A chromium and arsenic synchronous removal-conversion type biomass-based adsorption material, a preparation method and application thereof

Abstract

The application discloses a kind of chromium and arsenic synchronous removal-conversion type biomass-based adsorption material and its preparation method and application, belong to environmental management technical field, solve the problem of chromium arsenic coexisting wastewater difficult management.The biomass-based adsorption material is by introducing high-density amino and light response component on biomass matrix, then they are solidified by one-step rapid crosslinking strategy to prepare stable heavy metal adsorption material.The biomass-based adsorption material can be used for efficient adsorption of hexavalent chromium and trivalent arsenic, and hexavalent chromium and trivalent arsenic are converted into less toxic trivalent chromium and pentavalent arsenic, realizing synchronous removal and conversion.The biomass-based adsorption material prepared by the application can completely remove chromium and arsenic in water, and the conversion rates of hexavalent chromium and trivalent arsenic both reach more than 95%, effectively utilize light source and amplify the synergistic effect between pollutants to weaken the competitive effect, and help global carbon emission reduction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental governance, and particularly relates to a chromium and arsenic synchronous removal-transformation biomass-based adsorption material and a preparation method and application thereof. BACKGROUND

[0002] Chromium and arsenic are the two most dangerous pollutants in industrial wastewater, posing a significant risk to groundwater resources and public health. Chromium and arsenic usually exist in the form of oxygen-containing anions, including hexavalent chromium, trivalent arsenic and pentavalent arsenic. These substances often coexist in wastewater, especially wastewater from wood preservatives and acid mine drainage. Considering the high toxicity and high mobility of hexavalent chromium and trivalent arsenic, and the feature that the interaction between chromium and arsenic increases the complexity of heavy metal wastewater treatment, achieving rapid adsorption of them and transforming them into trivalent chromium and pentavalent arsenic with less toxicity is an effective water treatment strategy. Among numerous wastewater treatment technologies, adsorption is a green, low-carbon and sustainable wastewater treatment technology because its goal is consistent with carbon neutrality. Amino modification is considered a simple and effective method to improve the adsorption performance of oxygen-containing metal anions through electrostatic interaction, but trivalent arsenic usually exists in an electrically neutral form, which limits the adsorption effect of amino-modified materials on it. In addition, hexavalent chromium and pentavalent arsenic have the same electric properties and adsorption mechanisms, and thus there is a competitive behavior for adsorption sites. Therefore, designing a material that can transform trivalent arsenic into pentavalent arsenic while improving the adsorption efficiency of chromium and arsenic is of great significance for the treatment of water bodies containing chromium and arsenic pollutants such as wood preservative wastewater and acid mine wastewater. SUMMARY

[0003] The present application aims to provide a chromium and arsenic synchronous removal-transformation biomass-based adsorption material and a preparation method thereof. The material has abundant amino adsorption sites and good photo-thermal and photocatalytic properties, and can efficiently adsorb hexavalent chromium and trivalent arsenic while transforming them into trivalent chromium and pentavalent arsenic with lower toxicity, achieving the synchronous removal and transformation of hexavalent chromium and trivalent arsenic.

[0004] The above-mentioned object of the present application is achieved by the following technical solution:

[0005] The present application provides a preparation method of a chromium and arsenic synchronous removal-transformation biomass-based adsorption material. The method introduces amino groups, reduced iron and coconut shell carbon containing C=C double bonds into a biomass matrix through ring-opening reaction of epichlorohydrin, thereby preparing the chromium and arsenic synchronous removal-transformation biomass-based adsorption material.

[0006] The preparation method of the coconut shell carbon containing C=C double bonds comprises the following steps: under the condition of an inert atmosphere, the coconut shell is heated at a rate of 5-15℃·min -1to 600-900℃ at a heating rate of 5-15℃·min-1 for 45-130min; the pyrolysis product is mixed with KMnO4 solution and dried at 80-105℃; the dried mixture is mixed with NaOH or KOH, and the mixture is ground to 300 mesh; -1 to 600-800℃ at a heating rate of 5-15℃·min-1 for 60-120min; the secondary pyrolysis product is washed with water until the pH value is neutral, and then dried at 90-105℃ to obtain coconut shell charcoal containing C=C double bonds, which is ground to 300 mesh;

[0007] The amino group is derived from an amine compound.

[0008] Further, the biomass is eucalyptus wood, pine wood, rice husk, straw or peanut shell, which is crushed to 200-400 mesh, cleaned and then placed in an oven to dry.

[0009] Further, the amine compound is polyethyleneimine, diethylene triamine, tetraethylene pentaamine, pentaethylene hexamine, polyallylamine or branched amine.

