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

Background: industrial effluents the major contaminants of the environment and colored wastewaters from the textile industries are the main sources of environmental pollution. objectives: 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. materials and methods: 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. results: 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. conclusions: 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.