Detergency Effect of Trisodium Phosphate on the Removal of Bovine Serum Albumin from Alumina Surfaces during Caustic Alkali Cleaning

The detergency effect of trisodium phosphate (Na3PO4) on the removal of irreversibly adsorbed bovine serum albumin (BSA) from alumina (Al2O3) particles during cleaning with 0.05 M NaOH solution was kinetically studied. The desorption curve of BSA, obtained by plotting the logarithm of the amount of residual BSA against cleaning time, during cleaning with the NaOH solution with and without Na3PO4 could be apparently reduced to the sum of two straight lines with different slopes. This fact suggested that two species of BSA, i.e., a fasterdesorbing species (BSAf) and a slower-desorbing species (BSAs), were present on Al2O3 surfaces and desorbed according to a first-order process. The first-order desorption rate constant (ks) of BSAs obtained from cleaning with the NaOH solution alone was approximately 56-fold lower than that (Kf) of BSAf. The addition of Na3PO4 to the NaOH solution had no influence on the desorption of BSAf, whereas it accelerated the desorption of BSAs, with an approximately 7-fold increase in the ks. Potentiometric titration showed that phosphate ions were adsorbed on Al2O3 surfaces after cleaning with the NaOH solution containing Na3PO4. The results indicated that hydroxide ion and phosphate ions could displace the slower-desorbing BSAs species at Al2O3-water interfaces in a synergistic manner.