[0010] Further, the addition amount of the coconut shell, KMnO4 solution, NaOH or KOH is 1.0g:0.5-2.5mL:0.3-2.0g, and the mass concentration of the KMnO4 solution is 0.3%-4.0%.

[0011] Further, the above-mentioned preparation method of the chromium and arsenic synchronous removal-transformation type biomass-based adsorption material mainly comprises the following steps: mixing biomass, an amine compound, coconut shell charcoal containing C=C double bonds, reduced iron powder and deionized water, and stirring at 200-600rpm for 5-25min; then adding epichlorohydrin to initiate crosslinking reaction until the mixture is converted from liquid to solid; washing the obtained solid product to neutral and vacuum freeze-drying to obtain the chromium and arsenic synchronous removal-transformation type biomass-based adsorption material.

[0012] Further, the addition amount of the biomass, amine compound, coconut shell charcoal containing C=C double bonds, reduced iron powder, deionized water and epichlorohydrin is 1.0g:1.0-6.0g:1.0-3.0g:0.5-1.5g:10-28mL:3.0-10.0mL.

[0013] In addition, the present application also provides a chromium and arsenic synchronous removal-transformation type biomass-based adsorption material prepared by the above-mentioned preparation method.

[0014] The present invention also provides the use of a biomass-based adsorbent material for simultaneous chromium and arsenic removal and conversion, prepared by the aforementioned method, for removing chromium and arsenic while reducing their toxicity. The biomass-based adsorbent material is placed in heavy metal wastewater containing chromium and arsenic. Under xenon lamp irradiation and stirring, the adsorbent material absorbs hexavalent chromium and trivalent arsenic while converting them into less toxic trivalent chromium and pentavalent arsenic, respectively.

[0015] The present invention has the following beneficial effects:

[0016] (1) The biomass-based adsorption material prepared by the present invention has excellent photothermal and photocatalytic properties. Under light irradiation, the material not only heats up to above 60°C but also generates photogenerated electrons that can convert hexavalent chromium into trivalent chromium and holes and hydroxyl radicals that convert trivalent arsenic into pentavalent arsenic. This improves the adsorption rate and enhances the conversion rate of hexavalent chromium and trivalent arsenic.

[0017] (2) The one-step rapid cross-linking technology adopted in the present invention introduces reduced iron into the biomass-based adsorption material in the form of various iron oxides, and the iron component acts as an electron bridge between hexavalent chromium and trivalent arsenic through the self-Fenton effect, further improving the conversion rate of hexavalent chromium and trivalent arsenic.

[0018] (3) The biomass-based adsorption material prepared by the present invention has abundant adsorption sites for anionic heavy metals (chromium, arsenic, etc.); it enhances the synergistic conversion between hexavalent chromium and trivalent arsenic. The hexavalent chromium preferentially adsorbed on the material not only enhances the conversion of trivalent arsenic, but also promotes the adsorption of pentavalent arsenic by enhancing the local electrical properties of the amino group.

[0019] (4) The biomass-based adsorption material prepared by the present invention can achieve rapid removal of chromium and arsenic from heavy metal wastewater (20-60 minutes), with maximum adsorption capacities exceeding 310 mg / L and 240 mg / L for chromium and arsenic, respectively. Furthermore, the chromium and arsenic enriched in the adsorption material exist primarily in the less toxic forms of Cr(III) and As(V), with conversion rates exceeding 95% for both hexavalent chromium and trivalent arsenic, achieving simultaneous removal and conversion of hexavalent chromium and trivalent arsenic. DETAILED DESCRIPTION

[0020] The eucalyptus wood, pine wood and rice husks used in the following Examples 1-3 were all crushed, cleaned, and then placed in an oven to dry.

[0021] Example 1

[0022] 1. Take 30g coconut shell and place it in a tube furnace under inert atmosphere at 15℃·min -1The temperature was raised to 800℃ and pyrolyzed for 60min. The pyrolysis product was mixed with KMnO4 (20.0mL, 1wt%) solution and dried at 80℃. The dried mixture was mixed with 45g KOH and heated at 10℃·min -1 The temperature was raised to 800°C for secondary pyrolysis for 60 min. The product was then washed with water until the pH value was neutral and dried at 95°C to obtain coconut shell charcoal containing C=C double bonds, which was then ball-milled to 300 mesh.

