Recovery of wolframite from tungsten mine tailings by the combination of shaking table and flotation with a novel “crab” structure sebacoyl hydroxamic acid

Liu W., Peng X., Liu W., Zhang N., Wang X.

In this work, the stable layer structure of serpentine, which seriously restricts the extraction of magnesium, was broken down, and a nearly 94% leaching efficiency of Mg was obtained by adding 5% fluorite powder. Compared with the system without fluorite, the Mg leaching efficiency increased by 36.42%. This result was achieved because the complexation of fluorinion (F − ) with Si in serpentine promoted a distorted tetrahedral orientation, which led to a loose crystal structure of serpentine and contributed to exposing more Mg for a remarkable increase in Mg recovery. It is suggested that fluorite powder could replace expensive assisted reagents in the leaching process, which would markedly decreased the cost. Moreover, an energy-efficient “solvent displacement crystallization” (SDC) method was employed to efficiently recover magnesium (99.04%) from pregnant solutions. At the same time, the reuse of fluorine-containing solutions was explored.

Cao S., Yin W., Yang B., Zhu Z., Sun H., Sheng Q., Chen K.

Temperature affects the flotation of quartz in the calcium/sodium oleate (NaOL) system, while there is a lack of understanding of its potential mechanism. Therefore, in this work, the flotation response of quartz to temperature was investigated via micro-flotation experiments, interface property analyses, and theoretical calculations. Flotation results demonstrated that increasing temperature contributed to higher flotation recovery of quartz, which enhanced the removal of quartz from hematite. Surface tension results revealed that higher temperatures lowered the critical micelle concentration (CMC) and surface tension of the NaOL solution, and thus enhanced its surface activity. Solution chemistry calculations and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the increased content of Ca(OH) + achieved by increasing temperatures enhanced the adsorption amounts of calcium species (acting as activation sites) on the quartz surface. Dynamic light scattering (DLS) measurements verified that the association degree of RCOO − to form (RCOO) 2 2− was strengthened. Furthermore, adsorption density measurements and molecular dynamics (MD) simulations confirmed that increasing the temperature facilitated NaOL adsorption toward the surface of the quartz, which was attributed to the stronger interaction between NaOL and the calcium-activated quartz surface at higher temperatures. As a result, quartz flotation was improved by increasing temperatures. Accordingly, a possible adsorption model was proposed.

Huang Z., Shuai S., Wang H., Liu R., Zhang S., Cheng C., Hu Y., Yu X., He G., Fu W.

Comparison diagram of flotation behavior of lepidolite by new Gemini collector HBDB and traditional monomolecular collector DA. • A novel amine-based Gemini surfactant HBDB was synthesized in our lab. • HBDB was introduced as an efficient collector of lepidolite flotation. • HBDB has better collecting ability and selectivity than traditional collector DA. • Using less dosage HBDB obtained a higher quality lepidolite concentrate. The global lithium supply and demand in this century is accelerated by the energy transition from carbon-based fossil fuels to renewable energy where electrical energy storage and electric vehicles heavily depend on the lithium-ion battery. The lepidolite is one of the main resources for extracting lithium, and it is usually enriched by froth flotation separation technology. However, the traditional lepidolite collector is monomer surfactant with only a single hydrophobic group and hydrophilic group, which usually leads to the low flotation separation efficiency. Therefore, to achieve the flotation separation of lepidolite ore more efficiently, in this work, an amine-based Gemini surfactant, hexanediyl-α, ω-bis (Dimethyldodecylammonium bromide) (HBDB), was synthesized, and compared with the conventional single molecule collector dodecylamine (DA). The experimental results show that the optimum pH value of flotation is 3, and the optimum dosage of HBDB and DA are 150 g/t and 300 g/t respectively. In bench-scale flotation experiments, compared with the conventional monomer DA collector (350 g/t), the Gemini HBDB with only 1/2 dosage of DA (175 g/t) increased the recovery of lepidolite by 16.18%. Economic calculation for a lepidolite ore plant, 1500 t/d, demonstrating that using Gemini HBDB can gain more about $ 8.2 million USD per year than using traditional unimolecular DA. Accordingly, this study provides a new and highly efficient collector for the flotation separation of lepidolite ore.

