Study on methylene blue adsorption using cashew nut shell-based activated carbon

Adsorption is a widely used technique for the treatment of wastewater containing dyes, which are pollutants that can have serious impacts on the aquatic ecosystems. In this work, activated carbon (AC) was prepared from cashew nut shell (CNS) and used to adsorb methylene blue (MB) from solution. The CNS AC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption isotherms. The adsorption behavior of MB on CNS AC was investigated by varying the initial solution pH, adsorbent dosage, and initial MB concentration. The results showed that the CNS AC was effective for MB removal, with an adsorption capacity of 24.8 mg/g. The adsorption nature of MB onto the CNS AC surface was explored by analyzing the experimental data using isotherm and kinetic models. The Freundlich and Dubinin-Radushkevich (D-R) isotherm models showed good agreement with the experimental adsorption equilibrium results. The mean adsorption energy was found to be 22.4 kJ/mol, indicating chemical adsorption. The adsorption of MB on the CNS AC followed pseudo-second-order kinetics. This study demonstrates the potential application of CNS AC for MB removal.