CN116573643A - Mixed melting activation type preparation method of sludge biochar - Google Patents
Mixed melting activation type preparation method of sludge biochar Download PDFInfo
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- CN116573643A CN116573643A CN202310458485.8A CN202310458485A CN116573643A CN 116573643 A CN116573643 A CN 116573643A CN 202310458485 A CN202310458485 A CN 202310458485A CN 116573643 A CN116573643 A CN 116573643A
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- 239000010802 sludge Substances 0.000 title claims abstract description 110
- 238000002844 melting Methods 0.000 title claims abstract description 26
- 230000008018 melting Effects 0.000 title claims abstract description 24
- 230000004913 activation Effects 0.000 title claims abstract description 19
- 238000002360 preparation method Methods 0.000 title description 4
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 36
- 238000000197 pyrolysis Methods 0.000 claims abstract description 30
- 239000011592 zinc chloride Substances 0.000 claims abstract description 27
- 235000005074 zinc chloride Nutrition 0.000 claims abstract description 27
- 238000002156 mixing Methods 0.000 claims abstract description 25
- 238000001035 drying Methods 0.000 claims abstract description 16
- 238000007873 sieving Methods 0.000 claims abstract description 16
- 238000000227 grinding Methods 0.000 claims abstract description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 230000003213 activating effect Effects 0.000 claims abstract description 13
- 238000003756 stirring Methods 0.000 claims abstract description 13
- 238000005406 washing Methods 0.000 claims abstract description 11
- 239000008367 deionised water Substances 0.000 claims abstract description 10
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 10
- 238000005554 pickling Methods 0.000 claims abstract description 10
- 230000007935 neutral effect Effects 0.000 claims abstract description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 26
- 229910052757 nitrogen Inorganic materials 0.000 claims description 13
- 239000011261 inert gas Substances 0.000 claims description 12
- 229910052573 porcelain Inorganic materials 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 10
- 238000000855 fermentation Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000009423 ventilation Methods 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000001914 filtration Methods 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 125000000524 functional group Chemical group 0.000 abstract description 6
- 238000001179 sorption measurement Methods 0.000 description 35
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 239000002994 raw material Substances 0.000 description 9
- CZGCEKJOLUNIFY-UHFFFAOYSA-N 4-Chloronitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C=C1 CZGCEKJOLUNIFY-UHFFFAOYSA-N 0.000 description 8
- 239000004695 Polyether sulfone Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 229920006393 polyether sulfone Polymers 0.000 description 8
- 239000011148 porous material Substances 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910019142 PO4 Inorganic materials 0.000 description 6
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 6
- 239000010452 phosphate Substances 0.000 description 6
- 238000005070 sampling Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 239000012528 membrane Substances 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000003463 adsorbent Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000003610 charcoal Substances 0.000 description 3
- 239000003344 environmental pollutant Substances 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000002957 persistent organic pollutant Substances 0.000 description 3
- 231100000719 pollutant Toxicity 0.000 description 3
- 239000010865 sewage Substances 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 238000002336 sorption--desorption measurement Methods 0.000 description 3
- 239000003242 anti bacterial agent Substances 0.000 description 2
- 229940088710 antibiotic agent Drugs 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 2
- 235000019796 monopotassium phosphate Nutrition 0.000 description 2
- 244000052769 pathogen Species 0.000 description 2
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BFCFYVKQTRLZHA-UHFFFAOYSA-N 1-chloro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1Cl BFCFYVKQTRLZHA-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007630 basic procedure Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004151 fermentation Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/342—Preparation characterised by non-gaseous activating agents
- C01B32/348—Metallic compounds
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/318—Preparation characterised by the starting materials
- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/40—Valorisation of by-products of wastewater, sewage or sludge processing
Abstract
The invention discloses a method for preparing sludge biochar by mixing and melting activation, which comprises the following steps: step 1: the sludge is screened and then concentrated to obtain concentrated sludge; step 2: mixing the concentrated sludge and zinc chloride according to the mixing mass ratio of 0.5:1-5:1 of the zinc chloride to the concentrated sludge to obtain mixed sludge, and stirring to obtain a sample to be activated; step 3: placing a sample to be activated into a 105 ℃ oven for drying, and grinding and sieving the sample with a 20-mesh sieve; step 4: placing the sample prepared in the step 3 into a tube furnace for pyrolysis to obtain biochar; step 5: fully pickling the biochar in a pickling solution, washing the biochar to be neutral by using hot deionized water, drying the biochar in an oven, and grinding the dried biochar to obtain the mixed-melt activated biochar. The invention adopts the method for preparing the sludge biochar by mixing and activating, and utilizes the method of drying and pyrolyzing the mixed sludge obtained by uniformly mixing zinc chloride and wet sludge to perform mixing and activating so as to obtain the sludge biochar with larger specific surface area and richer surface functional groups.
