Acid dyes found in textile industrial effluents are hazardous aromatic pollutants which ionise in aqueous environments. Owing to their non-biodegradability and high aqueous solubility, conventional wastewater treatment processes are not able to remove them. Alternatively, adsorptive treatment systems are preferably employed to remove such pollutants from industrial effluents. Nevertheless, the already available adsorbents have one or more limitations such as low adsorption rate and low reusability. To address these issues, removal of two hazardous acid dyes (Acid Red 27 and Acid Orange 52) was investigated in this study using a nano _γ-Fe₂O₃ based magnetic cationic hydrogel (nFeMCH) which was synthesized through a facile method.

The sorption performance (e.g., capacity and kinetics) and...[ Read more ]

Acid dyes found in textile industrial effluents are hazardous aromatic pollutants which ionise in aqueous environments. Owing to their non-biodegradability and high aqueous solubility, conventional wastewater treatment processes are not able to remove them. Alternatively, adsorptive treatment systems are preferably employed to remove such pollutants from industrial effluents. Nevertheless, the already available adsorbents have one or more limitations such as low adsorption rate and low reusability. To address these issues, removal of two hazardous acid dyes (Acid Red 27 and Acid Orange 52) was investigated in this study using a nano _γ-Fe₂O₃ based magnetic cationic hydrogel (nFeMCH) which was synthesized through a facile method.

The sorption performance (e.g., capacity and kinetics) and solution matrix effects (e.g.,pH and co-present constituents) were investigated. To acquire a mechanistic insight, experimental data was further analyzed by employing different mathematical models such as Langmuir and Freundlich (for isotherms) and pseudo first order, pseudo second order and intraparticle diffusion model (for kinetic analyses). Furthermore, different regeneration conditions (e.g., composition, strength and amount) were tested to systematically develop a suitable regeneration strategy. Based on the findings from the regeneration study, the reusability of nFeMCH was investigated for 30 consecutive adsorption-desorption cycles.

The nFeMCH exhibited fast kinetics (99% dye removal within 5 min) and the experimental data fitted well to the pseudo second order model. The adsorption isotherm data agreed well with the Langmuir model with an estimated maximum capacity of 833 mg/g and 1430 mg/g for Acid Red 27 and Acid Orange 52, respectively. The high adsorptive performance persisted not only over a wide pH range but also over 30 consecutive rounds of adsorption-desorption. Moreover, the impregnated γ-Fe₂O₃ nanoparticles rendered the hydrogel superparamagnetic, thereby allowing its convenient magnetic separation.