Study on Catalytic Ozonation of Modified Silicate Ore to Remove Antibiotic Pollutants in Water

Author:Luo Li Sha

Supervisor:zou dong lei


Degree Year:2019





With the continuous improvement of people’s living standards and the rapid development of the pharmaceutical industry,the pollution of antibiotics in aquatic environment becomes increasingly serious,and threatens the ecosystem balance and human health.The antibiotics are difficult to be efficiently removed by conventional water treatment processes.Heterogeneous catalytic ozonation has a broad application prospect for the removal of antibiotic pollutants considering its high oxidation efficiency,easy separation of catalysts,simple process and low water treatment cost.How to improve the catalytic activity and processing effect of the catalysts is the focus of current scholars,and furthermore the systematic study of the mechanism of heterogeneous catalytic ozonation for antibiotics removal from water is very important to effectively control the pollution of antibiotic compounds.In view of the above problems,this paper developed a modified silicate ore catalyst with high activity,and investigated the effectiveness and mechanism of catalytic ozonation of modified silicate ore for degrading three kinds of typical antibiotic pollutants with high detection frequency in water.In this paper,a kind of natural light porous silicate ore was selected as the carrier and a variety of metal modified silicate ore catalysts was successfully prepared by wet dipping method.By comparing the catalytic ozonation degradation efficiency of ciprofloxacin(CIP),tetracycline hydrochloride(TCH)and sulfamethoxazole(SMX),the catalysts of higher activity were selected.The catalysts were manganese modified silicate ore(MnSO),cobalt modified silicate ore(CoSO)and iron modified silicate ore(FeSO),and their preparation conditions were optimized.The physical structure and chemical properties of the catalysts were characterized by SEM-EDS,XRD,XPS,BET,FT-IR and Zeta potential.The characterization results showed that the modified silicate ores had good crystal structure,large specific surface area and abundant pore structure,the metal oxides formed were dispersed evenly on silicate ores,and the density of hydroxyl group on the surface of catalyst was 2.59 mmol g-1,2.77 mmol g-11 and 3.13 mmol g-1,respectively.The zero charge(pHpzc)of the three catalysts were all nearly neutral.The removal efficiency of antibiotics by catalytic ozonation of three modified silicate ores and their influencing factors were investigated.The results showed that the existence of modified silicate ore significantly improved the ozonation degradation and mineralization efficiency of antibiotics.After 30 minutes of reaction,the degradation rate of CIP in MnSO/O3 system and SMX in FeSO/O3 system was 38.8%and 39.0%,respectively,higher than that of O3 alone.In CoSO/O3 system,the degradation rate of TCH by catalytic ozonation increased from 46.0%to 93.2%when ozonated alone.All the reactions conform to the pseudo-first-order kinetic model.With the increase of catalyst dosage,the initial pH value and water temperature,the removal efficiency of antibiotics by catalytic ozonation system increased gradually,and there was a positive correlation between them.With the increase of the initial concentration of the target,the degradation effect decreased.The common inorganic ions PO43-,SO42-and Cl-in water had obvious inhibitory effects on the catalytic activity of modified silicate ore catalysts,while the inhibitory effects of K+,Na+,Ca2+,Mg2+and NO3-were not obvious.The selected modified catalysts had good stability.After repeated use,they can still maintain good catalytic activity,and the dissolution of active ingredients was small.The results of batch experiments showed that the addition of catalyst can obviously promote ozone decomposition.The process of ozone self-decomposition and catalytic ozone decomposition conform to pseudo-first-order kinetics model.The decomposition rate constants of ozone increased from 0.025 min-1(ozone self-decomposition)to 0.130min-1(MnSO catalyzed ozone decomposition),0.149 min-1(CoSO catalyzed ozone decomposition)and 0.136 min-1(FeSO catalyzed ozone decomposition),respectively.The addition of catalyst can effectively improve the ozone utilization rate.The addition of tert-butanol,a radical inhibitor,significantly inhibited the removal of antibiotics,indicating that the reaction followed the oxidation mechanism of hydroxyl radical(·OH).Molecular fluorescence spectrometry confirmed that the main active species in the catalytic ozonation system was·OH,and the amount of·OH in the system gradually accumulated with the extension of reaction time.Surface hydroxyl group was the main site of catalyst activity.Under neutral conditions,the activity of catalyst was the highest.Based on the results of LC-MS,the intermediate products of CIP,TCH and SMX were determined.It was speculated that hydroxylation,ring opening and demethylation/amino degradation of three antibiotics occurred under the oxidation of·OH and ozone molecule.The modified silicate ore catalytic ozonation reaction system established in this paper can effectively remove a variety of antibiotic pollutants in water,with high ozone utilization rate,low cost of catalyst preparation and good reusability.The system can provide guidance for the application of heterogeneous catalytic ozone technology in the efficient treatment of practical antibiotic wastewater.