| Red mud is the solid waste produced in the process of alumina production in Bayer bauxite.At present,it is basically disposed by open storage and has not been used effectively on a large scale,which not only wastes land resources,but also causes environmental pollution.the red mud?RM?was used as raw material and modified by acrylic acid?AA?to obtain red mud/acrylic composite?RM/PAA?.The adsorption properties of lead and cadmium in water and soil were studied and compared between RM and RM/PAA,in order to provide a new approach and theoretical basis for resource utilization of red mud solid waste.The research focuses on three areas:?1?Red mud/polyacrylic acid composite?RM/PAA?was prepared by using red mud as raw material,under the action of coupling agent and initiator,to bridge and polymerize with acrylic acid.The chemical composition,structure and morphology of XRD,FT-IR,XPS,SEM and BET were used to characterize it.The results showed that the coupling agent KH-570 produced two groups of alcoholic hydroxyl and methacrylic groups through hydrolysis,respectively Red mud Si-OH,Al-OH and acrylic monomers undergo hydroxyl dehydration condensation and acrylic acid polymerization,thereby bridging the acrylic polymer on the surface of red mud.The changes in the appearance and morphology of RM/PAA and the decrease in specific surface area,average pore size,and pore volume also further indicate that acrylic acid was successfully grafted onto the surface of red mud.?2?The adsorption behavior of cadmium and lead ions in water by RM and RM/PAA was studied.The results show that the adsorption effect of RM/PAA on Cd???is greatly improved than that of RM.When the amount of adsorbent is 1.25 g·L-1,the p H of the solution is 6,the initial concentration of cadmium ion is 100 mg·L-1 and when the adsorption time reaches 240 min,the adsorption capacity of RM/PAA for Cd???is68.80 mg·g-1,the adsorption rate reaches 86%,which is 3.9 times of RM;the adsorption of RM/PAA for Cd???is The spontaneous endothermic process conforms to the quasi-second-order kinetic model and the Langmuir adsorption isotherm;the adsorption mechanism study shows that there are three adsorption methods of RM/PAA for cadmium:electrostatic interaction,ion exchange and chemical coordination;the study also found that RM has lead ions The adsorption capacity is higher.In contrast,the adsorption effect of RM/PAA on lead ions does not have a significant improvement ability.?3?RM and RM/PAA were used for soil lead and cadmium treatment,and their mechanism of action on lead and cadmium in the soil was inferred through the changes of metal forms in the soil.The effects of the amount of adsorbent added,the p H of the added aqueous solution and the cultivation time on the form of lead and cadmium in the soil were studied.The results showed that when the mass ratio of RM and RM/PAA to the soil sample reached 0.7:10 and the cultivation time reached 45 days,the exchangeable cadmium ions and lead ions in the soil reached equilibrium state,and the p H value of the aqueous solution was added,it has no obvious effect on the morphological changes of cadmium and lead ions in the soil;RM/PAA has a solubilizing effect on both lead and cadmium ions.It mainly converts cadmium ions into organically bound states,while it is converted leads to residue state. |
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