Effects Of Environmental Factors And Different Water Matrices On Photocatalysis Of Tetracycline

Antibiotics have attracted widespread attention from all walks due to the particularity of continuous emission,environmental accumulation and toxic risk.In addition,antibiotics exhibited a“persistent existence”state,and it was an urgent research subject to investigate the fate and behavior of antibiotics in natural environment.Based on the previous studies of photocatalytic degradation of antibiotics,this study simulated the complex situation of the actual water body,to reveal the characteristic of Tetracycline（TC） photocatalytic degradation under different water matrices,effects of TC photocatalytic degradation by ZnO（ZnO） as a function of aeration,heavy metals,photosensitizers,p H,nitrate and nitrite were investigated.The main results were listed as following:（1）The analysis results of TC degradation laws under Cu（Ⅱ）coexistence and aeration are as follow:TC degradation reached 91%within 120 min in the existence of Cu（Ⅱ）;Compared with nonexistence of Cu（Ⅱ）,TC under Cu（Ⅱ） coexistence was achieved higher photocatalytic degradation with pH increase from 3 to 9;Humic acid（HA） inhibited TC degradation by Zn O whether there was Cu（Ⅱ） or not;TC degradation was first accelerated and elevated while then inhibited with Cu（Ⅱ） concentration increase;Moreover,TC degradation was improved via Cu（Ⅱ）?TC surface complexation and followed N-demethylation and hydroxylation routes.TC degradation（98%）under aeration was higher than24%without aeration within 120 min;The trend of TC degradation under aeration and no aeration was the same in the range of pH 3?9.（2）Degradation rules of TC in different water matrix are different:The degradation of TC _{pure water}>TC _{river water}>TC _seawaterin non-aerated condition,TC degradation in three kinds of water solutions under aerated increased greatly;Cu（Ⅱ）,Zn（Ⅱ）,Pb（Ⅱ） and Cd（Ⅱ）promoted or inhibited the photocatalytic activity of TC in the same water matrix at different concentrations,and the same concentration of Cu（Ⅱ）,Zn（Ⅱ）,Pb（Ⅱ） and Cd（Ⅱ） exhibited different effects on the degradation of TC in different water matrixes;The photosensitization of HA in pure water to TC was lower than that of light shielding,and the photosensitization in sea water was greater than that of light shielding,HA in river water inhibited TC degradation;The degradation of TC in pure water was promoted by acetone,the degradation of TC by acetone in seawater was opposite to that of pure water,acetone promoted TC degradation in river water with high concentration,and inhibited it in low concentration;The photocatalytic degradation trend of TC in pure water and seawater was similar in pH 3?9,but the degradation effect in seawater was lower than that in pure water,and the degradation trend of TC in river water was totally different from that in seawater and pure water;NO₂^? and NO₃^?in seawater inhibited the photocatalytic degradation of TC.（3）Liquid chromatography-mass spectrometry revealed that the degradation pathways and products of TC were diverse in pure water,river water and seawater:TC in pure water was degraded by three ways:ring opening,functional group removal and oxidation reaction;In river water,it was carried out by four ways of hydroxylation,dehydration,demethylation and deamination;In seawater,five reactions including hydroxylation,epimerization,demethylation,dehydration and oxidation were carried out;CD spectrum revealed that the secondary structure of TC in pure water was easily destroyed during the catalytic process,and the combination of TC in river water and seawater with other substances was easy to produce products with more stable structure,which indirectly hindered the change of TC’s own conformation;TOC indicated the mineralization effect of TC _{pure water}>TC _{river water}>TC _{sea water}.TC in river water and sea water was more likely to produce by-products that affected the mineralization efficiency and may be accompanied by toxic hazards.In conclusion,the degradation of TC under the coexistence of heavy metals,aeration and different water substrates all showed unlike photocatalytic laws.This study could be of good potential in extrapolating the transformation of other antibiotics under different water substrates.