Separation Of Dyes Research Articles

Preparation of PVDF mixed matrix membrane based on hydrophilic imine type covalent organic framework(COF) for dye and salt separation

Due to its high porosity, excellent chemical stability, and low density, covalent organic frameworks have been widely researched in membrane separation technology. This study prepared COF-LZU1 PVP/PVDF membranes with different loadings of covalent organic framework (0–0.8 wt% COF-LZU1) synthesized by the room temperature method incorporated into a polyvinylpyrrolidone (PVP) /polyvinylidene fluoride (PVDF) matrix. The addition of hydrophilic COFs improved the hydrophilicity of the membrane, reducing the water contact angle on the membrane surface from 79° (PVDF membrane) to 58° (optimized membrane, M0.4). The water permeance of membranes was improved by 2.3 times by incorporating 0.4 wt% COF-LZU1 nanoparticles. Moreover, the rejection ratio for eriochrome black T (CBT), acid red (AR), congo red (CR), and methylene blue (MB) are all higher than 94.5%. Furthermore, it exhibits excellent permeance of 19.37 L·m−2·h−1·bar−1 in the mixed solution of CR and NaCl, with respective rejection of 96.3% and 1.6%. The BSA filtration test demonstrated that after three cycles, the FRR of COF-LZU1 PVP/PVDF membrane reached 91.52%. Generally speaking, incorporating COF-LZU1 into PVDF polymer matrix can lead to the preparation of membranes with excellent anti-fouling properties for dye separation and dye/salt separation purposes.

Solar Light Active Graphitic Carbon Nitride/Biochar Nanocomposite for RhB Dye Degradation

AbstractIn this work, nanocomposite graphitic carbon nitride/biochar is successfully prepared by physical mixing method to achieve efficient charge separation and photodegradation of RhB dye under sunlight. The biochar is synthesized by heating biomass in muffle furnace in an inert atmosphere. The graphitic carbon nitride is prepared using melamine as a precursor and heating it in a muffle furnace in air atmosphere. The structural characterizations FTIR and X‐ray diffraction are done to confirm the functional groups and crystallography of prepared samples. The photodegradation of RhB dye by nanocomposite is analyzed using a UV–visible spectrophotometer under solar irradiation. It is found that the RhB dye is completely reduced by the nanocomposite in less than 6 min in the presence of sunlight. The kinetic study confirms the photodegradation of RhB dye is first order reaction and rate constant is found to be 0.31 min−1.

Preparation of high performance membrane via one-step polymerization and co-deposition of polydopamine/zwitterionic monomers/poly(ethylene glycol) diacrylate

Membrane separation is an effective method for water purification. However, conventional preparation processes for the membranes usually suffer from complicated production technology and lack versatility. Mussel-inspired chemistry has generated extensive interest in exploring a facile strategy for the preparation of polymeric membranes. In this work, a simple, green and time saving strategy is proposed for accomplishing the surface functionalization via one-step polymerization and co-deposition of dopamine/zwitterion/poly(ethylene glycol) diacrylate (PEGDA). The chain segment of the zwitterion can tightly bind water molecules upon the membrane surface, enhancing the hydrophilicity of the membrane. The chain segment of PEGDA can offer cross-linking sites during the co-deposition process, facilitating the formation of the network structure. The retention to dyes for the membranes prepared with PEGDA was higher than those membranes prepared without PEGDA. The optimized membrane exhibited high water permeance up to 25.9 L m−2 h−1 bar−1, with rejection of 99.7 % and 99.6 % for Methyl blue and Congo Red. Meanwhile, the anti-bacterial rate for the optimized membrane reaches 75.9 %, and the water flux recovery rate (FRR) is as high as 86.65 %. The results cast a light on the exploration of the PDA-based NF membranes, featuring simple production technology and versatile capabilities for the separation of various dyes.

