Department of Industrial Chemical & Environmental Engineering, Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
Int J Environ Res Public Health. 2019 Jan 11;16(2):198. doi: 10.3390/ijerph16020198.
Industrial activity is one of the most important sources of water pollution. Yearly, tons of non-biodegradable organic pollutants are discharged, at the least, to wastewater treatment plants. However, biological conventional treatments are unable to degrade them. This research assesses the efficiency of photocatalytic activation of peroxymonosulfate (PMS) by two different iron species (FeSO₄ and Fe-citrate) and TiO₂. These substances accelerate methylene blue removal by the generation of hydroxyl and sulfate radicals. The required pH and molar ratios PMS:Fe are crucial variables in treatment optimization. The kinetic removal is reduced by the appearance of scavenger reactions in acidic and basic conditions, as well as by the excess of PMS or iron. The best performance is achieved using an Fe-citrate as an iron catalyst, reaching the total removal of methylene blue after 15 min of reaction, with a molar ratio of 3.25:1 (1.62 mM of PMS and 0.5 mM Fe-citrate). Fe-citrate reached higher methylene blue removal than Fe as a consequence of the photolysis of Fe-citrate. This photolysis generates H₂O₂ and a superoxide radical, which together with hydroxyl and sulfate radicals from PMS activation attack methylene blue, degrading it twice as fast as Fe (0.092 min with Fe and 0.188 min with Fe-citrate). On the other hand, a synergistic effect between PMS and titanium dioxide (TiO₂) was observed ( = 1.79). This synergistic effect is a consequence of PMS activation by reaction with the free electron on the surface of TiO₂. No differences were observed by changing the molar ratio (1.04:1; 0.26:1 and 0.064:1 PMS:TiO₂), reaching total removal of methylene blue after 80 min of reaction.
工业活动是水污染的最重要来源之一。每年，至少有数千吨不可生物降解的有机污染物被排放到废水处理厂。然而，生物常规处理方法无法降解它们。本研究评估了两种不同的铁物种（FeSO₄ 和 Fe-柠檬酸盐）和 TiO₂ 对过一硫酸盐（PMS）的光催化活化效率。这些物质通过生成羟基和硫酸根自由基加速亚甲基蓝的去除。所需的 pH 值和 PMS:Fe 摩尔比是处理优化的关键变量。在酸性和碱性条件下，由于猝灭反应的出现以及 PMS 或铁过量，动力学去除会受到限制。使用 Fe-柠檬酸盐作为铁催化剂可获得最佳性能，在 15 分钟的反应后可实现亚甲基蓝的完全去除，摩尔比为 3.25:1（1.62 mM 的 PMS 和 0.5 mM 的 Fe-柠檬酸盐）。由于 Fe-柠檬酸盐的光解，Fe-柠檬酸盐比 Fe 具有更高的亚甲基蓝去除率。这种光解生成 H₂O₂和超氧自由基，与 PMS 活化产生的羟基和硫酸根自由基一起攻击亚甲基蓝，使其降解速度比 Fe 快两倍（Fe 为 0.092 分钟，Fe-柠檬酸盐为 0.188 分钟）。另一方面，观察到 PMS 和二氧化钛（TiO₂）之间存在协同效应（= 1.79）。这种协同效应是由于 PMS 通过与 TiO₂表面的自由电子反应而被活化的结果。改变摩尔比（1.04:1；0.26:1 和 0.064:1 PMS:TiO₂）时没有观察到差异，在 80 分钟的反应后可实现亚甲基蓝的完全去除。
