Yong-Jian Tang

Polypiperazine-amide Nanofiltration Membrane Modified by Different Functionalized Multiwalled Carbon Nanotubes (MWCNTs)

In this work, three modified multiwalled carbon nanotubes (MWCNTs) with carboxyl (MWCNT-COOH), hydroxyl (MWCNT-OH) and amino groups (MWCNT-NH), respectively, were added into the aqueous phase containing piperazine (PIP) to fabricate the nanocomposite nanofiltration (NF) membranes via interfacial polymerization. The influences of functional groups of MWCNTs on the performance of modified NF membrane were investigated. The MWCNTs were characterized by TEM, FT-IR and TGA; meanwhile, the properties of the membranes were evaluated by XPS, TEM, AFM and contact angle. The XPS results proved the successful incorporation of MWCNT in the active layer of modified NF membrane. When the MWCNT concentration is 0.01% (w/v), all the nanocomposite membranes possessed the optimal separation properties, among which the membrane incorporated with MWCNT-OH demonstrated the highest water flux of 41.4 L·m(-2)·h(-1) and the Na2SO4 rejection of 97.6% whereas the one with MWCNT-COOH had the relative lowest rejection of 96.6%. Furthermore, the increased hydrophilicity of functional groups in modified MWCNTs resulted in different nodular surface morphologies, thicknesses and hydrophilicities of the nanocomposite membranes. All the membranes possessed a molecular weight cutoff (MWCO) within 300 Da and good operation stability.

Fabrication and characterization of a novel nanofiltration membrane by the interfacial polymerization of 1,4-diaminocyclohexane (DCH) and trimesoyl chloride (TMC)

This study focuses on the preparation and nanofiltration properties of a novel thin-film composite polyamide membrane formed by the interfacial polymerization of 1,4-diaminocyclohexane (DCH) and trimesoyl chloride (TMC) on a porous polysulfone supporting membrane. At the same time, we found that the introduction of sodium N-cyclohexylsulfamate (SCHS) can improve to a degree the water flux and salt rejection. The active surface of the membrane was characterized by employing SEM and AFM. The performance of the nanofiltration membrane was optimized by considering the preparation conditions, including the monomer concentration, reaction time, curing conditions and SCHS concentration. The resulting NF membrane prepared under the optimum conditions exhibited a Na2SO4 rejection of 98.1% and a water flux of 44.6 L m−2 h−1 at 0.6 MPa. The pore size of the NF membrane was about 0.33–0.42 nm, which was calculated from the rejection of PEG and carbohydrates, respectively.

Novel polyamide thin-film composite nanofiltration membrane modified with poly(amidoamine) and SiO2 gel

Recently, poly(amidoamine) (PAMAM) has emerged as a novel material due to its high density of functional groups, hyper-branched structure and hydrophilic nature. PAMAM has been used as a monomer during an interfacial polymerization process for the fabrication of nanofiltration membranes. Previous work has focused on the low generation of PAMAM (G0, G1 and G2), however, the high generation of PAMAM (G4 and G5) still lacks investigation. This work focuses on the preparation of nanofiltration membranes, which are made of PAMAM–NH2 G4 and PAMAM–NH2 G5. By optimizing the concentration of PIP and SiO2 gel in the aqueous solution, the pure water flux improved by 106% while separation properties are kept at the same level. XPS, EDS, SEM, AFM and contact angle were used to characterize the NF membrane properties. The PAMAM/PIP/SiO2 membrane prepared under the optimum conditions exhibited a pure water flux of 38.5 L m−2 h−1 and Na2SO4 rejection of 92.0% under 0.6 MPa. The PAMAM/PIP/SiO2 membrane’s robust long-time running performance showed its good potential in practical applications.

Antifouling sulfonated polyamide nanofiltration hollow fiber membrane prepared with mixed diamine monomers of BDSA and PIP

A novel high-flux sulfonated polyamide nanofiltration (NF) hollow fiber membrane was made from the mixed monomers of 2,2′-benzidinedisulfonic acid (BDSA) and piperazine (PIP). By optimizing the preparation parameters (TMC concentration, reaction time and BDSA/PIP mixing ratio), the optimized NF membrane possessed a pure water permeability (PWP) of 49.1 L m−2 h−1 and a Na2SO4 rejection of 95.5% under 4 bar. The molecular weight cut off (MWCO) of the BDSA/PIP NF membrane was about 400 Da. Furthermore, in a long-term antifouling test with 0.3 g L−1 bovine serum albumin (BSA) solution, the total flux decline rate (FDR) and the flux recovery ratio (FRR) of the membrane were 16.7% and 85.7% respectively, which indicated the good antifouling properties and application prospects of the TFC NF membrane.