Efficiency of chitosan nanoparticle with polyaluminum chloride in dye removal from aqueous solutions: Optimization through response surface methodology (RSM) and central composite design (CCD).

According to the widespread use of polyaluminum chloride (PAC) in wastewater treatment and residual aluminum left in treated water, there is an urgent need to use environmentally friendly natural coagulants with conventional chemical coagulants to reduce their consumption. In this investigation, chitosan (CS) nanoparticles prepared as natural coagulant by ion gelation were applied to remove anionic dyes from aqueous solutions. For the characterization of the synthesized CS nanoparticles, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and zeta analyzer were used. The effects of different parameters, including pH, initial concentration of dye in addition to CS nanoparticles, and PAC dosages on adsorption efficiency were studied via response surface methodology (RSM) to determine the optimum conditions for maximum color removal. Results of the tests indicate that the use of CS nanoparticles and PAC with an interval of 30 s effectively increases the efficiency of color removal. The usage of PAC (80 mg/L) and CS nanoparticles (150 mL/L) at pH = 6.6 reaches the maximum color removal efficiency of 92 %. Accordingly, the use of CS nanoparticles as coagulant aid reduced the amount of needed PAC and enhanced the color removal efficiency. Furthermore, the exclusive effect of CS nanoparticles in the adsorption of dye revealed that the adsorption followed the Langmuir type II model, with an adsorption capacity of 1100 mg/g. The resulting data from the kinetic study indicated that the pseudo-second-order type II model was the most suitable model to describe the adsorption process of dye on CS nanoparticles. Based on the results, the CS nanoparticles have adequate potential to reduce the amount of needed PAC dosage for the treatment of water contaminated with anionic dyes.