Removal of methylene blue from aqueous solution using poly(acrylic acid)/SiO2 and functionalized poly(acrylic acid)/SiO2 composite nanofibers

Abstract

In this study, poly(acrylic acid)/SiO2 (PAA/SiO2) and mercapto-functionalized poly(acrylic acid)/SiO2 (PAA/SiO2/TMPTMS) composite nanofibers were prepared through a sol-gel/electrospinning method to remove methylene blue (MB) from aqueous solution. The optimum conditions of the electrospinning process were achieved at room temperature at an applied voltage of 22 kV, a distance of the needle to the collector of 15 cm, and a flow rate of 0.005 mL/min. The presence of a characteristic peak at 2557.61 cm−1 in the FTIR spectra exhibited that the mercapto group was successfully incorporated into the PAA/SiO2 composite nanofiber. SEM-EDX, TEM, and BET analysis showed that the diameters of PAA/SiO2 and PAA/SiO2/TMPTMS were 382.5 and 246 nm, respectively, with the surface areas of PAA/SiO2 and PAA/SiO2/TMPTMS were 27.67 and 108.54 m2/g, respectively. The batch adsorption results indicated that the maximum MB adsorption capacity of PAA/SiO2 and PAA/SiO2/TMPTMS composite nanofibers was found to be 400 and 437.78 mg/g, respectively, at pH 10 for 120 min of contact time. The adsorption isotherm and kinetics data showed that MB adsorption onto both PAA/SiO2 and PAA/SiO2/TMPTMS composite nanofibers followed the Langmuir adsorption isotherm and was best described by the pseudo-second order kinetic model. Under the experimental conditions, thermodynamic parameter data indicated that the MB adsorption process onto PAA/SiO2 and PAA/SiO2/TMPTMS composite nanofibers was non-spontaneous and endothermic. Their high adsorption capacities and their ability to be reused in multiple cycles support these composite nanofibers to become a promising adsorbent to be developed for removing MB from wastewater.