High efficiency removal of methylene blue using SDS surface-modified ZnFe2O4 nanoparticles.

Recent studies have shown that hazardous organic dye substances can be removed from aqueous solutions by spinel ferrite nanomaterials. We found that Sodium Dodecyl Sulfonate (SDS) surface-modified mesoporous ZnFe2O4 nanoparticles (10-50nm) have a remarkably high maximum adsorptive capacity (∼699.30mg/g) for aqueous Methylene Blue (MB) removal at T of 288K and pH of 12. Unmodified ZnFe2O4 nanoparticles suffer from particle agglomeration, which reduces surface area, thus reducing their adsorptive capacity. Here it is shown that when modified with SDS, the specific surface area increased by ∼34%. It is also shown that the anionic SDS surfactant significantly increased the electrostatic attraction to the cationic MB compound. Moreover, it was found that adsorption of MB positively correlated with the aqueous solution's pH, which is attributed to a stronger negative charge on the SDS modified ZnFe2O4 surface at high pHs. The SDS-modified ZnFe2O4 adsorption of MB fitted well with the Langmuir adsorption isotherm model, and kinetic data fitted into a pseudo-second-order model. Thermodynamic parameters indicated that the adsorption was spontaneous and exothermic in nature, and physisorption dominated the adsorption of MB. The findings of this study demonstrate the potential for enhanced removal of MB contamination from aqueous solutions by SDS-modified ZnFe2O4 nanoparticles and, therefore, the potential for them to remove cationic organic dye from wastewater.