Selective Removal of Reactive Orange 16 via Adsorption onto Activated Alumina, and Its Application to Textile Wastewater

This study demonstrates the sorptive removal of reactive orange 16 (RO-16), a textile dye from water, as well as, from a local textile industry via activated alumina-based batch technique. The adsorption of the dye was pH-dependent within the range of 2.49-12.21. Thermodynamic parameters such as increment H-o, increment S-o and increment G(o) were obtained from Van't Hoff equation applied to the obtained data at temperature 303, 323, 333, and 343 K. Further, the adsorption data were applied to the well-known Langmuir isotherm model, and the competitive sorption of RO-16 was studied in the presence of other commonly used reactive dyes (used in textile dyeing process), namely: Remazol brilliant blue R, reactive black 5, and reactive red 120. Effect of various chemicals used in the textile dyeing process such as acetic acid, formic acid, urea, sodium chloride, sodium nitrate, sodium sulfate, sodium phosphate, and sodium carbonate on the adsorption of RO-16 was studied in the concentration range of 500-5000 mg.L-1. Briefly, RO-16 removal was not affected by the urea, and formic acid addition; however, 3000 mg.L-1 of acetic acid showed up to 30% decrease in RO-16 removal. Chloride and nitrate did not affect RO-16 removal; nevertheless, carbonate, sulfate, and phosphate prominently decreased the adsorption efficiency at > 1000 mg.L-1 concentration. Increase in temperature from 303 to 353 K, and therefore the negative Delta S-o observed during all batches, manifests that the proposed adsorption process is exothermic. The optimized adsorption conditions represented 98.54% RO-16 removal upon mixing with real wastewater from a local textile industry.