Electronic Waste Management by Biological Leaching

Acid mine drainage (AMD) is a persistent environmental challenge resulting from mining activities, characterized by low pH and high concentrations of sulfates and toxic metals. This chapter examines cutting-edge green technologies for treating AMD, with a focus on ecologically benign, economical, and sustainable methods. In addition to new smart technologies like machine learning and AI-driven monitoring systems that allow for real-time treatment optimization and predictive management, it highlights recent developments in the use of bio-based materials, alkaline industrial by-products, constructed wetlands, and advanced membrane systems. In addition to reducing the environmental hazards associated with AMD, these green innovations facilitate resource recovery, such as metal extraction and water reclamation, which supports a circular economy model in the mining industry. Experimental findings reviewed in this chapter reveal that combining bio-sorption and bio-precipitation with membrane or hybrid systems effectively removes 85%–99% of metals and sulfates, while also stabilizing pH and lowering environmental risks. Technologies such as forward osmosis and passive systems like wetlands and magnesite-based treatments offer promising, low-maintenance solutions for AMD, especially in remote areas. A bibliometric study was also carried out to evaluate influential publications, global research trends, and knowledge gaps in AMD treatment. The results showed that over the past 20 years, there has been a growing scientific interest in digital and eco-friendly solutions. This chapter contributes to the discourse on low-carbon, digitally enabled AMD treatment within the broader goals of sustainable and green mining.

Water is an important resource and a necessity for the mining and minerals processing industries. The mining and mineral-based industries extract water from groundwater, streams, rivers, and lakes, for mineral processing, dust suppression, and slurry transport. When the available water in mines is in excess, it can cause flooding in the underground mines; and when it is scarce, it can significantly influence the mining operations. Wastewater generated by the underground and open-cast mines and acid mine drainage produced from the oxidation of metal sulfides, contains higher levels of dissolved aluminium (Al), iron (Fe), and sulfate (SO4). The oxidative dissolution of sulfide minerals releases extremely acidic leachates consisting of toxic elements such as sulfur, arsenic, cadmium, copper, chromium, nickel, lead, uranium, and zinc, which can potentially affect the surrounding environment. The interactions of the elements associated with acid mine drainage is necessary to study for developing proper wastewater management strategy. Studies have shown that the mining activity influences the groundwater and also contaminates water bodies in proximity. In India, water discharge standards/limits containing 33 parameters were framed under the Environment (Protection) Rule, 1986 (under Schedule VI) by the Ministry of Environment, Forest and Climate Change (MOEFCC). Mining wastewater management from surface, underground, and acid mine drainage is therefore one of the most challenging factors in the mining sector. There were several techniques available to treat physiochemical properties of polluted water such as screening, skimming, sedimentation, neutralization, equalisation, oxidation pond, activated sludge process, trickling filters, chlorination, and reverse osmosis. The Total Dissolved Solids (TDS), Total Suspended Solid (TSS), Biological Oxygen Demand (BOD), Dissolved Oxygen (DO), Chemical Oxygen Demand (COD), are the most common parameters that are monitored and treated by the mining companies. In order to meet the present as well as future demands for creating the effective water management strategies, the mining companies need to be increasingly conscious of the risks and opportunities involved in the management of water resources. Although the modern water management systems have better modelling tools, these systems need improvement in their online monitoring tools for data collection, organization, and transfer. To secure quantity as well as quality of water throughout the life cycle of a mine, it is important to make optimum utilization of available resource and ensure its recycling. This chapter provides a critical review of the issues in the management of mine waters and their influence on the health and environment.KeywordsAcid mine drainageGround waterMetal toxicitySurface waterContaminantsRecycling processes

The electronic waste conjointly called e-waste consists of unwanted electronic and electrical waste items. The increasing usage of electrical and electronic goods has arisen in the production of a higher quantity of electronic waste. The management of electronic waste in emerging nations is a challenging problem due to the lack of awareness and improper handling of waste material. Electronic waste management is the challenging problem also in India due to a lack of awareness and poor skills of peoples. In developing nations like Brazil, China, India, etc. major focus lies over monetary gains rather than spending on managing wastage. E-waste accumulation becomes a direct environmental issue that may develop human health hazards. The present study focuses on various constituents existing in e-waste or created throughout processes of use in conjunction with their management and disposal methods.

Acidophilic microbial communities: Candidates for bioremediation of acidic mine effluents

Reductive dissolution of minerals and selective recovery of metals using acidophilic iron- and sulfate-reducing acidophiles

Acid drainage from coal mining: Effect on paddy soil and productivity of rice.

