Experimental study on adsorption of Cu2+ and Zn2+ in acid mine wastewater by modified lignite

In view of the problems of high content of Cu2+ and Zn2+ in acid mine drainage (AMD),and limited adsorption capacity of lignite,the lignite was used as raw material and pseudomonas aeruginosa was used to modify lignite to prepare microbial modified lignite,so as to explore the adsorption characteristics and adsorption stability of Cu2+ and Zn2+ in AMD.At the same time,the adsorption mechanism of Cu2+ and Zn2+ on lignite and microbially modified lignite was revealed by means of SEM,BET and FTIR.The results show that compared with lignite,the adsorption and removal rates of Cu2+ and Zn2+ by microbial modified lignite were all increased by more than 15%,and the adsorption saturation capacity of microbially modified lignite for Cu2+ and Zn2+ is 22.625 mg/g and 21.825 mg/g,respectively,which were 20.66% and 19.92% higher than that of the original lignite,and the desorption test shows that lignite and modified lignite have high stability in adsorption of metal ions.The adsorption of Cu2+ and Zn2+ by lignite and microbially modified lignite conform to the pseudo-second-order kinetic model,,indicating that the adsorption process is chemical adsorption and mainly ion exchange.The isothermal adsorption line fitting of adsorption Cu2+ and Zn2+ by lignite and modified lignite is more in line with the Langmuir model,and the adsorption conforms to the single-molecule layer adsorption process.From SEM,BET and FTIR tests,it can be seen that the surface structure of lignite modified by Pseudomonas aeruginosa is destroyed,the specific surface area is greatly increased, and some functional groups are dissolved,which leads to the increase of surface pores of lignite.At the same time,the molecular structure of lignite changes,the main chain and branch chains in olefins containing C═C and cyclic hydrocarbons are fractured,and oxygen-containing functional groups such as—CHO and C═O in lignite will decompose,resulting in the production of smaller hydroxyl groups.And the small molecular organics such as alcohol bases,and oxygen-containing functional groups such as —OH and —COOH are greatly increased,the adsorption sites are increased,and the adsorption capacity of lignite is improved.