Removal of methyl orange from aqueous solution by Azolla filicoloides: Synthesis of Fe3O4 nano-particles and its surface modification by the extracted pectin of Azolla

The modified Fe3O4 nano-particles with the extracted pectin from the cell wall of Azolla filicoloides (FN-EP) can remove methyl orange as a water-soluble azo dye from waste water better than Azolla and the extracted pectin from Azolla (EPA), alone. It could be due to more crowding the main functional groups of uptake after binding pectin with nano-particles. Thermodynamic studies showed that adsorption equilibrium constant (KL) and maximum adsorption capacities (Qmax) were increased with decreasing temperature (exothermic). The maximum uptake capacity (Qmax) of dye by FN-EP in a batch reactor was 0.533, 0.498 and 0.446 mmol/g at 5, 25 and 50 °C, respectively. The enthalpy change (ΔH) and entropy change (ΔS) were −15.31 kJ/mol and −0.02434 kJ/mol K, respectively.