Removal Of Aqueous Oxytetracycline By Zero Valent Iron

Oxytetracycline was one member of the tetracycline families found in the 1940s,which is a broad-spectrum antimicrobial agent,also a kind of growth-promoter,often used as feed additives.However,in recent years,high level of oxytetracycline has been detected in water and soils accompanied by the increase of drug-resistant strains,especially in large-scale livestock and poultry wastewaters,which might raise risks of health to human health and other biology.In 2007,one proposal on the "863" project guidances for resources and the environment field was about the treatment technology of antibiotics and heavy metals in intensive farming wastewaters,and the main aims is to get a removal rate higher than 80%for the antibiotics and heavy metals.In other words,it is of great significance to remove oxytetracycline from wastewaters from intensive animal feeding operations using inexpensive, effective and environment friendly techniques.Zero-valent iron has been used to get rid of pollutants like heavy metals,halogenated organics,pesticides,dyes and other pollutants from wastewaters.Mechanisms of adsorption, complexation,reduction and precipition were suggested.Currently,there is a lack of report on the study of oxytetracycline treatment by zero-valent iron,and little is known about the mechanism.Moreover,it seemed that there are some possiblilities for zero valent iron to remove heavy metals and antibiotics simultaneously from wastewaters regarding to the previous studies.In this study,batch tests were performed to investigate the surface reactions of oxytetracycline on zero valent iron.Functions of time,zero-valent iron dose,temperature,pH value,inorganic anions,cations,organic anions and DOMs from livestock manure were examined.The results showed that rather good removal rate(＞90%) of oxytetracycline by zero-valent iron can be obtained.The temperature showed little effect on the reactions.The removal rate of oxytetracycline was better at lower pH value.The removal of oxytetracycline was suppressed by cations like Mg²⁺,Zn²⁺,Ca²⁺ and anions such as H₂PO₄,CO₃^2-,EDTA^2- to different degree.In order to elucidate the mechanisms,a series of test and characterization were conducted including desorption of oxytetracycline,release of iron ion,scanning electron microscopy analysis,energy dispersive x ray fluorescence analysis.The results revealed that adsorption and chemical precipitation mechanism are involved during the reaction processes.