Mineral Recovery Research Articles

Contamination assessment and potential sources of heavy metals and other elements in sediments of a basin impacted by 500years of mining in central Mexico.

Since the middle of the 1500s, mining has been active in central Mexico. Total estimates for low-grade piles and mine tailing materials in the Guanajuato mining district (GMD) are in the range of 150 million tons, covering an area of 15 to 20 km2. GMD is located in the Guanajuato River sub-basin (GRB), which is part of one of the largest basins in Mexico (Lerma-Santiago). Previous studies on the GRB found unusually high concentrations of heavy metals in mining tailings and sediments. Geochemical and statistical methods were used here to determine the sediment's origin, background values, degree of contamination, and toxicity through different contamination indices. This analysis shows that Cu, Co, As, Sb, and Hg are higher than they are in the upper continental crust (UCC) overbank sediments without human and mining influence, because of the ore deposits and rock weathering in GRB. Geochemistry results in stream sediments show anomalies, where Hg, Cu, Zn, As, and Pb are higher than UCC because those heavy metals and trace elements (HMT) have been influenced by human activities and mineral recovery (smelting, amalgamation, cyanidation). The distribution of high concentrations of HMTs and contamination indices occur in the main channel of the Guanajuato River and downstream of the city of Guanajuato. Statistical analyses (cluster and principal component analysis) reveal relationships between Cr, Ni, Cu, and Pb, which are primarily of natural origin, related to rocks of the upper basin. The middle and lower basins are distinctive in their associations between As, Sb, Zn, Pb, and Hg. Additionally, it is recognized that the origins of Pb, Zn, and Hg are geogenic and anthropogenic. This study demonstrates how crucial it is to understand the geochemistry of various HMT sources, with both natural and anthropogenic contributions (stream sediments and rocks), in order to calculate a more realistic background in a basin with both natural anomalies and anthropogenic contamination. The basin is a regional aquifer recharge area, so the new geochemical data are important for improving basin environmental management.

Cationic chitosan graft flocculants: Synthesis, characterization and applications in kaolin separation

Chitosan is a biodegradable, non-toxic and environmental friendly biopolymer. It is a linear polysaccharide which can be tailored for wide range of applications such as, wound healing, drug delivery, mineral recovery, flocculation etc. In this work, cationic flocculants based on the graft co-polymerization of chitosan (Chi) with cationic monomer namely, 3-acrylamidopropyltrimethylammonium chloride (APTMAC) were synthesized. The grafting ratio was varied to get three different compositions of the graft-co-polymers (Chi: APTMAC 1:3, 1:5 and 1:8 wt% in feed) with different MWs and charge, which are the important parameters for efficient flocculation. The chemical structure of the copolymers was confirmed by 1H and 13C NMR spectroscopy. The molecular weight and zeta potential for all the graft copolymers were determined. The charge on the graft polymer increased as the content of the APTMAC increased from 1:3 to 1:8 wt%. The graft copolymers were used for the flocculation of kaolin and the flocculation performance was correlated to molecular weight and charge on the graft copolymers. The optimum dosages were determined and the driving mechanism for the flocculation was discussed in terms of bridging, charge neutralization and electrostatic patch model. The flocs of kaolin were characterized in terms of moisture content and surface properties by optical microscopy. The efficiency of flocculation was found to be very good with low dosages of the flocculants and show great potential in industrial separations.

Development of a geospatial database of tailing storage facilities in Australia using satellite images.

Tailings storage facilities (TSFs) are the main source of pollution from mining operations. However, TSFs are increasingly being considered as the potential secondary sources of some critical minerals. Recovering the critical minerals from TSFs is important due to both environmental and economic implications. Yet, identification of the potential TSFs is the major challenge in this venture due to the lack of publicly available database of TSFs. The objective of this study was to identify the TSFs and document their status in the form of a database for Australia. Visual inspection and interpretation of satellite images in Google Earth were used to identify the TSFs in 6 states and the publicly available database of TSFs for Western Australia (WA) was validated in this study to incorporate into a national-level database. This study has identified 331 active and 759 inactive TSFs in Australia. Among the sites, 42 active and 56 inactive mine sites with TSFs were found within 2km of urban centres in the studied states. Coal and gold were the major commodities of 27% of active mine sites with the TSFs and 38% of inactive mine sites with TSFs, respectively. Approximately 16% of active mine sites with TSFs and 28% of inactive mine sites with TSFs were found to process copper as a major commodity. Considering the companionability matrix, many of these TSFs could be explored for the possible recovery of critical minerals (e.g. rare earth elements, cobalt). This study has developed a national-level database of TSFs for Australia for the first time, and it could be used for a number of applications.

