Congo Red Rejection Research Articles

Nitrogen incorporation by plasma polymerization of heptylamine on PES membrane for removal of anionic dye (Congo red)

Fouling is one of the drawbacks in membrane filtration systems, reducing the water quality and decreasing the lifespan of a membrane filtration system. In this study, we propose a surface modification on polyethersulfone (PES) membrane by using plasma polymerization with heptylamine as the precursor by varying the deposition time from 3 to 15 min to induce hydrophilic surface of the membrane without changing the bulk properties of PES membrane. Cross-flow filtration and water contact angle of the PES membrane were used to measure permeate flux and Congo red rejection. Based on permeate flux, we calculate the fouling tendencies of each membrane and the result showed that sample with 5-min deposition time produces the best permeate flux (58% increase) and the lowest fouling tendencies (65% decrease) when compared to the untreated membrane. From the EDX mapping, the deposition enables to introduce a stable nitrogen element into the membrane with the homogeneous distribution. This plasma-based post-surface modification demonstrates the encouraging potential to improve significantly the permeate flux, rejection and fouling properties compared to the untreated commercial filtration membrane.

Enhanced photocatalytic performance of polyvinylidene fluoride membrane by doped CuFe2O4 nanocrystals for water treatment

CuFe2O4 nanocrystals with the size about 60 nm were synthesized under hydrothermal conditions, and doped them into polyvinylidene fluoride (PVDF) membranes for enhancing their photocatalytic performance. The morphology, phase, and photoelectric performance of CuFe2O4/PVDF membranes were confirmed by X-ray photoelectron spectroscopic (XPS), scanning transmission microscopy (SEM), and transient photoelectrochemical analysis. As a result, the morphologies of CuFe2O4 nanocrystals could change with the concentration of NaOH solution under hydrothermal conditions. CuFe2O4 nanocrystals showed strong facet-dependent photoelectric and photocatalytic properties. PVDF membrane doped with CuFe2O4 nanocubes showed excellent photocatalytic activity of Congo red degradation (95%), and kept the good self-cleaning performance after five circles. The flux and rejection performance displayed the CuFe2O4 nanocubes/PVDF membrane kept high water flux (40 L/m2 h) and Congo red rejection (99%), and the composite membrane have good potential in water treatment applications.

Sub-10 nm Polyamide Nanofiltration Membrane for Molecular Separation.

To separate small molecules from the solvent with high permeability and selectivity, the membrane process is thought to be highly effective with much lower energy consumption when compared to the traditional thermal-based separation process. To achieve high solvent permeance, a sub-10 nm thick polyamide nanofiltration membrane was synthesized through interfacial polymerization of ethidium bromide (EtBr) and trimesoyl chloride (TMC). Thanks to the extremely low solubility of the EtBr monomer in the organic phase, the polymerization process was strictly limited at the interface of the water and hexane, leading to an ultrathin polyamide membrane with a thickness down to sub-10 nm. When used in nanofiltration, these ultrathin membranes display ultrafast water permeation of 40 liter per square meter per hour per bar (L m-2 h-1 bar-1 ), and a high Congo red rejection rate of 93 %. This work demonstrates a new route to synthesize ultrathin polyamide membranes by the traditional interfacial polymerization.

NH2-Fe3O4-regulated graphene oxide membranes with well-defined laminar nanochannels for desalination of dye solutions

Graphene oxide (GO)-based nanofiltration membranes, featuring well-ordered microscopic structure, well-defined 2D nanochannels and superior molecular sieving ability, have attracted sustained research interest in molecular and ionic separation. However, most of current GO laminar membrane have a poor water flux and high rejection of both dyes and salts, which is not suitable for the dye/salt mixture separation. Herein, we report a vacuum filtration strategy to fabricate GO/NH2-Fe3O4 nanofiltration membranes with high water flux and excellent separation performance for dye/salts mixture by introducing NH2-Fe3O4. The NH2-Fe3O4 is not only worked as the rigid spherical nanospacer to tune GO interlayer spacing but also as crosslinkers to improve the stability of GO membrane in water. FTIR, XRD, SEM, zeta potential and contact angle were applied to analyze the chemical composition and morphology of as-prepared membranes. The effect of intercalated NH2-Fe3O4 nanoparticles on overall performance of the GO/NH2-Fe3O4 membranes was systematically investigated. The resulted membrane with 8 wt% of NH2-Fe3O4 loading has high water flux of up to 78 Lm−2 h−1, which is 4.8 times higher than that of pure GO membrane. Moreover, such membrane also displays high congo red rejection (94%) and low NaCl rejection (~15%), rendering the membranes promising for dye/salt mixtures separation.

