Ultrasound-enhanced remediation of toxic dyes from wastewater by activated carbon-doped magnetic nanocomposites: analysis of real wastewater samples and surfactant effect

Abstract

Water pollution has become a worldwide threat as the natural water resources are shrinking day by day. Emergent actions are needed to conserve water stocks to fulfill the sustainable development goals. Herein, we have prepared activated carbon-doped magnetic nanocomposites (AC@CoFe₂O₄) with environment friendly approach and characterized for FTIR, XRD, SEM, EDS, BET surface area, and pH_zpc. AC@CoFe₂O₄ nanocomposite was applied for the decolorization of toxic food dyes (rhodamine B and tartrazine) from wastewater. Effect of ultrasonic waves, pH, contact time, surfactants, temperature, and analysis of real wastewater systems were studied. Adsorption isotherm, kinetics, and thermodynamics of the experiment were calculated for the present removal process. The effect of ultrasonication shows that the maximum removal percentage for RhB was found to be 92% and for tartrazine, it was found to be 86% at 60 min. Ultrasound-assisted adsorption and degradation revealed good results because of the formation of highly active ^·H and ^·OH radicals in the liquid through the decomposition of water molecules by the formation of hot spots under ultrasonic waves. Highest decolorization of 69% was obtained for RhB with anionic surfactant SDS and climax decolorization of tartrazine was acquired in case of CTAB as 60.5%. Analysis of real wastewater samples shows that the decolorization of RhB was found to be ~ 91% from well-water and ~ 95% removal of tartrazine was observed from submersible water on AC@CoFe₂O₄ nanocomposites. The decolorization best fitted (R² < 0.988) with Langmuir model and value of Langmuir climax decolorization efficiency (Q₀) was found to be 142.68 and 435.72 mg/g for RhB and tartrazine, respectively. Kinetic analysis revealed that adsorption follows pseudo-second-order equation. The dye-loaded AC@CoFe₂O₄ nanocomposites were recycled by 0.1 M HCl or NaOH and regenerated AC@CoFe₂O₄ nanocomposites were used up to five rounds with better adsorption efficiency.

Keywords: Decolorization; Magnetic nanocomposites; Real water samples; Surfactant; Ultrasound.