Facilitating the Critical Mineral Future: Valorization of Kaolin Mining Waste through Partnerships

<p>In Morocco, no measures have been taken to manage residual waste from operational or abandoned mining and quarries sites.</p><p>Indeed, significant quantities of mine waste, composed of concentrator residues and sterile waste, have been abandoned after the closure of operations without any effective management or rehabilitation planning.</p><p>These residues could have harmful impacts on the environment: soil and water pollution, destruction or disturbance of natural habitats, visual impact on the countryside...</p><p>The valorization and sustainable management of mining waste appear to be adequate solutions to major environmental problems. The construction sector can be a profitable sector to absorb chemically stable mining waste.</p><p>The objective of this research work is to study the feasibility of recycling waste from the abandoned Kettara mine (Morocco) and gypsum waste rock in Sidi Tijji (Morocco) as raw materials in construction materials.</p><p>The study consists first of a geological characterization and then a characterization of the physical, chemical and mineralogical properties of the residues, followed by an evaluation of the mechanical properties of the composite mixtures based on the chemically stable residues.</p><p>The Kettara mine is located in the Jbilet Central Mountains, 30 km northwest of Marrakech. Geologically, the pyrrhotite district of Kettara corresponds to the outcrop area of the volcano-sedimentary series of Saghlef shales. For the gypsum quarry at Sidi Tijji, which is part of the Safi basin, characterized by Jurassic outcrops essentially formed by gypsum and carbonate formations.</p><p>Mineralogical and chemical analysis have shown that these waste products are still rich in minerals such as the waste from the Kettara mine; the FeO3 concentrated amounts to 55.6%. In addition, gypsum waste rock represents a concentration of 28.9% CaO. Therefore, a low water content for the majority of samples.</p><p>Adapting to the principles of integrated recovery and management of mining and quarry waste requires a cultural change within the industry, but also in the ministries concerned.</p><p><strong>Keywords</strong>: Valorization, mine waste, mines and quarries, construction materials.</p>

Mine waste can create long-term and occasionally catastrophic environmental degradation. Due diligence of mine waste in the form of monitoring and maintenance requires a constant supply of societal resources. Furthermore, mine waste is unlikely to disappear with current mining methods and instead, it is more likely to accumulate at a faster rate due to decreasing primary ore grades and increasing societal demands. However, mine waste can be a societal asset, as it can offer an alternative source of partly critical raw materials (CRMs) that can augment primary sources and provide an opportunity to mitigate supply-risk while ensuring sustainability and easing geopolitical tensions. Cobalt is a critical raw material that is largely a by-product of mining of copper, nickel and platinum-group element ores. It is an element that the renewable energy and high-tech sectors critically depend on and for which no reasonable substitutes currently exist. The majority of the global cobalt production stems from the Central African Copperbelt. Published cobalt production figures for the Central African Copperbelt were used to evaluate cobalt tailings from the Central African Copperbelt. As part of a waste valorisation framework that focuses on primarily on the technical aspects of mine waste valorisation, this study assesses the application of key geostatistical methods, such as kriging and conditional simulation, followed by uniform conditioning, to evaluate the resource potential in a hypothetical copper-cobalt tailing deposit from the Central African Copperbelt. The results indicate that methods such as traditional algorithmic kriging, sequential Gaussian simulation and uniform conditioning are highly effective tools in resource modelling of mine waste. The resource assessment framework component developed in this study makes it possible to systematically characterise, profile and model any mine waste storage facility and thus supplements other framework components discussed in an accompanying paper to maximise mine waste utilization.

The quest for steady primary supplies of critical raw materials (CRMs) creates significant waste, which is inevitably generated at each phase of mining and mineral processing. Waste from extraction, separation and refinement of non-renewable natural resources is accumulated globally and creates not only environmental hazards but also economic possibilities. Mine waste management is an expensive and prolonged task but unavoidable. Mine tailings, especially historical ones, can contain economically feasible resources, and given the right condition, such tailings could be reutilised through a waste valorisation concept. A prominent example are the Witwatersrand gold mine tailings in South Africa, which have been reused in small-scale projects. Tailing reutilisation is only possible if a sound classification, sampling and resource modelling framework is established to thoroughly and accurately profile the economic, environmental, health and geometallurgical aspects. Our study on valorisation of mine waste is presented in two parts: Here, in Part I, we focus on the essential components of a mine waste valorisation framework that includes the characterization and development of a systematic sampling framework for consolidated mineralised tailings. The development of a mine waste valorisation framework will hopefully enable worldwide reduction and reutilisation of mine waste.

There are various existing practices and future potential for turning mining waste into valuable products. The inventory of the tailings in the metal mines in Finland showed that considerable concentrations of many critical metals are contained in the waste. However, the amounts of generated waste are so significant that the full implementation of circular economy is challenging. A combination of several different circular economy approaches (reduce, reprocess, upcycle, downcycle and dispose for future) is needed to manage the waste streams in mining in a holistic way. Various technologies are already in use for the recovery of metals from the tailings and for the use of the mineral residues in high and low-value products. The institutional framework has an impact on the economics of the valorisation of mine waste. Digitalisation can support in identifying where the biggest potential for valorisation exists. The rising concepts of digital material and product passports would support the circularity and the traceability of waste-based materials. • Finnish tailings contain considerable amounts of metals. • Holistic circular economy approaches are needed to manage the waste streams. • Technologies to recover metals and to use mineral residues are available. • Valorisation of mine waste depends on the institutional framework. • Digitalisation can support circularity of waste-based materials.

