Removal of zinc from aqueous solutions using sea nodule residue

Sea nodule residue (SNR), a solid waste generated during the processing of polymetallic sea nodules for copper, nickel, and cobalt recovery, has been demonstrated to be an effective adsorbent for removing an inorganic pollutant such as zinc from wastewaters/industrial effluents by adsorption. The technology offers the potential for inexpensive recovery and reuse of a material normally discarded as a solid waste. Metal removal by this adsorbent was compared favorably with those achieved by commercial adsorbents. The adsorption experiments were performed, while varying adsorbent particle size (152–53 μm), adsorbent concentration (0.2–3% (w/v)), initial zinc concentration (75–500 mg l−1), shaking time (0.08–24 h), pH (1–6), and temperature (303–333 K). About 2.0 g of SNR was found to be sufficient to remove 99.8% of 200 mg l−1 zinc from 100 ml aqueous solution in 4 h, and the optimum pH value for maximum adsorption was found to be 5.5. The kinetic curves show very clearly the selectivity of SNR for zinc. The uptake obeys both the Freundlich and the Langmuir isotherms. The applicability of Lagergren kinetic model has also been investigated. Thermodynamic parameters were calculated to understand the nature of adsorption.