After a desired contact time, the amount of 2,4-D in the liquid phase
was analyzed by absorbance measurement using a double beam
UV/Visible spectrophotometer (Shimadzu, Model UV 1700, Japan)
at 283 nm. The adsorption capacity after a given contact time t, qt
(mg/g) and the percent removal, R (%), were calculated using Eqs.
(1) and (2), respectively.