Precipitation as the main mechanism for Cd(II), Pb(II) and Zn(II) removal from aqueous solutions using natural and activated forms of red mud

The red mud (RM) has been used as an alternative low-cost adsorbent to remove trace elements, with the adsorption onto sodalite surface described main removal mechanism for elements. However, recent studies have shown that precipitation might be of great importance some metals using natural and thermal activated RM. Therefore, aim this study was identify responsible Cd(II), Pb(II) Zn(II) from aqueous solutions forms RM, based on sequential extractions a kinetic model developed. Results showed carbonate fraction highest elements (ca. 85%), minerals assemblages precipitated: otavite – CdCO3, cerussite - PbCO3, smithsonite ZnCO3 anglesite PbSO4. mineral limit due HCO3− consumption during formation new minerals. Hence, central removal, regardless or This finding raise doubt about effectiveness traditional isotherms kinetics models describe contributing insights future researches involving these hazardous materials.