Wang Xinghao, Pu Lirong, Sun Zhaoyue, Fang Guodong, Wang Yujun, Gu Cheng, Gao Juan
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
J Hazard Mater. 2024 Jan 15;462:132759. doi: 10.1016/j.jhazmat.2023.132759. Epub 2023 Oct 11.
The photochemical processes of dissolved humic acid and its potential contribution to As(III) oxidation in natural water has received considerable attention. However, the role of mineral-humic complexes in As(III) conversion is rarely studied. Herein, two simulated mineral-humic complexes were prepared by coating humic acid on hydrous aluminum oxide, HA@HAO, or montmorillonite, HA@SWy, respectively, and batch experiments at circumneutral pH were performed under light irradiation. Our findings showed that the light-assisted oxidation of As(III) increased with increasing fractions of organic carbon in mineral-humic complexes, and As(III) photooxidation with HA@HAO or HA@SWy was up to 18.2 or 3.5-fold higher compared to that measured in the presence of equivalent amount of free HA, respectively. The reactive triplet state of HA and hydroxyl radicals in HA@HAO and HA@SWy system made a primary contribution to As(III) oxidation under irradiation. The results indicated that mineral-humic complexes have dual roles, an adsorbent and a photosensitizer, to promote As(III) access to reactive intermediates at the particle surfaces. This process was important for As(III) conversion in paddy water as colloidal particles, composed of both minerals and HA, could greatly promote As(III) oxidation and As(V) immobilization. This study provides a previously overlooked, important mechanism of As(III) phototransformation mediated by mineral-associated humic acid in natural environment.
溶解态腐殖酸的光化学过程及其对天然水中As(III)氧化的潜在贡献已受到广泛关注。然而，矿物-腐殖质络合物在As(III)转化中的作用却鲜有研究。在此，通过将腐殖酸分别包覆在水合氧化铝（HA@HAO）或蒙脱石（HA@SWy）上制备了两种模拟矿物-腐殖质络合物，并在中性pH条件下进行了光照下的批量实验。我们的研究结果表明，As(III)的光助氧化随着矿物-腐殖质络合物中有机碳含量的增加而增加，与等量游离HA存在时相比，HA@HAO或HA@SWy体系中As(III)的光氧化分别高出18.2倍或3.5倍。HA的反应性三重态以及HA@HAO和HA@SWy体系中的羟基自由基在光照下对As(III)氧化起主要作用。结果表明，矿物-腐殖质络合物具有吸附剂和光敏剂的双重作用，可促进As(III)在颗粒表面接触反应性中间体。这一过程对于稻田水中As(III)的转化很重要，因为由矿物和HA组成的胶体颗粒可极大地促进As(III)的氧化和As(V)的固定。本研究提供了一种在自然环境中由矿物结合腐殖酸介导的As(III)光转化的重要机制，该机制此前一直被忽视。
