The Equilibrium and Thermodynamics of Methylene Blue Uptake onto Ekowe Clay; Influence of Acid Activation and Calcination

The equilibrium isotherm study verified that the linear Freundlich model best explained the adsorption data and mechanism. The maximum adsorption capacities, 9.709, 13.889, and 18.868g/g for RS, RCS and ACS respective obtained from the Langmuir isotherm model at 25oC. Verifiable with increased filtration rates, acid activation and calcination improved the clay porosity and the total surface area RS-22.04, RCS-30.36 m2g-1 and ACS-40.92m2g-1. Sample PZCs were less than solution pH indicating cation affinity and enhanced dye adsorption. Dye uptake varied with temperature and adsorption equilibrates around 80min. Langmuir model (DeltaG#730lt-5KJ/mol) and thermodynamics (DeltaG#730gt-18kJ/mol and DeltaH) revealed a spontaneous and exothermic physisorption of MB dye onto the raw and modified samples. DeltaS* suggested an associative adsorption mechanism and DeltaSo proposed an induced randomness and changes at the solute/solvent interface