Jiang H., Zhang Y., Wang C., Wang H.

Polyvinyl chloride (PVC) and polycarbonate (PC) microplastics are major sources of hazardous chlorine and bisphenol A, threatening the ecosystem and environment. Plastic recycling can control the source of microplastics pollution, but the recycling of PVC and PC will be prevented by invalid separation. We established a novel and clean flotation method to separate PVC and PC microplastics by using aluminum coating. Trace amounts of Al(OH) 3 can selectively coat the PVC microplastics surface due to its strong affinity for PVC. The contact angle of PVC decreases by 24° due to abundant hydroxyl groups of Al(OH) 3 coating, whereas PC remained hydrophobic. Response surface methodology (RSM) combining Box-Behnken design (BBD) is used to optimize modification. A quadratic model is established to predict PC purity, explore the interaction between pH, aluminum chloride concentration, and ultrasonic duration. The recovery and purity of microplastics can exceed 99.65% with parameter optimization. The effects of multi-component, brand, shape, size, and mass ratio of plastics are utilized to evaluate the application potential. The suitable situations and limits of this method are disclosed. The aluminum coating offers significant benefits over other modifications in terms of reaction temperature, treatment time, and pollution prevention. Flotation based on aluminum coating provides a new insight for separating and recycling microplastics. • Aluminum coating was applied in the floatation separation of PVC and PC MPs. • Strong interaction between Al(OH) 3 and C–Cl bond led to PVC hydrophilization. • Response surface methodology was used to optimize the modification conditions. • Over 99.65% PVC and PC microplastics can be separated and recovered. • Aluminum coating is a gentler, faster, and cleaner surface modification method.

Zhen Z., Ma X., Ma B.

The seepage accident of a tailings pond poses a serious threat to the stability of tailings dams and the surrounding environment. To reduce the occurrence of seepage accidents, this paper studies the identification of seepage hazards, the propagation law of seepage risk, the importance of hazards, and the priority of hazard treatment. To overcome the subjectivity and omission of hazard identification, according to the complexity and dynamics of tailings seepage, this paper proposes the evidence-based identification method of three-dimensional seepage hazards (EIMTSH) to identify the hazards of the tailings seepage system and the relationship between hazards. Then, on the basis of identifying the hazards of the tailings seepage system, the propagation network of seepage risk in tailing ponds (PNSRTP) is constructed based on the complex network theory. By analyzing the characteristics of the PNSRTP, it can be found that the propagation of seepage risk is scale-free and small-world. Through the node deletion method, this paper finds that the nodes with a higher degree value can reduce the network efficiency more quickly and should be governed first. By giving priority to the treatment of hazards with higher degree, the propagation of seepage risk can be reduced more quickly and the risk management level of tailings ponds can be improved, which is helpful to realize the sustainable development of mining production.

Zou S., Ma X., Wang S., Zhong H., Qin W.

In this study, the flotation of rhodochrosite fines induced by octyl hydroxamic acid (OHA) as hydrophobic agglomerates was investigated through the measurements of micro-flotation, laser diffraction, microscopy observations and zeta potential. The experimental results showed that the apparent particle size and morphology of rhodochrosite agglomerates were greatly affected by OHA concentration and stirring speed. Bigger agglomeration particle size and more regular agglomerates could be obtained at the OHA concentration of 60 mg/L, and appropriate stirring speed was required to form an optimum particle size of agglomerates for micro-flotation. The increased apparent particle size of rhodochrosite was favorable for micro-flotation recovery even though the particles were negatively charged in the presence of OHA. It's considered that OHA adsorbed on the surface of rhodochrosite through zeta potential results as well as the species distribution analysis of OHA and rhodochrosite. • Rhodochrosite agglomeration induced by OHA was investigated. • Agglomerates size was closely related to mechanical agitation. • Correlation of rhodochrosite aggregation with flotability was presented. • OHA could be well adsorbed on the surface of rhodochrosite.

Cui W., Chen J.

