Thermodynamic Analysis of Reactive Red 198 Removal from Synthetic Wastewater by Using Multiwall Carbon Nanotubes

Industrial effluents the major contaminants of the environment and colored wastewaters from the textile industries are the main sources of environmental pollution. The present study aimed to determine the appropriate MWCNTs dosage to adsorb RR-198 and identify the thermodynamic parameters such as the free energy (ΔG °), entropy (ΔS °), and enthalpy (ΔH °) changes during adsorption process at various temperatures. The present laboratory research investigated the effect of pH, adsorbent dose, temperature, initial dye concentration, and contact time on the adsorption process of RR-198 by MWCNTS. The values of thermodynamic parameters were determined to establish the adsorption mechanism. Also, the isotherm model has been investigated. The RR-198 absorption rates were 33.26 and 222.88 mg/g, respectively for 20, and 200 mg/L dye concentration, at pH of 3, 600 mg/L dose of adsorbent, and 120 minutes time. In addition, the maximum absorption was observed at 600 mg/L dose of MWCNTs. Also, the studied dye absorption isotherm was fitted Freundlich model (R2 = 0.996 at 298K) and, the maximum adsorption capacities calculated by Freundlich model was 169.73 mg/g at 298K. All ΔG ° values were negative. The values of enthalpy (ΔH °) and entropy (ΔS °) were 38.119 KJ/mol, and 134.93 KJ/mol, respectively. The study results showed that by increasing the initial dye concentration and contact time, the adsorption capacity increased, as well. Moreover, the thermodynamic parameters (ΔH °, ΔG °, and ΔS °) revealed the endothermic sorption of RR-198 onto MWCNTs.