阅读说明：本技术 一种生物炭负载纳米铁镍复合材料去除水中六价铬方法 (Method for removing hexavalent chromium in water by using charcoal-loaded nano iron-nickel composite material ) 是由 李士凤 孙洪刚 姚淑华 臧淑艳 于 2019-11-06 设计创作，主要内容包括：一种生物炭负载纳米铁镍复合材料去除水中六价铬方法,涉及一种水体中重金属污染修复方法,本发明将简化生物炭负载型双金属材料制备过程以及避免使用高成本的强还原剂,一步制备生物炭负载纳米零价铁镍双金属复合材料并应用于水中Cr(VI)的去除,解决纳米零价铁在处理水体重金属过程中存在表面易钝化,反应活性低,利用率低的问题。本发明具有成本低,操作简单,无二次污染的优点,生物炭负载铁镍双金属材料去除Cr(VI)的活性高和稳定性均要高于生物炭负载纳米零价铁材料。(The invention discloses a method for removing hexavalent chromium in water by a biochar loaded nano iron-nickel composite material, and relates to a method for restoring heavy metal pollution in water. The method has the advantages of low cost, simple operation and no secondary pollution, and the biochar loaded iron-nickel bimetallic material has high activity and stability for removing Cr (VI) which are higher than those of the biochar loaded nano zero-valent iron material.)

1. A method for removing hexavalent chromium in water by using a charcoal-loaded nano iron-nickel composite material is characterized by comprising the following steps:

(1) drying biomass such as corn straw, wheat straw, rice hull or bagasse, pulverizing with a pulverizer, and sieving with a 50-100 mesh sieve;

(2) ferric nitrate, ferric trichloride, ferric sulfate, ferrous chloride and ferrous sulfate are used as ferric salts, nickel nitrate, nickel sulfate or nickel chloride is used as nickel salt, and a ferric-nickel mixed salt solution is prepared according to the molar ratio of iron to nickel of 3:1-20: 1;

(3) soaking 10-40g of biomass powder in an iron-nickel mixed salt solution, performing ultrasonic treatment for 30-60min, and drying in an oven at 80-100 ℃ for 24-48 h to obtain iron-nickel impregnated biomass powder;

(4) placing the obtained iron-nickel impregnated biomass powder in a tubular furnace, heating the biomass powder to 700-800 ℃ at the speed of 3-5 ℃/min under the condition of continuously introducing inert gas or nitrogen into the tubular furnace;

keeping the temperature for 2-4 hours, and naturally cooling to room temperature; preparing a biochar loaded nano iron-nickel bimetallic composite material;

(5) preparing 10-100mg/L Cr (VI) solution, adjusting the pH value to 6.0, adding a biochar loaded nano iron-nickel bimetallic composite material into the solution, wherein the adding amount is 0.5-1.5/L, and placing the solution into a shaking table to shake at the temperature of 25 ℃ at 150 r/min; the reaction time is 60min, the time is counted after the reaction is started, 1mL of sample is sampled at the interval of 10min, the sample is filtered by a 0.45 mu m filter membrane, and the content of Cr (VI) is measured by an ultraviolet spectrophotometer.

2. The method for removing hexavalent chromium in water by using the biochar-loaded nano iron-nickel composite material as claimed in claim 1, wherein the composite material is prepared by directly pyrolyzing biomass and mixed iron-nickel salt.

3. The method for removing hexavalent chromium in water by using the biochar-loaded nano iron-nickel composite material as claimed in claim 1, wherein the iron salt is ferric nitrate, ferric trichloride, ferric sulfate, ferrous chloride or ferrous sulfate, and the nickel salt is nickel nitrate, nickel sulfate or nickel chloride.

4. The method for removing hexavalent chromium in water by using the biochar-loaded nano iron-nickel composite material according to claim 1, wherein the biomass raw material is one of corn stalks, wheat stalks, rice hulls and bagasse.

Technical Field

The invention relates to a method for restoring heavy metal pollution in a water body, in particular to a method for removing hexavalent chromium in water by a charcoal-loaded nano iron-nickel composite material.

Background

In recent years, with the continuous acceleration of the industrialization process, the water body environment pollution, especially the heavy metal pollution situation, is increasingly severe, and the health and the survival of human beings are obviously threatened. The situation of chromium pollution in industrial discharged wastewater is particularly serious, the total discharge amount of heavy metal pollutants represented by chromium is still in a high level due to the rapid expansion of heavy metal industries, and the potential safety hazard of heavy metal enterprises is still prominent. The forms of chromium in industrial discharge wastewater are mainly Cr (VI) and Cr (III), wherein the Cr (VI) has higher toxicity and mobility.

The existing method for removing hexavalent chromium in wastewater mainly comprises the following steps: adsorption, membrane separation, ion exchange, co-precipitation, reduction. The nanometer zero-valent iron (nZVI) has the characteristics of large specific surface area, strong reducibility, high reactivity, capability of repairing various environmental pollutants and the like, and becomes a very active material in the field of current environmental pollution repairing research. Research shows that the removal of Cr (VI) in water by using nZVI is more than that of adding S₂O₄ ^2-、SO₃ ^2-And Fe²⁺And the like have obvious advantages. Puls et al first used zero-valent iron material, sand, aquifer sediment as the filling medium for PRB to repair the underground water body of Cr (VI), and after five years of treatment, the amount of dissolved Cr was reduced to 0.01 mg/L. Meanwhile, zero-valent iron is easy to coalesce and harden, so that the reaction efficiency is sharply reduced. Therefore, zero-valent iron is often supported on a porous carrier in order to solve the problem of agglomeration thereof. The common carrier is active carbon, biochar, montmorillonite, kaolin, bentonite, zeolite, etc. Shi et al used bentonite-supported stabilized nano Fe to treat Cr (VI) in wastewater, and found that bentonite can effectively reduce the agglomeration of nano zero-valent iron particles and increase the specific surface area of the system. Hoch et al used a carbon-supported nano zero-valent iron system to treat cr (vi) in water. The carbon-stable nano zero-valent iron is prepared by immersing carbon black in an iron-containing solution to load Fe ions and calcining at high temperature. When the Fe/C ratio in the system is 10:3, the system can reduce 10ppm of Cr (VI) to less than 1ppm within three days. However, in the treatment process of Cr (VI) wastewater, the nano zero-valent iron has the surface which is easy to form an oxide film passivation layer, so that the continuous occurrence of reduction reaction is hindered, and the utilization efficiency of the nano zero-valent iron is reduced.

In order to solve the above problems, a bimetallic system is formed by loading another metal or metals (such as nickel, copper and the like) with high reduction potential on the surface of zero-valent iron by chemical precipitation, electroplating and the likeHas proven to be an effective method. The metals with high reduction potential such as nickel, copper and the like play a role of a catalyst in the reaction, so that the reaction activity of the zero-valent iron is improved, the surface area and the porosity of the zero-valent iron are increased, and more surface reaction sites are provided for removing Cr (VI) reaction. However, the existing research mainly adopts a liquid phase reduction method to prepare load type nano iron-nickel and other bimetallic materials, and most of the load type nano iron-nickel and other bimetallic materials use NaBH₄And hydrazine hydrate and other strong reducing agents, and the preparation process is complex and high in cost.

Disclosure of Invention

The invention aims to provide a method for removing hexavalent chromium in water by using a biochar loaded nano iron-nickel composite material, which utilizes biochar generated by biomass pyrolysis and CO and H contained₂The cracking gas reduces ferric iron and nickel, and the biochar loaded nano zero-valent iron-nickel bimetallic composite material is prepared in one step. The method has the characteristics of low cost, simple operation, no secondary pollution, high activity of the iron-nickel bimetal, and good stability and dispersibility.

