Ni Extraction Research Articles

Dissolution of copper and nickel from nickel-rich anode slimes under oxidized pressure leaching

ABSTRACT Anode slimes are valuable by-products in the electrolytic copper refinery process. This study aimed to investigate maximum extraction efficiency of Cu and Ni from slimes originating from the electrorefining of anodes containing high [Ni]. In addition, the extractions of Se, Te, As and Bi were determined. A factorial leaching series was conducted with T = 140–160°C, [H2SO4] = 12–20%, p O2 = 2–8 bars and solid/liquid ratio = 200–400 g/L. The highest Ni extraction of 99.7% was obtained with [H2SO4] = 20%, p O2 = 8 bar and T = 160°C while maintaining S/L ratio of 200 g/L. The extraction of copper was found to be within 97–99% in all the leaching experiments. Increasing acidity and decreasing S/L ratio increased the efficiency of Cu extraction. Mineralogical characterizations by SEM-EDX demonstrated the presence of Ag2Se, BaSO4, PbSO4 and several oxide phases in the leach residue.

Extraction of Cu, Zn, and Ni from waste silica-rich integrated circuits by sulfation roasting and water leaching

High-tech electrical and electronic equipment contain large numbers of silica-rich integrated circuits (SRICs) which after its end of life generate huge amount of waste; however, its valuable metal contents can be properly recycled. Extraction of Cu, Ni, and Zn from pulverized SRIC obtained from discarded waste electrical and electronic equipments (WEEE) by sulfation roasting followed by water leaching was studied. Co-extraction of other metals such as Fe, Al, and Pb present in the sample was also explored. Effects of H2SO4/SRIC ratio, roasting temperature, time, and varying water leaching conditions on the extraction efficiencies were evaluated. The optimum conditions for Cu, Zn, and Ni extractions were determined as H2SO4/SRIC ratio 0.5, roasting temperature 300 °C, roasting time 60 min, leaching temperature 50 °C, leaching time 60 min, and liquid–solid ratio = 10:1 (i.e., 100 mL/10 g) with extraction efficiencies of 61.9, 84.9, and 93.6% for Cu, Ni, Zn, and co-extractions of Fe and Al were 71.1 and 55.6, respectively. Under the optimum conditions, approximate 20% Fe3+ was naturally precipitated which is advantageous for the subsequent step. Comparatively, higher extraction efficiencies of Cu, Zn, and Ni were observed in water leaching of H2SO4-roasted sample than direct H2SO4 leaching of raw sample keeping other leaching conditions constant. Lead retained in the roasted–leached residue was extracted with dilute HCl leaving silica and Al in the final leached residue. Process flow sheet for the extraction of Cu, Ni, Zn, and Pb and reuse of silicon from waste SRICs was proposed.

Enhanced Ni phytoextraction by effectiveness of chemical and biological amendments in sunflower plant grown in Ni-polluted soils

ABSTRACTA greenhouse study was conducted as a completely randomised design in a factorial arrangement to assess how inoculation of AMF (arbuscular mycorrhizal fungus) and application of EDTA (ethylenediaminetetracetic acid) as biological and chemical amendments can affect the Ni (nickel) phytoremediation in Ni-polluted soils using sunflower plant. The results showed that the inoculation of AMF increased root colonisation while applying EDTA and high level of Ni decreased it. Microbial incubation has a positive effect on both shoot and root dry yields; however, co-application of Ni and EDTA demoted the growth rate. Shoot nutrients uptake of plants decreased as Ni levels increased. In inoculated plants, shoot uptake of Zn, Fe and Mn was higher in all Ni levels than non-inoculated plants. Ni uptake in plant shoots and roots increased with applying both AMF and EDTA. However, the mean Ni concentration and uptake in inoculated plants along with applying EDTA are higher in sunflower shoots than in roots. As Ni levels increased, Ni extraction and uptake efficiencies increased; it can be concluded co-application of EDTA and AMF was effective in increasing phytoextraction potential of sunflower plants in Ni-contaminated sites. This study highlights that AMF could be suitable for cleaning Ni-polluted areas and it could significantly contribute to phytoremediation technology.

