Study On Degradation Of Tetracycline By Manganese Dioxide/Organic Acids

Manganese oxides are highly reactive mineral phases that play an important role in controlling the cycling of biogeochemical elements and have many industrial applications.Manganese oxides are considered to be the strongest oxidants in the nature.They may affect soil composition and participate in various chemical reactions that occur in groundwater.They are the most important naturally occurring reactants or catalysts in the conversion of many organic pollutants in the natural environment.Nowadays,the use of tetracycline antibiotics are ranked second in all antibiotics over the world,and in China,tetracycline antibiotics is the most used antibiotics.Due to the high hydrophilicity and biostability of tetracycline antibiotics,it can migrate and enrich in the environment,which may affect human health and ecological environment.In this paper,we make manganese dioxide as the representative of manganese oxide,and tetracycline as tetracycline antibiotics on behalf of the study on the degradation of TC by manganese dioxide and manganese dioxide/ DOM typical components system,we discussed the initial pH,cations,DOM typical components and other factors,and the degradation products of manganese dioxide,manganese dioxide / oxalic acid,and manganese dioxide / tartaric acid system that were analyzed by UPLC-MS.The effect of manganese oxide on the degradation of TCs was further revealed,which provided a theoretical basis for further understanding the migration and transformation of TCs in manganese-containing environment.Research indicates that:?1?It is found that the degradation rate of TC increases with the initial concentration of MnO₂.For the effect of pH,the degradation rate from high to low is pH2> pH4> pH8> pH6 ? blank> pH10.The effect of Ca²⁺,Mg²⁺ and Na⁺ on the degradation of TC by MnO₂ was negligible.The inhibitory effect of Mn²⁺,Zn²⁺ and Fe3⁺ was been found.The inhibitory effect was Fe3⁺ > Mn²⁺ > Zn²⁺,and the effect of Mn²⁺ addition is not very different.The main products of MnO₂ degradation of TC include three substances with m/z of 417 and one substance with m/z of 413.?2?In the degradation of TC by manganese dioxide/DOM,?1?After the addition of HA and amino acid?lysine,tryptophan?,it inhibited the degradation of TC by MnO₂,and their additions have little effect on the reaction.The inhibitory effect of tryptophan was the strongest,and the inhibitory effect of HA and lysine was close.At the same pH,HA was still inhibited.?2?In the degradation of TC by MnO₂/organic acid system,the effect of different organic acids on the degradation of TC was different.Tartaric acid and malic acid to promote the best,followed by oxalic acid,the worst citric acid.There are two reasons for the promotion of organic acids: First,the reaction of organic acid and MnO₂ to produce Mn???can effectively promote the reaction;Second,the addition of organic acid makes the solution acidic,which is beneficial to the degradation of TC by MnO₂ itself.?3?The effect of different oxalic acid on the degradation of TC in the MnO₂/oxalic acid system was significantly different.The degradation rate of TC on the initial concentration of oxalic acid at 75?M was the best.When the initial concentration was higher than 125?M,the degradation rate on TC began to decrease.The degradation rate on TC was lower than that of MnO₂ at 500?M.When the concentration was at 4000?M,degradation was not occurred.?4?For the effect of pH,the degradation rate from high to low is blank ? pH4> pH8 ? pH6> pH2> pH10.For MnO₂/citric acid system,MnO₂/tartaric acid system,MnO₂/malic acid system on the degradation of TC,the higher concentration of organic acids,the greater the role of its promotion.The effect of MnO₂ / tartaric acid system on the degradation of TC was significant,and the degradation rate was pH2> pH4? blank> pH8> pH6> pH10.The addition of Ca²⁺,Zn²⁺,Mg²⁺,Na⁺ on the degradation of TC was negligible,but Mn²⁺ promotes this reaction,and it is stronger as the increase of Mn²⁺ addition.And the Fe3⁺ addition is inhibitory effect.?5?MnO₂/ oxalic acid degradation of TC products mainly include one substance with m/z of 477,one substance with m/z of 461,one substance with m/z of 431,one substance with m/z of 413,two substances containing m/z of 475,two substances with m/z of 459.The main products of MnO₂/tartaric acid degradation were similar to those of MnO₂/oxalic acid system.