ABSTRACT Various pyrometallurgical processes to produce TiO2 slag have been reviewed, focusing on the solid-state reduction aspects of ilmenite. Most of the upgradation processes from ilmenite to titania slag involve direct smelting of ilmenite and, therefore, are generally considered energy-intensive and not environmentally friendly. On the other hand, the pre-reduction of ilmenite, followed by the smelting processes, is advantageous because of its low energy consumption, furnace stability, and negligible slag foaming. In this paper, the impact of different reducing agents on the ilmenite reduction kinetics has been reviewed. The gas-based reduction techniques, primarily with hydrogen or hydrogen-enriched syngas as reductants, show better reaction kinetics and are more environment-friendly than the carbon-based reduction of ilmenite. Hence, the titania slag production from ilmenite can be made efficient and sustainable by incorporating the pre-reduction concept and gas-based reduction for the pre-reduction step. Numerous ways of improving ilmenite pre-reduction have been investigated intensively, featuring pre-oxidation, additives, mechanical activation, and microwave-assisted reduction. Since ilmenite is a good microwave absorber and the microwave-assisted reduction process provides faster kinetics, the method is also very promising for large-scale applications.

ABSTRACT Titanium dioxide, which is found in the mineral ilmenite as a feedstock, has the highest refractive index of any known white pigment. Therefore, two commercial techniques have been developed to produce TiO2 pigment using pyrometallurgical processes, such as melting cast iron while shrinking ilmenite. Although the leaching of ilmenite with sulfuric or hydrochloric acids to remove impurities like iron to create TiO2 pigment or SR is included in the second group of methods. In addition to studying various methods of pre-treatment acid leaching of ilmenite, such as oxidation, reduction, mechanical activation, KOH decomposition, alkali roasting, and the Becher process, with assessing the impact of leaching variables including temperature, duration, acid concentration, particle size, acid to ilmenite ratio, extra stirring speed, and other additional factors. This research attempts to explain these aims with a review of recent articles on ilmenite leaching, which means accelerating iron extraction and Ti dissolving to obtain a high content of TiO2 in the final process with low cost, ecologically friendly, and a limited number of contaminants that can be used in the pigment industry or other usage. As well, the mechanism of HCl and H2SO4 acid leaching of ilmenite has been precisely investigated.

ABSTRACT Cationic reverse flotation of kaolinite from bauxite is an alternative to adequate high silica bauxites to the specifications of the Bayer process. However, the presence of clay minerals influences the slurries rheology decreasing the flotation performance. The objective of this work was to investigate the use of ultrasonic pre-treatment on kaolinite flotation and contrast it with the traditionally used chemical dispersant. Two bauxite samples were characterized in terms of chemical and mineralogical composition, as well as particle size distribution. Flotation was accomplished after conditioning with sodium polyacrylate and/or pre-treatment in ultrasound. Determinations of viscosity, sedimentation yield, and screening followed by the analysis of available alumina and reactive silica were also conducted. By increasing the concentration of solids to more than 20 wt.%, the slurry behavior changed from a Newtonian to a non-Newtonian behavior, the viscosity increased, and the flotation performance decreased. The use of chemical dispersant and ultrasonic pre-treatment increased the flotation performance. The ultrasound had a more marked effect in slurries with higher concentrations of solids. This result is related to the synergic effect of particle dispersion and reduction of the slime coating promoted by kaolinite onto gibbsite particles.

ABSTRACT The high energy consumption of high-intensity conditioning (HIC) limits the popularization of this technology although it has been validated as an effective way to improve flotation. In this study, an economic and efficient pulp conditioning method for a low-quality coarse coal slime was innovatively proposed by comparing four different conditioning-flotation processes. It is found that the energy consumption per unit combustible recovery of conditioning using emulsified diesel was reduced by 8.3% compared with that of the conventional conditioning. This is attributed to the energy reduction of the optimum conditioning speed decreased from 2100 rpm to 1300 rpm, and a negligible energy consumed in the preparation of emulsified diesel. Results showed that when using an emulsified diesel, flotation performance was further improved and less affected by conditioning speed but more by conditioning time. Moreover, flotation is no longer affected by the degree of surface cleaning. It was indicated that the dispersion of collector is crucial for HIC. This study provides a technical reference for the development of economic and efficient conditioning equipment.

ABSTRACT The kinetics of the leaching of natural magnesite with hydrochloric or nitric acid has been studied. Relatively high values of the apparent activation energy (from 46.5 to 70.0 kJ mol−1), but especially the low values of the apparent reaction order for H+ cations, n , have shown that the whole process is controlled by the surface chemical reaction. The value of n decreases continuously with increasing activity of H+ cations in the range of pH 5 to −1.4. At pH < 2.6 there is a transition from the kinetic regime characterized by n ≅ 0.5 to another one with n close to zero.

ABSTRACT Recovery of nickel and cobalt from laterite ores is important to meet the demand for these metals. In this work, a process was developed for the separation of metal ions from synthetic sulfate leach liquor of laterite ores containing Fe(III), Al(III), Ni(II), Co(II), Ca(II), Mg(II), and Mn(II). First, Fe(III) and Al(III) were removed by precipitation of their hydroxides by adjusting solution pH and then Mn(II) was removed from the filtrate by oxidative precipitation with NaClO. Sequentially, Co(II) and Ni(II) from the filtrate containing Mg(II) and Ca(II) were separated by selective precipitation of CoS and NiS by adding Na2S solution, leaving Ca(II) and Mg(II) in the filtrate. The mixed precipitates of CoS and NiS were completely dissolved by 0.1 M HCl solution containing NaClO. Co(II) can be separated from Ni(II) present in the HCl solution by either oxidative precipitation with NaClO or selective extraction with saponified Cyanex 272. Optimum conditions for these procedures were obtained. Continuous experiments indicated that the purity of Co(II) and Ni(II) solutions was higher than 99%.

