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Experimental and Kinetic Studies on Acid Red 88 Dye (AR88) Adsorption by Azolla filiculoides

Davoud Balarak and Yousef Mahdavi

The use of Azolla filiculoides (AF) for the removal of Acid Red 88 dye (AR88) from aqueous solutions at different contact times, temperatures, pH, adsorbent doses and initial dye concentration was investigated. The extent of dye removal decreased with increasing adsorbent dosage and AR88 concentration, also increased with increasing contact time and temperature. The adsorption isotherms are described by means of the Langmuir, Freundlich, Tempkin and Sips isotherms. It was found that the Langmuir equation fit better than the other equation. Maximum adsorption capacity (qm) was calculated at different temperatures (20, 30, 40 and 50°C) 22.45, 23.95, 25.29 and 26.17 mg/g, respectively. The adsorption kinetics of Acid Red 88 could be described by the pseudo-second-order reaction model. The obtained results are: (1) high levels of color removal (>98%) were achieved with low contact times adsorbent/dye (less than 90 min contact); and (2) the whole Azolla filiculoides can be successfully used as adsorbent of AR88 in aqueous solutions. Azolla biomass, an inexpensive and easily available material, can be alternative for more costly adsorbents used for dye removal in wastewater treatment processes.