FIXED BED STUDIES FOR ADSORPTION OF NITROBENZENE AND HUMIC AICD BY ACTIVATED CARBON

Abstract

In the present study, continuous fixed-bed adsorption has been carried out in commercial grade activated carbon (ACC) packed bed for the removal of nitrobenzene and humic acid from aqueous solution. Experiments were done with nitrobenzene solution of concentration 50-200 mg/1 with pH kept around 6.0 and with humic acid solution was made with concentration 50-200 mg/1 with pH kept around 2.0. The effects of important factors namely bed height (Z=15-60 cm), influent concentration of solution (Co=50-200 mg/1), the flow rate (Q=0.02-0.04 1/min) and column diameter (D=2-4 cm) were studied. Higher uptake of nitrobenzene and humic acid was observed at highest Z. It was found that the time to breakthrough time (4) decreased with an increase in Co. The larger the Co, the steeper was the slope of the breakthrough curve and the smaller was the tb. The amount of nitrobenzene and humic acid adsorbed onto the unit bed height increased with an increase in Q leading to faster saturation at a higher value of Q. It was found that the adsorbent usage rate (Ur) decreased with an increase in EBCT. A 50% breakthrough curve between t and Z must result in a straight line passing through the origin, however, the straight line does not pass through the origin. The plot of 50% breakthrough (t0.5) versus Z curve did not pass through the origin indicating the adsorption of nitrobenzene and humic acid onto ACC occurred through complex mechanism. Adams—Bohart, Bed-Depth Service-Time, Thomas, Yoon—Nelson, Clark and Wolborska models has been applied to the experimental data for the prediction of the breakthrough point, and to determine the characteristic parameters of the column. Error analysis showed that the Yoon—Nelson model best described the experimental breakthrough curve, while Wolborska model showed good prediction of breakthrough curve for the relative concentration (C/Co) region up to 0.5.