Acid mine drainage treatment using chicken eggshell waste

Resumen

Acid mine drainage (AMD) is a source of soil and water resources pollution. Calcite is a mineral constituted of calcium carbonate (CaCO₃). The AMD interaction with calcite drives their natural neutralization. Calcite is the main component of the chicken eggshell (ES). This work aimed to evaluate the use of ES waste as a material to treat raw AMD. Five treatments (T1, T2, T3, T4, and T5) were carried out with concentrations of 1, 2, 3, 4, and 5 ES g/L AMD, respectively. Each treatment was performed for 3 h at room temperature without agitation. The response variables analyzed were pH, redox potential (Eh), electrical conductivity (σ), chlorides (Cl^–), alkalinity, sulfates (SO₄^2–), nitrates (NO₃^–, and potentially toxic heavy metals and metalloids (PTHMM). Also, the removal efficiencies of SO₄^2–, NO₃^–, and PTHMM were analyzed. Additionally, the chemical and mineralogical composition of ES and precipitates were determined. The initial pH for AMD was 2.50 and it reached a final value of 5.50, 5.60, 5.80, 5.93, and 6.12 in T1, T2, T3, T4 and, T5, respectively. Moreover, the different treatments granted alkalinity to the treated effluents, reaching a maximum value of 124 CaCO₃ mg/L in T5. Finally, Al and Fe were completely removed from AMD, whereas Cu reached > 95 % removal, especially in T3, T4, and T5. Ba, Cr, and Pb showed an average removal of ~65 %. The ES concentration that showed the best results of neutralization and PTHMM removal efficiency was 5 ES g/L. The results showed that ES is a biocompatible waste material with an added value because it can be used as a sustainable material to treat raw AMD.