Flotation is a complex process that occurs in solid–liquid-gas multiphase systems, and its main factors include the minerals, separation medium, as well as various flotation reagents. The study of mineral properties and interactions with other components such as reagents and water lays the basic theoretical foundation for flotation. Density functional theory (DFT) calculations can qualitatively evaluate the exchange of matter and energy between the mineral system and the surroundings and quantitatively characterize these behaviors, which greatly expands the breadth and depth of flotation studies. This review systematically summarizes the advances of flotation research based on DFT studies, including the study of mineral crystal chemistry represented by the theory of lattice defects, mineral surface hydration such as hydrophilicity and hydrophobicity, surface regulation mechanism, and collecting mechanism based on surface adsorption theory. More significantly, it systematically elaborates different types of collectors according to their characteristics and emphatically explains the mechanism of some typical collectors in detail.

Zhang S., Huang Z., Wang H., Liu R., Cheng C., Shuai S., Hu Y., Guo Z., Yu X., He G., Fu W.

How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing. In this work, a novel amino-based Gemini surfactant butadiyl-1, 4-bis (dimethyl dodecylammonium bromide) (BBDB) was prepared and first utilized as a novel collector for kaolinite flotation. Its flotation performance for kaolinite was compared with that of the common monomolecular surfactant 1-dodecylamine (DDA) by micro-flotation tests. The tests results indicated that 95% kaolinite recovery was obtained using 2.0 × 10 −4 mol/L BBDB at 25 ℃, which was half of the dosage when DDA obtained the maximum kaolinite recovery of 81%. At extremely low temperature (0 ℃), 3.0 × 10 −4 mol/L BBDB could still collect 91% kaolinite, while DDA showed a frustrating ability. The contact angle tests indicated that BBDB could still significantly improve the hydrophobicity of the kaolinite surface (contact angle 71.7°) than DDA (contact angle only 25.8°) at 0 ℃. The Krafft point comparison tests indicated that BBDB had a much lower Krafft point (below 0 ℃) than DDA. Fourier transform infrared spectroscopy (FTIR)-spectrum analysis and zeta potential measurements showed that BBDB was physically adsorbed on the surface of kaolinite through electrostatic interaction.

Liu C., Zhu Y., Huang K., Yang S., Liang Z.

Flotation separation of smithsonite from calcite is difficult due to their similar surface properties. In the present study, a reagent scheme of depressant calcium lignosulphonate (CLS) and collector benzyl hydroxamic acid (BHA) was introduced in the flotation of smithsonite from calcite. Microflotation tests revealed that the efficient flotation of smithsonite from calcite could only be obtained with the addition order of BHA before CLS, which was opposite to the widely-used order that adding depressant prior to the collector. The zeta potential measurements indicated that BHA selectively adsorbed onto smithsonite surface, then not allowed the CLS adsorption onto the smithsonite surface rather than calcite surface because of the steric hindrance, thereby the smithsonite surface remained hydrophobic while calcite surface became more hydrophilic after the addition of CLS. As a result, the calcite flotation was completely depressed while the smithsonite flotation recovery was still in high value, leading to the optimal flotation separation performance.

Liu W., Sun W., Liu W., Dai S., Duan H., Zhou S., Qiu J.

• AESNa separates magnesite from dolomite via flotation for the first time. • EO groups improve the ion tolerance and solubility of AESNa. • The selectivity of AESNa is improved due to ion tolerance. • The effect of Ca ions on selectivity changed from negative to positive. The separation of magnesite and dolomite has always been a difficult problem in flotation production, one of the reasons is that the dissolved Ca 2+ ions from dolomite weaken the anionic flotation selectivity. In this study, an ion-tolerance collector, sodium fatty alcohol polyoxyethylene ether sulfonate (AESNa), was used to weaken or eliminate the adverse effects of Ca 2+ . Micro-flotation tests, surface tension tests, Fourier transform infrared spectroscopy (FTIR) tests, X-ray photoelectron spectroscopy (XPS) tests, and density functional theory (DFT) calculations were carried out. The micro-flotation results showed that AESNa had a better collecting ability and selectivity under alkaline conditions, and the addition of Ca 2+ selectively inhibited approximately 15% recovery of dolomite. Additionally, AESNa successfully separated magnesite from dolomite in the presence of Ca 2+ and water glass (Na 2 SiO 3 ) for the first time. The mechanism analysis indicated that AESNa had a high surface activity and was chemically adsorbed on the mineral surface. The EO groups in AESNa complexed with Ca 2+ by electrostatic interactions and made it difficult for Ca 2+ to invade polar head groups, resulting in the flotation of magnesite not being affected. Additionally, the interaction between the sulfonic groups and CaOH + was weak and led to inhibition of the adsorption of AESNa on the surface of dolomite by a large amount of CaOH + . Therefore, AESNa can promise a wide range of application prospects in flotation production, and the ion tolerance of the collector becomes a key factor in improving the flotation selectivity of soluble minerals.

