ABSTRACT
The chitosan-grafted-poly(N-vinylcaprolactam) (chitosan-g-PNVCL) nanofibers were synthesized via electrospinning method. ZIF-8 metal-organic frameworks nanoparticles were incorporated into the nanofibers for adsorption of Cr(VI), As(V) and phenol from water. The BET, FTIR, XRD and SEM analysis were carrfried out to obtain the characteristics of nanofibers. The optimum parameters of ZIF-8 content, pH, contact time, adsorbent dosage, and initial concentration of adsorbates on the Cr(VI), As(V) and phenol removal were studied. The reusability of synthesized nanofibers for five sorption-desorption cycles was also examined. The maximum experimental adsorption capacity of the chitosan-g-PNVCL/ZIF-8 nanofibers for Cr(VI), As(V) and phenol sorption were 269.2, 258.5 and 152.3 mg g-1, respectively under ZIF-8 concentration of 3 wt.%, adsorbent dosage of 0.5 g/L, pH of 3, equilibrium times of 30 min, and temperature of 25 °C. The kinetic, and isotherm parameters of adsorption process using chitosan-g-PNVCL/ZIF-8 nanofibers were evaluated. In ternary system, the central composite design was applied to investigate the interaction influence of initial concentrations of selected metal ions and phenol on the performance of nanofibrous adsorbent. The obtained results showed the high capability of nanofibers for the removal of heavy metals and organic pollutants from water.
ABSTRACT
The potential of electrospun cellulose acetate/chitosan/single walled carbon nanotubes/ferrite/titanium dioxide (CA/chitosan/SWCNT/Fe3O4/TiO2) nanofibers was investigated for the removal of Cr(VI), As(V), Methylene blue and Congo red from aqueous solutions via the adsorption and photocatalytic reduction processes. The properties of synthesized SWCNT/Fe3O4/TiO2 and fibers were characterized using TEM, SEM, FTIR, XRD, TGA and BET analysis. In adsorption process, the influence of adsorbent type including SWCNT to Fe3O4 ratio, TiO2 to SWCNT/Fe3O4 ratio and SWCNT/Fe3O4/TiO2 concentration as well as the adsorption parameters including pH, contact time, and initial concentration of adsorbates on the Cr(VI), As(V), Methylene blue and Congo red adsorption in a batch mode was investigated. The reusability of nanofibers was also investigated for five adsorption-desorption cycles. The photocatalytic reduction of Cr(VI), As(V), Methylene blue and Congo red was also investigated using various nanofibrous catalysts. The obtained results indicated that the removal of Cr(VI) and As(V) using CA/chitosan/SWCNT/Fe3O4/TiO2 nanofibrous adsorbent via adsorption process could be preferred for the lower concentrations of metal ions. The photocatalytic reduction was an effective method for the Cr(VI), As(V) removal at higher concentrations and degradation of Methylene blue and Congo red under both lower and higher concentrations of azo dyes.
