Research On Poss-modified Mesoporous And Removing Amonion Nitrogen In Drinking Water

This study is dedicated to synthesis POSS-modified mesoporous molecular sieves to improve the efficiency of ammonia-nitrogen removal from drinking water.Based on tetraethoxysilane and P125 template, the original SBA-15 molecular sieve was synthesized using hydrothermal crystallization method. The POSS modifiers, (Me₄N)₈(OSiO_1.58 (OSA) and (SHC₃H₆)₈(OSiO_1.5)₈, were prepared using rice husk ash and (3-mercaptopropyl)trimethoxysilane, respectively, through the sol-gel process, and further POSS-COOH and POSS-SO₃H modified SBA-15 molecular sievesThe SBA-15 molecular sieves before and after the modifications were characterized by standard techniques: mass spectrometry (MS), infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), small angle XRD and nitrogen sorption porosimetry (NSP). The MS spectra shown narrow molecular distributions for the three molecular sieves, and the FT-IR spectra shown the corresponding groups before and after the modifications; the small-angle XRD peaks and TEM images represente micro-pore structures of the three SBA-15 molecular sieves; SEM images give clearly the changes of particle surface morphology (particle size and shape) before and after the modifications; NSP measurement determined the morphology of the SBA-15 molecular sieves before and after the modification, giving surface areas, pore diameters and pore volumes quantitively. Comparing with those of original SBA-15 molecular sieve, the pore diameters and pore volumes of the POSS-COOH modified SBA-15 molecular sieve increased but the surface area decreased; for the POSS-SO₃H modified SBA-15 molecular sieve, all those decreased. Above facts conclude that the POSS-modified SBA-15 molecular sieve can be made and increased in active groups to remove ammonia-nitrogen from drinking water.The influence of adsorption time, adsorption temperature and ammonia-nittrogen concentration on adsorption capacity and removal efficiency was investigated. The results shown that the longer adsorption time, the higher adsorption temperature, and higher initial concentration can lead to greater adsorption capacity and adsorption rate. Also, the experimental data shown that the two kinds of POSS-modified SBA-15 molecular sieves had greater ammonia-removing efficiency.The mentioned increase tendency was validated using a molecular dynamic simulation program of the Materials Stutio software to calculate the diffusion behavior of ammonia-nitrogen in the pores of three SBA-15 molecular sieve, and to compare transition–state energy of the ammonia-nitrogen removal reaction in the SBA-15 molecular sieve before and after modification.