Study On Adsorption Mechanism Of Typical Heavy Metals In Mine Wastewater By Modified Biochar Supported Iron Floc

This research used a wide range of low-cost rice straw and iron floc produced from the treatment of mining wastewater as raw materials.They combined by chemical modification to load the iron floc on biochar.Two kinds of modified biochar adsorption materials?A and B?were prepared by the combined method of ultraviolet and ultraviolet radiation.The materials were characterized by SEM,FTIR,BET,ZETA and other different characterization methods,this paper researched the adsorption performance of elements?Pb,Zn,Sb and As?and the adsorption mechanism with the modified biochar.It can provide environmentally compatible adsorbent for the prevention and control of heavy metals in mining wastewater,and enabled the iron floc to be recycled.By studying its adsorption mechanism,it can provide some theoretical guidance to develop more heavy metal adsorption materials for mining wastewater,the main results of the research are as follow;Modified material A was prepared by chemical modification-ultraviolet radiation using iron floc and rice straw as substrates,and the prepared materials were screened by orthogonal experiments.The optimal preparation conditions were screened as follows:the amount of CS₂ was 1m L,the amount of Zn SO₄·7H₂O was 2m L,and the amount of Na OH was 8m L.Based on material A,the material preparation process was further optimized and optimized,and a magnetic modified material B was prepared from the same raw materials.The conditions for preparing magnetic material B are;HCL and Na OH are both acid-base modified at a liquid-solid ratio of 10:1?m L:g?,and then a 2 mol·L^-1Na OH solution is used at a liquid-solid ratio of 10:1?m L:g?mixed with biochar in a 250m L Erlenmeyer flask,stirred for 90 minutes,washed with water,dried and combined with the ratio of Fe?III?:Fe?II?to hydrochloric acid and modified materials,and added 3 m L of a 10%Mg Cl₂ solution was used to adjust the system p H 8 with Na OH solution,ultrasonically stirred for 1 h,and irradiated with ultraviolet rays for 2 h,separated and washed until the supernatant was neutral,and dried to obtain the final magnetic material B.The adsorption amount of modified material A on Pb?II?gradually increased with the increase of p H,and the adsorption effect was the best under the condition of p H7,the maximum actual adsorption amount of Pb?II?was 247.3mg·L^-1.The Langmuir equation and the second-order kinetic equation can described this process well.The adsorption of material A belongs to single-molecule chemical adsorption,which is combined with Pb?II?through complexation and chelation.The specific surface area of material A increased significantly,many oxygen-containing functional groups were added to the surface,and the xanthate and ferrite groups were successfully supported on the material.The adsorption amount of the four elements of Pb,Zn,Sb and As has a significant increase compared with the unmodified material B.The actual adsorption amounts are292.2mg·g^-1,103.67mg·g^-1,5.21 mg·g^-1and 6.85 mg·g^-1.In the mixed system,the increase of Pb?II?concentration will seriously inhibit the adsorption of Zn?II?by the material Pb?II?has a stronger binding force than Zn?II?;As has a better competitive advantage than Sb and can react with material B more quickly.Regeneration experiments show that the effective regeneration capacity of material B for Pb?II?and Zn?II?is significantly stronger than Sb and AS.The former has three effective regeneration times,and the latter has only one or two times.Under low concentration conditions,material B has a good fixing effect on Pb?II?and Zn?II?,which provides some theoretical support for the treatment of lead and zinc wastewater discharged from lead-zinc smelting and other industrial production.