Investigation of the functional groups on the surface of activated carbons

Activated carbons were produced in the laboratory from wood using a 20-run Plackett-Burman experimental design for 19 factors. The obtained batches of activated carbon were analysed by potentiometric titration and FTIR spectros- copy to determine the surface functional groups. The results obtained by potentio- metric titration displayed the distribution of individual acidity constants of those groups in the pK range. Considering this parameter, the surface functional groups were divided into carboxyl, lactone and phenol. The linear regression equations re- flecting the influence of each operation used for the synthesis on the amount of these functional groups in the obtained activated carbons were generated. The FTIR spec- tra were used in parallel for the evaluation of the amount and the type of the surface functional groups. Relationships between the two data sets obtained by potentio- metric titration and FTIR spectroscopy were evaluated by correlation analysis. It was established that the amount of surface functional groups determined by poten- tiometric titration positively correlates with the intensity of the peaks of hydrophilic functional groups in the FTIR spectra. At the same time, the negative correlation be- tween potentiometrically determined amount of surface functional groups and the intensity of peaks of hydrophobic functional groups was observed. Most probably, these non-polar formations can take part in the interaction of carbon surface with H + /OH - ions and diminish the strength of existent functional groups.