Pulp Density Research Articles

Role of Glycerol Oxidation Pathways in the Reductive Acid Leaching Kinetics of Manganese Nodules Using Glycerol.

Manganese nodules from ocean bed are potential resources of Cu, Ni, and Co for which land-based deposits are scarce in India. The present work describes a novel approach of using glycerol, a nontoxic biomass-derived reductant, for the reductive acid leaching of manganese nodules. Parameters such as acid concentration, time, temperature, and pulp density were optimized for leaching. The optimal leaching conditions were found to be 10% (w/v) pulp density and 10% (v/v) H2SO4 at 80 °C with 1% (v/v) glycerol yielding >95% of Ni and >98% Cu, Co, and Mn extraction within an hour. Kinetic analysis of the data based on the initial rate method showed that the leaching process was chemical reaction-controlled with an apparent activation energy of 55.47 kJ/mol. Various oxidation intermediates of glycerol formed during leaching were identified using mass spectrometry and Raman spectroscopy, and a probable oxidation pathway of glycerol during the leaching process has been elucidated based on the analysis. Glycerol was oxidized to glyceraldehyde, glyceric acid, tartronic acid, dihydroxyacetone, hydroxy pyruvic acid, glyoxalic acid, oxalic acid, and finally converted to CO2 during leaching. The fast reaction kinetics, near-complete dissolution of manganese, and other associated metals in the nodule can be attributed to the participation of all intermediate products of glycerol oxidation in redox reactions with MnO2, enhancing the overall reduction leaching efficiency.

Study of Nickel Leaching Using Sulfuric Acid and Phosphoric Acid on The Selectivity Nickel Ore

Study of nickel leaching using sulfuric acid and phosphoric acid on the selectivity of low-grade laterite nickel ore under atmospheric conditions has been successfully carried out. In this study, the laterite nickel leaching process was carried out by varying the solution concentration and operating time. The concentrations of sulfuric acid and phosphoric acid solutions were varied at 5 M and 6 M concentrations, while the operating time was varied at 4 hours and 6 hours. For other operating conditions, it is kept constant with an operating temperature of 90 ℃, pulp density 15% w / v, particle size ≤ 200 mesh. After that, the analysis stage was carried out using an atomic absorption spectroscopy (AAS) tool to determine the nickel content in the sample. The results showed that the highest nickel recovery was obtained at the concentration of 5 M sulfuric acid solution of 2.60% and 5 M phosphoric acid of 2.59% with the optimum operating time at 4 hours of operating time.

Recovery of Zinc and Silver from Zinc Acid-Leaching Residues with Reduction of Their Environmental Impact Using a Novel Water Leaching-Flotation Process

Zinc-leaching residue (ZLR) is a strongly acidic hazardous waste; it has poor stability, high heavy metal levels, and releases toxic elements into the environment. ZLR has potential as a valuable resource, because it contains elevated levels of zinc and silver. In this paper, the recovery of zinc (Zn) and silver (Ag) from ZLR wastes from zinc hydrometallurgy workshops using water leaching followed by flotation was studied. During water leaching experiments, the zinc and copper recovery rates were 38% and 61%, respectively. Thereafter, various flotation testing parameters were optimized and included grinding time, reagent dosages, pulp density, flotation time, and type of adjuster. Experimental results demonstrated this flotation method successfully recycled Ag and Zn. A froth product containing more than 9256.41 g/t Ag and 12.26% Zn was produced from the ZLR with approximately 80.32% Ag and 42.88% Zn recoveries. The toxicity characteristic leaching procedure (TCLP) results indicated the water-leaching flotation process not only recycled valuable metals such as zinc and silver in zinc-containing hazardous wastes but lowered the hazardous waste levels to those of general wastes and recycled wastes in an efficient, economical, and environmentally friendly way.

Intensification and optimisation of nickel recovery from spent hydrogenation catalysts via ultrasound-augmented hydrometallurgy