The Iberian Pyrite Belt (IPB), located in the SW of the Iberian Peninsula, is one of the largest polymetallic massive sulfide provinces in the world. Historical mining activity in the area has left a significant legacy of mine residues, including 90 abandoned mines and more than 1.000 ha of waste rock dumps and tailings. Therefore, large volumes of Acid Mine Drainage (AMD) are produced due to oxidation of pyrite-rich residues exposed to atmospheric conditions, which end up in the Tinto and Odiel rivers and subsequently into the ‘‘Ría de Huelva’’ estuary (SW Spain), polluting these water environments. During the passive treatment of AMD with Dispersed Alkaline Substrate (DAS) technology, sequential precipitation of Fe3+ as schwertmannite and Al as basaluminite occurs, and Rare Earth Elements (REE) are preferentially concentrated within the Al-rich precipitate layer. This could be an interesting alternative source of REE, given that AMDs of the IPB are enriched in middle REE (MREE) and heavy REE (HREE). A rough estimation of the REE potential of these AMD sources, based on 40 DAS plants operating in the Odiel basin with variable content of REE, will be the production of 11 kton/year of basaluminite containing 21 ton/year of REE2O3 with grade of 0.19%. However, the origin of REE in AMD is not well understood. This work examines the concentration and pattern of REE in AMD, ore bodies, and country rocks in two representative mining areas of the IPB: Perrunal and Poderosa mines. Leaching experiments were conducted on sulfide ores and host rocks under simulated AMD formation conditions, and the results were compared with the AMD formed in these two mining areas. The preliminary results indicate that the host rocks (felsic and mafic volcanics and shales) are the primary source of REE in the AMD. A mineralogical and chemical study of the country rocks in Perrunal and Poderosa mines reveals that secondary phosphates and carbonates contain the highest REE content, which are also soluble under acidic conditions. REE-rich monazite-type is systematically present in felsic volcanics and shales in both mining areas. HREE-rich xenotime-type is also present in most felsic volcanics, while REE-rich carbonates (mainly parasite-type) are present in carbonate-rich shales from the Perrunal mine. Other minor REE-bearing minerals, such as apatite and zircon, have been identified in the host rocks. However, due to their lower abundance and solubility under acidic conditions, they are not considered an important source of REE in the AMDs of the studied mining areas. Finally, the petrographic evidence shows a selective leaching of these REE-bearing phosphates and carbonates which highly supports their involvement as the main source of REE in AMD.Acknowledgements: This work is part of the I+D+i TRAMPA project (PID2020-119196RB-C21), funded by MCIN/AEI/10.13039/501100011033/.

Biodiversity and ecology of acidophilic microorganisms

Mining activities can generate acid mine drainage (AMD), an acidic discharge that contains elevated sulfate (SO42-), soluble metals, and orange-yellow metal-containing particulates. AMD imposes ecological risks from metal toxicity and physical stress, which may physically spread to nearby water sources or biologically through bioaccumulation. Current methods for AMD treatment, such as chemical or passive biological treatments, are often non-sustainable. Chemical treatments can be expensive and create large amounts of secondary waste, whereas biological treatments like anaerobic wetlands require continuous maintenance through input of organic nutrients. The end goal of this research is to develop a cost-efficient and sustainable floating treatment wetland (FTW) system to remediate AMD-impacted waters from the abandoned Tab-Simco mining site in Southern Illinois. AMD from the site is acidic, having a pH of 2 to 3, with elevated amounts of SO42-, Fe, Al, Mn, Zn and lower amounts of various other metals. Vetiver grass (Chrysopogon zizanioides) is a non-invasive and fast-growing plant that can grow sustainably under hydroponic conditions. Moreover, vetiver is tolerant of acidic conditions and metals, and is a known hyperaccumulator of Pb and Zn. A short-term (30-day), bench-scale experiment revealed that vetiver was tolerant of Tab-Simco AMD and able to improve water quality by increasing pH and reducing the amounts of SO42- and soluble metals. In a follow-up, year-long mesocosm experiment, vetiver plants were positioned on rafts for FTWs and suspended in 378.5-liter containers filled with 170 liters of unfiltered Tab-Simco AMD while additional plants were suspended in AMD that was passed through a plug-filter with recycled materials designed to remove metals and neutralize the water. From the unfiltered AMD, there was high net removal of SO42- (28%), Fe (81%) and Pb (81%) with lower removal of Ni (38%), Zn (35%), Mn (27%), Cr (21%), Al (11%) and Cu (8.0%). From the filtered AMD, there was little to no remaining metals, though there was high net removal of SO42- (45%). Vetiver accumulated Fe > Al > Mn > Zn > Cr > Ni > Cu > Pb. The majority of metals were localized on the root surface as Fe plaques, though Mn and Zn demonstrated greater translocation to the shoots. Moreover, vetiver biomass was deemed non-hazard following metal accumulations through TCLP. An additional year-long microcosm experiment was conducted to ensure complete root coverage by vetiver, which resulted in superior remediation with near complete removal of SO42- (91%) and most metals (90-100%) with the exception

