Preparation Of Amidoxime Functionalized Malodorous Siliica And Adsorb Uranium、Lead From Aqueous Solution

Uranium ions in wastewater are radioactive and can generate internal radiation if entering human body, posing serious hazards to human health. If children drink water containing too much Pb, their health and intelligence development will be seriously affected though the water is not radioactive. Therefore, it is urgent to seek an efficient method for treating uranium and lead-bearing wastewater. At present, most researches focus on the adsorption method for treatment of uranium and lead-bearing wastewater. In this study, silica material was used as the carrier which underwent chemical modifications, so as to discuss its performance and mechanism in adsorbing uranium and lead ions.Through functional modification, amidoxime group and rigid organic groups(ethane) with excellent selectivity over uranium were introduced into the silica material to synthesize amidoxime- functionalized ethane-bridged mesoporous silica(AO-PMOs). A static adsorption experiment was performed to investigate the influence of such factors as p H value, initial solution and adsorbent dosage on the uranium and lead adsorption performance of AO-PMOs; also, the adsorption process was analyzed by fitting adsorption isotherm model and kinetic model; infrared spectroscopy and scanning electron microscope were used to analyze the groups and morp Hology of the material before and after adsorption, so as to investigate its adsorption mechanism.The experimental results showed that:(1) The p H value suitable for AOPMOs to adsorb uranium in water solution was within the range of 5-7, and the best adsorption performance was achieved when p H = 5. The adsorption rate was very high during the first 10 min of the adsorption process and gradually became stable after 30 min. When adsorption equilibrium was achieved, the highest uranium removal rate reached over 99%. The uranium ion adsorption capacity was seldom affected by the initial solution, and the material could basically adsorb uranium-bearing solutions of various concentrations.(2)Through analysis by fitting the isothermal adsorption model, it was found that the process of uranium adsorption with AO-PMOs could be described with the Langmuir model. The Langmuir adsorption capacity was 151.98mg/g and 153.84mg/g respectively at 30 ℃and 40℃, suggesting that temperature raise could help adsorption; the adsorption process involved endothermic reaction, focusing on monolayer adsorption. The results of kinetic fitting showed that the process of uranium adsorption with AO-PMOs followed the second-order kinetic model, and uranium ion adsorption with the material was mainly the coordination between amidoxime group and uranium.(3) The optimum p H value for AO-PMOs to adsorb lead was 6.0. When adsorption equilibrium was achieved 60 min after the start of adsorption, the highest lead removal rate reached over 80%. The process of lead adsorption with the material followed the Freundlich isotherm model, suggesting that multilayer adsorption was focused. The pseudo-second-order kinetic model could be used to describe the process of lead adsorption. Through analysis of infrared spectrograms before and after lead adsorption with the material, it could be seen that amidoxime group played a major role in lead adsorption which mainly involved chemical adsorption.