The Use of Selected Carbonized Agricultural Waste as a Low Cost Scrubber in Air Pollution Control

The production of activated carbon from agricultural waste is one of the mostenvironmental friendly solutions of transforming less valuable into more valuable materials and it is also a way of converting waste to wealth. Rice husks, maize cobs and coconut shells were individually used to prepare activated carbon under the same experimental conditions of 500OC carbonization temperature, impregnation ratio of 10:1 under 1hr activation time using chemical activation method with zncl₂ as the activation agent. After being subjected to carbonization and chemical activation, the farm residues were examined for their surface areas, PHs, conductivities, specific gravities, bulk densities and moisture contents. Elemental composition of each of the waste at carbonized stage, when chemically activated, when used to trap air pollutants and when reactivated were also determined. The adsorptive capacities of these activated carbons were investigated and compared by loading each of them in an adsorption column of 1.5m tall, 0.98m diameter with four openings at height 0m (input), 0.5m, 1.0m, 1.5m (output). A 0.85kva generator was connected to the column and the concentrations of some selected primary pollutants (HC, CO, CO2 NOX) were determined at the input was analyzed and compared to the concentrations at different heights in the column, as the fumes passed through. Optimization studies were also carried out to investigate the adsorptive efficacies of blends of the activated carbons, at different ratios and proportions. When the three activated carbons were mixed at same ratio and proportion, the adsorptive capacity was found to be less than when compared to the efficiencies of the individual activated carbons. Activated carbon produced from coconut shells was experimentally found to have the highest adsorptive capacity followed by that produced from maize cobs and rice husks. The adsorptive capacity was experimentally found to be dependent on adsorbate dosage, contact time and concentration of the adsorbate. CO and CO2 were found to be easily absorbed by all the three activated carbons. Some recommendations have been made.