Sorptive elucidation of rice husk ash derived synthetic zeolite towards deionization of coalmine waste water: A comparative study

Abstract

Synthetic zeolite (Z-RHA) produced from rice husk ash was used as adsorbent for decontaminating Fe (II), Cu (II) and As (V) laden aqueous solution. Impact of influential parameters viz. pH 1–7), adsorbent dose (0.03–1g/L), initial adsorbate concentration (1–100mg/L), agitation speed (100–180rpm), temperature (15–50°C) and contact time (30–1440min) on sorptive removal of contaminated ions were studied. Maximum removal percentage of Fe (II), Cu (II), and As (V) by zeolite Z-RHA was found to be 91.46%, 90% and 87.81% respectively. Adsorptivity of the three adsorbate ions onto Z-RHA was found in the order of Fe (II) > As (V) > Cu (II). Heterogeneity of the adsorbent had favoured the removal of Fe (II) and Cu (II) as compared to As (V) which followed a monolayer adhesion. Morphological study of Z-RHA revealed a crystalline structure. The elemental analysis confirms the presence of silica, aluminium and oxygen which forms the basic structure of a zeolite. Also, surface chemistry revealed the presence of multiple functional groups which were involved in the adsorbate uptake. Electronegativity of the adsorbate particles were responsible for the adsorption where As (V) followed physisorption; and Fe (II) and Cu (II) chemisorption as well-evidenced from the kinetic analysis. Although adhesion occurred mostly in the “Fast” phase, the rate of adsorption was limited by film diffusion in case of Fe (II) and Cu (II) and external mass transfer was found to be a rate-declining factor for As (V) adsorption. Desorbed and regenerated spent Z-RHA claimed multiple usage in the removal process which compensated its cost of production. Therefore, the synthetic zeolite Z-RHA obtained from rice husk ash was found to possess adsorptive potentials in treating contaminated aqueous solution.