Effect of nickel concentration and soil pH on metal accumulation and growth in tropical agromining ‘metal crops’

This study investigated the physico-geochemical properties of three types of ultramafic substrates in Sabah (Malaysia) and further characterised their influence on nickel (Ni) accumulation in two selected tropical ‘metal crops’ (Phyllanthus rufuschaneyi and Rinorea cf. bengalensis). Three experiments, consisting of a randomised block growth trial in large pots over 12 months in Sabah, were conducted: i) soil ratio experiment (Cambisol:Ferralsol:Leptosol), ii) soluble Ni dosing experiment with added 0, 60, 240, 600 mg Ni kg−1, and iii) soil pH adjustments (pH 5.2, 5.8 and 6.4) experiment. The results show that the low pH status of Ferralsol did not result in increased extractable Ni concentrations, indicating that Ni-bearing phases and mineralogy play a major role in Ni extractability in these substrates. The increasing order of extractable Ni concentrations was Ferralsol 15 g kg−1 in P. rufuschaneyi) in the Cambisol, >5-fold higher relative to that recorded in Leptosol and Ferralsol. Mixing the Cambisol with the other substrates significantly improved Ni yield in both species relative to the individual substrates. The effect of Ni addition on the selected ‘metal crops’ was species-dependent, whereas reduction of soil pH in Cambisol significantly reduced Ni yield in both species. Nickel accumulation patterns in ‘metal crops’ in response to the diverse ultramafic soils in the tropics are influenced by the physico-geochemical characteristics of the soil types. Soil Ni extractability in these soils is more dependent on the Ni-bearing phases and mineralogy rather than the pH status. This study provides useful information on plant-soil interactions required for identifying suitable substrates for implementing tropical Ni agromining.

Mechanism of nickel extraction from sulfuric acid medium by synthesized α‐aminophosphonate derivative

A new compound, α‐aminophosphonate derivative containing pyridine ring (PPDE), was designed and synthesized as an extractant for the separation of nickel from metal impurities. Over 94.5% of Ni (II) extraction from sulfuric acid solution was achieved by using PPDE with an equilibrium pH of 4.02. Meanwhile, high separation coefficients of 23.8 for Ni to Co, 84.9 for Ni to Mn, 254.1 for Ni to Ca and 696.7 for Ni to Mg, respectively, were obtained. It was noted that PPDE exhibited an excellent regenerability, and the extraction of Ni with the recycled organic phase ranged from 92.5% to 93.9% during six circulations. The extracted nickel complex was determined as [Ni (PPDE)2(DNNSA−)2(H2O)4], which was supported by the data obtained from Fourier transform‐infrared, UV–Vis and electrospray ionization‐mass spectrometry spectra.

Preferential extraction of Ni(II) over Co(II) by arylsulphonic acid in the presence of pyridinecarboxylate ester: Experimental and DFT calculations

Selective extraction of Ni(II) from base metals is a critical step in the direct nickel synergistic extraction process. Significant synergistic effect and preferential extraction of Ni(II) over Co(II) were observed by using the synergistic extractant containing dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (ligand L) in Escaid 110. The selectivity sequence followed the order: Ni(II) > Co(II) > Al(III) > Mg(II) > Fe(III). In order to elucidate the separation difference between Ni(II) and Co(II) which had similar chemical properties, statistical thermodynamics analysis and relativistic density functional theory (DFT) calculations were applied to provide the selective mechanism from both macroscopic and microscopic perspectives. The synergistic extraction diagrams showed that the optimum molar ratio of HDNNS and the ligand L was at 1:2 for Ni(II) and Co(II) extraction, and statistical thermodynamics analysis indicated that the overall extraction process was endothermic. According to DFT calculation results, the optimized geometries of the Ni(II) and Co(II) complexes were in accordance with the crystallographical data. The thermodynamical examination for the Ni and Co extraction was further conducted using a thermodynamical cycle. The difference in the change of Gibbs free energies for the formation of the Ni(II) complex was more negative than that of the Co(II) complex, which was in agreement with the experimental data. It could be concluded that the synergistic extractant had a higher affinity for Ni(II) than Co(II), which might account for the preferential extraction of Ni(II) over Co(II). The results established a computational model capable of predicting the selectivity order of metal ions, which would provide new insights into the separation mechanism of Ni(II) and Co(II) with synergistic extractants.

