Removal of Cu(II) in fixed bed and batch reactors using natural zeolite and exfoliated vermiculite as adsorbents

The ability of natural zeolite (clinoptilolite) and exfoliated vermiculite to remove copper from aqueous solutions was studied in fixed bed column and batch reactors. The effect of agitation speed (0, 100, 200, 400 rpm), temperature (25, 45, 60°C), and particle size [2.5-5.0 mm, dust (<0.25 mm)] and solution pH (1.00-4.00) on the removal of heavy metals was studied. Fixed bed experiments were conducted, using three different volumetric flow rates of 5-7-10BV (Bed Volumes)/h, under an initial normality of 0.01 N (317.7 mg/L), at initial pH of 4.00 and ambient temperature (25°C). Vermiculite was found to be more effective for the removal of copper in batch mode reactors under all the tested conditions, while the removal efficiency follows the order: vermiculite > clinoptilolite dust > clinoptilolite 2.5-5.0 mm. The removal of Cu(II) using vermiculite reached 67.6%, at ambient temperature and at the agitation speed of 400 rpm, while it was approximately 42.5% at 60°C with no agitation. The highest removal level in the case of clinoptilolite use reached the percentage of 37.3% at the temperature of 60°C without agitation; the same removal efficiency was obtained at ambient conditions with an agitation speed of 400 rpm. Clinoptilolite dust is found to be more efficient than granular clinoptilolite under all the conditions that were tested. Agitation and temperature also affect the uptake of the specific ions. Finally, the acidity of the aqueous solution influences the removal of copper by minerals. In column studies, the decrease of the flow rate resulted in the increase of the removal efficiency.