Adsorption of anionic and cationic dyes from single and binary systems by industrial waste lead–zinc mine tailings

Abstract

The potential of using lead–zinc mine tailings (LZMT) as an adsorbent for the removal of anionic dyes (Acid Red (AR) and Acid Fuchsine (AF)) and cationic dyes (Basic Violet 5BN (BV) and Basic Green (BG)) from single and binary systems was investigated. The adsorbent was characterised by SEM, ICP-AES and XRD. The adsorption study was carried out by varying parameters such as the solution pH and the adsorbent dose. The results showed that the adsorption of the ionic dyes was pH-dependent; the maximum removal of AR and AF was 95.37 and 62.74% at pH 2.0 and 30 °C using 2.0 g LZMT and 100 mg L⁻¹ dye, and 83.63 and 97.04% for BV and BG at pH 7.0 and 40 °C, respectively. Kinetic studies indicated that the adsorption of LZMT for ionic dyes in single and binary systems both fitted better with a Lagergren pseudo-second order model, and the equilibrium data conformed well with a Freundlich model. XRD analysis showed that the manganese oxides within the LZMT damaged the dye chromophore by redox reactions and enhanced the effect of decolourisation.