Lan Huong Tran

Simultaneous removal of Cu and PAHs from dredged sediments using flotation

PurposeThis study addresses the feasibility of a flotation technique, using a lab-scale flotation cell, to simultaneously remove both metals and polyaromatic hydrocarbons (PAHs) from fine sediment fractions (<250xa0μm) that are potentially contaminated with copper (Cu).Materials and methodsA multiple flotation process with three consecutive flotation stages was performed on three sediments (13S, 14B, and 24A) with different particle size distributions, Cu and PAH concentrations, and organic matter contents.Results and discussionFlotations performed under selected conditions allowed for significant removal of both Cu (61–70xa0%) and PAHs (75–83xa0%) with acceptable froth recoveries of approximately 23–29xa0%. Removal rates for arsenic, lead, and zinc were 48–61, 40–48, and 32–36xa0%, respectively. Flotation selectivity of Cu was greatly influenced by the contents of fine particles and organic matter of the sediments. The maximum flotation selectivity was obtained for the 53–125-μm size fraction. The high flotation selectivity of Cu (2.5–3.2) and PAHs (3.0–3.6) demonstrated the feasibility of flotation to treat soils or sediments containing both organic and inorganic pollutants.ConclusionsOverall, the flotation results showed a high selectivity for both Cu and PAHs and demonstrated the feasibility of flotation to treat media contaminated with organic and inorganic contaminants.

Degradation of polycyclic aromatic hydrocarbons in different synthetic solutions by Fenton’s oxidation

ABSTRACT The Fenton oxidation using phenanthrene (Phe), fluoranthene (Fle) and benzo[a]pyrene (BaP) as representative polycyclic aromatic hydrocarbon (PAH) contaminants was examined. The effect of the H2O2 concentration, the temperature and the competition between the PAHs in different solutions (methanol, surfactant and quartz) was investigated. The Fenton oxidation process was performed at pHu2009=u20092.5. The best conditions were recorded by adding 15u2005g H2O2 L− 1 with a molar H2O2/Fe2+ ratio of 10/1 at Tu2009=u200960°C. Phe, Fle and BaP were efficiently degraded in aqueous solution (Pheu2009=u200999%, Fleu2009=u200999% and BaPu2009=u200990%). The present study demonstrated that Phe, Fle and BaP were degraded to intermediate compounds and also oxidized to carbon dioxide. Among the by-products obtained, phthalic acids and benzoic acid were recorded as the major products.

Remediation of Contaminated Dredged Sediments Using Physical Separation Techniques

Physical separation processes constitute a cost-effective approach to remediate contaminated sediments. A laboratory-scale physical separation process using froth flotation, Wilfley table (WT), and physical separation column (PSC) as the key unit operations was studied using Sandy Beach sediments (Gaspé, Canada) contaminated with metals, mainly copper (Cu), and polycyclic aromatic hydrocarbons (PAHs). Copper was distributed (89-96%) mainly in the fractions <250 μm, whereas PAHs were mainly in the sand, coarse particles, and gravel. Froth flotation was found to be effective for separating both Cu and PAHs simultaneously from fractions < 250 μm. WT (0.25-2 mm) and PSC (> 2 mm) were more effective for PAH removal than Cu removal. Overall, the treatment process resulted in a cleaned sediment recovery of 74-75% (w/w) with the following pollutants removed: 71-80% PAHs, 61-65% Cu, 27-33% Zn, and 36-40% Pb.

Polycyclic Aromatic Hydrocarbon Oxidation from Concentrates Issued from an Attrition Process of Polluted Soil Using the Fenton Reagent and Permanganate

This study was conducted to determine the optimal conditions for PAH degradation from highly contaminated attrition sludge (PAC) using a Fenton process or successive permanganate (KMnO4) oxidation and Fenton processes. The following parameters were studied to optimize the Fenton oxidation process: the amounts of reactants based on the stoichiometric oxidant demand (SOD), the reactant addition protocol and number of doses, and the solid/liquid ratio (S/L). The results showed that the following conditions were optimum: TSu2009=u200930%, 7.5 times SOD, H2O2/Fe2+ ratiou2009=u200910, and added five times during 60xa0min, which allowed the degradation of 43% of total 27 PAHs from the PAC. Successive Fenton and KMnO4 oxidation processes were also tested. PAH degradation using a sequential Fenton process followed by KMnO4 oxidation (or KMnO4 followed by Fenton) was higher than for the use of Fenton or KMnO4 treatment alone. Up to 71% of the total 27 PAHs were degraded when using a combination of both processes. It appeared that the sequential treatment is a viable method for the significant degradation of 27 PAHs from PAC (t valueu2009>u20092.77).

