Dong Jun, Li Fang-bai, Lan Chong-yu, Liu Cheng-shuai, Li Xiao-min, Luan Tian-gang
School of Life Science, Sun Yat-sen University, Guangzhou, China.
J Environ Sci (China). 2006;18(4):777-82.
To understand the degradation of endocrine disrupting chemicals (EDCs) in natural environment with existence of iron oxides and carboxylic acids, the dependence of bisphenol A (BPA) photodegradation on the initial concentration of oxalate (COX) in lepidocrocite (gamma-FeOOH) aqueous suspension was investigated under both UV and visible lights in this study. Lepidocrocite powder was home-prepared by a hydrothermal process. It was found that BPA degradation was promoted greatly in the presence of oxalate owing to the formation of lepidocrocite-oxalate complex. And there was an optimal COX, which was 2.0 and 2.4 mmol/L, under UV and visible lights, respectively. The first-order kinetic constant, k value increased 38 times from 0.17 x 10(-2) min(-1) in the absence of oxalate to 6.39 x 10(-2) min(-1) in the presence of oxalate with an optimal COX (2.0 mmol/L) under UV irradiation, and almost 306 times from 0.02 x 10(-2) min(-1) in the absence of oxalate to 6.11 x 10(-2) min(-1) in the presence of oxalate with an optimal COX (2.4 mmol/L) under visible irradiation. The BPA degradation rate increased and the first-order kinetic constants decreased with the increase in BPA initial concentration. The dependence of the variation of pH value, total-Fe and Fe2+ during the photoreaction on COX was also investigated. The pH value increased obviously with the reaction time. Total-Fe increased dramatically at the first 5 min and then decreased quickly under UV irradiation and slowly under visible irradiation. The initial concentration of oxalate is a main factor to affect BPA photodegradation in aqueous suspension under both UV and visible lights.
为了解在存在铁氧化物和羧酸的自然环境中内分泌干扰化学物质（EDCs）的降解情况，本研究考察了在紫外光和可见光下，水铁矿（γ-FeOOH）水悬浮液中双酚A（BPA）光降解对草酸盐（COX）初始浓度的依赖性。水铁矿粉末通过水热法自制。研究发现，由于形成了水铁矿-草酸盐络合物，草酸盐的存在极大地促进了BPA的降解。在紫外光和可见光下，分别存在一个最佳的COX，其值分别为2.0和2.4 mmol/L。一级动力学常数k值在紫外光照射下，从不存在草酸盐时的0.17×10⁻² min⁻¹增加到存在最佳COX（2.0 mmol/L）草酸盐时的6.39×10⁻² min⁻¹，增加了38倍；在可见光照射下，从不存在草酸盐时的0.02×10⁻² min⁻¹增加到存在最佳COX（2.4 mmol/L）草酸盐时的6.11×10⁻² min⁻¹，增加了近306倍。随着BPA初始浓度的增加，BPA降解速率增加而一级动力学常数降低。还研究了光反应过程中pH值、总铁和Fe²⁺的变化对COX的依赖性。pH值随反应时间明显增加。在紫外光照射下，总铁在前5分钟急剧增加，然后迅速下降；在可见光照射下下降缓慢。草酸盐的初始浓度是影响紫外光和可见光下水悬浮液中BPA光降解的主要因素。
