This investigation presents the development of a waste batteries recycling technology, that could lead to the minimization of waste discharged and contamination problems and to the depletion of ...natural resources. This study mainly focused on the recovery of metals from a pregnant leach solution (PLS) obtained from a sulphuric leaching process applied to unsorted spent batteries. The PLS mainly contains Zn, Mn, Cd, Ni and Co. Cyanex 272 (di-2,4,4-trimethylpentyl phosphinic acid) was used to selectively recover Zn from the mixed solution. The Zn-Cyanex 272 was stripped and electrodeposited in metallic form and approximately 134 kg of Zn were recovered. Cd and Mn were co-extracted in the organic solvent D2EHPA (2-ethylhexylphosphonic acid) from the Zn-depleted solution and they were stripped using H2SO4. Consequently, Cd was selectively electrodeposited from a sulphate-stripped solution where the amount of Cd recovered was equal to 21.6 kg Cd per ton of waste battery powder. Residual Mn was recovered in the carbonate form by the addition of Na2CO3 (238 kg of Mn t−1 of waste battery powder). In the following step, Cyanex 272 was used to remove Co and other impurities from the Zn-Cd-Mn depleted solution, while Ni was not extracted. Finally, Ni was precipitated from the pure NiSO4 solution with Na2CO3 and 23.8 kg of Ni were recovered per ton of waste battery powder. The costs of the process develop to recover metals (including only chemical costs and energy consumption) are estimated at $814 t−1 of battery powder, while the metal revenues obtained are estimated at $2132 t−1 of battery powder. The chemical cost/metal revenue ratio is lower than 50%, which indicates that the process is feasible.
•A sulfuric acid leaching process is applied on unsorted spent batteries.•The pregnant leach solution (PLS) contains Zn, Mn, Cd, Ni and Co.•Zn and Cd are separated from PLS using solvent extraction and electrodeposition.•Mn and Ni are recovered using chemical precipitation as metal carbonates.
Spent batteries contain hazardous materials, including numerous metals (cadmium, lead, nickel, zinc, etc.) that are present at high concentrations. Therefore, proper treatment of these wastes is ...necessary to prevent their harmful effects on human health and the environment. Current recycling processes are mainly applied to treat each type of spent battery separately. In this laboratory study, a hydrometallurgical process has been developed to simultaneously and efficiently solubilize metals from spent batteries. Among the various chemical leaching agents tested, sulfuric acid was found to be the most efficient and cheapest reagent.
A Box-Behnken design was used to identify the influence of several parameters (acid concentration, solid/liquid ratio, retention time and number of leaching steps) on the removal of metals from spent batteries. According to the results, the solid/liquid ratio and acid concentration seemed to be the main parameters influencing the solubilization of zinc, manganese, nickel, cadmium and cobalt from spent batteries. According to the results, the highest metal leaching removals were obtained under the optimal leaching conditions (pulp density = 180 g/L (w/v), H2SO4 = 1 M, number of leaching step = 3 and leaching time = 30 min). Under such optimum conditions, the removal yields obtained were estimated to be 65% for Mn, 99.9% for Cd, 100% for Zn, 74% for Co and 68% for Ni. Further studies will be performed to improve the solubilization of Mn and to selectively recover the metals.
•Metals present in spent batteries were efficiently recycled.•Sulfuric acid was proved to be an efficient leaching agent to solubilize metals.•Optimum leaching conditions were determined using a Box-Behnken design.•Up to 65% of Mn, 68% of Ni, 74% of Co and 100% of Cd and Zn were solubilized.
The use of CO2 mineral carbonation represents an attractive approach to recycling waste concrete. In this study, the effect of gas pressure, Liquid/Solid (L/S) ratio (w/w), Gas/Liquid (G/L) ratio ...(v/v) and reaction time for CO2 sequestration were investigated. While carbonation of such matrix is already described, this study opens new insights in concrete carbonation. To increase the reactivity potential of concrete, the fine fraction (<500 μm), which contains mostly cement paste, was separated from the inert coarse aggregates. Separation was conducted by crushing and sieving. The ground fine concrete fraction showed enhanced reactivity with 75% of CO2 removed (corresponding to 0.057 g CO2 removed/sample) compared to that of raw concrete, with 54% of CO2 removed (corresponding to 0.034 g CO2 removed/sample). Tests were conducted under 144 psi of gas pressure (9.93 Bars) at ambient temperature for 10 min. On the other hand, the resulting aggregates fraction have an improved potential recycling value. The new proposed approach allows better carbonation efficiency and increases the overall valuation of waste concrete.
