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Heavy metals are well-known pollutant in the water body, which can threaten our health in various ways. Since size exclusion and electrostatic repulsion play a significant role in heavy metals removal for membrane technology, hereon, a positively charged nanofiltration membrane with a dense polyamide (PA) layer and a surfactant functionalized layer (SFL) was successfully developed. The optimization of the PA layer was achieved by adjusting the concentration of piperazine (PIP) and trimesoyl chloride (TMC) during interfacial polymerization and the thin film composite (TFC) membrane formed by 0.4% (w/v) PIP and 0.01% (w/v) TMC was selected for further study due to its gratifying performance. Then, the membrane was developed by attaching surfactants in which cetyl trimethyl ammonium bromide (CTAB) endowed a superior positively charged surface whereas sodium dodecyl sulfate (SDS) intensified negative charge compared to the original membranes. Furthermore, the SFL attached membrane was successfully obtained by attaching CTAB with various concentration and grafting time. The feed concentration of all metal ions and salts adopted for evaluating NF performances were 500 mg‧L−1. The best performance showed a high water permeability of 21.5 ± 0.6 L‧m−2‧h−1‧bar−1 and 96.6 ± 1.4% rejection for MgCl 2. Overall, the as-developed SFL attached membrane has found its potential application in heavy metal removal in which the separation efficiency was over 98% against Zn2+, Ni2+, 96%–98% against Cu2+, >94% against Ca2+ and >85% against Pb2+ with a high efficiency of water reclamation simultaneously. [Display omitted] • Positively charged NF membrane was developed through surfactant post-treatment. • IP built dense PA layer was optimized by monomers concentration adjustment. • CTAB and SDS endowed superior positively and negatively charged surfaces. • The surfactant layer offers a superior NF performance. • CTAB attached TFC membrane owns excellent heavy metals removal ability and stability. [ABSTRACT FROM AUTHOR]

Heavy metals are well-known pollutant in the water body, which can threaten our health in various ways. Since size exclusion and electrostatic repulsion play a significant role in heavy metals removal for membrane technology, hereon, a positively charged nanofiltration membrane with a dense polyamide (PA) layer and a surfactant functionalized layer (SFL) was successfully developed. The optimization of the PA layer was achieved by adjusting the concentration of piperazine (PIP) and trimesoyl chloride (TMC) during interfacial polymerization and the thin film composite (TFC) membrane formed by 0.4% (w/v) PIP and 0.01% (w/v) TMC was selected for further study due to its gratifying performance. Then, the membrane was developed by attaching surfactants in which cetyl trimethyl ammonium bromide (CTAB) endowed a superior positively charged surface whereas sodium dodecyl sulfate (SDS) intensified negative charge compared to the original membranes. Furthermore, the SFL attached membrane was successfully obtained by attaching CTAB with various concentration and grafting time. The feed concentration of all metal ions and salts adopted for evaluating NF performances were 500 mg‧L−1. The best performance showed a high water permeability of 21.5 ± 0.6 L‧m−2‧h−1‧bar−1 and 96.6 ± 1.4% rejection for MgCl 2. Overall, the as-developed SFL attached membrane has found its potential application in heavy metal removal in which the separation efficiency was over 98% against Zn2+, Ni2+, 96%–98% against Cu2+, >94% against Ca2+ and >85% against Pb2+ with a high efficiency of water reclamation simultaneously. [Display omitted] • Positively charged NF membrane was developed through surfactant post-treatment. • IP built dense PA layer was optimized by monomers concentration adjustment. • CTAB and SDS endowed superior positively and negatively charged surfaces. • The surfactant layer offers a superior NF performance. • CTAB attached TFC membrane owns excellent heavy metals removal ability and stability. [ABSTRACT FROM AUTHOR]

