Dye adsorption onto activated carbons from tyre rubber waste using surface coverage analysis

Two types of activated carbons from tyre char (with or without sulphuric acid treatment) were produced via carbon dioxide activation with BET surface areas in the range 59–1118 m2/g. Other characterisation tests include micropore and mesopore surface areas and volumes, pH, and elemental compositions, particularly heteroatoms such as nitrogen and sulphur. They were correlated to the adsorption capacity which were in the range of 0.45–0.71 mmol/g (untreated) and 0.62–0.84 mmol/g (acid-treated) for Acid Blue 25. In the case of larger-sized molecules like Acid Yellow 117, capacities were in the range of 0.23–0.42 mmol/g (untreated) and 0.29–0.40 mmol/g (acid-treated). Some tyre carbons exhibit a more superior performance than a microporous, commercial activated carbon (Calgon® F400). By modelling the dye adsorption equilibrium data, the Redlich–Peterson isotherm is adopted as it has the lowest SSE. Based on the surface coverage analysis, a novel molecular orientation modelling of adsorbed dyes has been proposed and correlated with surface area and surface charge. For the acid dyes used in this study, molecules were likely to be adsorbed by the mesopore areas.

Pore volumes of activated carbons from tyre chars pre-treated by H2SO4. Acid-treated chars reveal the lower reactivity that enables gasification to proceed under reaction limited phase. Both micro- and mesopores continue to develop even at 16 h of gasification.Figure optionsDownload high-quality image (64 K)Download as PowerPoint slide