CN114345310B - Polypyrrole coated layered double hydroxide composite material and preparation method and application thereof - Google Patents
Polypyrrole coated layered double hydroxide composite material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a synthetic method of an organic-inorganic hybrid composite material adsorbent and application thereof in removing anionic pollutants Cr (VI) in water. The method takes layered double hydroxide prepared by a coprecipitation method as a substrate, hydroxyl groups of the layered double hydroxide attract pyrrole monomers, an oxidant is added to synthesize polypyrrole outside the layered double oxide through in-situ oxidative polymerization, and the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) is prepared. The polypyrrole particles are dispersed by the existence of the layered double hydroxide, so that the synthesized PPy/LDH has excellent Cr (VI) adsorption performance, and Cr (VI) in water can be reduced to Cr (III) in water and fixed on the surface of the material.
Description
Technical Field
The invention relates to the field of nano material preparation and application, in particular to a preparation method and application of a polypyrrole coated layered double hydroxide composite material.
Background
With the rapid development of industry, the problem of water pollution caused by heavy metals increasingly threatens the ecological system and human health. Chromium (Cr) is a typical heavy metal contaminant and widely exists in the fields of metal plating, tanning, pigment chemical industry, chromium ore mining, and the like. The chromium in aqueous solution is usually present in trivalent and hexavalent oxidation states, wherein Cr (VI) has much higher hazard and toxicity than Cr (III), has mutagenicity and carcinogenicity, and is severely harmful to human health. In China, chromium is listed as a national hazardous waste directory. According to the regulations of national emission standards of chromium and its compound industrial pollutants, the allowable limit values of Cr (VI) and total chromium discharged from industrial wastewater to surface water are respectively 0.1 and 1.0mg/L. Because of the high flowability of Cr (VI) in water ecosystems and its high toxicity and carcinogenicity, there is an urgent need to develop efficient methods for more efficient Cr (VI) removal.
Currently, various repair techniques such as chemical precipitation, ion exchange, adsorption, membrane filtration, photocatalytic reduction, electrochemical reduction, etc. have been used for the treatment of Cr (VI) wastewater. The adsorption method has the advantages of convenient operation, good stability, high efficiency and the like, and is widely applied to Cr (VI) removal technology. However, incomplete removal of micro-traces of Cr (VI) in water remains a major limitation of current adsorption technology.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention provides a composite material for preparing polypyrrole coated layered double hydroxide by an in-situ chemical oxidation polymerization method, and the composite material is used as a high-efficiency adsorbent capable of reducing low-concentration heavy metal ions Cr (VI) to a standard limit value. The adsorption capacity of the catalyst for Cr (VI) in wastewater is higher, and the adsorption capacity of the catalyst is higher, and the adsorption removal rate of Cr (VI) with low concentration is higher.
The aim of the invention is realized by adopting the following technical scheme:
in a first aspect, the invention provides a preparation method of an organic-inorganic hybrid polypyrrole coated layered double hydroxide composite material, which comprises the following steps:
step 1, ni (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixing O into formamide aqueous solution, and performing coprecipitation reaction under alkaline conditions to prepare NiFe hydroxide precursor mixed solution;
step 2, carrying out solid separation on the NiFe hydroxide precursor mixed solution, drying and fully grinding the solid to obtain NiFe hydroxide;
step 3, dispersing NiFe hydroxide into deionized water, and stirring at room temperature in a dark way to form NiFe hydroxide solution;
step 4, pyrrole monomers and hexadecyl trimethyl ammonium bromide are added into the NiFe hydroxide solution, and are stirred and dispersed uniformly to obtain NiFe hydroxide mixed solution;
step 5, adding the ammonium persulfate solution into the NiFe hydroxide mixed solution, and continuously stirring and mixing to generate black polymer;
and 6, separating the black polymer from the mixed solution, and drying and grinding to obtain the polypyrrole coated layered double hydroxide composite material.
Preferably, in the step 1, the volume percentage of the aqueous formamide solution is 23%.
Preferably, in the step 1, ni (NO 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 After O is mixed into the formamide aqueous solution, the molar concentration ratio of nickel ions to iron ions in the solution is 3:1, and the total molar quantity of metal ions is 1-20 mmol.
Preferably, in the step 1, the alkaline condition is that the NaOH solution is continuously added dropwise to maintain the ph=10 of the system, and the concentration of the NaOH solution is 0.25 to 5mol/L.
Preferably, in the step 1, the temperature of the coprecipitation reaction is 75 to 85 ℃.
Preferably, in the step 3, the solid-to-liquid ratio of the NiFe hydroxide to the deionized water is 150-300 mg/100 mL.
Preferably, in the step 3, the dark stirring time at room temperature is 0.5-1 h.