<p>Various industrial residues that are either landfilled or currently have a low recycling rate could represent important secondary mineral resource potential for the construction sector. An ever-increasing construction sector causes increased demand for cement-based materials and consequently implies in increase of CO<sub>2</sub> emission. Belite-sulfoaluminate cements are potentially an alternative cementitious binder to ordinary Portland cements, due to the lower embodied energy and reduced CO<sub>2</sub> emissions compared to OPC clinkers. Its production also allows the substitution of natural raw materials with secondary ones. In the frame of RIS-ALiCE project, funded by the EIT RawMaterials, various industrial and mine residues in Eastern-Southeastern Europe are being mapped. In addition, as a matchmaking tool between the waste holders/producers and potential end-users the registry of secondary mineral raw materials has been developed. In this study, mine and quarry residues have been valorised in order to evaluate their suitability for production of innovative and sustainable low CO<sub>2</sub>-mineral binders. Residues from three mine sites (mine spoils from two Pb-Zn mines from Slovenia and Serbia and brown coal open pit mine from Slovenia) and two quarry sites (limestone quarries from Slovenia) were considered. Samples were characterized with respect to their chemical, mineralogical, physical and radiological properties. Furhermore, to assess the usability of particular residue in cement production, cement clinkers with belite, calcium sulfoaluminate and ferrite as main phases were synthesised, incorporating certain amounts of mine and quarry waste replacing primary raw materials. Main and trace elements as well as REE of residues were determined by X-ray fluorescence spectroscopy and ICP optical emission spectrophotometry. Mineralogical composition of residues as well as sythesised clinkers was determined by X-ray powder difraction and Rietveled method. Content of radionuclides (<sup>40</sup>K, <sup>226</sup>Ra, and <sup>232</sup>Th) was determined by gamma spectroscopy. Depending on the chemical composition of the residues, lower or higher amounts were allowed to be incorporated in the raw mixture for clinker production with targeted phase composition. Potential barriers in the cement production and environmental impact are also discussed. Developed registry with the data valuable for both, waste providers as waste users in Eastern-Southeastern Europe region, can be later-on upscaled also to other regions of Europe. It will provide the data on the available and appropriate secondary resources for cement production which will contrbute to the implementation of sustainable management of raw materials and circular economy.</p><p><strong>Keywords:</strong> mine waste, quarry waste, cement, valorisation.</p>

Sustainable conversion of Brazilian Amazon kaolin mining waste to zinc-based Linde Type A zeolites with antibacterial activity

There is growing global interest in maximising the re‐use and recycling of waste, to minimise the environmental impacts associated with waste treatment and disposal. Use of high‐volume wastes in the production of blended or novel cements (including alkali‐activated cements) is well known as a key pathway by which these wastes can be re‐used. This paper presents a critical overview of the urban, agricultural, mining and industrial wastes that have been identified as potential precursors for the production of alkali‐activated cement materials, or that can be effectively stabilised/solidified via alkali activation, to assure their safe disposal. The central aim of this review is to elucidate the potential advantages and pitfalls associated with the application of alkali‐activation technology to a wide variety of wastes that have been claimed to be suitable for the production of construction materials. A brief overview of the generation and characteristics of each waste is reported, accompanied by identification of opportunities for the use of alkali‐activation technology for their valorisation and/or management. © 2016 Society of Chemical Industry

Lightweight aggregates are extensively used in construction and other industrial applications due to their technological characteristics. The extraction of natural aggregates results in serious environmental effects. Thus, within the circular economy concept, the valorization of waste through the optimization of materials and product design is encouraged. In this work, glass lightweight aggregates were prepared from mixtures of white glass cullet and carbonate wastes from mining (wastes originating from the extraction, manufacture and marketing of magnesite and its derivatives) and the food industry (eggshell and mussel shell). The effects of different processing parameters, such as the particle size of the base glass, percentage of the blowing additive, shaping method, heating rate, temperature and processing time, were evaluated. The results indicate that the mineralogical composition of the blowing agent and the particle size of the base glass are the two processing parameters with the greatest impact on expansion efficiency. Thus, glass artificial aggregates were obtained with characteristics similar to those of commercial products (density values ranged between 0.3 and 0.8 g/cm3 and mechanical strength between 0.7 and 1.5 MPa) from thermal shock expansion treatments in the temperature range 800–900 °C and with dwell times no longer than 15 min.

