Advance modification of polyacrylonitrile nanofibers for enhanced removal of hexavalent chromium from water

Abstract

Hexavalent chromium [Cr(VI)] is a known carcinogenic and mutagenic heavy metal. Its level in drinking water is regulated worldwide to protect public health. This study presents a novel chemical method to modify the polyacrylonitrile (PAN) nanofibers for efficient Cr(VI) removal from water. The PAN nanofibers with an average diameter of 165 nm are produced using the electrospinning technique. Through a 2-step chemical modification process, the amidine polyacrylonitrile (APAN) nanofibers are synthesized by the conversion of nitrile groups [ C N] in PAN nanofibers into amidines [ C(N═NH)(NH 2 )]. The attenuated total reflectance Fourier transform (ATR-FTIR) spectroscopy revealed the successful conversion of nitrile groups into amidoximes, resulting in amidoximated polyacrylonitrile nanofibers, and subsequent conversion into amidine functional groups, forming the APAN nanofibers. Greater concentration of hydroxylamine hydrochloride, increased reaction time and temperature yielded higher conversion of nitrile groups into amidoximes to a maximum of 37%. The Cr(VI) uptake by APAN nanofibers was found as a multilayer adsorption process modeled by Freundlich isotherm. The maximum Langmuir Cr(VI) adsorption capacity for APAN nanofibers was found as 225 mg g À1 at pH = 3.0 after 4.0 h exposure duration. The regeneration study revealed the excellent reusability of APAN nanofibers after five adsorption/desorption cycles.

Improving the stability of LIBS for chromium in soil based on the model of micro-linear spectrum

“…Eqn (5) shows the functional relationship between the transmittance and signal wavelength. The effective wavelength range of the collected signal is 340-1100 nm.…”

“…The effective wavelength range of the collected signal is 340-1100 nm. Combined with the measurement conditions, the xed measurement values can be substituted into eqn (4) and (5). Therefore, the curve relationship between the total transmittance and wavelength can be obtained as shown in Fig.…”

“…[1][2][3] Chromium (Cr) is a common soil pollution element, which not only reduces chlorophyll in plants to hinder photosynthesis, but also has carcinogenicity, causing damage to human organs and DNA. [4][5][6] Therefore, the accurate measurement of the excessive Cr content in soil has always been a hot topic.…”

Enhanced the antifouling and antibacterial performance of PVC/ZnO‐CMC nanoparticles ultrafiltration membrane

“…However, PVC membrane suffers from the membrane fouling during filtration because of its intrinsic hydrophobicity, resulting in a sharp decrease in permeate flux 10 . Numerous strategies have been implemented to increase the hydrophilicity of membrane surface including surface coating, 11,12 surface grafting, 13,14 and blending technique 15,16 . Zhou et al 17 investigated the PVC/poly(vinyl chloride‐ co ‐poly(ethylene glycol) methyl ether methacrylate) (poly(VC‐ co ‐PEGMA)) blending membrane and found that the coverage of PEGMA component on the membrane surface increased the surface pore sizes, hydrophilicity and antifouling properties.…”

“…10 Numerous strategies have been implemented to increase the hydrophilicity of membrane surface including surface coating, 11,12 surface grafting, 13,14 and blending technique. 15,16 Zhou et al 17 investigated the PVC/poly(vinyl chloride-co-poly(ethylene glycol) methyl ether methacrylate) (poly(VC-co-PEGMA)) blending membrane and found that the coverage of PEGMA component on the membrane surface increased the surface pore sizes, hydrophilicity and antifouling properties. Liu et al 18 demonstrated a polyamide thin-film composite membrane with highly antifouling properties.…”