Research On The Purification Effect Of Modified Zeolites Substrates Coated With LDHs In The Simulated Vertical-flow Constructed Wetlands

According to the research of purification effect on zeolite substrates modified with layered double hydroxides(LDHs) in the simulated vertical-flow constructed wetlands(VFCWs), LDHs-modified zeolites were employed for the removal of organics 、 nitrogen 、 phosphorus in wastewater which were collected from Shahu Sewage Treatment Plant(Wuhan, China) after the thin grill. The modification and purification experiments were conducted for a whole year. Base on the analysis of purification effect for the main pollutants, there provided a scientific basis for the selection of substrates, the methods of modification and the research of purification mechanisms on LDHs modified zeolites.In this study, the experiments consist of two parts which were the modification of zeolites and the purification of sewage by the simulate VFCWs system. The main results were as follows: 1. Based on the surface characteristics of LDHs crystals and the compositions of original zeolites, the modified zeolites were observed by Scanning Electron Microscope(SEM) and X-Ray Fluorescence Spectrometer(XRFS).It demonstrated that the LDHs coating on the zeolites were successfully; 2. The results of organics, nitrogen and phosphorus purification experiments indicated that the removal effect of modified zeolites on phosphorus was best; 3. The removal mechanisms of the organics were chemical and biological adsorption; the removal mechanisms of nitrogen were micro-biological nitrification and denitrification; the removal mechanisms of phosphorus were physical interception, microbe adsorption and ion exchange; 4. The comprehensive purification effect of the three particle size of zeolites was in the following order: Small>Medium>Large; 5. The purification effects of diffident pollutants by 9 kinds of LDHs modified zeolites were varied. The optimal type for the removal of organics is the middle-partical-size zoelites coated with Co Ca-LDHs; the optimal selection for the removal of total nitrogen is the small-partical-size zoelites coated with Fe Mg-LDHs and the large-partical-size zoelites coated with Co Ca-LDHs; the optimal selection for the removal of ammonianitrogen is the zoelites in small-particle-size modified with Fe Mg-LDHs and the zoelites in large-partical-size covered with Al Ca-LDHs; the optimal type for the removal of total phosphorus is the small-partical-size zeolites with Fe Zn-LDHs; the best type of LDHs for the removal of phosphate is which contains Zn2+. So we can choose different zeolites with different particle size and modified with different LDHs to adjust to different wastewater for the best purification results.