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Colloidal stability of nanosized activated carbon in aquatic systems: Effects of pH, electrolytes, and macromolecules TEXT SIZE: A A A

Nanosized activated carbon (NAC) is a novel adsorbent with great potential for water reclamation. However, its transport and reactivity in aqueous environments may be greatly affected by its stability against aggregation. This study investigated the colloidal stability of NAC in model aqueous systems with broad background solution chemistries including 7 electrolytes (NaCl, NaNO3, Na2SO4, KCl, CaCl2, MgCl2, and BaCl2), pH 4–9, and 6 macromolecules (humic acid (HA), fulvic acid (FA), cellulose (CEL), bovine serum albumin (BSA), alginate (ALG), and extracellular polymeric substance (EPS)), along with natural water samples collected from pristine to polluted rivers. The results showed that higher solution pH stabilized NAC by raising the critical coagulation concentration from 28 to 590 mM NaCl. Increased cation concentration destabilized NAC by charge screening, with the cationic influence following Ba2+ > Ca2+ > Mg2+ >> Na+ > K+. Its aggregation behavior could be predicted with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory with a Hamaker constant (ACWC) of 4.3 × 10?20 J. The presence of macromolecules stabilized NAC in NaCl solution and most CaCl2 solution following EPS > BSA > CEL > HA > FA > ALG, due largely to enhanced electrical repulsion and steric hindrance originated from adsorbed macromolecules. However, ALG and HA strongly destabilized NAC via cation bridging at high Ca2+ concentrations. Approximately half of NAC particles remained stably suspended for ~10 d in neutral freshwater samples. The results demonstrated the complex effects of water chemistry on fate and transport of NAC in aquatic environments. (C) 2021 Elsevier Ltd. All rights reserved.

Publication name

 Water Research Volume 203, 15 September 2021, 117561 https://doi.org/10.1016/j.watres.2021.117561

Author(s)

 Zhiwei Shao, Shijie Luo, Miaoting Liang, Zengping Ning, Weimin Sun, Yujing Zhu, Juncheng Mo; Yongtao Li, Weilin Huang, Chengyu Chen

Corresponding author(s) 

 CHEN Chengyu 
 cychen@scau.edu.cn   
 College of Natural Resources and Environment, South China Agricultural University, 483 Wushan Road, Guangzhou, Guangdong 510642, China

Author(s) from IGCAS   NING Zengping

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