Removal of heavy metal ions from industrial effluents using low cost adsorbents in packed bed column

Abstract

The present work researches the removal of Cu & Cd ions using mixed adsorbent prepared by blending activated charcoal and bone charcoal in 1:1 ratio for both batch and continuous flow operation. The adsorption mechanism follows a chemisorption process due to the synergistic effect associated by contribution of high surface area from the activated charcoal (1600 m2/g) and negative charge from the bone charcoal. The potential capacity of the mixed adsorbent material for the removal of Cu (II) and Cd (II) from the prepared synthetic metal ion solution was studied by optimizing various parameters in the batch study and these optimized parameters are used in the continuous flow operation to find the effect of adsorbent dose and volumetric flow rate at a constant initial metal ion concentration of 100 ppm. The batch adsorption studies has been carried out for 2 hrs considering all the 6 parameters by optimizing each of them. The effect of pH, temperature, initial metal concentration, agitation (high speed rotation) rate, adsorbent dose and contact time were studied with respect to reaction time until the achievement of equilibrium. The maximum removal for Cu (II) was 97.21% and Cd (II) was 78.76% obtained at 2 hrs for pH 6. The % removal for Cu varies from 87.16 to 99.74% at an adsorbent dosage of 5 g/L, pH 6, initial metal ion concentration of 50mg/l,agitationrateof180rpm,andatatemperatureof25oC.SimilarlyforCd(II)itvariesfrom 70.23 to 88.4% at 5 g/L respectively at the same operating conditions. The % removal for Cu (II) was 99.75% and for Cd (II) it was 88% at a temperature of 40oC. Confirmation experiments were carried out using the industrial effluents with mixed adsorbent, and low cost (maize cobs) in batch studies and the results were compared with synthetic solution, industrial effluents and maize cobs. The column study experiments were carried out for copper and cadmium by different bed heights (12 cm, 24 cm, 36 cm) with fixed volumetric flow rate of 10ml/min. The optimized % removal parameter for column studywas foundtobe36cmand10 ml/min, andfurtherexperiments were carried at fixed bed height of 36 cm and variation of volumetric flow rates from 10 ml/min to 30 ml/min. Simultaneous metal ion removal studies were carried out in batch mode to study the effect of pH, effect of adsorbent dosage and effect of contact time.