Removal of hazardous organic pollutants using fly ash

Abstract

This study aims to achieve the highest removal efficiency of direct blue dye using a low-cost adsorbent. The adsorption of direct blue 78 dye (DB78) with commercial name (Tubantin blue GLL 300) from a synthetic wastewater using a raw coal fly ash was studied. The ability of coal fly ash (industrial by product) as cost-effective adsorbent to remove dyes from textile wastewater effluent was investigated in detail. A series of batch experiments were conducted in terms of adsorbent dose, contact time, pH, and initial concentration of dye. The raw coal fly ash was characterized by physico-chemical analysis namely; X-ray diffraction (XRD), X-ray fluorescence (XRF) and Brunauer–Emmett– Teller (BET). It was found that the major phases for coal fly ash are quartz and hematite. Loss of ignition percentage and surface area are 36% and 9.6113 m2g-1 respectively with average particles size 624 nm. The adsorption tests showed that the removal efficiency increases with increasing adsorbent dosage and contact time. Removal efficiency decreases at high initial concentration of direct blue 78 dye. The maximum capacities for dyes removal reached to 99.1% with initial concentration 10 mg/l and fly ash dose 3 g/l. Dyes removal (98.4%) was obtained using initial concentration 20 mg/l and fly ash dose 4 g/l. At higher initial concentration (30 mg/l) using fly ash dose 5 g/l, lower removal efficiency was obtained with 97.2%. The Langmuir isotherm model was shown to have a higher coefficient of determination R2 than the Freundlich isotherm model in representing the fly ash adsorption process.