The Preparation Of Layered Double Oxide Ozone Catalyst And Application For The Aniline Wastewater Treatment

Layered double hydroxide(LDH)is a kind of new type synthetic clay material which is composed of two or more positively charged main layers and interlayer anions through non-covalent interactions assembled.Layered double oxide(LDO)is calcined from LDH.In recent years,LDO have a wide range of application as ozone catalyst because of their typical characteristics such as high transition metal content,big specific surface area,even distribution of catalytic active sites and good thermal stability.In this study,a series of layered double hydroxides were prepared by co-precipitation,and then the preparation of layered double oxides by calcination methods.The prepared samples were characterized and fully ananlyzed.Effect of preparation factors for layered double oxides catalytic ozone oxidation of aniline wastewater were investigated systematically.Degradation kinetics of aniline in different catalytic systems were also determined.The main contents are as follows:(1)Binary iron-based layered double hydroxide and binary aluminum-based layered double hydroxide were prepared by forward / reverse co-precipitation method.Effect of preparation factors for layered double oxides catalytic ozone oxidation of aniline wastewater were investigated systematically.The calcination temperature of LDO prepared by LDH was determined by thermal analysis.The study showed that the materials had the greatest influence on the catalytic effect.Co2+ was more suitable for catalytic ozone oxidation of aniline wastewater.The optimal preparation conditions were set as p H 12,temperature 60?,cobalt-iron ratio 3:1 for Co/Fe-LDH,and p H 12,temperature 70?,cobalt-aluminum ratio 3:1 for Co/Al-LDH.The catalytic effect of Co/Fe-LDO and Co/Al-LDO prepared by reverse co-precipitation method is better than that of forward co-precipitation method.TG-DTG analysis showed that Co/Fe-LDO and Co/Al-LDO had the greatest catalytic activity at400-500? of calcination temperature.(2)Physicochemical properties of the as-prepared Co/Fe-LDO and Co/Al-LDO ozone catalysts were evaluated according to the XRD,SEM and BET analysis.TheXRD showed that the main phase of the two catalysts was based on Co3O4.The SEM showed that the obvious layered structure and rough surface in the two kinds of layered double oxides ozone catalysts.BET implies that the two catalysts belonged to mesoporous pore size materials and appeared IV adsorption and desorption isotherms.(3)The degradation of aniline wastewater by ozone with Co/Fe-LDO and Co/Al-LDO catalysts at different reaction temperatures were compared with that by ozone oxidation aniline wastewater.The reaction kinetics of Co/Fe-LDO and Co/Al-LDO ozone catalysts for the degradation of aniline wastewater in catalysts/ozone systems were established.Aniline oxidized by ozone or catalyst/ozone systems were both based on the first-order reactions.Co/Al-LDO and Co/Fe-LDO catalysts can reduce the reaction activation energy for CODCr degradation by 23.25 k J·mol-1and 16.61 k J·mol-1 and the eaction activation energy for TOC degradation by15.03 k J·mol-1and 22.12 k J·mol-1.(4)The ternary LDO catalysts were prepared on the binary LDO catalysts by doping metal elements.The results showed that the effect of Calcium doping on Co/Fe-LDO and Zinc doping on Co/Al-LDO catalysts on the degradation of aniline wastewater was the best.Co-Ca/Fe-LDO and Co-Zn/Al-LDO catalysts can reduce the reaction activation energy for CODCr degradation by 29.19 k J·mol-1 and 23.64 k J·mol-1.