Extraction and recycling technologies of cobalt from primary and secondary resources:A comprehensive review

Cobalt has excellent electrochemical,magnetic,and heat properties.As a strategic resource,it has been applied in many hightech products.However,the recent rapid growth of the battery industry has substantially depleted cobalt resources,leading to a crisis of cobalt resource supply.The paper examines cobalt ore reserves and distribution,and the recent development and consumption of cobalt resources are summarized as well.In addition,the principles,advantages and disadvantages,and research status of various methods are discussed comprehensively.It can be concluded that the use of diverse sources(Cu-Co ores,Ni-Co ores,zinc plant residues,and waste cobalt products)for cobalt production should be enhanced to meet developmental requirements.Furthermore,in recovery technology,the pyro-hydrometallurgical process employs pyrometallurgy as the pretreatment to modify the phase structure of cobalt minerals,enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt production.Consequently,it represents a promising technology for future cobalt recovery.Lastly,based on the above conclusions,the prospects for cobalt are assessed regarding cobalt ore processing and sustainable cobalt recycling,for which further study should be conducted.

Experimental study on the dispersion behavior of a microemulsion collector and its mechanism for enhancing low-rank coal flotation

As the poor dispersion of oily collectors and the inferior hydrophobicity of the mineral surface, the lowrank coal has an unsatisfactory flotation performance when using traditional collectors. In this paper, an ionic liquid microemulsion was used as a collector to enhance its floatability. Flotation test results demonstrated the microemulsion collector exhibited a superior collecting ability. A satisfactory separation performance of 78.66% combustible material recovery was obtained with the microemulsion collector consumption of 6 kg/t, which was equivalent to the flotation performance of diesel at a dosage of25 kg/t. The dispersion behavior of the microemulsion collector was investigated using the CryogenicTransmission Electron Microscopy. The interaction mechanism of the microemulsion collector on enhancing the low-rank coal flotation was elucidated through the Zeta potential and contact angle measurements, the Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis.The microemulsion collector exhibited superior dispersibility, which was dispersed into positively charged oil droplets with an average size of 160.21 nm in the pulp. Furthermore, the nano-oil droplets could be more efficiently adsorbed on the low-rank coal surface through electrostatic attraction, resulting in the improvement of its hydrophobicity. Thus, the microemulsion collector shows great application potential in improving the flotation performance of low-rank coal.

Insight into the microstructural evolution of anthracite during carbonization-graphitization process from the perspective of materialization

Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstructural evolution of anthracite in the temperature range of 1000–2800 ℃ was systematically investigated to provide a guidance for the microstructural regulation of coal-based carbon materials.The results indicate that the microstructure of anthracite undergoes an important change during carbonization-graphitization process. As the temperature increases, aromatic layers in anthracite gradually transform into disordered graphite microcrystals and further grow into ordered graphite microcrystals, and then ordered graphite microcrystals are laterally linked to form pseudo-graphite phase and eventually transformed into highly ordered graphite-like sheets. In particular, 2000–2200 ℃ is a critical temperature region for the qualitative change of ordered graphite crystallites to pseudo-graphite phase,in which the relevant structural parameters including stacking height, crystallite lateral size and graphitization degree show a rapid increase. Moreover, both aromaticity and graphitization degree have a linear positive correlation with carbonization-graphitization temperature in a specific temperature range.Besides, after initial carbonization, some defect structures in anthracite such as aliphatic carbon and oxygen-containing functional groups are released in the form of gaseous low-molecular volatiles along with an increased pore structure, and the intermediates derived from minerals could facilitate the conversion of sp^(3) amorphous carbon to sp^(2) graphitic carbon. This work provides a valuable reference for the rational design of microstructure of coal-based carbon materials.

Ionic liquid catalyzed solvent-free synthesis of chalcone and its derivatives under mild conditions

An ionic liquid(IL)catalyzed solvent-free process was developed for the direct synthesis of chalcone and its derivatives by using substituted acetophenones and benzaldehydes via aldol reaction under mild conditions.A series of acidic and basic ILs were selected and screened.The influences of cations and reaction conditions on product yield and selectivity were systematically investigated.The[Bmim]OH was identified as the optimal IL,with the highest yield and selectivity reaching up to 96.7% and 100%,respectively.A reaction mechanism-based kinetic model was established and regressed with experimental data,revealing the β-Hydroxylketone dehydrolysis with activation barrier of 37.8 kJ·mol^(-1) was observed as the ratecontrolling step.

Advanced silicon nanostructures derived from natural silicate minerals for energy storage and conversion

To effectively alleviate the ever-increasing energy crisis and environmental issues,clean and sustainable energy-related materials as well as the corresponding storage/conversion devices are in urgent demand.Silicon(Si) with the second most elemental abundance on the crust in the form of silicate or silica(SiO_(2)) minerals,is an advanced emerging material showing high performance in energy-related fields(e.g.batteries,photocatalytic hydrogen evolution).For the improved performance in industry-scale applications,Si materials with delicate nanostructures and ideal compositions in a massive production are highly cherished.On account of the reserve,low cost and diverse micro-nanostructures,silicate minerals are proposed as promising raw materials.In the article,crystal structures and the reduction approaches for silicate minerals,as well as recent progress on the as-reduced Si products for clean energy storage/conversion,are presented systematically.Moreover,some cutting-edge fields involving Si materials are discussed,which may offer deep insights into the rational design of advanced Si nanostructures for extended energy-related fields.

