Adsorption of PFOA and PFOS on Chitosan-Carbon Nanotubes Hydrogel Beads: Parametric Optimization Using RSM

The environmental occurrence of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), particularly in potable water sources, is evidence that current wastewater treatment facilities are unable to eliminate these newly recognized environmental contaminants entirely. On the other hand, studies on parametric optimization for solid-liquid adsorption of PFOA and PFOS are scanty. As such, the present study focuses on the parametric optimization of PFOA and PFOS on chitosan-carbon nanotube hydrogel beads from aqueous solution using the central composite design in response surface methodology as the first case. The effect of solution pH (4 – 10), contact time (2 – 48 hours), adsorbate initial concentration (5-20 mg/L), and adsorbent load (0.05 – 1.5 g/L) on the uptake of PFOA and PFOS were investigated using batch adsorption studies. The experimental data were analysed using variance alongside quadratic response models, resulting in R2 values higher than 0.97 with 95% confidence. The study gave optimal conditions of pH 4, contact time of 48 hours, adsorbate concentration of 5 mg/L, adsorbent load of 1.5 g/L, and percentage removals of greater than 90% at a standard deviation of ±1% for both PFOA and PFOS. As such, the present study's findings under optimal conditions indicate that proper adjustment of operating parameters is crucial in maximizing the uptake of the model adsorbate.