Department of Civil and Environmental Engineering, Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, Republic of Korea; Korea Testing Certification Institute, 20, Gukgasandan-daero 40-gil, Guji-myeon, Dalseong-gun, Daegu, Republic of Korea.
Department of Civil and Environmental Engineering, Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, Republic of Korea.
Water Res. 2023 Nov 1;246:120715. doi: 10.1016/j.watres.2023.120715. Epub 2023 Oct 10.
Sustained activation of persulfate through the slow release of Fe(II) from silica-coated nanosized zero-valent iron (nZVI) particles (nZVI@SiO) was investigated. Slow release of Fe(II) prevented radical scavenging by excess Fe(II) and increased the radical yield, which improved the stoichiometric efficiency of phenol degradation. Sulfate and hydroxyl radicals were found to be the main oxidative species produced during phenol degradation and were found to make comparable contributions to oxidation. The nZVI@SiO particle silica shell thickness controlled the release of Fe(II) and therefore the sustained activation of persulfate and was strongly affected by the synthesis conditions, including the [Si]/[Fe] ratio and silica supply rate. Optimal sustained phenol degradation was achieved when nZVI@SiO particles were synthesized using a [Si]/[Fe] ratio of 0.5 and a tetraethyl orthosilicate supply rate of 0.5 mL/min, and this was attributed to the nZVI@SiO particles giving an optimal Fe(II) release rate and therefore a high persulfate activation rate and a high phenol removal efficiency. Sustained persulfate activation induced by Fe(II) being slowly released was described well by single-stage first-order kinetics rather than two-stage first-order kinetics typical of unmodified nZVI/persulfate systems. Persulfate was found still to be activated by iron (oxyhydr)oxides minerals after the nZVI@SiO particles had been exhausted but the persulfate sustained activation induced by the slow release of Fe(II) played a crucial role in determining the overall degradation efficiency. The results highlight the importance of the slow release of Fe(II) from nZVI-based materials for in situ chemical oxidation through sustained persulfate activation.
通过从涂覆有二氧化硅的纳米零价铁（nZVI）颗粒（nZVI@SiO）中缓慢释放 Fe(II) 来持续激活过硫酸盐的方法得到了研究。缓慢释放的 Fe(II) 可防止过量 Fe(II) 清除自由基，并增加自由基的产率，从而提高苯酚降解的化学计量效率。在苯酚降解过程中发现硫酸盐和羟基自由基是主要的氧化物种，它们对氧化的贡献相当。nZVI@SiO 颗粒的二氧化硅壳层厚度控制 Fe(II)的释放，从而控制过硫酸盐的持续激活，这强烈受到合成条件的影响，包括 [Si]/[Fe] 比和二氧化硅供应率。当使用 [Si]/[Fe] 比为 0.5 和正硅酸乙酯供应率为 0.5 mL/min 来合成 nZVI@SiO 颗粒时，可实现最佳的持续苯酚降解，这归因于 nZVI@SiO 颗粒具有最佳的 Fe(II)释放速率，从而具有高的过硫酸盐激活速率和高的苯酚去除效率。由缓慢释放的 Fe(II) 引起的持续过硫酸盐激活可以很好地用单阶段一级动力学来描述，而不是典型的未修饰的 nZVI/过硫酸盐体系的两阶段一级动力学。尽管 nZVI@SiO 颗粒已经耗尽，但仍发现铁（氧）氢氧化物矿物会激活过硫酸盐，但由 Fe(II) 的缓慢释放引起的持续过硫酸盐激活在确定整体降解效率方面起着关键作用。研究结果强调了 nZVI 基材料中缓慢释放 Fe(II) 对通过持续过硫酸盐激活进行原位化学氧化的重要性。
