Enhanced photoelectrocatalysis for oxidation of organic pollutants and metal recovery from polluted water and sediments

Sediments often contain a complex mixture of organic and inorganic pollutants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), aliphatic and aromatic hydrocarbons, phthalates, tributyltin (TBT), and metals. Since large quantities of contaminated sediments are regularly dredged, it is necessary to develop methods to simultaneously treat the different contaminants. These techniques should also handle complex sediment matrices where pollutants may be strongly bound, e.g., TBT in paint flakes and PAHs in tire particles. This work has focused on the development of photoelectrocatalytic (PEC) processes to degrade organic pollutants (OPs) and simultaneously recover metals from marine, brackish and stormwater sediments. The remediation efficiencies were studied in real contaminated sediments and clear water solutions spiked with PAHs, PCBs, TBT, and metals. In spiked water, PEC yielded a > 99 % reduction of PAHs, PCBs, and TBT, and recovered 76 % of copper. The pollutant removal from the sediments by PEC was less efficient, especially for PAHs in stormwater sediment. However, the combination of PEC and H₂O₂ reduced other groups of OPs: TBT by 91 %, PCB by 82 %, and phthalates DINP and DEHP by 98 % and 85 %, respectively. The release of pollutants from sediments into the water phase is the key to successful PEC application.