The removal of arsenic from solution through biochar-enhanced precipitation of calcium-arsenic derivatives

Zama, Eric F., Li, Gang, Tang, Yu-Ting, Reid, Brian J., Ngwabie, Ngwa M. and Sun, Guo-Xin (2022) The removal of arsenic from solution through biochar-enhanced precipitation of calcium-arsenic derivatives. Environmental Pollution, 292. ISSN 0269-7491

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Abstract

Arsenic (As) pollution remains a major threat to the quality of global soils and drinking water. The health effects of As pollution are often severe and have been largely reported across Asia and South America. This study investigated the possibility of using unmodified biochar derived from rice husk (RB) and aspen wood (WB) at 400 °C and 700 °C to enhance the precipitation of calcium/arsenic compounds for the removal of As(III) from solution. The approach was based on utilizing calcium to precipitate arsenic in solution and adding unmodified biochar to enhance the process. Using this approach, As(III) concentration in aqueous solution decreased by 58.1% when biochar was added, compared to 25.4% in the absence of biochar. Varying the pH from acidic to alkaline enabled an investigation into the pH dependent dynamics of the approach. Results indicated that significant precipitation was only possible at near neutral pH (i.e. pH = 6.5) where calcium arsenites (i.e. Ca(AsO 2) 2, and CaAsO 2OH•½H 2O) and arsenates (i.e. Ca 5(AsO 4) 3OH) were precipitated and deposited as aggregates in the pores of biochars. Arsenite was only slightly precipitated under acidic conditions (pH = 4.5) while no arsenite was precipitated under alkaline conditions (pH = 9.5). Arsenite desorption from wood biochar was lowest at pH 6.5 indicating that wood biochar was able to retain a large quantity of the precipitates formed at pH 6.5 compared to pH 4.5 and pH 9.5. Given that the removal of As(III) from solution is often challenging and that biochar modification invites additional cost, the study demonstrated that low cost unmodified biochar can be effective in enhancing the removal of As(III) from the environment through Ca–As precipitation.

Item Type: Article
Uncontrolled Keywords: arsenic pollution,biochar,arsenate,precipitation,ph,toxicology,pollution,health, toxicology and mutagenesis ,/dk/atira/pure/subjectarea/asjc/3000/3005
Faculty \ School: Faculty of Science > School of Environmental Sciences
Related URLs:
Depositing User: LivePure Connector
Date Deposited: 04 Dec 2021 01:41
Last Modified: 01 Feb 2022 12:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/82538
DOI: 10.1016/j.envpol.2021.118241

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