Temperature and photosensitive PVDF-g-PNIPAAm/GPE-PDA@ZnO composite membranes with efficient dyes separation capability and light-cleaning function

In this paper, PVDF-g-PNIPAAm/GEP-PDA@ZnO composite membranes that can undergo light-induced structural response and photodegradation to achieve self-cleaning have been designed and applied to the separation and purification of dye wastewater. The membranes were prepared by blending graphene (GPE)-polydopamine (PDA)-coated zinc oxide (ZnO) core–shell particles into the PVDF-g-PNIPAAm matrix with a non-solvent induced phase separation technique. The GPE and ZnO are tightly bonded by highly adhesive PDA to form a “strawberry-like” core–shell structure. GPE absorbs light energy and converts it into heat, resulting in changes in PNIPAAm chain segments to expand the pore size for self-cleaning. While the membrane is warming up, GPE further promotes the activation of active groups on the surface of PDA@ZnO at high temperature, resulting in unique and excellent photothermal catalytic activity. As a result, the membrane achieves both self-cleaning and pollutant degradation, which results in an FRR of 99.6% after light cleaning. Moreover, the GPE-PDA@ZnO nanoparticle-modified PVDF-g-PNIPAAm membranes exhibit excellent cycling stability with a degradation flux recovery rate of more than 97% even after multiple UV cleaning. Thus, PVDF-g-PNIPAAm/GPE-PDA@ZnO composite membranes extend the versatility of PVDF-based membranes and show extraordinary potential for application in wastewater treatment.

A new multi-functional Cd(II)-organic framework as a platform for high selective fluorescence sensing and dye adsorption

A new three-dimensional porous MOF: {[Cd4(L)2(H2O)6]·(H2O)13·[(H2N(Me)2]2}n was synthesized by solvothermal reaction of 2,4-di(2′,4′-dicarboxyphenyl) benzoic acid ligand with Cd(Ⅱ) metal ion. Cd-MOF has a unique Cd-O metal oxygen chain structure. Metal oxygen chains are connected by ligands to form a three-dimensional porous structure. The solid-state fluorescence spectrum of Cd-MOF shows that the maximum emission peak is at 408 nm. Further liquid fluorescence sensing studies show that the complex can effectively and selectively detect Fe3+, CrO42- and Cr2O72− in aqueous solution with detection limit of 1.77 × 10−4 M, 1.08 × 10−3 M and 1.86 × 10−4 M, respectively, and can be reused five times, so it is a potential fluorescence recognition probe material. The fluorescence quenching mechanism of the system was discussed in detail. At the same time, in the study of the adsorption of dye molecules, it is found that the Cd-MOF has good adsorption capacity for methyl green and methylene blue and can also be used as an excellent dye separation material to selectively adsorb and separate mixed anion and cationic dyes.

Surface modification of GO/PVDF composite membrane by MXene/protonated g‐C₃N₄ nanosheets hybrids with improved dye separation and antifouling properties

AbstractGraphene oxide‐polyvinylidene composite membranes were fabricated via the phase inversion technique. Then, GO‐PVDF membrane with highest water flux was achieved via surface modification with 2‐D MXene and 2‐D MXene /protonated 2‐D g‐C₃N₄ nanosheets hybrid via vacuum filtration of an aqueous dispersion of MXene and MXene‐protonated g‐C₃N₄ nanosheets hybrid, respectively, on GO‐PVDF membrane support to improve filtration efficiency and antifouling properties. The membranes were designated as MXene/GO‐PVDF (M2) and MXene‐protonated g‐C₃N₄/GO‐PVDF(M3). XRD, SEM, and FTIR analysis were used for characterization. The results showed that the performance of both MXene /GO‐PVDF and MXene‐ Pg‐C₃N₄/GO‐PVDF membranes was improved significantly in removing cationic dyes, unlike anionic pigments. Also, the resistance of these membranes against fouling has improved. The MXene‐ Pg‐C₃N₄/GO‐PVDF shows a significant enhancement in the removal of crystal violet (CV) cationic dye (100%) compared to the pristine membrane (84%) after 4 h of the filtration process. Tests also were performed to remove another two cationic dyes Methylene blue (MB), Rhodamine B (RB), and an anionic dye Methyl‐orange. The anionic dye separation rate from the stream did not show significant improvement while cationic dyes show significant enhancement in separation efficiencies. Modified membranes exhibit an enhancement of fouling resistance properties compared to pristine membranes.Highlights The water contact angle decreased from 71 to 45, which means hydrophilicity improved successfully. Membrane fouling resistance was improved around 15%–20%. PVDF membrane was prepared and graphene oxide was added to the matrix to modify the bulk properties. MXene and C3N4 were synthesized successfully. Surface modification of the PVDF membrane was successful by MXene and C3N4.

