CN113042000A - Chicken manure derived biochar loaded nano zero-valent iron composite material and preparation method and application thereof - Google Patents
Chicken manure derived biochar loaded nano zero-valent iron composite material and preparation method and application thereof Download PDFInfo
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- CN113042000A CN113042000A CN202110306419.XA CN202110306419A CN113042000A CN 113042000 A CN113042000 A CN 113042000A CN 202110306419 A CN202110306419 A CN 202110306419A CN 113042000 A CN113042000 A CN 113042000A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
- B01J20/28009—Magnetic properties
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2220/00—Aspects relating to sorbent materials
- B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
- B01J2220/48—Sorbents characterised by the starting material used for their preparation
- B01J2220/4875—Sorbents characterised by the starting material used for their preparation the starting material being a waste, residue or of undefined composition
- B01J2220/4887—Residues, wastes, e.g. garbage, municipal or industrial sludges, compost, animal manure; fly-ashes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
Abstract
The invention discloses a chicken manure derived biochar loaded nano zero-valent iron particle, a preparation method thereof and application of the particles in removing Cr (VI) in water. The novel composite material of the chicken manure derived biochar loaded with the nano zero-valent iron particles comprises chicken manure derived biochar (CMBC) and nano zero-valent iron particles (nZVI) loaded on the surface of the CMBC and in a pore channel of the CMBC. The invention adopts a liquid phase reduction method, takes CMBC as a carrier and FeSO4•7H2O is ferrous salt, NaBH4Is a reducing agent, is prepared under the protection of nitrogen, and the obtained material effectively inhibitsThe easy agglomeration of the nZVI greatly improves the reaction activity of the nZVI. The preparation and application of the composite material do not involve complex process flows, and the composite material has wide raw material sources and low cost and is beneficial to popularization and application.
Description
Technical Field
The invention belongs to the technical field of environment restoration materials, and particularly relates to a chicken manure derived biochar loaded nano zero-valent iron particle, a preparation method thereof and application thereof in removing Cr (VI) in water.
Background
With the development of human society, especially the industrialization of production activities, the environmental pollution caused by the chromium ions entering the water body due to improper production storage or disposal sometimes occurs. Chromium is a toxic heavy metal and has applications in electroplating, metallurgy, leather and chromate manufacturing industries, etc. In natural environment, chromium exists mainly in two forms of Cr (III) and Cr (VI), wherein Cr (III) is easy to exist in a stable complex form in natural water, and Cr (VI) has high toxicity, is soluble in water, is difficult to precipitate and is easy to migrate, and is often in an oxyanion form (CrO)4 2-、HCrO4-And Cr2O7 2-) Are present. Because of their carcinogenic, environmentally persistent and bioaccumulative properties, they pose a potential threat to human health if they eventually enter the human body via the food chain. Compared with Cr (VI), Cr (III) has less toxicity to the environment, and the conversion of Cr (VI) into Cr (III) ions is one of the effective ways for researchers to reduce the risk of chromium pollution. Therefore, it is necessary to remove Cr (VI) from water.
At present, various technologies have been applied to repair of cr (vi) -contaminated environments, including nanofiltration membrane methods, chemical precipitation methods, ion exchange methods, adsorption methods, reduction methods, electrodialysis methods, and photocatalytic methods. The nanometer zero-valent iron (nZVI) has strong reducibility, has quick response time effect on chromium-polluted water, good effect and wide applicability, can realize the restoration target in a short time, and becomes one of the focuses of the attention of researchers.
The nZVI refers to zero-valent iron particles with nano-scale particle sizes, has stronger reducibility and reactivity, and can reduce the toxicity of pollutants by adsorbing metal ions and carrying out redox reaction with the metal ions; however, unmodified nZVI is prone to agglomeration and oxidation, resulting in reduced reactivity, and thus modification of nZVI is highly desirable in order to improve its stability and activity. At present, the nZVI modification technology mainly comprises nanometer bimetal, surface coating, emulsification nZVI and solid load, wherein the solid load is widely concerned due to the variety of sources and the economy of load materials; the reaction activity of the nZVI is effectively improved by loading the nZVI in the bentonite; the biochar is also prepared from rice straws, and the nZVI is loaded on the biochar, so that Cr (VI) in water is effectively removed; and the waste dregs are used for preparing the biochar composite material containing the nZVI, so that the Cr (VI) in water can be efficiently removed. The current research shows that loading nZVI on a specific carrier is an effective method for improving the agglomeration resistance and the oxidation resistance of the carrier.
The nZVI is loaded on the charcoal, is a green and efficient environment-repairing material, and has a greater application value than single unmodified nZVI. According to the prior knowledge, no report related to the preparation of the chicken manure derived biochar loaded with the nano zero-valent iron (nZVI @ CMBC) exists. According to the preparation method, fermented chicken manure is prepared into chicken manure derived biochar (CMBC) through a high-temperature pyrolysis method, and nZVI is loaded on the surface of the CMBC and inside a pore passage of the CMBC, so that the novel nZVI @ CMBC composite material is successfully prepared, the problems that unmodified nZVI is easy to agglomerate and oxidize are effectively solved, and the nZVI is adsorbed on the material by utilizing the reduction, complexation, coprecipitation and ion exchange effects of the traditional biochar and nano zero-valent iron particles in combination with the respective advantages of the traditional biochar and the nano zero-valent iron particles, so that the Cr (VI) in water is efficiently removed in a short time, and the reducibility of the nZVI is furthest exerted. It is desirable to be able to achieve waste utilization while also improving the feasibility for the application of nZVI in the field of environmental remediation.
Disclosure of Invention
The invention aims to provide a chicken manure derived biochar loaded nano zero-valent iron composite material, a preparation method thereof and a method for removing Cr (VI) in water.
The invention provides a chicken manure derived biochar loaded nano zero-valent iron composite material, which comprises biochar (CMBC) prepared from chicken manure and nano zero-valent iron particles (nZVI) loaded on the surface and inner pore channels of the biochar.
