The 8-mL vials were filled with a sorbate solution to minimize the headspace volumes of vials and sealed with aluminum foil-lined Teflon screw caps to avoid evaporation of sorbate, and then gentle
agitated at 30rpm on an end-over-end rotary shaker for 3 days at 25±0.5 ◦C to reach apparent equilibrium (kinetic tests indicated that sorption equilibrium was achieved in less than 48 h).