Study On Adsorption And Catalytic Oxidation Degradation Of Tetracycline By Hydrous Ferric Oxide And Its Modified Materials

Tetracycline（TC）is a typical antibiotic which mainly forms a reversible combination with the ribosome of the bacterial to inhibit protein synthesis.Tetracycline is widely used as a feed additive in animal husbandry and aquaculture for the function of prevention of diseases and promotion of animal growth in animals.However,30%-90%of antibiotics are excreted with feces and urine in the form of parent becaused of its low absorptivity,which leads to the pollution of antibiotics in soil and water and causes potential ecologically risk.Adsorption and advanced oxidative degradation are common methods which have been applied to remove tetracycline from wastewater.However,monometallic iron compounds catalysts are limited in practical application because of its low catalytic activity,poor stability and recyclability.Recently,much effort has been exerted to improve the practical applications of heterogeneous catalysts.Bimetallic oxides（composite oxides of iron and another metal element）has become a research hotspot.In this study,hydrous ferric oxide（HFO）and its cobalt modified materials was synthesized.The adsorption and catalytic oxidation behavior of tetracycline by HFO and its composite were system studied.The results can provide a theoretical basis and technical support for the removal of tetracycline in wastewater.The main results are as follows.1.HFO and its modified materials were synthesized and were characterized by BET,XRD,TGA and particle size distribution analysis.The HFO contains crystal water but poor crystallinity,and belongs to amorphous iron.The largest adsorption amount of tetracycline onto HFO was at p H 7.Present of K⁺ions had little effect on TC adsorption by HFO.The removal rate of TC decreased from 96.50%to 17.18%and from 96.50%to 27.13%,respectively,with the concentrations of Ca²⁺and Mg²⁺increased from 0 to 0.5 mol/L.Pseudo-second-order adsorption kinetics and Langmuir adsorption isotherm fitted the adsorption process well,which indicates that the adsorption of tetracycline by HFO is controlled by chemical interaction and monolayer adsorption.2.The degradation efficiency of TC is 97%and the K_obs is 9.4×10^-3 min^-1 under the conditions H₂O₂ concentration 5 mmol/L,reaction time 450 min,temperature 25°C and HFO dosage 0.4 g/L.Present of Na⁺,Ca²⁺,NO₃^-and SO₄^2-had little effect on degradation of TC in HFO/H₂O₂ system.However,Mg²⁺and HCO₃^-decreased the degradation of TC in HFO/H₂O₂2 system.The inhibitory effect became more obviously with the increasing concentrations of Mg²⁺and HCO₃^-.Free radical·O₂^-was found the dominant ROS promoting TC degradation in the HFO/H₂O₂ system.3.CoOOH@HFO-0.1 was the most sable catalyst maferial with favourable TC degradation effect.The degradation efficiency was 99%at the PMS concentration 80 mg/L,p H 9 and dosage 0.4 g/L.Present of NO₃^-had little effect on degradation of TC in CoOOH@HFO-0.1/PMS system.However,the present of Cl^-decreased the degradation of TC in CoOOH@HFO-0.1/PMS system,as well as HCO₃^-and H₂PO₄^-.The degradation of TC in CoOOH@HFO-0.1/PMS system decreased with the concentrations of EDTA.However,low concentration of o-phenanthroline did not show inhibitory effect to TC,and exhibited significantly inhibitory effect at high o-phenanthroline concentration to TC tetracycline.The dominant degradation of TC in CoOOH@HFO-0.1/PMS system were caused by ¹O₂ and electron transfer.