ACTIVATED CARBON SURFACE MODIFICATIONS BY NITRIC-ACID, HYDROGEN-PEROXIDE, AND AMMONIUM PEROXYDISULFATE TREATMENTS

A series of activated carbons with different degrees of activation was treated with HNO3, H2O2, and (NH4)(2)S2O8 in order to introduce oxyge n surface complexes. The effects of the oxidizing treatments on the su rface area, the pore texture, and the surface chemical nature were ana lyzed by means of N-2 and CO2 adsorption, mercury porosimetry, FTIR, T PD, electrophoretic, and mass titration measurements. Results obtained show that the HNO3 treatment affects the surface area and the porosit y of the samples to a greater extent than the other treatments. Carbox yl groups were essentially fixed after the three treatments, although ketone and ether groups, as detected by FTIR, were also fixed after th e treatments with peroxides. The most important conclusion was that th e stronger acid groups were fixed after the (NH4)(2)S2O8 treatment rat her than after the HNO3 treatment, in spite of the fact that this latt er treatment fixed the largest number of oxygen complexes that evolved as CO2.