Hydrogen peroxide cleaning of residues from surfaces

This research has focused on minimizing waste generation during cleaning operations in pharmaceutical, fine chemical, photography, and military industries. These industries and EPA have aggressively sought means of eliminating the traditionally employed organic cleaning solvents. The research herein has focused on developing a novel aqueous cleaning system employing a low concentration, alkaline hydrogen peroxide solution to replace organic solvents, and on the kinetics and reaction mechanisms.This novel H2O2 cleaning system has been found herein to effectively replace organic solvents in cleaning recalcitrant residues from industrial reactor surfaces, where asphalt was extensively evaluated as a surrogate for such residues. A 3% H2O2 aqueous solution at 70°C and pH 8.5--9.5 effectively removed 100% of an asphalt coating from a glass surface within 45--60 minutes, even when the asphalt had been air-dried onto the surface for a week. Gas formations were observed at asphalt-glass-solution interfaces using the Surface Imaging Spectroscopy technique. Microscopic gas pockets were found to form underneath the edges of the asphalt coating and help accelerate the cleaning process by prying off the coating as the reactions between the asphalt and H 2O2 progressed along the interface.The thermokinetic properties of hydrogen peroxide decomposition and reactions were investigated using the Accelerating Rate Calorimeter (ARCTM) and adiabatic calorimetry at different pHs, in the presence of ferric catalysts, and at different surfaces. The lowest, second order observed rate constant for a "pure" alkaline-induced H2O2 decomposition was obtained as 5.89 x 10-8 M-1s -1 at 30°C, using 3% H2O2 at pH 9.5--11.8 in Pyrex-glass containers. The second order rate constant of the rate determining step between H2O2 and HO2 for the alkaline-induced H2O2 decomposition was obtained as 0.019 M-1 s-1 at 30°C, using 5% H2O 2 in titanium containers. The second order rate constant of the rate determining step between Fe(III) and HO2 for ferric catalyzed H 2O2 decomposition was obtained as 3.58 M-1s -1 at 30°C, using 5% H2O2 at pH 9.5--11.8 in Pyrex-glass containers.Another main objective was the implementation and modification of the ARCTM technique and adiabatic calorimetry to analyze thermokinetic properties and to interpret reaction mechanisms of H2O2 systems.