Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
Water Res. 2017 Dec 1;126:111-121. doi: 10.1016/j.watres.2017.09.020. Epub 2017 Sep 13.
Graphene was successfully employed as a catalyst for the activation of sodium persulfate, towards the effective degradation of propylparaben, an emerging micro-pollutant, representative of the parabens family. A novel process is proposed which utilizes a commercial graphene nano-powder as the catalyst and sodium persulfate as the oxidizing agent. It was found that over 95% of micro-pollutant degradation occurs within 15 min of reaction time. The effects of catalyst loading (75 mg/L to 1 g/L), sodium persulfate (SPS) concentration (10 mg/L to 1 g/L), initial solution pH (3-9) and initial paraben concentration (0.5 mg/L to 5 mg/L) were examined. Experiments were carried out in different aqueous conditions, including ultrapure water, bottled water and wastewater in order to investigate their effect on the degradation rate. The efficiency of the process was lower at complex water matrices signifying the role of organic matter as scavenger of the oxidant species. The role of radical scavengers was also investigated through the addition of methanol and tert-butanol in several concentrations, which was found to be important only in relatively high values. An experiment in which propylparaben was substituted by methylparaben was conducted and similar results were obtained. The consumption of SPS was found to be high in all pH conditions tested, surpassing 80% in near neutral environment. However, the results indicate that the sulfate radicals formed react with water in alkaline conditions, which are the optimal for the reaction, producing hydroxyl radicals which appear to be the dominant species leading to the rapid degradation of propylparaben. To the best of our knowledge, this is the first time pristine graphene has been implemented as an activator of sodium persulfate for the effective oxidation of micro-pollutants.
石墨烯成功地被用作激活过硫酸钠的催化剂，用于有效降解对羟基苯甲酸丙酯，这是一种新兴的微污染物，代表了对羟基苯甲酸酯类家族。提出了一种新的过程，利用商业石墨烯纳米粉末作为催化剂和过硫酸钠作为氧化剂。研究发现，在 15 分钟的反应时间内，超过 95%的微污染物降解。考察了催化剂用量（75mg/L 至 1g/L）、过硫酸钠（SPS）浓度（10mg/L 至 1g/L）、初始溶液 pH 值（3-9）和初始对羟基苯甲酸酯浓度（0.5mg/L 至 5mg/L）的影响。实验在不同的水介质中进行，包括超纯水、瓶装水和废水，以研究它们对降解速率的影响。在复杂的水基质中，该过程的效率较低，这表明有机物作为氧化剂的清除剂的作用。通过在不同浓度下添加甲醇和叔丁醇来研究自由基清除剂的作用，发现只有在较高浓度下才起重要作用。进行了用甲基对羟基苯甲酸酯替代对羟基苯甲酸丙酯的实验，得到了相似的结果。发现所有测试 pH 值条件下 SPS 的消耗都很高，在接近中性环境中超过 80%。然而，结果表明，在碱性条件下形成的硫酸根自由基与水反应，这是反应的最佳条件，产生羟基自由基，这似乎是导致对羟基苯甲酸丙酯快速降解的主要物质。据我们所知，这是首次将原始石墨烯用作过硫酸钠的激活剂，用于有效氧化微污染物。
