Removal of Cu(II) and Cd(II) from aqueous solution by seafood processing waste sludge

Dried waste slurry generated in seafood processing factories has been shown to be an effective adsorbent for the removal of heavy metals from dilute s olutions. Characterization of the sludge surface with scanning electron mic roscope and X-ray microanalyzer were carried out to evaluate the components on the sludge surface that are related to the adsorption of metal ions. Al uminum and calcium, as well as organic carbon are distributed on the surfac e of sludge. Alkalimetric titration was used to characterize the surface ac idity of the sludge sample. The surface acidity constants, pK(a1)(s) and pK (a2)(s) were 5.50 and 9.55, respectively. Batch as well as dynamic adsorpti on studies were conducted with 10 to 5 x 10(-3) M Cu(II) and Cd(II). A surf ace complexation model with the diffuse layer model successfully predicted Cu(II) and Cd(II) removals in single metal solutions. Predictions of sorpti on in binary-adsorbate systems based on single-adsorbate data fits represen ted competitive sorption data reasonably well over a wide range of conditio ns. The breakthrough capacity found from column studies was different for e ach metal ion and the data reflect the order of metal affinity for the adso rbent material very well, (C) 2000 Elsevier Science Ltd. Ail rights reserve d