Co-Fermentation of Agri-Food Residues Using a Co-Culture of Yeasts as a New Bioprocess to Produce 2-Phenylethanol.

Whey is a dairy residue generated during the production of cheese and yogurt. Whey contains mainly lactose and proteins, contributing to its high chemical oxygen demand (COD). Current environmental regulations request proper whey disposal to avoid environmental pollution. Whey components can be transformed by yeast into ethanol and biomolecules with aroma and flavor properties, for example, 2-phenyethanol (2PE), highly appreciated in the industry due to its organoleptic and biocidal properties. The present study aimed to valorize agri-food residues in 2PE by developing suitable bioprocess. Cheese whey was used as substrate source, whereas crab headshells, residual soy cake, and brewer's spent yeast (BSY) were used as renewable nitrogen sources for the yeasts Kluyveromyces marxianus and Debaryomyces hansenii. The BSYs promoted the growth of both yeasts and the production of 2PE in flask fermentation. The bioprocess scale-up to 2 L bioreactor allowed for obtaining a 2PE productivity of 0.04 g2PE/L·h, twofold better productivity results compared to the literature. The bioprocess can save a treatment unit because the whey COD decreased under the detection limit of the analytical method, which is lower than environmental requirements. In this way, the bioprocess prevents environmental contamination and contributes to the circular economy of the dairy industry.

Optimization of metals and rare earth elements leaching from spent Ni-MH batteries by response surface methodology.

The rechargeable battery market has almost doubled in 15 years. Regardless of the type of batteries, their limited lifespan means that sooner or later they will constitute a mass of waste whose management is problematic as their content is high in elements and metals of high economic interest, but also toxic to the environment. This project is to optimize the solubilization conditions for rare earth elements (REEs) and other metals from waste nickel-metal hydride (Ni-MH) batteries. The Ni-MH battery powder used contained the following main elements: Ni (548 g/kg), La (45 g/kg), Co (32 g/kg), Zn (22 g/kg), Nd (15 g/kg), Sm (12 g/kg), and Ce (11 g/kg). The metals were solubilized in the presence of sulfuric acid. Acid concentration, solids concentration, leaching time, and temperature were optimized using the Box-Behnken design methodology. The optimal conditions identified are an H2SO4 concentration of 2 M, a S:L ratio of 10% (w:v), a leaching temperature of 60°C and a reaction time of 90 min. These conditions make it possible to solubilize 81% Ni, 99% Co, and 70% REEs, while the mathematical model predicted 83% Ni, 100% Co, and 80% REEs respectively. The process was also operated in counter-current leaching mode with the optimal parameters. The high solubilized yields obtained after five loops for all metals, REE and the significant reduction of water consumption confirm that this process leaching can be apply for industrial application.

Carbon dioxide sequestration by mineral carbonation via iron complexation using bipyridine chelating ligands.

An innovative mineral carbonation method was developed to synthesize iron(II) carbonate (FeCO3) by cation complexation using 2,2'-bipyridine as ligand. First, complexes of iron(II) and different ligands were theoretically analyzed and discounted in terms of their temperature and pH-dependent stabilities, iron-ligand interactions, possible by-products and difficulty of analysis, choosing 2,2'-bipyridine as the most suitable ligand. Then, the Job plot was used to verify the complex formula. The stability of [Fe(bipy)3]2+ at pH 1-12 was further monitored for 7 days using UV-Vis and IR spectroscopy. Good stability was observed between pH 3 and 8, decreasing within pH 9-12 where the carbonation reaction occurs. Finally, the reaction between Na2CO3 and [Fe(bipy)3]2+ was performed at 21, 60, and 80 °C and pH 9-12. The total inorganic carbon measured after 2 h shows that the best carbonate conversion (50%) occurred at 80 °C and pH 11, being the most suitable conditions for carbon sequestration. SEM-EDS and XRD were used to examine the effect of synthesis parameters on the morphology and composition of FeCO3. The FeCO3 particle size increased from 10 µm at 21 °C to 26 and 170 µm at 60 and 80 °C respectively with no pH dependence. In addition, EDS analysis supported the carbonate identity, whose amorphous nature was confirmed by XRD. These results would help prevent the iron hydroxide precipitation problem during mineral carbonation using iron-rich silicates. These results are promising for its application as a carbon sequestration method with a CO2 uptake of around 50% obtaining Fe-rich carbonate.

