Department of Chemical Engineering, Quaid-e-Awam University of Engineering, Science and Technology (QUEST), Nawabshah 67480, Pakistan.
Institute of Environmental Sciences and Engineering (IESE), School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST) H-12 Campus, Islamabad 44000, Pakistan.
Molecules. 2021 Sep 16;26(18):5615. doi: 10.3390/molecules26185615.
The increased utilization of CuO nanoparticles (CuO NPs) in various fields has raised concerns about their discharge into water containing a wide range of organic ligands. Moreover, the adsorption of these ligands can stabilize the CuO NPs in drinking water treatment plants. Thus, their removal from potable water is important to mitigate the risk to humans. The present study explored the efficacy of the coagulation-sedimentation (C/S) process for the removal of tannic acid (TA)-stabilized CuO NPs using polyaluminum ferric chloride (PAFC) as a coagulant. Moreover, the influence of process conditions (stirring speed) and water chemistry (i.e., pH and ionic strength (IS)) were also investigated to determine their impact on removal. The results showed that stirring speed in the reaction phase significantly affected the removal due to increased flocculation compared with stirring speed in the mixing phase. In addition, pH and IS affect the colloidal stability and removal efficiency of CuO NPs. A relatively better removal performance (<99%) of CuO NPs was found at lower coagulant dosage in the pH range 6-8. The addition of organic ligands reversed the surface charge potential and enhanced the colloidal stability of CuO NPs, resulting in the destabilization of TA-CuO NPs, thereby reducing the optimum PAFC dosage for removal. By contrast, the IS above the critical coagulation concentration decreased the removal efficiency due to inhibition of the ionic activity of PAFC hydrolysate in the aqueous environment. Fourier transform infrared findings of TA-CuO NPs composite flocs suggest that the primary removal mechanism might be mediated via the combined effect of neutralization, complexation as well as adsorption.
氧化铜纳米粒子（CuO NPs）在各个领域的广泛应用引起了人们对其排放到含有各种有机配体的水中的担忧。此外，这些配体的吸附可以使氧化铜纳米粒子在饮用水处理厂中稳定存在。因此，从饮用水中去除它们对于减轻对人类的风险非常重要。本研究探讨了使用聚合氯化铝铁（PAFC）作为混凝剂通过混凝沉淀（C/S）工艺去除单宁酸（TA）稳定的氧化铜纳米粒子的效果。此外，还研究了工艺条件（搅拌速度）和水化学（即 pH 值和离子强度（IS））的影响，以确定它们对去除的影响。结果表明，反应阶段的搅拌速度由于与混合阶段的搅拌速度相比絮凝增加而显著影响去除效果。此外，pH 值和 IS 值影响氧化铜纳米粒子的胶体稳定性和去除效率。在 pH 值为 6-8 的范围内，较低的混凝剂剂量下，CuO NPs 的去除性能较好（<99%）。有机配体的添加会改变表面电荷势并增强 CuO NPs 的胶体稳定性，从而导致 TA-CuO NPs 的失稳，从而降低了去除的最佳 PAFC 剂量。相比之下，高于临界凝聚浓度的 IS 会由于抑制 PAFC 水解产物在水相中的离子活性而降低去除效率。TA-CuO NPs 复合絮体的傅里叶变换红外研究结果表明，主要的去除机制可能是通过中和、络合和吸附的综合作用介导的。
