Simple synthesis of NiMn2O4/CuMn2O4/chitosan nanocomposites as a novel adsorbent for methyl orange removal from water and investigation of adsorption kinetics and isotherm models

Abstract The main objective of this research is to develop an efficient nanocomposite adsorbent for the rapid removal of organic pollutants from aqueous media. For this purpose, NiMn 2 O 4 nanostructures (NMO) and NiMn 2 O 4 /CuMn 2 O 4 /chitosan nanocomposites (Ni/Cu/CS) were synthesized using Allium cepa (onion extract) and applied, for the first time, to remove methyl orange (MO) dye. The synthesized materials were characterized. Using response surface methodology (RSM), optimum adsorption conditions were pH = 3, adsorbent dose = 1.2 g/L, MO concentration = 10 mg/L, contact time = 5 min, and agitation speed = 300 rpm. Adsorption followed the Langmuir model (maximum capacity = 416.67 mg/g, KL = 0.01) and pseudo-second-order kinetics (R² = 0.9964). The outstanding and ultra-fast adsorption of Ni/Cu/CS highlights its strong potential for wastewater treatment applications.