Liu N., Li B., He Z., Dai L., Wang H., Wang L.

This article mainly reviews the energy storage mechanisms and research progress of vanadium-based and manganese-based cathode materials in aqueous ZIBs. The growing demand for energy storage has inspired researchers’ exploration of advanced batteries. Aqueous zinc ion batteries (ZIBs) are promising secondary chemical battery system that can be selected and pursued. Rechargeable ZIBs possess merits of high security, low cost, environmental friendliness, and competitive performance, and they are received a lot of attention. However, the development of suitable zinc ion intercalation-type cathode materials is still a big challenge, resulting in failing to meet the commercial needs of ZIBs. Both vanadium-based and manganese-based compounds are representative of the most advanced and most widely used rechargeable ZIBs electrodes. The valence state of vanadium is +2 ~ +5, which can realize multi-electron transfer in the redox reaction and has a high specific capacity. Most of the manganese-based compounds have tunnel structure or three-dimensional space frame, with enough space to accommodate zinc ions. In order to understand the energy storage mechanism and electrochemical performance of these two materials, a specialized review focusing on state-of-the-art developments is needed. This review offers access for researchers to keep abreast of the research progress of cathode materials for ZIBs. The latest advanced researches in vanadium-based and manganese-based cathode materials applied in aqueous ZIBs are highlighted. This article will provide useful guidance for future studies on cathode materials and aqueous ZIBs.

Jiang Y., Cheng G., Li Y., He Z., Zhu J., Meng W., Dai L., Wang L.

The application of metal oxide is limited due to low conductivity, weak combination, poor dispersion, and hard nanocrystallization in vanadium redox flow battery. Herein, metal–organic framework (MOF) was firstly employed to prepare metal oxide and porous carbon nanocomposite, which was used to ultra-uniformly decorate graphite felt by in-situ growth. Graphite felt was modified with UiO-66 (Zr-MOF) nanoparticle using hydrothermal synthesis followed by conversion into porous nanocomposite (ZrO2@C) via high-temperature carbonization. ZrO2@C owns large surface area, regular arrangement of ZrO2, and high conductivity, which provides large reaction place, high active site density, and rapid electron transfer for redox reaction. Therefore, ZrO2@C can boost the electrochemical performance of graphite felt for VO2+/VO2+ and V3+/V2+ reactions by promoting diffusion, charge transfer, and electron transport, systematically. The modified flow cell using ZrO2@C/GF has better stability and higher utilization of electrolyte than pristine cell during 500-cycle test. ZrO2@C/GF decreases electrochemical polarization of cell at different current densities. At 200 mA cm−2, voltage efficiency (77.5%) and energy efficiency (75.2%) of modified cell increase by 14.6% and 13.9% respectively compared with pristine cell. The modified cell can operate at a high current density up to 300 mA cm−2 and shows a 62.4% of energy efficiency. The cell performance in this study is superior to that reported in previous metal oxide-related works. This work presents a design allowing MOF-derived catalyst with nano size, high conductivity, good adhesion, and uniform dispersion, simultaneously.

Lu Y., Wang S., Zhong H.