Comparison of Hydro- and Biohydrometallurgical Extraction of Metals from Waste Li-Ion Batteries of Cell Phone

In the present study, the black residual powders of waste Li-ion batteries were treated with citric, malic, and a combination of these acids for chemical extraction of multimetals. Among the treatments, 0.75 M malic + 0.75 M citric acid was found to be better than either 1.5 M citric acid or 1.5 M malic acid for 20 g L−1 pulp density at 90 °C. Bioleaching studies were carried out by Leptospirillum ferriphilum-dominated consortium using the two-step process, which resulted in 1.2–1.8-fold higher metal extractions compared to a one-step process. At optimal pH 2.0, Cu–Zn–Ni solubilization was 85 ± 2%, while Co and Li extractions were 97.2% and 33.96%, respectively, after 2–6 days with 10 g L−1 pulp density. When 9 g L−1 initial ferrous iron concentration was used, Cu–Zn–Ni–Co extractions were 92 ± 7%, whereas Li solubilization attained 37.74% within 2–8 days. Optimization of the bioleaching process resulted in 1.7–2.7-fold increase in metal extractions. Studies at 10, 50, and 100 g L−1 pulp densities showed that metal extraction operational time increased as the pulp density was increased, and the obtained extractions ranged between 83 and 40% for Cu, 93 and 54% for Zn, 91 and 27% in the case of Ni, 99 and 17% Co and Li extractions were 44 and 13%. For the spent medium at 10, 50, and 100 g L−1 pulp densities, Cu extraction ranged between 52 and 33%, Zn extractions between 78 and 39%, Ni extractions between 73 and 25%, Co extractions between 58 and 16%, and Li extractions between 22 and 5% within 4–6 days of reaction time. Presence of the consortium had a beneficial influence on the extraction of all the metals studied.

A study on selective leaching of heavy metals vs. iron from fly ash

Incinerator plant waste streams contain underexploited metals originating from households and industrial operators. The objective was to investigate the dissolution behavior of fly ash in: 0.2–7 M HCl, 0.2–7 M H2SO4, 0.5–1 M oxalic acid, 0.5–4 M citric acid, 0.5–7 M acetic acid, water, and ethaline, at 33 °C during 24 h leaching. The capability for high metals’ extraction of Zn, Cu, Ni, Pb, and Fe and management of the heavy metal Pb through leaching or precipitation was investigated. Selective leaching of valuable metals vs. Fe was observed. The target was to find a sustainable leaching method and provide a basis for further development of metal recovery from fly ash. The highest Zn extraction (> 80%) was achieved with 3 M H2SO4 and 7 M HCl, which also dissolved Cu (> 87%) and Ni (> 65%). However, more dilute HCl, 0.2 M, was able to provide Zn, Cu, and Ni extractions of 43, 86, and 18%, respectively. Efficient Pb leaching was achieved in HCl—complete extraction was provided by 3 and 5 M HCl, whereas H2SO4 did not extract Pb due to PbSO4 formation; similarly, in oxalic acid, Pb precipitated as PbC2O4. Ethaline could extract 50% of Pb with high selectivity towards Fe.

