Anionic Dye Alizarin Red S Removal Using Heat-Treated Dolomite

Abstract

In modern society, frequent use of synthetic materials in the household and industry presents a great challenge to environmental and water quality. As such, numerous types of research have been conducted for potential removal of emerging contaminants from water using advanced materials. Earth materials, due to their low costs and vast reserves, have also been evaluated in great details for contaminant removal. In this study, a naturally occurring carbonate mineral dolomite (Dol) was assessed for the removal of an anionic dye alizarin red S (ARS) from aqueous solution before and after heat treatment to increase its performance. The ARS-removal capacities increased from 80 to 130 mmol/kg after heat treatment based on the isotherm study. And the ARS-removal efficiency rose by a factor of four as the partitioning coefficient increased from 1.5 to 6 L/mmol after heat treatment. The X-ray diffraction (XRD) analyses showed minute conversion of dolomite into calcite after samples being heated at 800 °C for 3 h. However, there were no phase changes for ARS before and after its sorption. Fourie transform infra-red (FTIR) results also showed a minute appearance of calcite after heating. Thus, the increase in ARS sorption could be due to surface reactivation of Dol after heating or due to formation of a minute amount of amorphous MgO in the system as a result of the conversion of Dol to calcite. The results from this study will add new perspectives to the utilization of Earth materials for environmental application.