Preferably, the chicken manure comprises fermented chicken manure.
Preferably, the nano zero-valent iron particles are fully loaded on the surface and in the inner pore canal of the CMBC to form the zero-valent iron coating layer.
Preferably, the particle size of the nanometer zero-valent iron particles is 20-100 nm.
The invention provides a preparation method of a chicken manure derived biochar loaded nano zero-valent iron composite material, which comprises the following steps:
a) under the protection of inert gas, carrying out high-temperature pyrolysis on the chicken manure in a tube furnace, cooling, removing impurities by using an acid solution, cleaning for several times, and drying to obtain chicken manure derived biochar particles;
b) uniformly mixing the chicken manure derived biochar and a ferrous salt solution in water to obtain a chicken manure derived biochar-ferrous salt mixed solution;
c) under the protection of inert gas, carrying out oxidation-reduction reaction on the mixed solution and a reducing agent to obtain a chicken manure derived biochar loaded nano zero-valent iron suspension;
d) and carrying out solid-liquid separation on the suspension, cleaning black solid particles, and drying to obtain the chicken manure derived biochar loaded nano zero-valent iron particles.
Preferably, in step a), the chicken manure comprises fermented chicken manure.
Preferably, in the step a), the particle size of the chicken manure derived biochar is 5-100 ㎛, and the pore diameter is 0.5-1.5 ㎛
Preferably, in the step a), the high-temperature pyrolysis temperature is 400-1000 ℃; the high-temperature pyrolysis time is 2-4 h.
Preferably, in step a), the acid solution comprises a hydrochloric acid solution; the concentration of the acid solution is 0.5-5.0 mol/L.
Preferably, in step a), the cleaning is performed several times by using deionized water.
Preferably, in the step a), the drying comprises forced air drying, and the drying time is 24-48 h.
Preferably, step a) specifically comprises:
after the chicken manure is naturally dried, grinding and sieving are carried out, sieved particles are subjected to high-temperature pyrolysis in a tube furnace, impurities are removed by using an acid solution after cooling, solid particles are cleaned after removal is finished, and the solid particles are dried until the pH value of filtrate is neutral to obtain the chicken manure derived biochar particles.
Preferably, in step b), the ferrous salt solution comprises a ferrous sulfate solution; the concentration of the ferrous sulfate solution is 0.045-0.09 mol/L.
Preferably, in the step b), the mass ratio of the iron element to the chicken manure-derived biochar in the mixed solution is 1: (0.2-5).
Preferably, step b) specifically comprises:
and after the ferrous salt is completely dissolved, adding the chicken manure derived biochar, and continuously stirring to fully mix the solution to obtain the chicken manure derived biochar-ferrous salt mixed solution.
Preferably, in step c), the inert gas comprises high purity nitrogen; and introducing inert gas for more than 30min before the oxidation-reduction reaction.
Preferably, in step c), the reducing agent comprises sodium borohydride solution; the concentration of the sodium borohydride solution is 0.53-1.06 mol/L.
Preferably, in the step c), the rotation speed of the stirring is preferably 300-600 rpm/min.
Preferably, in the step c), the temperature of the oxidation-reduction reaction is 10-35 ℃; the time of the oxidation-reduction reaction is 0.5-2 h.
Preferably, step c) specifically comprises:
and under the protection of inert gas, slowly dripping the reducing agent into the mixed solution in a dripping mode, continuously and quickly stirring, and continuously stirring after dripping is finished to obtain the chicken manure derived biochar loaded nano zero-valent iron suspension.
Preferably, in step d), the solid-liquid separation comprises the use of a magnetic separation method.
Preferably, in the step d), the cleaning is performed several times by using deoxidized deionized water and absolute ethyl alcohol sequentially.
Preferably, in the step d), the drying includes vacuum freeze-drying, and the time of the vacuum freeze-drying is preferably 12-48 hours.
Preferably, step d) specifically comprises:
and after solid-liquid separation of the suspension, sequentially using deoxidized deionized water and absolute ethyl alcohol to clean the black solid particles until the pH of the filtrate is neutral, and drying to obtain the chicken manure derived biochar loaded nano zero-valent iron particles.
The invention also provides a method for efficiently removing Cr (VI) in water, which comprises the following steps:
the chicken manure derived biochar loaded nano zero-valent iron composite material or the chicken manure derived biochar loaded nano zero-valent iron composite material obtained by the preparation method is added into an aqueous solution polluted by Cr (VI), and finally the Cr (VI) in the aqueous solution is efficiently removed by the chicken manure derived biochar loaded nano zero-valent iron composite material, and the composite material can also be separated and recovered from the aqueous solution through the magnetic action.
Compared with the prior art, the chicken manure derived biochar loaded nano zero-valent iron composite material provided by the invention combines the advantages of biochar and nZVI, the raw material of the biochar is chicken manure, belongs to waste in the livestock and poultry breeding industry, is wide in source and low in price, the nZVI is dispersed and loaded on the surface and in the pore channel of the chicken manure derived biochar, the problem of agglomeration of the nZVI is effectively solved, the reaction activity of the nZVI is obviously improved, Cr (VI) in water is efficiently removed, the composite material is environment-friendly, does not produce secondary pollution, and has magnetism under the condition of a magnetic field, so that the composite material is beneficial to separation and recovery after reaction, and has a very wide application prospect in the technical field of environment restoration materials.
