In order for adsorption to be practically realizable in the industry, it should have a high capacity for the targeted solutes, a high rate of adsorption, and facilitate convenience of operation on a large scale. To achieve these requirements, natural materials are transformed by acid treatment, alkali treatment, carbonization (for carbonaceous materials), activation with appropriate agents (steam, hydrogen, and one more) and pelletization. Pelletization involves the blending of the activated carbon with suitable binders and extruding the resulting mass into pellets of suitable dimensions. The pellets offer a much smaller pressure drop when employed in industrial continuous bed adsorbers. There is much scope for optimization of the pelletization process as it involves competing and often contradicting factors like adsorption capacity, attrition resistance, and cost. Commercial adsorbents from different precursors along with two binders were mixed in proportions suggested by Mixture Design of Experiments and subsequently pelletized. The responses studied were ball pan hardness, n-butane gas adsorption capacity, and cost. Different and simultaneous objective functions involving combinations of maximizing ball pan hardness and hardness and minimizing cost were tried and results are presented. The benefit to cost ratio factor was introduced to grade the different proportion of pellets in different categories. Consistent trends were noted from the optimization studies. These blended pellets may be used in applications involving pollutants in gaseous and liquid streams.
Subsequent research to meet the industrial objectives will involve inorganic adsorbents. Clay materials will be suitably treated with metal cations that will form pillared structures. These will resist the inherent swelling of clay materials upon contact with water and create structures with tunable porosity. There is considerable scope for process improvement and optimization of the pillared clay synthesis process. The process may be intensified using ultrasound and microwave. We plan to optimize the process conditions for the preparation of pillared clays and use them as efficient adsorbent along with activated carbon for versatile treatment of wastewater containing both organic and inorganic pollutants.
Keywords: Versatile Treatment, Activated Carbon, Pelletization, Clay, Pillaring