Surface Functional Characteristics (C, O, S) of Waste Tire-Derived Carbon Black before and after Steam Activation

Abstract

The effects of steam activation on the surface functional characteristics of waste tire-derived carbon black were investigated. Two carbon-based materials, powdered carbon black (PCB) and PCB-derived powdered activated carbon (PCB-PAC), were selected for this study. A stainless steel tubular oven was used to activate the PCB at an activation temperature of 900 °C and 1 atm using steam as an activating reagent. X-ray photoelectron spectroscopy (XPS) was adopted to measure the surface composition and chemical structure of carbon surface. Various elemental spectra (C, O, and S) of each carbon sample were further deconvoluted by peak synthesis. Results showed that the surfaces of PCB and PCB-PAC consisted mainly of COC and C—O. The PCB-PAC surface had a higher percentage of oxygenated functional groups (C═O and O—C═O) than PCB. The O_1s spectra show that the oxygen detected on the PCB surface was mainly bonded to carbon (C—O), whereas the oxygen on the PCB-PAC surface could be bonded to hydrogen (O—H) and carbon (C—O). Sulfur on the surface of PCB consisted of 58.9 wt% zinc sulfide (ZnS) and 41.1 wt% S═C═S, whereas that on the surfaces of PCB-PAC consisted mainly of S═C═S. Furthermore, the increase of oxygen content from 9.6% (PCB) to 11.9% (PCB-PAC) resulted in the increase of the pH values of PCB-PAC after steam activation.