On using excess Gibbs energy as an indicator of hydrophobicity in the flotation process

It has been shown that the partial molar excess Gibbs energy (G̅ex) can be used as an indicator of hydrophobicity and hence contributes to explaining the behaviour of collectors in the recovery of minerals by flotation. This is because hydrophobicity of a mineral particle on which a collector is adsorbed is related to the fact that the alkyl chain associated with the collector behaves in the same way as any hydrocarbon would in a non-ideal mixture with water. Such mixtures are quantified thermodynamically by determining the activity coefficient of the hydrocarbon moiety of the collector and hence its G̅ex in the mixture. The present paper is aimed at extending the above concepts in two different ways. Firstly, an investigation is made of the relationship between G̅ex and contact angle and/or recovery for systems such as ionic liquids and aminothiophenols. Secondly, on the basis of the observation that increases in G̅ex are indicative of increases in the hydrophobicity of the mineral particle-collector aggregate, a study was undertaken to examine, respectively, the effects of the presence of electrolytes or alcohols in the system, of pH and changing concentrations of the collector, on G̅ex of the collector alkyl group and hence its hydrophobicity. In the first instance, the relationship between G̅ex and contact angle and recovery is sustained. With respect to the latter, the absence of any correlation between G̅ex and recoveries supported the proposition that the major effect of electrolytes and added alcohols is rather on particle – bubble attachment. Similarly, it is also indicated that since the change in G̅ex is minimal when collector concentration or pulp temperature is increased these changes do not significantly affect the hydrophobicity of the collector-mineral particle and hence also the recovery in a microflotation.

Enhanced sulfidization flotation mechanism of smithsonite in the synergistic activation system of copper–ammonium species

Copper–ammonium species were introduced in this work to improve the surface sulfidization and flotation performance, and the mechanism was revealed by solution composition determination and surface measurements. Results showed that copper–ammonium species exhibited superior activation performance compared to individual copper ions, and more copper ions were transferred onto the smithsonite surface to increase the mineral surface reactivity with sulfide and xanthate species. Compared with the individual activation system of copper ions, a superior sulfidization of smithsonite was obtained in the synergistic activation system of copper–ammonium species. The activation of smithsonite surfaces with copper–ammonium species not only increased the content of copper sulfide species, but also enhanced the activity of sulfidization products on the surface of smithsonite. Accordingly, a greater amount of xanthate species adsorbed on the surface of smithsonite, and the surface hydrophobicity significantly was enhanced after smithsonite was activated with copper–ammonium species. Compared with treatment in the direct sulfidization system, the flotation recovery of smithsonite increased by approximately 30% under the optimum flotation conditions after treatment in the synergistic activation system of copper–ammonium species. The research results provide a potential technology for promoting the efficient recovery of zinc oxide minerals through sulfidization xanthate flotation.

Valorization of surface-water RO brines via Assisted-Reverse Electrodialysis for minerals recovery: Performance analysis and scale-up perspectives

Reverse osmosis (RO) processes have been recently identified as mostly capable of quantitative removal of salts and contaminants from saline and surface waters, though posing the problem of a concentrated brine to be disposed of and a produced permeate too low in minerals, thus requiring a sometimes expensive remineralization step. In the present paper, Assisted-Reverse Electrodialysis (A-RED) has been proposed for the remineralization of surface-water RO permeate by recovering minerals from its brine. A purposely developed and validated model has been adopted to carry out a parametric analysis for design and optimization of an industrial-scale plant. The techno-economic analysis underlined that full permeate remineralization can be achieved with minimum specific energy consumption of 0.08 kWh m−3, while a minimum remineralization cost of 2.2 c€ m−3 was found applying a permeate by-pass and feed & bleed scheme to (i) increase the plant remineralization capacity and (ii) maintain a stack inlet conductivity above 100–160 μS cm−1 (starting from a permeate ~10 μS cm−1). Compared to current post-treatment techniques, results appear very promising thanks to the reduction of chemicals and total costs as well as environmental concerns related to brine disposal.

