Kinetics of alkaline hydrolysis of the insoluble protein fraction following enzymatic hydrolysis of chrome-tanned shavings

The problem of using chrome-tanned wastes (namely shavings) has been the subject of a number of reports. One path is enzymatic hydrolysis with possible utilization of both the protein fraction as well as chromium. After hydrolysis and subsequent filtration, a so-called filter (or chrome) cake is formed, which is composed of hydrated Cr 2 O 3 heavily contaminated with protein products of hydrolysis (removable, e.g. in washing) as well as with a non-hydrolysable fraction. The fraction requires breaking down, e.g. with strong alkali, as was performed in tests conducted to provide data for evaluating hydrolysis kinetics. Applying a number of simplifying assumptions, efforts were directed to expressing formal kinetics of this alkaline hydrolysis with a KOH solution. According to calculations, the reaction appears to agree well with a second-order reaction, with effective values of rate constant c = 3.9.10 - 3 l/(mol.s) and activation energy E a = 130 kJ/mol at hydrolysis temperature of 116°C.