Optimizing removal of arsenic, chromium, copper, pentachlorophenol and polychlorodibenzo-dioxins/furans from the 1–4 mm fraction of polluted soil using an attrition process

Abstract

8The objective of this study was to evaluate, at a pilot plant scale, the performance of an attrition 9 process for removing As, Cr, Cu, pentachlorophenol (PCP) and polychlorodibenzodioxins and 10 furans (PCDDF) from a 1-4 mm soil fraction. Once optimized, this attrition process would be 11 applied to the coarse fractions (> 0.250 mm) whereas the fine particles might be treated using a 12 chemical leaching process. The tests were carried out on 2 kg of soil (fraction 1-4 mm) in a 10 L 13 stainless reactor, using tap water. A Box-Behnken experimental design was utilized to evaluate 14 the influence of several parameters (temperature, surfactant concentration and pulp density) and 15 to optimize the main operating parameters of this attrition process. According to the results, the 16 concentration of surfactant (cocamidopropylbetaine-BW) was the main parameter influencing 17 both PCP and PCDDF removal from the 1-4 mm soil fraction by attrition. The behavior of each 18 dioxin and furan congener during the attrition process was studied. The results indicated that the 19 concentration of surfactant had a significant and positive effect on the removal of almost all of 20 the dioxin and furan. The removal of 56%, 55%, 50%, 67% and 62% of the contaminants were 21 obtained for As, Cr, Cu, PCP and PCDDF, respectively, using the optimized conditions ([BW] = 22 2% (w.w -1 ), T = 25°C and PD = 40% (w.w -1 )). These results showed that attrition in the presence 23 of a surfactant can be efficiently used to remediate the coarse fractions of soil contaminated by 24As, Cr, Cu, PCP and PCDDF. 25 26

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

“…During this study, the attrition steps were conducted in a 10-L stainless reactor equipped with internal baffles with 2 kg of the 1-4-mm J3 soil fraction. Five attrition steps were performed under the optimized operating conditions defined by Guemiza et al (2016): tap water, pulp density (PD) = 40% (w.w -1 ), [BW] = 2% (w w -1 ), t = 20 min, T = 20°C, mixing speed = 1,700 rpm. The pulp was shaken using a mechanical stirrer (Light EV1 P25, AXFLOW, New York, NY, USA) equipped with a stainless steel axial propeller (6 cm diameter) at 1,700 rpm.…”

“…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.…”

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

“…This decrease of performances may be due to the fact that the slurry becomes too dense, which decreases the inter-particle motion and the scrubbing action. Recently, Guemiza et al (2016) used an experimental design methodology to evaluate the effect of pulp density in the range of 20 to 40% (w.w -1 ) on the removal of PCP and PCDD/F from the 1-4 mm fraction of a contaminated soil using attrition. Their results showed that a high pulp density is more efficient for the removal of both contaminants.…”

“…Attrition was found to be an efficient technique (INRS-Georessources & CRM 1997). This technique can be used as a physical decontamination process alone (Bayley et al 2005;Bisone et al 2013;Guemiza et al 2016;Metahni et al 2016;Stražišar and Sešelj 1999) as well as a step prior to other decontamination processes such as gravity concentration and froth flotation (Bisone et al 2012;Jobin et al 2015Jobin et al , 2016Veetil et al 2014;Williford et al 1999). Attrition scrubbing allows friction between contaminated particles; enhancing the removal of the thick films around soil particles and/or the detachment of fine particles usually contaminated from the surface of the coarse particles (uncontaminated).…”