Performance of slurry contact adsorber operating under high gravity for removal of fluoride

Abstract

Fine adsorbent particles though associated with large surface area and high adsorption rate are not employed in fixed bed adsorber for wastewater treatment due to high-pressure drop. In this investigation, slurry contact adsorption wherein fine adsorbent particles can be utilized was studied for the removal of fluoride using commercial activated charcoal as adsorbent (size<100 µm). The mass transfer operation was performed in two rotating contactors (rotating packed bed and rotating spiral) operating under centrifugal acceleration up to fifty times the terrestrial gravity, and conventional contactors (continuous stirred tank and fixed bed). The results indicated that the removal efficiency with slurry contact adsorption is higher in rotating spiral contactors compared to rotating packed bed or traditional contactors. Maximum utilization (equilibrium loading) of adsorbent particles at contactor exit is approached at high rotational speed and adsorbent dosage, and low feed flow rate and feed concentration. The magnitude of the volumetric mass transfer coefficient in a rotating spiral contactor obtained from mathematical modeling varied between 1.5 × 10−2 1/s to 8.0 × 10−2 1/s.