A trithiocyanurate-based chelating agent for the stabilisation of lead in municipal solid waste incineration fly ash

The widespread incineration of municipal solid waste (MSW) has raised concerns regarding environmental pollution caused by the hazardous heavy metal lead (Pb) in fly ash (FA), necessitating safe treatment prior to landfill disposal. This study developed a novel organic chelating agent-TA (The chelating agent is named as an acronym derived from the two primary monomers), a trithiocyanuric acid-functionalized allylthiourea macromolecule, and evaluated its effectiveness in stabilising Pb in municipal solid waste incineration fly ash (MSWI-FA). Compared to conventional organic chelating agents such as dithiocarbamates (DTC), TA presents an environmentally superior alternative by eliminating the use of highly volatile and hazardous CS₂ (Carbon disulfide) as a raw material. The addition of 4 wt% (Weight Percentage) TA successfully reduced the leaching concentration of Pb from fly ash to a level below the Chinese landfill regulatory limit. This reduction was primarily attributed to the stabilisation treatment significantly decreasing the acid-extractable fraction of Pb from 12.845% to 3.79%. Furthermore, the TA treatment also facilitated the reduction of Pb (IV) to the more stable Pb²⁺, contributing to the overall enhanced stability and reduced environmental risk.HIGHLIGHTSA novel macromolecular chelator (TA) was synthesised from trithiocyanuric acid and allylthiourea for lead(Pb) stabilisation.TA achieves efficient Pb immobilisation, reducing leaching concentration to 0.22 mg/L, meeting Chinese landfill standards.The stabilisation mechanism involves the reduction of Pb (IV) to Pb²⁺ and the formation of a tetrahedral structure through chelation of lead by TA, as evidenced by XAFS and XPS analysis.TA converts acid-extractable Pb into stable oxidisable and residual fractions, significantly lowering environmental risk.