Removal of Malachite Green Using Activated Carbon From Coconut Husk and Groundnut Shell: Adsorption Kinetics and Electrochemical Studies

ABSTRACT In this research work, the desorption of malachite green dye from water by means of adsorption onto NaOH‐activated carbon obtained from agricultural waste sources including coconut husks and peanut shells is examined. Scanning Electron Microscopy, X‐Ray Diffraction, and Fourier Transform Infrared Spectroscopy were applied for activated coconut husk carbon and activated groundnut shell carbon. The activated coconut husk carbon demonstrated a remarkable removal efficiency of 95.6%, whereas the activated groundnut shell carbon exhibited a removal efficiency of 92.1% at an optimal pH of 7–8, adsorbent dosage of 0.03 g, and initial dye concentration of 20 ppm. The adsorption mechanism followed the Freundlich isotherm model with an R 2 value of 0.98 and 0.99 for activated coconut husk carbon and activated groundnut shell carbon. Furthermore, electrodes for groundnut and coconut shells were made, and these were then electrochemically characterized using methods such as electrochemical impedance spectroscopy, linear sweep voltage measurement, and cyclic voltammetry. Maximum dye removal of 90% was obtained at 40 min for reaction time with an initial dye concentration of 20 ppm.