Fabrication and characterization of electrospun cellulose acetate/graphene oxide/sodium dodecyl sulphate nanofiber membrane for phosphate ion removal

Abstract

Excessive amounts of nutrient content such as phosphorus can pollute the river, harm the ecosystem, and if the issue persists, even contribute to eutrophication. It is essential to monitor and control the concentration of phosphorus elements (< 5mg/L) for sustaining good water quality and reducing water pollution of natural water. Hence, the main idea of this research is to fabricate an adsorbent based on cellulose named cellulose acetate/graphene oxide/sodium dodecyl sulphate (CA/GO/SDS) through hydrogen bonding to adsorb phosphate ions from aqueous solution. A 13% (w/v) CA solution and a 13% (v/v) GO/SDS solution were prepared using a binary solvent system acetone:N-N dimetylacetamide (Ac:DMAc) with a ratio of 2:1. The mixture of the two solutions was electrospun in a fume hood to produce an electrospun CA/GO/SDS nanofiber membrane. Based on the characterization of electrospun CA/GO/SDS nanofiber membrane, it was proven that GO/SDS were successfully incorporated onto the CA as demonstrated by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). In a Field Emission Scanning Electron Microscopy (FESEM), the electrospun CA nanofiber membrane is pure white, while the electrospun CA/GO/SDS nanofiber membrane is not as white as that of CA since the GO content darken the membrane. A study of optimization for the adsorption process was conducted by varying the pH, immersion time and mass of membrane. In our study, hydroxyl groups on the surface of electrospun CA/GO/SDS nanofiber membrane assisted the removal of phosphate from aqueous solution through ligand exchange mechanism between the hydroxyl group and negatively charged phosphate ions. The electrospun CA/GO/SDS nanofiber membrane exhibited excellent ion removal properties due to the hydrophilic properties as well as their smooth surface membrane. The solution reached a maximum removal efficiency of 87.1% at pH 7 since the surface charge of the membrane was negative, promoting the specific adsorption of phosphate ions to occur where phosphate ions replaced hydroxyl groups on the membrane surface. A kinetic study revealed that 180 min of immersion time could adsorb about 87.2% of phosphate onto the membrane. The maximum phosphate removal on 0.05 g electrospun CA/GO/SDS nanofiber membrane was 175.44 mg-P/g. The data showed that adsorption kinetic followed the pseudo- second-order model whereas the adsorption mechanism followed the Langmuir model.