Hydrometallurgical production of LiNi0.80Co0.15Al0.05O2 cathode material from high-grade nickel matte

In this study, a material-oriented metallurgical strategy, which is of such characteristics as short process, energy conservation and cost saving, is proposed to treat high-grade nickel matte and simultaneously produce LiNi0.80Co0.15Al0.05O2 cathode material for lithium ion batteries. This process is mainly composed of four steps, which is oxidation roasting, two-stage leaching, purification and material synthesis. First, high-grade nickel matte is roasted to eliminate sulfur under air atmosphere. Then the roasted product is first leached to selectively remove 78.10% Cu with little Ni and Co extraction at atmospheric temperature under optimum conditions (25 °C, HCl 1.50 mol L−1, L/S 7.0, 30 min). After that, 96.23% Ni, 96.58% Cu and 84.18% Co are extracted in thermal leaching process under optimum conditions (70 °C, HCl 3.0 mol L−1, L/S 10.0, 120 min), leaving Fe, Zn and Ca in residue. The obtained lixivium is purified by solvent extraction method to adjust the mass ratio of Cu and Ni to the range that meets the requirement for preparation of cathode material. Finally, LiNi0.80Co0.15Al0.05O2 material is produced by spray pyrolysis and sintering. The electrochemical performance of the resulting material is comparable with that prepared from analytical reagents, indicating such process can realize the comprehensive utilization of high-grade nickel matte.

Column leaching of low-grade saprolitic laterites and valorization of leaching residues

Socio-economic data on nickel and cobalt show their importance throughout the entire metal value chain, from mining to end use, disposal and recycling. Thus, the extraction of both metals from primary and secondary raw materials as well as from wastes is currently considered strategically important for the industry and the society. In this paper heap leaching of Greek low-grade saprolitic laterites, with Ni content 0.97%, was investigated. The main parameters studied involved the strength of the H2SO4 solution used (49 and 147gL−1) and the effect of adding sodium sulfite (Na2SO3) in the leaching medium. The pregnant leach solution (PLS) was recycled several times during leaching in order to minimize acid consumption. The experimental results showed that within a period of 25days, and under the optimum conditions (147gL−1 H2SO4 and 20gL−1 Na2SO3), i) Ni and Co extractions were 72.5% and 47.4%, respectively and ii) Fe and Al co-extractions were 8.7% and 31.3%, respectively. Furthermore, valorization of the leaching residues through alkali activation using NaOH and Na2SiO3 and the addition of metakaolin (MK) for the production of inorganic polymers (IPs) was explored. X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Differential scanning calorimetry (DSC/TG) and Scanning electron microscopy (SEM-EDS) were used to characterize the ore, its leaching residues and the IPs. The IPs produced demonstrated high compressive strength, almost 40MPa and are suitable for a wide range of applications in the construction sector.

Preliminary Study of Smelting of Indonesian Nickel Laterite Ore using an Electric Arc Furnace

Nickel is one of the most important metals in industry. Sources of nickel can be classified into two groups: sulfide and laterite ores. Now, laterite ore is more potential. Due to its problem, this research aims to find an effective way of processing laterite ore. The nickel content from laterite ore was analyzed by variation of particle size. The highest nickel content from nickel laterite ore of this research is the sample with particle size is -80#100 mesh. The preliminary study of smelting of Indonesian laterite nickel ore using PKSC as reductant shows that the best Ni extraction is 89,35%.

Counter-Current Leaching of Low-Grade Laterites with Hydrochloric Acid and Proposed Purification Options of Pregnant Solution

A hydrochloric acid hydrometallurgical process was evaluated for Ni and Co extraction from a low-grade saprolitic laterite. The main characteristics of the process were (i) the application of a counter-current mode of operation as the main leaching step (CCL), and (ii) the treatment of pregnant leach solution (PLS) with a series of simple precipitation steps. It was found that, during CCL, co-dissolution of Fe was maintained at very low levels, i.e., about 0.6%, which improved the effectiveness of the subsequent PLS purification step. The treatment of PLS involved an initial precipitation step for the removal of trivalent metals, Fe, Al, and Cr, using Mg(OH)2. The process steps that followed aimed at separating Ni and Co from Mn and the alkaline earths Mg and Ca, by a combination of repetitive oxidative precipitation and dissolution steps. Magnesium and calcium remained in the aqueous phase, Mn was removed as a solid residue of Mn(III)–Mn(IV) oxides, while Ni and Co were recovered as a separate aqueous stream. It was found that the overall Ni and Co recoveries were 40% and 38%, respectively. About 45% of Ni and 37% of Co remained in the leach residue, while 15% Ni and 20% Co were lost in the Mn oxides.

