Tyre-derived activated carbon – textural propertiesand modelling of adsorption equilibrium of n-hexane

There is general agreement that primary pyrolysis products of end-of-life tyres should be valorised toimprove the economics of pyrolysis. In this work, tyre pyrolysis char (TPC) is produced in a pyrolysispilot plant designed and built at our home university. The produced TPC was upgraded to tyre-derivedactivated carbon (TDAC) by activation with CO2, and then characterised using stereological analysis(SA) and nitrogen adsorption at 77 K. SA showed that the grains of TPC and TDAC were quasi-spherical and slightly elongated with a 25% increase in the mean particle cross-section surface area forTDAC. The textural properties of TDAC demonstrated the BET and micropore surface areas of 259 and70 m2/g, respectively. Micropore volume and micropore surface area were 5.8 and 6.7 times higher forTDAC than TPC at2nm, respectively. Then-hexane adsorption was investigated using experimentsand modelling. Eight adsorption isotherms along with three error functions were tested to model theadsorption equilibrium. The optimum sets of isotherm parameters were chosen by comparing sum ofthe normalized errors. The analysis indicated that the Freundlich isotherm gave the best agreementwith the equilibrium experiments. In relation to different activated carbons, the adsorption capacityof TDAC forn-hexane is about 16.2 times higher than that of the worst reference material and 4.3times lower than that of the best reference material. In addition, stereological analysis showed thatactivation with CO2did not change the grain’s shape factors. However, a 25% increase in the meanparticle cross-section surface area for TDAC was observed.