Abstract
Water pollution by direct discharge of textile industry waste effluents, agricultural runoffs, industrial and domestic sewage to drinking water sources is becoming serious environmental problem that causes various health problems for both terrestrial and aquatic life. Among various chemical pollutants, organic dyes are one of the major constituents of industrial discharges of effluents. Adsorption technology is an excellent treatment method of the removal and remediation of organic dyes. This is due to its economically efficiency and applicability of removing dye even at low concentrations. The adsorption of dyes onto various adsorbent have been found to be promising in water re-use. This is because of their capabilities for adsorbing specific or a broad range of pollutants efficiently. However, the synthesis of some adsorbents is considered expensive. Most researchers have used various waste materials as adosrbents, and fly ash (FA) has stand out as one of the low-cost industrial wastes and highly efficient materials for water remediation due to its attractive features such as high porosity and high surface area. In this study raw fly ash was modified and used for the adsorption of rhodamine 6G and methylene blue dyes. Fly ash was treated with sodium hydroxide to produce microporous adsorbent to remove dyes from wastewater. The optimum dye was adsorbed from wastewater onto 91 mg of modified fly ash at pH 6. The grinding of fly ash particles to less than 45m was essential for increasing its surface area. Less amount of modified fly ash (91 mg) is required to adsorb up to 97% dyes after 40 minutes of sonication whereas the amount of the raw fly ash required under the same conditions is 5000 mg. The application of isotherms and kinetic models indicated that the modified fly ash has high adsorption capacity and high removal efficiency of methylene blue under optimized conditions as the pseudo-second order experimental adsorption capacity (168 mg g−1) was higher than the theoretical estimated adsorption capacity of 102 mg g−1. Similarly, the pseudo-second order experimental adsorption capacity (130 mg g−1) of Rhodamine 6G was higher than that the theoretical estimated adsorption capacity of 93.7 mg g−1. In conclusion, the use of modified fly ash is feasible and cost-effective adsorbent of dye removal from wastewater due to its high adsorption capacity. Therefore, the application of modified fly ash for dye removal is a new development that will minimize dye pollution.
M.Sc. (Chemistry)