Surface chemistry and porosity of nitrogen-containing activated carbons produced from acrylic textile waste

Abstract

Acrylic textile waste was pyrolysed in a fixed bed reactor in a nitrogen atmosphere at three different temperatures, 700, 800 and 900°C. Steam activation of the chars generated at these temperatures was carried out for different durations of activation time up to 4h at 900°C temperature to produce activated carbons. The BET surface area and the pore structure of the pyrolysis chars and activated carbons were evaluated from nitrogen adsorption data at 77K in relation to process conditions. The BET surface area of the pyrolysis chars were all less than 2m2g−1, but significantly increased with steam activation to produce a maximum surface area of 752m2g−1 for the activated carbon produced from the char generated at 700°C and steam activated at 900°C for 2h. The porosity of the product activated carbon was mainly microporous with an increase in mesopore fraction at higher degrees of burn-off. The effect of burn-off on the acid/base properties and the surface chemistry of the activated carbon, in terms of carbon, nitrogen and oxygen functionalities, were studied in detail using titration method and X-ray photoelectron spectroscopy (XPS) respectively. The results showed that, for all activated carbon samples, the concentrations of basic groups are always much higher than that of acidic groups. Higher degrees of burn-off leads to a lower percentage of graphite, higher percentage of carbide, an increase in C-oxygen functionalities and the percentage of quaternary nitrogen, while the ratio of the N-5 functionality decreased.