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