Effect of temperature on equilibrium and thermodynamic parameters of Cd (II) adsorption onto turmeric powder

Batch adsorption of cd (ii) onto turmeric powder was conducted as a function of temperature. nonlinear langmuir,freundlich,dubinin-radushkevish (d-r) and temkin equilibrium models were employed. in addition to r2,five different error functions were used to determine best fit equilibrium isotherm model. it was found that freundlich isotherm model provided better fit for adsorption data at 298 and 303 k and langmuir model was suitable for the experimental data obtained at 310 and 313 k. it was found that increase in temperature decreased maximum adsorption capacities,showing that the adsorption of cd (ii) onto turmeric powder is exothermic. enthalpy values also confirmed the same trend. entropy values were negative which means that randomness decreased on increasing temperature. gibbs free energies were non spontaneous at all the temperatures studied. e values were in the range of 2.73-3.23 kj mol-1 which indicated that adsorption mechanism is essentially physical.