RECOVERY OF SILVER FROM AQUEOUS SOLUTION BY WATER HYACINTH (EICHHORNIA CRASSIPES) ROOTS

Abstract

Roots of water hyacinth, Eichhornia crassipes, were found to have biosorption capacity for silver. To evaluate the biosorption capacity and characteristics, the effect of solution pH, dose of biosorbent loading, contact time, temperature and initial silver concentration were investigated in a batch mode. The Langmuir and Freundlich adsorption models were used for mathematical description of the sorption equilibrium. Equilibrium data was fitted to the Langmuir model at 293 and 398 K and concentrations of 10-150 mg L-1. Based on the Langmuir isotherm plots, the maximum biosorption capacity value was calculated to be 141.54 mmol g(-1) at 293 K. Various thermodynamic parameters, such as Delta G degrees, Delta H degrees, and Delta S degrees, were evaluated with results indicating that this system was an exothermic spontaneous reaction and kinetically suited to pseudo second order model.