A two-sorbent system for fast uptake of arsenate from water: Batch and column studies. (1st January 2023)

• Record Type: Journal Article
• Authors: Wang, Zhengyang; Bi, Xiangyu; He, Xiaoqing; Xie, Yunchao; Lin, Jian; Deng, Baolin
• Is Part Of: Water research. Volume 228(2023)Part B
• Publication Date: 2023-01-01
• Subjects: Water treatment -- Arsenic -- Kinetics -- Adsorption -- Extraction -- Dialysis; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.119290
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Capture-and-storage sorption process is proposed for small water treatment systems. Two sorbents work in tandem for rapid capturing of arsenate from water. The first sorbent sorbs arsenate more rapidly than the second one. Arsenate can be relocated to the second sorbent with a larger capacity for storage. The relocation process would optimally occur when no water flows through a unit. Abstract: There is a critical need to use decentralized and/or point-of-use systems to address some challenging water quality issues in society. Sorption-based approaches are uniquely suitable for such applications because of their simplicity in operation; however, the sorbents must possess fast contaminant uptake kinetics to overcome short hydraulic contact times often encountered in small systems. Here we designed a two-sorbent system consisting of Fe2 O3 -coated mesoporous carbon (FeMC) and nano-Fe2 O3 -coated activated carbon (FeAC) and demonstrated its ability to remove arsenate with a < 1 min empty bed contact time (EBCT) by a capture-and-storage process. Batch experiments showed rapid capture of arsenate by FeMC, likely occurred on the rod-like structures protruding to the liquid film. The captured arsenate could subsequently be relocated to FeAC for storage, which had a higher apparent sorption capacity. Column studies, operated with a 10 h running time followed by a 14 h pump-off time, showed that with a 102 μ g-As/L influent concentration and at 0.85 min EBCT, the column treated 20, 022 bed volumes until the 10 μ g-As/L breakthrough, corresponding to a sorption density of 2.36 mg-As/g. This capture-and-storage technique resulted in a rapid and high-capacity arsenate removal through a combined effect of facile access to sorption sites on one sorbent and dynamic equilibrium in the two-sorbent system possessing a large total sorption capacity. Graphical abstract: Image, graphical abstract