Sustainable applications of polyhydroxyalkanoates in various fields: A critical review.

PHA is one of the most promising candidates in bio-polymer family which is biodegradable and environment-friendly in nature. In recent years, it has been applied as a biodegradable alternative for petroleum-based plastic across different domains. In literature, several research groups have scrutinised the biocompatibility and biodegradability of PHA in both in vivo settings as well as in in vitro conditions. Microbial yield polyhydroxyalkanoates (PHAs) are promoted at present as biodegradable plastics. On the other hand, only a limited number of products is being commercially manufactured out of PHAs (e.g., bottles). A succession of microbes (prokaryotes in addition to eukaryotes) has been identified as potential candidates that can disintegrate PHAs. These materials have been successfully employed in packaging industry, medical devices and implants, moulded goods, paper coatings, adhesives, performance additives, mulch films, non-woven fabrics, etc. The present paper reviews and focuses on the potential applications of PHA and its derivatives in different industries.

A comprehensive review on current technologies for removal of endocrine disrupting chemicals from wastewaters.

In the recent years, endocrine disrupting compounds (EDCs) has received increasing attention due to their significant toxic effects on human beings and wildlife by affecting their endocrine systems. As an important group of emerging pollutant, EDCs have been detected in various aquatic environments, including surface waters, groundwater, wastewater, runoff, and landfill leachates. Their removal from water resources has also been an emerging concern considering growing population as well as reducing access to fresh water resources. EDC removal from wastewaters is highly dependent on physicochemical properties of the given EDCs present in each wastewater types as well as various aquatic environments. Due to chemical, physical and physicochemical diversities in these parameters, variety of technologies consisting of physical, biological, electrochemical, and chemical processes have been developed for their removal. This review highlights that the effectiveness of EDC removal is highly dependent of selecting the appropriate technology; which decision is made upon a full wastewater chemical characterization. This review aims to provide a comprehensive perspective about all the current technologies used for EDCs removal from various aquatic matrices along with rising challenges such as the antimicrobial resistance gene transfer during EDC treatment.

Behaviour of flotation tailings from a rare earth element deposit at high salinity.

Various rare earth element (REE) deposits hosted by carbonatite complexes have been identified in southern (Montviel, Niobec) and northern Quebec (Eldor deposit). During the winter in Quebec, the use of road salts to facilitate transportation on the mine site and/or avoid water freezing during mine operation may be necessary. The sources of salinity can be diverse on a mine site: process water, precipitation, alteration of minerals in the soil. Thus, tailings may come in contact with these salts and react. The purpose of the present study was to evaluate the impact of salinity on the behaviour of flotation tailings (Eldor deposit), i.e. the mobility of the elements contained in the tailings under these conditions and the environmental risks involved. For this purpose, leaching column tests were developed. The solutions were deionized water (CW column), NaCl (25 g/L; CS1 column) and CaCl2 (25 g/L; CS2 column). The leachate analysis revealed that the divalent cations (Ba, Cd, Mg, Mn, Sr, and Zn) are more mobile in the presence of CaCl2 (CaCl2 > NaCl > deionized water). The mobility of these elements appears to be governed by the competition with Ca2+ for tailings sorption sites. U and Sc are most mobile in the presence of salts regardless of the applied salt solution, i.e. CaCl2 = NaCl > deionized water. The formation of soluble chloride complexes with these elements could therefore be the cause of this phenomenon. For S, the leaching solution has no impact on its mobility. In conclusion, the presence of salts would tend to increase the mobility of divalent cations present in these residues and enhance their contamination potential. Modeling using PHREEQC software allowed comparison of these results with post-dismantling mineralogical characterization. Both methods showed: (i) total dissolution of fluorite [CaF2], galena [PbS], richterite [Na(CaNa(Mg,Fe2+)5[Si8O22](OH)] and Ba silicate; (ii) precipitation of iron oxides/hydroxides and silicate minerals. However, the modeling was unable to predict the behaviour of carbonate minerals. Further modeling tests involving kinetics should be considered in a future study.

