Study On Adsorption Of Typical Pollutants In Aquatic System By Modified Magnetic Materials And Chitosan/PVA Films

Magnetic material as adsorbent support offers great simlification on easy adsorbent recovery by eliminating procedures such as centrifugation or filtration.Chitosan?CS?is widely used for adsorption application because of its abundant structural amino and hydroxyl groups.In this study,Zr-PEI@Fe₃O₄was prepared by modifying Fe₃O₄ with polyethyleneimine?PEI?and zirconyl oxychloride?Zr OCl₂·8H₂O?,and its adsorption performance on alizarin red?AR?and phosphate(PO₄^3-)were studied.;CS-PVA membrane was prepared by mixing CS and polyvinyl alcohol?PVA?together,and its adsorption performance for humic acid?HA?was studied;CS-PVA-HA membrane was prepared by coating CS-PVA with HA,and its adsorption performance for heavy metal ion Cu²⁺was studied.These adorbents were characterized by isoelectric point?p Hpzc?,infrared spectrum?FTIR?,scanning electron microscope?SEM?,hysteresis loop?VSM?,specific surface area?BET?,and X-ray photoelectron spectroscopy?XPS?.The main findings are as follows:The experimental results of adsorption of AR and PO₄^3-on Zr-PEI@Fe₃O₄showed that p H of the solution had a large effect on the adsorption of AR and PO₄^3-.At p H=2,the maximum adsorption capacity is 114mg·g^-1for AR,and 32.2 mg·g^-1 for PO₄³,respectively;The isotherm data of AR adsorption on Zr-PEI@Fe₃O₄ are fitted better to the Langmuir model.The kinetic data are fitted closelywith the Elovich equation,which indicates that the adsorption is a complex process involving a single molecular layer and multiple molecular layers.The isotherm data of PO₄^3-adsorption by Zr-PEI@Fe₃O₄ is fitted betterto the Freundlich model.The kinetic process can be described by either the Elovich equation or Double Constant model,which is indicated to be a heterogeneous multi-layer adsorption process.The thermodynamic results show that the adsorption of either AR or PO₄^3-on Zr-PEI@Fe₃O₄is a spontaneous,endothermic,and entropy-increasing process.The mechanisms of these adsorption processes are mainly through electrostatic attraction and complexation.The results of HA adsorption on CS-PVAshow that the optimal p H for HA adsorption on CS-PVA is 6,and the maximum adsorption capacity is 111 mg·g^-1.Both ncreasing and decreasing p H will result a derease of the adsorption capacity.Coexsiting ions increase the adsorption capacity.The adsorption process could be well described by Langmuir model.The kinetic process follows the pseudo-second-order model.The results imply that the adsorption process is a monolayer adsorption on a uniform surface through electrostatic attraction and hydrophobic effect.The calculated thermodynamic parameters indicate that the adsorption of HA by CS-PVA membrane is a spontaneous,exothermic,and entropy-reducing process.The optimal p H for Cu²⁺adsorption by CS-PVA-HA membrane was 5.5.Coexisting ions had a negative effect on the adsorption.The adsorption process could be decribed by the Freundlich model.The Cu²⁺adsorption kinetic by CS-PVA-HA membrane could be described by the Elovich equation,Adsorption mainly relied on complexing forces through analysis of experimental results and XPS.Thermodynamic parameters indicated that adsorption was a spontaneous,endothermic,and entropically increasing chemical adsorption process.Therefore,the developed adsorbents prove to have good adsorption capacities for the Chosen environmental pollutents.And they are promising candidates for the pollutent removal.