Preparation and evaluation of orange peel cellulose adsorbents for effective removal of cadmium, zinc, cobalt and nickel

The preparation of chemically modified orange peel cellulose adsorbents and its biosorption behaviors of Co(II), Ni(II), Zn(II) and Cd(II) have been studied. Effects of different chemical modifications on the adsorbent properties including different alkalis saponification (NaOH, NH4OH, and Ca(OH)2) and different acids (C6H6O7·H2O, H2C2O4, and H3PO4) modification after saponification with NaOH were investigated. The FT-IR spectra showed that there are different functional groups in adsorbents, which are able to react with metal ions in aqueous solution. The maximum adsorption capacities of Ni(II), Co(II), Zn(II) and Cd(II) for SPA, SPA, SCA and SOA were obtained as 1.28, 1.23, 1.21 and 1.13 mol/kg and have increased by 95, 178, 60 and 130% compared to raw orange peel, respectively. Effects of initial pH, initial metal ions concentrations, shaking time and solid/liquid ratio on metal ions biosorption were also investigated. Biosorption equilibriums were rapidly established in about 60 min and the adsorption kinetics followed the Lagergren first-order kinetics model. The Langmuir and Freundlich adsorption isotherms models fitted the experimental data best with regression coefficient R2 > 0.95 for all the metal ions. Elution efficiencies with different concentrations of HCl were evaluated.