In situ generation of a hydroxyl radical by nanoporous activated carbon derived from rice husk for environmental applications: kinetic and thermodynamic constants

The objective of this investigation is to evaluate the hydroxyl radical (OH) generation using nanoporous activated carbon (NPAC), derived from rice husk, and dissolved oxygen in water. The in situ production of the OH radical was confirmed through the DMPO spin trapping method in EPR spectroscopy and quantitative determination by a deoxyribose assay procedure. NPAC served as a heterogeneous catalyst to degrade 2-deoxy-D-ribose (a reference compound) using hydroxyl radical generated from dissolved oxygen in water at temperatures in the range 313-373 K and pH 6, with first order rate constants (k = 9.2 x 10(-2) min(-1), k = 1.2 x 10(-1) min(-1), k = 1.3 x 10(-1) min(-1) and k = 1.68 x 10(-1) min(-1)). The thermodynamic constants for the generation of hydroxyl radicals by NPAC and dissolved oxygen in water were Delta G -1.36 kJ mol(-1) at 313 K, Delta H 17.73 kJ mol(-1) and Delta S 61.01 J mol(-1) K-1.