Drawings
FIGS. 1a, 1b, 1c are SEM pictures of CMBC in example 1 of the present invention, nZVI in comparative example 1 and nZVI @1CMBC in example 1;
FIG. 2 is XRD patterns of nZVI, CMBC and nZVI @1CMBC before and after absorbing Cr (VI) according to comparative example 1 and example 1 of the present invention;
FIG. 3 is a hysteresis curve of nZVI @1CMBC in example 1 of the present invention;
FIG. 4 is a graph showing the effect of composite materials of different mass ratios of nZVI to CMBC on Cr (VI) removal obtained in example 1, comparative example 1 and example 2 according to the present invention;
FIG. 5 is a graph showing the effect of nZVI @1CMBC produced in example 1 of the present invention on the removal of Cr (VI) from water at different dosages and reaction times;
FIG. 6 is a graph showing the effect of nZVI @1CMBC produced in example 1 of the present invention on the removal of Cr (VI) from water at different initial pH values;
FIGS. 7a, 7b, 7C, 7d show XPS spectra (C1 s, O1s, Fe2p, and Cr2 p) of nZVI @1CMBC before and after absorption of Cr (VI) in accordance with example 1 of the present invention;
FIG. 8 is a Zeta potential diagram before and after absorption of Cr (VI) by nZVI, CMBC and nZVI @1CMBC according to comparative example 1 and example 1 of the present invention;
FIG. 9 is an FTIR spectrum of the present invention before and after absorption of Cr (VI) by nZVI, CMBC and nZVI @1CMBC in comparative example 1 and example 1.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be part of the invention and not all of it.
The invention provides a chicken manure derived biochar loaded nano zero-valent iron composite material which comprises biochar (CMBC) prepared from fermented chicken manure and nano zero-valent iron particles (nZVI) loaded on the surface and inner pore channels of the biochar.
In the composite material provided by the invention, the preferred particle size of the biochar is 5-100 ㎛, and the pore diameter is 0.5-1.5 ㎛; the particle size of the nano zero-valent iron is preferably 20-100 ㎚; the nano zero-valent iron particles are preferably fully loaded in the surface and the inner pore canal of the CMBC to form a zero-valent iron coating layer.
According to the invention, the chicken manure derived biochar is used as a carrier material of the nano zero-valent iron, has the properties of a biochar material, and can provide corresponding attachment points for the nano zero-valent iron, so that the agglomeration of the nano zero-valent iron loaded on the material is effectively inhibited; because of the large specific surface area, the metal ion adsorption material can adsorb precipitates generated after Cr (VI) in water is reduced by nZVI or Fe (II), thereby effectively reducing the metal ion content in the water solution and avoiding the possibility of secondary pollution. Compared with the traditional biochar, the chicken manure derived biochar loaded nano zero-valent iron composite material provided by the invention has certain magnetic capability, is beneficial to recovery and separation of materials in water, and fundamentally solves the risk of secondary pollution. Compared with the traditional nano zero-valent iron particles, the chicken manure derived biochar loaded nano zero-valent iron composite material provided by the invention effectively overcomes the easy agglomeration of nZVI, combines the advantages of biochar and nZVI, remarkably improves the reaction activity of nZVI, realizes the efficient removal of Cr (VI) in water, and has a very wide application prospect in the technical field of environment restoration materials.
The invention also provides a preparation method of the chicken manure derived biochar loaded nano zero-valent iron composite material, which comprises the following steps:
a) under the protection of inert gas, carrying out high-temperature pyrolysis on the chicken manure in a tube furnace, cooling, removing impurities by using an acid solution, cleaning for several times, and drying to obtain chicken manure derived biochar particles;
b) uniformly mixing the chicken manure derived biochar and a ferrous salt solution in water to obtain a chicken manure derived biochar-ferrous salt mixed solution;
c) under the protection of inert gas, carrying out oxidation-reduction reaction on the mixed solution and a reducing agent to obtain a chicken manure derived biochar loaded nano zero-valent iron suspension;
d) and carrying out solid-liquid separation on the suspension, cleaning black solid particles, and drying to obtain the chicken manure derived biochar loaded nano zero-valent iron particles.
In the preparation method provided by the invention, the chicken manure derived biochar is prepared by firstly carbonizing chicken manure, wherein the particle size of the chicken manure derived biochar is preferably 5-100 ㎛; after the chicken manure is carbonized, preferably carrying out acid modification to remove impurities; the specific steps of the carbonization and acid modification treatment preferably comprise:
naturally drying the chicken manure, grinding and sieving; then placing the sieved chicken manure into a tubular furnace, and carrying out high-temperature pyrolysis under the protection of inert gas to obtain carbonized black solid particles; and (3) soaking the black solid particles in an acid solution after cooling, and finally cleaning and drying the black solid particles to obtain the acid-modified chicken manure derived biochar particles.
In the carbonization and acid modification treatment steps provided by the invention, the chicken manure is preferably fermented chicken manure and is sieved by a 100-mesh sieve; the inert gas is preferably filled with high-purity nitrogen; the high-temperature pyrolysis temperature is preferably 400-1000 ℃, and specifically can be 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃ or 1000 ℃; the high-temperature pyrolysis time is 2-4 h, specifically 2h, 3h and 4 h; the acid solution is preferably hydrochloric acid solution; the concentration of the acid solution is 0.5-5.0 mol/L, and specifically can be 0.5mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L, 3.0mol/L, 3.5mol/L, 4.0mol/L, 4.5mol/L or 5.0 mol/L; washing for several times by using deionized water until the pH value of the filtrate is neutral; the drying mode is selected from air blast drying, and the drying time is preferably 24-48 h, and specifically can be 24h, 30h, 36h, 42h or 48 h.
In the preparation method provided by the invention, the preparation steps of the chicken manure derived biochar-ferrous salt mixed solution preferably comprise:
firstly, completely dissolving ferrous salt in deionized water, then adding the prepared chicken manure derived biochar, and continuously stirring to fully mix the solution.
In the preparation step of the mixed solution provided by the invention, the ferrous salt solution comprises a ferrous sulfate solution; the concentration of the ferrous sulfate solution is 0.036-0.09 mol/L, and specifically can be 0.036mol/L, 0.054mol/L, 0.072mol/L or 0.09 mol/L; the mass ratio of the iron element to the chicken manure derived biochar in the mixed solution is 1 (0-5), and specifically can be 1:0, 1:0.2, 1:0.5, 1:1, 1:2 or 1: 5.
