Poly(vinyl alcohol)/Vitamin C-multi walled carbon nanotubes composites and their applications for removal of methylene blue: Advanced comparison between linear and nonlinear forms of adsorption isotherms and kinetics models

Abstract

The fabrication of glutaraldehyde (Gl)-crosslinked poly(vinyl alcohol) (PVA)/Vitamin C (VC)-multi walled carbon nanotubes (VC-MWCNTs) composites and their adsorption capacity for removal of methylene blue (MB) are reported. These composites were characterized with various techniques. The thermal stability of Gl-crosslinked PVA/VC-MWCNTs 3 and 5 wt% was greater than PVA owing to uniform distribution of VC-MWCNTs. The results of adsorption experiments showed that the Gl-crosslinked PVA/VC-MWCNTs 7 wt% can remove about 97 ± 3% of MB from aqueous solution after 45 min at room temperature. The up-to-date linear and nonlinear forms of two isotherms (Langmuir and Freundlich) and two kinetic models (pseudo-first-order and pseudo-second-order) were studied. The adsorption data obeyed nonlinear pseudo-first-order model and linear Freundlich isotherm. Also, the adsorbent can be reused for five times after regeneration without any loss of the efficiency (removal≈97 ± 3%). The outcomes of electrical conductivity analysis demonstrated that the fine electrical conductivity was achieved at 3 wt% of VC-MWCNTs.