Recovery of valuable heavy minerals via gravity and magnetic separation operations from Diit Quaternary stream sediments, southern coast of the Red Sea, Egypt

This research aims to concentrate and recover valuable heavy minerals (VHMs) contained in Diit area, southern coast of the Red Sea, Egypt. In this study, three technological samples were collected representing Lens, Delta and Wadi Diit; mineralogical investigation followed by mineral processing was performed in order to recover VHM content. VHMs such as zircon, ilmenite, rutile, sphene, apatite, garnet, and magnetite have been recorded in associations with lesser amounts of uranothorite, monazite, xenotime, fergusonite, khatyrkite, and gold. Initially, two stage wet gravity concentration processes, rougher and scavenger, were carried out via a shaking table to produce a clean concentrate of VHMs, which was used as feed material for the magnetic separation process. Magnetic separation was performed in order to separate ferromagnetic minerals from paramagnetic minerals as well as diamagnetic minerals to obtain clean concentration of these fractions. Assay and Material balance of the concentration steps proved that the THM content of Diit lens increased to 89.70% with a recovery of 91.68% in a weight of 61.08% out of the original sample. While the percentage of THM content in Wadi and Delta Diit samples increased to 48.68 and 47.67% respectively, with recovery equivalent to 71.67 and 82.06% respectively in a weight of 16.51, 18.7% respectively out of the original sample. Finally, a process flowsheet was created according to the optimum conditions for concentration and separation processes.

An Assessment of the Role of Combined Bulk Micro- and Nano-Bubbles in Quartz Flotation

Bulk micro-nano-bubbles (BMNBs) have been proven to be effective at improving the flotation recovery and kinetics of fine-grained minerals. However, there is currently no research reported on the correlation between the properties of BMNBs and flotation performance. For this purpose, aqueous dispersions with diverse properties were created by altering preparation time (0, 1, 2, 3, 5, and 7 min), aeration rate (0, 0.5, 1, 1.5, and 2 L/min) and aging time (0, 0.5, 1, and >3 min). Micro- and nano-bubbles were characterized using focused beam reflection measurements (FBRM) and nanoparticle tracking analysis (NTA), respectively. The micro-flotation of quartz particles was performed using an XFG-cell in the presence and absence of BMNBs with Cetyltrimethylammonium bromide (CTAB) as a collector. The characterization of bubble sizes showed that the bulk micro-bubble (BMB) and bulk nanobubble (BNB) diameters ranged from 1–10 μm and 50–400 nm, respectively. It was found that the preparation parameters and aging time considerably affected the number of generated bubbles. When BNBs and BMBs coexisted, the recovery of fine quartz particles significantly improved (about 7%), while in the presence of only BNBs the promotion of flotation recovery was not significant (2%). This was mainly related to the aggregate via bridging, which was an advantage for quartz flotation. In comparison, no aggregates were detected when only nano-bubbles were present in the bulk solution.

Mining minerals and critical raw materials from bittern: Understanding metal ions fate in saltwork ponds

Seawater represents a potential resource for raw materials extraction. Although NaCl is the most representative mineral extracted other valuable compounds such as Mg, Li, Sr, Rb and B and elements at trace level (Cs, Co, In, Sc, Ga and Ge) are also contained in this “liquid mine”. Most of them are considered as Critical Raw Materials by the European Union. Solar saltworks, providing concentration factors of up-to 20 to 40, offer a perfect platform for the development of minerals and metal recovery schemes taking benefit of the concentration and purification achieved along the evaporation saltwork ponds.However, the geochemistry of these elements in this environment has not been yet thoroughly evaluated. Their knowledge could enable the deployment of technologies capable to achieve the recovery of valuable minerals. The high ionic strengths expected (0.5–7 mol/kg) and the chemical complexity of the solutions imply that only numerical geochemical codes, as PHREEQC, and the use of Pitzer model to estimate the activity coefficients of the different species in solution can be adopted to provide valuable description of the systems.In the present work, for the first time, PHREEQC Pitzer code database was extended to include the target minor and trace elements using Trapani saltworks (Sicily, Italy) as a case study system. The model was able to predict: i) the purity in halite and the major impurities contained, mainly Ca, Mg and sulphate species; ii) the fate of minor components as B, Sr, Cs, Co, Ge and Ga along the evaporation ponds. The results obtained pose a fundamental step in critical raw materials mining from seawater brine, for process intensification and combination with desalination.