Description
Technical Field
The invention relates to the technical field of sludge treatment, in particular to a method for preparing sludge biochar by mixing and melting activation.
Background
The sludge produced by sewage treatment plants contains various toxic organic and inorganic components, such as heavy metals, antibiotics, pathogens, nitrogen and phosphorus pollutants, and if the sludge cannot be properly treated, the sludge can cause great harm to the environment and human health. Meanwhile, the sludge also contains a large amount of organic carbon, and if the sludge can be effectively recycled, the sludge can be recycled, so that the method has important practical significance.
The sludge pyrolysis is an environment-friendly, economical and efficient sludge treatment technology, is performed under the anoxic or anaerobic condition, avoids the problem of secondary pollution, can completely pyrolyze the components such as organic pollutants, antibiotics and the like which are difficult to degrade in the sludge, can fix heavy metals and kill pathogens, can convert the sludge into a biochar material with larger specific surface area and rich surface functional groups and high added value, and realizes the recycling utilization of the sludge. However, the untreated raw pyrolytic biochar material still has limited specific surface area and functional groups, and has difficulty in achieving good pollutant adsorption effect. The activated biochar is mainly characterized in that the surface morphology of the biochar is modified under the high temperature condition by the action of an activating agent to form more pore structures so as to improve the performance of the biochar, and the method is mainly divided into a physical activating method, a chemical activating method and a physicochemical activating method.
The zinc chloride activation method is one of the most widely applied chemical activation methods in industrialization at home and abroad, and has low pyrolysis temperature requirement, correspondingly lower energy consumption and lower cost. At present, zinc chloride is activated mainly by preparing biochar by pyrolysis after carrying out dipping treatment on dehydrated sludge which is dried, but the specific surface area of the biochar obtained by the method is still limited, and the requirement on the zinc chloride dosage is high. In order to solve the problems, a novel sludge biochar preparation method is needed.
Disclosure of Invention
The invention aims to provide a mixed-melting activation preparation method of sludge biochar, which is characterized in that mixed sludge obtained by uniformly mixing zinc chloride and wet sludge is dried and pyrolyzed for mixed-melting activation so as to obtain sludge biochar with larger specific surface area and richer surface functional groups.
In order to achieve the above purpose, the invention provides a method for preparing sludge biochar by mixing and activating, which comprises the following steps:
step 1: the sludge is screened and concentrated to obtain concentrated sludge, and the concentration of the concentrated sludge is 20-100g/L;
step 2: mixing the concentrated sludge and zinc chloride according to the mixing mass ratio of 0.5:1-5:1 of the zinc chloride to the concentrated sludge to obtain mixed sludge, and continuously stirring the mixed sludge at 40-200rpm for 30min-24h to obtain a sample to be activated;
step 3: placing a sample to be activated into a 105 ℃ oven for drying, and grinding and sieving the sample with a 20-mesh sieve;
step 4: paving the sample prepared in the step 3 in a porcelain boat, and putting the porcelain boat in a tube furnace for pyrolysis under the protection of inert gas to obtain biochar; the inert gas is nitrogen or argon, and ventilation is started for 10-30min to discharge air and ensure the inert gas atmosphere in the tube furnace; the pyrolysis temperature is 400-800 ℃, the heating rate is 3-15 ℃/min, and the pyrolysis time is 50-120min;
step 5: and (3) fully pickling the biochar prepared in the step (4) in a pickling solution, washing the biochar to be neutral by using hot deionized water, then putting the biochar into a 105 ℃ oven for drying to constant weight, grinding the dried biochar, and sieving the ground biochar with a 100-mesh sieve to obtain the mixed-melt activated biochar.