Chemical and microbial leaching of base metals from obsolete cell-phone printed circuit boards

Abstract Bioleaching process is recommended for the recovery of metals from electronic waste (E-waste) due to its environment-friendly nature and a rich source of metals present in the E-waste. Each gram of cell phone printed circuit boards (PCBs) powder used in the study contained 275.5, 17.85 and 19.55 mg copper, zinc and nickel as major metal constituents respectively. The chemical leaching by mixture of ferric sulphate and ferrous sulphate (70:30) at 100 g L−1 pulp density was best for copper leaching among the studied systems in which after 4 d of reaction time, 2740 mg copper was solubilized from cell phone PCB powder, while ferric sulphate alone was best for zinc and nickel solubilisation, in which 88 mg zinc and 135 mg nickel were solubilised after 4 d and 7 d of reaction time, respectively. Bioleaching study showed that with acidophilic iron oxidizers, pH 1.8 and initial ferrous concentration 9 g L−1 were optimum for Cu–Zn–Ni extraction from discarded cell phone PCB powder. Cu–Zn–Ni extractions from 10 g L−1 cell phone PCB powder pulp density by the metabolites of iron-oxidizing consortium were 275, 5 and 11 mg, while at 50 and 100 g L−1 pulp density, extractions were 1350, 18 and 53 mg, and 2640, 25 and 100 mg, respectively. The process can be further scaled-up for higher pulp density.

The separation of Ni(II) over base metal ions in acidic polymetallic medium: Synergistic extraction and structural evidence

The selective extraction of Ni(II) from a polymetallic solution was achieved with an extractant mixture containing dinonylnaphthalene disulfonic acid (H2DNNDS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC, LII). The equilibrium results indicated that Ni(II) extraction was sensitive to the molar fraction of 4PC in the mixture containing H2DNNDS and 4PC. It was found that individual H2DNNDS or 4PC resulted in low extraction efficiency of Ni(II). Interestingly, when the mole fraction of 4PC in the mixture surpassed 50%, significant synergistic effect was observed for Ni(II) separation over Fe(III), Al(III), Ca(II), Mg(II) and Mn(II), thus highlighting the synergistic role of 4PC. In order to provide structural evidence for synergistic mechanism, two nickel model complexes were synthesized with 1,5-naphthalene disulfonic acid (H2NDS) in the absence/presence of methyl isonicotinate (LI), which were the corresponding short-chain analogues of H2DNNDS and 4PC, respectively. Combined with single crystal X-ray diffraction of nickel model complexes, the coordination chemistry of nickel complex in the loaded organic phases was disclosed with the Fourier Transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results showed that Ni(II) was directly coordinated with two monodentate ligands LI and four water molecules, while no direct interaction existed between Ni(II) and the O atoms of the deprotonated H2NDS in both two nickel model complexes. Hydrogen-bonding interaction between the H atom of coordinated water and the O atom of the deprotonated H2NDS played important role in stabilization of coordination configuration. The selective extraction of Ni(II) might be attributed to the incorporation of the pyridine based nitrogen donor into the inner coordination sphere of Ni(II) to supplant coordinated water.

Mechanochemical pre-treatment of lateritic nickel ore with sulfur followed by atmospheric leaching

In this study, the role of mechanochemical pre-treatment with the addition of S in atmospheric agitation leaching of a lateritic nickel ore was investigated. In the mechanically activated sample with S (20 wt%), the amount of Ni-Co-bearing amorphous FeMg hydrosilicate phases decreased and a new FeMgS phase was formed. In addition, the formation of NiSO4 was determined by X-ray photoelectron spectroscopy analysis. The effect of leaching temperature, leaching time, H2SO4 concentration, and the amount of S added during the mechanochemical pre-treatment on the extractability of Ni, Fe, and Co were investigated. When the mechanically activated sample with 20% added S was leached for 2 h under conditions of a solid/liquid ratio of 1/2.5 (w/w), temperature of 85 °C, and H2SO4 concentration of 300 g/L, 92.0% Ni, 79.1% Fe, and 84.8% Co extractions were achieved. Moreover, 17.5% lower Ni extraction was obtained using the mechanically activated sample without S. In terms of leaching behavior, the relationship between Ni and Fe dissolution weakened after mechanochemical activation. Furthermore, the leaching of the newly formed compounds was mostly controlled by the chemical reaction model.