Preferably, in the step 4, the addition amount of the pyrrole monomer is 50 to 300. Mu.L, and the addition amount of the cetyl trimethylammonium bromide is 50 to 100mg.
Preferably, in the step 5, the ammonium persulfate solution is a hydrochloric acid solution in which ammonium persulfate is dissolved in a concentration of 0.25 to 1 mol/L; the concentration of the ammonium persulfate solution was 0.895mol/L.
Preferably, in the step 5, the volume of the ammonium persulfate solution is 1.25mL.
In a second aspect, the invention provides an organic-inorganic hybrid polypyrrole coated layered double hydroxide composite material prepared by the preparation method.
Preferably, the organic-inorganic hybrid polypyrrole-coated layered double hydroxide composite material PPy/LDH is a black solid powder; the microstructure is nano sphere piled particles with rough surfaces and irregular shapes.
In a third aspect, the invention provides an application of the organic-inorganic hybrid polypyrrole coated layered double hydroxide composite material prepared by the preparation method in Cr (VI) adsorption.
Preferably, the application method specifically comprises the following steps:
adding a certain amount of PPy/LDH composite material into a solution with an initial pH value of 3-11 and a Cr (VI) concentration of 30-300 mg/L, oscillating a shaking table at constant temperature for adsorption, filtering the solution after adsorption balance, and taking the supernatant to measure the Cr (VI) concentration, wherein the maximum adsorption capacity of Cr (VI) can reach 338.9mg/g.
Preferably, when the organic-inorganic hybrid polypyrrole coated layered double hydroxide composite material is applied, the PPy/LDH composite material is used for adsorbing Cr (VI) containing solution in a circulating regeneration mode, and after the adsorbent is used for 3 times in a circulating regeneration mode, the removal rate of 20mg/L Cr (VI) solution in the first two times is more than 95%.
The beneficial effects of the invention are as follows:
the invention prepares a NiFe bimetallic oxide precursor by a coprecipitation method, and uses the precursor as a substrate to generate the organic-inorganic hybrid PPy/LDH composite material by in-situ oxidative polymerization.
Firstly, compared with other methods, the method disclosed by the invention is simple to operate, and the synthesized PPy/LDH has excellent Cr (VI) adsorption performance, so that the excellent adsorption performance can be maintained under the condition of pH of 5, and the condition that the pH of an adsorption system is too low is avoided.
Second, more significantly, the PPy/LDH of the present invention is effective in scavenging low concentrations of Cr (VI), from 10mg/L down to the maximum allowable level of Cr (VI) in drinking water (0.05 mg/L).
In addition, the material obtained by the invention has better stability and safety, can reduce the adsorbed Cr (VI) into Cr (III) with lower toxicity, and the trivalent chromium after reduction is fixed on the material instead of being released into the solution, thereby facilitating the subsequent treatment.
Drawings
The invention will be further described with reference to the accompanying drawings, in which embodiments do not constitute any limitation of the invention, and other drawings can be obtained by one of ordinary skill in the art without inventive effort from the following drawings.
FIG. 1 is an SEM image of a PPy/LDH composite of example 1;
FIG. 2 is an SEM image of the PPy/LDH composite of example 2;
FIG. 3 is a TEM image of the PPy/LDH composite of example 2;
FIG. 4 is a graph showing the relationship between the removal rate of the PPy/LDH composite material prepared in example 2 and Cr (VI) solution and the adsorption time;
FIG. 5 is a graph showing the relationship between the removal rate of the PPy/LDH composite material prepared in example 2 and Cr (VI) solution and the adsorption time;
FIG. 6 shows the adsorption performance of the PPy/LDH composite material prepared in example 2 on Cr (VI) solutions at different pH values of the Cr (VI) solutions;
FIG. 7 is a bar graph of the repeated activity evaluation of the PPy/LDH composite material prepared in example 2.
Detailed Description
The technical features, objects and advantages of the present invention will be more clearly understood from the following detailed description of the technical aspects of the present invention, but should not be construed as limiting the scope of the invention.
The invention will be further described with reference to the following examples.
