Mining discharge, namely acid mine drainage (AMD), is a significant environmental issue due to mining activities and site-specific factors. These pose challenges in choosing and executing suitable treatment procedures that are both sustainable and effective. Ceramic membranes, with their durability, long lifespan, and ease of maintenance, are increasingly used in industrial wastewater treatment due to their superior features. This review provides an overview of current remediation techniques for mining effluents, focusing on the use of ceramic membrane technology. It examines pressure-driven ceramic membrane systems like microfiltration, ultrafiltration, and nanofiltration, as well as the potential of vacuum membrane distillation for mine drainage treatment. Research on ceramic membranes in the mining sector is limited due to challenges such as complex effluent composition, low membrane packing density, and poor ion separation efficiency. To assess their effectiveness, this review also considers studies conducted on simulated water. Future research should focus on enhancing capital costs, developing more effective membrane configurations, modifying membrane outer layers, evaluating the long-term stability of the membrane performance, and exploring water recycling during mineral processing.

Mining operations must account for increasingly stringent wastewater discharge limits for various contaminants, such as heavy metals and suspended solids. In the treatment of metal-bearing wastes, electrochemical processes, including electrocoagulation (EC), are gaining popularity. At large scales, EC processes can be hindered by considerable amounts of flocculants and by sedimentation tank sizes required to properly operate. This work sought to address these concerns by evaluating EC in mine water treatment using a pilot system coupled with ceramic membrane microfiltration (MF) and ultrafiltration (UF). The use of MF and UF after EC allows for the removal of suspended solids without needing a flocculation-sedimentation process. EC evaluation was performed using field samples of mine water from a North American concentrator. Under optimal conditions, EC removed over 95 % of Cr, Co, Cu, Fe, Mn, Ni, Pb, Ti and Zn from the mine water. Effluent from EC was used as feed in MF and UF processes with ceramic membranes. The tested membranes rejected 100 % of suspended solids from the EC effluent. Permeate from the membranes was free of solids and possessed turbidities of 0.05-0.15 NTU. Filtrate from the hybrid process satisfied environmental regulations for heavy metal concentrations, offering new opportunities for reuse or discharge. The hybrid process applied in this work can thus be used in mining operations to safely discharge their water, and/or to increase their water recirculation due to environmental concerns and water shortage.

Steam assisted gravity drainage (SAGD) is an energy and water intensive oil recovery technology for in-situ extraction of oil sands bitumen. It is essential to recycle the SAGD produced water (PW) to reduce water consumption and improve the energy efficiency of the process. This work investigated the removal of residual organic matter (ROM) in the SAGD-PW by the ceramic nanofiltration (NF) membrane process. The overall removal efficiency of ROM in the SAGD-PW was influenced by their polarities, membrane pore size, and membrane material. Non-polar oil components including saturated and aromatic hydrocarbons were completely removed; meanwhile, approximately 80% of polar components were removed by the membrane nanofiltration. Membrane nanofiltration significantly altered the chemical composition of the SAGD-PW by removing 95.0–98.3% of total solvent extracted material (TSEM). The chemical fingerprints of the solvent extracted materials in the feed and permeate samples were characterized. The profile of polar components such as naphthenic acids (NAs) in the permeate samples is significantly different from that in the feed samples.

Water chemistry and its impact on mineral processing operations are not well understood and often not adequately monitored. CanmetMINING, as part of its water management research program, has been involved in a project initiated to identify opportunities for improving water recovery, water treatment, and recycling in the mining and mineral processing operations. One of the main objectives of this work is to evaluate and assess water chemistry and identify factors that impact mineral recovery, concentrate grade, and metal extraction efficiencies in order to understand and mitigate negative impacts of water recycling and improve process efficiency. In collaboration with a North American concentrator, CanmetMINING has been involved in assessing the water chemistry in the mill and evaluating water recycling options for select process streams to reduce fresh water intake and maximize recycling. The overall goal of the project is to investigate options for water recycling (increase the thickener overflow recirculation from thickener overflow tank) without affecting nickel and copper metallurgy. The results of the sampling campaigns showed that the water chemistry of the streams was fairly consistent throughout the year with no significant seasonal variations. The laboratory tests illustrated that when higher quantities of thickener overflow from thickener overflow were used, the nickel + copper grade versus nickel recovery curves shifted towards lower values. These observations were observed for the plant water samples obtained in April, June and August 2019.

