Thermodynamic and Isotherms Studies on the Application of Modified Activated Carbon Developed From Periwinkle Shells for the Adsorption of Heavy Metals from Waste Water

The aim of this study was to investigate the thermodynamic properties of modified activated carbon developed from periwinkle shell carbon (PSC) for the adsorption of heavy metals (Fe+ and Pb) from waste water .Metalsadsorption from aqueous solutions unto periwinkle shell carbon was prepared (carbonized at 650oC and activated with phosphoric acid) and characterized to determine its physicochemical properties. Batch adsorption experiments were conducted to investigate the effects of process parameters (contact time, particle size, carbon dosage and initial concentration) on adsorption rate. Adsorption isotherms were analyzed using the Langmuir, Freudlich andTemkin isotherms while thermodynamic parameters such as enthalpy change (ΔHo ) , entropy change (ΔS o ) and Gibbsenergy change (ΔGo ) were determined. Results showed that adsorption rate increase with increase in contact time, adsorbent dosage and decreased with increase in particle size. Isotherm data showed that theFreudlich isotherm accurately described the adsorption data indicating that adsorption has a heterogeneous adsorbent surface. Thermodynamic parameters results showed that adsorption process was endothermic with enthalpy change (ΔHo ) of 96.38KJ/mol; a positive entropy change (ΔSo ) of 35.11 KJ/mol, indicating an increase in the degree of freedom (or disorderliness) of the adsorbed specie and a negative Gibbs-energy change (ΔGo ) at all temperature indicating that the adsorption process was spontaneous and favourable at high temperature. The study has showed PSC is a good adsorbent and it is effective enough for waste water treatment, as such it is recommended for integration with existing technologies to explore compatibilities with current water treatment systems and scale-ip studies should be conducted to evaluate performance in continuous flow system.