Dye Removal Performance Research Articles

Fiber engineering of silica-based aerogels with surface specificity and regenerability for continuous removal of dye pollutants from wastewaters

Aerogels are attractive candidates as advanced adsorbents in water-treatment given their high specific surface area and reticulated porous structure. We present here hollow silica aerogel fibers (SAFs) engineered based on a wet spinning approach for dye removal from wastewaters. The surface characteristics of SAFs can be flexibly adjusted via a simple post-modification by silane coupling agents, delivering not only high dye removal efficiency but also great feasibility for various dyes. By the means of incorporating commercially used photocatalysis active nanoparticles (P25) into SAFs (denoted as SAF-P25), a photo-regenerable SAF-P25 adsorbent can be successfully prepared. SAF-P25 can recover its initial adsorption properties via a simple UV or natural light irradiation treatment. Consequently, the novel SAF-P25 is able to continuously adsorb and degrade dyes in wastewaters with a long-term dye removal performance. In addition to high adsorption efficiency and photo-renewability, the SAF-based adsorbent also preserves the merits of low cost, good scalability, wide applicability, and operation simplicity; all these make it become a promising dye removal system for future wide usage in various wastewater purifications. • Silica aerogel fibers (SAFs) were manufactured by wet spinning. • Specific surface modification endowed SAFs with adsorption selectivity. • After the introduction of photocatalyst, SAFs showed renewability and maintained excellent adsorption performance. • SAF-P25 can continuously and efficiently remove dyes under UV or natural light.

Integration with MoO3 microrods as precursors for hierarchical polyaniline microtubes and composites for anionic dye removal in water treatment

PANI microtubes were well constructed with MoO3 microrods as a sacrificing template, and exhibited excellent performance for dye removal. Moreover, the PANI microtubes can be a good support to synthesize multifunctional PANI-based composites.

Effective adsorption of dyes on an activated carbon prepared from carboxymethyl cellulose: Experiments, characterization and advanced modelling

• An activated carbon with a high surface area and outstanding dye adsorption properties was studied. • Dye adsorption isotherms were quantified at different temperatures. • Statistical physics model was used to attribute theoretical interpretation of dye adsorption mechanism. An activated carbon with a high surface area and outstanding adsorption properties was prepared for dye removal from water. The new adsorbent was obtained from the chemical activation and pyrolysis of sodium carboxymethyl cellulose (CMC). This activated carbon was employed to analyze and characterize the adsorption mechanism of three dye molecules: methyl violet, allura red and congo red. Different characterization techniques and experimental adsorption isotherms quantified at different temperatures (25–45 °C) were utilized to interpret the dye adsorption mechanism. A double layer adsorption model was employed to estimate the steric and energetic parameters associated with the adsorption of these dye molecules. The modelling results provided the possible adsorption orientations of these dyes on adsorbent surfaces at different operating temperatures and the number of bonded dye molecules per functional group of this adsorbent was also analyzed. Calculated adsorption energies showed that both exothermic and endothermic processes were feasible for these dyes and physical forces were involved in the adsorption mechanism. Overall, this new adsorbent showed a competitive performance for dye removal in aqueous solution and can be a potential option for industrial applications.

Efficient Adsorption of Dyes Using Polyethyleneimine-Modified NH2-MIL-101(Al) and its Sustainable Application as a Flame Retardant for an Epoxy Resin.

Metal–organic frameworks (MOFs) exhibit highly designable properties and have been used in wide applications. To further improve their performance, the modification of MOFs is an effective method. However, the modification process is usually complicated. Besides, the sustainable use of MOFs is difficult to achieve due to the complicated recycling treatment. Herein, we designed a polyethyleneimine (PEI)-modified NH2-MIL-101(Al) composite (PEI@NH2-MIL-101(Al)). This composite showed excellent dye removal performance of methyl orange (MO, 89.4%) and Direct Red 80 (DR80, 99.8%). Remarkably, the dye removal application of PEI@NH2-MIL-101(Al) also acted as a modification process toward flame retardant application. Thus, the dye-adsorbed PEI@NH2-MIL-101(Al) composite (MO-PEI@NH2-MIL-101(Al) and DR80-PEI@NH2-MIL-101(Al)) was sustainably used as an effective flame retardant for an epoxy resin (EP) at low additions (4.0 wt %). The limiting oxygen values of EP/MO-PEI@NH2-MIL-101(Al) and EP/DR80-PEI@NH2-MIL-101(Al) increased to 26.5 and 26.7%, respectively. The heat release and the smoke production of dyes-PEI@NH2-MIL-101(Al)/EP were greatly reduced compared with those of EP. This strategy provides a simple and effective modification method for MOFs. Meanwhile, the modified MOF composite can achieve sustainable application, giving full play to the advantages of MOFs.

