Heavy metal content in sediments is of serious concern since sediments may act as carriers and secondary sources for contaminants in the marine environment.
Mercury (Hg) is a highly toxic and ‘possibly carcinogenic to humans’ element, arsenic (As) is a carcinogenic and toxic metalloid.
In this recent work, a remediation method was developed to clean marine sediments contaminated by As and Hg.
The method consists of four steps:
- 1) washing with sodium hydroxide (NaOH) to remove metals associated with humic acid;
- 2) Fenton-reaction using alpha-cyclodextrin (ACD) to stabilise Fe(II) at natural pH and oxidise As (III) and Hg (0 or I);
- 3) complexation reaction with ACD;
- 4) complexation with sodium sulfide (Na2S) to remove Hg as soluble Hg-polysulfides.
Conclusions: compared to other remediation experiences in literature, this technique provides the best removal efficiency for As and Hg (ranging between 26 -71 % and 57–95 %, respectively). Considering these results, another work is in progress to evaluate the up-scaling of this remediation method, using a soil washing plant with a treatment capacity of 1 ton of sediment per hour and also looking at the economic feasibility.
Read more:
Fabio D’Agostino, Antonio Bellante, Maria Bonsignore, Marianna Del Core, Laura Clarizia, Nadia Sabatino, Luigi Giaramita, Giorgio Tranchida, Salvatore Chiavarini, Mario Sprovieri (2023) A chemical remediation technique for a nearly-total removal of arsenic and mercury from contaminated marine sediments. Helyon 9, E22633. doi: 10.1016/j.heliyon.2023.e22633