Decontamination of metals and polycyclic aromatic hydrocarbons from slag-polluted soil

Abstract

Metallurgy is an industrial activity that is one of the largest contributors to soil contamination by metals. This contamination is often associated with organic compound contamination; however, little research has been aimed at the development of simultaneous processes for decontamination as opposed to treatments to heavy metals or organic compounds alone. This paper presents an efficient process to decontaminate the soils polluted with smelting by-products rich in Cu, Zn and polycyclic aromatic hydrocarbons (PAHs). A simultaneous treatment for metals and PAHs was also tested. The process is mainly based on physical techniques, such as crushing, gravimetric separation and attrition. For the finest particle size fractions, an acid extraction with H2SO4 was used to remove metals. The PAH removal was enhanced by adding surfactant during attrition. The total metal removals varied from 49% to 73% for Cu and from 43% to 63% for Zn, whereas a removal yield of 92% was measured for total PAHs. Finally, a technical-economic evaluation was done for the two processes tested.

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

“…Over the past several decades, several authors have studied physical and chemical decontamination processes to evaluate their ability to simultaneously remove inorganic and organic compounds from solid matrices, including soils (Riveiro-Huguet and Marshall, 2011;Bisone et al, 2013a;Reynier et al, 2013a, b;Guemiza et al, 2016;Metahni et al, 2016). The attrition uses high-intensity agitation to remove films around soil particles and/or to detach fine particles from the surface of coarse particles, resulting in the release of contaminants.…”

“…The attrition process is governed by the physical contact between the contaminated particles themselves, the contact between the contaminated particles and the liquid phase, and the walls and the impellers present in the mixing reactor, which favor the removal of the fine particles that contain the contaminants. As most of the contaminants present in soil usually have low water solubility, such additives as acids, alkaline agents, surfactants and/or chelating agents are often added into the attrition pulp to improve the removal of both inorganic (e.g., As, Cr, Cu, Pb, and Zn) and organic compounds (e.g., PAHs, PCP, and PCDDFs) (Riveiro-Huguet and Marshall, 2011;Bisone et al, 2013a;Reynier et al, 2013b;Guemiza et al, 2016;Metahni et al, 2016). Surfactants are compounds that contain both hydrophilic and hydrophobic parts in their molecular structure.…”

“…Attrition processes may be used with or without a surfactant to remove organic compounds (e.g., PCP and PCDDF) from contaminated soils. The attrition process performed by Bisone et al (2013a) that used a surfactant ([cocamidopropyl hydroxysultaine, CAS] = 0.2 g L -1 ) achieved a removal of more than 90% of PAHs from contaminated soil. The decontamination process developed by Veetil et al (2014) consisted of froth flotation (fractions < 250 µm), a Wilfley table (0.250-2 mm) and a physical separation column preceded by an attrition step as pretreatment (> 2 mm).…”

Dual Soil Decontamination Procedures

“…"lais process is mainly based on physical techniques, such as crushing, gravimetric separation and atrition. In another such study, "lais team demonstrated that it is possible to atain removal eiciencies of 4 3% for Cu and from 43 to 63% for Zn, whereas a removal yield of 2% was measured for total P"Hs [40,41]. The results were improved replacing cocamidopropyl betaine with cocamidopropyl hydroxysultaine (up to 0% P"Hs and Pb removal, in three diferent polluted soil types) [42].…”

Removal of chlorinated pesticide contamination by soil washing with sole water

“…Effectiveness of most of them has been reported only at laboratory scale while containment or immobilisation is extensively practised [6]. Soil washing has drawn attention for its successful implementation in presence of organic [7] and inorganic [8] contaminants even mixed together [9]. Its limited environmental impact in terms of greenhouse gas emissions in comparison with other soil remediation treatments has been pointed out as additional benefit [10].…”