In the preparation method provided by the invention, the preparation of the chicken manure derived biochar loaded nano zero-valent iron suspension is carried out by carrying out redox reaction on the mixed solution and a reducing agent under the protection of inert gas, and the preferable steps comprise:
and under the protection of inert gas, slowly dripping the reducing agent into the mixed solution in a dripping mode, continuously and quickly stirring, and continuously stirring after dripping is finished to obtain the chicken manure derived biochar loaded nano zero-valent iron suspension.
In the above suspension preparation step provided by the present invention, the inert gas is preferably high-purity nitrogen; introducing inert gas for more than 30min before the oxidation-reduction reaction; the reducing agent is preferably sodium borohydride solution; the concentration of the sodium borohydride solution is 0.42-1.06 mol/L, and specifically can be 0.42mol/L, 0.63mol/L, 0.85mol/L or 1.06 mol/L; the rotation speed of the stirring is preferably 300-600 rpm/min, and specifically can be 300rpm/min, 400rpm/min, 500rpm/min or 600 rpm/min; the temperature of the oxidation-reduction reaction is 10-35 ℃, and specifically can be 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃ or 35 ℃; the time of the oxidation-reduction reaction is 0.5-2 h, and specifically can be 0.5h, 1h, 1.5h or 2 h.
In the preparation method provided by the invention, the preparation of the chicken manure derived biochar loaded nano zero-valent iron particles comprises the following steps of carrying out solid-liquid separation on the suspension, cleaning black solid particles and drying, wherein the preferable steps comprise:
and (3) after solid-liquid separation of the suspension, sequentially cleaning black solid particles by using deoxidized deionized water and absolute ethyl alcohol until the pH value of the filtrate is neutral, and drying to obtain the chicken manure derived biochar loaded nano zero-valent iron particles.
In the preparation step of the chicken manure derived biochar loaded nano zero-valent iron particles, a magnetic separation method is preferably selected for solid-liquid separation; the cleaning is carried out for several times by using deoxidized deionized water and absolute ethyl alcohol; the drying is preferably vacuum freeze drying, and the vacuum freeze drying time is preferably 12-48 h, and specifically can be 12h, 18h, 24h, 30h, 36h, 42h or 48 h.
According to the preparation method provided by the invention, a corresponding reducing agent is dripped into the chicken manure derived biochar-ferrous salt mixed solution through a liquid phase reduction method, so that nano zero-valent iron particles are reduced on the surface and in pore channels of the chicken manure derived biochar, and thus the chicken manure derived biochar loaded nano zero-valent iron composite material is obtained. The preparation method combines the chicken manure derived biochar and the nano zero-valent iron together, so that the composite material generates a synergistic effect, realizes the efficient removal of Cr (VI) in water by utilizing the advantages of the biochar and the nano zero-valent iron, and has a very wide application prospect in the technical field of environment restoration materials. Specifically, the preparation method provided by the invention has the following advantages:
1) the chicken manure derived biochar is used as a carrier material of the nano zero-valent iron, has the properties of a biochar material, and can provide corresponding attachment points for the nano zero-valent iron, so that the agglomeration of the nano zero-valent iron loaded on the material is effectively inhibited; because of the large specific surface area, the metal ion adsorption material can adsorb precipitates generated after Cr (VI) in water is reduced by nZVI or Fe (II), thereby effectively reducing the metal ion content in the water solution and avoiding the possibility of secondary pollution.
2) Compared with the traditional biochar, the chicken manure derived biochar loaded nano zero-valent iron composite material provided by the invention has certain magnetic capability, is beneficial to recovery and separation of materials in water, and fundamentally solves the risk of secondary pollution.
3) Compared with the traditional nano zero-valent iron particles, the charcoal-loaded nano zero-valent iron composite material derived from chicken manure effectively overcomes the easy agglomeration of nZVI, so that the nZVI is more dispersed, the particle size is smaller, the adsorption capacity is stronger, and the removal capacity of the nZVI on Cr (VI) in water is greatly improved.
4) The raw materials have wide sources, belong to the field of waste utilization, have low cost, and have safe preparation process and no complex process requirements.
5) Combines the advantages of the biochar and the nZVI, remarkably improves the reaction activity of the nZVI, and realizes the high-efficiency removal of the Cr (VI) in the water.
The invention also provides a method for efficiently removing Cr (VI) in water, which comprises the following steps:
the chicken manure derived biochar loaded nano zero-valent iron composite material or the chicken manure derived biochar loaded nano zero-valent iron composite material obtained by the preparation method is added into an aqueous solution polluted by Cr (VI), so that the Cr (VI) in the aqueous solution is efficiently removed by the chicken manure derived biochar loaded nano zero-valent iron composite material.
According to the method for efficiently removing the Cr (VI) in the water, the composite material is directly added into the water containing the Cr (VI), the composite material has the effects of reduction, complexation, coprecipitation, ion exchange and the like on the Cr (VI) in the water, and is finally adsorbed or precipitated on the composite material in the form of precipitates, and the composite material is separated from the water body after the reaction is finished, so that the efficient removal of the Cr (VI) in the water is realized. The method has the advantages of high reaction speed, environmental friendliness, effective reduction of harm of Cr (VI) to the environment and human body by 'treating waste by waste', and very wide application prospect in the technical field of environment restoration materials.
For a clearer description, the following examples are given in detail below.
Example 1
A chicken manure derived biochar loaded nano zero-valent iron composite material takes chicken manure derived biochar (CMBC) as a carrier, and nano zero-valent iron particles are loaded in the surface and inner pore channels of the CMBC, and the preparation process comprises the following steps:
(1) preparation of chicken manure derived biochar (CMBC)
Naturally airing the fermented chicken manure, grinding and sieving the chicken manure (100 meshes), weighing a certain amount of the sieved chicken manure, placing the chicken manure in a tube furnace, introducing nitrogen for 30min, heating the chicken manure to 600 ℃ at the speed of 10 ℃/min and keeping the temperature for 2h (nitrogen protection in the whole pyrolysis process) to obtain carbonized black solid particles, cooling the black solid particles to the normal temperature, soaking the black solid particles in 0.5mol/L HCl solution for 24h (the ratio of the solid particles to the HCl solution is 1g:100ml), finally washing the solid particles with deionized water until the pH of filtrate is neutral, and placing the washed chicken manure-derived biochar solid particles in a forced air drying oven for drying for 24h for later use.
