Study On Adsorption Of Cadmium Ion In Aqueous Solution On Silica Modified By Polymer Composites

Water pollution as a public problem becoming more and more serious,due to the arbitrary disposal of wastewater form mining,chemical industry,metallurgy,petroleum refining and other industrial sectors.Among them,heavy metal pollution has attracted people's attention because of its non-natural degradation and bioaccumulation.However,the wastewater treatment technology is difficult to meet the growing demand of industrial development,which impels researchers continuously to develop an economic,efficient and green way to treat polluted water.In this study,polyacrylamide and sodium polyacrylate were grafted onto the surface of silica by multi interval ultra-violet initiation polymerization to remove heavy metal cadmium from wastewater.On this basis,the preparation conditions and proportion of the material were optimized,the influence of adsorption conditions was investigated,and the adsorption process and behavior rules were investigated under the optimal conditions.The adsorption mechanism was preliminarily explored in combination with the structural properties and the adsorption behavior of the material.Finally,the cost of materials was evaluated simply,which can provide guidance and comparative indicators for the production and application of the industry,and establish the basis for the industrialization of materials.In this paper,polyacrylamide and sodium polyacrylate were grafted onto silica by multi interval ultra-violet initiation polymerization.Fourier transform infrared spectroscopy,N₂ adsorption-desorption isotherms analysis,X-ray photoelectron spectroscopy,scanning electron microscopy and X-ray energy spectrum were employed to characterize the surface morphology and structure of the material.The concentration of Cd²⁺in the solution was detected by atomic absorption spectrophotometer and the adsorption capacity of material was investigated by the change of concentration.According to a variety of isotherm and kinetic models,the experimental data of adsorption process were fitted and analyzed.The result showed that the polyacrylamide modified silica composites were described with Langmuir isotherm model and pseudo-second-order kinetic model,and the sodium polyacrylate modified silica composites were conform to sips model and pseudo-second-order kinetic model.The adsorption capacity of polyacrylamide and sodium polyacrylate modified silica composites for cadmium in aqueous solution reached 197.63 mg/g and 122.20 mg/g?T=35°C,p H=6.5 and 7?,respectively.Through the investigation of adsorption temperature,the result showed that the adsorption capacity increases with the increase of temperature.Combined with thermodynamic analysis,the adsorption reaction was a spontaneous and endothermic process.In this study,the cost of materials was simply evaluated by improving CCC index,the preparation cost of different types adsorbents was compared,and the cost price of Cd²⁺adsorbed per unit mass was investigated.The results proved that the polyacrylamide modified silica composites have a certain price advantage in application.At last,the adsorption mechanism of materials was explored and analyzed preliminarily.It is found that precipitation complexation and ion exchange are the main adsorption mechanisms of these materials.