Spent catalysts generated from various processing industries such as those involved in the hydrogenation of fats and oils pose severe environmental issues if not treated and disposed of aptly. In this present work, process intensification was provided by the means of ultrasonic irradiation via an ultrasonic bath to ascertain the positive effects it imparts on the nitric acid and sulphuric acid leaching of spent silica-supported nickel hydrogenation catalysts. The extent of nickel recovered from ultrasound-assisted leaching was compared to that of the conventional mechanical stirring technique, whereby the actual ultrasonic densities of the ultrasound source were determined. Ultrasonic irradiation appreciably enhanced the extraction of nickel from the spent catalyst in all instances due to the physical and chemical effects of acoustic cavitation. In particular, sonication resulted in the expedited extraction of Ni, allowing a time reduction of 2 h in recovering ca. 70% Ni. Furthermore, it was also discovered that nitric acid was a more efficient leaching agent than sulphuric acid, achieving an improvement of ca. 20% in recovering Ni at 70 °C under ultrasonic conditions. Additionally, process optimisation was executed by adopting the response surface methodology, in which the modelled optimal conditions were ultrasonic bath amplitude = 67%, leaching temperature = 60 °C, nitric acid concentration 12.5 vol% and pulp density = 7.5%. Ultimately, the Ni recovery recorded under the optimal conditions was 99.37% in 2 h. Finally, an approximate economic analysis was performed to ascertain the recovery costs of nickel using the ultrasonic method. This study demonstrated the beneficial usage of ultrasound technology in the process intensification of hydrometallurgy, which could be employed on an industrial scale for higher recovery efficiencies and improved sustainability.

Efficient separation of zinc from zinc containing copper sulfide concentrate by chemical leaching

As the most abundant copper containing resource and zinc containing resource, chalcopyrite and sphalerite/marmatite commonly coexist as Cu-Zn mixed ores in deposits. However, it is difficult to completely separate sphalerite and chalcopyrite by flotation, thus resulting in the existence of zinc impurity in copper concentrate. Sphalerite/marmatite existed in copper sulfide concentrate as impurity may lead to severe damage of the smelting equipment, and cause the waste of copper and Zn resources, it will also decrease of the sale price of copper concentrates. Therefore, the deep separation of zinc from zinc bearing copper sulfide concentrate is of great significance. In this work, selective chemical leaching was developed to efficiently remove zinc from zinc containing copper sulfide concentrate. Under the optimal condition (i.e., sulfuric acid concentration exceed 100 g/L, temperature of 80 °C, pulp density of 10%, leaching time of 48 h), over 85% Zn was extracted into the leaching solution together with only about 10% Cu and Fe, according to the leaching experiment. Leaching slurry had good solid-liquid separation characteristics, and zinc can be further effectively recovered from the leaching solution. According to X-ray diffraction (XRD) and scanning electron microscope/energy dispersive spectrometer (SEM/EDS) analysis, chalcopyrite was the main mineralogical phase in the residues, which can be regarded as high quality copper concentrate for metallurgy. Accordingly, a new process for deep and efficient separation of Cu-Zn mixed ores has been proposed.

Multidetector CT and cone-beam CT have substantial agreement in detecting dental and sinus abnormalities in equine cadaver heads.

The performance of cone-beam CT (CBCT) systems compared to conventional helical multidetector CT (MDCT) imaging of the equine head is unknown. The aim of this prospective, method-comparison study was to compare the ability of CBCT and MDCT to detect abnormalities in equine cadaver heads. Eleven equine cadaver heads were scanned using a CBCT scanner and a 64-slice MDCT scanner. Consensus evaluations for CBCT and MDCT scans were performed by three observers. Identified abnormalities were grouped into subcategories with a focus on dental abnormalities. Kappa agreement values between detected abnormalities for CBCT and MDCT methods were calculated. Of 468 teeth evaluated, 122 (26.1%) were found to have abnormalities (including in 58 infundibula and 7 pulps) using MDCT and 105 (22.4%) were found to have abnormalities (including in 52 infundibula and 2 pulps) using CBCT. The agreement between CBCT and MDCT was almost perfect for overall detection of dental abnormalities (k=0.90) with k=1 for diastema k=0.95 for clinical crown abnormalities, and k=0.93 for infundibular abnormalities. However, the detection of pulp changes by CBCT was only moderate k=0.44. Increased scatter radiation, non-calibrated Hounsfield Unit and artefacts in CBCT images made accurate identification of the pulp density difficult. In conclusion, CBCT results were similar to conventional MDCT for the majority of dental abnormalities, however, pulp abnormalities were not reliably identified using CBCT, potentially limiting its clinical use for detecting endodontic disease in its current form. Further comparison with more cases with confirmed dental disease and studies in clinical cases are warranted.

