Efficient Recovery of Rare Earth Elements and Zinc from Spent Ni–Metal Hydride Batteries: Statistical Studies

Hormesis and Low Toxic Effects of Three Lanthanides in Microfungi Isolated from Rare Earth Mining Waste in Northwestern Russia

The low-dose toxicity of chloride and nitrate salts of three lanthanides (La, Ce and Nd) was tested on six microfungal species. Five of them (Geomyces vinaceus, Aspergillus niveoglaucus, Pseudogymnoascus pannorum, Penicillium simplicissimum and Umbelopsis isabellina) were isolated from the loparite ore tailings on the Kola Peninsula, northwestern Russia. Sydowia polyspora was a control strain. In the case of nitrate salts, the toxicity of REEs to four of six microorganisms was significantly (p < 0.5) lower compared to chloride salts. In this case, nitrates can play the role of exogenous nutrients, compensating for the toxic effect of REEs. Interestingly, U. isabellina only showed an opposite response, indicating the highest toxicity of nitrate (IC5 = 9-20 mg/L) REEs' salts compared to chlorides (IC5 = 80-195 mg/L) at low concentration levels. In addition, treatment with lanthanides showed a "hormesis effect" on fungal growth with stimulation at low doses and inhibition at high doses. However, U. isabellina and S. polyspora demonstrated the absence of hormetic response under the treatment of REEs' nitrate salt. Taking into account the specific hormetic responses and high tolerance of P. simplicissimum and U. isabellina to lanthanides, our findings may be useful in the assessment of the potential application of the selected fungi to bioremediation and REE bioleaching.

Recovery of W(VI) from Wolframite Ore Using New Synthetic Schiff Base Derivative

A new synthetic material, namely, (3-(((4-((5-(((S)-hydroxyhydrophosphoryl)oxy)-2-nitrobenzylidene) amino) phenyl) imino) methyl)-4-nitrophenyl hydrogen (R)-phosphonate)), was subjected to a quaternary ammonium salt and named (HNAP/QA). Several characterizations, such as FTIR spectrometry, ¹H-NMR analysis, ¹³C-NMR analysis, ³¹P-NMR Analysis, TGA analysis, and GC-MS analysis, were performed to ensure its felicitous preparation. HNAP/QA is capable of the selective adsorption of W(VI) ions from its solutions and from its rock leachate. The optimum factors controlling the adsorption of W(VI) ions on the new adsorbent were studied in detail. Furthermore, kinetics and thermodynamics were studied. The adsorption reaction fits the Langmuir model. The sorption process of the W(VI) ions is spontaneous due to the negative value of ∆G° calculated for all temperatures, while the positive value of ∆H° proves that the adsorption of the W(VI) ions adsorption on HNAP/QA is endothermic. The positive value of ∆S° suggests that the adsorption occurs randomly. Ultimately, the recovery of W(IV) from wolframite ore was conducted successfully.

Recovery of vanadium and nickel from heavy oil fly ash (HOFA): a critical review

Heavy oil fly ash "HOFA" is the fly ash generated in power stations using heavy oil as fuel. HOFA is considered a hazardous waste because it contains considerable amounts of heavy metals. However, it contains significant amounts of vanadium "V" and nickel "Ni", which are precious metals for manufacturing processes. This paper presents a critical review of various approaches described in the literature for the recovery of V and Ni from HOFA, including processes of leaching, chemical precipitation, solvent extraction, and ion exchange. The optimum operational parameters and their effects on recovery efficiency are discussed. The digestion mixtures of strong mineral acids used for dissolving all metals present in HOFA are also highlighted. The leaching processes of V and Ni use mainly acidic and alkaline solutions. Bioleaching is a promising environmentally friendly approach for the recovery of V and Ni through using appropriate bacteria and fungi. After leaching, V and Ni compounds are recovered and purified using various techniques, including chemical precipitation, solvent extraction, and ion exchange. In most cases, V and Ni are recovered as thermally decomposable compounds that undergo calcination to produce V₂O₅ and NiO. Eventually, V and Ni are recovered as pure oxides in most approaches, but pure metals are obtained in exceptional procedures.

Recovery of Rare Earth Elements from NdFeB Magnets by Chlorination and Distillation

A sustainable separation concept for large-scale recycling of NdFeB magnets under atmospheric pressure was developed by utilizing a combination of two separation concepts known from the literature: (I) selective pre-separation by in situ chlorination and evaporation of ground oxidized NdFeB material and (II) subsequent distillation for high-purity recovery of all recyclable chlorinated material components, especially its Rare Earth Elements (REEs). Theoretically, simplified estimations of the time conversion curves at 1173 K, 1273 K, and 2000 K of a single particle resulted in the idea of realizing chlorination in some kind of combustion chamber, fluidized bed, or continuous combustion chamber. After chlorination, all non-volatile components, such as REE chlorides, are condensed out of the vapor phase in a single-stage phase separator. For subsequent fine separation by distillation (1292–1982 K for Rare Earth Chlorides and 418–867 K at 2500 kPa for boron and zirconium chloride recovery), simplified simulations were performed in a total-reflux column under ideal phase equilibrium conditions to show the estimated minimum separation effort. Using two composition examples from the literature, high-purity separation of the major Rare Earth Chlorides within a twelve-stage distillation column as a residual heavy boiling product has been demonstrated to be potentially technically feasible.