Cleanup of sewage sludge spiked with Cd, Cu, and Zn: Sludge quality and distribution of metals in the "soil-plant-water" system.

Corn was grown under greenhouse conditions in the presence of uncleaned versus cleaned municipal sewage sludge to assess the effectiveness of a chemical leaching process that uses an inorganic acid and strong oxidants to clean biosolids (i.e., to remove metals without reducing their agronomic potential). Specifically, our study analyzed physicochemical sludge from the Montreal (MSL) wastewater treatment plant (WTP) and biological sludge from the Becancour (BSL) WTP. Both biosolids were spiked with individual metals (dry weight basis): Cd (100 mg kg-1), Cu (3000 mg kg-1), and Zn (5000 mg kg-1), or their mixture. MSL biosolid enrichment led to the solubilization of added metals and removed 84-88% of Cd, 78-79% of Cu, and 79-81% of Zn. Similarly, BSL biosolid enrichment resulted in the removal of 86-88% of Cd, 80-81% of Cu, and 88-89% of Zn. The fractional distribution of metals varied between biosolids depending on their production process, stabilization, and initial metal concentration. In the MSL biosolids, only Cu partitioning was influenced by spiking, cleanup, and washing. The three metals (Cd, Cu, and Zn) occurred either in their crystalline phase or were linked to Fe oxide, organic matter, or carbonate. In the BSL biosolids, the metals that were not in their crystalline phase were only associated with Fe oxide. This study demonstrated that 99% of Cd and Cu and 97% of Zn contents remained in the soil; however, biosolid cleanup generally decreased metal concentrations in plants, leachate, and/or soil.

Optimized indium solubilization from LCD panels using H2SO4 leaching.

Spent liquid crystal displays (LCDs) are a secondary source of precious/strategic metals, including indium (In). The present study involved optimizing the solubilization of this strategic element from samples of indium tin oxide (ITO) glass prepared from LCD screens of computer monitors and laptop screens. The influence of operating conditions on In solubilization, as well as optimum conditions for sulfuric acid leaching were defined by a Box-Behnken-type experimental design methodology. Optimum operating conditions include a leaching step for 30 min at a temperature of 70 °C in the presence of 0.4 N H2SO4 and a pulp density of 50% (w/v). Under these conditions, the quadratic model established to predict the solubilization of In from ITO glass samples provided an In solubilization efficiency of 89.7%, which was validated experimentally (99.5%). The analysis of direct operating costs and capital costs for the implementation of such a leaching process revealed that the process is conceivable for a high-capacity plant processing ~100 t/day of ITO glass.

Assessment of the leaching potential of flotation tailings from rare earth mineral extraction in cold climates.

Increasing use of rare earth elements (REEs) in modern technologies and existing or expected imbalances between demand and supply have led many countries, including Canada, to consider the exploitation of their own REEs primary sources. The objective of this study is a thorough characterization of the flotation tailings generated during the pre-concentration of REEs from a carbonatite type deposit with the aim of predicting their geochemical behaviour over time. These tailings were characterized based on physicochemical and mineralogical properties. Weathering cells were also used to assess the impact of temperature (3 and 19 °C) on the geochemical behaviour of the tailings exposed to a sub-arctic climate. Because the tailings consisted mainly of carbonates (97.4%) and had very high neutralization potential (859 kg CaCO3/t) relative to their acidity potential (3.94 kg CaCO3/t), no acid mine drainage (AMD) is anticipated. Compared to regional environmental standards and guidelines, the concentrations of Cd (0.20 µg/l), Zn (17 µg/l), and Pb (close to 4 µg/l) in leachates obtained during kinetic testing may be considered as potentially problematic. Finally, the results of the weathering cells at 3 °C indicate that the exposure to low temperatures may increase the concentrations of elements leached from the tailings. This study confirms that low temperatures and freeze-thaw events, which occur readily in a sub-arctic climate, may impact the geochemical behaviour of tailings produced from the extraction of REEs from carbonatite type deposit.

