Taguchi Optimization of Adsorptive Removal of 4-Nonlyphenol Pollutant Using Chitosan-Magnetic Composites: A Study of Kinetics, Isotherms, and Thermodynamics

Abstract

Industrial wastewater often contains 4-nonylphenol (4-NP), a persistent and harmful pollutant that poses significant risks to aquatic ecosystems and human health. Addressing this issue, this study focuses on the synthesis and optimization of superparamagnetic chitosan-coated magnetic composites (Cs–Fe₃O₄) as an efficient adsorbent for 4-NP removal from water. Among the tested formulations, the 1:2 Cs–Fe₃O₄ composite exhibited superior magnetic properties, larger surface area, and higher adsorption capacity compared to the 1:1 ratio, resulting in enhanced removal efficiency. Its superparamagnetic behavior enables easy separation and reusability, maintaining over 80% efficiency after five adsorption–desorption cycles. The Taguchi method identified optimal removal conditions─pH 8, a 10 min contact time, and a dosage of 0.5 mg/mL─achieving nearly 100% removal efficiency. Kinetic analysis revealed that the adsorption process followed pseudo-second-order behavior, while isotherm studies confirmed Langmuir monolayer adsorption with a maximum capacity (q_max) of 168.28 mg/g. Thermodynamic analysis demonstrated the exothermic and spontaneous nature of the process, making Cs–Fe₃O₄ a highly effective and sustainable solution for wastewater treatment.