Removal of Dyes from Wastewater Using Bottom Ash

Municipal solid waste incinerator (MSWI) bottom ash was converted into a low-cost adsorbent, characterized and used for the removal of alizarin yellow, fast green, and methyl violet from wastewater. The percentages of removal of alizarin yellow (1.0 × 10-4 M), fast green (1.0 × 10-4 M), and methyl violet (1.0 × 10-4 M) on this adsorbent were 87.5, 97.0, and 73.0, respectively. In batch experiments, parameters studied include the effect of the adsorbate concentration, pH, sorbent dosage, temperature, and contact time. The optimum contact time for all of the three dyes has been found to be 4 h, while the maximum adsorption was observed at pH 5.5, 5.0, and 8.0 for alizarin yellow, fast green, and methyl violet, respectively. The adsorbent dose has been optimized as 10.0 g/L for the three dyes. Kinetic studies showed a rate of adsorption of first order with respect to the dye solution concentration. Adsorption processes were found to be film-diffusion-controlled for all of the three dyes. Thermodynamic parameters such as free energy, enthalpy, and entropy of adsorption of the dye-bottom ash systems were also evaluated.