Geochemical behavior and stabilization of spent sulfate-reducing biofilter mixtures for treatment of acid mine drainage.

Sulfate-reducing biofilters operated in semi-passive or passive modes constitute an approach of choice for treatment of acidic mining effluents. The aim of the present study involved examining the behavior of biofilters after use based on two modes of management, namely in unsaturated and saturated media. Two acidophilic biofilters were investigated following their mixing with different alkaline industrial residues (i.e., 25% fly ash biomass or 30% aluminum red mud, or 10% kiln dust). Percolation column tests for a 330-d period indicated that aluminum red mud and lime kiln dust (to a lesser extent) are efficient materials for maintaining the pH neutrality of biofilter leachate and to reduce release of metals (i.e., Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in spent biofilters. The storage of biofilters in saturated mode also makes it possible to preserve the reducing conditions of the environment and neutrality of the pH and to limit the dissolution of the solution of cadmium, nickel and zinc. Conversely, increased iron release is noted under saturated conditions. Finally, the results indicated that a mixture of biofilters and lime kiln dust is preferable to surface addition of these to reduce the loss of metals in leachates.

Techno-economic assessment of an hydrometallurgical process to simultaneously remove As, Cr, Cu, PCP and PCDD/F from contaminated soil.

Industrial activities lead to the contamination of large amounts of soils polluted by both inorganic and organic compounds, which are difficult to treat due to different chemical properties. The efficiency of a decontamination process developed to simultaneously remove mixed contamination of industrial soils was evaluated at the pilot-scale, as well as operating costs associated to that process to define the best remediation approach. The results showed that the treatment of the coarse fractions (>0.250 mm) of 40 kg of soil by attrition in countercurrent mode allowed the removal of 17-42% of As, 3-31% of Cr, 20-38% of Cu, and 64-75% of polychlorinated dioxins and furans (PCDD/F). Removals of 60% for As, 2.2% for Cr, 23% for Cu, and 74% for PCDD/F were obtained during the treatment of attrition sludge (<0.250 mm) by alkaline leaching process. However, the results of the techno-economic evaluation, carried out on a fixed plant with an annual treatment capacity of 7560 tons of soil treated (tst), showed that the estimated overall costs for the attrition process alone [scenario 1] (CAD$ 451/tst) were lower than the costs of the process, which additionally includes an alkaline leaching step to treat attrition sludge [scenario 2] (CAD$ 579/tst). This techno-economic evaluation also showed that the process becomes competitive with current disposal options (thermal desorption and landfilling - CAD$ 600/tst) from a certain treatment capacity, which is around of 3465 tst/yr for the scenario 1 and 6930 tst/yr for the scenario 2. On the other hand, the techno-economic evaluations are crucial to selecting feasible decontamination process for a soil remediation project, with considerations of the type of contamination, site characteristics and cost effectiveness.

Prediction of physical separation of metals from soils contaminated with municipal solid waste ashes and metallurgical residues.

Environmental legislation is forcing industrialized countries to rehabilitate contaminated lands. Expensive solutions are available to treat soils contaminated by metals (e.g., solidification, stabilization, and landfilling). Physical remediation techniques, which are less expensive, are able to efficiently separate metals from contaminated soils under specific physical conditions. In the current study, densimetric and mineralogical characterization of fractions of soil between 0.25 and 4 mm contaminated by municipal solid waste (MSW) ashes and metallurgical waste was performed. This characterization confirmed the usefulness of the jig and wet shaking table for separating the metal contaminants from the soil. Mineralogical characterization allowed the prediction of treatment efficiencies and potential limits. The jig performance was optimized based on densimetric characterization. Water washing coupled with ferrous material extraction using magnetic separation, and, attrition scrubbing coupled with the jig and wet shaking table, led to a removal yield varying from 42.1% to 83.4% for Ba, Cu, Pb, Sn, and Zn from the fraction of soil >0.25 mm contaminated by MSW ashes. The recovered treated mass varied from 57.1% to 73.4% (by weight). For the fraction of soil >0.25 mm contaminated with metallurgical residues, Cu and Zn removal yields were higher than 57.5%. The recovered treated mass from this soil fraction corresponded to 64.8% (by weight). Depending on the level and leachability of contaminants, the soil fractions <0.25 mm were recommended for appropriate treatments (solidification or stabilization) or for safe disposal via landfills.

