Decontamination of metals, pentachlorophenol, and polychlorined dibenzo-p-dioxins and dibenzofurans polluted soil in alkaline conditions using an amphoteric biosurfactant

Abstract

In this paper, flotation in acidic conditions and alkaline leaching soil washing processes were compared to decontaminate four soils with variable contamination with metals, pentachlorophenol (PCP), and polychlorodibenzo dioxins and furans (PCDD/F). The measured concentrations of the four soils prior treatment were between 50 and 250 mg/kg for As, 35 and 220mg/kg for Cr, 80 and 350mg/kg for Cu, and 2.5 and 30mg/kg for PCP. PCDD/F concentrations reached 1394, 1375, 3730, and 6289ng/kg for F1, S1, S2, and S3 soils, respectively. The tests were carried out with masses of 100g of soil (fraction 0-2 mm) in a 2 L beaker or in a 1 L flotation cell. Soil flotation in sulphuric acid for 1 h at 60 degreeC with three flotation cycles using the surfactant cocamidopropyl betaine (BW) at 1% allows the solubilization of metals and PCP with average removal yields of 85%, 51%, 90%, and 62% for As, Cr, Cu, and PCP, respectively. The alkaline leaching for 2 h at 80 degreeC solubilizes As, Cr, Cu, and PCP with average removal yields of 60%, 32%, 77%, and 87%, respectively. Tests on PCDD/F solubilization with different surfactants were carried out in combination with the alkaline leaching process. PCDD/F removal yields of 25%, 72%, 70%, and 74% for F1, S1, S2, and S3 soils, respectively, were obtained using the optimized conditions.

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

“…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.…”

Influence of Soil Parameters on the Efficiency of the Attrition Process to Remove Metals, PCP, Dioxins and Furans from Contaminated Soils

“…In addition, the presence of organic matter (humic and fulvic acids), metallic oxides (iron, aluminum or manganese oxides) can immobilize the contaminants into the soil, especially inorganic contaminants (Banerji et al 1993). According to several authors, As, Cr, Cu, PCP, and PCDD/F are strongly fixed to the organic matter or/and to metal oxides present in the soil, indicating that the efficiency of the decontamination process might be influenced by the nature of the soil (amount of organic matter or metal oxides) (Banerji et al 1993;Reynier et al 2013;UK Environment Agency 2009). According to the study carried out Metahni et al (2016), it appeared that the performance of an attrition process to remove PCDD/F from the coarse soil fractions (> 0.125 mm)…”

Treatment of contaminated soil leachate by precipitation, adsorption and ion exchange

“…For the DF, the removal yields ranged from 25 to 74% 20 depending on the nature of the soil and the initial contaminant 21 levels. According to the authors, the alkaline leaching process can 22 be successfully used to remove inorganic and organic contami- 23 nants from polluted soils due to its efficiency and the low operating 24 costs [6]. However, this leaching process generates large amounts 25 of alkaline effluents with concentration of As, Cr, Cu, PCP and DF 26 higher than the regulations for the discharge of effluents in sewers 27 [7,8].…”

“…Among the 11 chemical decontamination processes developed, the solubilization 12 of As, Cr, Cu, PCP and DF using alkaline solutions and a bio- 13 surfactant seemed to be very promising in terms of contaminant 14 removal efficiencies and operational costs. Indeed, Reynier et al [6] 15 highlighted that more than 60% of As, 32% of Cr, 77% of Cu and 87% 16 of PCP can be removed from contaminated soils after 3 leaching 17 steps of 2 h each carried out at 80 C with a pulp density fixed at 18 10% in the presence of sodium hydroxide (0.5 M) and a surfactant 19 ([BW] = 2%). For the DF, the removal yields ranged from 25 to 74% 20 depending on the nature of the soil and the initial contaminant 21 levels.…”