A review of the influence of blast fragmentation on downstream processing of metal ores

Rock fragmentation is one of the most commonly optimized blasting outcomes due to its significant influence on the efficiency of downstream operations. This paper reviews the influence of blast fragmentation on processing of metal ores. Two aspects of rock fragmentation that influence downstream mineral processing operations include the particle size of the run-of-mine ore and the degree of internal microfracturing in the fragments induced by blasting. The main influences identified include productivity of comminution equipment, energy consumption in comminution equipment and mineral recovery. An increase in blasting energy results in higher throughput and energy reduction in comminution circuits. Increase in blasting energy results in energy savings in the overall mining operations. However, when increasing the blasting energy, the environmental and safety impacts must be taken into consideration. Blast-induced microfractures increase the permeability of the fragments, therefore enhancing mineral exposure to leaching reagents and consequently may lead to higher mineral recoveries, particularly in heap and dump leaching operations which employ-one-stage comminution. However, the textural characteristics of the ore also influence the mineral recovery. Further research should focus on establishing the relationship between blast intensity and mineral leaching recovery for metal ores of different textural properties.

Strengthening flotation enrichment of Pb(Ⅱ)-activated scheelite with N-[(3-hydroxyamino)-propoxy]-N-hexyl dithiocarbamate

To improve the flotation recovery of tungsten minerals was of an urgent issue. In this paper, N-[(3-hydroxyamino)-propoxy]-N-hexyl dithiocarbamate (HAHD) was designed as a powerful collector to enrich and separate scheelite particles. In comparison to benzohydroxamic acid (BHA), HAHD dramatically promoted the floatability of the Pb(Ⅱ)-activated scheelite. Meanwhile, HAHD exhibited a competent selectivity for flotation separation of scheelite from calcite. The findings of zeta potential, contact angle, FTIR, UV and XPS deduced that both HAHD’s dithiocarbamate and hydroxamate groups were of the reactive centers to the Pb(Ⅱ)-activated scheelite where the surface HAHD-Pb(Ⅱ) complex was generated. The introduction of the dithiocarbamate group had a limited influence on HAHD’s flotation affinity towards calcite, while strengthened HAHD aggregation on to the Pb(Ⅱ)-activated scheelite surface, the floatability difference between scheelite and calcite significantly increased. Moreover, the “h-shape” adsorption mode and hexyl group of HAHD possessed a stronger hydrophobization towards scheelite than the single-site adsorption and benzene ring of BHA, returning a higher flotation recovery of scheelite particles.

Towards sustainable production of minerals and chemicals through seawater brine treatment using Eutectic freeze crystallization and Electrodialysis with bipolar membranes

European policy encourages the adoption of sustainable systems that promote the efficient use and recovery of minerals and chemicals. In this respect, desalination brines do contain a dramatic amount of valuable minerals and can be valorized through appropriate treatments rather than releasing them into the environment. This paper proposes an innovative brine recovery system for obtaining high purity chemicals through the integration of Eutectic Freeze Crystallization (EFC) and Electrodialysis with Bipolar Membrane (EDBM) technologies. Two separate laboratory-scale experimental campaigns were carried out to validate the potential integration of the two processes. Mirabilite (Na2SO4∙10H2O) has been recovered with a purity of 99.9% using the EFC, and a feed rich in NaCl with low impurities has been further processed in an EDBM unit. EDBM tests with feed solutions simulating EFC effluents have shown that it is possible to produce acidic and basic solutions with high purity (>99%), despite the presence of impurities in the feed. Interestingly, the low EDBM specific consumptions of 0.9–1.1 kWh kg−1NaOH at 100 A m−2 and 1.3–1.6 kWh kg−1NaOH at 300 A m−2 were comparable with and without impurities. In the context of the circular economy strategy promoted by the EU-H2020 Water Mining project, the current study demonstrates that this integrated system effectively minimizes waste, promoting sustainability while providing a potential economic return.

