Work

Sequential washing vs. thermal treatment: heavy metal management in soil-like material derived from landfills

Year: 2025

Type: article

Abstract: Landfill mining generates large quantities of potentially contaminated soil-like material (SLM) that require treatment before reuse. While most earlier studies have emphasized the characterization and valorization of SLM, the present study focuses on the critical need for contaminant reduction (predominantly heavy metals) to enable its safe off-site reuse. This study compares two cost-effective methods: sequential washing with ultrapure water and low-temperature thermal treatment (ranging from 60 °C to 500 °C), specifically targeting the mobilization and immobilization behaviour of heavy metals commonly found in landfill environments. Sequential washing with ultrapure water significantly reduced the leachable fractions of As, Cr, Co and Ni, with most metals showing a substantial reductions after the first one or two wash cycles, except for Pb. In contrast, thermal treatment at 300 °C resulted in increased mobilization of Co, Cr, Mn, and Ni, while treatment at 500 °C was more effective for immobilizing Cu and Pb. A comparative analysis revealed that seven successive washings were more effective than thermal treatment at 300 °C in mobilizing Cu, Zn, As, Pb, and Cd, whereas thermal treatment was better at immobilizing Cu and Pb. The findings of the study suggest that the choice of treatment should be guided by the target metal and the desired outcome – whether mobilization for removal or immobilization for stabilization. • Reasonable reduction of heavy metals required 5 washings with ultrapure water. • Thermal treatment at 300 °C most effectively mobilized the heavy metals. • A temperature of 500 °C effectively immobilized heavy metals, except Cr. • Concentrations of leachate hardly complied with groundwater standards.

Source: Journal of Environmental Management

DOI: 10.1016/j.jenvman.2025.127833

Authors: Ingo Hölzle, Mohit Somani, G.V. Ramana, Manoj Datta, Peter Fiener

Institutions: University of Augsburg, Indian Institute of Technology Delhi, Indian Institute of Technology Bhubaneswar

Language: English

Topic: Landfill Environmental Impact Studies

Subfield: Waste Management and Disposal

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $3,750