Rare-Earth Elements Extraction from Low-Alkali Desilicated Coal Fly Ash by (NH4)2SO4 + H2SO4

Coal fly ash (CFA) obtained from pulverized coal furnaces is a highly refractory waste that can be used for alumina and rare-earth elements (REEs) extraction. The REEs in this type of CFA are associated with a mullite and amorphous glassy mass that forms a core-shell structure. In this research, it was shown that complete dissolution of amorphous aluminosilicates from the mullite surface with the formation of the low-alkali mullite concentrate prior to sulfuric acid leaching with the addition of (NH₄)₂SO₄ helps to accelerate the extraction of REEs. The extraction degree of Sc and other REEs reaches 70-80% after 5 h of leaching at 110 °C and acid concentration of 5 M versus less than 20% for the raw CFA at the same conditions. To study the leaching kinetics of the process, the effects of temperature (90-110 °C), liquid-to-solid ratio (5-10), and leaching time (15-120 min) on the degrees of Al and rare-earth elements (REEs) extraction were evaluated. After 120 min of leaching at 110 °C and L/S ratio = 10, the extraction of Al was found to be lower than 30%. At the same time, total REEs (TREE) and Fe extraction were greater than 60%, which indicates that a part of the TREE was transferred into the acid soluble phase. After leaching, the residues were studied by laser diffraction (LD), X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM-EDS) to evaluate the leaching mechanism and the solubility of Al- and Fe-containing minerals, such as mullite, hematite, and amorphous aluminosilicate.

Potentially harmful elements in urban surface deposited sediment of Ekaterinburg, Russia: Occurrence, source appointment and risk assessment

In this study, the human health risks of potentially harmful elements (PHEs) in urban surface deposited sediments (USDS) were examined by collecting urban dust samples, measuring their PHE concentrations, and using index evaluation. About 35, 12 and 16 samples are represented a green zones, roads, driveways and sidewalks in residential areas of Ekaterinburg, respectively. The dust fraction (0.002-0.1 mm) was obtained by sieving, filtration, and decantation process. Total concentrations of 10 PHEs were measured using inductively coupled plasma mass spectrometry. The highest concentrations of Pb were found in USDS from green zones, while Fe, V, Mn, Co, Ni, Sn, and Sb on roads, Cu and Zn on driveways and sidewalks. The contamination levels in the investigated land-use areas were studied, where the highest contamination was contributed from Sb in the driveways and sidewalk. Moreover, the pollution in the studied zones was a high load, contributing to anthropogenic activities and traffic emissions. No non-cancerogenic risk was attributed from the PHEs based on the results of health indices (HI < 1) for both adult and children, except Co and Ni which has HI > 1 for children. The total carcinogenic risk (TLCR) in all urban landscape areas is defined as a high potential inhalation exposure and a low potential ingestion and dermal exposure.

A Novel Triazole Schiff Base Derivatives for Remediation of Chromium Contamination from Tannery Waste Water

Tannery industries are one of the extensive industrial activities which are the major source of chromium contamination in the environment. Chromium contamination has been an increasing threat to the environment and human health. Therefore, the removal of chromium ions is necessary to save human society. This study is oriented toward the preparation of a new triazole Schiff base derivatives for the remediation of chromium ions. 4,4′-((1E)-1,2-bis ((1H-1,2,4-triazol-3-yl) imino)ethane-1,2-diyl) diphenol was prepared by the interaction between 3-Amino-1H-1,2,4-triazole and 4,4′-Dihydroxybenzil. Then, the produced Schiff base underwent a phosphorylation reaction to produce the adsorbent (TIHP), which confirmed its structure via the different tools FTIR, TGA, ¹HNMR, ¹³CNMR, GC-MS, and Phosphorus-31 nuclear magnetic resonance (³¹P-NMR). The newly synthesized adsorbent (TIHP) was used to remove chromium oxyanions (Cr(VI)) from an aqueous solution. The batch technique was used to test many controlling factors, including the pH of the working aqueous solution, the amount of adsorbent dose, the initial concentration of Cr(VI), the interaction time, and the temperature. The desorption behaviour of Cr(VI) changes when it is exposed to the suggested foreign ions. The maximum adsorption capacity for Cr(VI) adsorption on the new adsorbent was 307.07 mg/g at room temperature. Freundlich’s isotherm model fits the adsorption isotherms perfectly. The kinetic results were well-constrained by the pseudo-second-order equation. The thermodynamic studies establish that the adsorption type was exothermic and naturally spontaneous.

Selective Recovery of Cadmium, Cobalt, and Nickel from Spent Ni–Cd Batteries Using Adogen® 464 and Mesoporous Silica Derivatives

Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H2SO4, solid/liquid (S/L) 1/5 at 80 °C for 6 h. The leaching efficiency of Fe, Cd, and Co was nearly 100%, whereas the leaching efficiency of Ni was 95%. The recovery of the concerned elements was attained using successive different separation techniques. Cd(II) ions were extracted by a solvent, namely, Adogen® 464, and precipitated as CdS with 0.5% Na2S solution at pH of 1.25 and room temperature. The extraction process corresponded to pseudo-2nd-order. The prepared PTU-MS silica was applied for adsorption of Co(II) ions from aqueous solution, while the desorption process was performed using 0.3 M H2SO4. Cobalt was precipitated at pH 9.0 as Co(OH)2 using NH4OH. The kinetic and thermodynamic parameters were also investigated. Nickel was directly precipitated at pH 8.25 using a 10% NaOH solution at ambient temperature. FTIR, SEM, and EDX confirm the structure of the products.