• A hydroxamic acid derivative (NPOHA) was synthesized and first introduced as wolframite collector. • The chemical reactivity and surface activity of NPOHA were stronger than BHA and OHA. • NPOHA could efficiently separate wolframite from fluorite and quartz, with no activator or frother applied. • NPOHA chemisorbed onto wolframite surfaces by bonding two oxygen atoms of CONOH group with Fe atom. Wolframite, as the main mineral for extracting tungsten, is usually separated and enriched by flotation in mineral processing, thus the construction of efficient flotation collector is of great concern to the effective utilization of tungsten resources. In this study, by introducing a phenyl group into octyl hydroxamic acid (OHA) structure, we design and synthesize a hydroxamic acid derivative N-substituted phenyl octyl hydroxamic acid (NPOHA), and report its first employment as a collector in wolframite flotation. Density functional theory (DFT) calculations and surface activity characterization revealed that compared to OHA and benzohydroxamic acid (BHA), NPOHA possessed not only superior electron-donating ability and chemical reactivity, but also stronger hydrophobicity, which contributed to its application in wolframite flotation. Micro-flotation tests proved that NPOHA possessed much stronger collecting ability to wolframite than BHA and OHA, with superb flotation selectivity against quartz and fluorite, which was regarded as an appropriate collector for wolframite flotation. Zeta potential, Fourier Transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements indicated that NPOHA chemisorbed onto wolframite surfaces through the formation of N-O-Fe and C-O-Fe bonds, which was further verified and explained by binding ability evaluations.

Sun Q., Ma X., Lu Y., Wang S., Zhong H.

Both thioether and hydroxamate groups are excellent iron ligands. Herein, to improve the properties of hydroxamic acid and the recovery of tungsten-minerals, a surfactant containing thioether and hydroxamate groups, 2-(benzylthio)-acetohydroxamic acid (BTHA), was introduced to separate wolframite from fluorite. The properties, predicted by Density Functional Theory (DFT) calculations and Molecular Dynamics (MD), indicated that BTHA, as a multifunctional surfactant (i.e., thioether and hydroxamate groups), could enhance its hydrophobicity and selectively adsorb on the desired mineral surfaces. The experimental results of micro-flotation and contact angles confirmed BTHA had a strong collecting ability and good selectivity toward wolframite versus fluorite. The adsorption mechanism, surveyed through zeta potential, solution chemical analysis and XPS, demonstrated only electrostatic adsorption on fluorite surfaces, while chemisorption and hydrogen bonding would be produced on wolframite surfaces. The thioether and hydroxamate groups could co-absorb onto wolframite's surfaces to form Fe S bonds and five-membered hydroxamate-(O, O)-Fe rings.

Liu C., Zheng Y., Yang S., Fu W., Chen X.

Lizardite is representative of a group of serpentine minerals that coexists with nickel sulfide minerals, and the lizardite slime coating that easily forms on surfaces during mineral processing, making it difficult for beneficiation. In this study, a biodegradable polyepoxysuccinic acid (PESA) was introduced as a novel depressant to eliminate the adverse effects of lizardite slimes on pentlandite flotation. The results of microflotation tests and adsorption measurements showed that PESA addition considerably increased the separation efficiency of pentlandite from lizardite slimes, which could be attributed to the improvement of collector adsorption density on the pentlandite surface. Zeta potential measurements and DLVO calculations showed that the lizardite surface charge changed from positive to negative in the presence of PESA, and the resulting electrostatic repulsion caused hetero-dispersion between pentlandite and lizardite particles. Consequently, a collector could adsorb onto the exposed pentlandite surface, restoring the floatability of pentlandite. X-ray photoelectron spectroscopy (XPS) analysis was used to characterize the chemical interactions between PESA and the Mg sites on the lizardite surface. These results demonstrate that PESA can be used as an effective depressant for removing lizardite slimes from the pentlandite surface in a flotation system.

Jiang Z., He G., Jiang Y., Zhao H., Duan Y., Yuan G., Fu H.

Hu Y.

Yang Y., Li B., Che L., Li M., Liu P., Li T., Luo Y.

Cheng C., Wu J., Huang Z.

In this study, a novel collector, N1,N10-dihydroxydecanediamide (DHH) was synthesized in our lab and introduced in flotation of malachite ore. The separation performance and action mechanism of DHH were explored and compared with octyl hydroxamic acid (OHA). The results of single mineral flotation tests indicated that DHH exhibited a stronger collecting ability to malachite and better selectivity against quartz and calcite than OHA, and floated out 94 % malachite, 8.5 % quartz and 17 % calcite at pH = 10 with a collector concentration of 60 mg/L. The FTIR spectra, zeta-potential tests and XPS tests proved that DHH could absorb onto malachite surface though a chemical mode. DFT calculation results showed that DHH anion owned a stronger affinity to malachite than DHH molecular and OHA anion/molecular, and its bis-minerophilic groups could form C(=O)NHO-Cu bond with surface Cu atom. It exhibited that DHH was an excellent candidate and capable for high efficiency flotation of malachite ore.

