Removal of methyl violet and copper from aqueous solutions using functionalized multi-walled carbon nanotubes

In this study, the removal of methyl violet and copper, which are specific pollutants, was aimed by using MWCNT-COOH and MWCNT-OH adsorbents from multi-walled carbon nanotubes. The properties of MWCNT-COOH and MWCNT-OH were determined by FTIR, SEM, BET analyses. Isotherm, kinetic and optimisation studies of methyl violet and copper adsorption with MWCNT-COOH and MWCNT-OH were carried out. Langmuir, Freundlich and Temkin models were tested in isotherm studies and the results for methyl violet and copper were found to be compatible with Langmuir isotherm. In adsorption kinetics studies, pseudo-first order, second order, pseudo-second order, Elovich and Intraparticle diffusion kinetics models were tested and the results for both pollutants were compatible with pseudo-second order. Central Composite Design of Response Surface Method and Artificial Neural Networks were used separately for optimisation and modelling. In the modelling studies, equations giving the removal efficiency and adsorbent capacity were derived, ANOVA analyses showing the effect of the parameters were performed and graphs showing the binary interactions of the parameters were obtained. In addition, the optimum conditions for the process were determined by using these models. In the optimisation with RSM, 99% and 97% removal efficiency; 259.5 mg/g and 21.68 mg/g maximum adsorption capacity values were obtained for methyl violet and copper removal with MWCNT-COOH, respectively. In the removal of methyl violet and copper with MWCNT-OH, removal efficiencies of 95% and 45.1%; maximum adsorption capacity values of 176.5 mg/g and 16.7 mg/g were obtained, respectively.