This study explores the potential of modified coal fly ash (CFA) as an adsorbing material for immobilizing Per- and Polyfluoroalkyl Substances (PFAS) and bulk organic matter from landfill leachate, comparing its efficacy to that of activated carbon. Physiochemical modification of CFA using hydrochloric acid (HCl) and thermal treatment significantly enhanced its adsorption properties, increasing the BET surface area by 2.5 to 3.5 times and pore volume by 2 to 3 times. Despite the high concentrations of dissolved organic matter (DOM) in landfill leachate, modified CFA achieved up to 88 % removal of total organic carbon (TOC) and 93 % decrease of UV254 at an optimal dose of 400 g/L. The PFAS adsorption capacity reached 3.5 mg/g, representing approximately 3–15 % of that of activated carbon due to its limited surface area and pore volume. CFA possesses 5 to 15 times higher surface area based adsorption capacity (in mg/m2) than activated carbon. Adsorption kinetics were best described by a pseudo-second-order model, indicating that chemisorption is the primary mechanism. Notably, longer-chain PFAS exhibited faster adsorption rates and higher adsorption capacity with CFA. The adsorption isotherm data fits better with non-linear Langmuir isotherm compared to Freundlich isotherm, indicating that the adsorption of PFAS on CFA is monolayer adsorption. Overall, CFA demonstrates exceptional performance in leachate treatment, with its low cost and energy requirements positioning it as a promising alternative to conventional carbon-based adsorbents.

中文翻译：

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改性粉煤灰 （CFA） 对垃圾渗滤液中全氟烷基和多氟烷基物质 （PFAS） 的吸附能力及机理


本研究探讨了改性粉煤灰 （CFA） 作为吸附材料从垃圾填埋渗滤液中固定全氟烷基和多氟烷基物质 （PFAS） 和散装有机物的潜力，并将其功效与活性炭进行了比较。使用盐酸 （HCl） 对 CFA 进行物理化学改性和热处理显着增强了其吸附性能，BET 表面积增加了 2.5 至 3.5 倍，孔体积增加了 2 至 3 倍。尽管垃圾渗滤液中的溶解有机物 （DOM） 浓度很高，但在 400 g/L 的最佳剂量下，改性 CFA 实现了高达 88% 的总有机碳 （TOC） 去除率和 93% 的 UV254 降低。PFAS 吸附容量达到 3.5 mg/g，由于其表面积和孔体积有限，约为活性炭吸附容量的 3-15%。CFA 的基于表面积的吸附容量（以 mg/m2 为单位）比活性炭高 5 到 15 倍。吸附动力学最好用伪二级模型来描述，表明化学吸附是主要机制。值得注意的是，长链 PFAS 表现出更快的吸附速率和更高的 CFA 吸附容量。与 Freundlich 等温线相比，吸附等温线数据更适合非线性 Langmuir 等温线，表明 PFAS 在 CFA 上的吸附是单层吸附。总体而言，CFA 在渗滤液处理方面表现出卓越的性能，其低成本和能源需求使其成为传统碳基吸附剂的有前途的替代品。