A pilot field study was conducted in a Canadian northern village (NV) to assess the remediation efficiency of sodium persulphate (SPS) alkali activated with calcium peroxide (CP) to degrade diesel ...from Arctic raft soil. A minimum temperature increase in the subsurface due to overall process reactions was required. The projected context of application was imperative to preserve the integrity of the remaining permafrost. The test was performed with two soil columns of 370 L buried in the ground. The columns were contaminated with 7500 mg diesel/kg representative raft soil that was matured for a period of 11 months. The continuous delivery by gravity and the static presence of the oxidizing solution was made over 33 days. During that period, SPS concentration, pH and temperatures, were monitored. SPS was activated prior to its distribution and activation by-products were confined in a surficial tank and under a sludge form. The maturation period resulted in the important natural attenuation of diesel (47%) that occurred in the shallower horizons of the soil profile. About 35% of the diesel remaining after the maturation period was removed by chemical oxidation during the operation period on site. The temperature increase measured during the SPS activation process was not significant while the temperature increase due to diesel degradation by oxidation in the subsurface was evaluated to be below 3°C. The soil columns were not clogged by the by-products as indicated by hydraulic testing before and after oxidizing treatment.
► Electrocoagulation and flocculation combined is effective in removing Ptot from MWW. ► The best performance was established using 38.2mA/cm2 for a period of 20min. ► Ptot concentration ...(C0=5.0−50mg/L) could be optimally diminished by up to 97%. ► Electrochemical coagulation was more effective than chemical treatment using FeCl3. ► Electrochemical treatment involved a total cost varying from 0.24 to 0.31 CAN $/m3.
Effluents from municipal wastewater treatment plants (WTP) can contain residual phosphorus concentration above the recommended limiting values and it could have a high environmental impact (e.g. eutrophication as a result of excess nutrients). In order to produce an effluent suitable for stream discharge, electrochemical techniques have been explored at the laboratory pilot scale, for total phosphorus (Ptot) removal from spiked municipal wastewater (MWW). The MWW was an effluent provided from a biofiltration process installed at the Quebec Urban Community WTP. The effects of current density, retention time and initial Ptot concentration were investigated using a bipolar electrolytic cell made of mild steel electrodes. Effectiveness was measured in terms of Ptot reduction. The amount of residual sludge produced and energy consumed have been also considered. Results showed that the best performances of Ptot removal from MWW were obtained while combining electrocoagulation with flocculation. Under optimal conditions, electrolysis was operated at a current density of 38.2mA/cm2 through 20min of treatment and then, the electrocoagulated-effluent was flocculated using a cationic polymer (10mg/l) before filtration. At least, 97% of Ptot was removed regardless of the initial Ptot concentration imposed (5.0–50mg/l) in MWW. The optimal conditions determined for Ptot removal, including energy consumption, electrode consumption and metallic sludge disposal, involved a total cost varying from 0.24 to 0.35$CAN per cubic meter of treated MWW in continue mode operation.
Mineral carbonation (MC) represents a promising alternative for sequestering CO2. In this work, the CO2 sequestration capacity of the available calcium-bearing materials waste concrete and ...anorthosite tailings is assessed in gas–solid–liquid and gas–solid routes using 18.2% flue CO2 gas. The objective is to screen for a better potential residue and phase route and as the ultimate purpose to develop a cost-effective process.
The results indicate the possibility of removing 66% from inlet CO2 using waste concrete for the aqueous route. However, the results that were obtained with the carbonation of anorthosite were less significant, with 34% as the maximal percentage of CO2 removal. The difference in terms of reactivity could be explained by the accessibility to calcium. In fact, anorthosite presents a framework structure wherein the calcium is trapped, which could slow the calcium dissolution into the aqueous phase compared to the concrete sample, where calcium can more easily leach.
In the other part of the study concerning gas–solid carbonation, the results of CO2 removal did not exceed 15%, which is not economically interesting for scaling up the process.
The results obtained with waste concrete samples in aqueous phase are interesting. In fact, 34.6% of the introduced CO2 is converted into carbonate after 15 min of contact with the gas without chemical additives and at a relatively low gas pressure.
Research on the optimization of the aqueous process using waste concrete should be performed to enhance the reaction rate and to develop a cost-effective process.
•Dry and aqueous flue gas mineral carbonation routes were investigated.•Two types of calcium-bearing residues were tested.•Dry phase experiments did not showed any carbonates formation.•Waste concrete is more reactive than anorthosite residues.•34.6% of CO2 was converted into carbonate with concrete samples in aqueous phase.