Mining waste recovery and valorisation is a major challenge because mining generates very large volumes of waste, and because part of this waste has to be considered a resource for the present and future needs of minerals, provided that the waste characteristics are better known. This applies to both suitability for intended use and environmental safety compliance. Due to mining waste characteristics, its reliable characterisation cannot be efficiently achieved by laboratory methods alone. A review of the main on-site characterisation methods is given, along with an evaluation of their scope and limitations. On-site methods, used as the main approach or as a complement, offer a significant gain in representativity and in time reactivity, resulting in a better cost-effectiveness of recovery evaluation and operation.

Mine wastes based geopolymers: A critical review

The mining and minerals beneficiation industries produce large volumes of waste, the land disposal of which can lead to harmful environmental emissions and a loss of valuable resources. Globally, researchers are developing technologies for recovering valuable minerals and converting mine waste into a resource with market value. However, university-developed technological innovations to long-term environmental problems can be difficult to transfer to the mining industry. This paper focuses on the barriers and enablers to technology transfer in the South African mining industry using the valorization of coal processing waste as a case study. Data and information derived from interviews with relevant experts and published literature were used to gain a better understanding of the landscape of waste valorization technology implementation. Results indicated that financial considerations and demonstration of technical feasibility will be vital in determining the success of technology transfer, as will a changing perception of waste and its value within the sector. Original equipment manufacturers (OEMs) and boutique waste processors were identified as potential commercial partners for further development and commercial implementation of university-developed waste valorization technologies within the mining sector.

The cataloging of over 220 coal mining dumping grounds after hard coal mining was carried out on the area of the Upper Silesian Coal Basin (USCB). Considering the significant content of coal particles in the waste, these object may be perceived as perspective anthropogenic deposits. In order to define the possibilities of recovery, an attempt of linking the quality of coal in the deposit and the in waste material was performed. Another step is the reclamation and use of dumping grounds after completing effective recovery processes. The purpose of the research was the cataloging, mapping and valorization of coal mining waste dumps from Katowicki Holding Węglowy coal mines, for the needs of reclamation and management of examined objects and defining the potential recovery of coal from the dumps. The valorization of the post-mining waste dumps was done with the use of original methodology, considering the problems of: reclamation, management, accessibility of the dumps as well as environmental hazards. T he directions of the technical reclamation (e.g. landscape objects, tabular dumps) and biological reclamation (e.g. forest direction, mixed reclamation (grass and tree reclamation), grass cultivation, lack of reclamation) were defined. Accessibility with regard to open access/closing of the dump area and the roads leading towards the object were evaluated. T he connection of coal quality in the deposits of KHW S.A. and in waste material enabled the definition and evaluation of the potential possibilities of recovery of coal from the post mining dumping grounds.

This review provides an update to the last mini-review with the same title pertaining to recent developments in bioleaching and biooxidation published in 2013 (Brierley and Brierley). In the intervening almost 10 years, microbial processes for sulfide minerals have seen increased acceptance and ongoing but also declining commercial application in copper, gold, nickel and cobalt production. These processes have been applied to heap and tank leaching, nowadays termed biomining, but increasing concerns about the social acceptance of mining has also seen the re-emergence of in situ leaching and quest for broader applicability beyond uranium and copper. Besides metal sulfide oxidation, mineral dissolution via reductive microbial activities has seen experimental application to laterite minerals. And as resources decline or costs for their exploitation rise, mine waste rock and tailings have become more attractive to consider as easily accessible resources. As an advantage, they have already been removed from the ground and in some cases contain ore grades exceeding that of those currently being mined. These factors promote concepts of circular economy and efficient use and valorization of waste materials.Key points• Bioleaching of copper sulfide ore deposits is producing less copper today• Biooxidation of refractory gold ores is producing more gold than in the past• Available data suggest bioleaching and biooxidation processes reduce carbon emissions

The valorization and reusing of mining waste has been widely studied in recent years. Research has demonstrated that there is great potential for reusing mining waste for construction applications. This work experimentally investigated the strength development, pore structure, and microstructure of a binary alkali-activated binder. This is based on tungsten mining waste mud (TMWM) and electric-arc-furnace slag (EAF-Slag) using different proportions of TMWM (10, 20, 30, 40, and 50 vt.%). The precursors were activated using sodium silicate (Na2SiO3) and potassium hydroxide (KOH 8M) as alkaline activator solution with solid:liquid weight ratio = 3. Pastes were used to assess the compressive strength of the blended binder and their microstructure. The reaction products were characterized by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infra-red (FT-IR) spectroscopy, while the porosity and the pores size properties were examined by mercury intrusion porosimetry (MIP). The results show that the partial replacement of TMWM with EAF-Slag exhibited better mechanical properties than the 100TM-AAB. A maximum strength value of 20.1 MPa was obtained in the binary-AAB sample prepared with 50 vt.% TMWM and EAF-Slag. The pastes that contained a higher dosage of EAF-Slag became more compact with lower porosity and finer pore-size distribution. In addition, the results obtained by SEM-EDS confirmed the formation of different types of reaction products in the 100TM-AAB, 100FS-AAB, and the binary-AABs mixtures such as N-A-S-H, C-A-S-H and (N, C)-A-S-H gels frameworks in the system as the major elements detected are Si, Al, Ca, and Na.

Strategies for the valorization of soil waste by geopolymer production: An overview