The purpose of the invention is realized by the following technical scheme:

a method for removing hexavalent chromium in water by using a charcoal-loaded nano iron-nickel composite material comprises the following steps:

(1) drying biomass such as corn straw, wheat straw, rice hull or bagasse, pulverizing with a pulverizer, and sieving with a 50-100 mesh sieve;

(2) ferric nitrate, ferric trichloride, ferric sulfate, ferrous chloride and ferrous sulfate are used as ferric salts, nickel nitrate, nickel sulfate or nickel chloride is used as nickel salt, and a ferric-nickel mixed salt solution is prepared according to the molar ratio of iron to nickel of 3:1-20: 1;

(3) soaking 10-40g of biomass powder in an iron-nickel mixed salt solution, performing ultrasonic treatment for 30-60min, and drying in an oven at 80-100 ℃ for 24-48 h to obtain iron-nickel impregnated biomass powder;

(4) the obtained iron-nickel impregnated biomass powder is placed in a tubular furnace, and the temperature is raised at the speed of 3-5 ℃/min and heated to 700-800 ℃ under the condition of continuously introducing inert gas or nitrogen into the tubular furnace. Keeping the temperature for 2-4 hours, and naturally cooling to room temperature; preparing a biochar loaded nano iron-nickel bimetallic composite material;

(5) preparing 10-100mg/L Cr (VI) solution, adjusting the pH value to 6.0, adding a biochar loaded nano iron-nickel bimetallic composite material into the solution, wherein the adding amount is 0.5-1.5/L, and placing the solution into a shaking table to shake at the temperature of 25 ℃ at 150 r/min; the reaction time is 60min, the time is counted after the reaction is started, 1mL of sample is sampled at the interval of 10min, the sample is filtered by a 0.45 mu m filter membrane, and the content of Cr (VI) is measured by an ultraviolet spectrophotometer.

The method for removing hexavalent chromium in water by using the biochar loaded nano iron-nickel composite material is characterized in that the composite material is prepared by directly pyrolyzing biomass and iron-nickel mixed salt.

The method for removing hexavalent chromium in water by using the biochar loaded nano iron-nickel composite material is characterized in that the ferric salt is ferric nitrate, ferric trichloride, ferric sulfate, ferrous chloride or ferrous sulfate, and the nickel salt is nickel nitrate, nickel sulfate or nickel chloride.

The method for removing hexavalent chromium in water by using the biochar loaded nano iron-nickel composite material is characterized in that the biomass raw material is one of corn straw, wheat straw, rice hull and bagasse.

The invention has the advantages and effects that:

(1) in the process of preparing the biochar, the biochar produced by biomass pyrolysis and the biochar containing CO and H₂The cracking gas reduces ferric iron and nickel, and the biochar loaded nano zero-valent iron-nickel bimetallic composite material is prepared in one step. Compared with other chemical reduction methods, the method has the advantages of low cost, simple operation, no secondary pollution, high activity of the iron-nickel bimetal, and good stability and dispersibility.

(2) The biochar loaded nano zero-valent iron-nickel bimetallic composite material has good performance of removing Cr (VI) in water and good reusability. When the adding amount of the biochar loaded nano zero-valent iron-nickel bimetallic composite material is 1.2g/L, the removal rate of Cr (VI) reaches 99.3 percent.

Drawings

FIG. 1 is an XRD spectrogram of a biochar-loaded nano-nickel-iron bimetallic composite material prepared by the invention;

FIG. 2 is a diagram showing the effect of the biochar loaded bimetal composite material with different ferronickel ratios on the removal of Cr (VI);

fig. 3 is a diagram of the reuse performance of the biochar loaded nano-nickel-iron bimetal composite material prepared by the invention for removing Cr (VI).

Detailed Description

The present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 is an XRD spectrogram of the biochar loaded nano ferronickel bimetallic composite material prepared by the method, wherein 2 theta =26.64 degrees is SiO in the biochar₂A diffraction peak of (a);

FIG. 2 shows the removal effect of the prepared biochar loaded bimetallic composite material with different ferronickel ratios on Cr (VI), wherein the removal rate of the bimetallic composite material Cr (VI) with different ferronickel ratios is higher than that of the biochar loaded nano zero-valent iron under the same condition;

fig. 3 shows that the biochar loaded nano-nickel-iron bimetal composite material prepared by the invention has the repeated use performance of removing Cr (VI), and after the biochar loaded nano-nickel-iron bimetal composite material is repeatedly used for three times, the removal rate of Cr (VI) is still more than 99%, and the biochar loaded nano-nickel-iron bimetal composite material has good repeated use performance.

