Biosorption of copper, nickel and cobalt ions from dilute solutions using BSA-coated air bubbles

This study probed the competitive biosorption behavior of a ternary system containing copper, nickel and cobalt ions using a novel material known as air-filled emulsion (AFE). AFE is a stable colloidal suspension in which fine protein-coated bubbles (<10 μm) generated by an ultrasonic technique are dispersed through the aqueous solution, introducing a high surface area between protein as an extractant and metal ions. Effect of different experimental conditions including metal solution pH, temperature, biomass dosage and metal ion concentration on metal ion uptake was investigated. It was observed that an increase in pH led to greater metal uptake; although, bovine serum albumin (BSA)-coated bubbles illustrated higher affinity for copper ions than for nickel and cobalt ions. Increasing the temperature up to 65 °C increased copper uptake to roughly 98%; however nickel and cobalt removal did not exhibit a significant change. BSAEM also demonstrated very different adsorption behaviors for copper, nickel and cobalt at various biomass and metal ion concentrations. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results revealed that amino, carboxylic and thiol groups of BSA-coated microcells are the active sorbing sites for metal ion uptake in the solution.