A Study On The Adsorption Of Typical Pollutants In Water By Modified Peanut Shell

Peanut shell(PS)as agricultural byproduct can be developed to remove pollutants from environment.In this study,PS was modified to improve its adsorption capacity toward pollutants for solution.Polyethyleneimine(PEI),FeCl3·6H2O,β-cyclodextrin(β-CD)and citric acid(CA)were selected as modified agents to obtain the adsorbent PEI-PS,Fe-PEI-PS and P-CD-PS,respectively while adsorption properties of hexavalent chromium(Cr(VI)),2,4-dichlorophenoxyacetic acid(2,4-D),lead ions(Pb2+)and bisphenol sulfide(BPS)were performed.Scanning electron microscopy(SEM),infrared spectroscopy(FTIR),elemental analysis,X-ray photoelectron spectroscopy(XPS),etct were used to characterize the adsorbent before and after modification,and the results showed that the three adsorbents were successfully prepared.The results of the adsorption of Cr(VI)by PEI-PS showed that there is in favor of Cr(VI)adsorption at pH 2 while there is not conducive to adsorption with common salts coexisted in solution.The adsorption isotherm conformed to the four models of Langmuir,Freundlich,Temkin and Koble-Corrigan while the adsorption kinetic process conformed to the Pseudo-second-order kinetic model and Elovich model.This adsorption was an exothermic reaction with spontaneous and entropy reduction.Thomas,The Clark and The Yoon-Nelson models can be used to describe the kineitc adsorption process.0.1 moL·L-1 NaCl+0.1 moL·L-1 NaOH can be used as desorption agent.The results of the adsorption of 2,4-D by Fe-PEI-PS indicated that Fe-PEI-PS has a wide range of 2,4-D adsorption within pH 3～8.The presence of salts has a negative effect on the adsorption.The equilibrium results were well predicted by Langmuir model and Koble-Corrigan model while the pseudo-second-order models can describe the kinetic adsorption process.Thermodynamic studies showed that the adsorption process was an exothermic reaction with spontaneous and entropy reduction.The column adsorption process was consistent with Thomas,Yan and The Yoon-Nelson models.0.1 moL·L-1 NaCl can regenerate the spent Fe-PEI-PS multiple times.The results of β-CD-PS adsorption on Pb2+ and BPS showed that acidic conditions were not conducive to the adsorption of Pb2+,and the adsorption of BPS remained basically unchanged within pH 2～7 while alkaline conditions were not in favor of BPS adsorption.The presence of salt had a negative effect on Pb2+ adsorption,but had no effect on BPS adsorption.Langmuir and Koble-Conrigan models showed a high fitting degree for the adsorption process of Pb2+,and the adsorption process of BPS conformed to the Temkin and Koble-Corrigan models.The adsorption process of Pb2+was fitted with Pseudo-first-order and Elovich model,while the BPS adsorption was consistent with the model of Pseudo-second-order kinetic model.Thermodynamic studies showed that the adsorption of Pb2+ was an endothermic reaction with spontaneous and entropy increase.The adsorption of BPS was an exothermic reaction with spontaneous and entropy reduction.Yan model and The Adams-Bohart model can well describe the dynamic adsorption process of Pb2+.The dynamic adsorption process of BPS was fitted with Yan model.The β-CD-PS adsorbed by Pb2+can be regenerated using 0.1 mol·L1HNO3 while75%C2H5OH had a better desorption and regeneration effect on BPSloaded β-CD-PS.The modified peanut shell is promising to effectively remove some pollutants from solution.