Meso-porous Carbon Loaded TiO₂ Degrading Wastewater From Waste Mineral Oil Production

The wastewater from the re-processing of waste mineral-oil was mainly generated in the flash-dehydration step.The effective treatment of wastewater is a major issue which limits this waste mineral-oil processing route,due to its complex compositions,high COD value,difficult biochemical-degradation,high toxicity and serious damage to environment.Here,the main pollutant components of wastewater were first analyzed,which are composed of organic ammonia salts,sulfonates and high polyether compounds,etc.Afterwards,some attempts such as flocculation and sedimentation,extraction,rectification,adsorption,and micro-electrolysis have been explored to treat this wastewater.However,it was found that the only use of each method was ineffective.Based on our early research in photocatalytic degrading organics,carbon supported titanium oxide bi-functional catalyst was used to photo-degrade this wastewater.The detailed contents are described as followsThe carbon-supported titanium oxide composite was first prepared by a sol-gel method.The photocatalyst with superior activity was obtained by optimizing the composition ratio?i.e.the mass ratio of meso-porous carbon?MPC?:butyl titanate:absolute ethanol:glacial acetic acid:distilled water is5:9:35:3:5?and the calcination temperature?540 ^oC?.The resultant catalysts were characterized by means of XRD,SEM and N₂ adsorption-desorption measurement,etc.The corresponding result indicates that the active component in this catalyst is anatase-structured titanium dioxide.Moreover,most TiO₂ entered the pores of MPC,and only a small amount of TiO₂ was uniformly distributed on the support surface.The specific surface area of MPC was decreased from 578 to 382m²·g^-1after loading TiO₂.In addition,the performance of TiO₂/MPC for photocatalytic degrading wastewater was evaluated.The pre-treating process together with degradation in the presence of hydrogen peroxide and ozone was proved to be the best method for treating this wastewater.It is worth noting that when the pH value in reaction system is 5-8,this catalyst(24g·L^-1)exhibits a COD degradation rate of 88%under the irradiation of ultraviolet lamp?300 W?at 120 min.However,this value was increased to 91.8%at 90 min with the introduction of hydrogen peroxide?8wt%?and ozone(0.3m³·h^-1).So,a combinative process involving flocculation sedimentation pretreatment,photocatalytic degradation and final biochemical treatment was expected to effectively treat the sewage effluent.