Compared with traditional methods for elaborately tailoring the active layer of thin-film composite (TFC) membranes, this study focused on building novel substrates for potential applications in developing organic solvent nanofiltration (OSN) membranes. One kind of "three-parts" hierarchically structured interface with nanospheres and macro surface pores was successfully prepared via Michael addition and Schiff's base (M&S) reactions between N-(2-aminoethyl)-3-aminopropyl triethoxysilane (NAE-A) and glycerite (a natural polyphenol) in the aramid substrate. The thickness was reduced to sub10 μ m with the aid of the high-speed spin coating process coupling nonsolvent-induced phase separation (HSSC-co-NIPS) method. The composition characterization results demonstrated the introduction of glycerite, and the reactions occurred in/on the substrate. Scanning electron microscopy (SEM) images clearly showed that the sub10 μ m substrate contained a "three-level" hierarchically structured interface that included: (1) a "stalk-like" structure; (2) glycerite-NAE-A silane (GNAS) nanospheres; and (3) the substrate surface. These phenomena also resulted in better surface hydrophilicity. All types of organic solvents, including harsh solvents, such as tetrahydrofuran (THF) and N,N-dimethylformamide (DMF), had stable permeability within the substrate, as did apolar n -hexane and isopar™ G. Therefore, the as-prepared TFC OSN membrane, which had an extremely short polymerization time, retained broad-spectrum solvent stability and had the highest solvent permeance in acetonitrile (24.5 ± 0.4 L m−2 h−1·bar−1). In addition, the resultant TFC membrane almost completely rejected the popular macrolide antibiotic azithromycin (AZM, 748.98 g mol−1) in ethanol, which is used to treat COVID-19. Image 1 • Sub10 μm macroporous substrates were prepared via the HSSC-co-NIPS method. • The natural polyphenol glycerite and NAE-A were adopted first in membrane development. • The "three-parts" hierarchically structured interface could be distinctly observed. • Short polymerization (20 s) time offered excellent performance. • AZM could be almost completely purified and concentrated in EtOH with the membrane. [ABSTRACT FROM AUTHOR]

A green method for safety drinking water production was proposed in this study by the development of a positively charged nanofiltration (PNF) membrane composed of two different functional layers. Glycosyl layer was fabricated through interfacial polymerization in which the performances of sucrose doped NF membrane was superior to the glucose and raffinose doped membranes, which were further enhanced by alkali treatment. Sucrose (0.8 wt%) and NaOH (0.05 mol‧L−1) benefit the formation of higher porosity and better hydrophilicity and offer a high pure water flux (13.5 L m−2 h−1·bar−1) and Na 2 SO 4 rejection (99.3%). Then, the PNF membrane was acquired by coating polyethyleneimine (PEI) on the sucrose-polyamide layer. The concentration of PEI and grafting time were both studied and the optimal membrane showed an excellent performance for heavy metals removal. The as-developed membrane has found its potential application in drinking water purification which gave 90% rejection for heavy metals and the permeance reached to 7.4 L m−2 h−1·bar−1. With the proposed method, the trace elements were retained partially which was beneficial to the human body and the toxic metals were kept within the limits. Image 1 • Positive charged NF membrane with dual functional layers was proposed. • Glucose, sucrose and raffinose were used to form negatively charged layer. • Sucrose and NaOH offer higher porosity, better hydrophilicity and separation ability. • PEI coated TFC membrane has excellent heavy metals removal ability and stability. • The positively charged membrane exhibited well in drinking water purification. [ABSTRACT FROM AUTHOR]

Active layers with outstanding organic solvent nanofiltration (OSN) performances were designed novelly by adopting host-guest (HG) interaction to realize adamantane structure immobilization. During the fabrication process, β -cyclodextrin (β -CD) served as the "host" while adamantylamine/adamantanemethylamine (AMA/AMmA) worked as the "guest". Stechiometrical experiment results demonstrated that one half molar ratio of the "guest" to the "host" molecular (1.0%, w/v) led to the best OSN performance. The successful immobilization of adamantane structure was verified by XPS , FT-IR and EDX results, and the adamantane immobilized membrane showed weakened "nodule-like" pattern and reduced surface roughness values compared with the control membrane. Acetone, for the first time, was proposed as the activation solvent for enhancement of OSN performance. After acetone activation, the morphology and topography of the adamantane immobilized membranes seldom changed but their pure methanol (MeOH) flux were quintupled (29.0 ± 2.6 L m−2 h−1) and the rose bengal (RB) removed from MeOH reached to 98.2 ± 0.1%. Those HG complexes also resulted in the reduction of molecular weight cut-off (MWCO) values from 466.6 Da to 436.9 and 428.4 Da of PCA10 1/2 + and PCAm10 1/2 +, respectively. Besides, the PCAm10 1/2 + demonstrated excellent OSN performances in the long-term operation of active pharmaceutical ingredients (APIs) concentration of clarithromycin (CLA)/acetone. Novel designed active layer immobilized adamantane structure with outstanding stability and membrane performances for organic solvennt nanofiltration (OSN). Image 1 • Host-guest chemistry was firstly utilized in OSN membrane development. • Adamantane structure was successfully immobilized into the active layer. • Activation of the OSN membrane using pure acetone was firstly proposed. • The mechanism of experimental errors of MWCO values was illuminated. • Outstanding performance in the potential application of API concentration was made. [ABSTRACT FROM AUTHOR]