THERMODYNAMICS OF CHLORINE ADSORPTION BY ACTIVATED CARBON FROM SELECTED LOCAL RAW MATERIALS

Abstract

Thermodynamics of chlorine adsorption by activated carbons from cattle bone (CB), coconut-shell (CS) and wood (WC) as influenced by method of activation (heat and acid) were studied using a commercial activated carbon (CC) as control. Batch chlorine adsorption by each activated carbon was investigated by contacting with fixed amount of chlorine solution at 10, 15, 20, 25, and 30 °C respectively at 10 minutes intervals. The temperature dependency of the mass transfer was verified using Arrhenius and van't Hoff equations. Heat (H) activation was at 950°C/3hr to produce heat activated bone carbon (HCB), and 850°C/2.5hr for heat activated coconut-shell(HCS) and wood carbon HWC) while concentrated phosphoric acid (A) (1:3-1:4) carbon: acid (w/w) was at 600°C/2hr to produce acid activated wood (AWC), acid activated coconut-shell (ACS) and acid activated bone(ACB) samples. Adsorption activation energies ranged from 11.058 kJ/mol (HCB) to 16.850kJ/mol for (CC). The changes in enthalpy and entropy of adsorption varied from 16585.4(HCB) to 26041.8(CC) J/mol°C and 2371.3 to 5817.8 J/mol°C with changes in Gibb's free energy of - 530.8(ACB) to -1562.2(CC) kJ/mol respectively indicating that mass transfer was spontaneous. This study indicated that efficient activated carbons could be obtained from local raw materials by controlled activation with acid or heat for home and industrial purposes.