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.

中文翻译：

---

石墨烯：过硫酸钠的新型活化剂，用于水中对羟基苯甲酸酯的高级氧化

石墨烯已成功地用作过硫酸钠活化的催化剂，从而有效降解了对羟基苯甲酸丙酯（一种新兴的微污染物，对羟基苯甲酸酯家族的代表）。提出了一种新的方法，该方法利用市售的石墨烯纳米粉作为催化剂，并用过硫酸钠作为氧化剂。发现在反应时间的15分钟内发生了超过95％的微污染物降解。催化剂负载量（75 mg / L至1 g / L），过硫酸钠（SPS）浓度（10 mg / L至1 g / L），初始溶液pH（3–9）和初始对羟基苯甲酸酯浓度（0.5 mg）的影响/ L至5 mg / L）。为了研究它们对降解速率的影响，在不同的水性条件下进行了实验，包括超纯水，瓶装水和废水。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。还通过添加几种浓度的甲醇和叔丁醇来研究自由基清除剂的作用，发现仅在相对较高的值下，自由基清除剂才是重要的。进行了将对羟基苯甲酸丙酯替换为对羟基苯甲酸甲酯的实验，并获得了相似的结果。发现在所有测试的pH条件下，SPS的消耗量很高，在接近中性的环境中，该消耗量超过80％。然而，结果表明，所形成的硫酸根在碱性条件下与水反应，这是反应的最佳条件，产生了羟基自由基，似乎是导致对羟基苯甲酸丙酯快速降解的主要物质。