Comparison of different interpolation methods and sequential Gaussian simulation to estimate volumes of soil contaminated by As, Cr, Cu, PCP and dioxins/furans.

Understanding the spatial distribution of organic and/or inorganic contaminants is crucial to facilitate decision-making of rehabilitation strategies in order to ensure the most appropriate management of contaminated sites in terms of contaminant removals efficiencies and operating costs. For these reasons, various interpolation methods [Thiessen Polygon (TP) method, inverse of distance (IDW) method, ordinary kriging (OK), as well as sequential Gaussian simulations (SGS)] were used to better understand the spatial distribution of As, Cr, Cu, pentachlorophenol (PCP) and dioxins and furans (PCDD/F) found onto a specific industrial site. These methods do not only vary in complexity and efficiency but also lead to different results when using values coming from the same characterization campaign. Therefore, it is often necessary to evaluate their relevance by performing a comparative analysis. The results showed that ordinary kriging (OK) was a better estimator of the mean and more advanced compared to the two other methods of interpolation (TP and IDW). However, it appeared that SGS has the same power than OK but it also permitted to calculate a reliable value of the probabilities of exceeding regulatory cut-offs of contamination.

Semi-passive in-situ pilot scale bioreactor successfully removed sulfate and metals from mine impacted water under subarctic climatic conditions.

Mine drainage contaminated with metals is a major environmental threat since it is a source of water pollution with devastating effects on aquatic ecosystems. Conventional active treatment technologies are prohibitively expensive and so there is increasing demand to develop reliable, cost-effective and sustainable passive or semi-passive treatment. These are promising alternatives since they leverage the metabolism of microorganisms native to the disturbed site at in situ or close to in situ conditions. Since this is a biological approach, it is not clear if semi-passive treatment would be effective in remote locations with extremely cold weather such as at mines in the subarctic. In this study we tested the hypothesis that sulfate-reducing bacteria, which are microorganisms that promote metal precipitation, exist in subarctic mine environments and their activity can be stimulated by adding a readily available carbon source. An experiment was setup at a closed mine in the Yukon Territory, Canada, where leaching of Zn and Cd occurs. To test if semi-passive treatment could precipitate these metals and prevent further leaching from waste rock, molasses as a carbon source was added to anaerobic bioreactors mimicking the belowground in-situ conditions. Microbial community analysis confirmed that sulfate-reducing bacteria became enriched in the bioreactors upon addition of molasses. The population composition remained fairly stable over the 14 month operating period despite temperature shifts from 17 to 5 °C. Sulfate reduction functionality was confirmed by quantification of the gene for dissimilatory sulfite reductase. Metals were removed from underground mine drainage fed into the bioreactors with Zn removal efficiency varying between 20.9% in winter and 89.3% in summer, and Cd removal efficiency between 39% in winter and 90.5% in summer. This study demonstrated that stimulation of native SRB in MIW was possible and that in situ semi-passive treatment can be effective in removing metals despite the cold climate.

Removal of macro-pollutants in oily wastewater obtained from soil remediation plant using electro-oxidation process.