(2) Preparation of chicken manure derived biochar-ferrous salt mixed solution
Adding 0.5g chicken manure derived biochar into 100ml 0.09mol/L FeSO4•7H2In solution of O, inContinuously oscillating at the rotating speed of 300rpm/min for 12h to fully mix the solution, wherein the mass ratio of the iron element in the obtained mixed solution to the chicken manure derived biochar is 1: 1.
(3) Preparation of chicken manure derived biochar loaded nano zero-valent iron suspension
Introducing nitrogen into the mixed solution for 30min, and then dropwise adding 25ml of 1.06mol/L NaBH at the dropping speed of 2-3 ml/min4Solution (NaBH to ensure sufficient reduction of iron in solution4Solution with FeSO4•7H2The concentration ratio of the O solution is about 3: 1), and after the dropwise addition is finished, the stirring is continuously carried out for 1h at the rotating speed of 600rpm/min, and the reaction temperature is 25 ℃ (the whole oxidation-reduction reaction is protected by nitrogen).
(4) Preparation of chicken manure derived biochar loaded nano zero-valent iron particles
And (2) carrying out solid-liquid separation on the obtained suspension by using a magnetic separation method, cleaning the obtained solid particles by using deionized water (introducing nitrogen for 30min before the deionized water is used) until the pH of the filtrate is neutral, cleaning for 3 times by using absolute ethyl alcohol, and placing the filtrate in vacuum freeze drying for 24 hours to obtain the solid particles, namely the chicken manure derived biochar loaded nano zero-valent iron particles, wherein the mass ratio of the iron element in the solid particles to the chicken manure derived biochar is 1:1 and is marked as nZVI @1 CMBC.
Comparative example 1
The preparation process of nanometer zero-valent iron particle includes the following steps:
(1) preparation of nano zero-valent iron suspension
To 100ml of 0.09mol/L FeSO4•7H2Introducing nitrogen into the O solution for 30min, and then dropwise adding 25ml of 1.06mol/L NaBH at the dropping speed of 2-3 ml/min4Solution (NaBH to ensure sufficient reduction of iron in solution4Solution with FeSO4•7H2The concentration ratio of the O solution is about 3: 1), and after the dropwise addition is finished, the stirring is continuously carried out for 1h at the rotating speed of 600rpm/min, and the reaction temperature is 25 ℃ (the whole oxidation-reduction reaction is protected by nitrogen).
(2) Preparation of nano zero-valent iron particles
And (3) carrying out solid-liquid separation on the suspension obtained by the magnetic separation method, washing the obtained solid particles by deionized water (introducing nitrogen for 30min before the deionized water is used) until the pH of the filtrate is neutral, washing the filtrate for 3 times by using absolute ethyl alcohol, and placing the filtrate in vacuum freeze drying for 24 hours to obtain the solid particles, namely the nano zero-valent iron particles, which are recorded as nZVI.
Product characterization
FIG. 1a is an SEM image of chicken manure-derived biochar (CMBC) having a rough surface, irregular shape, large variation in particle size, pore size of about 0.5-1.5 ㎛, and particle size distribution of 5-100 ㎛. Fig. 1b shows the surface morphology of the nano zero-valent iron (nZVI), and the picture shows that a large number of chain-shaped spherical particles are serious in agglomeration property, and the particle size is mainly distributed between 20 and 100 ㎚, which is a typical morphology feature of the nano zero-valent iron. From fig. 1c, it is clear that the chicken manure derived biochar surface becomes rougher and is dispersed with a large amount of chain-like fine particles, and in the absence of a magnetic field, the synthetic material is nonmagnetic, which indicates that nZVI is successfully loaded on CMBC, and the agglomeration of the nZVI is effectively inhibited.
FIG. 2 is an XRD pattern of different materials with more CMBC diffraction peaks including C, CaCO3And SiO2. Wherein 2 theta of 20.85 degrees, 26.62 degrees, 36.53 degrees, 45.77 degrees, 50.11 degrees, 63.99 degrees, 67.70 degrees, 68.27 degrees, 75.61 degrees and 77.62 degrees belong to SiO respectively2 100. Characteristic peaks of the crystal planes 011, 110, 201, 112, 113, 122, 031, 302 and 220 (PDF 70-3755); and characteristic peaks of C006, 0012, 108 and 109 crystal planes (PDF 26-1076) at 26.60 degrees, 54.79 degrees, 56.67 degrees and 60.02 degrees, and CaCO at 35.45 degrees and 39.49 degrees3Characteristic peaks of the 131 and 302 crystal planes (PDF 17-0763). The characteristic peak of the 110 crystal face (PDF 03-1050) of the zero-valent iron appears at 44.83 degrees, which is a typical characteristic peak of the zero-valent iron, and no obvious characteristic peak related to the iron oxide appears, which indicates that the nitrogen protection is better in the preparation process of the zero-valent iron, and the oxidation phenomenon of the zero-valent iron does not appear. The characteristic peak of zero-valent iron appears in the spectrum of nZVI @1CMBC, and the strength of the characteristic peak is almost unchanged compared with that of nZVI, which shows that the nano zero-valent iron is successfully loaded on the chicken manure derived biochar.
The hysteresis curve (fig. 3) indicates that nZVI @1CMBC is ferromagnetic, which indicates that the material can be conveniently recycled using magnetism. The magnetism is positively correlated. Wherein the saturation magnetization (Ms) of nZVI @1CMBC is 22.1emu/g, and no hysteresis loop phenomenon exists, which indicates that nZVI @1CMBC is a superparamagnetic material. Generally (without a magnetic field), nZVI @1CMBC is non-magnetic, indicating that it does not readily agglomerate in the environment.
