Ultrasound enhanced adsorption and desorption of chromium (VI) on activated carbon and polymeric resin

The effect of ultrasound on the adsorption and desorption of Cr(VI) on activated carbon and PVC–PPA resin were investigated. The results indicated that, on resin, the adsorption rate increased and the equilibrium time decreased obviously in the presence of ultrasound, while on activated carbon, ultrasound only enhanced the adsorption rate slightly at the initial stage of adsorption. Ultrasound didn't influence the desorption rates of Cr(VI) from both activated carbon and resin in distilled water. The addition of NaOH to the system caused an enhancement of Cr(VI) desorption, especially on activated carbon in the presence of ultrasound. After acid-treatment, the ultrasonic regenerated activated carbon had a good re-adsorption capacity.

Research highlights
► Using ultrasound to enhance Cr(VI) adsorption on activated carbon is unnecessary.
► Ultrasound is beneficial for Cr(VI) adsorption on PVC–PPA resin.
► Ultrasound and NaOH had synergistic effect on Cr(VI) desorption.
► Ultrasonic regenerated activated carbon has a good re-adsorption capability.