Counter-Current Attrition Process (CCAP) to Remove Metals, Pentachlorophenol (PCP), Dioxins and Furans (PCDDF) from the 1-4-mm Fraction of Contaminated Soil

ABSTRACT

The objective of this study was to evaluate the potential of a counter-current attrition process (CCAP) over 15 cycles for removing metals, pentachlorophenol (PCP) and polychlorinated dibenzo-p-dioxins and -furans (PCDDF) from contaminated soil. The CCAP, applied to the 1–4-mm fraction of a contaminated soil, included five attrition steps (pulp density (PD) = 40% (w w⁻¹), surfactant [BW] = 2% (w w⁻¹), t = 20 min, T = 20°C) followed by one rinsing step. The water emerging from the first attrition step was treated using flocculation in the presence of 0.04 g CMX 123 (commercial flocculent) L⁻¹ before being reintroduced into the CCAP. The CCAP including the treatment of attrition wastewater (ATW) by flocculation achieved a removal of 44 ± 5% As, 26 ± 6% Cr, 24 ± 5% Cu, 49 ± 4% PCP and 45 ± 3% PCDDF. Moreover, the CCAP enabled a significant reduction (78%) in the amount of water required (around 14.5 m³ of water per ton of the 1–4-mm soil fraction). The high removal yields obtained after 15 attrition cycles of the CCAP for PCP and PCDDF and the significant reduction of water consumption confirm that this CCAP can be considered for industrial applications.

KEYWORDS:

• Attrition
• Counter-current
• Contaminated soil
• Pentachlorophenol
• Polychloro-dibenzodioxins and furans
• Metals

Acknowledgments

This work was supported by the Natural Sciences and Engineering Research Council of Canada and IREQ under grant RDC 463019–14. The authors thank Myriam Chartier for her assistance.