Example 1
A preparation method of a polypyrrole coated layered double hydroxide composite material, which comprises the following steps:
(1) 2.181g of nickel nitrate (Ni (NO) 3 ) 2 ·6H 2 O), 1.010g of ferric nitrate (Fe (NO) 3 ) 3 ·9H 2 O) dissolving in 20mL of deionized water, and carrying out ultrasonic dissolution at normal temperature to obtain a metal ion aqueous solution; the obtained metal ion aqueous solution and 2.5MNaOH solution are the same asDropwise adding the mixture into a 23vol.% formamide aqueous solution at 80 ℃, keeping pH=10 in the dropwise adding process, magnetically stirring, and obtaining yellow precipitate after the reaction is finished;
(2) Separating, drying and fully grinding the yellow precipitate prepared in the step (1);
(3) 300mg of the solid obtained in the step (2) is dispersed into 100mL of deionized water solution, and the solution is stirred for 0.5h at room temperature in a dark way;
(4) 75 μl of pyrrole monomer and 75mg of cetyltrimethylammonium bromide (CTAB) were added to the dispersed mixed system described in (3), stirring was continued for 1h;
(5) 1.25mL of ammonium persulfate solution with the concentration of 0.895mol/L is injected into the mixed system in the step (4), and stirring is continued for 12 hours, so that a black polymer is obtained; the ammonium persulfate solution is hydrochloric acid solution with the concentration of 0.25-1 mol/L;
(6) The black solid of step (5) is isolated, dried and sufficiently ground.
Among them, FIG. 1 is an SEM image of a polypyrrole-coated layered double hydroxide composite material (PPy/LDH) obtained in example 1.
Example 2
A preparation method of a polypyrrole coated layered double hydroxide composite material, which comprises the following steps:
(1) 1.0905g of nickel nitrate (Ni (NO) 3 ) 2 ·6H 2 O), 0.5050g of ferric nitrate (Fe (NO) 3 ) 3 ·9H 2 O) dissolving in 20mL of deionized water, and carrying out ultrasonic dissolution at normal temperature to obtain a metal ion aqueous solution; the obtained metal ion aqueous solution and 1.25m naoh solution were simultaneously added dropwise to a 23vol.% formamide aqueous solution at 80 ℃ while maintaining ph=10 during the addition, magnetically stirred, and a yellow precipitate was obtained after the reaction was completed.
(2) Separating, drying and fully grinding the yellow precipitate prepared in the step (1);
(3) 150mg of the solid obtained in the step (2) is dispersed into 100mL of deionized water solution, and the solution is stirred for 0.5h at room temperature in a dark way;
(4) 200 μl of pyrrole monomer and 75mg of cetyltrimethylammonium bromide (CTAB) were added to the dispersed mixed system described in (3), and stirring was continued for 0.5h;
(5) 1.25mL of ammonium persulfate solution with the concentration of 0.895mol/L is injected into the mixed system in the step (4), and stirring is continued for 12 hours, so that a black polymer is obtained; the ammonium persulfate solution is a hydrochloric acid solution in which ammonium persulfate is dissolved in a concentration of 0.25 to 1 mol/L.
(6) The black solid of step (5) is isolated, dried and sufficiently ground.
Fig. 2 and 3 are SEM and TEM images of the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) prepared in this example.
Example 3
As a method for removing Cr (VI) in water, which is an embodiment of the invention, the method comprises the following steps:
5mg of the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) synthesized in example 2 was put into 20mL of a 10mg/L Cr (VI) solution, the initial pH value was about 5.0, the mixture was magnetically stirred at room temperature, samples were taken and filtered at different time points, and the supernatant was taken to detect the concentration of pollutants. The relation curve of the removal rate of the PPy/LDH composite material to Cr (VI) along with the adsorption time is shown in FIG. 4, after 24 hours of adsorption, the removal rate of Cr (VI) can reach 99.8%, the adsorption capacity is 40.9mg/g, and the concentration of the residual Cr (VI) is only 0.02mg/L and is lower than the maximum allowable level (0.05 mg/L) of Cr (VI) in drinking water.
Example 4
5mg of the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) synthesized in example 2 was put into 20mL of a 50mg/L Cr (VI) solution, the initial pH value was about 5.0, the mixture was magnetically stirred at room temperature, samples were taken and filtered at different time points, and the supernatant was taken to detect the concentration of pollutants. The relation curve of the removal rate of Cr (VI) by the PPy/LDH composite material is shown in figure 5, and after 12 hours of adsorption, the removal rate of Cr (VI) is 57.1%, and the adsorption capacity can reach 112.3mg/g.
Example 5
5mg of the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) synthesized in example 2 is put into 20mL of 50mg/L Cr (VI) solution, a certain amount of 1M hydrochloric acid or sodium hydroxide solution is used for adjusting the pH value of the Cr (VI) solution to an initial pH value, the pH value is adjusted, the mixture is subjected to constant-temperature vibration adsorption, sampling and filtration are carried out after adsorption balance, and the supernatant is taken to detect the concentration of Cr (VI) pollutants.
The relation between the removal rate and the adsorption capacity of the PPy/LDH composite material to Cr (VI) and pH is shown in FIG. 6.
Example 6
60mg of the polypyrrole-coated layered double hydroxide composite material (PPy/LDH) synthesized in example 2 was put into 120mL of a 20mg/L Cr (VI) solution, the initial pH value was about 5.0, the temperature was kept at 35 ℃, sampling and filtration were carried out after adsorption equilibrium, and the concentration of pollutants was measured by taking the supernatant.
