Van Truong Tuan, Kim Dong-Jin
Department of Environmental Sciences and Biotechnology & Institute of Energy and Environment, Hallym University, 1 Okcheon, Chuncheon, 24251, South Korea.
Department of Environmental Sciences and Biotechnology & Institute of Energy and Environment, Hallym University, 1 Okcheon, Chuncheon, 24251, South Korea.
Environ Res. 2021 May;196:110877. doi: 10.1016/j.envres.2021.110877. Epub 2021 Mar 9.
Alum sludge (AS) is an abundant and ubiquitous residue generated from drinking water treatment plants. AS was thermally treated to use as an adsorbent for phosphate removal from wastewater. Organic matter in the AS was a potential competitor and can deter phosphate adsorption. Pyrolysis and drying of AS were adopted to enhance phosphate removal by eliminating organic matter and enriching Al content. Adsorption kinetics showed that phosphate removal was highest with the AS pyrolyzed at 700 °C followed by 500 °C, air-dried and oven-dried (105 °C). Adsorption kinetic modelling showed that chemisorption is the operative mechanism of phosphate removal in all the AS. Adsorption isotherms also showed that the pyrolyzed AS and air-dried AS had similar adsorption capacity of 30.83-34.53 mg P/g AS. Al dissolution was less than 2 mg/g Al in all the AS samples. COD release was significant in the dried AS, up to 8.0 mg COD/g AS, whereas the pyrolyzed AS released less than 1 mg COD/g AS. FTIR and SEM-EDS analyses of the AS after phosphate adsorption showed the formation of aluminum-phosphate complex. Overall, the pyrolysis of AS at 700 °C was most effective in removing phosphate without leaving secondary pollution.
明矾污泥（AS）是饮用水处理厂产生的一种丰富且普遍存在的残留物。对AS进行热处理以用作从废水中去除磷酸盐的吸附剂。AS中的有机物是一种潜在的竞争物质，会阻碍磷酸盐的吸附。采用AS的热解和干燥来通过去除有机物和富集铝含量来提高磷酸盐去除率。吸附动力学表明，在700℃热解的AS对磷酸盐的去除率最高，其次是500℃热解的AS、风干和烘干（105℃）的AS。吸附动力学模型表明，化学吸附是所有AS中去除磷酸盐的作用机制。吸附等温线还表明，热解后的AS和风干的AS具有相似的吸附容量，为30.83 - 34.53 mg P/g AS。所有AS样品中的铝溶出量均小于2 mg/g Al。干燥后的AS中化学需氧量（COD）释放显著，高达8.0 mg COD/g AS，而热解后的AS释放的COD小于1 mg COD/g AS。对吸附磷酸盐后的AS进行傅里叶变换红外光谱（FTIR）和扫描电子显微镜-能谱（SEM-EDS）分析表明形成了铝-磷酸盐络合物。总体而言，700℃热解AS在去除磷酸盐且不产生二次污染方面最为有效。
