Fu Liu,Bi-rong Ma,Dong Zhou,Li-Jing Zhu,Yin-Yi Fu,Li-xin Xue
A novel positively charged loose nanofiltration (NF) membrane was fabricated feasibly by UV-induced photografting polymerization of diallyl dimethyl ammonium chloride (DADMAC) on Polysulfone ultrafiltration membrane. A possible reaction mechanism was proposed that a linear chain structure and/or pyrrole like five-membered nitrogen heterocycles structure on the side chain were grafted to form the active barrier layer. NF membrane demonstrated a looser average pore size of 8.6 nm and positive charges surface. Owing to the nanoscale ultrathin nanoscale barrier layer and the combination of Donnan exclusion and steric hindrance , NF membrane exhibited good hydrophilicity , a high pure flux of 60 L/m 2 h (0.5 MPa), a good salt rejection to Mg 2+ (90.8%), Al 3+ (94.0%), Ca 2+ (91.5%), and a high dye rejection to methylene blue (99.4%) and congo red (100.0%) respectively. The salts rejection of NF membrane to different salts followed the order of AlCl 3 > CaCl 2 > MgCl 2 > NaCl > LiCl > MgSO 4 > Na 2 SO 4. NF membrane showed certain fouling resistance to seawater and BSA solution. The grafting polymerization kinetics were comprehensively investigated including irradiation time, monomer concentration and irradiation intensity. X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurement were employed to investigate membrane chemistry, morphologies, and hydrophilicity.
A series of sphere-like polyelectrolyte complexes (PECs) and their homogeneous polyelectrolyte complex membranes (HPECMs) were synthesized by using sodium carboxymethyl cellulose (CMCNa) and poly(diallyldimethylammonium chloride) (PDDA). Different compositions or ionic complexation degrees (ICD) of PECs could be characterized by FT-IR spectra. The circular dichroism spectrum (CD) and field emission scanning electron microscopy (FESEM) were employed to examine the conformation and morphology of PECs, respectively. Zeta (ζ) potential was utilized to investigate the charge density of PEC particles while the surface hydrophilicity of HPECMs was studied by using contact angle (CA) meter. When subjected to ethanol dehydration, HPECMs revealed a satisfactory pervaporation performance and desired anti-trade-off phenomenon. For HPECM 0.31 and HPECM 0.57, the permeation fluxes were 2.25 kg m −2 h −1 and 2.93 kg m −2 h −1 , and the water content in permeate reached up to 99.35 wt% and 99.38 wt%, with respect to 10 wt% water in feed under 70 °C. All the results indicated that small-sized and sphere-like PECs were truly in favor of enhancing the pervaporation performance in ethanol dehydration.
Lu Juanjuan,Liu Yuelin,Liu Xinhe,Lu Xiaoquan,Liu Xiuhui
In this article, we constructed an electrochemical sensor for highly sensitive determination of β-nicotinamide adenine dinucleotide (NADH) using the poly(diallyldimethylammonium chloride)-functionalized reduced graphene oxide nanocomposite modified electrode (PDDA-rGO/GCE). The nanocomposite was characterized by transmission electron microscopy, Fourier transform-infrared spectrometry, ultraviolet-visible absorption spectrometry, cyclic voltammetry, and electrochemical impedance spectroscopy. The experimental results demonstrated that the fabricated sensor exhibited excellent electrocatalytic activity on the oxidation of NADH with a decreased about 200 mV in overpotential and 5.0-fold increment in the oxidation peak current compared to a bare GCE. Applying cyclic voltammetry, a wide linear range from 1.0 × 10 −7 to 2.9 × 10 −3 M with low limit of detection (LOD) of 3.4 × 10 −8 M and high sensitivity of 463.3 μA mM −1 cm −2 were obtained, which was superior to other NADH electrochemical sensors reported previously. Furthermore, the fabricated NADH sensor possessed excellent selectivity, reproducibility, and stability. The oxidation mechanism of NADH at the PDDA-rGO/GCE was also discussed in detail.
A simple NADH sensing platform based on PDDA-rGO composite is constructed, which exhibits an ultra-low detection limit ( 3.4×10-8 M) towards the oxidation of NADH, and the electrochemical reaction mechanism of NADH is discussed in detail.
危险品化学品经营许可证（带存储）