Experiments were repeated 3 times.
FIG. 7 is a bar graph of the repeated activity evaluation of polypyrrole coated layered double hydroxide composite material (PPy/LDH) prepared in example 2. From the graph, the removal rate of the adsorbent PPy/LDH on Cr (VI) still reaches 60% after three-cycle experiments, wherein the removal rate of the former two cycles is more than 95%.
In conclusion, the polypyrrole coated layered double hydroxide composite material can reduce the concentration of low-concentration Cr (VI) to below a standard limit value, has excellent Cr (VI) removal performance, provides a new idea for solving the limitation that an adsorbent is not used for completely removing Cr (VI) in water in the technical field of adsorption, and has good application prospect.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (9)
1. The preparation method of the polypyrrole coated layered double hydroxide composite material is characterized by comprising the following steps of:
step 1, ni (NO) 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 Mixing O into formamide water solution under alkaline conditionCoprecipitation reaction is carried out to prepare NiFe hydroxide precursor mixed solution;
step 2, carrying out solid separation on the NiFe hydroxide precursor mixed solution, drying and fully grinding the solid to obtain NiFe hydroxide;
step 3, dispersing NiFe hydroxide into deionized water, and stirring at room temperature in a dark way to form NiFe hydroxide solution;
step 4, pyrrole monomers and hexadecyl trimethyl ammonium bromide are added into the NiFe hydroxide solution, and are stirred and dispersed uniformly to obtain NiFe hydroxide mixed solution;
step 5, adding the ammonium persulfate solution into the NiFe hydroxide mixed solution, and continuously stirring and mixing to generate black polymer;
and 6, separating the black polymer from the mixed solution, and drying and grinding to obtain the polypyrrole coated layered double hydroxide composite material.
2. The method for preparing a polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 1, the volume percentage of the aqueous formamide solution is 23%.
3. The method for preparing a polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in step 1, ni (NO 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 And mixing O into the formamide aqueous solution, wherein the molar concentration ratio of nickel ions to iron ions in the solution is 3:1, and the total molar quantity of metal ions is 1-20 mmol.
4. The method for preparing the polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 1, an NaOH solution is continuously added dropwise under an alkaline condition to maintain ph=10 of the system, and the concentration of the NaOH solution is 0.25 to 5mol/L.
5. The method for preparing a polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 1, the temperature of the coprecipitation reaction is 75-85 ℃.
6. The method for preparing a polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 3, the solid-to-liquid ratio of NiFe hydroxide to deionized water is 150~300 mg:100mL.
7. The method for preparing the polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 4, the addition amount of pyrrole monomer is 50-300 μl, and the addition amount of cetyl trimethyl ammonium bromide is 50-100 mg.
8. The method for preparing the polypyrrole coated layered double hydroxide composite material according to claim 1, wherein in the step 5, the ammonium persulfate solution is prepared by dissolving ammonium persulfate in a hydrochloric acid solution with a concentration of 0.25-1 mol/L, and the concentration of the ammonium persulfate solution is 0.895mol/L.
9. Use of a composite material coated with a layered double hydroxide according to claim 1 for the adsorption of Cr (VI).
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107275611A (en) * | 2017-06-19 | 2017-10-20 | 南昌航空大学 | The spherical zinc oxide material of nanometer and preparation method of a kind of polypyrrole cladding |
| CN111892123A (en) * | 2020-06-19 | 2020-11-06 | 太原理工大学 | Preparation method of anionic surfactant modified conductive polymer-layered double hydroxide oil-water separation membrane |
| CN112063386A (en) * | 2020-09-25 | 2020-12-11 | 中科院过程工程研究所南京绿色制造产业创新研究院 | Layered double-metal hydroxide composite material and preparation method and application thereof |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107275611A (en) * | 2017-06-19 | 2017-10-20 | 南昌航空大学 | The spherical zinc oxide material of nanometer and preparation method of a kind of polypyrrole cladding |
| CN111892123A (en) * | 2020-06-19 | 2020-11-06 | 太原理工大学 | Preparation method of anionic surfactant modified conductive polymer-layered double hydroxide oil-water separation membrane |
| CN112063386A (en) * | 2020-09-25 | 2020-12-11 | 中科院过程工程研究所南京绿色制造产业创新研究院 | Layered double-metal hydroxide composite material and preparation method and application thereof |
Non-Patent Citations (1)
| Title |
|---|
| 聚吡咯对Cr(Ⅵ)离子的吸附性能研究;孙万虹;孙豫;周艳青;刘娟丽;王彦斌;陈丽华;朱利云;;材料保护(10);94-99 * |
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