Preferably, the sludge in the step 1 comprises at least one of excess sludge and excess sludge anaerobic fermentation liquid, and the concentration treatment method is gravity concentration, centrifugal concentration or filtration concentration.
Preferably, the concentration of the concentrated sludge is 40-80g/L.
Preferably, in the step 2, the mixing mass ratio of the zinc chloride to the concentrated sludge is 1:1-3:1, the stirring speed is 60-120rpm, and the stirring time is 12-24h.
Preferably, the pyrolysis temperature in the step 4 is 450-650 ℃, the heating rate is 5-10 ℃/min, and the pyrolysis time is 50-70min.
Preferably, the acid washing solution in the step 5 is 1-3mol/L of dilute hydrochloric acid, the acid washing time is 10min-2h, and the temperature of the hot deionized water is 70+/-5 ℃.
Therefore, the method for preparing the sludge biochar by mixing and melting activation has the following beneficial effects:
1. according to the invention, sludge in a sewage treatment plant is used as a raw material, and the sludge biochar is prepared by high-temperature pyrolysis, so that not only can the reduction, stabilization and harmlessness of waste sludge in the sewage treatment plant be realized, but also the recycling of the sludge can be effectively realized;
2. the mixed melting activation mode of the invention can obviously increase the specific surface area of the sludge biochar, enrich oxygen-containing functional groups on the surface of the sludge biochar, and the prepared sludge biochar has a composite structure with developed internal pore structure and micro-mesopores, and can be used as an adsorbent with excellent performance to remove organic pollutants in water;
3. the method for mixing, melting and activating the sludge biochar reduces the consumption of zinc chloride, has the advantages of simple process, safe operation, high carbon yield, low cost, good performance and stable effect of activated biochar materials, has the condition of industrial production, and has good practical application prospect.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIGS. 1- (a) and (b) are SEM images of the blended activated biochar HR-SBC and the unactivated biochar SBC prepared in example 1 and comparative example 1, respectively;
FIGS. 2- (a) and (b) are graphs of nitrogen adsorption and desorption of the mixed and fused activated biochar HR-SBC and the unactivated biochar SBC prepared in example 1 and comparative example 1, respectively;
FIGS. 3- (a), (b) and (c) and (d) are pore size distribution and surface activation energy distribution diagrams of the mixed and fused activated biochar HR-SBC and the unactivated biochar SBC prepared in example 1 and comparative example 1, respectively;
FIGS. 4- (a) and (b) are XPSC1s peak-split fitting graphs of the mixed activated charcoal HR-SBC and the unactivated charcoal SBC prepared in example 1 and comparative example 1, respectively;
FIGS. 5- (a) and (b) are respectively an adsorption kinetic curve and an adsorption isothermal curve of the mixed-melt activated biochar HR-SBC prepared in example 1 for adsorbing p-chloronitrobenzene;
FIGS. 6- (a) and (b) are respectively the adsorption kinetics curve and adsorption isotherm curve of the mixed-melt activated biochar HR-DBC adsorbed phosphate prepared in example 2.
Detailed Description
Embodiments of the present invention will be further described with reference to the accompanying drawings.
The method for preparing the sludge biochar by mixing and melting activation comprises the following steps:
step 1: the sludge is screened and concentrated to obtain concentrated sludge, and the concentration of the concentrated sludge is 20-100g/L; the sludge comprises at least one of excess sludge and excess sludge anaerobic fermentation liquid, the concentration treatment method is gravity concentration, centrifugal concentration or filtration concentration, and the concentration of the concentrated sludge can be 40-80g/L.
Step 2: mixing the concentrated sludge and zinc chloride according to the mixing mass ratio of 0.5:1-5:1 of the zinc chloride to the concentrated sludge to obtain mixed sludge, and continuously stirring the mixed sludge at 40-200rpm for 30min-24h to obtain a sample to be activated; the mixing mass ratio of the zinc chloride to the concentrated sludge is 1:1-3:1, the stirring speed is 60-120rpm, and the stirring time is 12-24h.
