Department of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China.
Department of Environmental Engineering, Chang'An University, Xi'an, 710064, Shanxi, China.
Chemosphere. 2020 Mar;242:125062. doi: 10.1016/j.chemosphere.2019.125062. Epub 2019 Oct 5.
Removing dissolved organic matter (DOM) is of great concern due to its adverse effects on water supplies. Great effort has been given to studying DOM removal by coagulation, while the mechanism of DOM removal and the changes in its properties during coagulation have not been clearly illustrated due to the limitations of detection methods under practical environmental conditions. In this paper, the changes in DOM during coagulation were quantified using differential UV-Visible absorbance spectroscopy, and the differential spectra of DOM in the wavelength range of 200-600 nm could be deconvoluted into six Gaussian bands with maxima at approximately 200, 240, 276, 316, 385, and 457 nm after coagulation, respectively. The intensity of these maxima decreased with the type and dosage of coagulants. These observations should reflect the difference in the removability of DOM by coagulation, and this perspective was further confirmed by examining the deprotonation-protonation properties of DOM before and after coagulation. The affinity sites of DOM in coagulated waters, quantified by spectra parameter DlnA (differential log-transformed spectra at wavelength 400 nm) in combination with the revised NICA model, increased as the coagulant dosage, which indicates that coagulation is inclined to remove the DOM fraction with fewer functional groups. Polyaluminum chloride (PAC) and Al-aggregate (Al) were more efficient than Alum for removing DOM due to their high efficiency for removing DOM fractions with fewer functional groups. The residual dissolved Al concentration depended on the total amount of reactive binding sites in DOM, and there was a strong linear correlation between residual dissolved Al and the total amount of reactive binding sites in DOM for Alum, while a weaker correlation was presented for PAC and Al. This indicates that Al was the dominant species to bind with the affinity sites in DOM to form residual dissolved Al.
去除溶解的有机物（DOM）是非常重要的，因为它会对供水造成不利影响。人们已经付出了很大的努力来研究通过混凝去除 DOM，但是由于实际环境条件下检测方法的局限性，DOM 的去除机制及其在混凝过程中性质的变化尚未得到清楚的说明。在本文中，使用差示紫外-可见吸收光谱定量研究了 DOM 在混凝过程中的变化，并且 DOM 在 200-600nm 波长范围内的差示光谱可以在混凝后分别解卷积为六个具有最大值的高斯带，其最大值约为 200、240、276、316、385 和 457nm。这些最大值的强度随混凝剂的类型和剂量而降低。这些观察结果应该反映了 DOM 通过混凝去除的可去除性的差异，并且通过检查混凝前后 DOM 的去质子化-质子化性质进一步证实了这一观点。通过光谱参数 DlnA（400nm 波长处的差分对数变换光谱）与修订后的 NICA 模型相结合，定量了混凝水中 DOM 的亲和位点，随着混凝剂剂量的增加而增加，这表明混凝倾向于去除具有较少官能团的 DOM 部分。聚合氯化铝（PAC）和 Al-聚集体（Al）比明矾更有效地去除 DOM，因为它们对去除具有较少官能团的 DOM 部分的效率更高。残留溶解 Al 的浓度取决于 DOM 中反应性结合位点的总量，并且对于明矾，残留溶解 Al 与 DOM 中反应性结合位点的总量之间存在很强的线性相关性，而对于 PAC 和 Al 则存在较弱的相关性。这表明 Al 是与 DOM 中的亲和位点结合形成残留溶解 Al 的主要物质。