Electro-oxidation process by niobium boron-doped diamond (Nb/BDD) electrode was used to treat non-biodegradable oily wastewater provided from soil leachate contaminated by hydrocarbons. Firstly, the diffusion current limit and mass transfer coefficient was experimentally measured (7.1 mA cm-2 and 14.7 µm s-1, respectively), in order to understand minimum applied current density. Later on, the oxidation kinetic model of each pollutant was investigated in different current densities ranged between 3.8 and 61.5 mA cm-2. It was observed that direct oxidation was the main removal mechanism of organic and inorganic carbon, while the indirect oxidation in higher current density was responsible for nitrogen oxidation. Hydrocarbon in the form of colloidal particles could be removed by electro-flotation. On the other hand, electro-decomposition on the surface of cathode and precipitation by hydroxyl ions were the utmost removal pathway of metals. According to the initial experiments, operating condition was further optimized by central composite design model in different current density, treatment time, and electrolyte addition, based on the best responses on the specific energy consumption (SEC), chemical oxygen demand (COD), and total organic carbon (TOC) removal efficiency. Unde r optimum operating condition (current density = 23.1 mA cm-2, time = 120 min, Ti/Pt as a cathode, and Nb/BDD as the anode), electro-oxidation showed the following removal efficiencies: COD (84.6%), TOC (68.2%), oil and grease (99%), color (87.9%), total alkalinity (92%), Ntot (18%), NH4+ (31%), Ca (66.4%), Fe (71.1%), Mg (41.4%), Mn (78.1%), Ptot (75%), S (67.1%), and Si (19.1%). Graphical abstract Environmental significance statement Soil treatment facilities are rapidly grown throughout the world, especially in North America due to its intense industrialization. High water content soil in humid area like Canada produces significant amount of leachate which is difficult to remove by physical and biological processes. Current treatment facility was modified by applying the electro-chemical oxidation process. The kinetic models of each macro-pollutant included carbon, nitrogen, phosphorous, and metals were developed to investigate their oxidation mechanism (graphical abstract). The efficiency of treatment was monitored in order to optimize the decisive operating parameters of electro-oxidation process. The result of this article could pave the way of future investigation on efficient treatment of variety of oily wastewater.

Study of factors involved in the gravimetric separation process to treat soil contaminated by municipal solid waste.

The current research investigated the effectiveness of a gravimetric process (shaking table) to treat soil contaminated by municipal solid waste. A detailed characterization of the inorganic pollutants was performed, followed by concentrating the metals within smaller volumes using the shaking table technology. The densimetric examination of the 1-2 mm and 0.250-1 mm fractions of the contaminated soil showed that lead (Pb), copper (Cu), and tin (Sn) were mostly concentrated in the heavy fraction (metal removals > 50%). Scanning electron microscopy coupled with elemental analysis indicated the relevance of using gravimetric processes to treat this soil sample. The influence of shaking table parameters was determined using a Box-Behnken design. The tilt and washing water flow demonstrated significant effects on the motion of the 1-2 mm soil fraction and on the removal of Pb, Cu, and Sn. The results obtained under the optimal settings of the shaking table defined using the Box-Behnken methodology when treating the 1-2 mm fraction were close to those obtained when using dense media separation. The recovered mass of the concentrate was approximately 20.8% (w.w-1) of the total mass. The removals of Pb, Cu, and Sn were estimated to be 67.3%, 54.5% and 54.6% respectively. The predicted and experimental mass distributions of the medium (1-2 mm) and fine-sized (0.250-1 mm) particles were compared successively under some selected conditions. The mass distribution of both fractions showed similar tendencies in response to the forces applied by each condition. However, lowering the forces induced by the bumping action and the flowing film was recommended so as to efficiently treat the fine fraction (0.250-1 mm). The recovered mass of the concentrate (10%) was slightly lower than that obtained by dense media separation (13%). However, satisfactory removal yields were obtained for Pb, Cu, and Sn (42.7%, 23.6%, and 35% respectively).

Valorization of raw glycerol and crustacean waste into value added products by Yarrowia lipolytica.

Crude glycerol has been widely investigated as a renewable carbon source for biodiesel production. In the present study, this feedstock was supplemented by various inducers: surfactants and oils to enhance lipid and lipase production by the newly isolated yeast, Yarrowia lipolytica. Results have shown that a culture medium composed of olive oil could enhance lipase activity at 25U/mL and lipid content up to 35% (w/w). The fortification of the medium with crustacean waste increased the lipase activity up to 38U/mL. The hydrolytic activity of the extracellular lipases produced in mentioned medium was satisfactory and opened avenues for other biotechnological processes.

