Study On Adsorption Of Cadmium Ion On Sepiolite Modified By Manganese And Magnesium Oxides

Today,with the development of industrialization and urbanization,the environmental problems caused by the discharge of heavy metal ions are becoming more and more serious.The current technology is difficult to meet the future development demand for heavy metal ion wastewater treatment,which makes it more and more important to efficiently and economically remove heavy metal ion wastewater discharged from factories.In this paper,the Xiangtan sepiolite was used as the carrier,and two metal oxides,manganese dioxide and magnesium oxide,were loaded on sepiolite by liquid phase redox method and coprecipitation method respectively,for the adsorption of heavy metal ion Cd²⁺in wastewater.On this basis,the influence of preparation and adsorption conditions on the adsorbent was studied,and the structural characteristics of the adsorbent and the adsorption performance of Cd²⁺were investigated.To provide guidance for the actual production and life,develop high value-added products.In this paper,metal oxide?MnO₂,MgO?modified sepiolite was prepared by loading different content of metal oxide on purified and acid-modified sepiolite?MnO₂-sepiolite,MgO-sepiolite?.The physical and chemical characteristics of modified sepiolite before and after modification and after adsorption of Cd²⁺adsorbents were characterized by Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,scanning electron microscope?SEM?,specific surface and pore size analysis,X-ray energy spectrum analysis?EDS?and X-ray photoelectron spectroscopy?XPS?to investigate the adsorbent properties.And the adsorption capacity of the adsorbent was measured by atomic absorption spectrophotometer?AAS?.Three isotherm models and three kinetic models were fitted the adsorption isotherm experimental data and adsorption kinetic data.It was found that the experimental data of MnO₂-sepiolite adsorption of Cd²⁺were consistent with Sips isotherm model and Avrami kinetic model,and the experimental data of MgO-sepiolite adsorption of Cd²⁺were consistent with Sips isotherm model andpseudo-second-kinetic model.When the reaction temperature was 298 K,the adsorption capacity of MnO₂-sepiolite and MgO-sepiolite on Cd²⁺reached 114.7 mg/g and 604.95 mg/g at pH=6 and pH=4,respectively.In addition,the effect of adsorption temperature was investigated,and the thermodynamic analysis showed that the adsorption process of adsorbents on Cd²⁺was spontaneous and endothermic.Further,HCl and EDTA solutions were used to desorbed MnO₂-sepiolite and MgO-sepiolite after adsorption of Cd²⁺to investigated the stability of the adsorbent for recycling.The results showed that the removal efficiency of Cd²⁺was still as high as 90%after four cycles of adsorption-desorption.In order to compare the preparation of cost of adsorbent for adsorbing Cd²⁺,a simple price evaluation scheme was proposed to investigate the price required for adsorbing Cd²⁺per unit weight of adsorbent,and it was found that MnO₂-sepiolite prepared in this paper has a price advantage in this paper.Finally,this paper also analyzed the adsorption mechanism of oxide modified sepiolite on Cd²⁺.It is found that ion exchange,surface complexation and precipitation are the main adsorption mechanisms of Cd²⁺.