Removal Of A Newly Discovered Algal Toxin BMAA By Chemical Oxidation: Performance And Impact Factors

?-N-methyl amino-L-alanine(BMAA)is a new type of algal toxins,which may be an important cause of amyotrophic lateral sclerosis(ALS)and Parkinson's disease.Most cyanobacteria have been reported to produce the BMAA and it has been detected in water and aquatic products all over the world.The water resources in many regions is facing serious eutrophication problem,and the associated BMAA problems may pose a serious threat to the safety of drinking water and health of urban residents.So far,there has been little research on the removal of BMAA from drinking water treatment process.Whether the existing water treatment process can remove BMAA and how to safely remove BMAA effectively is the problem to be solved.It is very important for the improvement of water quality and ensure the safety of water supply.According to the above problem,this study is based on the normal oxidation technology of water treatment plant,studies the removal effects of typical antioxidant sodium hypochlorite and ozone with BMAA.To study the effects on removal of BMAA which influence include oxidant concentration,temperature and pH value of different conditions.The oxidation products and oxidation pathways of BMAA oxidation by sodium hypochlorite and ozone were investigated.The study showed that oxidation of BMAA by sodium hypochlorite were in accord with the second order kinetics model,and the kinetic constants were 697.6 L/mol·min.The higher rhe temperature,the larger the reaction rate constant.Arrhenius and Eyring equation fitting get reaction of activation energy of 16.639kJ/mol,?H*of 14.106kJ/mol,?S*of 142.250 J/molK.PH value has a significant effect on the oxidation of BMAA by sodium hypochlorite.Under acidic conditions,sodium hypochlorite oxidizes BMAA with the best effect.The removal of BMAA by ozone is mainly ozone oxidation directly,the removal rate of 2 minutes is above 95%.The higher the initial concentration of ozone,ozone oxidation removing BMAA faster,ozone concentration is high enough BMAA removal rate can reach 99%,while at the same time a certain amount of ozone residual ensures BMAA completely removed.Under different pH conditions,the ozone oxidation BMAA is mainly associated with different form of BMAA under the pH condition,and the oxidation effect is best under neutral conditions,and it can be up to 97% in one minute.Low temperature conditions favorable for ozone oxidation removal BMAA,and the low temperature condition BMAA is 7.3 percent higher than the high temperature condition.During the oxidation process between BMAA and sodium hypochlorite,seven oxidation products were found.The m/z of them are 88(?),153(?),153(?),187(?),187(?),108(?)and 71(?),the main pass way is substitution reaction of chlorination,decarboxylation reaction,C-C bond rupture.And three oxidation products were found during the oxidation process between BMAA and ozone.The m/z of them are 105(?),90(?),88(?),the main pass way are C-N bond rupture and N-C bond rupture of BMAA.In this study,the removal efficiency of BMAA under two different conditions was investigated and it provided a theoretical basis for the removal of BMAA in drinking water.By comparison,we found that the removal of BMAA by ozone is more efficient and the salinity is higher compared to sodium hypochlorite,the ozone is more suitable for removal of BMAA.