Flotation performance analysis on coal washery rejects

The coal washery rejects cause major environmental problems in various parts of the globe. Nearly 1 Mt of coal rejects discarded as waste, is accumulated per annum in India, during washing or cleaning of raw coal. Cleaning coal, especially washery rejects, has posed a major challenge to the recovery of fine coal. Froth flotation is a better choice for processing coal washery rejects. In this study, flotation studies are attempted on the coal slurry received from Sudamdih coal washery, Jharkhand, India. A statistical design package (Minitab V17) was used to study the effect of process variables like collector and frother dosages on the responses. Regression equations for froth height, froth density, recovery and ash content of clean coal were developed. The coefficient of correlation (R2) values between the experimental and the predicted values of the flotation responses was found to be greater than 0.98 for all the models. Clean coal product was analyzed for recovery, froth height, and ash content by varying pulp densities. Results show that the coal slurry sample could be evaluated with acceptable recovery via flotation. Clean coal with an ash content of 17.2% is obtained with a 70% recovery from 35.5% ash. The cleaned coal can be used in powder coal-consuming industries.

Sustainable treatment of bimetallic (Ag–Pd/α-Al2O3) catalyst waste from naptha cracking process: An innovative waste-to-value recycling of precious metals

Bimetallic (Ag–Pd/α-Al2O3) catalysts are essentially applied to naptha-cracking process with a controlled CO2 emission. After losing the catalytic properties in long run, the landfilling disposal of spent catalysts poses severe stress to the environment and deprivation of precious metals. Therefore, an innovative solvo-chemical recycling approach that involving the solid-liquid and liquid-liquid mass transfer phenomena was studied. The parametric variations for dissolving precious metals yielded >98% efficiency at a lixiviant concentration, 2.0 mol L−1 HCl; pulp density, 20% (wt./vol.); agitation speed, 300 rpm, temperature, 90 °C, and duration, 60 min. The activation energy of silver (6.9 kJ mol−1) and palladium (11.9 kJ mol−1) leaching indicated that the process was governed by a diffusion-controlled mechanism. Subsequently, silver and palladium were separated using 0.15 mol L−1 LIX 84-I at different acid concentration that yielding the maximum separation factor (β(Ag/Pd) = 12,501) at 2.0 mol L−1 HCl. Stripping of separately (Ag/Pd)-loaded organic solutions with different solutions of HNO3, (NH4)2SO4, and CH4N2S showed higher affinity for thiourea, yielding 56%, 38%, and 87% efficiency, respectively. Thus the counter-current extraction at an organic-to-aqueous (O:A) ratio of 1:2.5 and stripping with 0.5 mol L−1 CH4N2S at an O:A ratio of 2:1 yielded a five-fold enrich solutions of precious metals (75.2 mg L−1 Ag and 188.5 mg L−1 Pd) with a purity of >99.9%. The process essentially aims to Goal 12 under the United Nations’ Sustainable Development Goals for sustainable recycling of industrial wastes consequently conserving the natural mineral reserves.

Distribution of scandium in red mud and extraction using Gluconobacter oxydans

The aim was to study bioleaching of rare earth elements from red mud by a chemoorganotrophic microorganism, and to investigate the microbe-mineral interactions. Red mud is a promising resource for scandium, whose concentration was 92 and 54 mg/kg in two samples from Germany and India, respectively; however, both showed appreciably high concentration of zirconium. A gluconic acid-producing bacterium, Gluconobacter oxydans (DSMZ 46616), was used in the bioleaching experiments under parametric variation of inoculum concentration, pulp density, and culture adaptation. At a solid load of 10% (w/v) red mud with 10% (v/v) bacterial inoculum at 37 °C, a maximum solubilisation of 83% and 94% Sc was observed after 18–20 d of incubation for Indian and German red mud, respectively. The total amount of gluconic acid excreted by the bacteria increased with an increase in pulp density up to 10% (w/v). After bioleaching, SEM-EDAX analysis of the solid residue depicted enrichment of zirconium associated with the silicate matrix, and the bacterial cells were adhered to the major mineral matrix.

Leaching of metals from spent fluid catalytic cracking catalyst using Acidothiobacillus ferrooxidans and comparing its leaching efficiency with organic and inorganic acids

