Simultaneous co-adsorptive removal of phenol and cyanide from binary solution using granular activated carbon

The present study deals with the equilibrium, kinetic and thermodynamic modeling of simultaneous co-adsorption of phenol and cyanide from binary solution onto Granular Activated Carbon (GAC). The effect of process parameters like pH, temperature, adsorbent dose and contact time on the adsorptive efficiency has been evaluated. At an optimum pH 8, temperature 30 °C and adsorbent dose of 30 g/L, 79.9% of 200 mg/L phenol and 93.6% of 20 mg/L cyanide were removed. Four multicomponent isotherms were applied to the experimental data conducted at an initial concentration range of 100-1000 mg/L. Single component isotherms viz. Langmuir and Freundlich were applied to determine the multicomponent isotherm parameters. It was found that phenol adsorption followed extended Langmuir isotherm while cyanide adsorption followed extended Freundlich isotherm in multicomponent system. The monolayer adsorption capacity of GAC was found to be 269.7 and 1.95 mg/g for phenol and cyanide, respectively as calculated by extended Langmuir isotherm. Adsorption of phenol and cyanide followed pseudo-second order kinetics indicating chemisorption to be the mechanism of adsorption. Thermodynamic parameters viz., ΔG0, ΔH0 and ΔS0 were −3.5174 KJ/mol, −10.326 KJ/mol, −0.0225 KJ/mol-K for phenol and −6.5575 KJ/mol, 14.044 KJ/mol and 0.0679 KJ/mol-K for cyanide adsorption, respectively. Thermodynamic studies established the process of phenol adsorption onto GAC as exothermic and spontaneous in nature while of cyanide as endothermic in nature.