Assessing the sustainability of acid mine drainage (AMD) treatment in South Africa

Chemical and biological leaching is practiced on a commercial scale for the mining of metals from ores. Although bioleaching is an environmentally-friendly alternative to chemical leaching, one of the principal shortcomings is the slow rate of leaching which needs to be addressed. The application of ultrasound in bioleaching, termed sonobioleaching, is a technique which has been reported to increase the rate and extent of metal extraction. This article reviews efforts made in the field of sonobioleaching. Since bioleaching is effectively a biological and chemical process, the effects of sonication on chemical leaching/reactions and biological processes are also reviewed. Although sonication increases metal extraction by increasing the metabolite production and enhanced mixing at a micro scale, research is limited in terms of the microorganisms explored. This paper highlights some shortcomings and limitations of existing techniques, and proposes directions for future research.

The wastes generated from both operational and abandoned coal and metal mining are an environmental concern. These wastes, including acid mine drainage (AMD), are treated to abate the devastating effects they have on the environment before disposal. However, AMD contains valuable resources that can be recovered to subsidize treatment costs. Two of the major constituents of coal AMD are iron and aluminium, which can be recovered and engineered to function as coagulants. This work examines the potential of producing a poly-alumino-ferric sulphate (AMD-PAFS) coagulant from coal acidic drainage solutions. The co-precipitation of iron and aluminium is conducted at pH values of 5.0, 6.0 and 7.0 using sodium hydroxide in order to evaluate the recovery of iron and aluminium as hydroxide precipitates while minimizing the co-precipitation of the other heavy metals. The precipitation at pH 5.0 yields iron and aluminium recovery of 99.9 and 94.7%, respectively. An increase in the pH from 5.0 to 7.0 increases the recovery of aluminium to 99.1%, while the recovery of iron remains the same. The precipitate formed at pH 5.0 is used to produce a coagulant consisting of 89.5% and 10.0% iron and aluminium, respectively. The production of the coagulant is carried out by dissolving the precipitate in 5.0% (w/w) sulphuric acid. Subsequently, the treatment of the brewery wastewater shows that the AMD-PAFS coagulant is as efficient as the conventional poly ferric sulphate (PFS) coagulant. The turbidity removal is 91.9 and 87.8%, while the chemical oxygen demand (COD) removal is 56.0 and 64.0% for AMD-PAFS and PFS coagulants, respectively. The developed process, which can easily be incorporated into existing AMD treatment plants, not only reduces the sludge disposal problems but also creates revenue from waste.

Evaluation of charcoal ash nanoparticles pollutant removal capacity from acid mine drainage rich in iron and sulfate

Passive co-treatment of phosphorus-depleted municipal wastewater with acid mine drainage: Towards sustainable wastewater management systems

Acid mine drainage (AMD) is the largest environmental problem facing the world mining and processing industry because it has low pH and can contain high concentrations of potential pollutants. Biomass ash (BA) can be considered as a potential material for AMD treatment. The main goal of this work was to investigate potential use of Biomass ash of CPK-LA and PK-LA types for AMD remediation. Four UK BAs from different fuels (i.e. straw, meat and bone meal, poultry litter), synthetic AMD, and raw AMDs (Belovo and Ursk) were used for the AMD treatment experiments. Batch experiments showed that in 1 h the biomass ash from straw combustion can effectively neutralise the synthetic AMD and the Belovo AMD with removal of potential pollutants at the liquid-to-solid ratio (L/S) of 100–250 and 10–50, respectively. The biomass ashes from straw and poultry litter combustion can effectively remove pollutants from the Ursk AMD at L/S 100 and adjust pH. The metal concentrations of those treated AMDs met receiving water quality standards. Potential pollutants precipitated as carbonate/hydroxide/sulphate, co-precipitated with Fe oxyhydroxides and Ca phosphates, and appeared as new phases such as Ca, Cu, Zn phosphates and Ca, Fe phosphates. This investigation is essential for development of appropriate, environmentally friendly and economically rational waste management.Graphic