Example 2
The specific steps are as described in example 1, except that the amounts of the biochar derived from chicken manure in the step (2) are 0.1g, 0.25g, 1g and 2.5g, respectively, in the preparation of the mixed solution of biochar derived from chicken manure and ferrous salt, i.e., the mass ratios of nZVI to CMBC in the mixed solution are 1:0.2, 1:0.5, 1:2 and 1:5, respectively. The obtained charcoal-loaded nano zero-valent iron particles derived from chicken manure are respectively marked as nZVI @0.2CMBC, nZVI @0.5CMBC, nZVI @2CMBC and nZVI @5 CMBC.
Example 3
Examining the influence of different mass ratios of nZVI and CMBC on the Cr (VI) removal effect, removing Cr (VI) in water by using chicken manure derived biochar loaded nano zero-valent iron particles (obtained from example 1, comparative example 1 and example 2) with the same Fe equivalent, setting 3 parallel samples in each group of experiments and using the samples as error bars, and specifically comprising the following steps:
0.02g of Fe equivalent of the chicken manure-derived biochar-supported nano zero-valent iron particles were weighed respectively, added to a series of 50ml of aqueous solutions with an initial pH of 4.03 and a Cr (VI) concentration of 50mg/L so that the concentrations of the chicken manure-derived biochar-supported nano zero-valent iron particles in the reaction system were 0.02g (nZVI in comparative example 1), 0.024g (nZVI @0.2CMBC in example 2), 0.03g (nZVI @0.5CMBC in example 2), 0.04g (nZVI @1CMBC in example 1), 0.06g (nZVI 2CMBC in example 2) and 0.12g (nZVI @5 BC in example 2), 0.02g of the CMBC of step (2) described in example 1 and a commercially available iron powder were weighed respectively, and after shaking for 24 hours under reduced pressure at normal temperature (25 ℃ C), the absorbance of the solution was measured as a cross-coordinate by using a diphenylcarbohydrazide method (Cr @ optical spectrophotometry), with Cr (VI) removal capacity qe(mg/g) is the left ordinate to correspond to the specific surface area (m) of the material2The/g) is the right ordinate. The results are shown in FIG. 4.
The experimental result shows that the chicken manure derived biochar with different mass ratios loads the nano zero-valent iron particlesThe removal amount of Cr (VI) is 73.47-81.58 mg/g, which is 21.8-24.1 times of that of CMBC (3.38mg/g), and 4.8-5.3 times of that of iron powder (15.27 mg/g). The removal capacity of the iron powder is far lower than that of nZVI (76.92mg/g), and the freshly prepared nano zero-valent iron has lower passivation degree by oxygen and obviously stronger reducibility compared with the iron powder, so that the nZVI has better effect of removing Cr (VI). When the ratio of nZVI to CMBC is 1:1 and 1:2, the removal amount of Cr (VI) is obviously increased compared with that of nZVI, because the addition of CMBC disperses the nZVI on the surface and among pores of the CMBC, the agglomeration of the nZVI is effectively prevented to a certain extent, so that the nano nZVI particles are more stable, more effective active adsorption sites are provided, and the reaction activity of the material is fully released. From the removal effect, when the ratio x of nZVI to CMBC is 5, 0.5 and 0.2, the removal capacity of nZVI @ xCBC to Cr (VI) is lower than that of nZVI, which indicates that the removal effect of nZVI @ xCBC on Cr (VI) is reduced to a certain extent by preparing an inappropriate mass ratio. In the research, the composite material with the mass ratio of nZVI to CMBC of 1:1 has the best effect of removing Cr (VI) in the aqueous solution, so that the composite material with the ratio is selected in other subsequent experiments. In addition, according to the following table 1, the specific surface area, pore volume and pore diameter of the chicken manure-derived biochar-supported nano zero-valent iron particles were compared, and the specific surface area of the CMBC was increased along with the increase of the ratio of the CMBC, wherein the specific surface area of the CMBC was 60.36m2(iv)/g is nZVI @1CMBC (21.25-45.85 m)21.3-2.8 times of/g), and the adsorption effect of nZVI @ CMBC has no obvious correlation with the increase of the content of CMBC; the pore volume of the composite material is smaller than the value of CMBC and irregularly changes; the pore sizes of the nZVI @0.2CMBC and the nZVI are almost the same, and the rest is less than 9.31 nm; the results of FIG. 4 show that the specific surface area, pore volume and pore diameter of the composite material are not the main factors influencing the adsorption and removal of Cr (VI).
TABLE 1 specific surface area, pore volume and pore diameter of the materials
Example 4
The influence of the addition amount and the reaction time on the Cr (VI) removal effect is examined by using the nZVI @1CMBC obtained in the example 1, 3 parallel samples are set in each group of experiments and used as error bars, and the specific steps are as follows:
0.005g, 0.01g, 0.02g, 0.03g, 0.04g, 0.05g and 0.1g of nZVI @1CMBC with Fe equivalent weight are respectively weighed and added into a series of 50ml of Cr (VI) aqueous solution with concentration of 50mg/L, and sampling is carried out to determine the Cr (VI) concentration when the reaction time is 5min, 10min, 20min, 0.5h, 1h, 3h, 6h, 12h, 24h, 48h and 72h, and the result is shown in figure 5.
The experimental results show that when the amount of nZVI @1CMBC was increased from 0.005g to 0.05g, the removal of Cr (VI) from the aqueous solution increased from 16.65% to 98.92% when the reaction time was 180 min. When the amount was increased to 0.1g, the removal rate did not increase significantly, but the reaction appeared to be faster. When the time is 10min, the removal rate reaches 98.13 percent until the reaction time is 180min and reaches 99.08 percent. When the amount is 0.1g, the Cr (VI) removal rate is only 0.16% higher than that of 0.05g, indicating that the composite material is used in an amount of 0.05g, the reaction sites of Cr (VI) in the aqueous solution are saturated, and the optimum amount of nZVI @1CMBC required for removing the Cr (VI) aqueous solution is 0.05 g. As can be seen from FIG. 5, the reaction eventually reached equilibrium when the reaction time was extended to 72 h. From the curves of 7 different doses it can be seen that the 180min adsorption capacity substantially exceeds 60% of the equilibrium adsorption capacity.
