α-MnO2/水界面磺胺嘧啶的氧化降解动力学

The oxidative degradation of sulfadiazine at the interface of α-MnO_2 and water

通过反歧化法合成α-MnO2,并以α-MnO2为氧化剂,研究了不同锰氧化物剂量、不同磺胺嘧啶初始浓度和不同pH值下α-MnO2/水界面磺胺嘧啶的氧化降解动力学,并讨论了不同的反应条件对反应动力学的影响。结果表明,α-MnO2可以有效的氧化降解甚至矿化磺胺嘧啶,反应符合准一级反应动力学方程,在25℃,pH4.6的反应条件下,反应120min后,11.5mmol·L-1的α-MnO2对0.02mmol·L-1磺胺嘧啶去除率达到99.98%。α-MnO2剂量和磺胺嘧啶的初始浓度均与磺胺嘧啶氧化降解的动力学常数呈显著正相关关系,相关因子分别为0.67和0.18,相关系数R分别达到0.9961和0.9979;而磺胺嘧啶的降解动力学常数与体系的pH则呈显著负相关关系,相关因子为-0.25,相关系数R达到0.9975。初步探讨了锰氧化物氧化降解磺胺嘧啶机理。研究表明,土壤及沉积物中的锰氧化物可以有效促进其中残留抗生素类药物磺胺嘧啶的降解消除过程。

α-MnO2 was prepared through a low-temperature liquid-phase comproportionation method. The kinetics of oxidative degradation of sulfadiazine （SD） at the interface of α-MnO2 and water were investigated as a function of the α-MnO2 dosage, initial concentration of SD and reaction pH. The reaction kinetics was affected by factors including dosage of a-M nO2, initial concentration of SD and pH. The experimental results showed that SD was rapidly degraded and even mineralized by α-MnO2. The SD degradation process followed the pseudo-first-order kinetics. After 120 minutes, SD removal efficiency （99.98%） were determined in the course of the degradation of 0.02 mmol.L^-1 SD by 11.5 mmol·L^-1 α-MnO2 at 25 and pH 4.6. The dosage of α-MnO2 and the initial concentration of SD were positively correlated with the kobs values. Apparent reaction orders for SD and α-MnO2 were 0.67 and 0.18, and the correlation coefficients （R） were 0.9961 and 0.997 9, respectively. The result showed that the values of kobs decreased linearly when pH increased from 3.6 to 9.0. Reaction order with respect to H＋ was -0.25, and correlation coefficient （R） was 0.997 5. The kinetics of oxidative degradation of sulfadiazine by α-MnO2 was also discussed with respect to the dosage of α-MnO2, the initial concentration of SD and reaction pH values. The results of this study indicate that natural manganese oxides in soils and sediments are likely to promote appreciable degradation of SD antibiotics for remediation of contaminated soil and surface water.