[0023] 2. Eucalyptus (0.50 g, 200 mesh), polyethyleneimine (2.00 g), coconut shell charcoal containing C=C double bonds (1.00 g), and reduced iron powder (0.30 g) were mixed with 10.00 mL of deionized water and stirred at 200 rpm for 25 minutes. Subsequently, 2.00 mL of epichlorohydrin was added to initiate a crosslinking reaction until the mixture underwent liquid-solid conversion. The resulting solid sample was washed with deionized water until neutral and freeze-dried in vacuo to obtain the product, a eucalyptus-based adsorbent material for simultaneous chromium and arsenic removal and conversion.

[0024] 0.05 g of the eucalyptus-based adsorbent prepared in Example 1 was placed in a beaker containing 50 mL of a chromium-arsenic mixture (with 50 mg / L Cr(VI) and 50 mg / L As(III) concentrations, respectively). The mixture was stirred at 180 rpm under xenon lamp irradiation. Samples were taken every 10 minutes, and 8 mL of the solution was syringed and filtered through a 0.22 μm water filter. The resulting solution was then measured for chromium and arsenic concentrations using ICP-OES. At 20 and 50 minutes, the chromium and arsenic concentrations in the samples were both 0 mg / L, indicating complete removal of chromium and arsenic. XPS spectra showed that the conversion rates of hexavalent chromium and trivalent arsenic on the eucalyptus-based adsorbent adsorbed with the chromium-arsenic mixture were 98.57% and 95.63%, respectively. The material was washed three times with a 0.1M HCl solution and then a NaOH solution, and finally rinsed with clean water to a neutral pH value for regeneration experiments. It was found that the eucalyptus-based adsorption material prepared in Example 1 could still achieve a chromium and arsenic removal rate exceeding 90% after five cycles. One gram of the eucalyptus-based adsorption material prepared in Example 1 was placed in an adsorption column for dynamic adsorption experiments, and its maximum adsorption capacities for hexavalent chromium and trivalent arsenic reached 323 mg / L and 269 mg / L, respectively.

[0025] Example 2

[0026] 1. Take 30g coconut shell and place it in a tube furnace under inert atmosphere at 10℃·min -1 The temperature was raised to 900℃ and pyrolyzed for 45min. The pyrolysis product was mixed with KMnO4 (75.0mL, 0.3wt%) solution and dried at 95℃. The dried mixture was mixed with 9g NaOH and heated at 15℃·min-1 The temperature ramping rate was increased to 700 °C for secondary pyrolysis and the pyrolysis time was 90 min. Subsequently, the product was washed with water until the pH value was neutral and dried at 90 °C to obtain the coconut shell char containing C=C double bonds, which was ball milled to 300 mesh.

[0027] 2. Pine wood (1.00 g, 300 mesh), polyethyleneimine (6.00 g), coconut shell char containing C=C double bonds (3.00 g), and reduced iron powder (1.50 g) were mixed with 10.00 mL of deionized water and stirred at 300 rpm for 15 min. Subsequently, 3.0 mL of epichlorohydrin was added to initiate the cross-linking reaction until the liquid-solid transformation of the mixture occurred. The obtained solid sample was washed with deionized water until neutral and vacuum freeze-dried to obtain the product, which was a pine wood-based adsorbent material for simultaneous removal and transformation of chromium and arsenic.

[0028] A 0.05 g pine wood-based adsorbent material prepared in Example 2 was placed in a beaker containing 50 mL of a chromium-arsenic mixed solution (the concentrations of Cr(VI) and As(III) were 50 mg / L, respectively), and the reaction was carried out under xenon lamp irradiation on a magnetic stirrer at a rotation speed of 180 rpm. Samples were taken every 10 min, 8 mL of the solution was taken using a syringe and filtered using a water filter head with a pore size of 0.22 μm, and the obtained solution was measured for the concentrations of chromium and arsenic using ICP-OES. The concentrations of chromium and arsenic in the samples were both 0 mg / L at 30 min and 50 min, respectively, i.e., the complete removal of chromium and arsenic was achieved. XPS spectra showed that the conversion rates of Cr(VI) and As(III) on the pine wood-based adsorbent material adsorbed with the chromium-arsenic mixed solution were 96.74% and 96.88%, respectively. The material was washed three times with 0.1 M HC1 solution and NaOH solution, respectively, and finally washed with clean water until the pH value was neutral for the recycling regeneration experiment. It was found that the pine wood-based adsorbent material prepared in Example 2 could still achieve a removal rate of chromium and arsenic of more than 90% after five cycles. A 1 g pine wood-based adsorbent material prepared in Example 2 was placed in an adsorption column for dynamic adsorption experiment, and the maximum adsorption capacities of the material for Cr(VI) and As(III) were 313 mg / L and 282 mg / L, respectively.