Step 3: placing a sample to be activated into a 105 ℃ oven for drying, and grinding and sieving the sample with a 20-mesh sieve;
step 4: paving the sample prepared in the step 3 in a porcelain boat, and putting the porcelain boat in a tube furnace for pyrolysis under the protection of inert gas to obtain biochar; the zinc chloride inert gas is nitrogen or argon, and ventilation is started for 10-30min to discharge air and ensure the inert gas atmosphere in the tubular furnace; the pyrolysis temperature of the zinc chloride is 400-800 ℃, the heating rate is 3-15 ℃/min, and the pyrolysis time is 50-120min; the pyrolysis temperature of the zinc chloride is 450-650 ℃, the heating rate is 5-10 ℃/min, and the pyrolysis time is 50-70min.
Step 5: fully pickling the biochar prepared in the step 4 in a pickling solution, wherein the pickling solution is 1-3mol/L of dilute hydrochloric acid, the pickling time is 10min-2h, and then washing the biochar to be neutral by using hot deionized water, and the temperature of the hot deionized water is 70+/-5 ℃. And then drying the mixture in a 105 ℃ oven until the weight is constant, grinding the dried biochar, and sieving the ground biochar with a 100-mesh sieve to obtain the mixed-melt activated biochar.
Example 1
In the embodiment, the mixed melting activated biochar HR-SBC is prepared by taking excess sludge as a raw material and comprises the following steps:
s1, taking excess sludge as a raw material, sieving the sludge, and centrifuging to obtain concentrated sludge with the concentration of 60g/L;
s2, mixing the concentrated sludge and zinc chloride according to a mass ratio of 1:1 to obtain mixed sludge, and continuously stirring the mixed sludge at 120rpm for 24 hours to fully mix the mixed sludge to obtain a sample to be activated;
s3, placing the sample to be activated into a 105 ℃ oven for drying, and grinding and sieving with a 20-mesh sieve;
s4, paving the sample prepared in the step 3 in a porcelain boat, putting the porcelain boat in a tube furnace for pyrolysis under the protection of nitrogen, starting ventilation for 15min to discharge air and ensure inert gas atmosphere in the tube furnace, wherein the pyrolysis temperature is 600 ℃, the heating rate is 5 ℃/min, and the pyrolysis time is 50min;
s5, soaking the pyrolyzed biochar in 3mol/L dilute hydrochloric acid for 30min, washing the biochar to be neutral by using 70 ℃ deionized water, and then drying the biochar in a 105 ℃ oven until the weight is constant; grinding the dried biochar, and sieving the ground biochar with a 100-mesh sieve to obtain a final product of the mixed melting activated biochar HR-SBC.
Comparative example 1
The same as in example 1, except for steps S1-3: and (3) after the sludge is concentrated in the step (S1), directly performing the step (S3), and marking the finally obtained sample as biochar SBC.
According to the invention, the mixed melting activated biochar HR-SBC and the biochar SBC prepared in the embodiment 1 and the comparative example 1 are characterized, and the obtained scanning electron microscope pictures are shown in figures 1- (a) and (b), so that the mixed melting activated biochar HR-SBC in the embodiment 1 has a more developed pore structure, and the pores change from macropores to micropores, which is beneficial to adsorbing more pollutants.
As can be seen from the nitrogen adsorption and desorption curves shown in the figures 2- (a) and (b), under the condition of the same relative pressure, the nitrogen adsorption amount of the mixed-melt activated biochar HR-SBC is far greater than that of the biochar SBC, which indicates that micropores and mesopores of the mixed-melt activated biochar HR-SBC are more developed, and the specific surface area of the mixed-melt activated biochar HR-SBC is 1084.31m according to a BET equation 2 Per g, specific surface area of activated biochar SBC (388.26 m 2 Per g) is increased by 696.05m 2 /g。
The pore size distribution and the surface activation energy distribution diagram are shown in fig. 3 (a) and (b), and it can be seen that the mixed melting activated biochar HR-SBC has higher surface activation energy; the split peak fitting condition of XPS detection C1s is shown in figures 4- (a) and (b), and the obvious increase of the proportion of oxygen-containing groups of the mixed activated biochar HR-SBC and the decrease of the graphitization degree can be seen.
