Preparation and characterization of porous adsorbent for chromium(VI) removal

Abstract

Chromium (VI) compounds are widely used in industry such as electroplating, meal finishing, leather tanning, pigments, etc. In recent years ground water is the main source of domestic water supply. Chromate poisoning cause severe skin disorders allergic dermatitis, liver and kidney damage. Thus chromium causes great public concern. A wide range of separation process has been investigated for the removal of Chromium (VI) from water. Adsorption using activated carbons posed to be the efficient method for removal of Chromium ions from water.
To use carbon as an adsorbent requires activation or surface modification of carbon. Methods like thermal and chemical methods of activation are common, but some problems are associated with them. Electrochemical method as one of the method of surface modification of commercially available activated carbon can be applied. The result is better adsorption of Chromium (VI) ions. The present thesis includes various adsorption techniques. A literature review of adsorption characteristics has been included. Our project work include fabrication of an experimental setup, surface modification (oxidation at anode) in 0.5 M KCl solution at various intensity of currents, and latter comparisons of BET surface area, porosity, FTIR analysis ( for identification of changes in bonds after electrochemical oxidation) and adsorption in spectrophotometer.
Surface area, pore volume and pore size all decrease with increase in current intensity. A significant loss in porosity and decrease in pore diameter were observed and is due to blockage of pores by formation of functional groups (carboxylic acidic groups, hydroxyl groups, lactonic grops, phenolic group) and aggregation of humic substances. As the intensity of oxidation is increased by increasing the intensity of source current the amount of adsorption also increases. Also it is observed that if the intensity of current is increased from 0.1 Amp to 2.1 Amp, the amount of adsorption increases. But as the current approaches to 2.1 Amp the adsorption amount doesn’t change significantly. Sample oxidized at 2.1 ampere was analyzed in FTIR. In the FTIR spectra it is revealed that in some ranges dip in transmittance was observed. Suitable reasons were found out. This process of activation can be suitably applied for activation of carbon.