收录:
摘要:
This study examined the difference of ammonium adsorption by molecular sieve with different silica-alumina ratios that were determined using x-rays fluorescence (XRF) method. Based on the results from scanning electron microscopy (SEM) and X-ray diffraction (XRF), It was investigated the adsorption mechanism of molecular sieve under different silica-alumina ratio conditions from the perspective of molecular sieve framework, surface morphology, and crystal structure. Meanwhile, the ammonium adsorption improvement through the desilicification of molecular sieve framework was revealed, and this would provide technical reference for the molecular sieve based deep denitrification of sewage treatment plant effluent. The results indicated that molecular sieves with different silica-alumina ratio had significant variation in surface morphology, crystal structure, and ammonium adsorption performance. It was found that the increased silica-alumina ratio was associated with decreased crystallization, increased obscuring of crystal grain shape, and decreased adsorption capacity. When the silica-alumina ratio rose from 35 to 237, the equilibrium adsorption capacity of ammonium by molecular sieve decreased from 5.65mg/g to 0.41mg/g, and the monolayer adsorption saturation capacity confirmed by Langmuir adsorption isotherm decreased from 6.5963mg/g to 0.4430mg/g. The adsorption process conformed to the pseudo-second-order kinetic model, which was revealed that the adsorption rate was controlled by the mechanism of ion-exchange chemical adsorption. Both the ion-exchange capacity of molecular sieve and the rate of adsorption decreased with the increase in silica-alumina ratio. It was observed that the ability of ammonium absorption was significantly improved by desilicification process of molecular sieve framework, and the equilibrium ammonium adsorption with a silica-alumina ratio of 35increased by 81.6% after a desilicification process. This would provide an effective technological approach for improving the ammonium adsorption by molecular sieve. © 2019, Editorial Board of China Environmental Science. All right reserved.
关键词:
通讯作者信息:
电子邮件地址: