硫酸根自由基对酸性红37的降解动力学与机制

为探索酸性红37(AR37)在硫酸根自由基作用下的降解可行性,设计了短波紫外光(UVC)活化乙腈(ACN)和水中过二硫酸钾盐K₂S₂O₈(PDS)体系,研究了UVC/PDS/(90%ACN+10%H₂O)体系中不同PDS用量、底物浓度、反应温度和光照强度等因素对AR37降解动力学的影响,借助液质联用仪对该体系中AR37的降解中间产物进行鉴定,并对AR37降解途径进行推导。结果表明:AR37在UVC/PDS/(90%ACN+10%H₂O)体系中具有较好的降解效果,反应60 min其去除率达到98%以上,降解速率为0.123 min^-1;高温和光强增强有利于PDS产生硫酸根自由基,从而提高了AR37的降解效率;UVC/PDS/(90%ACN+10%H₂O)体系中硫酸根自由基对AR37的降解占据主导作用,而AR37的初始降解途径主要包括单电子转移反应导致的脱磺酸基和偶氮键断裂,以及吸氢反应和取代反应导致的羟基化产物等。

Degradation kinetics and mechanism of Acid Red 37 under attack of sulfate radicals

In order to explore the degradation possibility of Acid Red 37 (AR37) under the attack of sulfate radicals, the system of UVC-activated potassium persulfate (PDS) was obtained in mixed solution of acetonitrile (ACN) and water. Firstly, the degradation feasibility of AR37 in different solutions, such as dimethyl sulfoxide (DMSO), N-N-dimethylformamide (DMF), ACN and water, was compared. And then the influences of the dosage of PDS, the concentration of substrate, the reaction temperature and the UVC light intensity on the degradation kinetics of AR37 were studied in the system of UVC/PDS/(90%ACN+10%H₂O). Lastly, the degradation intermediates of AR37 were identified by HPLC/MS/MS and the transformation mechanism was proposed. The results indicated that AR37 can be degraded in the system of UVC/PDS/(90%ACN+10%H₂O). The removal efficiency of AR37 is more than 98% and the pseudo-first-order rate is 0.123 min^-1. Higher temperature and light intensity facilitate producing the sulfate free radical, which is helpful for the degradation of AR37; and the sulfate free radical plays an important role in the degradation of AR37 in the system of UVC/PDS/(90%ACN+10%H₂O). Based on the degradation intermediates, the degradation pathway is deduced, such as the cleavage of azo bond and the desulfonation due to single electron transfer of the sulfate free radical, as well as hydroxylation products from hydrogen-abstracted and substitution reaction.