A Green Chemical Remediation Process Achieving 71% Arsenic and 95% Mercury Extraction from Marine Sediments for Safe Reuse

Prolonged coastal industrialization has generated persistent pollution in many marine zones, making restoration actions necessary to eliminate hazardous inorganic contaminants. This study introduces a clean-up strategy tailored for marine sediments enriched with arsenic (As) and mercury (Hg). The approach is suitable for movable treatment units and is intentionally designed to reduce secondary impacts on the environment. The procedure was evaluated on two laboratory-spiked sediments and on two field materials originating from highly impacted regions in southern Italy—Augusta Bay and the Gulf of Bagnoli—known for elevated Hg and As levels, respectively.
The workflow integrates four sequential operations: alkaline washing with sodium hydroxide (NaOH) to release metals interacting with humic substances; a Fenton system in which α-CycloDextrin (aCD) stabilizes Fe(II) at natural pH and promotes oxidation of As(III) and Hg(0/I); a complexation step involving aCD; and a final treatment with sodium sulfide (Na₂S) to convert Hg into soluble polysulfide complexes. Relative to other approaches described in the literature, this method yields superior extraction efficiencies for both As and Hg, achieving 26–71 % and 57–95 % removal, respectively. Based on the remaining concentrations and the regulatory thresholds imposed by European directives for reuse, the processed sediment can be reintroduced into various civil or industrial applications. The proposed protocol aligns with circular-economy principles, limits further contamination, conserves natural resources, and facilitates the productive reuse of remediated matrices (sediments, soils, and aqueous phases), thereby reducing landfill disposal.