Toxicity Analysis And Photocatalytic Degradation Of Antibiotics And Metal Composite Pollutants

With the rapid growth of antibiotics and metals contamination in environmental system,the combination risk of antibiotics and heavy metal ions pollution has continuously growing,especially the common tetracyclines,sulfas and quinolones.There are many electron donor groups(carboxyl,hydroxyl,amino,etc.)and heteroatoms(such as N,O,S,etc.)in the structure of antibiotics that can be compounded with the missing electrons of metal ions.Complex pollutants formed by antibiotics and metals bring new environmental problems.In order to better control this compound pollutant,it’s necessary to further study the combination of antibiotics and heavy metal ions and its toxicity changes,seeking the treatment of the compound pollutants.In this article,six antibiotics including tetracycline antibiotics(TC,CTC),quinolone antibiotics(OFLX,NOR),sulfonamide antibiotics(SMZ,SM2)and metal ions of copper and zinc were used as research objects,the mechanism of compound pollutants formed by antibiotics and metals was detected by IR,UV-vis and circular diehroism spectroscopy.The effect of the solution environments(concentrations of metal ions,pH of solutions,coexisting anions,humic acid,etc.)on the combination of antibiotics and metals were analyzed.The result showed that these six antibiotics with metal copper,zinc can form complex compounds.And the higher the content of metal ions in water environment was,the easier it is to compound with antibiotics;when the condition of solution pH(pH>8)was alkaline,the antibiotics were easier to compound with the metals.The coexistence of anion in the solution were beneficial to the combination of antibiotics and metals;Humic acid effect of the formation of metal and antibiotics complexes,but 20 mg/L to 100mg/L of humic acid had no effect on the metal-antibiotic compound;the order of antibiotic with metal formed complex compound was tetracyclines>quinolones>sulfonamides.Compared with zinc ions,copper ions were easily compounded with antibiotics.The toxicity of compounds of antibiotics and with different molar ratios metals was studied by chlorella as a test creature.The toxicity of antibiotics,metals,their compounds were evaluated by chlorella growth curve inhibition rate and Chlorella acute toxicity(EC50).The result showed that the toxicity of antibiotics-metals compound was increased compared with the original antibiotic;that is because of the complex.The photodegradation of antibiotics and complex with metal in the simulated wastewater was investigated by photocatalytic technology.The photocatalytic oxidation efficiency of tetracycline,chlortetracycline,norfloxacin,sulfamethoxazole,sulfamethazine and with metal compounds was compared.The result showed that the degradation efficiency reach 90.94%under 250W simulated sunlight for 180min for 0.1 g/L ofloxacin at neutral solution(pH=7)and 1g/L catalyst dosage.However,the degradation efficiency of ofloxacin and metal copper and zinc compounds was 49.82%and 84.11%respectively.Compared with pure of antibiotics,the photocatalytic degradation efficiency of compounds of tetracycline,chlortetracycline,norfloxacin,sulfamethoxazole,sulfamethazine and copper,zinc ions decreased by about 20%,15%,40%,50%%,3%,12%and 2%、5%、9%、6%、4%、7%,respectively.Indicating that antibiotics forming complexes with metal ions,is to inhibit its photocatalytic degradation.