Potential used of mining waste - fly ash -based alkali activated materials as an adsorbent to remove of copper, and arsenic ions from water

Chile, a major mining country, generates over 537 million tons of mine tailings annually, with volumes expected to continue increasing in the coming years. Additionally, due to freshwater scarcity, increasing water recirculation rates is essential. To address environmental and water scarcity challenges, abandoned copper mine tailings (Cu tailings) and fly ash (FA) were used as secondary raw materials to produce alkali-activated materials (AAMs), incorporating Ordinary Portland Cement (OPC) as an additive. Characterization results revealed that Cu tailings are primarily crystalline with quartz, while FA contains 68% amorphous content. The addition of OPC improved densification, reduced porosity, and enhanced the mechanical properties of the FA-AAM2 sample, achieving a compressive strength of 16 MPa after 28 days of curing, compared to 12 MPa for FA-AAM1 (without OPC). Leaching tests confirmed that heavy metal and metalloid concentrations remained within safety limits. In adsorption experiments, the materials effectively removed Cu (0.5 mg/g in FA-AAM1, 0.4 mg/g in FA-AAM2) and As (2.0 mg/g in FA-AAM1, 1.5 mg/g in FA-AAM2) from aqueous solutions.

In summary, the combination of Cu tailings, FA, and OPC successfully produced AAMs with good mechanical strength and adsorption capacity, offering a sustainable and value-added solution for the management and valorization of abandoned mine tailings.