Biosorption of cationic dyes from aqueous solution by Water hyacinth roots

Water hyacinth Eichhornia crassipes was found to have biosorption capacity for cationic dyes,
malachite green and methylene blue from aqueous solutions. To evaluate the biosorption capacity
and characteristics, the effect of solution pH, initial dye concentration, temperature, dose of
biosorbent loading, contact time and shaking rate were investigated in a batch mode. Biosorption
was increased with the increasing temperature for both studied dyes. The Langmuir and Freundlich
adsorption models were used for mathematical description of the sorption equilibrium. Equilibrium
data was fitted well to the Langmuir model in the studied concentrations (1-200 mg L-1) at 293 and
313 K. Based on the Langmuir isotherm plots the maximum biosorption capacity values were
calculated to be 44.64 mg g-1 for malachite green and 42.55 mg g-1 for methylene blue at 313 K.
Various thermodynamic parameters such as ΔGo, ΔHo, and ΔSo were evaluated with results
indicating that this system was an endothermic spontaneous reaction and kinetically suited to
pseudo-second-order model.