Bioleaching is an eco-friendly alternative for the extraction of metals from the spent fluid catalytic cracking catalyst (SFCCC). Acidothiobacillus ferrooxidans (A. ferrooxidans) are the most widely reported bacteria in leaching but remained unexplored for SFCCC till date. The present study proposes a cleaner, environmentally friendly process to leach metals from SFCCC by A. ferrooxidans. Batch bioleaching of metals was carried out with unadapted and adapted A. ferrooxidans. Experiments were performed by varying the pulp density (PD) (1–20%) at two different initial Fe(II) concentrations i.e. 2 g/L [M2Fe(II)] and 8.84 g/L [M8.84Fe(II)]. The results showed that adapted A. ferrooxidans leached out metals better than unadapted ones. Even though the loss of Iron to Jarosite formation was higher in M8.84Fe(II) than in M2Fe(II), leaching remained higher in M8.84Fe(II). Jarosite formation was minimized by maintaining the pH of the medium to 2 ± 0.1. Maximum leaching efficiency was observed at 1% PD. At this concentration. A. ferrooxidans growth was triggered which increased the production of Fe(III), thereby increasing leaching efficiency. Increase in PD led to a decrease in metal leaching efficiency. The maximum leaching observed by A. ferrooxidans is Al (35%), Ti (14%), Ni (27%) and V (56.5%). The amount of Al leached (70 mg/gm of SFCCC) suggests SFCCC be the potential secondary source of Al compared to popular secondary sources such as red mud and other spent catalysts. Al and V were better leached by A. ferrooxidans while organic acids were more suitable to extract Ti and Ni from SFCCC.

Effect of mechanical activation on terbium dissolution from waste fluorescent powders

Rare earth elements (REEs), independently by the economic value, have a strategic importance and are involved, as critical materials, in the competition for their supply. An innovative process with the introduction of a preliminary physicochemical treatment was proposed. The mechanical activation of waste of fluorescent powders was performed by a vibratory disc mill at different experimental conditions to optimize the process. The mechanical forces induced to the powders cause crystal structure defects with a consequent increase of rare earths leachability. Factorial experimentations and analysis of variance were studied to determine the significant effects of the investigated factors (mechanical activation time, sulfuric acid concentration, pulp density and leaching temperature), especially for terbium dissolution. The preliminary activation allows to increase terbium dissolution of 35%. Then, according to the best conditions the subsequent operations of precipitation and calcination were performed obtaining a purity of 98.3% as rare earth oxides. Based on the experimental results, the flowsheet for rare earths recovery has been proposed and implemented by SuperPro Designer, a simulation software for process analysis and mass-energy balances. Finally, this paper reports a comparison between the present process with the mechanical pre-treatment and the alternative method based on thermal pre-treatment.

The environmental impact assessment of gold extraction processes for discarded computer RAM: a comparative study of two leaching chemicals

Electrical and electronic equipment waste (WEEE) problems should be set as a priority in Thailand due to unpleasant operations. E-waste mismanagement caused by illegal transport of WEEE has intensified public health and environmental concerns. Computers are processed in recycling industries, but they still contain vulnerable metal remnants, such as gold. High-grade components, such as Random-Access Module (RAM), for example, are often extracted by hydrometallurgical processes through different leaching chemicals along with their related methods. Gold leaching agents, including aqua regia and cyanide-based solutions, were considered to extract gold from computer RAM in this study. Environmental impacts of the two extracting processes were investigated using material flow analysis and life cycle assessment, based on 1 kg of recovered gold. The effect of pulp density was also measured. The comparison between the two leaching processes without waste management demonstrated that the cyanide-based solution provided 8.5 times lower in terrestrial ecotoxicity and 6.4 times lower in human carcinogenic toxicity than aqua regia due to the lower overall chemical consumption. Nevertheless, proper wastewater treatments and a combination of incineration and landfill for solid waste treatment are potential options to minimize these impacts.

Bioleaching of vanadium by Acidithiobacillus ferrooxidans from vanadium-bearing resources: Performance and mechanisms

Bioleaching is promising to meet the demand of strategic vanadium both economically and environmentally. Whereas the combination of bioleaching with traditional techniques is of great interest, little is known on bioleaching of vanadium from abundant vanadium-bearing resources utilized/produced in existing processes. This study investigated the bioleaching of vanadium from vanadium-titanium magnetite, steel slag, and clinker, which are common raw mineral and intermediates used in conventional vanadium extraction process. Clinker had greater leachability by Acidithiobacillus ferrooxidans, compared to vanadium-titanium magnetite and steel slag. Pulp density, inoculum volume, initial pH and initial Fe2+ concentration had influencing effects on this bioleaching process. Under optimal condition with 3% pulp density, 10% inoculum volume, initial pH at 1.8, and 3 g/L initial Fe2+ concentration, the bioleaching of clinker achieved the maximum vanadium leaching efficiency of 59.0%. Both X-ray fluorescence and energy dispersive spectroscopy analysis confirmed the reduction of vanadium content in the solid residues after leaching. The results of Community Bureau of Reference sequential extraction suggested that vanadium in acid-soluble and oxidizable phase was more easily leachable. This study is helpful to develop sustainable and practical techniques for vanadium extraction from abundant raw materials and step forward in combining bioleaching with traditional process.

