Synthesis of polyethylene terephthalate/multi-walled carbon nanotubes adsorbent for methylene blue adsorption

Dye pollution is a typical undesirable environmental problem and requires effective solutions. This study aims to synthesize polyethylene terephthalate (PET) and polyethylene terephthalate/multi-walled carbon nanotube (PET/MWCNT) to adsorb methylene blue (MB). Both adsorbents are synthesized via the phase inversion method. It was found that the optimal contact time for the adsorption was 2880 min. At the initial concentration of 6 mg/L, PET/MWCNTs produced higher MB uptakes and percentage removal of 51.53% and 0.3162 mg/g, respectively, as compared to PET with 23.05 and 0.1421 mg/g, respectively. The adsorption capacity for both adsorbents decreased, while the MB dye removal percentage increased with increasing adsorbent dosage. When the initial concentration rose from 2 to 10 mg/L, the adsorption capacity increased but the removal percentage decreased for both adsorbents. The data obtained were well-fitted with the Langmuir (Type II) adsorption isotherm model with monolayer adsorption capacity, Q(m), of 0.2215 and 0.7264 mg/g for MB-PET and MB-PET/MWCNTs systems, respectively. The Langmuir dimensionless factor, R-L, values were in the range of 0 to 1 at all concentrations studied, which signified a favorable adsorption. In kinetic study, both the linear and nonlinear methods were conducted, and their results were tested with the F-test. The F-test divulged that the F-value obtained for all kinetic models studied (both linear and nonlinear methods) was greater than their respective F critical value, therefore, rejecting the null hypothesis. For all the systems studied, the P values obtained were below 0.05, which indicated a significant result of the F-test.