The extraction of bitumen from oil sands using steam-assisted gravity drainage (SAGD) produces a considerable amount of oily process water that must be recycled. Ceramic membranes are well suited for this task, but membrane fouling remains a significant barrier to their widespread application. Bituminous clays in produced water are heavily charged and interact with the charged surfaces of ceramic membranes in a way that reduces membrane performance. To address this problem, the surfaces of commercially available multi-lumen tubular ceramic membranes were chemically modified using several charge-neutral polyethylene oxide (PEO)-based organosilanes. Membranes with a pore size of 10 nm and selective layers of either gamma-Al2O3 or TiO2 were modified based on protocols previously used on small-scale ceramic membrane disks and challenged with SAGD-produced water. Results indicate that the modification leads to an improvement in membrane performance. Modification of gamma-Al2O3 membranes by a 30% solution of straight-chain PEO-silane increased permeate flux by factors as high as 2.9. Modification of TiO2 membranes also improved permeate flux. Flux recovery factors upon backflushing increased from 1.3 to 1.6. Furthermore, flux values for gamma-Al2O3 membranes ranged between 50 and 150 Lmh and increased over time, while flux values for TiO2 membranes ranged between 220 and 350 Lmh and declined slightly over time. This indicates that gamma-Al2O3 is a stronger adsorbent for bituminous foulants than TiO2, with foulants being adsorbed quickly and subsequently released during filtration and backflushing. Finally, the decline in performance when switching to a SAGD feed, with a higher pH, total organic carbon and alkalinity, was significantly less severe for modified TiO2 membranes compared to unmodified counterparts. Based on these results, surface modification of tubular ceramic membranes with PEO-based silanes was successful in improving the rejection of bituminous foulants from the membrane surface.

Current oil sands extraction technologies expend a significant amount of energy in the treatment and recycling of the oily process waters that are generated during the extraction process. Ceramic membranes are promising candidates for enhancing the energy efficiency of the produced water deoiling process due to their low energy requirements. However, membrane fouling by bituminous solids remains a significant barrier to the widespread acceptance of membranes in this application. As an alternative to chemical membrane cleaning, a steam regeneration technique was applied to ceramic membranes in the filtration of steam-assisted gravity drainage (SAGD) produced water. This technique involved the periodic injection of steam directly into the membrane feed channels, and was applied in conjunction with conventional permeate backflushing. Tubular multilumen ceramic membranes with titania selective layers having pore sizes of 5 or 10 nm were used. Support layers were composed of either alumina or titania. Optimal transmembrane pressure and crossflow velocity settings were found to be 50 psi and 1 m/s over the investigated ranges. Membrane permeate fluxes increased from 50 to 200 Lmh when the steam regeneration method was activated. Flux enhancement was found to depend on the initial duration of filtration without steam injection, which results in significant irreversible fouling. Steam regeneration also improved membrane separation performance, increasing total organic carbon, sulfate and chloride retention by as much as 19%, 17% and 10%, respectively. Steam regeneration is a continuous in-process method that offers the possibility of recycling the oleophilic cake released from the surface of the membrane. The cake can be sent to a flotation unit upstream of the membrane system, allowing bituminous fines to be entrained in the main oil stream. This offers many possibilities for waste minimization, particularly in remote areas where cleaning fluids that are produced when membranes are chemically cleaned would need to be transported and treated off-site.

Industrial oily wastewaters often contain many recalcitrant species, such as dissolved metal ions, salts, bitumen, clays and humics. These species possess surface charges due to acidic, basic and amphoteric groups, thus leading to severe ceramic membrane fouling. To address this problem, ceramic membrane surfaces were chemically modified with highly hydrophilic PEO-based organosilanes. Three different membrane surface layers (ZrO2 TiO2, ZrO2 and TiO2) were modified at varying silane concentrations and reaction times to test their reactivity and stability. All modified membranes maintained hydrophilic behavior, as shown by water contact angles of < 25 degrees and pure water fluxes of 500-600 Lmh. Modified TiO2 membranes exhibited superhydrophilicity with contact angles < 10 degrees. It was found that TiO2 membranes were the most reactive, achieving maximal silane surface coverage at lower concentrations and reaction times, followed by ZrO2 and ZrO2-TiO2 membranes. The silylated TiO2 membrane was also the most thermally stable surface at 130 degrees C and 160 degrees C. Increasing the length of the PEO chain in the silane was also found to increase the thermal stability of the silane surface. TiO2 membranes modified with the higher molecular weight silane maintained 97% of the silane at the membrane surface when exposed to heat at 130 degrees C. In enhancing the suitability of ceramic membranes in challenging applications; titania membranes over zirconia and zirconia-titania should be used and modified with PEO-silanes containing 9-12 repeat units to ensure maximal surface coverage and enhanced thermal stability.

