The Study Of Hydroxyl Basic Salts As Catalysts For Degrading Phenolic Wastewater

Phenol and its derivatives are broadly applied in petrochemical, chemical, pharmaceutical, oil refineries, dyes and plastics industries as raw materials, resulting in contaminants in effluent inevitably. The treatment of phenolic wastewater is necessary before discharging it directly, due to the haard to human health and aquatic life. There are many methods to deal with phenolic wastewater, but biological treatment is only effective at a low phenol concentration or need long time because of the biorefractory and toxic phenolic compounds. Some physical technologies, such as adsorption and membrane separation, are only suitable for wastewater of higher concentration. Catalytic wet peroxide oxidation (CWPO) of chemical technologies which can eventually oxidie organic pollutants to water, carbon dioxide, and other small molecules under mild condition, are the common alternatives for medium wastewater treatment, especially for refractory pollutants.The heterogeneous Fenton catalysts are strictly controlled pH=3.5 to degrade effluent in CWPO. The degradation of phenol solutions by some copper-containing catalysts is not excellent or the copper ions in the solutions after treatment are too many to be treated again. A few copper hydroxyl salts are reported to oxidie organic wastewater and the effect is excellent. These copper hydroxyl salts are simple to be prepared and stable. In addition, the condition of treatment is mild and they perform well.Based on the above viewpoints, catalytic wet peroxide oxidation (CWPO) and copper hydroxyl sulfates are employed to degrade phenolic wastewater in this work. Phenol is select as a model compound in wastewater, and the effect of temperature, hydrogen peroxide dosage, initial pH and catalyst dosage initial pH by Cu4(OH)6SO4-A is investigated. Excellent results, phenol removal efficiency of 99% after 10 min and COD removal efficiency of 97% after 180 min, have been achieved when treating 150 mL 100 mg/L phenol wastewater under the optimal condition (50℃, pH=6.88,0.13 g/L Cu4(OH)6SO4-A,2.5 times of theoretical H2O2).Cu4(OH)6SO4-A, Cu4(OH)6SO4-B and Cu3(OH)4SO4 which synthesied by three hydrothermal methods have different pore diameters. The structure-activity relationship of the catalysts is investigated by degrading phenol, methyl orange and acid orange II wastewater at the same conditions and characterizing the structure of them. It is found that pore diameter of the catalysts with low specific area is bigger than that of traditional catalyst and the sie of the organics. The bigger pores decrease the diffusion control of organics to the catalytic active, hence the hydroxyl radicals can oxidie organics fast. As the sie of organic increases, the difference of catalytic activity between three catalysts increases. And the pores of catalyst are bigger, the catalytic activity is higher.The catalysts from wastewater after centrifugation are reused. It was shown that copper hydroxyl sulfates after three consecutive runs still have catalytic activity, even though the COD removal efficiency in the third run is lower.