Msumange D.A., Msumange J.A., Bru K., Bourgeois F.

This paper aims to provide an overview of tungsten (W) tailings properties, detrimental impacts of these tailings, approaches to mitigate these impacts, and a presentation of methods to reprocess them to capture their economic value. Since W is widely used in a variety of industries, it has been extensively mined since the 19th century, and the mining continues to generate significant volumes of tailings. Recent data show that global W production stands at 84 kt per year, and more than 100 Mt of W tailings exist containing over 100 kt of WO3. The tailings contain variable amounts of valuable products and deleterious environmental substances. Some of the contained metals are in great demand for the energy transition. However, these tailings usually contain FeS2/Pyrrhotite and FeAsS minerals, which, when exposed to air and water, can produce acid mine drainage. As such, W tailings may pose environmental and human health risks. Globally, the reprocessing of W tailings presents a potential resource that can be regarded as a paradigm of sustainability and circular economy. Flotation, enhanced gravity separation, and wet high-intensity magnetic separation have been reported to be the common approaches to reprocessing W tailings. However, W processing presents particular difficulties owing to complex material properties, such as fine particle size, surface weathering, similarity in surface properties exhibited by gangue materials (fluorite, apatite, calcite), low concentrations of the elements of interest, and poor mineral liberation.

Das S.K., Nagesh C.H., Sreenivas T., Kundu T., Angadi S.I.

Tungsten is considered one of the important strategic metals due to its specific use in defense applications and high supply risk associated with it. Scheelite (CaWO4) and wolframite ((Fe, Mn)WO4) are the primary minerals mined for the commercial exploration of tungsten. The present review article summarizes the research investigations on geological occurrences connecting to different beneficiation techniques such as gravity, magnetic, and flotation techniques and subsequent plant practices across the globe. Scheelite is primarily associated with skarns and stratabound deposits, whereas wolframite is found in veins, porphyry, and disseminated deposits. The gravity concentration and magnetic separation techniques are predominantly practiced in wolframite beneficiation, while gravity concentration followed by froth flotation is the key route in the scheelite beneficiation. Several research articles have been published in the recent past on the flotation separation of scheelite from calcite, fluorite, and other calcium-bearing minerals. The separation of these mineral systems is challenging as they exhibit similar surface properties. Thus, the present review article also collates the surface properties and various reagent systems developed towards enhancing the flotation selectivity of scheelite particles. Further, the present communication critically reviews the flotation separation of the wolframite mineral system for the first time.

Jeong D., Kim S., Jeon H.

Xie H., Yao X., Yu X., Mao L., Zeng Y., Wu F., Guo S., He G.

In this paper, the flotation separation of cerussite and quartz under different experimental conditions was studied by using phenylpropenyl hydroxamic acid (PHA) as a collector. The flotation performance of PHA was studied through experiments involving pure minerals and artificial mixed minerals, and the results showed that PHA has good selectivity and collecting ability for cerussite. The adsorption mechanism of the collector on the surface of cerussite was investigated via adsorption capacity experiments, zeta potential tests, FTIR spectroscopy, and XPS analysis. The adsorption capacity results showed that PHA can be well adsorbed on the surface of cerussite. The results of the zeta potential tests showed that PHA has strong chemical adsorption on the cerussite surface. FTIR and XPS analysis showed that PHA may form a Pb–PHA complex on the cerussite surface to improve the floatability of cerussite.

Yang Y., Li B., Li T., Liu P., Zhang B., Che L.