The feasibility of the application of electrodialysis in separation of light and heavy rare earth elements (REE) in synthetic solutions was investigated. The experiments were carried out using single and binary solutions of a light (cerium) and heavy (ytterbium) REE. The effects of electrical voltage, electrical current, and the addition of complexing agent (EDTA) to increase the separation selectivity were investigated. Separation of Ce and Yb was achieved in binary solutions with and without the addition of EDTA. Higher degrees of separation were seen at higher voltages. Ce–Yb separation was more significant in the presence of EDTA. The separation factor of Ce–Yb and Ce–Yb-EDTA were 1.44 and 2.60, respectively.

In light of the technical challenges associated with performance degradation of ceramic membranes applied to the treatment of produced water, a study aimed at characterizing the nature of fouling was conducted.Tubular gamma-alumina multilayered membranes with titania selective layers used for the treatment of two oil sands impacted water feeds were considered. The first, labelled 'oily water', consisted of physically-separated water and bitumen fractions. The second, representative of steam-assisted gravity drainage (SAGD) process water, was mainly an oil-in-water emulsion.Saturation of the selective layer through bitumen entrapment had an irreversible impact on the physical integrity of the membrane after treatment of the oily water. Treatment of the SAGD feed produced fouling characteristics typically expected in crossflow membrane filtration, and surface modifications to optimize separation of the oil droplets from the surface and pore percolation of the water phase should be effective to improve performance. Surface foulant accumulation was strongly controlled by linear defects resulting from solvent evaporation during sol-gel fabrication of the selective layer. A better understanding of the impact of such defects on fouling seems necessary. Finally, partial replacement of titania by crystalline BaSO4 suggested that other types of selective layers should be considered for a feed containing Ba.

The extraction of bitumen using oil extraction and recovery processes such as SAGD (steam assisted gravity drainage) produces oily process waters that must be treated and recycled when possible. Ceramic membranes are well suited for this task. However, ceramic membranes in aqueous media have a pH dependent surface charge. It was hypothesized that these surface charges are responsible for the high fouling of ceramic membranes in treating wastewaters containing bituminous fines. To maintain desirable hydrophilic properties without surface charges, a highly hydrophilic and neutral organosilane was used to modify the surface of ceramic membrane disks. Membranes having pore sizes of 150 kDa, 300 kDa and 0.14 mu m were modified using this organosilane. The ceramic membranes were then used in the filtration of SAGD produced water. Results indicate that the modification was successful in mitigating the irreversible fouling caused by bituminous ultrafines. The permeate flux of the 150 and 300 kDa membranes more than doubled after modification in a 20% silane solution. Furthermore, the filtered water obtained from the modified membranes was of superior quality, to that of the untreated membrane, as evidenced by total organic carbon analysis. All of the ceramic membranes tested were shown to reduce the particle sizes in the produced water from >200 nm in the feed to <40 nm in the permeate.

A bioleaching study was conducted with six nickel sulphide ores from different geographical locations across Canada. Mineralogical and chemical examination revealed considerable variability between the samples, particularly in the silicate phases. The ores contain 0.3-1% nickel, primarily in pentlandite and secondarily in pyrrhotite. Copper is present primarily in chalcopyrite, and cobalt in pentlandite. The ores were subjected to the same crushing and grinding procedure, and bioleached under the same conditions for 3 weeks with a mixed culture of iron- and sulphur-oxidizing bacteria. Stirred-tank experiments with finely ground ore (-147 mu m) at 30 degrees C were conducted to assess the effect of pH (2-5) and the impact of the bacteria. Nickel extraction from pentlandite and pyrrhotite during bioleaching at pH 2 and 3 was generally good (49-86% after 3 weeks), and cobalt extraction tracked nickel extraction over most conditions. All six ores showed a similar response to a change in pH; an increase in pH from 2 to 3 resulted in approximately the same nickel and cobalt extraction (within statistical error), and a statistically significant reduction in sulphuric acid consumption, dissolved iron, and magnesium extraction. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

The focus of this study is to characterize the bacterial community structure present during stirred-tank bioleaching of a low-grade nickel sulphide ore at different temperatures (5 to 45°C) and pH levels (3 and 5). This is a continuation of previous work, which was designed to assess the technical feasibility of applying elevated-pH bioleaching to this same ore from Manitoba, Canada. A combination of classical microbiological and molecular biological techniques has been used to identify and enumerate the members of the bacterial consortia over the course of the five-week experiments. DGGE analysis revealed the presence of at least 16 distinct 16S rRNA gene sequences, 14 of which are closely related to existing GenBank sequences. Two sequences were detected that are not closely related to existing GenBank sequences and may possibly be from novel species. Thirteen sequences are related to gene sequences of genera that have previously been detected in bioleaching environments (Acidithiobacillus, Leptospirillum, Sulfobacillus, Acidiphilium, Ferrimicrobium, and Acidimicrobium). Members from the genus Acidithiobacillus were dominant at all temperatures except 45°C, at which Sulfobacillus spp. were dominant. Many of the acidithiobacilli are most closely related to strains of Acidithiobacillus ferrooxidans, and different strains were dominant under different experimental conditions, indicating considerable phenotypic heterogeneity within the species.

