Silk fibroin/nylon-6 blend nanofilter matrix for copper removal from aqueous solution

Abstract

Heavy metal pollution has become a serious problem for living organisms. In this study, silk fibroin (SF)/ nylon-6 nanofiber matrices were formed by electrospinning and their surface was modified with calcium phosphate (CaP) crystals to increase the affinity of divalent heavy metals. The properties of matrices were evaluated as a filter matrix for copper adsorption from aqueous solution. Atten- uated total reflectance fourier transform infrared spectros- copy (ATR-FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray pho- toelectron spectroscopy (XPS), and alizarin red staining method were used for characterization. Adsorption studies were performed by batch and continuous system. The various parameters regarding adsorption process such as pH of solution, surface area, initial copper concentration, and flow rate were optimized. Toxicity values were assessed before and after the Cu(II) adsorption studies. The resultant SF/nylon-6 nanofiber matrices indicate an excellent fibrous structure without beads (fiber diameter at 250 ± 50 nm) and modified successfully with CaP crystals. Adsorption results showed that the removal efficiency of copper could reach 32 % by continuous flow system whereas 77 % by batch system. Acute toxicity bioassays using Vibrio fischeri showed that the toxicity decreased after continuous and batch flow systems. For desorption study, different concen- trations of various desorption solutions were used and the percentage of Cu(II) desorption was determined as 11 %, approximately.