氧协同菱铁矿降解微囊藻毒素机理研究

已知在无氧条件下天然矿物菱铁矿能成功水解微囊藻毒素-LR(MC-LR),然而实际应用过程中难以避免水中溶解氧(O₂)的存在,因此有必要深入研究不同溶氧量(DOC)条件下菱铁矿对MC-LR降解的影响。本文通过在无氧和有氧条件下菱铁矿对MC-LR的降解实验,发现在有氧条件下(溶氧量1.62～21.87 mg/L), MC-LR的降解速率均比无氧条件(k₀=0.030 16 mg·L^-1·h^-1)高且其降解速率随O₂含量增加而依次增加,当O₂加入量为1.0 mL(溶氧量21.87 mg/L)时,菱铁矿对MC-LR降解速率最大(0.083 34 mg·L^-1·h^-1),为无氧条件下的2.76倍。通过外加腐殖酸(humic acid, HA)和自由基进行捕获实验,发现FeCO₃能直接活化O₂产生超氧自由基(·O~-₂),以实现对MC-LR的氧化,但外加HA抑...

Study on the mechanism of synergistic degradation of microcystin by oxygen and siderite

It has been found that siderite(FeCO₃)could directly hydrolyze microcystin-LR(MC-LR)under anaerobic conditions in previous studies.However,oxygen(O₂)could not be completely avoided during application process.Therefore,it is urgent to study the effect of dissolved oxygen content(DOC)on the degradation efficiency of MC-LR by siderite.The results showed that the degradation rate of MC-LR under O₂ conditions(DOC=1.62~21.87 mg/L)is higher than that under anaerobic conditions(k₀=0.03016 mg·L^-1·h^-1),and its degradation rate increased with the increase of O₂ content.When the volume of O₂ added was 1.0 mL(DOC=21.87 mg/L),siderite showed the highest degradation rate of MC-LR(0.08334 mg·L^-1·h^-1),which was 2.76 times higher than that without O₂.According to humic acid(HA)additions and radical capture experiments,it indicated that siderite could directly activate O₂ to produce superoxide radical(·O₂^-),facilitating the oxidation of MC-LR.However,the addition of HA inhibits the selective hydrolysis of MC-LR by FeCO₃.Finally,the LC-ESI/MS analysis of MC-LR degradation intermediates showed that under aerobic conditions,the hydrolysis sites of MC-LR occurred in Mdha—D-Ala and Adda—L-Arg peptides.Bond,under the oxidation of(·O₂^-)produced by the activation of O₂ by Fe^Ⅱon the FeCO₃ surface,the hydrolyzed product continues to undergo hydroxylation and decarboxylation reactions,and is finally converted into small molecular aldehydes.