Removal of adsorbable organic halides from wastewater: A review of advanced chemical and electrochemical processes

To overcome the current limitations of conventional technologies for removing adsorbable organic halides (AOX) from wastewater, advanced chemical and electrochemical processes are attracting interest. This work aims to systematically review the latest findings for the removal of AOX compounds from wastewater, discussing the current main gaps and proposing possible tips for future research. Fenton and photo-Fenton, photocatalysis coupled with biological systems, and reductive processes showed encouraging results with up to 98%, 95%, and 75% of AOX mineralization, respectively. The analysis also highlighted that the studies were mainly carried out on real wastewater, but, except for Fenton and photo-Fenton, lab scale conditions are often far from the realistic ones, representing a huge gap. In all studies, a very low amount of volume has been used with significant concerns about the reliability of results in case of full-scale applications. For these reasons, the promising outcomes of chemical and electrochemical technologies for AOX removal should be fully validated before a possible application on real industrial and municipal wastewater treatment plants. In case of reductive processes, the reduction of approximately half of the AOX present in the wastewater needs days, which is not compatible with large-scale application. Moreover, more studies are also needed to understand the actual toxicity of the treated effluent to estimate the potential detrimental effect of by-products generated during the treatment. These results can be useful both for the scientific community and technical stakeholders to stimulate the scientific debate and increase awareness of these new approaches for AOX removal.