Acid mine drainage (AMD) is a pollutant with strong acidity and high concentration of metals, metalloids, and sulfates caused by industrial activities, which is extremely harmful to the environment. AMD prevention technologies, treatment technologies and resource recovery technologies are all available to manage AMD. The principles, advantages, disadvantages and future development of various AMD processing methods were summarized and analyzed in detail in this paper. On this basis, an innovative approach to economic and environmental sustainability assessment (LCSA) based on life-cycle assessment (LCA) and analytical hierarchy process (AHP) was proposed, and various AMD treatment technologies were comprehensively evaluated. It was found that the inorganic dry cover method and inorganic passivation method were the most sustainable methods among AMD prevention technologies, and the oxygen barrier method and surface passivation method could be considered first when we selected AMD prevention methods. The permeable reaction barrier (PRB) technology was the highest scoring method, and passive and biological treatment technologies had the absolute advantage in AMD treatment. The metal (metalloid) and REEs recovery technologies, AMD and MWW co-processing technology, and semi-metallic mineral recovery technology had the best potential for development in AMD resource recycling. The results can provide some insights for the technicians concerned in the field of AMD governance and provide references for the development of AMD treatment technologies.

Chernoburova O., Chagnes A.

This chapter is dedicated to the conventional and novel methods, techniques, and technologies for the critical raw materials (CRMs) recovery from mining, mineral processing and metallurgical residues, industrial solutions, and acid mine drainage. However, a brief overview of the conventional methods used for CRMs extraction from the primary resources is also given in this chapter as primary resource processing impacts the properties of the generated residues. Subsequently, the emerging methods used for CRMs extraction from different types of residues are reviewed. The emphasis was placed on the current research trends and hydrometallurgical methods. This chapter concludes with the perspectives for improving the technologies and a case study.

Zeng Y., Duan N., Fu C., Liao D., Song X., Jin S., Cui K.

Using tailings to prepare constructive materials is of great significance for sustainable development of mineral processing industry. In this study, the possibility of preparing tungsten tailing-based geopolymers was explored in detail. XRD, FTIR, PLM, SEM and XPS analyses were carried out to characterize the phase composition, chemical bonding, microstructure, chemical state, and interface properties of tungsten tailing-based geopolymers. Results showed tungsten tailings presented little activity using NaOH as activator, while geopolymers with 60% non-pretreatment tungsten tailing and 40% metakaolin presented a 3-day compressive strength of 8.4 MPa and 28-day compressive strength of 9.1 MPa. The geopolymerization products of tungsten tailing-based geopolymers were N-A-S-H gels and aluminosilicate zeolite crystals, while tungsten tailings were wrapped by metakaolin-derived geopolymerization phases as aggregates with interfaces containing Si–O–Si bonding between quartz in tungsten tailings and zeolite and/or gel phase in metakaolin-derived geopolymer in the geopolymerization process. Besides, the leaching test results indicated that the immobilization efficiency of T6M4 geopolymers for Mn and Pb derived from tungsten tailings reached up to 97.28% and 99.95%, respectively. This research results provide a new idea for utilization of tungsten tailings on a large scale.

Zhao G., Liu S., Qi J., Yang L., Qiu X., Liu G.

Electron donating ability and hydrophobicity are of the two aspects related to flotation performance of a collector. To solve the insufficient collecting power of benzohydroxamic acid (BHA) in tungsten ores flotation, its derivatives p-alkoxyl benzohydroxamic acids (AOBHAs) were designed as the advanced wolframite collectors. The computational results inferred that compared with BHA, the p-π conjugation between the alkoxyl oxygen and phenyl ring enhanced the electron donating ability of AOBHAs. Meanwhile, AOBHAs exhibited higher hydrophobicity which increased with expanding the carbon chain length of alkoxyl. On this basis, MOBHA (p-methoxy BHA), EOBHA (p-ethoxyl BHA), POBHA (p-propoxyl BHA) and BOBHA (p-butoxyl BHA) were synthesized, and their flotation response towards wolframite was explored through adsorption, zeta(ζ)-potential and contact angle measurements as well as micro-flotation tests. The findings indicated that the adsorption capacities, rangeability of ζ-potential and hydrophobization to wolframite followed the sequence of BOBHA > POBHA > EOBHA > MOBHA > BHA. After pre-activation with 1.0 × 10−4 mol/L lead nitrate, the flotation recovery of wolframite reached about 12.6%, 87.6%, 93.1%, 93.4% and 95.2% for 2.0 × 10−5 mol/L BHA, MOBHA, EOBHA, POBHA and BOBHA, respectively. The experimental findings well supported the molecular design hypothesis.