The purpose of the present work is to investigate the technical feasibility of using elevated-pH bioleaching on a low-grade ultramafic nickel sulphide ore from Manitoba, Canada, which is not currently exploitable with conventional technologies. The ore contains 21% magnesium (similar to 35% MgO) and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as lizardite, making processing difficult with conventional pyro- and biohydrometallurgical techniques. This work has two equally important objectives: to minimize magnesium mobilization and to maintain an acceptable level of nickel extraction. Five-week stirred-tank bioleaching experiments were conducted with finely ground ore (-147 mu m) at 30 degrees C to study the effect of pH (2 to 6) on nickel and magnesium extraction. The rate of nickel extraction from pentlandite was found to be relatively insensitive to acidity at low pH and positively correlated to acidity at high pH. During the first three weeks of bioleaching, nickel was extracted at similar rates for experiments conducted at pH <= 5, with over 70% of the nickel extracted in that timeframe. The leaching of magnesium showed a greater dependency on pH. gradually decreasing from 70 to 10% at pH 2 and 5 respectively, after five weeks. Bioleaching at elevated pH substantially increased the ratio of nickel to magnesium in the leachate, and resulted in substantially less sulphuric acid consumption. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

This study is a continuation of previous work designed to assess the effect of elevated-pH bioleaching on a low-grade ultramafic nickel sulphide ore from Manitoba, Canada. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as lizardite, making processing of the ore difficult with conventional pyro- and biohydrometallurgical techniques. This work has two objectives: to maximize nickel extraction, and to minimize magnesium mobilization. Five-week stirred-tank bioleaching experiments were conducted with finely ground ore (-147 mu m) at three pH levels (3,4 and 5) and five temperatures (5,15,22.5, 30, and 45 degrees C). The initial rate of nickel extraction from pentlandite was observed to be inversely correlated to acidity at all temperatures, while the final extraction of nickel after 5 weeks was determined to be moderately correlated to acidity at high temperatures and negatively correlated to acidity at low temperatures. The advantage of elevated-pH bioleaching was most evident at 5 degrees C, in which the final extraction of nickel at pH 5 was approximately 250% greater than at pH 3. Electron probe X-ray microanalysis of the post-leach residues revealed that the un-reacted lizardite was enriched with nickel during experiments conducted at pH 5, and that the extent of enrichment was a strong function of temperature. The undesirable extraction of magnesium exhibited a strong negative pH-temperature interaction and the consumption of sulphuric acid directly tracked the extraction of magnesium over all experimental conditions. Bioleaching at elevated pH substantially increased the ratio of nickel to magnesium in the leachate, and resulted in a substantial reduction in sulphuric acid consumption. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

A process has been developed to remove arsenic from contaminated water and wastewater. The effect of initial and operating pH on the uptake of arsenic by two types of activated alumina was investigated in this work. Arsenic concentrations of less than 50 mu g/L were obtained within ten minutes from solutions with initial arsenic levels of greater than 40 mg/L. Lower residual arsenic concentrations were achieved when a constant pH was maintained throughout the experiments. The optimum pH for arsenic removal was between 2 and 5, with pH 3 resulting in better aresenic removal. The effect of the presence of sulphate on arsenic uptake by alumina was studied. The presence of sulphate at concentrations higher than 100 mg/L significantly inhibited arsenic adsorption.

A series of bench-scale tests was carried out to evaluate two membrane-based processes. The first process was designed to remove heavy metals from soil. It incorporated slurry leaching coupled with membrane filtration. The soil slurry was continuously filtered through a semipermeable membrane. This resulted in a removal of leaching product from the system during its operation and helped maximize the driving force of leaching.The second process was intended to remove heavy metals from aqueous streams. It involved the binding of metals with lignosulfonates followed by ultrafiltration. Ultrafiltration membranes used in the study rejected metals ions bound to lignosulfonate molecules thus removing the metals from water.Both processes appeared to be feasible for the removal of heavy metals from respective contaminated media. Test results are discussed in this paper and recommendations for future work is provided.