X-ray diffraction (XRD) is an important and widely used material characterization technique. With the recent development in material science technology and understanding, various new materials are being developed, which requires upgrading the existing analytical techniques such that emerging intricate problems can be solved. Although XRD is a well-established non-destructive technique, it still requires further improvements in its characterization capabilities, especially when dealing with complex mineral structures. The present review conducts comprehensive discussions on atomic crystal structure, XRD principle, its applications, uncertainty during XRD analysis, and required safety precautions. The future research directions, especially the use of artificial intelligence and machine learning tools, for improving the effectiveness and accuracy of the XRD technique, are discussed for mineral characterization. The topics covered include how XRD patterns can be utilized for a thorough understanding of the crystalline structure, size, and orientation, dislocation density, phase identification, quantification, and transformation, information about lattice parameters, residual stress, and strain, and thermal expansion coefficient of materials. All these important discussions on XRD analysis for mineral characterization are compiled in this comprehensive review, so that it can benefit specialists and engineers in the chemical, mining, iron, metallurgy, and steel industries.

This work explores the mineral carbonation of stainless steel slags in search for a technically and economically feasible treatment solution that steers these waste residues away from costly disposal in landfills and into valuable applications. Argon Oxygen Decarburization (AOD) and Continuous Casting (CC) slags prove ideal for mineral carbonation as their powdery morphology forgoes the need for milling and provides sufficient surface area for high reactivity towards direct aqueous carbonation. Experiments were undertaken using two methodologies: unpressurized thin-film carbonation, and pressurized slurry carbonation. The influence of process parameters (temperature, CO2 partial pressure, time, solids loading) on the slag carbonation conversion are investigated, seeking the optimal conditions that maximize the potential of the slags as carbon sinks. It was found that CC slag carbonates more extensively than AOD slag at essentially every processing condition due to differences in particle microstructure; still, it was possible to reach up to 0.26 and 0.31 g,CO2/g,slag uptake with AOD and CC slags, respectively, at optimal processing conditions via pressurized slurry carbonation. Mineral carbonation conversion was accompanied by significant reduction in basicity, as much as two pH units, and stabilization of heavy metals leaching, meeting regulatory limits (borderline for Cr) for safe waste materials re-use. Via quantitative mineralogical analyses, it was possible to differentiate the carbonation reactivity of several alkaline mineral phases, and to discern the preferential formation of certain Ca- and Mg-carbonates depending on the processing route and operating conditions. Slurry carbonation was found to deliver greater mineral carbonation conversion and optimal treatment homogeneity, which are required for commercial applications. However, thin-film carbonation may be a more feasible route for the utilization of slags solely as carbon sinks, particularly due to the elimination of several processing steps and reduction of energy demand.status: publishe

Scanning electron microscopy (SEM) is a powerful tool in the domains of materials science, mining, and geology owing to its enormous potential to provide unique insight into micro and nanoscale worlds. This comprehensive review discusses the background development of SEM, basic SEM operation, including specimen preparation and image processing, and the fundamental theoretical calculations underlying SEM operation. It provides a foundational understanding for engineers and scientists who have never had a chance to dig in depth into SEM, contributing to their understanding of the workings and development of this robust analytical technique. The present review covers how SEM serves as a crucial tool in mineral characterization, with specific discussion on the workings and research fronts of SEM-EDX, SEM-AM, SEM-MLA, and QEMSCAN. With automation gaining pace in the development of all spheres of technology, understanding the uncertainties in SEM measurements is very important. The constraints in mineral phase identification by EDS spectra and sample preparation are conferred. In the end, future research directions for SEM are analyzed with the possible incorporation of machine learning, deep learning, and artificial intelligence tools to automate the process of mineral identification, quantification, and efficient communication with researchers so that the robustness and objectivity of the analytical process can be improved and the analysis time and involved costs can be reduced. This review also discusses the idea of integrating robotics with SEM to make the equipment portable so that further mineral characterization insight can be gained not only on Earth but also on other terrestrial grounds.

Treatment and disposal of Basic Oxygen Furnace (BOF) slag, a residue of the steel production process characterized by high basicity and propensity for heavy metal leaching, is a costly burden on metallurgical plants; a sustainable valorization route is desired. The stabilization of BOF slag utilizing hot-stage carbonation treatment was investigated; this approach envisions carbonation during the hot-to-cold pathway followed by the material after the molten slag is poured and solidified. Three experimental methodologies were employed: (i) in-situ thermogravimetric analyzer (TGA) carbonation was used to assess carbonation reaction kinetics and thermodynamic equilibrium at high temperatures; (ii) pressurized basket reaction carbonation was used to assess the effects of pressurization, steam addition and slag particle size; and (iii) atmospheric furnace carbonation was used to assess the effect of carbonation on the mineralogy, basicity and heavy metal leaching properties of the slag. Free lime was found to be the primary mineral participating in direct carbonation of BOF slag. Initial carbonation kinetics were comparable at temperatures ranging from 500 to 800 °C, but higher temperatures aided in solid state diffusion of CO2 into the unreacted particle core, thus increasing overall CO2 uptake. The optimum carbonation temperature of both BOF slag and pure lime lies just below the transition temperature between carbonation stability and carbonate decomposition: 830-850 °C and 750-770 °C at 1 atm and 0.2 atm CO2 partial pressures, respectively. Pressurization and steam addition contribute marginally to CO2 uptake. CO2 uptake progressively decreases with increasing particle size, but basicity reduction is similar independent of particle size. The solubility of some heavy metals reduced after carbonation (barium, cobalt and nickel), but vanadium and chromium leaching increased.status: publishe

Mining is an important industry, accounting for 6.9% of global GDP. However, global development promotes accelerated demand, resulting in the accumulation of hazardous waste in land, sea, and air environments. It reached 7 billion tonnes of mine tailings generated yearly worldwide, and 19 billion solid tailings will be accumulated by 2025. Adding to this, the legacy of environmental damage from abandoned mines is worrying; there are around 10,000 abandoned mines in Canada, 50,000 in Australia, and 6000 in South Africa, as well as 9500 coal mines in China, reaching 15,000 by 2050. In this scenario, restoration techniques from mining tailings have become increasingly discussed among scholars due to their potential to offer benefits towards reducing tailing levels, thereby reducing environmental pressure for the correct management and adding value to previously discarded waste. This review paper explores the available literature on the main techniques of mining tailing recycling and reuse and discusses leading technologies, including the benefits and limitations, as well as emerging prospects. The findings of this review serve as a supporting reference for decision makers concerning the related sustainability issues associated with mining, mineral processing, and solid waste management.