Example one:

(1) drying corn stalks, crushing by a crusher, and sieving by a 50-100 mesh sieve;

(2) taking 8.1g Fe (NO)₃)₃‧9H₂O and 0.3, 0.6, 1.5g Ni (NO) were weighed out separately₃)₂‧6H₂And O, dissolving in 100mL of water to prepare mixed salt solutions with three different iron-nickel molar ratios.

(3) And respectively soaking 10g of corn straw powder in the three iron-nickel mixed salt solutions, performing ultrasonic treatment for 40min, and drying in an oven at 80 ℃ for 48 hours to obtain the biomass powder soaked in different iron-nickel molar ratios.

(4) And (3) placing the three types of iron-nickel impregnated biomass powder in a tubular furnace, and heating to 800 ℃ at a speed of 5 ℃/min under the condition of continuously introducing nitrogen into the tubular furnace. The temperature was maintained for 2 hours and the mixture was allowed to cool to room temperature. Three kinds of biological carbon loaded nano iron-nickel bimetal composite materials are prepared.

The product obtained by this method with a molar ratio of iron to nickel of 10:1 had the following characteristics:

referring to FIG. 1, an XRD spectrum of a composite material with a molar ratio of Fe to Ni of 10:1 is shown.

0.12g of three biochar-loaded nano iron-nickel bimetallic composite materials are respectively taken, placed in 100mL of 10mg/L Cr (VI) solution with the pH =6.0, and placed in a shaking table to shake at 150r/min, and the temperature is 25 ℃. The reaction time is 60min, timing is carried out after the reaction is started, 1mL of sample is sampled at the interval of 10min, the sample is filtered by a filter membrane of 0.45 mu m, the content of Cr (VI) is measured by an ultraviolet spectrophotometer, and the effect of the biochar loaded nano iron-nickel bimetal composite material on removing hexavalent chromium is shown in figure 2.

Example two:

(1) drying bagasse, pulverizing, and sieving with 50-100 mesh sieve;

(2) 16.2g of Fe (NO) are taken₃)₃‧₉H₂O and 1.2g Ni (NO)₃)₂‧6H₂Dissolving O in 100mL of water to prepare an iron-nickel mixed salt solution.

(3) And (3) soaking 20g of bagasse powder in the iron-nickel mixed salt solution, performing ultrasonic treatment for 60min, and drying in an oven at 100 ℃ for 48 hours to obtain iron-nickel impregnated biomass powder.

(4) And (3) placing the obtained iron-nickel impregnated biomass powder in a tubular furnace, heating the biomass powder to 760 ℃ at the speed of 3 ℃/min under the condition of continuously introducing nitrogen into the tubular furnace. The temperature was maintained for 2 hours and the mixture was allowed to cool to room temperature. The biochar loaded nano iron-nickel bimetallic composite material is prepared.

Taking 0.12g of the prepared biochar loaded nano iron-nickel bimetal composite material, placing the biochar loaded nano iron-nickel bimetal composite material in 100mL of 10mg/L Cr (VI) solution with the pH =6.0, and placing the solution in a shaking table to shake at 150r/min, wherein the temperature is 25 ℃. The reaction time is 60min, the time is counted after the reaction is started, 1mL of sample is sampled at the interval of 10min, the sample is filtered by a filter membrane with the diameter of 0.45 mu m, the content of Cr (VI) is measured by an ultraviolet spectrophotometer, and the removal rate of Cr (VI) is measured after 60min and is 99.3 percent. And (3) separating the composite material from the solution by centrifugation, placing the composite material in 0.5mol/L NaOH solution for regeneration, and placing the regenerated composite material in hexavalent chromium solution for reuse. The performance of the biochar loaded nano iron-nickel bimetal composite material repeatedly applied to removing hexavalent chromium is shown in figure 3.