Tannin-assisted interfacial polymerization towards COF membranes for efficient dye separation.

Membrane separation has been shown to have significant potential in addressing the global shortage of clean water. Covalent organic frameworks (COFs) have gained significant attention in the field of membrane separation due to their structural stability and controllable pore size. Here, a modification of polyethersulfone ultrafiltration membranes with TA-assisted COFs is prepared by interfacial polymerization and co-deposition. Intriguingly, in comparison to the conventional COF synthesis method, the interfacial polymerization reaction used n-butanol as the oil-phase monomer to prevent substrate corrosion. More importantly, the TA-assisted co-deposition not only introduces a large number of environmentally friendly hydrophilic groups to enhance the hydrophilicity of the membrane surface, but also the phenolic hydroxyl group contained in TA generates a quinone group upon oxidation. This group can undergo a Michael addition reaction with the amine group, followed by interfacial polymerization to regulate the COFs pore size. Consequently, the optimized membrane exhibited a high permeation flux of 122.03 L m-2 h-1 bar-1 without altering the pore size structure of the original membranes and demonstrated separation performance for various dyes (Mw: 300-1300 g mol-1), with a retention rate of over 98%. Despite multiple filtrations of methyl blue dye, the membrane prepared by simple rinsing still exhibited high retention rates (>98%) with exceptional stability and retention performance. The optimized membrane demonstrated good hydrophilicity and dye separation performance, indicated promising potential for dye separation applications.

Correction: NaCMC-decorated ZnO nanocomposite polymer membranes for the separation of reactive dyes from textile water

Correction for ‘NaCMC-decorated ZnO nanocomposite polymer membranes for the separation of reactive dyes from textile water’ by R. Robin et al., New J. Chem., 2023, 47, 20517–20526, https://doi.org/10.1039/D3NJ03783E.

Reusable magnetic graphene oxide based anion exchanger for the separation and removal of anionic dyes

Eco-friendly and reusable graphene-based magnetic anion exchange (NMGO) adsorption–desorption mechanisms and the most promising for the effective removal of anionic Congo red dyes from environmental samples.

Adsorptive separation of food and textile dyes from aqueous solution by SBA-15 supported polyaniline/polypyrrole composite: isotherms, kinetics, thermodynamics and recyclability study

Adsorptive separation of food and textile dyes from aqueous solution by SBA-15 supported polyaniline/polypyrrole composite: isotherms, kinetics, thermodynamics and recyclability study

An ultra-high permeability membrane composed of graphene oxide nanosheets supported by a MOF framework utilized for dye separation

Ultra-high permeability separation of Congo red dye is achieved by using a UiO/GO membrane.

Facile Fabrication of Positively Charged Nanofiltration Membrane for the Effective Separation of Cationic Dyes and Salt Mixtures

Facile Fabrication of Positively Charged Nanofiltration Membrane for the Effective Separation of Cationic Dyes and Salt Mixtures

Constructing polyamide/ceramic composite membranes for highly efficient and selective separation of dyes and salts from solution

The modified composite membrane had both good hydrophilicity and strong positive charge, breaking through the trade-off effect.