Example 5
The influence of the initial pH value on the Cr (VI) removal effect is investigated by using the nZVI @1CMBC obtained in example 1, 3 parallel samples are set in each group of experiments and used as error bars, and the specific steps are as follows:
the pH (2-10) of the solution was adjusted by using 0.5mol/L HCl and NaOH, 0.02g of nZVI @1CMBC equivalent to Fe was added to 50ml of Cr (VI), and after 24 hours of reaction, a sample was taken to determine Cr (VI) in the solution, and the results are shown in FIG. 6.
Experimental results show that the removal amount qe (mg/g) of the nZVI @1CMBC on the Cr (VI) is reduced from 124.12 mg/g to 30.71mg/g along with the increase of the pH value from 2.24 to 10.33, and the removal amount of the Cr (VI) is reduced by 75.26%, which indicates that the Cr (VI) in the solution is more favorably removed under acidic conditions, and the removal effect of the Cr (VI) is inhibited by alkalinity. As can be seen from the pH values after the end of the reaction in FIG. 7, when the initial pH of the reaction solution is less than or equal to 8.17, the final pH of the solution after the end of the reaction tends to be neutral, indicating that the removal of Cr (VI) in water by using nZVI @1CMBC contributes to the neutralization of the pH of the solution within a certain range of the initial pH.
Test examples
And (3) analyzing the changes of XRD and XPS spectrums before and after the composite material nZVI @1CMBC absorbs Cr (VI).
As shown in figure 2, after the chicken manure derived biochar loaded nano zero-valent iron composite material reacts with Cr (VI) in water, the peak intensity of zero-valent iron at 44.83 degrees is obviously weakened, and iron/chromium oxides appear near 35 degrees (35.51 degrees and 35.68 degrees) of 2 theta, wherein 35.68 degrees are Fe2O3 Characteristic peak of 119 plane (PDF 25-1402); and 35.51 DEG is FeCr2O4/Cr2FeO4The characteristic peak of the 311 crystal face (PDF 34-0140) shows that an effective redox reaction is carried out between the two to generate iron-chromium oxide, so that Cr (VI) is reduced to Cr (III) and then is adsorbed and precipitated on nZVI @1 CMBC.
As shown in fig. 7a, nZVI @1CMBC showed 4 peaks at 284.83, 286.23, 287.02 and 288.34eV, respectively, in the C1s spectrum, representing C-C, C-O, C = O and O-C = O, respectively. When nZVI @1CMBC was reacted with Cr (vi), the peaks of C-C, C-O, C = O and O-C = O shifted to 284.85, 288.65, 287.17 and 286.23eV, respectively, and the respective percentages were also changed from 77.32, 8.62, 1.86 and 12.2% to 69.41, 13.4, 1.69 and 15.5%, which indicates that surface complexation plays an important role in Cr (vi) removal.
The binding energy of O1s in fig. 7b at 529.96, 531.6 and 532.87eV corresponds to-OH, C-O and C = O, respectively, with percentages of 33.46, 50.69 and 15.85%, respectively. When nZVI @1CMBC is reacted with Cr (VI), the binding energies of C-O and C = O are shifted to 531.22eV and 531.81eV, respectively, and Cr appears at the position of 531.65eV2O3Characteristic peak of (2). When nZVI @ CMBC was reacted with Cr (vi), the percentage of-OH and C-O decreased, with the percentage of C = O suddenly increased from 15.85% to 46.82%. These changes illustrate that the reaction of Cr (VI) with nZVI @1CMBC reduces Cr (VI) to Cr (III) and further indicates complexation between contaminants and the surface functional groups of the composite.
In FIG. 7cFive characteristic peaks appear in the spectrum of Fe2p, namely Fe of 707.30eV0710.77eV FeO, 713.45 and 719.17eV Fe (III) and 724.36eV FeOOH. Wherein, Fe0The relatively low percentage of (A) may be due to the fact that the XPS instrument can only detect elements on the surface of the material, which is mostly Fe0Has been passivated by oxygen, but combined with the above XRD results, a large amount of nZVI exists in the whole system of the composite material, and most of nZVI is wrapped and dispersed in CMBC, so XPS can only detect surface Fe0A lesser amount. When nZVI @1CMBC reacts with Cr (VI), Fe0The characteristic peak of the alloy disappears (the intensity of the characteristic peak is obviously reduced and is consistent with that of the characteristic peak at 44.83 degrees of Cr (VI) -nZVI @1CMBC in the XRD compared with that of nZVI @1CMBC), the peak values of FeO, Fe (III) and FeOOH are slightly shifted, the percentage of FeO in the material is reduced, and the percentage of Fe (III) and FeOOH is obviously increased. This indicates that Fe0And Fe (II) is oxidized by Cr (VI) during the reaction.
After reaction of nZVI @1CMBC with Cr (vi) (fig. 7d) two main peaks 577.41 and 587.25eV appear in the Cr2p spectrum, five peaks after peak fitting are 580.25 and 582.04eV for Cr (vi), 576.57, 577.81 and 587.22eV for Cr (iii), respectively. Wherein 580.25eV is K2Cr2O7576.5eV is Cr2O3/Cr(OH)3And 577.81eV is FeCr2O4(with the above XRD analysis results in FeCr2O4The appearance of characteristic peaks is consistent). Cr (chromium) component2O3/Cr(OH)3And FeCr2O4The occurrence of (A) further demonstrates that Cr (VI) undergoes a redox reaction with nZVI @1CMBC, and K2Cr2O7The existence of the Cr (VI) also indicates that the Cr (VI) is not completely reduced into Cr (III), but part of the Cr (VI) is fixed on the surface of the composite material in an adsorption mode, so that the Cr (VI) is removed in an aqueous solution. In conclusion, the oxygen-containing functional group on the composite material nZVI @1CMBC plays a crucial role in removing Cr (VI) in a solution.
