School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
Water Res. 2017 Oct 1;122:701-707. doi: 10.1016/j.watres.2017.06.041. Epub 2017 Jun 15.
Bromate (BrO), as a contaminant producing from bromide (Br) oxidation, has been revealed for generation in sulfate radical involved processes. In this work, reduced graphene oxide (rGO) was firstly applied to inhibit the formation of BrO in thermally activated peroxymonosulfate (thermal/PMS) treatment. In the presence of 5-35 mg/L rGO, the decomposition rate of PMS was slightly increased from 0.0162 ± 0.0013 min to 0.0200 ± 0.0010 min, corresponding to removal rate of target pollutant increasing from 0.0157 ± 0.0012 min to 0.0204 ± 0.0022 min. This suggested the decay of PMS, the concentration and distribution of radicals were not influenced dramatically by the addition of rGO, which was partly supported by the almost unchanged HPLC chromatograms as compared with that in the absence of rGO. However, the produced BrO was significantly lowered by 67%-100% with the addition of rGO in a wide range of pH at 5-9 and activation temperature at 60-80 °C. Moreover, a quick reduction of hypobromous acid (HOBr) to Br was achieved with addition of rGO at room temperature, whilst no abatement of BrO and Br was observed in the same conditions. Therefore, masking HOBr was probably the role of rGO on bromate inhibition in thermal/PMS process. Because HOBr is a requisite intermediate for BrO, the inhibition effect of rGO is likely irrelevant of oxidation processes, which was inevitably showed by the good performance of rGO on BrO suppress in ozonation. Therefore, the addition of rGO in tens of mg/L is a promising measure to avoid the formation of unwanted bromine species in advanced oxidation processes.
溴酸盐（BrO ）作为溴化物（Br ）氧化产生的污染物，已被证明在硫酸根自由基参与的过程中生成。在这项工作中，首先将还原氧化石墨烯（rGO ）应用于抑制热激活过一硫酸盐（thermal/PMS ）处理中 BrO 的形成。在 5-35mg/L rGO 的存在下，PMS 的分解速率从 0.0162±0.0013min 略有增加至 0.0200±0.0010min ，相应的目标污染物去除速率从 0.0157±0.0012min 增加至 0.0204±0.0022min 。这表明 PMS 的衰减，自由基的浓度和分布并没有因 rGO 的添加而受到显著影响，这在一定程度上得到了支持，因为与不存在 rGO 的情况相比，HPLC 色谱图几乎没有变化。然而，在 5-9 的 pH 和 60-80°C 的活化温度范围内，添加 rGO 可显著降低 BrO 的生成，降低幅度为 67%-100%。此外，在室温下添加 rGO 可迅速将次溴酸（HOBr ）还原为 Br ，而在相同条件下，BrO 和 Br 没有减少。因此，掩蔽 HOBr 可能是 rGO 在 thermal/PMS 过程中抑制溴酸盐形成的作用。因为 HOBr 是 BrO 的必要中间体，所以 rGO 的抑制作用可能与氧化过程无关，这在 rGO 在臭氧氧化中对 BrO 抑制的良好性能中不可避免地表现出来。因此，在数十毫克/升的添加量下，添加 rGO 是避免高级氧化过程中形成不需要的溴化物的一种有前途的措施。