To examine the adsorption effect of the mixed-melt activated biochar HR-SBC prepared in example 1 on p-chloronitrobenzene in water, the following procedure was followed:
the pH of 60mg/L of 30mL of p-chloronitrobenzene (pCNB) solution is regulated to 7.0+/-0.2 by 0.1mol/L of dilute hydrochloric acid and 0.1mol/L of sodium hydroxide, 0.06g of charcoal HR-SBC is added into the system, the mixture is mixed and then is subjected to adsorption experiments in a constant temperature shaking box (150 rmp) at 25 ℃, samples are taken at different sampling times (0, 10, 20, 30, 45, 60, 90, 120, 150 and 180 min), after the 0.22 mu m PES polyether sulfone membrane is passed, the adsorption effect of the charcoal HR-SBC on the p-chloronitrobenzene is measured by a high performance liquid chromatograph, and the obtained data is fitted through a quasi-first-order kinetic model and a quasi-second-order kinetic model, and an adsorption kinetic curve is shown in figure 5- (a).
Preparing 30mL of p-chloronitrobenzene solution with initial concentrations of 0, 15, 30, 60, 90 and 120mg/L respectively, regulating the pH value to 7.0+/-0.2 by using dilute hydrochloric acid and sodium hydroxide, adding 0.06g of biochar HR-SBC into the system respectively, mixing, performing adsorption experiments in a constant-temperature shaking box (150 rmp) at 25 ℃, sampling after 24 hours, passing through a 0.22 mu m PES polyethersulfone membrane, measuring the adsorption effect of the biochar HR-SBC on the p-chloronitrobenzene by using a high performance liquid chromatograph, fitting the obtained data by using Langmuir, freundlich and Temkin isothermal adsorption models, and performing adsorption isothermal curves as shown in figure 5- (b).
Experimental results show that when the using amount of the mixed activated biochar HR-SBC prepared by using the surplus sludge as a raw material is 2g/L and the initial mass concentration of the p-chloronitrobenzene is 60mg/L, the adsorption rate of 74.04% can be reached within 30min, and the equilibrium can be reached rapidly within 45 min. From the fitting result of the model with better fitting effect, the adsorption capacity was 24.72mgpCNB/gbiochar (quasi-first order kinetic model, R 2 =0.979); the maximum theoretical adsorption capacity can reach 146.52mgpCNB/gbiochar (Langmuir model, R) 2 =0.993), the mixed activated biochar HR-SBC prepared by using the residual sludge as a raw material has a stronger adsorption effect on chloronitrobenzene.
Comparative example 2
The comparative example 2 is an activated biochar prepared by pyrolysis using a conventional zinc chloride activation method with excess sludge as a raw material, comprising the steps of:
s1, taking surplus sludge as a raw material, sieving the sludge, and centrifuging and concentrating to 60g/L;
s2, putting the concentrated sludge into a 105 ℃ oven for drying, and grinding and sieving the sludge with a 20-mesh sieve;
s3, dipping the dried sludge and zinc chloride according to a mass ratio of 1:1, continuously stirring the mixed sample at 120rpm for 24 hours to fully mix, and putting the uniformly mixed sample into a 105 ℃ oven for drying;
s4, paving the sample in a porcelain boat, putting the porcelain boat into a tube furnace for pyrolysis under the protection of nitrogen, starting ventilation for 15min to discharge air, ensuring inert gas atmosphere in the tube furnace, wherein the pyrolysis temperature is 600 ℃, the heating rate is 5 ℃/min, and the pyrolysis time is 50min;
s5, soaking the pyrolyzed biochar in 3mol/L dilute hydrochloric acid for 30min, washing the biochar to be neutral by using 70 ℃ deionized water, and then drying the biochar in a 105 ℃ oven until the weight is constant; grinding the dried biochar, and sieving with a 100-mesh sieve to obtain a final product JZ-SBC-1.
