Effects of the supporting electrolyte on the kinetics of the removal of proteins adsorbed on a stainless steel surface by H₂O ₂-electrolysis

The effects of different types of supporting electrolytes on the removal of β-lactoglobulin (β-Lg) after being adsorbed to a stainless steel surface by a H₂O₂-electrolysis treatment was investigated. In this process, hydroxyl radicals (·OH), generated by the electrolysis of hydrogen peroxide, decompose the substances adhering to the surface. The removal of the adsorbed protein from the stainless steel surface during the treatment was monitored in situ by ellipsometry. The apparent first-order removal rate constants, k_cl, for 17 types of supporting electrolytes were determined, as well as the current corresponding to the rate of generation of ·OH. The k_cl and generated current values for LiCl, NaCl, KCl, KNO₃, K₂SO₄, CH₃COOK, and K₂CO₃ were all similar. Ca²⁺ and Mg ²⁺ strongly suppressed the removal of the adsorbed protein. The presence of ammonium compounds led to an increase in k_cl and current values. In H₂O₂-electrolysis in the presence of potassium phosphate, the removal was extremely rapid, and an apparent increase in the thickness of the adsorbed layer was observed. The mechanisms responsible for the peculiar effects of calcium, magnesium, phosphate, and ammonium compounds were investigated by means of a Fourier transform infrared (FTIR) spectroscopic analysis, as well as by the characteristics of the removal under different treatment conditions.