Preparation And Adsorption Properties Of Ethylenedimine-grafted Silica Gel Material

Industrial wastewater often contains a lot of heavy metal ions which cause serious harm to the environment and organisms.The solid phase chelating material with amino used for treating heavy metal with low concentrations in wastewater can recycle precious metal effectively, and it has significance in environmental protection. The content of this study is composed of preparing a cheap ethylenediamine-grafted silica gel adsorption material which is promising in the recovery of heavy metal ions, investigating the synthesis conditions of CPTCS-SiO2 and EDA/SiO2, studying the substitution reaction of silica sueface and discussing the adsorption process of heavy metal ions on material.Silica gel was surface-modified with y-chloropropyltrichlorosilane (CPTCS),the higher stability of silanized silica gel CPTCS-SiO2 was prepared.The effect of interaction between hydration capacity and CPTCS dosage, time, solvent volume on alkylation reaction were researched by orthogonal experiment.The alkylation reaction conditions were optimized based on the orthogonal experiment via single-factor experiment. And characterized the performance of CPTCS-SiO2·The experiment results show that the effect of hydration capacity and CPTCS dosage on alkylation reaction are conspicuous.The better mass ratio of water and CPTCS is 1:11.78. With the increasing of organic content in silica gel surface, the wettability of methanol on CPTCS-SiO2 is better.Alkali stability of CPTCS-SiO2 prepared by adding water with hydrate form is the best.The ethylenediamine-grafted silica gel (EDA/SiO2) was prepared by CPTCS as surface anchor and ethylenediamine as surface modification agent. The effects of temperature, time and ethylenediamine concentration on the substitution reaction of ethylenediamine with CPTCS-SiO2 were investigated in detail. And it was obtained that the optimal conditions were reaction temperature 333K, reaction time 16h, and n(ethylenediamine):n(chlorine on the surface of CPTCS-SiO2) more than 9. The substitution reaction kinetics of ethylenediamine with CPTCS-SiO2 were also investigated. It was obtained that the parameters of the apparent kinetic model were reaction order 4.37, activation energy 55.44KJ·mol-1 and frequency factor 5.06×107h-1 by the kinetics data fitted with the differentiation and minimum variance linear regression.Studied the adsorption features of EDA/SiO2 on Cu2+,Pb2+,Zn2+. The experiment results show that pH value of solution affects adsorption capacity of EDA/SiO2 significantly, the best pH value of Cu2+,Pb2+,Zn2+ adsorption range are 3.5-4.5,3.5-4.0,3.0-6.0. The adsorption equilibrium data on Cu2+,Pb2+,Zn2+ is in accordance with Langmuir model, the results show that this adsorption process is endothermic adsorption,the temperature adding process is conducive to adsorption by calculating the adsorption enthalpy, free energy and adsorption entropy, and adsorption behavior of this process was explained reasonably. Adsorption kinetic data can be described by the pseudo-second-order kinetic equation,and the fitting adsorption kinetic constants are related with the solution concentration.By using 0.1mol·L-1 hydrochloric acid as eluent, the absorbed Cu2+ ions are eluted easily from EDA/SiO2, and the adsorption capacity of EDA/SiO2 is stable after 5 times of use.