Modeling of chromium (VI) adsorption from aqueous solutions using Jordanian Zeolitic Tuff.

The probable use of Jordanian natural zeolitic tuff in wastewater treatment as natural adsorbent for the removal of Cr (VI) ions from aqueous solution in continuous fixed bed columns was tested experimentally and theoretically. The tested zeolitic tuff was obtained from Al Hala volcano (HZ) located in southern part of Jordan and subjected to crushing and sieving only without any further treatment. Experimentally the HZ grains were packed in a fixed bed column. The used grain sizes are HZ1 (1.0-0.60 mm) and HZ2 (0.60-0.30 mm). The adsorption capacity was evaluated using breakthrough curves and by applying the Thomas and Yoon and Nelson models. The Thomas model analysis of the measured breakthrough curves revealed that the adsorbent HZ2 has a higher adsorption capacity to Cr (VI) ions (56.3 mg/g) than HZ1 (35.5 mg/g). The time elapsed to reach 50% breakthrough was determined by the Yoon and Nelson model. The time to reach 50% breakthrough is 318.78 min and 368.18 min for HZ1 and HZ2, respectively. The research results indicate that the small size fraction (HZ2) is more suitable and effective as adsorbent material than the size fraction (HZ1) due to its high surface area.