Brushing a superhydrophilic cross-linked coating on the metal mesh for dye separation

A superhydrophilic mesh prepared by a simple brushing method efficiently separated dye wastewater.

Chitosan-coated electrospun PVDF-ZnO nanofibrous membranes for dye wastewater separation

Dye-containing wastewater causes severe environmental pollution, posing a major challenge to existing water treatment methods. Advanced dye separation technology has emerged to solve this problem. Conventional polyvinylidene fluoride (PVDF) membrane is susceptible to fouling during dye removal due to its low surface free energy and strong hydrophobicity. To improve the hydrophilicity of PVDF, nanofibrous membranes with multilevel roughness are prepared by electrostatic spinning using chitosan (CS) and PVDF-nano-zinc oxide blended solution as raw materials. The adsorption performance of the membranes is evaluated when the ZnO content varies from 0 to 1.2 wt%. When the optimized membrane is used to treat Rhodamine B wastewater, its flux and retention rate reach 580.42 L•m−2•h and 96.33%, respectively (43.94% and 30.12% higher than those of a blank membrane). The flux recoveries are 69.67% for methyl orange and 67.35% for Rhodamine B (25.83% and 36.03% higher than those of a blank membrane, respectively). The irreversible fouling degrees are 30.33% for methyl orange and 32.65% for Rhodamine B, significantly lower than those of a blank membrane (70.51% and 70.07%, respectively).

Modification of a MoS2 composite membrane using nano-silica for high-efficiency dye separation

A novel MoS2/SiO2 composite membrane with larger interlayer spacing intercalation was prepared by vacuum-assisted self-assembly process using SiO2 nanoparticles, which showed high-efficiency dye separation performance and aqueous stability.

Ionic Hyperbranched Poly(amido-amine)-Incorporated Nanofiltration Membranes for High-Efficiency Dye Desalination.

High-efficiency dye desalination is crucial in the textile industry, considering its importance for human health, safe aquatic ecological systems, and resource recovery. In order to solve the problem of effective separation of univalent salt and ionic dye under the condition of high salt, ionic hyperbranched poly(amido-amine) (HBPs) were synthesized based on a simple and scalable one-step polycondensation method and then incorporated into the polyamide (PA) selective layers to construct charged nanochannels through interfacial polymerization (IP) on the surface of a polyvinyl chloride ultrafiltration (PVC-UF) hollow fiber membrane. Both the internal nanopores of HBPs (internal nanochannels) and the interfacial voids between HBPs and the PA matrix (external nanochannels) can be regarded as a fast water molecule transport pathway, while the terminal ionic groups of ionic HBPs endow the nanochannels with charge characteristics for improving ionic dye/salt selectivities. The permeate fluxes and dye/salt selectivities of HBP-TAC/PIP (57.3 L m-2 h-1 and rhodamine B (RB)/NaCl selectivity of 224.0) and HBP-PS/PIP (63.7 L m-2 h-1 and lemon yellow (LY)/NaCl selectivity of 664.0) membranes under 0.4 MPa operation pressure are much higher than PIP-only and HBP-NH2/PIP membranes. At the same time, this project also studied the membrane desalination process in a simulated high-salinity dye/salt mixture system to provide a theoretical basis and technical support for the actual dye desalination process.

