Work

Chelating, Reducing, and Adsorbing Agents in Geopolymers for Heavy Metals Stabilization from Galvanic Sludge

Year: 2025

Type: article

Abstract: Hazardous galvanic sludge waste (GSW) from the electroplating industry, produced at 100,000–150,000 tonnes/year in the EU and containing high concentrations of Cr and Ni was successfully treated using metakaolin-based geopolymers via Stabilization/Solidification (S/S). The experimental design incorporated chelating (sodium diethyl dithio carbamate, C5H10NS2Na, DTC), reducing (sodium sulfide, Na2S), and adsorbing (hydroxyapatite, Ca5(PO4)3(OH), Hap) agents separately to improve heavy metal immobilization. The results demonstrated that Na2S drastically decreased Cr release by −98.7% by reducing mobile Cr(VI) to insoluble Cr(III). DTC reduced Ni leaching by −93.4%, forming sparingly soluble Ni(II)(DTC)2 complexes that precipitated within the matrix. Hap enhanced Ni retention by 55.5% via cation exchange but was ineffective for Cr due to electrostatic repulsion with the anion Cr(VI)O42− at the geopolymer’s high pH. This work is the first to apply geopolymerization coupled with these chemical agents for S/S of as-received galvanic waste, offering a highly efficient, low-carbon strategy to manage this hazardous industrial residue.

Source: Polymers

DOI: 10.3390/polym18010028

Authors: Francesco Genua, Mattia Giovini, Cristina Leonelli, Isabella Lancellotti

Institution: University of Modena and Reggio Emilia

Language: English

Topic: Recycling and utilization of industrial and municipal waste in materials production

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDG: Responsible consumption and production

Open Access status: gold

Estimated APC paid: $3,258