Equilibriumstudies
Adsorption experiments were carried out by adding a fixed amount of sorbent (0.60 g) into a number of 250 mL-stoppered glass Erlenmeyers flasks containing a definite volume (0.20L in each case) of different initial concentrations (35–400 mg/L) of dye solution without changing pH and temperature 30◦C. The flasks were placed in a thermostatic water-bath shaker and agitation was provided at 130 rpm for 180 min to ensure equilibrium was reached. At time t=0 and equilibrium, the dye concentrations were measured using a double beam UV–vis spectrophotometer (Shimadzu, Model UV 1601, Japan) at 668 nm wavelength. After equilibrium, the sorbent was separated from the dye solution using filtration and the dye concentrations were similarly measured. The amount of adsorption at equilibrium, qe (mg/g), was calculated by