The obtained JZ-SBC-1 was subjected to a nitrogen adsorption/desorption test, and the specific surface area thereof was 530.60m as known by the BET equation 2 /g(R 2 =0.9998), example 1 specific surface area of activated biochar HR-SBC (1084.31 m 2 And/g) is improved by 100% compared with the traditional zinc chloride activated biochar JZ-SBC-1 of comparative example 2, which shows that the mixed melting activation mode can enrich the pore structure of the biochar and effectively improve the specific surface area of the biochar.
Comparative example 3
The basic procedure of this comparative example 3 is the same as comparative example 2 except that in step S3, the mass ratio of sludge to zinc chloride is 1:3, and the final sample is labeled JZ-SBC-2.
The obtained JZ-SBC-2 was subjected to a nitrogen adsorption/desorption test, and the specific surface area thereof was 791.05m as known by the BET equation 2 /g(R 2 =0.9998), the result shows that even though the zinc chloride dosage is increased by two times, the specific surface area is still lower than that of the mixed melting activated biochar HR-SBC of the example 1 by 293.26m 2 And/g, the mixed melting activation mode can effectively reduce the zinc chloride dosage.
Example 2
In this example 2, the mixed activated biochar HR-DBC is prepared from the anaerobic fermentation liquid of excess sludge, and comprises the following steps:
s1, taking excess sludge anaerobic fermentation liquid as a raw material, sieving the excess sludge anaerobic fermentation liquid, and centrifuging and concentrating to 60g/L;
s2, mixing the concentrated excess sludge anaerobic fermentation liquid and zinc chloride according to a mass ratio of 1:3, and continuously stirring the mixture at 120rpm for 24 hours to fully mix to obtain a sample to be activated;
s3, placing the sample to be activated into a 105 ℃ oven for drying, and grinding and sieving with a 20-mesh sieve;
s4, paving the sample obtained in the step three in a porcelain boat, putting the porcelain boat in a tube furnace, and carrying out pyrolysis under the protection of nitrogen to obtain biochar, starting ventilation for 15min to discharge air and ensure the inert gas atmosphere in the tube furnace, wherein the pyrolysis temperature is 500 ℃, the heating rate is 5 ℃/min, and the pyrolysis time is 60min;
s5, soaking the pyrolyzed biochar in 3mol/L dilute hydrochloric acid for 30min, washing the biochar to be neutral by using 70 ℃ deionized water, drying the biochar in a 105 ℃ oven until the weight is constant, grinding the dried biochar, and sieving the ground biochar with a 100-mesh sieve to obtain a final product HR-DBC.
The obtained HR-DBC was subjected to a nitrogen adsorption/desorption test, and the specific surface area thereof was 871.16m as known by BET equation 2 /g(R 2 ＝0.9998)。
In order to detect the adsorption effect of the mixed fusion activated excess sludge anaerobic fermentation liquid biochar HR-DBC prepared in the example 2 on phosphate in water, the following step test is carried out:
the pH value of 30mg/L of 40mL of potassium dihydrogen phosphate solution is regulated to 7.0+/-0.2 by 0.1mol/L of dilute hydrochloric acid and 0.1mol/L of sodium hydroxide, 0.08g of biochar HR-DBC is added into the system, the mixture is subjected to adsorption experiments in a constant temperature shaking box (150 rmp) at 25 ℃, sampling is carried out at different sampling times (0, 30, 60, 90, 120, 150 and 180 min), after passing through a 0.22 mu m PES polyether sulfone membrane, the adsorption effect of the biochar on phosphate is measured by an ultraviolet spectrophotometer, and the obtained data are fitted through a quasi-first-order kinetic model and a quasi-second-order kinetic model, and an adsorption kinetic curve is shown in figure 6- (a).
40mL of potassium dihydrogen phosphate solution with initial concentration of 20, 40, 60, 80, 120 and 140mg/L respectively is prepared, pH is regulated to 7.0+/-0.2 by dilute hydrochloric acid and sodium hydroxide, 0.08g of biochar HR-DBC is added into the system, the mixture is subjected to adsorption experiments in a constant temperature shaking box (150 rmp) at 25 ℃, sampling is carried out after 24 hours, after a 0.22 mu m PES polyethersulfone membrane is passed, the adsorption effect of the biochar on phosphate is measured by an ultraviolet spectrophotometer, the obtained data are fitted by adopting Langmuir, freundlich and Temkin isothermal adsorption models, and adsorption isothermal curves are shown in figure 6- (b).
