Background and purpose: Dyes in textile wastewater are amongst the main sources of environmental pollutants that are harmful for environment and human health. This study was designed for experimental evaluation of Reactive Blue 19 absorption from aqueous solutions by dried powder, modified powder, and modified carbon derived from Azolla aquatic plant carbon filiculoides, as a low cost adsorbent.

Materials and methods: In this experimental laboratorial study the effects of various parameters (initial dye concentration, contact time, pH and, amount of adsorbent (on the dye removal efficiency was investigated. Then the isotherm, kinetic, and thermodynamic equations were done. Measuring the amount of dye concentration was determined using a spectrophotometer at a wavelength of nm 594. Adsorbent characteristics were analyzed using SEM, FTIR, and BET techniques. Statistical analysis was done by Excel software.

Results: The highest absorption capacity were 4.83 mg/g by modified powder, 4.55 mg/g by dried powder, and 4.15 mg/g by modified carbon which were observed in optimum conditions: pH=2, equilibrium time of 60 min, 10 g/L of adsorbent, and initial dye concentration of 5 mg/l. The absorption efficiency of Azolla filiculoides increased by increasing the adsorbent dose and contact time, and decreasing the initial concentration of dye. It was found that the adsorption process followed Lungmuir isotherm and the kinetic model of pseudo second-order. The maximum absorbance of dye occurred by modified powder of Azolla filiculoides.

Conclusion: According to our results, adsorption process by Azolla aquatic plant is an efficient and affordable method for removal of dyes from textile industry wastewater.