The Adsorption Of Aquatic Lead And Cadmium By Chestnut Inner Shell

In this article, chestnut inner shell was investigated as a absorbent of removing heavymetal Pb2+and Cd2+in aqueous solution. Different factors such as temperature, time, pH ofsolution, initial concentration and absorbent dose was studied. The optimum adsorptionconditions were obtained through response surface analysis method. In addition,modifiedchestnut inner shells and irradiation were used in adsorption in order to improve removalrate in acid solution. The active groups of adsorption were explored by the method ofFTIR. Collecting water samples from several places and using chestnut inner shells toremoval Pb2+and Cd2+of them.The results show that:(1)The influence of solution pH on adsorption was more than other factors and whenthe solution pH was under3the removal rate was very low. The best adsorption conditionsof Pb2+through response surface analysis method were: temperature54.16℃, time6.50h,pH5.59. And the best adsorption conditions of Cd2+are: temperature54.15℃, time7.00h,pH5.73. The best removal rate of Pb2+and Cd2+were98.32%and98.67%, the bestadsorption capacity were41.18mg/g and29.98mg/g. The adsorption process of Cd2+fitLangmuir model and fit Freundlich model.Both of them fit Second order kinetic modelvery well.(2)The maleic acid treated chestnut inner shells and the method of irradiationimproved the removal rate in the acid solution of pH=2, the best removal rate was from28.59%to85.84%. FTIR shows that there were o lot of active groups on the surface ofchestnut inner shells which had major effect for the adsorption.(3)The removal rate of Pb2+and Cd2+were improved through the method of irradiationin acid solution of pH=2, when the irradition dose was6kGy, the removal rate of Pb2+andCd2+were from28.59%and28.41%to67.58%and65.33%. In addition, the removal rateof Pb2+can be96.81%through irradiation and chestnut inner shells adsorption, it wasnearly to the heating and chestnut inner shells adsorption.(4)The EDTA and citric acid in the solution may influence the adsorption of Pb2+andCd2+, and the effect of EDTA was greater than the effect of citric acid. The removal rate ofPb2+and Cd2+may reduce from98.32%and98.67%to3.52%and1.92%when there wasEDTA in the solution and the removal rate of Pb2+and Cd2+may reduce from98.32%and98.67%to33.26%and29.43%when there was citric acid in the solution. When Pb2+andCd2+were both in the solution, Pb2+may be first adsorbed by chestnut inner shells. Mg2+、Na+and Ca2+in the solution may compete with Pb2+and Cd2+and influence the adsorption. The water samples were mostly alkaline and the concentration of heavy metal was low.Chestnut inner shells had different adsorption effect to Pb2+and Cd2+in the water samplesand the method of irradiation can improved removal rate. The best removal rate of Pb2+andCd2+can be improved from83.10%and42.73%to93.35%and76.82%, the most canimprove135.66%and156.75%than before irradiation.(5)A small number of Pb2+and Cd2+may generate precipitation with pigment ofchestnut inner shells. The method of irradiation can improved removal rate of Pb2+andCd2+by discolored chestnut inner shells.