Chitosan-nickel oxide composite as an efficient adsorbent for removal of Congo red from aqueous solution

The chitosan-nickel oxide (CS-NiO) composite was synthesized and characterized by XRD, FT-IR, SEM, TEM, BET, and TG-DTG. The as-prepared composite was used as an adsorbent for the removal of Congo red (CR) dye from aqueous solution. Effects of various parameters such as solution pH, adsorbent dosage, initial dye concentration, contact time, and temperature on the adsorption of CR were investigated. The adsorption kinetics was found to conform to the pseudo-second-order kinetics model with good correlation. The adsorption of CR on the CS-NiO composite followed the Langmuir model and the maximum adsorption capacity at 25 °C determined from Langmuir model was 188.68 mg/g. The thermodynamic data revealed the spontaneous and endothermic nature of the adsorption process. The CS-NiO composite adsorbent can be separated from system effectively and easily, and maintained high adsorption efficiency even after five-time recycles. The aforementioned results demonstrated that the CS-NiO composite could be used as an efficient and low-cost natural adsorbent for the removal of CR from aqueous solution.