Issue 8, 2020

Chemical regeneration of granular activated carbon: preliminary evaluation of alternative regenerant solutions

Abstract

Granular activated carbon (GAC) is used in drinking water treatment plants worldwide to remove micro-pollutants such as pesticides. Early breakthrough of problematic micro-pollutants leads to frequent and costly thermal regeneration off-site. A potential alternative approach is to chemically regenerate GAC on-site (possibly in situ) with an appropriate solution capable of desorbing organic contaminants, having a range of physico-chemical properties. In this study, four types of regenerant solution were evaluated in batch tests for their ability to desorb five target contaminants. The solutions were: high purity water, sodium hydroxide, ethanol, and a mixture of sodium hydroxide and ethanol. The contaminants included: phenol and nitrobenzene, as representative aromatic compounds; clopyralid and metaldehyde, as poorly-adsorbed pesticides; and isoproturon, a well-adsorbed pesticide. Among the properties of the contaminants, their hydrophobicity and aqueous solubility had the most significant influence on the desorption efficiency. NaOH/CH3CH2OH was found to be more effective than individual solutions in desorbing the target contaminants, indicating an ability to desorb both hydrophobic and hydrophilic compounds. The NaOH/CH3CH2OH regenerant solution yielded desorption efficiencies in the range of approximately 40–90%, with the efficiency dependent on the contaminant. A thermodynamic study provided valuable fundamental information regarding the adsorption and desorption mechanisms, and the existence of two binding sites involving a weak physisorption and a stronger chemisorption-like interaction between the contaminants and the GAC.

Graphical abstract: Chemical regeneration of granular activated carbon: preliminary evaluation of alternative regenerant solutions

Supplementary files

Article information

Article type
Paper
Submitted
08 Apr 2020
Accepted
12 Jun 2020
First published
15 Jun 2020
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Water Res. Technol., 2020,6, 2043-2056

Chemical regeneration of granular activated carbon: preliminary evaluation of alternative regenerant solutions

A. Larasati, G. D. Fowler and N. J. D. Graham, Environ. Sci.: Water Res. Technol., 2020, 6, 2043 DOI: 10.1039/D0EW00328J

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