Speciation of nickel extracted from hyperaccumulator plants by water leaching

Agromining combines agronomic and hydrometallurgical processes to extract metals from secondary resources using hyperaccumulator plants (HA) and produce high value compounds. Agromining has been primarily developed for nickel (Ni) recovery from ultramafic soils. Most often, the dry HAs, containing ca 1 wt% of Ni are burnt to concentrate Ni in ashes (15–20 wt%) and remove organic matter; then the ashes are treated to give Ni metal, oxide or salts. This work was undertaken to investigate the recovery of Ni without any combustion stage in eco-friendly conditions.Ni extraction was tested with two HAs, the former grown in a temperate latitude (A. murale) the latter in a tropical climate (R. bengalensis), using water as an extracting agent in batch reactor, at two solid to liquid (S/L) ratios (4 and 8%). Ni extraction yield was higher from the former HA (90%) than from the latter (50%). Ni concentration in the leachates increased with the S/L ratio. Therefore column experiments were run with A. murale to work with the highest possible S/L ratio. Other main cations (K, Ca, Mg) and dissolved organic compounds were solubilized as well. Knowing that Ni is mainly chelated by malate and citrate in the plant tissues, low molecular weight carboxylic acids (LMWCAs) were analyzed in the leachates; they accounted for 14% of the dissolved organic carbon.The composition of the leachate at thermodynamic equilibrium was computed using the Chess software, dedicated to the simulation of the equilibrium of complex solutions, including gases, minerals, organics and colloids. Results showed that Ni was almost entirely complexed with LMWCAs. Further simulations were conducted to elucidate why Ni could not be simply recovered by precipitation of Ni hydroxide from the leachate. This behavior was interpreted by the contribution of a strong Ni ligand preventing the hydroxide precipitation. Calculations enabled us to obtain the minimum value of the complexation constant.The evidence that Ni can be extracted from HAs by water leaching and a better understanding of the equilibrium of the leaching liquor are important stages for further Ni recovery and purification.

Sustainable approach towards extractive waste management: Two case studies from Italy

Europe is confronted with an increasing risk of supply of critical raw materials (CRM) and secondary raw materials (SRM). Major parts of the economy depend on the supply of raw materials, a fact acknowledged by policymakers and scientists in Europe. Recent economic and geopolitical developments led to the focus on reuse and recycling of waste products to secure supply of raw materials. Consequently, to tackle the supply-risk challenge extractive waste (EW) present in mining dumps should be approached as opportunities as source of raw materials. Interdisciplinary studies are required with respect to correct estimation of raw materials present in extractive waste dumps, identify their reusability, and to measure the threats posed by EW dumps to local population. In present study, site investigation and geochemical analysis was performed to identify the metals present in waste dumps from two abandoned mine sites in Italy. These two sites are 1) Campello Monti, Piedmont used for Ni extraction 2) Gorno, Lombardy used for Zn and Pb exploitation in past. The study also focused on risk analysis to measure effects on human health due to dispersion and transfer of contaminants from waste dumps. In Campello Monti, it was observed that EW was rich in Ni, Co and Cu concentration. It was also observed that there was presence of carcinogenic risk due to As in the area. In Gorno, Zn ,Cd and Ga were found to be present in abundance. It was also noticed that, there was presence of carcinogenic risk (RI > 1 x 10-6) due to arsenic in Gorno, which had an RI equal to 72.2 × 10−6. The present research highlights the need to measure potential value of EW dumps for reusing and measuring environmental impacts. Thus, leading to the sustainable management of waste including both economic and environmental benefits.

