Preparation Of Composite Catalyst Particle And Application In Removal Of Color From Printing And Dyeing Wastewater

Using powdered activated carbon, powder alumina and attapulgite as the carriermaterial, copper nitrate as catalyst, the composite catalyst particle was prepared byimpregnation calcinations method. The structure and characterization was determinedby means of FT-IR and SEM.Meanwhile, the composite catalyst particle wascombined with different oxidant to treat acid scarlet which simulated printing anddyeing wastewater, and the degradation mechanism of acid scarlet studied in differentcatalytic oxidation system. On the basis of this study, the composite catalyst particlewas applied to remove color and COD from practical printing and dyeing wastewater.The effects of various operating parameters like initial pH, oxidation time, the dosageof catalyst and oxidant were discussed. Moreover, the regenerability and reutilizationof the composite particle catalyst were studied.Through the above experiments, the achievements were as follows:1. Ratio of raw materials of the composite particles is determined by orthogonalexperiment: attapulgite: powdered activated carbon: powder alumina is10:2:1. Thesingle factor experiment confirms the optimum conditions which are catalystconcentration of0.8mol/L, calcination temperature of600℃, calcination time of2.5h.2. Acid Brilliant Scarlet is used as simulated printing and dyeing wastewater. Indifferent catalyst–oxidant system, different degradation mechanisms have been got: Inthe hydrogen peroxide system, hydrogen peroxide is catalyzed and generated strongoxidant hydroxyl radicals by composite particle. Then-N=N-of Acid Brilliant Scarletis attacked by hydroxyl radicals. Through chemical reaction, organic moleculescontinue to degrade,–C-C-,-C=C-and benzene are ruptured to small molecules.However, in the ozone system, two oxidants exist, hydroxyl radicals are generated byozone, which attack–N=N-first. Then,-C-C-,-C-N-and benzene are oxidized tosmall molecules because hydroxyl radicals and ozone are synergy. Nitrogen is mainlyconverted to nitrogen gas.3. In the catalyst-hydrogen peroxide system,when the reaction temperature was60℃,the initial pH was6, the oxidant dosage was80mL/L，the catalyst was40g/L, the reaction time was60min, the color and COD of practical printing and dyeingwastewater removal rate could amount to95%and82%, respectively. When theparticle catalyst is used for ten times, COD removal rate reduced to64%, but the colorstill has high removal efficiency.In the catalyst-ozone system, when the initial pH was9, the catalyst was40g/L,the oxidant dosage was55mg/L, the reaction time was50min, the color and COD ofpractical printing and dyeing wastewater removal rate could amount to95%and60%,respectively. When the particle catalyst is used for ten times, COD removal ratereduced to59%, which still has high catalytic effect.4. Apparent kinetics model were established in different oxidant system. In thecatalyst-hydrogen peroxide system, the apparent kinetics equation of heterogeneouscatalytic oxidation isV=dc/dt=0.936E^0.16 F^0.425.The results show that reactionrate increases positively with the dosage of catalyst and hydrogen peroxide, In thecatalyst-ozone system, the apparent kinetics equation of heterogeneous catalyticoxidation isV=dc/dt=3.18E^0.215F^0.131.The rate increases positively with the dosageof catalyst and ozone concentration.