A novel approach for the synthesis of vaterite and calcite from incense sticks ash waste and their potential for remediation of dyes from aqueous solution

The dumping of incense sticks ash due to no known application of it makes it an emerging solid waste. The presence of toxic heavy metals may categorize them as hazardous materials but the presence of high Calcium and silica has drawn the attention of the value-added minerals recovery. Here, calcium oxides were recovered from the ISA, by minimizing the solid waste. Incense sticks ash contains nearly 49–55% which acts as a potential candidate as a raw material for calcium carbonate. The synthesis of CCMPs, from ISA, involves pre-treatment that includes: the extraction of ferrous particles, and the removal of aluminum and silica. The synthesized CCMPs were characterized by sophisticated instruments for detailed information where UV–Vis spectroscopy (UV–Vis), exhibited absorption peaks for calcium carbonate at 210 nm, while dynamic light scattering (DLS) was shown that the average particle size is 1280 nm. Fourier transform infrared (FTIR) and x-ray diffraction (XRD) confirmed the microcrystalline nature of the particles, where FTIR showed bands in the 1800-700 cm−1 range. Both FESEM and TEM revealed the rhombohedral shape of the CCMPs whose size varied from 0.5 μm to 6 μm and purity was 94–96%. Finally, calcium carbonate particles efficiency was analyzed for the remediation of methyl red dye from the aqueous solution and about 48% dye was removed within 1 h only.

A review of flotation and selective separation of pyrrhotite: A perspective from crystal structures

Pyrrhotite is an associated mineral that exists widely in sulfide ore. The presence of pyrrhotite will affect the recovery of platinum group minerals. Therefore, researchers have paid increasing attention to the flotation separation of pyrrhotite. Pyrrhotite superstructures owning different Fe/S ratios results in various crystal structures, corresponding to different physical, chemical and electronic properties, and consequently different flotation behavior. In the present paper, a comprehensive review is conducted to discuss the influence of crystal structures on the natural floatability, mineral-reagent interaction, surface oxidation and flotation electrochemistry of pyrrhotite. The selective flotation process of pyrrhotite from its associated minerals is also reviewed in this paper. It is hoped that this review can summarize the newly published research results combined with some representative results from the past, to provide a theoretical basis for the study of the flotation mechanism of pyrrhotite and provide a new direction for future research on pyrrhotite.

The minerals industry in the era of digital transition: An energy-efficient and environmentally conscious approach

The concept of the 4th industrial revolution is becoming a strategic determinant of sustainability, success and competitiveness in the modern mining sector. The importance of digital transformation in the mining industry has long been debated, hampered in part by the conservative nature of the mining sector. Much of the debate has focused on choosing suitable mining techniques that provide acceptable levels of ore/waste selectivity, the scale of implementation, cost reduction and suitable metallurgical extraction techniques. The purpose of this review is to give an overview of the digital transformation of the minerals and extractive industry with a focus towards energy efficiency and environmental sustainability. We address: (a) geological elements that influence the level of selectivity during mining, and technologies that deal with waste rejection; (b) eco-friendly techniques, such as tunnel-boring machines, or the use of non-explosive techniques that can assist fragmentation of ores, thereby decreasing energy requirements during mineral processing and improving mineral recovery; (c) use of low-water-consumption automated ore-waste sorting systems; (d) selective metal leaching using coarse particle percolation as an alternate method for treating complicated low-grade ores; and (e) assessing new technological boundaries for the mineral sector. A combination of these aforementioned processes will significantly reduce mining waste. Orebody features, mining methods and equipment, desired scales of implementation, alignment with circular strategies, ore extraction efficiency, and socio-economic factors all play a role in the development and implementation of new technologies and techniques.

