Performance of L-493 Macroprous Resin for Adsorption of Trihalomethanes from Water
2018
Liu, Shaogang | Huang, Wanting | Shu, Wei | Li, Zhangyan | Goodman, B. A. (Bernard A.) | Tan, Xuecai | Diao, Kaisheng
The commercial resin Dowex Optipore L-493 was evaluated for the removal of the trihalomethanes (THMs) from water. Adsorption amounts were in the order CHBr₃ ≈ CHBr₂Cl > CHBrCl₂ > CHCl₃, insensitive to pH in the range 3.0–7.0, but decreased at pH higher values. They were little affected by the presence of co-existing anions and humic acid, and environmental impurities in a spiked natural water sample were only slightly lower than those obtained with pure water. In a comparison with several other commercial adsorbents, the overall performance of L-493 for adsorption of THMs was comparable with the best of those tested, and superior to IR 120, IRC 748, and powder activated carbon. THM adsorption on L-493 was endothermic, and fitted by the pseudo-second-order kinetic and Langmuir isotherm models; maximum adsorption was 228.6, 247.3, 250.6, and 253.7 μg/g, for CHCl₃, CHBrCl₂, CHBr₂Cl, and CHBr₃, respectively. Charge distributions and dipole moments were calculated for the optimized structures using the hybrid density functional theory (DFT) method. Both hydrophobic effects and electrostatic interactions play important roles in the adsorption process. The L-493 resin was easily regenerated and could be recycled using 0.1 M NaOH, with only a small decrease in its initial adsorption capacities. Overall, this research shows that L-493 is potentially a valuable adsorbent for the removal of THMs during water treatment.
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