Adsorptive removal of malachite green using fox nutshell activated carbon: Adsorption isotherms and kinetic study

Abstract

Over the past few years, environmental concerns regarding dye contamination have grown. Removing dye from wastewater from industry is crucial for environmental sustainability. Fox nutshell, an agricultural byproduct, is widely available in India. Its fibrous texture and high cellulose, hemicellulose, and lignin content make it ideal for dye adsorption. By zinc chloride activation followed by carbonization at 600 ℃, fox nutshell has been converted into low-cost fox nutshell activated carbon (FNAC). Its ability to adsorb malachite green (MG) from aquatic solutions is investigated. A porous framework with 2408.9 m²/g surface area and 2.51 nm average pore diameter is discovered in the FNAC using SEM, and BET investigations. FTIR analysis shows the presence of the –COOH, C=C, C=O, and –OH, functional groups on the surface of FNAC. The adsorption system adhered to a pseudo-second-order kinetic model, with the equilibrium time being determined at 90 min. The Langmuir model accurately simulated the adsorption isotherms. The optimum pH for MG (500 mg/L) adsorption onto FNAC (0.08 gm/100 mL) was 6.5, with an adsorption capacity of 523.3 mg/g at 298 K. Negative ΔG° and ΔH° indicate spontaneous MG adsorption onto FNAC, decreasing with temperature. π–π interactions, electrostatic attractions, and hydrogen bonding amongst the FNAC functional groups and the MG lead to the potential adsorption of MG.