O2-enriched microbial activity with pH-sensitive solvo-chemical and electro-chlorination strategy to reclaim critical metals from the hazardous waste printed circuit boards

An innovative process integration for the sustainable recovery of critical metals from waste printed circuit boards (WPCBs) is demonstrated. In the acid pre-treatment of WPCBs, > 95% of highly toxic metals lead and tin could dissolve after 240 min of contact in 4.0 mol L−1 HNO3. Thereafter, the microbial activity of Sulfobacillus thermosulfidooxidans (strain RDB) under intense aeration is found favorable for base metals’ liberation. ~92% copper, 89% nickel, and 93% zinc get extracted at the optimal condition of O2-mixed-aeration, 30%; pulp density, 10 g L−1; aeration rate, 0.5 L min−1; sulfur dosage, 2%; temperature, 45 °C; and duration, 21 days. Quantitative separation of base metals is achieved using ketoxime as a function of equilibrium pH that yielding pH0.5 order: Cu (1.45) < Ni (5.7) < Zn (8.1). The residual gold from WPCBs is uniquely leached (~99% efficiency) in brine solution (2.0 mol L−1 NaCl) under the electro-chlorination rate, 0.62 mmol min−1; dissolution pH, 1.0; pulp density, 20 g L−1; temperature, 30 °C; and time, 60 min. Subsequently, gold from brine solution is solvated with tri-butyl-phosphate at pHeq, ≤ 0.5, forming [2(RP=O)·HAuCl4·H2O]¯ complex in the organic phase. Finally, > 99% of high-purity gold is stripped from loaded organic while contacting ammoniacal thiosulfate solution in two-stages of counter-current flow.

Bioleaching of iron from laterite soil using an isolated Acidithiobacillus ferrooxidans strain and application of leached laterite iron as Fenton's catalyst in selective herbicide degradation.

A novel isolated strain Acidithiobacillus ferrooxidans BMSNITK17 has been investigated for its bioleaching potential from lateritic soil and the results are presented. System conditions like pH, feed mineral particle size, pulp density, temperature, rotor speed influences bioleaching potential of Acidithiobcillus ferrooxidans BMSNITK17 in leaching out iron from laterite soil. Effect of sulfate addition on bioleaching efficiency is studied. The bioleached laterite iron (BLFe’s) on evaluation for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba exhibits 94.24% of ametryn degradation and 92.45% of dicamba degradation efficiency. Fenton’s oxidation performed well with the acidic pH 3. The study confirms the role of Acidithiobacillus ferrooxidans in leaching iron from lateritic ore and the usage of bioleached lateritic iron as catalyst in the Fenton’s Oxidation.

THE INTRODUCED STRAWBERRY (FRAGARIA×ANANASSA DUCH.) VARIETIES AS A PROMISING BREEDING MATERIAL

The integrated assessment of introduced strawberry varieties was held in order to identify the gene sources with high level economically important characters for their use in breeding. The biological objects of research were 69 strawberry accessions. As a result of a long-term comprehensive assessment of the genetic collection of introduced strawberry varieties according to the main economically valuable traits in various weather conditions, a source with the highest and stable level of a complex of priority traits was identified. This is the variety Maya with a large-fruited (&gt;25 g) and high productivity (&gt;500 g/plant). Sources of very early (+5 days, Flair variety) and late (-16 days, Malwina variety) ripening periods introduced from the Netherlands have been revealed. The study of everbearing varieties made it possible to identify the variety San Andreas (USA) as source with the most stable level of the multiple fruiting trait regardless of the duration of the photoperiod. All of the above sources are characterized by a number of valuable features that meet the requirements of the consumer market: pulp density, gloss on the surface, high marketability during transportation and dessert taste. The response of identified varieties to low temperature stressors in prewinter and winter periods showed a wide reaction rate and a high regeneration ability to plant biomass.

A Cross-Sectional Cohort Study of the Effects of FGF23 Deficiency and Hyperphosphatemia on Dental Structures in Hyperphosphatemic Familial Tumoral Calcinosis.

ABSTRACTHyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder caused by mutations in FGF23, GALNT3, KLOTHO, or FGF23 autoantibodies. Prominent features include high blood phosphate and calcific masses, usually adjacent to large joints. Dental defects have been reported, but not systematically described. Seventeen patients with HFTC followed at the National Institutes of Health underwent detailed clinical, biochemical, molecular, and dental analyses. Studies of teeth included intraoral photos and radiographs, high‐resolution μCT, histology, and scanning electron microscopy (SEM). A scoring system was developed to assess the severity of tooth phenotype. Pulp calcification was found in 13 of 14 evaluable patients. Short roots and midroot bulges with apical thinning were present in 12 of 13 patients. Premolars were most severely affected. μCT analyses of five HFTC teeth revealed that pulp density increased sevenfold, whereas the pulp volume decreased sevenfold in permanent HFTC teeth compared with age‐ and tooth‐matched control teeth. Histology revealed loss of the polarized odontoblast cell layer and an obliterated pulp cavity that was filled with calcified material. The SEM showed altered pulp and cementum structures, without differences in enamel or dentin structures, when compared with control teeth. This study defines the spectrum and confirms the high penetrance of dental features in HFTC. The phenotypes appear to be independent of genetic/molecular etiology, suggesting hyperphosphatemia or FGF23 deficiency may be the pathomechanistic driver, with prominent effects on root and pulp structures, consistent with a role of phosphate and/or FGF23 in tooth development. Given the early appearance and high penetrance, cognizance of HFTC‐related features may allow for earlier diagnosis and treatment. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Bioleaching and ecological toxicity assessment of carbide slag waste using Acidithiobacillus bacteria

Abstract Carbide slag generated from industrial sites can contain many organic and inorganic impurities such as toxic metals and organic compounds, which should be treated before disposal. Bioleaching using Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and their combination was investigated. The effects of important factors including pH and pulp density were assessed. It was found that under optimal conditions 100% Zn, 41.9% Ba, 98.5% Ni and 97.8% Li were extracted with the mixed culture of Acidithiobacillus at pH 1 with pulp density 0.5% (w/v) after 14 days. To ensure risk reduction of the carbide waste for the soil environment, ecological risk criteria and plant seed germination potentials were evaluated. The results showed that bioleaching significantly reduced slag toxicity, and plant seed germination from leached waste was observed.

Bioleaching of Uranium Tailings as Secondary Sources for Rare Earth Elements Production

Tailings from inactive uranium mine sites represent a potential secondary source of rare earth elements (REEs). For this study, two mine tailings (DT and RAT) from restored uranium sites in Ontario, Canada, were used. Bioleaching experiments were conducted with a mix of native sulfur- and iron-oxidizing bacteria to test the solubilization of REEs, U and Th at different temperatures (20, 30 and 40 °C). The selective recovery of REEs from bioleaching solution was evaluated using different ion exchange resins. The mineralogical characterization revealed that DT tailings were mainly composed of quartz, pyrite, gypsum and silicates, whereas RAT tailings were mainly composed of quartz. The maximum solubilization of heavy and light REEs (HREEs and LREEs, respectively), Th and U reached 54%, 6%, 60% and 51% for RAT after 35 days at pH 2, T = 30 °C and pulp density = 10% (w/v). Higher extraction yields were obtained for DT, with 58% of HREEs, 14% of LREEs, 85% of Th and 89% of U solubilized under the same conditions. The use of Lewatit TP272 resin for the recovery of Sc (94%) and U (99%) followed by the Lewatit SP112 resin for the recovery of Th (57%) and REEs (81% LREEs and 65% HREEs) seemed a promising method for the co-extraction of the key elements from the bioleaching solution.

Effect of pulp density on the bioleaching of metals from petroleum refinery spent catalyst.

Bioleaching is one of the well-known methods of metal recovery with Environmental benefits. This process has been extensively used for combating improper waste management issues along with metal reclamation. The aim of this study is to bioleach spent petroleum refinery catalyst at variant pulp densities (PD) (5, 10 and 15%) using microorganisms in acidic pH (1.5-1.6) and mesophilic temperature (30-35°C). The study includes leaching yields of metals like nickel, molybdenum, copper and aluminum. The three bioleaching experiments with different pulp densities yielded a maximum of more than 90% nickel, 73% copper, 87% molybdenum and 24% aluminum. The results are validated 5, 10, and 15% pulp density and the result is validated with pH, Redox potential, microbial population, sulphate concentration and ferrous iron, concentration. The time saving due to faster nickel dissolution using iron and sulphur oxidizing microorganisms would be economical for the bioleaching process.