adsorption of malachite green dye from aqueous solutions using roots of azolla filiculoides

pollution of water resources by various pollutants is nowadays a global environmental issue. among the different type of water pollutants, dye represents a major polluting group. in this study, azolla filiculides roots have been used for adsorption of malachite green (mg), a cationic dyed from aqueous solution. in this study, effects of operating parameters such as initial concentration of dye (5-30 mg/l), contact time (5-120 min), adsorbent dosage (0.05- 0.5) and ph (6-11) in the batch system investigated. the adsorption process data successfully were described by langmuir, freundlich, temkin and bet isotherms. the kinetics of the adsorption data were analyzed using 3 kinetic models such as pseudo second- order, intra-particle diffusion and elovich to understand the adsorption behavior of malachite green onto azolla filiculoides roots. the result showed the removal of mg was increased by increasing contact time and adsorbent dose, and ph. according to the analysis of the different kinetic models for adsorption of mg on azolla filiculoides roots follows of pseudo second – order kinetic. the temkin model described the adsorption result very well. this study indicated can be used as an effective and inexpensive adsorbent to removal of malachite green from aqueous solution. the positive value of change in enthalpy shows that the adsorption mg dye onto azolla filiculoides roots is endothermic. furthermore, the negative value of indicated that the adsorption mg dye was thermodynamically spontaneous.