Efficiency Of Tetracycline And Ciprofloxacin Removal From Water By Polyaluminum Chloride Coupled With Potassium Ferrate

Antibiotics are widely used in human medical treatment and livestock breeding because of their good bacteriostatic and bactericidal properties.However,antibiotics cannot be completely absorbed by human body or animal body and enter water bodies.Antibiotics in water bodies are difficult to degrade under natural conditions,which poses a potential threat to ecosystem security and human health.Tetracycline and ciprofloxacin are two typical antibiotics.The removal of tetracycline and ciprofloxacin from waste water has become a research hotspot in the field of water treatment.The removal of tetracycline and ciprofloxacin from water by polyaluminum chloride coagulation has limitations such as low efficiency and large sludge production.Potassium ferrate is a new type of green water treatment agent.Potassium ferrate can effectively degrade a variety of organic matter.The research found that polyaluminum chloride couple with potassium ferrate could effectively remove organic matter,heavy metal,algae and other pollutants.However,the removal of tetracycline and ciprofloxacin from water by polyaluminum chloride couple with potassium ferrate has not been reported.Based on these,the removal of tetracycline and ciprofloxacin from water by polyaluminum chloride couple with potassium ferrate was studied.The effects of dosage,pH,ionic strength(sodium chloride),alkalinity(carbonic acid),common coexisting ions(calcium ion,sulfate,siliceat,phosphate)and humic acid(HA)on the removal efficiency of tetracycline and ciprofloxacin were investigated.The removal mechanism of tetracycline and ciprofloxacin from water by polyaluminum chloride couple with potassium ferrate was investigated.The study on the removal of tetracycline from water showed that the dosage of 10mg/L potassium ferrate and 20 mg/L polyaluminum chloride was the optimal ratio.The use of polyaluminum chloride coupled with potassium ferrate coagulation was effective for the removal of 0.05 m M tetracycline,with an optimal pH of 7 and a removal rate of77%.Under acidic conditions,the highest removal rate of tetracycline was 58%,while under alkaline conditions,the highest removal rate of tetracycline was only 38%.The study revealed that ionic strength had no significant effect on the removal effect of tetracycline.However,alkalinity could affect the removal rate of tetracycline under alkaline conditions.Furthermore,the presence of sulfate did not show any significant impact on the removal of tetracycline.The presence of calcium ion,phosphate,and humic acid could affect the removal rate of tetracycline at pH 5～9,while the presence of siliceat could affect the removal rate of tetracycline at neutral and alkaline conditions.The study on the removal of ciprofloxacin from water showed that the combination of 10 mg/L potassium ferrate and 50 mg/L polyaluminum chloride was the optimal ratio.The removal efficiency of 2 mg/L ciprofloxacin reached 67% at the optimal pH of 7.Under acidic conditions,the highest removal rate of ciprofloxacin was 61%,while under alkaline conditions,the highest removal rate of ciprofloxacin was only 42%.It was found that ionic strength did not have any effect on the removal of ciprofloxacin.alkalinity influenced the removal rate of ciprofloxacin under acidic conditions.Furthermore,the presence of calcium ion affected the removal rate of ciprofloxacin at pH 5,and 10 m M calcium ion could also hinder the removal rate of ciprofloxacin under neutral and alkaline conditions.In addition,1 m M sulfate did not affect the removal of ciprofloxacin,5 m M sulfate could reduce the removal rate of ciprofloxacin at pH 5～9.Siliceat and phosphate also affected the removal rate of ciprofloxacin at pH 5～9.The presence of humic acid influenced the removal rate of ciprofloxacin at pH 5,and 5 mg/L humic acid could also hinder the removal rate of ciprofloxacin under alkaline conditions.The removal mechanism of tetracycline and ciprofloxacin by polyaluminum chloride coupled with potassium ferrate was the combination of oxidation with coagulation.There were three main reaction paths for tetracycline oxidation by potassium ferrate,and the main oxidation group was the six-membered ring connected with the N atom.There were three main reaction paths for the oxidation of ciprofloxacin by potassium ferrate,and the main oxidation group was piperazine ring.Tetracycline and ciprofloxacin were oxidized and degraded to form intermediates with smaller molecular weights.These intermediates were then removed by flocculation with large specific surface area and abundant void structure.This study provided an effective method for the removal of tetracycline and ciprofloxacin in waste water.