Interfacial polymerized and pore-variable covalent organic framework composite membrane for dye separation

Covalent organic frameworks (COFs) with crystalline imide structure achieved remarkable application in the field of water treatment membrane. In this work, 1,3,5-triformylphloroglucinol (Tp) and benzidine (Bd) or melamine (Me) monomers as the assemble units were firstly in-situ interfacial polymerized upon polysulfone (PSf) porous substrate to form COFs composite membrane with a thin and stable COFs selective layer. Furthermore, adding melamine monomer during interfacial polymerization between Tp and Bd monomers could further introduce a triazine ring type-keto-enol tautomeric type into COFs selective layer, and adjust the molecular network structure and crystallinity of the COFs layer with variable pore aperture. The results indicated that the as-prepared TpBd/PSf and TpBdMe/PSf membranes could be efficiently applied for dye separation process with congo red rejection above 99.0%. Compared with TpBd/PSf membrane, water permeability of TpBdMe/PSf membrane increased from 33.6 L·m−2·h−1·bar−1 to 62.2 L·m−2·h−1·bar−1. Moreover, both TpBd/PSf and TpBdMe/PSf membranes exhibited excellent anti-fouling property, chemical and thermal stability. This work develops a facile method to prepare the imine-linked COFs membrane with variable pore aperture by changing reaction parameters and selecting appropriate amine monomers.

Naturally derived polysaccharides-modified PSF membranes: A potency in enriching the antifouling nature of membranes

The present work investigates the antifouling properties and dye removal efficiency of lignocellulose and caramel induced polysulfone (PSF) membranes. The PSF-based flat sheet membranes were prepared via diffusion induced phase separation method using different additional amounts of lignocellulose (LGC) as a hydrophilic additive and caramel as a pore forming agent. The prepared membranes were structurally characterized using various techniques and their performance was evaluated by pure water flux and water uptake capacity. MWCO studies has also been carried out. The studies on rejection and fouling characteristics of membranes was assessed using bovine serum albumin (BSA). The LGC and caramel modified PSF membranes demonstrated a significantly enhanced flux of ~250 L/m2 h and the BSA rejection was found to be around 97% with a flux recovery ratio (FRR) of ~90%. Similarly, the removal efficiency of methylene blue and congo red dyes from lignocellulose induced membranes were found to be ~98% and the observed efficiency could be attributed to their rich adsorption and increased electrostatic repulsion respectively. In addition, the agglomerated congo red dye on the membrane was successfully recovered using ethanol and the membranes were reused several times with little compromise in flux and congo red rejection. Overall, the developed strategy opens up an effective possibilities to enhance the thermal and mechanical properties, hydrophilicity, permeability, antifouling properties and dye removal capacity of the PSF membranes.

Glutaraldehyde and polyvinyl alcohol crosslinked cellulose membranes for efficient methyl orange and Congo red removal

Self-standing and flexible regenerated cellulose membranes were fabricated by using a facile ZnCl2/CaCl2/cellulose dissolution system. The filtration experiments of the membranes were conducted by using methyl orange and Congo red as water contaminations. To improve the selectivity and stability, the crosslinkers of glutaraldehyde and polyvinyl alcohol were introduced to the membrane network. The best performance was observed over glutaraldehyde and polyvinyl alcohol crosslinked cellulose (P-G-RC) membrane with a Congo red rejection rate of 99.9% and a methyl orange rejection rate of 93.5%. The suitable pore radius (0.67 nm), low root-mean-square roughness (2.9 nm) and abundant hydroxyl groups were considered as the primary reasons contributed to the separation behavior. Furthermore, the P-G-RC membrane displayed excellent stability and reusability during the filtration tests.