Solvent effect on the electrophoretic mobility and adsorption of Cu on iron oxide

The adsorption of Cu2+ from the aqueous and aqueous–organic mixed solution on the iron oxide was studied as a function of temperature, pH and concentration of metal ions. The sorption of Cu2+ in the presence of different solvents followed the trend: aqueous–ethanol > aqueous–methanol > aqueous media, which is parallel to the increasing order of their dielectric constants. The electrophoretic mobility of the solid was studied to probe the adsorption mechanism. We observed that the electrophoretic mobility of the iron oxide in the presence of Cu2+ increases with the increase in pH of the suspension. However, a decrease in the electrophoretic mobility with the increase in concentration of metal cation showed the onset of the precipitation of the corresponding hydroxide on the surface of Fe2O3 particle. The solvent effect on the electrophoretic mobility of iron oxide followed the trend: aqueous > aqueous–methanolic > aqueous–ethanolic. We applied different models to explain the mechanism of the adsorption process.