Adsorption of methylene blue onto magnetic nanoparticles and magnetite nanoparticles coated with humic acid

Synthesis of magnetite nanoparticle (Fe3O4) and magnetite nanoparticles coated with humic acid (Fe3O4-HA) have been done and it was used to adsorp cationic dye, i.e. methylene blue (MB) in the waste water treatment. The synthesis of Fe3O4 and Fe3O4-HA were done by coprecipitation method using NH4OH as precipitating agent from a mixture of 2.78 g of salt FeSO4•7H2O; 5.41 g of salt FeCl3•6H2O; and 1 g of extracted HA. Determination of pH point of zero charge (pH PZC) has also been carried out before examining the adsorption of MB. The effect of pH, contact time, and the concentration of the MB solutions were the main examined parameters of adsorption. The results of this research showed that Fe3O4 and Fe3O4-HA have a value of pH PZC 8 and 6.47, respectively. The adsorption of MB onto both Fe3O4 and Fe3O4-HA are followed the model of kinetic adsorption of pseudo-second order and Langmuir isotherm with the value of adsorption equilibrium constant (k) and the adsorption capacity of Fe3O4 adsorbent sequently are 77,344 L mol-1 and 25,65 mg g-1, meanwhile for Fe3O4-HA are 107,304 L mol-1 and 28,81 mg g-1, respectively. This adsorption data were obtained at the condition of pH maksimum for adsorption MB at pH 10 and the equilibrium time at 200 minutes for Fe3O4, and at pH 7 and at 30 minutes for Fe3O4-HA. From those different result of adsorption data, we can conclude that Fe3O4-HA is more effective as an adsorbent of dye waste, i.e. Methylene Blue (MB).