Systematic Evaluation of Isotherm and Kinetic Models for Malachite Green Adsorption onto a Carbonaceous Nanocomposite

This study, equilibrium adsorption studies of malachite green (MG) solution on TiO۲ nanoparticle (NPs) loaded on f-MWCNT and the best optimum conditions such as pH, amount of adsorbent, contact time, initial dye concentration and particle size was investigated. The maximum adsorption capacity was obtained by pH ۸, adsorbent dose of ۰.۰۰۵ g, particle size = ۱۹.۹ nm, contact time of ۱۰ min, temperature of ۲۹۳K and dye concentration of ۵-۲۵ mg/L. The adsorption kinetic was found to undergo pseudo second-order. A significant amount of the dye (۹۹% for this adsorbent) was recovered by using ۱.۰ M NaOH as an eluting agent. The pseudo-second-order model best describes the adsorption kinetics, confirming physical and chemical adsorption as the dominant mechanism. The combination of high a in Elovich and high C in intraparticle diffusion implies a mixed mechanism involving surface interaction and boundary layer resistance. It showed that the MG chemisorptions mechanism was described by Langmuir-۲ model, with regression-coefficient (R²) of ۰.۹۹ and a Person's Chi-square (X²) of ۰.۰۰۲۳. Besides Langmuir-۲, Elovich, Freundlich and Tempkin models provided excellent correlations (R۲ = ۰.۹۹), implying a combination of physical and chemical adsorption on surfaces with heterogeneous energetic sites. This hybrid mechanism suggests the TiO۲/f-MWCNT composite has a structurally diverse surface with a wide energy distribution.

کلیدواژه ها:

Malachite Green ، Adsorption ، Isotherm Models ، Kinetic Models ، Carbonaceous Nanocomposite