Fe-ZSM-5 zeolite for efficient removal of basic Fuchsin dye from aqueous solutions: Synthesis, characterization and adsorption process optimization using BBD-RSM modeling

The current study reports the first use of Fe-ZSM-5 as a potential adsorbent for textile effluent purification. The Fe-ZSM-5 zeolite was synthesized through a hydrothermal method using tetrapropylammonium bromide as an organic structure-directing template for application as a binder for basic Fuchsin (BF) dye from aqueous media. SEM observations confirmed that Fe-ZSM-5 exhibits a granular shape with a quasi-hexagonal structure, which is in agreement with its crystallinity demonstrated by XRD analysis. FTIR analysis indicates the abundance of SiOH groups on the Fe-ZSM-5 surface. N2 adsorption-desorption measurement showed the microporous structure (pore size around 1.93 nm) of Fe-ZSM-5 with a BET surface area of 399 m2/g. The uptake performance of Fe-ZSM-5 zeolite for BF dye was systematically studied as a function of different operational parameters. The experimental adsorption data were in good agreement with pseudo-second-order kinetics and Langmuir isotherm with a maximum adsorbed amount of 251.87 mg/g. BF dye adsorption onto Fe-ZSM-5 was a spontaneous and endothermic phenomenon. The binding mechanism is attributed to electrostatic interactions combined with H-bonding. Further, the response surface modeling permits us to optimize BF dye adsorption process. The highest BF dye removal performance was found to be 99.6 % under optimum conditions of pH 5, Fe-ZSM-5 dose 0.75 g/L, initial BF concentration 10 mg/L for 120 min at 20 °C. The findings of this work revealed that Fe-ZSM-5 zeolite could be proposed as an alternative adsorbent with outstanding performance for BF dye removal from wastewaters.

Improving the hydrostability of ZIF-8 membrane by biomolecule towards enhanced nanofiltration performance for dye removal

Zeolitic imidazolate frameworks-8 (ZIF-8)/polymer composite membranes have shown great promise in gas separation, catalysis and biotechnology due to their microporous nature. However, the structural instability against protonation limits the application of ZIF-8 materials in aqueous environments, e.g. water treatment membranes. In this study, a ZIF-8 nanocomposite membrane with satisfactory hydrostability was explored. More specifically, a series of composite ZIF-8 thin film containing DNA molecules were deposited on dopamine-modified polysulfone (PSF) substrates via an in situ growth under ambient conditions. The incorporation of DNA molecules significantly enhanced the hydrophilicity of the composite membrane (water contact angle reduced from 66.9° to 29.2°). Compared with the pure ZIF-8 counterpart, the DNA-containing ZIF-8 membrane exhibited higher water flux, accompanied with higher rejections for organic dyes and inorganic salt ions. More importantly, the DNA-containing ZIF-8 membrane showed significantly enhanced water stability and anti-fouling property during the filtration tests. The utilization of biomacromolecules to stabilize ZIF membrane enables potential applications for ZIF membranes for wider water-related applications.

Factors affecting the degradation of remazol turquoise blue (RTB) dye by titanium dioxide (TiO2) entrapped photocatalytic membrane

This study investigated the photocatalytic degradation of remazol turquoise blue (RTB) dye using titanium dioxide (TiO2) entrapped polyvinylidene fluoride (PVDF) membrane synthesized by non-solvent induced phase separation method. Numerous experiments were conducted to investigate the effects of catalyst loading in membranes, the concentration of dye, feed temperature, pH of the solution, and the addition of H2O2 to the dye solution on the removal of dye. Results were compared with the performance of virgin PVDF and modified PVDF/TiO2 membranes. The experimental results indicated that the optimum TiO2 loading in the membrane was 2 wt%, which enhanced the membrane morphology, permeability, and dye removal performance. The rate of photocatalytic degradation dropped with the increase in dye concentration. The photocatalytic efficiency of the membrane depends on the pH and the temperature of the solution.

