As part of CORFO’s Crea y Valida Program to foster innovation, SMI-ICE-Chile’s Environmental Rehabilitation team will develop the study “Water Resilience for Climate Change: Pilot Validation of Passivation Technology to Ensure Quality Water.”
The project focuses on the pilot-scale validation of sulfide passivation technology as an essential method to ensure water quality, and thus promote sustainable development in response to the challenges of climate change. The initiative also seeks to strengthen the resilience of the mining industry and communities by preventing acid rock drainage (ARD).
Sulfide passivation technology is an innovative alternative to conventional solutions, such as high density sludge (HDS) treatment plants, since it generates a chemically inert barrier on sulfide minerals, such as pyrite, preventing and/or reducing the release of sulfuric acid, arsenic and heavy metals, thus preserving the integrity of water sources.
Shifts in precipitation patterns and water availability resulting from climate change have exacerbated the challenges associated with acid rock drainage (ARD). The greater frequency and intensity of extreme weather events has produced more marked variations in the quality and availability of water, affecting the industry and communities that depend on this vital resource.
Climate change and acid rock drainage generated from abandoned, closed and active mining sites represent one of the biggest environmental problems facing humanity. Due to their high reactivity, chemical composition and toxicity, ARDs are one of the greatest environmental challenges, with toxic heavy metals being dissolved and transported by surface waters to agricultural areas, drinking water sources, sediments from rivers and/or the sea, which can alter the biotic communities and the composition of the aquifers. In the US, over 72,000 hectares of lakes and aquatic reserves have been adversely affected by such acid rock drainage.
Chile has 742 tailings deposits—104 active, 463 inactive, 173 abandoned and 2 under construction—that could be a potential source of acid drainage. Likewise, the progressive increase in the processing of low-grade copper sulfides due to the aging of the country’s largest deposits has generated more dumps and tailings with a high content of pyrite, the main precursor of ADR.
In 2015 SERNAGEOMIN and Fundación Chile published a “Survey of measures and technologies for preventing, controlling and treating mine drainage,” which explains how Chile’s experience in ensuring chemical stability is recent and therefore limited.
Currently, most ARD control technologies treat acidic effluents or isolate problematic (unstable) waste from dumps and/or tailings, so they do not solve the problem at its source. The most common of these is the high density sludge (HDS) treatment plant, a fairly effective chemical method but with high investment and operating costs.
A recent study estimated that the cost of ADR in the world’s four major mining countries (Canada, Australia, the US and South Africa) ranges from US$32-72 billion.
This project recently awarded to the SMI-ICE-Chile team is supported scientifically by the doctoral thesis of Felipe Saavedra at the University of Queensland, entitled Phosphate-induced hydrogeochemical stabilization of sulphidic lead-zinc tailings for rapid phytostabilization. His thesis developed a prototype for the chemical stabilization of lead and zinc mine tailings at Australia’s Mount Isa mine, which has already been validated on a laboratory scale.
In these tests on tailings in Australia, the proposed technology significantly reduced the risk of ADR, maintaining the chemical stability of mining waste.
Through a technology prototype that uses chemical reagents to passivate sulfide minerals, the project to be developed by SMI-ICE-Chile as part of CORFO’s Crea y Valida program hopes to prevent the formation of ADR in copper mining waste and also avoid the impact on water quality. “In addition to a substantial step forward, our proposal represents a transformation in the prevention of ARD and the optimization of processes in the mining industry,” says project director Felipe Saavedra. “Nationally and internationally, this optimized technology overcomes the limitations of existing approaches. We believe that the safety and effectiveness of our solution lie in its ability to effectively reduce the generation of ADR resulting from the interaction of sulfide minerals with oxygen.
“Compared to other chemical stabilization technologies, our optimized product stands out because of its efficiency and low cost,” adds Felipe Saavedra. “In terms of its practical applicability, it simplifies the operation and has the potential to significantly reduce the costs associated with HDS treatment plants (hydro desulfurization process). We believe that the proposed technology has the potential to mark a new era in the sustainable environmental management of the mining industry.”
This passivation technology is also essential for the socio-economic development of communities.
“Reducing acid rock drainage (ARD) is the project’s core aim,” explains Jacques Wiertz, alternate project director. “Precise quantification anticipates a significant decrease in the release of sulfuric acid, arsenic and heavy metals into waters. Furthermore, the preservation of water quality translates into the conservation of vital sources, preventing these minerals from releasing harmful substances.
“Adapting to climate change is another central aspect of this project, since it contributes to water quality and availability. In a scenario of altered precipitation patterns, sulfide passivation technology is projected as an effective strategic ally for managing climate impacts on the water supply.”