As can be seen from the experimental results, when the excess sludge is used for anaerobic treatmentWhen the dosage of the mixed melting activated charcoal HR-DBC prepared by taking the fermentation broth as the raw material is 2g/L and the initial mass concentration of phosphate is 30mg/L, the adsorption rate of 60.00% can be reached within 30min, and the equilibrium can be reached within 120 min. From the fitting result of the model with better fitting effect, the adsorption capacity was 13.72mgTP/gbiochar (quasi-second-order kinetic model, R 2 =0.996), indicating that the adsorption process involves electron pair sharing or transfer between the adsorbents; the maximum theoretical adsorption capacity of the catalyst can reach 17.73mgTP/gbiochar (R) as known by Langmuir model fitting calculation 2 From the Freundlich model fitting calculation, 1/n=0.196 (n is the adsorption energy correlation constant, R) 2 =0.982), indicating that adsorption is easier to perform, indicating that the mixed-melt activated biochar HR-DBC exhibits better adsorption performance for phosphate.
Therefore, the method for preparing the sludge biochar by mixing and melting activation can obviously increase the specific surface area of the sludge biochar and enrich oxygen-containing functional groups on the surface, and the prepared sludge biochar has a composite structure with developed internal pore structure and micro-mesopores and can be used as an adsorbent with excellent performance to remove organic pollutants in water.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.
Claims (6)
1. A method for preparing sludge biochar by mixed melting and activation is characterized in that: the method comprises the following steps:
step 1: the sludge is screened and concentrated to obtain concentrated sludge, and the concentration of the concentrated sludge is 20-100g/L;
step 2: mixing the concentrated sludge and zinc chloride according to the mixing mass ratio of 0.5:1-5:1 to obtain mixed sludge, and continuously stirring the mixed sludge at 40-200rpm for 30min-24h to obtain a sample to be activated;
step 3: placing a sample to be activated into a 105 ℃ oven for drying, and grinding and sieving the sample with a 20-mesh sieve;
step 4: paving the sample prepared in the step 3 in a porcelain boat, and putting the porcelain boat in a tube furnace for pyrolysis under the protection of inert gas to obtain biochar; the inert gas is nitrogen or argon, and ventilation is started for 10-30min to discharge air and ensure the inert gas atmosphere in the tube furnace; the pyrolysis temperature is 400-800 ℃, the heating rate is 3-15 ℃/min, and the pyrolysis time is 50-120min;
step 5: and (3) fully pickling the biochar prepared in the step (4) in a pickling solution, washing the biochar to be neutral by using hot deionized water, then putting the biochar into a 105 ℃ oven for drying to constant weight, grinding the dried biochar, and sieving the ground biochar with a 100-mesh sieve to obtain the mixed-melt activated biochar.
2. The method for preparing sludge biochar by mixed melting and activating as claimed in claim 1, wherein the method comprises the following steps: the sludge in the step 1 comprises at least one of excess sludge and excess sludge anaerobic fermentation liquid, and the concentration treatment method is gravity concentration, centrifugal concentration or filtration concentration.
3. The method for preparing sludge biochar by mixed melting and activating as claimed in claim 2, wherein the method comprises the following steps: the concentration of the concentrated sludge is 40-80g/L.
4. The method for preparing sludge biochar by mixed melting and activating as claimed in claim 3, wherein the method comprises the following steps: in the step 2, the mixing mass ratio of the zinc chloride to the concentrated sludge is 1:1-3:1, the stirring speed is 60-120rpm, and the stirring time is 12-24h.
5. The method for preparing sludge biochar by mixed melting and activating as claimed in claim 4, wherein the method comprises the following steps: the pyrolysis temperature in the step 4 is 450-650 ℃, the heating rate is 5-10 ℃/min, and the pyrolysis time is 50-70min.
6. The method for preparing sludge biochar by mixed melting and activating as claimed in claim 5, wherein the method comprises the following steps: in the step 5, the acid washing solution is 1-3mol/L of dilute hydrochloric acid, the acid washing time is 10min-2h, and the temperature of the hot deionized water is 70+/-5 ℃.
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