Adsorption of Patent Blue V from Textile Industry Wastewater Using Sterculia alata Fruit Shell Biochar: Evaluation of Efficiency and Mechanisms

Biochar prepared from Sterculia alata fruit shell showed a better performance for dye removal than the biomass from Sterculia alata fruit shell. The important process parameters—namely the pH, the amount of biochar, the initial dye concentration and the contact time—were optimized in order to maximize dye removal using biochar of Sterculia alata fruit shell as the bio-sorbent. The results from this study showed that the maximum adsorption of dye on the biochar was obtained at a biochar dosage of 40 g/L, at a contact time of 5 h, and an initial dye concentration of 500 mg/L (pH 2.0; temperature 30 ± 5 °C). The increase in the rate adsorption with temperature and the scanning electron microscopic (SEM) images indicated the possibility of multilayer type adsorption which was confirmed by better fit of the Freundlich adsorption isotherm with the experimental data as compared to the Langmuir isotherm. The values n and R2 in the Freundlich isotherm were found to be 4.55 and 0.97, respectively. The maximum adsorption capacity was found to be 11.36 mg/g. The value of n > 1 indicated physical nature of the adsorption process. The first and second order kinetics were tested, and it was observed that the adsorption process followed the first-order kinetics (R2 = 0.911).

Silylated-montmorillonite as co-adsorbent of chitosan composites for methylene blue dye removal in aqueous solution

Industrialization plays important role in the economy of developing countries, including increasing community welfare. However, the presence of poorly industries waste disposal system has negative impact to the environment. Therefore, it is necessary to overcome this problem with low-cost technology, called adsorption. In this research, silylated-montmorillonite (sMMt) has been successfully prepared as supporting material for adsorption of methylene blue by chitosan. The sMMt was characterized by FTIR, XRD, and elemental mapping techniques. The chitosan/sMMt composites were prepared through dissolution-precipitation method and produced rod-like morphology as observed by SEM. The adsorption process was carried out in a batch method by studying the pH and the adsorption contact time. The adsorption kinetic mechanism of the chitosan/sMMt nanocomposite followed pseudo-second order rather than Lagergren model indicating chemisorption predominant. The addition of silylated-montmorillonite into chitosan enhanced the methylene blue dye removal performance, which evidenced by improving Qe values by 10% compared to chitosan.

A facile approach from waste to resource: Reclaimed rubber-derived membrane for dye removal

The polymer precursor plays a vital role in the membrane structure, as well as its permeance and rejection capability. In general, the polymer utilized in research is purified many times to obtain a higher purity, thus resulting in expensive and energy-consuming raw materials for membranes. Herein, we propose a facile method to prepare a nanofiltration hollow fiber membrane via reclaimed rubber recovered from waste tires as a precursor. The permeation tests reveal that the rubber-derived membrane with 12 wt% precursor concentration and three internal coating times exhibited the best performance for dye removal, with a methyl blue rejection rate of up to 93.1%. After three further filtration cycles, the permeate permeance obtained from the R1-12-L3 membrane could be maintained at 8.3 LMH/bar with a methyl blue rejection rate of 98.1%. These experimental results indicate that the rubber-derived hollow fiber membrane could be a feasible alternative for wastewater purification due to its low-cost, high-performing, and self-cleaning properties.

Performance Evaluation and Optimization of Dyes Removal using Rice Bran-Based Magnetic Composite Adsorbent.