This paper provides a quantitative comparison between electrocoagulation and chemical precipitation based on heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) removal from acidic soil leachate (ASL) at the ...laboratory pilot scale. Chemical precipitation was evaluated using either calcium hydroxide or sodium hydroxide, whereas electrocoagulation was evaluated via an electrolytic cell using mild steel electrodes. Chemical precipitation was as effective as electrocoagulation in removing metals from ASL having low contamination levels (30mgPbl−1 and 18mgZnl−1). For ASL enriched with different metals (each concentration of metals was initially adjusted to 100mgl−1), the residual Cr, Cu, Pb and Zn concentrations at the end of the experiments were below the acceptable level recommended for discharge in sewage urban works (more than 99.8% of metal was removed) using either electrocoagulation or chemical precipitation. Cd was more effectively removed by electrochemical treatment, whereas Ni was easily removed by chemical treatment. The cost for energy, chemicals and disposal of metallic residue of electrocoagulation process ranged from US$ 8.83 to 13.95tds−1, which was up to five times lower than that recorded using chemical precipitation. Highly effective electrocoagulation was observed as the ASL was specifically enriched with high concentration of Pb (250–2000mgPbl−1). More than 99.5% of Pb was removed regardless of the initial Pb concentration imposed in ASL and, in all cases, the residual Pb concentrations (0.0–1.44mgl−1) were below the limiting value (2.0mgl−1) for effluent discharge in sewage works.
This work focuses on the influence of different parameters on the efficiency of steel slag carbonation in slurry phase under ambient temperature. In the first part, a response surface methodology was ...used to identify the effect and the interactions of the gas pressure, liquid/solid (L/S) ratio, gas/liquid ratio (G/L), and reaction time on the CO
2
removed/sample and to optimize the parameters. In the second part, the parameters’ effect on the dissolution of CO
2
and its conversion into carbonates were studied more in detail. The results show that the pressure and the G/L ratio have a positive effect on both the dissolution and the conversion of CO
2
. These results have been correlated with the higher CO
2
mass introduced in the reactor. On the other hand, an important effect of the L/S ratio on the overall CO
2
removal and more specifically on the carbonate precipitation has been identified. The best results were obtained L/S ratios of 4:1 and 10:1 with respectively 0.046 and 0.052 gCO
2
carbonated/g sample. These yields were achieved after 10 min reaction, at ambient temperature, and 10.68 bar of total gas pressure following direct gas treatment.
In this study, expanded titanium (Ti) covered with ruthenium oxide (RuO
2) electrode was used to anodically oxidize polycyclic aromatic hydrocarbons (PAH) in creosote solution. Synthetic ...creosote-oily solution (COS) was prepared with distilled water and a commercial creosote solution in the presence of an amphoteric surfactant; Cocamidopropylhydroxysultaine (CAS). Electrolysis was carried out using a parallelepipedic electrolytic 1.5-L cell containing five anodes (Ti/RuO
2) and five cathodes (stainless steel, 316L) alternated in the electrode pack. The effects of initial pH, temperature, retention time, supporting electrolyte, current density and initial PAH concentration on the process performance were examined. Experimental results revealed that a current density of 9.23
mA
cm
−2 was beneficial for PAH oxidation. The sum of PAH concentrations for 16 PAHs could be optimally diminished up to 80–82% while imposing a residence time in the electrolysis cell of 90
min. There was not a significant effect of the electrolyte (Na
2SO
4) concentration on oxidation efficiency in the investigated range of 500–4000
mg/L. However, an addition of 500
mg
Na
2SO
4
L
−1 was required to reduce the energy consumption and the treatment cost. Besides, there was no effect of initial PAH concentration on oxidation efficiency in the investigated range of 270–540
mg
PAH
L
−1. Alkaline media was not favourable for PAH oxidation, whereas high performance of PAH degradation could be recorded without initial pH adjustment (original pH around 6.0). Likewise, under optimal conditions, 84% of petroleum hydrocarbon (C
10–C
50) was removed, whereas removal yields of 69% and 62% have been measured for O&G and COD, respectively. Microtox and
Daphnia biotests showed that electrochemical oxidation using Ti/RuO
2 could be efficiently used to reduce more than 90% of the COS toxicity.
Mineral carbonation is gaining increasing attention for its ability to sequester CO2. The main challenge is doing it economically and energy-efficiently. Recently, many studies have focused on the ...aqueous reaction of carbon dioxide with the alkaline earth minerals such as serpentine, Mg-rich olivine and wollastonite. Nevertheless, Fe-rich olivines have been poorly studied because of their high energy demand, which make them unfeasible for industrial implementation. This article describes the feasibility of an indirect mineral carbonation process using silicic, Fe-rich mining waste with direct flue gas CO2 via iron complexation using 2,2′-bipyridine. The overall process was performed in three main steps: leaching, iron complexation, and aqueous mineral carbonation reactions. The preferential parameters resulted in a recirculation scenario, where 38% of Fe cations were leached, complexed, and reacted under mild conditions. CO2 uptake of 57.3% was achieved, obtaining a Fe-rich carbonate. These results are promising for the application of mineral carbonation to reduce CO2 emissions. Furthermore, the greenhouse gas balance had a global vision of the overall reaction’s feasibility. The results showed a positive balance in CO2 removal, with an estimated 130 kg CO2/ton of residue. Although an exhaustive study should be done, the new and innovative mineral carbonation CO2 sequestration approach in this study is promising.
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