Yilmaz Emine, Altiparmak Ezgi, Dadaser-Celik Filiz, Ates Nuray
Graduate School of Natural and Applied Sciences, Erciyes University, Kayseri 380320, Turkey.
Department of Environmental Engineering, Erciyes University, Kayseri 380320, Turkey.
ACS Omega. 2023 Aug 18;8(35):31758-31771. doi: 10.1021/acsomega.3c02588. eCollection 2023 Sep 5.
Although activated carbon adsorption is a very promising process for the removal of organic compounds from surface waters, the removal performance for nonionic pesticides could be adversely affected by co-occurring natural organic matter. Natural organic matter can compete with pesticides during the adsorption process, and the size of natural organic matter affects the removal of pesticides, as low-molecular-weight organics directly compete for adsorbent sites with pesticides. This study aims to investigate the competitive impact of low-molecular-weight organics on the adsorptive removal of acetochlor and metolachlor by four commercial powdered activated carbons. The adsorption features of selected powdered activated carbons were evaluated in surface water samples collected from the influent stream of the filtration process having 2.75 mg/L organic matter and 0.87 L/mg-m specific UV absorbance. The adsorption kinetics and capacities were examined by employing pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models and modified Freundlich and Langmuir isotherm models to the experimental data. The competitive removal of acetochlor and metolachlor in the presence of natural organic matter was evaluated for varied powdered activated carbon dosages on the basis of UV and specific UV absorbance values of adsorbed organic matter. The adsorption data were well represented by the modified Freundlich isotherm, as well as pseudo-second-order kinetics. The maximum organic matter adsorption capacities of the modified Freundlich isotherm were observed to be 120.6 and 127.2 mg/g by Norit SX Ultra and 99.5 and 100.6 mg/g by AC Puriss for acetochlor- and metolachlor-containing water samples, respectively. Among the four powdered activated carbons, Norit SX Ultra and AC Puriss provided the highest natural organic matter removal performances with 76 and 72% and 71 and 65% for acetochlor- and metolachlor-containing samples, respectively. Similarly, Norit SX Ultra and AC Puriss were very effective for adsorbing aromatic organics with higher than 80% specific UV absorbance removal efficiency. Metolachlor was almost completely removed by higher than 98% by Norit SX Ultra, Norit SX F Cat, and AC Puriss, even at low adsorbent dosages. However, an adsorbent dose of 100 mg/L and above should be added for all powdered activated carbons, except for Norit SX F Cat, for achieving an acetochlor removal performance of higher than 98%. The competition between low-molecular-weight organics (low-specific UV absorbance) and acetochlor and metolachlor was more apparent at low adsorbent dosages (10-75 mg/L).
尽管活性炭吸附是从地表水中去除有机化合物的一种非常有前景的方法，但同时存在的天然有机物可能会对非离子型农药的去除性能产生不利影响。天然有机物在吸附过程中会与农药竞争，并且天然有机物的大小会影响农药的去除，因为低分子量有机物会直接与农药竞争吸附剂位点。本研究旨在调查低分子量有机物对四种商用粉末活性炭吸附去除乙草胺和异丙甲草胺的竞争影响。在从过滤过程进水口采集的地表水样品中评估所选粉末活性炭的吸附特性，该样品含有2.75mg/L的有机物和0.87L/mg-m的特定紫外吸光度。通过将伪一级、伪二级和颗粒内扩散动力学模型以及修正的弗伦德里希和朗缪尔等温线模型应用于实验数据，研究吸附动力学和吸附容量。根据吸附有机物的紫外和特定紫外吸光度值，评估了不同粉末活性炭投加量下天然有机物存在时乙草胺和异丙甲草胺的竞争去除情况。吸附数据用修正的弗伦德里希等温线以及伪二级动力学能很好地表示。对于含乙草胺和异丙甲草胺的水样，Norit SX Ultra和AC Puriss的修正弗伦德里希等温线的最大有机物吸附容量分别为120.6mg/g和127.2mg/g以及99.5mg/g和100.6mg/g。在四种粉末活性炭中，Norit SX Ultra和AC Puriss对天然有机物的去除性能最高，含乙草胺和异丙甲草胺的样品分别为76%和72%以及71%和65%。同样，Norit SX Ultra和AC Puriss对吸附芳香族有机物非常有效，特定紫外吸光度去除效率高于80%。即使在低吸附剂投加量下，Norit SX Ultra、Norit SX F Cat和AC Puriss对异丙甲草胺的去除率也几乎达到98%以上。然而，除了Norit SX F Cat之外，所有粉末活性炭都应添加100mg/L及以上的吸附剂剂量，以实现高于98%的乙草胺去除性能。在低吸附剂投加量（10 - 75mg/L）下，低分子量有机物（低特定紫外吸光度）与乙草胺和异丙甲草胺之间的竞争更为明显。