Although several studies have explored green adsorbent synthesized from many types of agriculture waste, this study represents the first attempt to prepare an environmentally friendly rice bran/SnO2/Fe3O4-based absorbent with economic viability and material reusability, for the promotion of sustainable development. Here, rice bran/SnO2/Fe3O4 composites were successfully synthesized and applied for adsorption of reactive blue 4 (RB4) and crystal violet (CV) dyes in aqueous solutions. The adsorption data were well-fitted by the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacities of the RB4 and CV dyes as indicated by the Langmuir isotherm model were 218.82 and 159.24 mg/g, respectively. As results of response surface methodology (RSM) showed, the quadratic model was appropriate to predict the performance of RB4 dye removal. The findings exhibited that an optimum removal rate of 98% was achieved at 60 °C for pH 2.93 and adsorption time of 360 min. Comparative evaluation of different agricultural wastes indicated that the rice bran/SnO2/Fe3O4 composite appeared to be a highly promising material in terms of regeneration and reusability, and showed that the composite is a potential adsorbent for dye removal from aqueous solutions. Overall, the study results clearly suggest that an adsorbent synthesized from rice bran/SnO2/Fe3O4 magnetic particle composites provides encouraging adsorption capacity for practical applications for environmental prevention.

Characterization and performance of rice husk as additive in green ceramic water filter fabricated by slip-casting

PurposeThe purpose of this study is to investigate the using of rice husk (RH) which is a green material derived from agricultural waste with the ability to absorb heavy metal. It has been used in wastewater treatment. In this research, a kaolin-based green ceramic water filter (CWF) incorporated with two different additives (RH and zeolite-based RH ash [RHA]) was successfully fabricated.Design/methodology/approachThe weight ratio of kaolin:additive was varied (90:10, 80:20 and 70:30) and fabricated via the slip-casting technique. The green CWFs were dried (60°C for 1 h), followed by sintering (1,200°C).FindingsThe green CWF of kaolin:RH with a weight ratio of 70:30 showed the best properties and satisfactory performance with a porous cross-section microstructure, highest porous area (4.58 µm2), good structure, lowest shrinkage (8.00%), highest porosity (45.10%), lowest density (1.79 g cm−3), highest water absorption (55.50%) and hardness (241.40 Hv). This green CWF has also achieved good permeability (42.00 L m−2h−1) and removal of the textile dye (27.88%). The satisfactory characterization and good textile dye removal performance (75.47%) were also achieved from green CWF with kaolin:zeolite at a weight ratio of 80:20.Research limitations/implicationsThis research is focused on green CWF and zeolite at a certain amount with the specific characterization analysis methods.Practical implicationsThe use of low-cost waste materials to treat dye wastewater from agricultural by-products/wastes sources in treating the dye will enhance the using of green material.Social implicationsAvoiding the waste sludge that can pollute the environment can create a health issue. The use of low-cost waste materials to treat dye wastewater from agricultural by-products/wastes sources in treating the dye can avoid the waste sludge that can pollute the environment and create serious health issue.Originality/valueAll the kaolin-based green CWFs incorporated with two different additives (RH and zeolite-based RHA) fabricated using a simple slip-casting technique have shown the potential to be used as a filter in wastewater treatment applications.

Fabrication of mechanical robust keratin film by mesoscopic molecular network reconstruction and its performance for dye removal

Regenerated keratin-based adsorbents have attracted much attention in environmental pollution remediation. However, fabricating keratin-based adsorbents with excellent adsorption performance is still a challenging issue due to its weak mechanical property. In this study, mechanical robust keratin composite films were designed and engineered at mesoscopic scale by molecular network reconstruction strategy. It was found that the β-crystallites structure of silk fibroin template could induce the transformation of free unfolded molecular chains of keratin to β-sheet conformation and further resulted in the controllable manipulating of the mechanical properties of keratin films. This mechanical reinforced composite film showed high adsorption efficiency and capacity for dyes as well as ideal regeneration and recycling performance. Adsorption behavior of reactive brilliant blue KN-R by keratin composite films was comprehensively studied. The adsorption capacity (qe) and removal efficiency for KN-R by the adsorbent could reach as high as 190.84 mg/g and 98.52%, respectively. The adsorbent exhibited excellent regeneration and recycling performance due to its mechanical robustness. The molecular network reconstruction strategy is both straightforward and effective for fabricating mechanical robust adsorbent for pollutant remediation.