[0029] Example 3

[0030] 1. 30 g of coconut shell was placed in a tube furnace, and pyrolysis was carried out at a temperature ramping rate of 5 °C·min -1 -1 to 600 °C for 130 min under an inert atmosphere. The pyrolysis product was mixed with a KMnO4 (15.0 mL, 4.0 wt%) solution and dried at 105 °C. The dried mixture was mixed with 60 g of KOH, and pyrolysis was carried out at a temperature ramping rate of 5 °C·min -1The temperature rate was raised to 600 °C for secondary pyrolysis and the pyrolysis time was 120 min. Subsequently, the product was washed with water until the pH value was neutral and dried at 105 °C to obtain the coconut shell carbon containing C=C double bonds, which was ball milled to 300 mesh.

[0031] 2. Rice husk (1.00 g, 400 mesh), polyethyleneimine (1.00 g), coconut shell carbon containing C=C double bonds (1.00 g), and reduced iron powder (0.50 g) were mixed with 28.00 mL of deionized water and stirred at 600 rpm for 5 min. Subsequently, 10.00 mL of epichlorohydrin was added to initiate the cross-linking reaction until the liquid-solid conversion of the mixture occurred. The obtained solid sample was washed with deionized water until neutral and vacuum freeze-dried to obtain the product, which was a rice husk-based adsorbent material for simultaneous removal and transformation of chromium and arsenic.

[0032] A 0.05 g of the rice husk-based adsorbent material prepared in Example 3 was placed in a beaker containing 50 mL of a chromium-arsenic mixed solution (the concentrations of Cr(VI) and As(III) were 50 mg / L, respectively), and the reaction was carried out on a magnetic stirrer at a speed of 180 rpm under xenon lamp irradiation. Samples were taken every 10 min, 8 mL of the solution was taken using a syringe and filtered using a water filter head with a pore size of 0.22 μm, and the obtained solution was measured for the concentrations of chromium and arsenic using ICP-OES. The concentrations of chromium and arsenic in the samples were both 0 mg / L at 20 min and 60 min, respectively, i.e., the complete removal of chromium and arsenic was achieved. XPS spectra showed that the conversion rates of Cr(VI) and As(III) on the rice husk-based adsorbent material adsorbed with the chromium-arsenic mixed solution were 99.21% and 95.13%, respectively. The material was washed three times with 0.1 M HC1 solution and NaOH solution, respectively, and finally washed with clean water until the pH value was neutral for the recycling regeneration experiment. It was found that the rice husk-based adsorbent material prepared in Example 3 could still achieve a removal rate of chromium and arsenic of more than 90% after five cycles. A 1 g of the rice husk-based adsorbent material prepared in Example 3 was placed in an adsorption column for dynamic adsorption experiment, and the maximum adsorption capacities of the material for Cr(VI) and As(III) were measured to be 332 mg / L and 246 mg / L, respectively.

[0033] Comparative Example 1

[0034] 1. The same as step 1 of Example 1.

[0035] 2. Polyethyleneimine (2.00 g), coconut shell carbon containing C=C double bonds (1.00 g), and reduced iron powder (0.30 g) were mixed with 10.00 mL of deionized water and stirred at 200 rpm for 25 min. Subsequently, 2.00 mL of epichlorohydrin was added to initiate the cross-linking reaction until the liquid-solid conversion of the mixture occurred. The obtained solid sample was washed with deionized water until neutral and vacuum freeze-dried to obtain the product, which was a carbon-based adsorbent material.

[0036] Example 1 was repeated except that 0.05 g of the carbon-based adsorbent material prepared in Comparative Example 1 was used. The sample was taken every 10 min, 8 mL of the solution was taken using a syringe and filtered using a water filter with a pore size of 0.22 μm, and the resulting solution was measured for chromium and arsenic concentrations using ICP-OES. The chromium and arsenic concentrations in the sample were measured to be 0.223 mg / L and 13.926 mg / L at 20 min and 50 min, respectively. The carbon-based adsorbent material of Comparative Example 1 showed poorer removal of chromium and arsenic than that of Example 1. The material was washed three times with 0.1 M HC1 solution and NaOH solution, respectively, and finally washed with clean water until the pH was neutral to perform a recycling experiment. It was found that the removal of chromium and arsenic by the carbon-based adsorbent material of Comparative Example 1 was 85% and 67%, respectively, when it was recycled for the third time, and the performance was significantly decreased compared to that of Example 1.

[0037] Comparative Example 2

[0038] 1. The same as Step 1 of Example 1.