ABSTRACT With the rapid growth of the electric vehicle (EV) and energy storage system (ESS) markets, the demand for lithium-ion batteries (LIBs) has skyrocketed, highlighting the importance of securing a sustainable supply of lithium. This study explores chlorination roasting as a method for recovering lithium from Li-containing slag, which is a promising alternative lithium source obtained from pyrometallurgical LIB recycling process. We investigate the efficiency of chlorination roasting in producing technical grade (TG) lithium chloride (LiCl) from the slag and quantitatively analyze the impurity behavior during the process. Different chlorinating agents, including CaCl2, NaCl, and PVC, are evaluated for their effectiveness in lithium recovery and purity. The results indicate that CaCl2 is the most effective in achieving high lithium recovery and LiCl purity, at approximately 90%. This offers a promising solution for sustainable lithium production. This research would highlight the importance of developing efficient recycling methods to meet the growing demand for lithium in EV and ESS applications.

ABSTRACT Presented universal recommendations for the reduction of crud formation, reviewing various aspects affecting the loss of diluent and extractant due to the formation of a third phase (crud), encountered in many hydrometallurgical plants using copper solvent extraction. In this paper introduce the reasons of the crud formation , description of the stable emulsions containing solid particles and choice of technological scheme. An analysis of operations to be considered in the operation of copper solvent extraction plants is presented, due to the deterioration of copper grade below 0.5% in ore and the increase in aluminum content up to 20–25%. Results of use of extraction properties of modified extractants of ACCORGA series and unmodified extractant Lix984N on pregnant leached solution of the most important deposits (Almaly and Aktogay) are given. It is established that for solutions of Almaly deposit, ACCORGA5640 and unmodified Lix984 extractants have high selectivity to copper. Distribution of iron, silica, and copper ions during extraction was studied, and it was found that high selectivity to copper/iron and copper/silica is possessed by extractant Lix 984N, ACCORGA5640. It was found that for solutions of the Aktogay deposit, the ratio of interphase suspension in both extractants is the same, and phase separation in experiments with the use of extractant Lix 984N was 10 s shorter with the use of extractant ACCORGA5640. It was found that the addition of ACCORGACR60 reagent in the amount of 5-10 ppm also leads to a decrease in the volume of crud by 13%, for a stronger suppression of crud.

ABSTRACT Organic acid leaching receives less attention than inorganic acids for Li-ion battery recycling process at the industrial scale due to the high consumption rate of the acids as leaching reagents. This paper reports an effective leaching of cobalt (Co) and lithium (Li) from spent battery cathode using low concentration of monosodium glutamate as lixiviants. More than 95% of Co and Li could be dissolved at leaching conditions MSG 0.1 M (18 g/L), pH 5, sodium sulfite 0.5 M as reductant, pulp density 20 g/L, room temperature and leaching time 6 h. Increasing the temperature to 80°C sped up the leaching process, where maximum recovery could be attained within 1 h. pH played a major role in the leaching efficiency (effective range pH 4–6). pH lower than 4 led to neutral and cationic glutamate species, which were ineffective in attracting cobalt ion. pH higher than 6 initiated the surface passivation by Co(OH)2. In the absence of a passivation layer, cobalt dissolution mechanism followed the chemical reaction-controlled model, while in the presence of the layer, the mechanism switched to diffusion through product layer. Kinetic studies demonstrated that aside from pH, the formation of passivation layer was hypothetically regulated by adjusting the other leaching parameters. Aside from the observation on kinetic study, the proposed leaching mechanism was supported by characterization (particle size analysis, SEM-EDS, FT-IR) results.

ABSTRACT In general, separating osmium and ruthenium metals via hydrometallurgical methods poses significant challenges. This study presents a novel approach to separate osmium from a metallic mixture with ruthenium through selective dissolution using a two phase system. The system comprises an aqueous phase containing sulfuric acid solution with sodium chlorate and an organic phase consisting of pure tributyl phosphate. Among the several variables investigated in this work, sulfuric acid concentration and stirring speed showed most significant effect on the dissolution of osmium metal. Based on the potential-pH diagram of osmium metal, an oxidation reaction of osmium metal by the sulfuric acid and sodium chlorate mixture was proposed. The role of tributyl phosphate was to prevent the evaporation of the dissolved osmium tetroxide species by extracting into organic phase. The separation of the two metals was accomplished by selective dissolution of osmium at the following conditions: 3 M sulfuric acid, 0.7 M sodium chlorate, pure tributyl phosphate, pulp density of 2 g/L, 20°C, 60 minutes and stirring speed of 200 rpm. Use of a mixture of thiourea and hydrochloric acid solution containing ascorbic acid completely stripped the osmium from the loaded tributyl phosphate. Comparison of dissolution efficiency of osmium metal between two phase system and one phase system of sulfuric acid-sodium chlorate-water indicated that the employment of tributyl phosphate in two phase system was of importance in the recovery of the dissolved osmium species. Our results demonstrated that osmium can be separated from ruthenium by selective dissolution with the two phase system.