Department of Chemistry, University of Ibadan, Ibadan, Nigeria; Institute of Soil Science and Soil Conservation, Justus Liebig University, Giessen, Germany.
Department of Chemistry, Vaal University of Technology, Vanderbijlpark, South Africa; Institute of Soil Science and Soil Conservation, Justus Liebig University, Giessen, Germany.
J Environ Manage. 2021 Feb 1;279:111619. doi: 10.1016/j.jenvman.2020.111619. Epub 2020 Nov 6.
Several emerging contaminants are currently used in an unregulated manner worldwide, resulting in their increasing stringent limits in water by regulatory bodies. Thus, more viable and cheap treatment technologies are required. Recently, synergistic combinations of low-cost adsorbents have shown huge potential for aqueous toxic metals adsorption in water treatment processes. However, there is dearth of data on their potential for emerging contaminant removal. Here, low-cost kaolinite (KAC) clay was synergistically combined with blended Carica papaya or pine cone seeds, and calcined to obtain composites of KAC-Carica papaya seeds (KPA) and KAC-pine cone seeds (KPC). These adsorbents were characterized and evaluated for ivermectin adsorption at varying operating times (15-1440 min), pH (3-11), concentration (100-600 μg/L), and temperature (19.5-39.5 °C), as well as testing adsorbents' reusability. The composites exhibited marked property differences including over 250% cation exchange capacity increases and ≥50% surface area decreases, but unchanged KAC clay primary lattice structure. Ivermectin adsorption data were explained using kinetics and adsorption isotherm models. The rate of adsorption on KAC decreased over time, while rates for KPA and KPC increased until equilibrium at 180 min; the presence of biomaterials in the composites conferred better ivermectin adsorption and retention under continuous agitation. The adsorbents exhibited dual adsorption peaks one each at the acidic and alkaline pH regions as solution pH changed from 3 to 11. The rate data fitted (≥0.9232) the homogeneous fractal Pseudo-Second Order (FPSO) better than any other kinetics model, as well as the Freundlich adsorption isotherm model (≥0.9887); these indicate complex interactions between ivermectin and the adsorption sites of both composites. Ambient temperature increase up to ≈30 °C caused higher ivermectin adsorption but beyond this temperature there was drastic drop in adsorption. The KPA and KPC adsorption capacities are 105.3 and 115.8 μg/g, respectively. The KPC was better at reducing ivermecitn in low-concentration solution (≈75 μg/L) to less than 5.0 μg/L compared with KPA with ≈20.0 μg/L. Though KPC showed better efficiency in adsorption capacity and lowering concentration in low-concentration solutions, KPA exhibited better reusability with 83.5 and 67.5% initial adsorption strengths remaining in the second and third adsorption cycles, respectively, compared to the 73.8 and 58.8% for the KPC. These results indicate that KPA and KPC composites have the economic potential for application in water treatment processes.
目前，全球有几种新兴污染物正在被无管制地使用，这导致监管机构对水中这些污染物的含量设定了越来越严格的限制。因此，需要更可行和更廉价的处理技术。最近，廉价吸附剂的协同组合在水处理过程中对水中有毒金属的吸附显示出巨大的潜力。然而，关于它们去除新兴污染物的潜力的数据却很少。在这里，我们将低成本的高岭土（KAC）粘土与混合番木瓜或松果种子协同组合，并进行煅烧，以获得 KAC-番木瓜种子（KPA）和 KAC-松果种子（KPC）复合材料。对这些吸附剂进行了表征，并在不同的操作时间（15-1440 分钟）、pH 值（3-11）、浓度（100-600μg/L）和温度（19.5-39.5°C）下进行了伊维菌素吸附评估，以及测试了吸附剂的可重复使用性。这些复合材料表现出明显的性能差异，包括阳离子交换容量增加超过 250%和比表面积减少≥50%，但 KAC 粘土的主要晶格结构保持不变。伊维菌素吸附数据采用动力学和吸附等温线模型进行解释。KAC 的吸附速率随时间的推移而降低，而 KPA 和 KPC 的吸附速率则增加，直到 180 分钟达到平衡；复合材料中生物材料的存在在连续搅拌下赋予了更好的伊维菌素吸附和保留能力。吸附剂在溶液 pH 值从 3 变为 11 时，在酸性和碱性 pH 区域各显示出一个双吸附峰。速率数据（≥0.9232）更符合均匀分形拟二级（FPSO）动力学模型，也更符合 Freundlich 吸附等温线模型（≥0.9887）；这表明伊维菌素与两种复合材料的吸附位点之间存在复杂的相互作用。环境温度升高到约 30°C 会导致更高的伊维菌素吸附，但超过此温度后，吸附会急剧下降。KPA 和 KPC 的吸附容量分别为 105.3 和 115.8μg/g。与 KPA 相比，KPC 更适合在低浓度（约 75μg/L）溶液中将伊维菌素降低至 5.0μg/L 以下，而 KPA 则约为 20.0μg/L。尽管 KPC 在低浓度溶液中的吸附容量和降低浓度方面表现出更好的效率，但 KPA 在第二和第三吸附循环中仍保留了 83.5%和 67.5%的初始吸附强度，而 KPC 则分别为 73.8%和 58.8%。这些结果表明，KPA 和 KPC 复合材料具有在水处理过程中应用的经济潜力。