[0039] 2. Eucalyptus wood (0.50 g, 200 mesh), polyethyleneimine (2.00 g), and coconut shell charcoal containing C=C double bonds (1.00 g) were mixed with 10.00 mL of deionized water and stirred at 200 rpm for 25 min. Then, 2.00 mL of epichlorohydrin was added to initiate a cross-linking reaction until the mixture was converted from liquid to solid. The resulting solid sample was washed with deionized water until neutral and vacuum freeze-dried to obtain the product, i.e., a eucalyptus wood-based adsorbent material.

[0040] Example 1 was repeated except that 0.05 g of the carbon-based adsorbent material prepared in Comparative Example 1 was used. The sample was taken every 10 min, 8 mL of the solution was taken using a syringe and filtered using a water filter with a pore size of 0.22 μm, and the resulting solution was measured for chromium and arsenic concentrations using ICP-OES. The chromium and arsenic concentrations in the sample were measured to be 0.223 mg / L and 13.926 mg / L at 20 min and 50 min, respectively. The carbon-based adsorbent material of Comparative Example 1 showed poorer removal of chromium and arsenic than that of Example 1. The material was washed three times with 0.1 M HC1 solution and NaOH solution, respectively, and finally washed with clean water until the pH was neutral to perform a recycling experiment. It was found that the removal of chromium and arsenic by the carbon-based adsorbent material of Comparative Example 1 was 85% and 67%, respectively, when it was recycled for the third time, and the performance was significantly decreased compared to that of Example 1.

Claims

1. A method for preparing a biomass-based adsorption material for simultaneous removal and conversion of chromium and arsenic, characterized in that: Using biomass as a matrix, the amino group of the amine compound, reduced iron powder and coconut shell charcoal containing a C=C double bond are introduced into the biomass matrix through the ring-opening reaction of epichlorohydrin to prepare the chromium and arsenic simultaneous removal-conversion biomass-based adsorption material; The preparation method of coconut shell charcoal containing C=C double bonds comprises: coconut shells are heated under inert atmosphere to The heating rate was raised to 600-900℃ and pyrolysis was carried out for 45-130 min; the pyrolysis products were mixed with The solution was mixed and dried at 80-105 ℃; the dried mixture was mixed with NaOH or KOH and The heating rate is increased to 600-800 °C for secondary pyrolysis, and the pyrolysis time is 60-120 min; the secondary pyrolysis product is washed with water until the pH value is neutral, and then dried at 90-105 °C to obtain coconut shell charcoal containing C=C double bonds, which is then ball-milled to 300 mesh.

2. The preparation method according to claim 1, characterized in that The biomass is eucalyptus, pine, rice husk, straw or peanut shell. The biomass is crushed to 200-400 meshes, cleaned, and then placed in an oven to dry.

3. The preparation method according to claim 1, characterized in that The amine compound is polyethyleneimine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine or polyallylamine.

4. The preparation method according to claim 1, characterized in that The ratio of the added amount of coconut shell, KMnO4 solution, NaOH or KOH is 1.0 g: 0.5-2.5 mL: 0.3-2.0 g, wherein The mass concentration of the solution is 0.3%-4.0%.

5. The preparation method according to claim 1, characterized in that The main operation is: biomass, amine compounds, coconut shell charcoal containing C=C double bonds, reduced iron powder and deionized water are mixed and stirred at 200-600 rpm for 5-25 minutes; then epichlorohydrin is added to initiate a cross-linking reaction until the mixture undergoes liquid-solid conversion; the obtained solid product is washed to neutrality and vacuum freeze-dried to obtain a biomass-based adsorption material with simultaneous chromium and arsenic removal and conversion.

6. The preparation method according to claim 5, characterized in that The addition ratio of the biomass, the amine compound, the coconut shell charcoal containing a C=C double bond, the reduced iron powder, the deionized water and the epichlorohydrin is 1.0 g: 1.0-6.0 g: 1.0-3.0 g: 0.5-1.5 g: 10-28 mL: 3.0-10.0 mL.

7. A chromium and arsenic simultaneous removal-conversion biomass-based adsorption material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of a chromium and arsenic simultaneous removal-conversion biomass-based adsorption material prepared by the preparation method according to any one of claims 1 to 6 in removing chromium and arsenic and reducing their toxicity.

9. The use according to claim 8, characterized in that The chromium and arsenic simultaneous removal-conversion biomass-based adsorption material is placed in heavy metal wastewater containing chromium and arsenic. Under xenon lamp irradiation and stirring conditions, the adsorption material adsorbs hexavalent chromium and trivalent arsenic while converting the hexavalent chromium and trivalent arsenic into less toxic trivalent chromium and pentavalent arsenic respectively.