Feasibility of combining biological hydrogel reactive filter media with electrokinetic for sustainable site remediation

The feasibility of electrokinetic (EK) for single and multiple heavy metals removal was investigated with and without a kappa carrageenan (kC) hydrogel reactive filter media (RFM) for a sustainable remediation process. Natural biodegradable polysaccharide kC hydrogel exhibits strong adsorption capacity, allowing the capture of heavy metal contaminants. Optimization tests confirmed that 4 % kC RFM performs better than 5 % and 6 % kC RFMs, achieving 84 % copper removal by the EK process. Then, the 4 % kC was crosslinked with 2 % glutaraldehyde (GD) to maximize the RFM adsorption capacity as well as impede the advancement of the alkaline front in the soil. Integrating the kC-GD hydrogel RFM in the EK system achieved, in two weeks, a 96.62 % removal of copper, 93.98 % removal of nickel, and 99.98 % removal of zinc. SEM and EDX analysis confirmed the adsorption of heavy metals by the kC-GD RFM. In the multiple heavy metals decontamination test with RFM-EK, results showed preferential removal of zinc and nickel at 99.97 % and 99.86 %, while copper removal was about 93.38 %. Density functional theory (DFT) simulation showed binding energies of 341.1, 545.7, and 106.0 kJ/mol for Cu²⁺, Zn²⁺, and Ni²⁺, revealing a notable discrepancy between theoretical and experimental results. This discrepancy is caused by copper-limited diffusion through the hydrogel and the dynamic variations in the soil pH during the EK process. Therefore, integrating computational and experimental approaches is recommended when designing responsive hydrogel-based sorbents for heavy metal remediation.