Study On Preparation And Application Of Heterogeneous Catalysts In Degradation Of Ciprofloxacin Wastewater

With the development of medical science and technology and wide application of antibiotic at home,the output of pharmaceutical wastewater(especially the antibiotic wastewater)has increased dramatically in our country,resulting in increasing the harm to human body and ecological environment.In view of the characteristics of antibiotic wastewater,such as great change of water quality,complex composition and high COD value,it is difficult to remove antibiotics in wastewater effectively with the existing treatment technologies.In this paper,ciprofloxacin(CIP)was selected as one of typical antibiotics and two new kinds of heterogeneous Fenton-like catalysts were prepared for the removal of ciprofloxacin in aqueous solution based on the traditional Fenton oxidation technology and previous reseaches.In this paper,activated alumina-supported manganese and sodium alginate(SA)gel beads catalysts were prepared by dipping-sintering and polymerization methods,respectively.The study of effects of preparation conditions and operating conditions of Fenton reaction on degradation of CIP was conducted by single factor analysis method.The activated alumina-supported manganese catalyst was characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The catalytic performance of the activated alumina-supported manganese catalyst sintered in nitrogen is better than that sintered in air.Compared with iron,copper and nickel,activated alumina-supported manganese catalystshows the highest catalytic activity.In addition,the preparation conditions,such as dipping time,concentration of dipping solution,sintering temperature,sintering time and manganese salt type,are of great influnences on catalytic activity of prepared heterogeneous catalysts.The optimal preparation conditions of catalyst were determined by single factor analysis method:the activated alumina was first dipped in 0.3 mol·L-1 nitric acid manganese solution for 8 h and then sintered at 600? by programing heating for 2 h.SA gel beads catalyst was characterized by SEM and thermal gravity analysis(TGA).The mechanical property of SA gel beads catalyst prepared with dual metal ions as crosslinking agent is stronger than that prepared with only iron ion as crosslinking agent.Moreover,effects of preparation conditions,such as concentration of iron ion,mass fraction of SA and polymerization temperature,on catalytic performances of prepared SA gel beads catalyst were investigated.The optimal preparation conditions of catalyst was determined by single factor analysis method:2%SA solution was added into 0.1 mol·L-1 ferric chloride solution for polymerization at 30?.Effects of operating conditions on catalytic performances of two kinds of heterogeneous catalysts were studied too.The catalytic performance of both prepared catalysts in alkaline solution is better than that in acid solution.The catalytic activity of both prepared catalysts increases with the increase of additive amounts of catalyst and H2O2.The relationship between initial concentration of CIP and degradation rate fits a second-order kinetic relationship.The relationships between pH,additive amounts of catalyst and H2O2 and degradation rate fit first-order kinetic relationship.Furthermore,seven kinds of degradation intermediate products were determined by LC-MS based on the catalytic mechanism and theory of electron cloud density.Finally,a possible degradation pathway was proposed,which could be used for reference and guidance for theory research on Fenton-like system in the future.