Improving the anti-fouling property and permeate flux of hollow fiber composite nanofiltration membrane using ß-cyclodextrin.

Hollow fiber composite NF membranes with improved anti-fouling property and water flux were prepared via interfacial polymerizationand layer-by-layer method using polyethylenimine (PEI), isophthaloyl dichloride (IPC), and ß-cyclodextrin (ß-CD). The chemical structures and the morphologies of the resultant NF membranes were characterized by attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The effects of ß-CD concentration on membrane morphologies, nanofiltration performances, surface hydrophilicities and anti-fouling properties were investigated. It was found that the permeate flux increased with increasing the ß-CD concentration, and no decline of rejection was observed. The results showed that the introduction of ß-CD improved surface hydrophilicities and anti-fouling performances of composite hollow fiber NF membranes. The water contact angles decreased from 61.3° to 23° within creasing the concentration of ß-CD from 0 to 2.0 wt.%. The resultant hollow fiber composite NF membrane showed an excellent anti-fouling property with the flux recovery ratio of 97.6%, which was much better than that of the original polyamide (PA) NF membranes.

A novel positively charged composite nanofiltration membrane based on polyethyleneimine with a tunable active layer structure developed via interfacial polymerization.

A novel positively charged composite nanofiltration (NF) membrane with tunable active layer structure was successfully developed via interfacial polymerization on a polysulfone (PSF) ultrafiltration (UF) membrane surface, using polyethyleneimine (PEI) as the monomer of the aqueous phase, and a mixture of isophthaloyl dichloride (IPC) and tri-mesoyl chloride (TMC) as the monomer of the organic phase. Interestingly, a synergetic effect of the mass ratio of IPC and TMC was observed on the pore size and the structure of the active layer of the resultant polyamide (PA)/polysulfone (PSF) composite NF membrane. The rejection (R) to the inorganic electrolytes increased with the mass ratio of IPC to TMC, while the permeate flux (F) escalated up to a 1 : 1 mixing ratio of IPC to TMC and dropped at higher mixing ratios. The rejection to different inorganic electrolytes decreased in the order of ZnCl2, MgCl2, CaCl2, CuCl2, MgSO4, NaCl, and Na2SO4. At ambient temperature and 0.4 MPa, the optimized membrane demonstrated R and F to 1 g L-1 MgCl2 aqueous solution as 98.1% and 27.6 L m-2 h-1, respectively. Its rejection to various dyes reduced significantly in the order of cationic red X-GTL (100%), rhodamine B (94.2%), cationic gold yellow X-GL (93.5%), and brilliant blue KN-R (43.9%), in agreement with the decrease in the molecular weight (M w) and the overall charges of the dye.

Preparation and characterization of a novel positively charged composite hollow fiber nanofiltration membrane based on chitosan lactate.

A positively charged composite hollow fiber nanofiltration (NF) membrane was prepared via interfacial polymerization (IP) between chitosan lactate (CL) and trimesoyl chloride (TMC) on a polyether sulfone (PES) hollow fiber ultrafiltration (UF) membrane. The chemical structure and the morphologies of the resultant NF membranes were characterized with attenuated total reflectance-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM). The rejection of NF membrane for different inorganic salt aqueous solutions followed the order: MgCl2 > ZnCl2 > MgSO4 > NaCl > Na2SO4. It suggested that this novel kind of composite hollow fiber NF membrane is positively charged. The molecular weight cut-off (MWCO) was obtained through the rejection of polyethylene glycol (PEG) solutions with different molecular weights (M w). The effect of monomer concentrations, the interfacial polymerization time, and the curing temperature, were investigated, respectively. The rejection and the permeate flux of the resultant composite hollow fiber CL membrane fabricated under the optimal conditions towards a MgCl2 solution of 1000 ppm were 95.1% and 10.3 L m-2 h-1, respectively, at 0.4 MPa and 25 °C. Moreover, the effects of operation conditions on the rejection performance of the composite hollow fiber NF membrane were investigated. It suggested that this novel kind of hollow fiber composite nanofiltration membrane based on CL have excellent stability in rejection performances to salt solutions.

A pH-stable positively charged composite nanofiltration membrane with excellent rejection performance.

A novel kind of pH-stable positively charged composite nanofiltration (NF) membrane with excellent rejection performance was developed via interfacial polymerization on the surface of a polysulfone (PSF) ultrafiltration (UF) membrane, using a mixture of polyethyleneimine (PEI) and piperazine (PIP) as the monomers of the aqueous phase, and cyanuric chloride (CC) as the monomer of the organic phase. The strong electron withdrawing and steric hindrance effects of the chloride group in the molecules of CC could protect the amido bond from the attack of hydrogen ions (H+) or hydroxyl ions (OH-) under acidic or alkaline conditions, thus the resultant polyamide composite membranes could be stable in acidic or alkali aqueous solution. A more compact PA active layer could be developed via mixing PIP into the PEI aqueous solution, where the PIP molecules could fill the pores of the polymer networks. There was no obvious change in the surface morphologies, the chemical structures, and the rejection performances after immersing the resultant polyamine composite NF membranes in the strong acidic solution (pH 1) and the strong alkaline solution (pH 13) for 30 days, respectively. The rejection performances of this kind of polyamine composite NF membranes could be adjusted through adjusting the mass ratio of PEI to PIP in the aqueous phase.

Microwave-Ultrasonic Synergistically Assisted Synthesis of ZnO Coated Cotton Fabrics with an Enhanced Antibacterial Activity and Stability.

ZnO nanoparticle (NP) coated cotton fabrics were prepared via a facile, time-saving, and cost-effective microwave-ultrasonic synergistic method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and inductively coupled plasma (ICP), which demonstrated that uniform ZnO NPs with an average diameter of 34 nm were intensely coated on the cotton fabrics. Compared with the samples prepared by the single microwave or ultrasonic method, the as-prepared samples displayed preferable and durable antibacterial activity against Staphylococcus aureus and Escherichia coli. The effects of the samples on inactivating microbial cells were also investigated by atomic force microscopy (AFM). It was found that the size and content of ZnO NPs coated on the cotton fabrics were dependent on the concentration of Zn2+ and microwave-ultrasonic reaction time, which also had a significant influence on the antibacterial activity of the cotton fabrics. In view of the antibacterial activity and synthesis time, the best experimental parameters were obtained. This simple, efficient, and environmentally friendly one-pot synthesis method may have great potential in scale-up production of an antibacterial textile.