Han Z., Levett A., Edraki M., Jones M.W., Howard D., Southam G.

Wolframite [(Fe,Mn)WO4] tailings represent a hazardous waste that can pose a threat to the environment, humans, animals and plants. The present study aims to conduct a high-resolution depth profile characterization of wolframite tailings from Wolfram Camp, North Queensland, Australia, to understand the biogeochemical influences on W mobilization. Several indigenous Fe- and S-oxidizing bacteria (e.g., Streptococcus pneumoniae and Thiomonas delicata) in wolframite tailings were found highly associated with W, As, and rare earth elements. Biooxidation of metal sulfides, i.e., pyrite, molybdenite and bismuthinite, produced sulfuric acid, which accelerated the weathering of wolframite, mobilizing tungstate (WO42-). Using synchrotron-based X-ray fluorescence microscopy (XFM) and W L-edge X-ray absorption near-edge spectroscopy (µ-XANES) analysis, wolframite was initially transformed into Na- and Bi- tungstate as well as tungstic acid (partial weathering) followed by the formation of Ga- and Zn- tungstate after extensive weathering, i.e., the wolframite had disappeared. While W (VI) was the major W species in wolframite tailings, minor W(0) and W(II), and trace W(IV) were also detected. The major contaminant in the Wolfram Camp tailings was As. Though wolframite tailings are hazardous waste, the toxicity of W was unclear. Tungsten waste still has industrial value; apart from using them as substitution material for cement and glass production, there is interest in reprocessing W waste for valuable metal recovery. If the environmental benefits are taken into consideration, i.e., preventing the release of toxic metals into surrounding waterways, reprocessing may be economic.

Akbari M., Shafaei Tonkaboni S.Z., Khanchi A.

This study was carried out to develop a beneficiation process flowsheet for the recovery and separation of thorium from Choghart iron mining waste. The characterization and mineralogical studies showed that the mining waste comprised ThO2:2100 ppm, and the main thorium-containing mineral was thorite. The radiometric sorting results indicated the Choghart thorium ore has a medium sortability; furthermore, the thorium cut-off grade and thorium enrichment rate were 100 ppm and 1.2, respectively. The gravity concentration process with a wet shaking table was performed on radiometric sorting concentrate, and the optimum conditions were determined to be 1.5° deck tilt angle, 2 kg/h feed flow rate, and 6 L/min wash water flow rate, according to statistical experimental design. A final product of the wet shaking table was obtained with a ThO2 content of 1.2% and a ThO2 recovery of 90.54% in optimal conditions. The magnetic separation on the heavy and middling fractions of the shaking table in 0.2T led to concentrate production with a ThO2 grade and recovery of 10.5% and 92% and 2.15% and 89%, respectively. Finally, the combination of these separation methods in optimal conditions showed the thorium grade and recovery to be obtained at 3.1% and 74%, respectively.

Ding Z., Liu P., Cui P., Hong C.

In order to build green mines, goaf is often filled, supported, and sealed with a high-water material to eliminate a series of environmental problems and safety hazards caused by goaf. In this study, ordinary Portland cement, sulphoaluminate cement, and alkali-activated cement were used as binders to prepare full-tailings high-water materials for filling, with various water-to-cement ratios. The compressive strength development of consolidated tungsten tailings specimens prepared with various curing binders was observed, and the influence of various water–cement ratios on the strength development was analyzed. The environmental impact of mine backfill materials was assessed according to the life cycle theory (LCA), and these mine backfill materials were prepared by using various binders. The results show that when the water-to-binder ratio is 3, the strength of alkali-activated cement can reach 3 MPa at 28 days; at that ratio, the microstructure of alkali-activated cement is more compact. Through LCA analysis, the environmental load of alkali-activated cement is shown to be significantly lower than that of either Portland cement or sulphoaluminate cement; the LCA results show that the primary energy consumption using alkali-activated cement is reduced from the Portland and sulphoaluminate cements by 1319.32 MJ and 945 kg, respectively. These unusual reduction percentages are achieved because the production of alkali-activated cement by LCA does not have any negative environmental impact—the production of alkali-activated cement, with its primary component being industrial byproduct slag, so that the use of alkali-activated cement in tailings’ consolidation has a positive environmental impact.