Preparation Of Manganese Oxide Modified Porous Materials And Their Application In The Treatment Of Phenolic Wastewater

Porous materials are widely used in the conventional and deep treatment of water due to their relatively large specific surface area and strong adsorption capacity,especially for the removal of organic pollutants in water.However,it is not good for the treatment of wastewater containing high concentration organic pollutants due to their physical adsorption,which easily leads to saturation of adsorption and considerable solid waste.In this thesis,based on the principle of catalytic oxidation in advanced oxidation technology,two novel,efficient,inexpensive and recyclable catalysts for degradation of organic pollutant wastewater were prepared by using the porous materials with large specific surface area and strong adsorption performance-manganese oxide modified molecular sieve and manganese oxide modified activated carbon.These two catalysts have strong catalytic degradation ability for phenolic wastewater and can be widely used in the purification of various organic pollutant wastewater.The main research work is as follows:?1?Preparation of Manganese Oxide Modified Molecular Sieve and its application in the treatment of Phenolic WastewaterWith 4A molecular sieve as the carrier and sodium hypochlorite as the oxidant,the environmentally friendly manganese oxide modified molecular sieve material was prepared by in situ oxidation of manganese sulfate on the surface of molecular sieve.The preparation conditions of material?the mass ratio of molecular sieve to manganese sulfate,the p H value of the reaction system,and the molar ratio of manganese sulfate to sodium hypochlorite?were optimized.The optimum preparation conditions of manganese oxide modified molecular sieve were obtained at the mass ratio of molecular sieve to manganese sulfate,the p H value of the reaction system,and the molar ratio of manganese sulfate to sodium hypochlorite of 7:1,7.2,and 1:2.5,respectively.The materials were characterized by field emission scanning electron microscopy?FE-SEM?and X-ray diffraction?XRD?.XRD analysis showed that manganese was present in the form of manganese oxides.The as-prepared manganese oxides existed as different forms under different p H conditions.The manganese oxide had the highest valence state when the reaction p H was 7.2,mainly in the form of MnO₂.The test showed that the higher the valence of manganese in manganese oxides,the better the treatment effect of phenolic wastewater was.The oxidative degradation of phenol-containing wastewater by hydrogen peroxide was studied using manganese oxide modified molecular sieve as catalyst under the optimum preparation conditions.The effects of different systems,wastewater temperature,pH value of wastewater,and the amount of hydrogen peroxide on the degradation of phenol were investigated.The results showed that under the optimum degradation conditions of wastewater,phenol was almost not degraded within 120 min if only hydrogen peroxide was added and the removal rate of phenol by the unmodified molecular sieve was only 35%,while that of phenol by manganese oxide modified molecular sieve was 82%,indicating that the oxidative degradation performance of phenol by manganese oxide modified molecular sieve was greatly improved.?2?Preparation of Manganese Oxide Modified Activated carbon and its application in the treatment of Phenolic WastewaterManganese oxide modified activated carbon?MnO_x@AC?was prepared by in situ oxidation of manganese sulfate on the surface of activated carbon?AC?with sodium hypochlorite as oxidant.The effects of the mass ratio of AC to manganese sulfate,the p H value of the reaction system,and the molar ratio of manganese sulfate to sodium hypochlorite on the amount of MnO_X supported on AC and the catalytic oxidation degradation of phenol were investigated.The results showed that when the mass ratio of AC to manganese sulfate was 10:1,the pH value of the reaction system was 7.4,and the molar ratio of manganese sulfate to sodium hypochlorite was 1:2.5,the performance of the as-prepared MnO_X@AC in the catalytic oxidation of phenol was the best.The materials were characterized by field emission scanning electron microscopy?FE-SEM?,X-ray diffraction?XRD?,Brunauer-Emmet-Teller?BET?,and X-ray energy spectrum?XPS?.BET analysis showed that the specific surface area of AC decreased from 489.4m²g^-1 to 302.8m²g^-1 because MnO_X was loaded on the surface of activated carbon.XPS analysis showed that the valence states of manganese in manganese oxides were different under different p H conditions.The BE difference was 4.81 e V when the p H was 7.4,indicating that the valence of manganese was + 4.Tests showed that the higher the valence of manganese in manganese oxides,the better the treatment effect of phenolic wastewater was.The oxidative degradation of phenol-containing wastewater by hydrogen peroxide was studied using MnO_X@AC as catalyst under the optimum preparation conditions.The effects of different systems,wastewater temperature,p H value of wastewater,and the amount of hydrogen peroxide on the degradation of phenol were investigated.The results showed that under the optimum degradation conditions of wastewater,phenol was almost not degraded within 120 min if only hydrogen peroxide was added and the removal rate of phenol by the unmodified AC was only 42%,while that of phenol by MnO_X@AC was 91%,indicating that the oxidative degradation performance of phenol by MnO_X@AC was greatly improved.