Metal Pollution and Mining in the Iberian Pyrite Belt: New Remediation Technologies to Improve the Ecosystem Services of the River Basins

Abstract

The highly metal-contaminated Odiel-Tinto River basin, located in the Iberian Pyrite Belt (IPB), has been the focus of many environmental studies as a natural lab for biodiversity and environmentally catastrophic scenarios and as a reference site for mining places with similar conditions. This study demonstrates the feasibility and effectiveness of two different technologies to recover ecosystems affected by acid mine drainage (AMD) in the area of IPB. The current study compiles results of two newest technologies for AMD remediation: passive remediation (dispersed alkaline substrate—DAS) and a new disruptive technology (Adiabatic Sonic Evaporation and Crystallization—ASE&C) that purifies the contaminated water, obtaining two by-products (high-quality water and metal conglomerates) that improve the general quality of the ecosystem including biodiversity by eliminating more than 90% of the contaminants from AMD and mining waters. The removal of contaminants, enhancement of AMD treatment efficiency, and offset operating costs were compared and analyzed for the different uses of the decontaminated effluents, including an old tailing pond failure, the Aznalcóllar mining spill. The efficiency of the removal of elements from the contaminated water is significant using both technologies, although the passive DAS does not still reach the international benchmark for some compounds (such as Fe, sulfates, and Mn); whereas ASE&C obtains distilled water fulfilling all the international benchmarks with conductivity values lower than 120 µS cm−1 or metal concentrations lower than µg/L. Both technologies are eco-friendly and cost-effective as a result of the generation of valuable by-products such as fresh water and metal conglomerates as potentially commercial products while remediating aquatic ecosystems impacted by mining activities.

A New Disruptive Technology for Zero-Brine Discharge: Towards a Paradigm Shift

“…Recovering metals, metalloids and rare earth elements as a byproduct of depuration activities is challenging, but some important concentrations are found in brines, such as lithium, rubidium, and potassium. Thus, extraction from brines and other waste streams is becoming economically viable, as previously reported in [16] with mining lixiviates depurated with the ASE&C technology.…”

“…A new innovative technology, termed Adiabatic Sonic Evaporation and Crystallization (ASE&C), was designed and patented (World International Patent Organization: EP3135635) for contaminated fluid purification using a physical approach, distillation for the separation of liquids and dissolved solids by promoting adiabatic changes and acceleration (Figure 2) [16]. In this case, it completely separated a seawater sample into freshwater and crystallized salts with a cost of energy between 0 and 20 kWh/m 3 .…”

The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore

“…Sulfide ore flotation tailings, especially those containing large amounts of pyrite as well as other sulfide minerals (containing different non-ferrous metals), are sources of acid mine drainage (AMD) due to the complex process of sulfide oxidation via biotic or abiotic processes induced by water and oxygen availability. Sulfide oxidation results in the formation of secondary minerals, such as sulfates (poitevinite, melanterite, gypsum), hydroxides (goethite), hydroxysulfates (jarosite, alunite), carbonates (malachite, azurite, smithsonite, siderite), and arsenates (scorodite) and release of metal cations and sulfates into the liquid phase [7,[9][10][11][12][13][14][15][16].…”

“…These metals can be released into the liquid phase during the storage, which is harmful or potentially harmful to the environment, due to the migration of various released ions possessing long-term harmful effects in areas of tailing disposal. These harmful effects were noted in different regions with various climate conditions [9,[13][14][15][16][17][18][19][20].…”

“…The reserves of metals contained in flotation tailing in some sites may be estimated as significant due to the large volumes of wastes accumulated from decades of exploitation of some mineral deposits [15,17,21]. Therefore, investigations have been carried out in recent decades to estimate the possibility of metal extraction from old sulfide-containing tailings using different approaches, which include hydrometallurgical techniques (acid leaching (with sulfuric, organic, hydrochloric leaching), leaching with sodium chloride, cupric chloride, ammonium salts, different oxidants, cyanidation, column and stirred tank reactor bioleaching [2,8,18,[21][22][23][24][25][26][27][28][29], roasting [30] and flotation [3], as well as treatment of AMD formed in tailing disposal areas as source of metals [16]. The results of these studies suggest that valuable metals can be successfully extracted from these wastes and high levels of extraction can be reached, while the specific chemical and mineral composition and high iron content (in the form of pyrite and oxide minerals) result in difficulties in base metal extraction.…”