The Study On Preparation And Removal Performance Of Iron-based Composites For Typical Pharmaceuticals In Water

With the development of medical and health services industry,the production and use of pharmaceuticals are increasingly widespread.Due to the bioaccumulation and difficulty in degradation,a variety of pharmaceuticals have been frequently detected in the aquatic environment with a continuously rising concentration level,posing a potential threat to water ecological environment and human health.Among kinds of water treatment methods,adsorption is widely concerned because of its advantages of simple operation and low cost.At the same time,persulfate advanced oxidation technology with high oxidation activity and environmental adaptability has also been extensively studied in recent years.The transition metal element iron has a wide range of sources and a relatively small impact on the environment.As an adsorbent or catalyst,it has always been a hot spot for researchers.In this study,aiming at the problem of pharmaceuticals pollution in water,and to improve the adsorption and persulfate activation performance of iron and its composites,three kinds of iron-based composites were synthesized.A series of characterization methods and influencing factors experiments were carried to investigate the removal performance and mechanism of iron-based composites on typical pharmaceuticals including fluoroquinolone antibiotics FQs?norfloxacin NOR,ofloxacin OFL?,tetracycline antibiotics TCs?tetracycline TC?and antiepileptic drugs?carbamazepine CBZ?.At the same time,the continuous flow advanced oxidation device was designed to remove TC from water and provide ideas for the treatment of actual contaminated water.Main research contents and results were as follows:?1?Liquid phase reduction method was used to prepare nanoscale zero valent iron?NZVI?and zeolite loaded PEG-4000 modified nano zero valent iron composite?PZ-NZVI?.The characterization results showed PZ-NZVI had mesoporous structure and good magnetism,it can be separated from the solution rapidly under a magnetic field.The adsorption study of NOR and OFL in solution revealed that,compared to NZVI and zeolite,PZ-NZVI had higher adsorption capacity.The maximum adsorption capacity of PZ-NZVI were 54.67 mg g^-1?NOR?and 48.88 mg g^-1?OFL?,respectively.The equilibrium studies were better agreed with pseudo-second-order kinetic model and Temkin isotherm model.The adsorption process was a spontaneous exothermic reaction.NOR/OFL adsorbed by PZ-NZVI could adapt a wide pH range?4¹0?,but it was inhibited under high ion strength.After three cycles,NOR/OFL adsorption efficiency by PZ-NZVI were higher than 50%.The main adsorption mechanisms contained surface complexation,hydrophobic action and pore filling.In real water matrix?Yellow River and secondary effluent from sewage treatment plant?,NOR and OFL adsorption by PZ-NZVI were negatively influenced.?2?Corn cob biochar?BC600?,pyrite modified biochar?PBC200,PBC400 and PBC600?were prepared from corn cob biomass and natural pyrite at different calcination temperatures.The characterizations and experimental results showed that PBC600 had a large degree of graphitization and defects.With magnetic property,PBC600 can be separated from aqueous solution by a magnet.In contrast,PBC600 had a higher PMS activation ability,92.66%CBZ and 40%TOC were removed in 2 h under the optimum conditions.The degradation rate of CBZ in PBC600/PMS system was high with a wide pH range?3⁹?,and almost unaffected by SO₄^2-and NO₃^-.But HCO₃^-and H₂PO₄^-with high concentration had negative impact on CBZ removal.After three cycles,PBC600 still had excellent PMS activation capacity with 87.14%CBZ removal rate.Active species including HO·,SO₄^·-and ¹O₂ were involved in the process of CBZ degradation.Besides,in tap water and Yellow River water,CBZ degradation by PBC600/PMS system was unaffected,but it was negatively influenced in secondary effluent from sewage treatment plant with complex composition.?3?Magnetic iron-carbon gel pellets?Fe-BC@CS?were synthesized via coating zero-valent iron and maize straw biochar with chitosan gel.The Fe-BC@CS filled continuous flow column was used to activate PS for advanced oxidation removal of rhodamine B,and the optimal operating parameters were obtained as:the filled pellets mass was 5.000 g,the concentration of PS was 2 mM and the inflow rate was 5.1 mL min^-1.Under these conditions,after three continuous cycles use of Fe-BC@CS pellets,the removal rate of TC can still reach 74.20%,showing that Fe-BC@CS had good cycling performance.In ultrapure water,Yellow River and sewage effluent,the TC removal rates were 87.77%,85.53%and 80.25%respectively,indicating the practical application potential of the Fe-BC@CS filled continuous flow column device.The active species such as HO·,SO₄^·-and ¹O₂ were generated in Fe-BC@CS pellets/PS system for TC degradation.