Study On Preparation Of Activated Red Mud Adsorption Material And Adsorption Properties For Pb(Ⅱ) And Zn(Ⅱ)

Red mud is an industrial solid waste generated in the process of alumina refining.The continuous development of alumina industry and the reduction of bauxite grade leads to the increase of red mud production,thus it is particularly necessary to dispose red mud reasonably.In recent years,with the continuous progress of industrialization,a large number of heavy metal ions have entered the natural environment,resulting in serious environmental pollution.In this study,the activated red mud adsorption material(NCRM)was prepared by neutralization-calcination activation process for the remediation of heavy metal contaminated water.This study aimed to determine the preparation conditions of activated red mud through comparing with the adsorption capacity of Pb(Ⅱ)and Zn(Ⅱ),and the preparation process was optimized by factorial experimental design and response surface methodology.The adsorption properties and mechanism of NCRM for Pb(Ⅱ)and Zn(Ⅱ)in single component system and binary system were studied in detail.The research contents and conclusions were as follows:The factorial experimental design and response surface methodology indicated that neutralization time,calcination temperature,and time were the main affecting factors.The prepared NCRM had the best adsorption performance for Pb(Ⅱ)and Zn(Ⅱ)at the solution concentration of 1.5mol/L,the liquid-solid ratio of 48,the neutralization time of 114 min,calcination temperature of 518 ℃,and the calcination time of 148 min.The material characterization results showed that the surface and structure of NCRM was rougher and looser,and had larger specific surface area and pore volume compared with the original red mud.The results of single-component system and binary system adsorption experiments indicated that the optimal operating conditions in the singlecomponent system were as follows: the dosage was 2.5 g/L,the solution p H was 5.0,the initial concentrations of Pb(II)and Zn(II)were 600 and500 mg/L,the adsorption time was 240 min,and the temperature was 328 K.The maximum adsorption capacities of Pb(Ⅱ)and Zn(Ⅱ)were 218.82 and 75.58 mg/g,respectively.When the dosage was 2.5 g/L,the p H was5.0,the adsorption time was 240 min,and the temperature was 328 K.,the maximum adsorption capacity of NCRM for Pb(II)and Zn(II)decreased to 197.18 and 52.38 mg/g in the binary system,and NCRM showed higher adsorption selectivity for Pb(II).The adsorption stability study showed that NCRM was still a general solid waste after adsorption and can be used for other aspects.Besides,the actual wastewater treatment indicated that NCRM can effectively remove Pb(II)and Zn(II)from water.The fitting results of adsorption isotherm indicated that the adsorption behavior of Pb(II)and Zn(II)in NCRM can be explained by Langmuir model,which revealed that the adsorption of NCRM for Pb(II)and Zn(II)was endothermic monolayer chemical adsorption.Moreover,the kinetic analysis showed that the adsorption process of NCRM for Pb(II)and Zn(II)in single-component and binary system could be explained by pseudo-second order kinetics,which further indicated that the chemical adsorption was the main adsorption process.