| Coal gasification slag is a kind of solid waste,which occupied a large amount of land resources and polluted the environment.Comprehensive utilization of high value-added resources is an effective way to solve this problem.In this paper,the coal gasification slag has a large specific surface area and contains a large amount of residual carbon and silicon.The raw coal gasification slag(GS)was modified to improve its the adsorption performance and applied to wastewater treatment.Firstly,the raw coal gasification slag was modified by acid leaching and microwave treatment methods to obtain acid leaching modified coal gasification slag(A-GS),microwave modified coal gasification slag(M-GS)and microwave modified coal gasification slag followed by acid leaching(M-GS-A).In order to overcome the shortcomings that the modified coal gasification slag was easy to agglomerate and not easy to separate,the modified coal gasification slag was mixed with chitosan,and then the chitosan was modified to obtain the modified chitosan/coal gasification slag composite material(P-CS/M-GS-A).The adsorbents were characterized and analyzed by XRD,FTIR,SEM,BET,Raman and Zeta potential,and they applied to adsorb methyl orange MO and Cr(?)from astewater,and further to explored the adsorption mechanism.The main contents were as follows:(1)Modified the coal gasification slag by microwave technology with a power of 600W,a time of 10min and a temperature of 60? was to obtain microwave modified coal gasification slag(M-GS).The acid leaching modified coal gasification slag(A-GS)was obtained through 20wt%hydrochloric acid solution and the ratio of the volume of hydrochloric acid to the mass of coal gasification slag is 4:1 under temperature was 90? after 8 hours.The M-GS modified by the acid leaching process to be prepared microwave modified coal gasification slag followed by acid leaching(M-GS-A).M-GS-A was based on microwave treatment to make macropores,and then acid leaching to make small pores on the walls of the macropores,which made M-GS-A has more pores structure.The specific surface area of M-GS-A was 343.06 m2/g,which was 2.3 times to the specific surface area of GS.(2)The maximum adsorption capacity of GS,A-GS,M-GS and M-GS-A for MO were 90.90,113.63,100.45 and 125.23 mg/g respectively,and the maximum adsorption capacity for Cr(?)were 4.94,6.98,5.87 and 8.70 mg/g respectively.The adsorption process of M-GS-A on MO and Cr(?)were more in line with the Langmuir adsorption isotherm.The ?H and AG were both negative,which indicating that the adsorption process was a monolayer adsorption and the spontaneous exothermic reaction.(3)Using glutaraldehyde as cross-linking agent,through cross-linking method and freeze-drying method,the optional mass ratio of chitosan,polyethyleneimine and M-GS-A was 1:3:1 have prepared the modified Chitosan/coal gasification slag composite material.The modified chitosan/coal gasification slag composite material has good dispersibility in aqueous solution,and was easy to separate.It has more pores structures and functional groups such as-NH2,-NH,-OH and-COOH.(4)The maximum adsorption capacity of P-CS and P-CS/M-GS-A for MO were 441.26 and 462.91 mg/g respectively,and the maximum adsorption capacity for Cr(?)were 131.23 and 143.45 mg/g respectively.The adsorption process of P-CS/M-GS-A on MO and Cr(?)were more in line with the pseudo second-order kinetic model.The adsorption process of MO and Cr(?)were followed the Langmuir adsorption isotherm model well.The AH and AG were both negative value,which indicating that the adsorption process was both monolayer adsorption and the spontaneous exothermic reaction.In addition to physical adsorption,modified chitosan/coal gasification slag composites may also remove the pollutants by electrostatic attraction,hydrogen bonding,and ? and ? stacking.After 3 times of desorption and regeneration,the adsorbents still maintain high adsorption performance. |
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