Control of chlorite and chlorate in drinking water using surfactant-modified activated carbon

Abstract

Disinfection of drinking water is a fundamental step towards the protection of public health. Particularly, chlorine dioxide is one of the most important disinfection methods applied in public water systems. However, some unwanted and potentially toxic by-products (chlorite-ClO2- and chlorate-ClO3-) can be generated during this process. Thus, the European Union (EU) has recently set a permissible maximum concentration of 0.25 mg⋅L-1 for both ClO2- and ClO3- in the water intended for human consumption. Nevertheless, the existent strategies proposed for the elimination of these oxyanions present important limitations for their large-scale application. Here, we propose the ClO2- and ClO3- adsorption by two granulated activated carbons modified with five different alkyl quaternary ammonium-based surfactants, exhibiting a large affinity for inorganic anions. A granulated activated carbon modified with hexadecylpyridinium chloride monohydrate (CPC@CAG1) was selected as the most efficient adsorbent, achieving an excellent oxyanions removal (≥99 and 80 ± 0.5% of ClO2- and ClO3- in only 2 h, respectively). Finally, the ClO2- and ClO3- elimination was evaluated using a continuous flow under realistic conditions (drinking water from a real treatment plant and 12 min empty bed contact time (EBCT)), reaching a very high oxyanions removal efficacy for 4 cycles of 160 h-each, thus envisioning the future real application of this adsorbent in water disinfection treatments.