Phytotoxicity and microbial respiration of Ni‐spiked soils after field aging for 12 yr

To assess the impact of Ni toxicity in soils after long-term field aging, a coarse-textured soil was spiked with Ni salt at 100, 200, and 400 mg kg-1 Ni concentrations. These soils were aged in the field along with an unspiked (control) soil under natural conditions for 12 yr, after which total soil Ni was measured and tests of Ni extractability by 0.01 M CaCl2 and diethylenetriaminepentaacetic acid (DTPA) were done. Soybean assays and soil respiration tests were performed to determine residual Ni toxicity of the aged contaminated soils. The greatest loss of Ni after 12 yr of aging occurred from the soil spiked with the highest Ni level, but substantial loss of Ni occurred from the lower Ni levels as well. Loss was attributable to leaching as the fraction of readily extractable (by 0.01 M CaCl2 ) Ni diminished with long-term aging. Readily extractable and DTPA-extractable Ni increased with increasing soil spiking levels, but only the latter was linearly proportional to total Ni. Phytotoxicity to soybeans (Glycine max L.) in the field was initially high at all levels of added Ni but diminished over the 12 yr of aging. A greenhouse soybean assay with the 12-yr aged soils confirmed toxicity to be statistically significant at all Ni addition levels and dose-dependent, with 0.01 M CaCl2 -extractable Ni >5 mg kg-1 shown to be measurably phytotoxic to soybeans. Phytotoxicity may have been caused at least in part by the observed inhibition of Mn, Fe, Cu, and Zn uptake by soil Ni. Soil respiration was increasingly inhibited as levels of added Ni increased from 100 to 400 mg kg-1 . Environ Toxicol Chem 2018;37:1933-1939. © 2018 SETAC.

Biocatalytic and chemical leaching of a low-grade nickel laterite ore

Nickel and cobalt recovery from a low-grade nickel laterite ore, supplied from Çaldağ deposit (Manisa, Turkey) were investigated by bio and chemical leaching processes. The fungus, Aspergillus niger was used for biocatalytic leaching experiments. The effects of parameters (solid ratio and sucrose concentration) on the biocatalytic leaching of the ore were initially tested in flasks to obtain the optimum conditions for the A. niger. Then chemical leaching was applied as a comparison to bioleaching, using organic acids (citric, oxalic, acetic and gluconic acids) as well as a mixture of acids. According the results, the maximum dissolution yield of nickel, cobalt and iron were detected respectively as 95.3%, 74.3% and 50.0% by biocatalytic processes which containing 25% (w/v) sucrose and 1% (w/v) solids. The increase in the solid ratio adversely influenced the biocatalytic activity of A. niger. Finally, further tests in reactors (v = 1 and 10 L) were performed using the optimum conditions from the flask tests. The difference in metals recovery between biocatalytic and chemical leaching was significantly important. Bioleaching produced higher Ni and Co extractions (34.3–75.6%) than chemical process.

Survey of Heavy Metal Contamination in Water Sources in the Municipality of Torola, El Salvador, through In Situ Sorbent Extraction

The presence of heavy metals in water resources directly affects consumer health. The quality of surface water resources in Central America is usually low due to the presence of metals and other pollutants. The lack of analytical instrumentation to perform routine monitoring of water has encouraged the development of easy tools to facilitate the determination of heavy metals in waters in remote sites. In this study, we evaluated the use of different sorbents, such as Adsorbsia As600 (titanium dioxide), Iontosorb Oxin, 8-hydroxyquinoline bearing functional groups, and Duolite GT-73, with thiol functionality, for Cd, Ni, Cu, Zn, and Al extraction. It was found that both Adsorbsia As600 and Iontosorb Oxin allowed the adsorption of all metals, and the recovery was achieved using either HCl or ethylenediaminetetraacetic sodium salt (EDTA) solutions. Hence, Adsorbsia As600 was employed for in situ sampling in the metal contamination evaluation of water samples (from 15 wells and nine storage tanks) from the municipality of Torola, Mozarán, El Salvador. The developed procedure allowed all the metals in the samples to be detected, and Ni and Al were found to be above Salvadoran guidelines for drinking water quality.