Robust reduced graphene oxide-PDA/ZIF-8 aerogel composite for cyclic, high-capacity dye adsorption

The contamination of nanosized organic dyes in the water bodies is of great concern as it adversely affects the marine ecosystem and biodiversity, leading to water-borne ailments. In recent years, designing sustainable, high-performance, and cost-effective composite adsorbents embedded with functional adsorbents for wastewater treatment has attracted immense attention. In this work, a new composite aerogel (rGO-PDA/ZIF-8) was prepared via self-assembling graphene oxide (GO) flakes to form a three-dimensional (3D) structure with functional polydopamine (PDA). Then, ZIF-8 crystals were decorated on the porous aerogel structure via the in-situ crystallization method. PDA-modified rGO aerogel provided abundant useful functional groups, such as –OH, –COOH, and –NH–, on the surface, while the incorporation of ZIF-8 nanocrystals further endowed composite aerogels with higher surface area and extra functional groups for enhanced organic dye adsorption. Our results revealed that the composite aerogel exhibited not only ultrahigh adsorption towards methylene blue (MB) with a maximum adsorption capacity of 1045 ± 2.9 mg g−1 (with a maximum rejection rate of > 99 %) but also excellent recyclability with a slightly decreased adsorption capacity of 897 ± 26.9 mg g−1 and a stable removal efficiency of > 92 % even after 10 cycles of adsorption. To the best of our knowledge, the obtained adsorption capacity almost doubled the best-reported values at similar conditions in the literature. The excellent adsorption performance is owing to strong π–π and electrostatic attractions between the dye molecules and the hierarchical porous composite structures with functional PDA coating and ZIF-8 nano-adsorbents. Therefore, the new composite rGO-PDA/ZIF-8 aerogel composite has great potential in high-performance, cyclic small organic dye separation.

Nanodomain Control in Carbon Molecular Sieve Membranes via Nanomaterial Footprinting

Carbon molecular sieve (CMS) membranes, fabricated via pyrolysis, are attracting attention owing to their stability under harsh environments, including high temperatures, organic media, and extreme pH. Herein, the fabrication of composite CMS (CCMS) membranes by incorporating sphere‐shaped C60(OH) and ellipsoid‐shaped C70(OH) fullerenol nanomaterials into intrinsically microporous 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride 3,3′‐dimethyl‐naphthidine polyimide is reported. The encapsulation of the nanomaterials by the polymer matrix, their chemical footprint, and the variation in the local chemistry of the pyrolyzed membranes are successfully revealed via nanodomain analysis using nano‐Fourier‐transform infrared spectroscopy. The incorporation of fullerenol nanomaterials into CMS membranes can induce the formation of fractional free volume upon pyrolysis, which can translate into molecular sieving enhancement. The effects of the concentration and geometrical shape of the fullerenol nanomaterials are successfully correlated with the membrane separation performance. The CCMS membranes demonstrate excellent stability and pharmaceutical and dye separation performance in organic media. Herein, nanodomain control is pioneered in CCMS membranes via nanomaterial footprinting to induce porosity during pyrolysis and subsequent control molecular sieving performance.

Separation of cationic methylene blue dye from its aqueous solution by S-sulfonated wool keratin-based sustainable electrospun nanofibrous membrane biosorbent

The use of electrospun nanofibrous membranes for the treatment of dyehouse effluent is drawing attention because of their high surface area, and dye adsorption capability. In this work, nanofibrous membranes of S-sulfonated wool keratin protein/poly(vinyl alcohol) or PVA were prepared by electrospinning, and their effectiveness as an adsorbent for the removal of cationic methylene blue (MB) dye was studied. The electrospun nanofibers fabricated from keratin/PVA had a considerably finer average diameter (79.0 nm) compared to the average diameter (255.4 nm) exhibited by nanofibers produced from PVA alone. The optimal adsorption capacity was attained at a pH value close to neutral at ambient temperature (238.7 mg g−1), and the pseudo-second-order model was determined to be a reliable fit for the experimental data. Based on the fitted Langmuir model and MB adsorption data, the adsorption mechanism followed a monolayer pattern on the surface of the membrane. The MB dye adsorption capacity was slightly influenced by the presence of sodium chloride. The study demonstrated that the PVA/keratin nanofibrous membrane exhibited good reusability as only a small loss in absorption capacity was observed after three recycling and reuses. The developed biosorbent could be suitable for the high removal of dyes from textile dyehouse effluent.