Adsorption of copper on amine-functionalized SBA-15 prepared by co-condensation: Equilibrium properties

SBA-15 functionalized with 3-aminopropyltrimethoxy-silane was synthesized by co-condensation and used as adsorbent for Cu2+ ions in aqueous solution. The adsorption capacity increased dramatically with increasing temperature, initial copper concentration and pH (up to ca. 6.5). Under suitable conditions, the material exhibited high adsorption capacity even at very low copper concentration. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). The adsorption isotherms of Cu2+ on propylamine-functionalized SBA-15 silica were best fitted by the Sips and Redlich–Peterson models. Regeneration of the adsorbent was investigated by treatment of the copper-loaded material with aqueous solution of 0.1 M HCl then 0.1 M NaHCO3 or by 0.1 M EDTA solution. The adsorption uptake after ten cycles was 90% and 60% of the fresh material adsorption capacity for regeneration with EDTA and acid/base treatment, respectively.