Mechanistic investigation of phosphoprotein enrichment by fly ash-based chromatography

In this work, the mechanistic details contributing to the binding of phosphoproteins on fly ash (FA) has been investigated. The effects of factors influencing adsorption of phosphoprotein, i.e., contact time, pH, ionic strength, initial concentration of proteins, and contribution of ligand exchange, were thoroughly examined. Results showed that the adsorption efficiency of phosphoproteins to FA was enhanced with increasing contact time. Intriguingly, the adsorption of phosphoproteins to FA was not profoundly affected by high ionic strength, suggesting that electrostatic interaction does not play a pivotal role in phosphoprotein binding on the surface of FA particles. The interaction between phosphoproteins and FA could be instead disturbed when NaF and phosphate ion were used as competing electrolytes/ions. Also, it was found that at a high pH condition has a substantial effect on the adsorption of phosphoproteins through ligand exchange mechanism. To this end, our results clearly indicated that ligand exchange mechanism exerted by F^-, phosphate ion and hydroxide ion with the metal oxide surface of FA is the mechanism that majorly contributed to the phosphoprotein binding on the surface of FA particles.