Effect of residual reagents on chalcopyrite losses at Mount Isa Mines copper operation: Part I – evaluation of mineral recoveries

Mount Isa Mines Copper Operation (MICO), owned by Glencore, is one of the largest copper producers in Australia. The concentrator has a complex circuit, which includes a pre-flotation section designed for early removal of deleterious talc, and other naturally floating gangue including carbonaceous material.The downside of early talc removal is the loss of chalcopyrite to the pre-flotation concentrate. This work investigates the role of residual collector and frother reagents on chalcopyrite losses in the MIM pre-flotation circuit, and the possibility of improving talc recovery whilst keeping chalcopyrite loss to a minimum. In Part I, the flotation response is evaluated as a function of mineral recoveries in order to differentiate talc flotation responses from those of other Methylglyoxal (MgO) containing minerals such as dolomite. This is achieved through the estimation of ore mineral content from elemental assays and a conversion methodology developed from historical mineralogy data.

Effect of residual reagents on chalcopyrite losses at Mount Isa Mines copper Operation: Part II - evaluation of flotation mechanisms

Mount Isa Mines Copper Operation (MICO) is one of the largest copper producers in Australia. The concentrator has a complex circuit, which includes a pre-flotation section designed for early removal of deleterious talc, and other naturally floating gangue including carbonaceous material.The downside of early talc removal is the loss of chalcopyrite to the pre-flotation concentrate. This work investigates the role of residual collector and frother reagents on chalcopyrite losses in the MIM pre-flotation circuit, and the possibility of improving talc recoveries whilst keeping chalcopyrite loss to a minimum. In Part I of this study, it was demonstrated that talc/chalcopyrite selectivity can be improved by removing residual reagents from the MIM process water. In Part II, the mechanisms of chalcopyrite losses are evaluated to explain the results presented in Part 1. This is done through an evaluation of mineral recoveries by true flotation and entrainment. The effect of residual reagents on chalcopyrite surfaces is evaluated using statistical analysis of Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) performed on process stream samples.

Strengthening the flotation recovery of silver using a special ceramic-medium stirred mill

Strengthening the flotation recovery of silver by fine grinding with special ceramic-medium stirred mill (SCSM), steel ball-medium stirred mill (SBSM) and ball mill (BM) were investigated, respectively. Grinding with SCSM exhibited better performance in terms of Ag recovery, which was approximately 2% higher than those obtained by grinding with SBSM and BM. The reduction of iron ions produced during grinding with SCSM was conducive to the recovery of silver minerals. Additionally, it was found that high liberation degree of silver minerals from gangue minerals was achieved by grinding with SCSM, and this is mainly attributable to good flow characteristics of ceramic medium. The liberation degree of silver minerals in the grinding products was as high as 77.33% after using SCSM to grind the ore to 85% passing 74 μm, suggesting that most silver minerals in the ore have been liberated. The Ag content and Ag recovery of the silver concentrates were basically the same in the cases of grinding with SBSM and BM. SCSM showed considerable potential in fine grinding of non-ferrous and noble metal ores.

Study of classification processes of various bulk geomaterials in a hydrodynamic environment using laboratory models of counter-current drum separators

The paper presents the results of studying separation processes of various mineral particles of different density in a hydrodynamic (water) environment in three laboratory models of counter-current drum separators with cylindrical, conical and multifaceted drums. Research results have shown that compared to cylindrical and conical drum separators, the multifaceted separator is most effective in separating and refining in a hydrodynamic environment. The high recovery of heavy minerals in the concentrate proves this fact.

Review: Brine Solution: Current Status, Future Management and Technology Development

Desalination brine is extremely concentrated saline water; it contains various salts, nutrients, heavy metals, organic contaminants, and microbial contaminants. Conventional disposal of desalination brine has negative impacts on natural and marine ecosystems that increase the levels of toxicity and salinity. These issues demand the development of brine management technologies that can lead to zero liquid discharge. Brine management can be productive by adopting economically feasible methodologies, which enables the recovery of valuable resources like freshwater, minerals, and energy. This review focuses on the recent advances in brine management using various membrane/thermal-based technologies and their applicability in water, mineral, and energy recoveries, considering their pros and cons. This review also exemplifies the hybrid processes for metal recovery and zero liquid discharge that may be adopted, so far, as an appropriate futuristic strategy. The data analyzed and outlook presented in this review could definitely contribute to the development of economically achievable future strategies for sustainable brine management.