Advances in depressants used for pyrite fotation separation from coal/minerals

Pyrite is separated from other minerals mainly by fotation.However,the hydrophilicity of pyrite is afected by many factors,causing it to easily enter the concentrate and consequently reduce the quality of concentrate.Highly efcient pyrite depressants can be selectively adsorbed on the surface of pyrite to improve its hydrophilicity,thereby increasing the fotation separation efciency.Understanding the fundamental inhibition mechanism of depressants on pyrite is a prerequisite to improve the fotation desulfurization efciency.The inhibition ability and mechanism of diferent types of pyrite depressants are reviewed in this manuscript.In recent years,molecular simulation has increasingly become a powerful tool to study the interaction between reagents and minerals,shedding new light on the adsorption mechanisms of reagents on mineral surfaces at the atomic and electronic levels.The properties of sulfde mineral and fotation reagents as well as the microscopic adsorption mechanistic studies of reagents on mineral surfaces based on quantum chemistry and molecular simulation are also reviewed.

Contact angle and stability of interfacial nanobubble supported by gas monolayer

Since solid-liquid interfacial nanobubbles(INBs)were first imaged,their long-term stability and large contact angle have been perplexing scientists.This study aimed to investigate the influence of internal gas density and external gas monolayers on the contact angle and stability of INB using molecular dynamics simulations.First,the contact angle of a water droplet was simulated at different nitrogen densities.The results showed that the contact angle increased sharply with an increase in nitrogen density,which was mainly caused by the decrease in solid-gas interfacial tension.However,when the nitrogen density reached 2.57 nm^(-3),an intervening gas monolayer(GML)was formed between the solid and water.After the formation of GML,the contact angle slightly increased with increasing gas density.The contact angle increased to 180°when the nitrogen density reached 11.38 nm^(-3),indicating that INBs transformed into a gas layer when they were too small.For substrates with different hydrophobicities,the contact angle after the formation of GML was always larger than 140°and it was weakly correlated with substrate hydrophobicity.The increase in contact angle with gas density represents the evolution of contact angle from macro-to nano-bubble,while the formation of GML may correspond to stable INBs.The potential of mean force curves demonstrated that the substrate with GML could attract gas molecules from a longer distance without the existence of a potential barrier compared with the bare substrate,indicating the potential of GML to act as a gas-collecting panel.Further research indicated that GML can function as a channel to transport gas molecules to INBs,which favors stability of INBs.This research may shed new light on the mechanisms underlying abnormal contact angle and long-term stability of INBs.

Structural and electronic properties of bastnaesite and implications for surface reactions in flotation

The structural and electronic properties of bastnaesite were studied by using the first-principles method based on the density functional theory(DFT).The geometry structure of bastnaesite was first optimized,and then the Mulliken populations,electron density and density of states were calculated and further analyzed in detail.The calculation results reveal that it mainly ruptures along the ionic Ce-O and Ce-F bonds during the cleavage of bastnaesite,leaving≡Ce^+,≡F^-and≡CO3^-dangling bonds exposed on the cleavage surface of bastnaesite.Combined with contact angle measurement,surface complexation theory and XPS analysis,the implications of structural and electronic properties on bastnaesite flotation reactions were studied.The hydration of exposed strong ionic bond on cleavage surface results in hydrophilic surface.According to surface complexation theory,the formed surface groups are≡CeOH^0,≡CO3 H^0 and≡FH^0 groups.The investigated metal ions and flotation reagents complex with surface≡CeOH^0 groups,while≡CO3H^0 and≡FH^0 groups are not involved in the complexation.The high activity of Ce atoms facilitates these surface reactions.

Biochar-based slow-release of fertilizers for sustainable agriculture:A mini review

Increasing global population and decreasing arable land pose tremendous pressures to agricultural production.The application of conventional chemical fertilizers improves agricultural production,but causes serious environmental problems and significant economic burdens.Biochar gains increasing interest as a soil amendment.Recently,more and more attentions have been paid to biochar-based slowrelease of fertilizers(SRFs)due to the unique properties of biochar.This review summarizes recent advances in the development,synthesis,application,and tentative mechanism of biochar-based SRFs.The development mainly undergoes three stages:(i)soil amendment using biochar,(ii)interactions between nutrients and biochar,and(iii)biochar-based SRFs.Various methods are proposed to improve the fertilizer efficiency of biochar,majorly including in-situ pyrolysis,co-pyrolysis,impregnation,encapsulation,and granulation.Considering the distinct features of different methods,the integrated methods are promising for fabricating effective biochar-based SRFs.The in-depth understanding of the mechanism of nutrient loading and slow release is discussed based on current knowledge.Additionally,the perspectives and challenges of the potential application of biochar-based SRFs are described.Knowledge surveyed from this review indicates that applying biochar-based SRFs is a viable way of promoting sustainable agriculture.

A review on sustainable reuse applications of Fenton sludge during wastewater treatment

The classical Fenton oxidation process(CFOP)is a versatile and effective application that is generally applied for recalcitrant pollutant removal.However,excess iron sludge production largely restricts its widespread application.Fenton sludge is a hazardous solid waste,which is a complex heterogeneous mixture with Fe(OH)3,organic matter,heavy metals,microorganisms,sediment impurities,and moisture.Although studies have aimed to utilize specific Fenton sludge resources based on their iron-rich characteristics,few reports have fully reviewed the utilization of Fenton sludge.As such,this review details current sustainable Fenton sludge reuse systems that are applied during wastewater treatment.Specifically,coagulant preparation,the reuse of Fenton sludge as an iron source in the Fenton process and as a synthetic heterogeneous catalyst/adsorbent,as well as the application of the Fenton sludge reuse system as a heterogeneous catalyst for resource utilization.This is the first review article to comprehensively summarize the utilization of Fenton sludge.In addition,this review suggests future research ideas to enhance the cost-effectiveness,environmental sustainability,and large-scale feasibility of Fenton sludge applications.