Effect of pCO2 on direct flue gas mineral carbonation at pilot scale.

Concerns about global warming phenomena induced the development of research about the control of anthropogenic greenhouse gases emissions. The current work studies on the scaling up of aqueous mineral carbonation route to reduce the CO2 emissions at the chimney of industrial emitters. The reactivity of serpentinite in a stirred tank reactor was studied for several partial pressures of CO2 (pCO2) (0.4, 0.7, 1.3 and 1.6 bar). Prior to carbonation, the feedstock was finely grinded and dehydroxyled at 650 °C by a thermal treatment. The major content of magnetite was removed (7.5 wt% · total weight-1). Experiments were carried out under batch mode at room temperature using real cement plant flue gas (14-18 vol% CO2) and open pit drainage water. The effect of the raw water and the pCO2 on the carbonation efficiency was measured. First, the main results showed a positive effect of the quarry water as a slight enhancement of the Mg leaching in comparison with distilled water. Secondly, a pCO2 of 1.3 bar was the optimal working pressure which provided the highest efficiency of the carbonation reaction (0.8 gCO2 · g residue-1). Precipitation rates of dissolved CO2 ranged from 7% to 33%. Pure precipitate was obtained and essentially composed of Nesquehonite. At a pCO2 of 1.3 bar, additional physical retreatment of the solid material after being contacted with 6 batches of gas enhanced considerably mineral carbonation efficiency (0.17 gCO2 · g residue-1.).

Treatment technologies used for the removal of As, Cr, Cu, PCP and/or PCDD/F from contaminated soil: A review.

The contamination of soils by metals such as arsenic, chromium, copper and organic compounds such as pentachlorophenol (PCP) and dioxins and furans (PCDD/F) is a major problem in industrialized countries. Excavation followed by disposal in an appropriate landfilling is usually used site to manage these contaminated soils. Many researches have been conducted to develop physical, biological, thermal and chemical methods to allow the rehabilitation of contaminated sites. Thermal treatments including thermal desorption seemed to be the most appropriate methods, allowing the removal of more than 99.99% of organic contaminants but, they are ineffective for inorganic compounds. Biological treatments have been developed to remove inorganic and hydrophobic organic contaminants but their applications are limited to soils contaminated by easily biodegradable organic compounds. Among the physical technologies available, attrition is the most commonly used technique for the rehabilitation of soils contaminated by both organic and inorganic contaminants. Chemical processes using acids, bases, redox agents and surfactants seemed to be an interesting option to simultaneously extract organic and inorganic contaminants from soils. This paper will provide an overview of the recent developments in the field of decontamination technologies applicable for the removal of As, Cr, Cu, PCP and/or PCDD/F from contaminated soils.

Study of the factors influencing the metals solubilisation from a mixture of waste batteries by response surface methodology.

This paper presents an innovative process for the recovery of valuable metals from a mixture of spent batteries. Different types of batteries, including alkaline, zinc-carbon (Zn-C), nickel cadmium (Ni-Cd), nickel metal hydride (Ni-MH), lithium ion (Li-ion) and lithium metallic (Li-M) batteries, were mixed according to the proportion of the Canadian sales of batteries. A Box-Behnken design was applied to find the optimum leaching conditions allowing a maximum of valuable metal removals from a mixture of spent batteries in the presence of an inorganic acid and a reducing agent. The results highlighted the positive effect of sodium metabisulfite on the performance of metals removal, especially for Mn. The solid/liquid ratio and the concentration of H2SO4 were the main factors affecting the leaching behavior of valuable metals (Zn, Mn, Cd, Ni) present in spent batteries. Finally, the optimum leaching conditions were found as follows: one leaching step, solid/liquid ratio = 10.9%, [H2SO4] = 1.34 M, sodium metabisulfite (Na2S2O5) = 0.45 g/g of battery powder and retention time = 45 min. Under such conditions, the removal yields achieved were 94% for Mn, 81% for Cd, 99% for Zn, 96% for Co and 68% for Ni.