The main Cr (VI) removing reaction mechanism
According to XRD and XPS characterization analysis before and after the reaction of nZVI @ CMBC and Cr (VI), BET, Zeta potential and pH analysis, and combined with the removal effect of Cr (VI) in water, the nZVI @ CMBC has the following potential reaction mechanism for removing Cr (VI) in water: (1) the pores of the nZVI @ CMBC and the oxygen-containing functional groups on the surface of the nZVI @ CMBC (such as C-O, C = O, -OH and O-C = O) generate a certain adsorption effect on part of Cr (VI) in the solution with the help of surface tension; (2) the electrostatic adsorption can promote the removal of Cr (VI); (3) under the acidic condition, part of zero-valent iron and Cr (VI) can obtain Fe (II) and Cr (III) (equations (1) and (2)) through oxidation reduction; (4) transferring electrons to partial Cr (VI) in the solution by using zero-valent iron or Fe (II), and converting the obtained electrons into Cr (III) (equations (3) and (4)); (5) forming Fe (III) -Cr (III) coprecipitation (equation (5)) by means of ion exchange; (6) the reaction produced Cr2O3 and FeCr2O4 precipitates (equations (6) and (7)).
The Zeta potentials of nZVI, CMBC, nZVI @1CMBC and Cr-nZVI @1CMBC after reaction under different pH conditions are shown in FIG. 8. The surface charge of nZVI @1CMBC is negative when the pH of the dispersant is in the range of 2.02-8.01, approaches zero value when the pH is =2.02, and the charge quantity is increased when the pH is reduced. The zero potential of CMBC appears between 4.08 and 5.07, and the zero potential of nZVI appears between 5.07 and 7.01. The surface charge of the post-reaction Cr-nZVI @ CMBC is slightly increased overall compared to that of the pre-reaction nZVI @1CMBC, which is related to the formation of Cr (III) on its surface. Therefore, when the reaction solution pH is less than 2.02, nZVI @1CMBC can promote the removal of Cr (VI) by electrostatic adsorption.
The FTIR spectroscopy result is shown in FIG. 9, the biochar main band prepared at 600 ℃ is 1000--1In the range, it was shown that a large number of hydroxyl (-OH) and carboxylic acid (-COOH) groups were present on CMBC. The carboxylic acid groups may form complexes with metal ions. For nZVI @1CMBC and Cr (VI) -nZVI @1CMBC at 556cm-1An absorption band reflecting the vibrational characteristics of Fe-O bonds is observed nearby, and the absorption band is mainly the tensile vibration of Fe-O. 1320cm-1The peak at (a) is associated with the O-C = O group, and 1060cm-1Frequency band and C-O bending oscillationIt is related. A typical peak is about 1590cm-1Mainly related to C = stretching oscillations and-OH stretching oscillations of esters. The results show that the length of the groove is 980cm-1The left and right base bands belong to the Cr-O group, indicating that Cr (VI) -nZVI @1CMBC adsorbs Cr on the surface.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (8)
1. The chicken manure derived biochar loaded nano zero-valent iron composite material is characterized by comprising derived biochar prepared by taking chicken manure as a raw material and nano zero-valent iron particles loaded on the surface and inner pore channels of the chicken manure derived biochar.
2. The chicken manure derived biochar-loaded nano zero-valent iron composite material as claimed in claim 1, wherein the chicken manure is fermented chicken manure.
3. The chicken manure derived biochar-loaded nano zero-valent iron composite material as claimed in claim 1, wherein the particle size of the chicken manure derived biochar is 5-100 ㎛, the pore diameter is 0.5-1.5 ㎛, and the particle size of the nano zero-valent iron particles is 20-100 ㎚.
4. A method for preparing the chicken manure derived biochar loaded nano zero-valent iron composite material as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:
a) under the protection of inert gas, carrying out high-temperature pyrolysis on the chicken manure in a tube furnace, cooling, removing impurities by using an acid solution, cleaning, and drying to obtain chicken manure derived biochar particles;
b) uniformly mixing the chicken manure derived biochar and a ferrous salt solution in water to obtain a chicken manure derived biochar-ferrous salt mixed solution;
c) under the protection of inert gas, carrying out oxidation-reduction reaction on the mixed solution obtained in the step b) and a reducing agent to obtain a chicken manure derived biochar loaded nano zero-valent iron suspension;
d) and d), carrying out solid-liquid separation on the suspension obtained in the step c), cleaning black solid particles, and drying to obtain the chicken manure derived biochar loaded nano zero-valent iron composite material.
5. The method as claimed in claim 4, wherein the chicken manure in step a) is fermented chicken manure; grinding the chicken manure and sieving the ground chicken manure with a 100-mesh sieve; the temperature of the high-temperature pyrolysis is 400-1000 ℃; the high-temperature pyrolysis time is 2-4 h; the acid solution is hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 0.5-5.0 mol/L.
6. The preparation method according to claim 4, wherein in the step b), the ferrous salt solution is a ferrous sulfate solution with a concentration of 0.045-0.09 mol/L; the mass ratio of the iron element in the mixed solution to the chicken manure derived biochar is 1: (0.2-5).
7. The method according to claim 4, wherein in the step c), the inert gas comprises high-purity nitrogen; introducing inert gas for more than 30min before the oxidation-reduction reaction; the reducing agent comprises a sodium borohydride solution; the concentration of the sodium borohydride solution is 0.53-1.06 mol/L; the temperature of the oxidation-reduction reaction is 10-35 ℃; the time of the oxidation-reduction reaction is 0.5-2 h.
8. The application of the chicken manure derived biochar loaded nano zero-valent iron composite material as claimed in claim 1, wherein the chicken manure derived biochar loaded nano zero-valent iron composite material is used for efficiently removing Cr (VI) in water.
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