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 The objective of this study was to evaluate, at a pilot scale, the performance of an attrition process for removing As, Cr, Cu, pentachlorophenol (PCP) and polychlorodibenzodioxins and furans (PCDDF) from a 1-4 mm soil fraction. A Box-Behnken experimental design was utilized to evaluate the influence of several parameters (temperature, surfactant concentration and pulp density) and to optimize the main operating parameters of this attrition process. According to the results, the concentration of surfactant (cocamidopropylbetaine-BW) was the main parameter influencing both PCP and PCDDF removal from the 1-4 mm soil fraction by attrition. The behavior of each 2,3,7,8-PCDD/F congener during the attrition process was studied. The results indicated that the concentration of surfactant had a significant and positive effect on the removal of almost all of the dioxin and furan. The removal of 56%, 55%, 50%, 67% and 62% of the contaminants were obtained for As, Cr, Cu, PCP and PCDDF, respectively, using the optimized conditions ([BW]= 2% (w.w−1), T = 25°C and PD = 40% (w.w−1)). These results showed that attrition in the presence of a surfactant can be efficiently used to remediate the coarse fractions of soil contaminated by As, Cr, Cu, PCP and PCDDF.

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

The objective of this study was to evaluate the influence of the soil parameters (particle size, initial contamination level, etc.) on the performances of an attrition process to remove As, Cr, Cu, pentachlorophenol (PCP) and dioxins and furans (PCDD/F). Five different contaminated soils were wet-sieved to isolate five soil fractions (<u20090.250, 0.250–1, 1–4, 4–12 and >u200912xa0mm). Five attrition steps of 20xa0min each, carried out in the presence of a biodegradable surfactant ([BW]u2009=u20092%, wxa0w−1) at room temperature with a pulp density fixed at 40% (wxa0w−1), were applied to the coarse soil fractions (>u20090.250xa0mm) of different soils. The results showed good performances of the attrition process to simultaneously remove PCP and PCDD/F from contaminated soil fractions initially containing between 1.1 and 13xa0mg of PCPxa0kg−1 (dry basis) and between 1795 and 5720xa0ng TEQ of PCDD/Fxa0kg−1. It appeared that the amounts of contaminants removed were significantly correlated (p valueu2009<u20090.05, R2u2009=u20090.96) with the initial amounts of PCP and PCDD/F, regardless of the particle size of the soils studied. The nature of the soil (granulometric distribution, pH, total organic carbon (TOC) (organic matter) and diverse industrial origin) slightly and negatively influenced the efficiency of organic contaminants removals using attrition. However, the attrition treatment allowed an efficient removal of both PCP and PCDD/F from the coarse fraction of contaminated soil, despite the nature of the soil.

Optimization of PAHs Oxidation from a Concentrate of Soil Attrition Using Potassium Permanganate

ABSTRACT The treatment of soils contaminated with organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), by attrition produced large amounts of highly concentrated attrition sludge (PAH – attrition concentrate – PAC). This paper studied the performance of an oxidation process using potassium permanganate (KMnO4) to degrade PAHs that were initially present in attrition concentrates. The influence of operating conditions (temperature, concentration of KMnO4 and reaction time) was studied, and these parameters were optimized using a response surface methodology (RSM). The results showed that the temperature and the reaction time had a significant and positive effect on the degradation of PAHs for the experimental domain studied (temperature between 20 and 60°C and reaction time between 1 and 7 h). The interaction between the temperature and the concentration of KMnO4 significantly influenced the degradation of the PAHs. The temperature and the concentration of KMnO4 were the main parameters that influenced the degradation of both phenanthrene (Phe) and benzo [a] pyrene (BaP). For benzo [a] anthracene (BaA), the temperature was the most influential factor. According to our results, the optimal conditions were defined as [KMnO4] = 0.4 M for 5.5 h at 60°C. These optimal conditions led to degradations of 42.9%, 40.8%, 41.0% and 46.0% of the total PAHs, Phe, BaA and BaP, respectively.

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.