Synthesis, characterization of β-CD based novel hydrogels with dual objectives of drug release and dye removal

In our recent work, we have reported on hydrogels devoid of cross-linkers. After observing the successful swelling and water retention properties, we have introduced β-cyclodextrin in acrylamide-co–N-(hydroxymethyl)-acrylamide hydrogel to introduce hydrophobic cores. In this work, we have focussed to improve the sustainable drug release and toxic dye removal performance of hydrogel by introducing β-cyclodextrin (β-CD). Four different grades of β- cyclodextrin grafted acrylamide-co–N-(hydroxymethyl)-acrylamide have been synthesized through free radical polymerization technique at room temperature. Different proportions of β-CD and fixed amount of acrylamide (AM), N-(hydroxymethyl)-acrylamide (NHMA) and 2,2′-azobis-[2-(2-imidazolin-2-yl)-propane] dihydrochloride (AIPD as an initiator) have been used. The synthesized grades were characterized using FTIR, SEM, TGA, UV–visible and powder XRD. Hydrogels have shown high swelling capacity, i.e. 3000 times higher than dry weight. The diffusion studies of drug loaded hydrogels have been performed which have followed quasi-Fickian drug release behavior. Cumulative drug release studies of diclofenac sodium has been investigated in buffer solution at pH 7.4 for 66 h. The toxic cationic dye (methylene blue) removal studies have been carried out in highly concentrated dye contaminated aqueous solution at neutral pH. Hydrogel resulted in complete removal of MB dye with lesser dose and in short span of time. β-Cyclodextrin grafted acrylamide-co–N-(hydroxymethyl)-acrylamide-2 and β-cyclodextrin grafted acrylamide-co–N-(hydroxymethyl)-acrylamide-3 showed highest 77% drug release and almost 100% dye removal from solution, respectively.

Electrochemical preparation of Nb2O5 nanochannel photoelectrodes for enhanced photoelectrocatalytic performance in removal of RR120 dye

The present work describes the synthesis of niobium oxide nanochannels (Nb2O5NCs) with high surface area, porosity, photocurrent density, and photoelectrochemical stability as photocatalyst. The Nb2O5NCs were prepared by electrochemical anodization of niobium foil in different electrolytes: 1 M H2SO4 containing 0.4 wt% HF (S1); glycerol containing 0.4 M NH4F (S2); 0.25 g NH4F with 4 vol% water in glycol at 50 °C (S3); and glycerol containing 10 wt% K2HPO4, at 130 °C (S4, annealed in air; S5, annealed in N2). All the Nb2O5NCs showed well-organized arrays of nanochannels grown on the Nb foil, with tube diameters in the order S4<S2<S1<S3 and film thicknesses in the order S1<S2<S3<S4, as determined using FEG-SEM analyses. The samples were also characterized using XRD, EDX, DRS, XPS, EIS, Mott-Schottky analysis, and LSV curves. But, best results were obtained only when phosphorus (about 1% doping) was incorporated into the electrodes samples prepared in glycerol containing 10 wt% K2HPO4 at 130 °C (i.e. S4 and S5). This procedure enhances the absorption intensity in the UV–Vis regions, the conductivity, the charge carrier density, and the photocurrent density. The Nb2O5NC sample S5 was tested for the degradation of Procion Red HE-3B (RR120) dye, as a model pollutant, achieving efficient photoelectrodegradation with nearly 2 times higher mineralization efficiency compared to photolysis (PT) and photocatalysis (PC). Thus, the results indicate that the modification of Nb2O5NC thin film photoelectrodes by phosphorous doping can be a powerful and efficient alternative to usual approaches applied to the treatment of complex reactive dyes.

Carboxymethyl cellulose-hydrogel embedded with modified magnetite nanoparticles and porous carbon: Effective environmental adsorbent

Adsorption is the most efficient technique for the removal of metal ions and organic dyes from water. This stimulates demand for the preparation of eco-friendly adsorbents. In this study, magnetic hydrogels based on a crosslinked carboxymethyl cellulose grafted acrylamide (CMC-g-AM) embedded with porous carbon (PC) and citric acid-modified magnetite were prepared. PC was synthesized via single-step oxidation of bagasse under muffled atmosphere condition. The magnetite (Fe3O4) nanoparticles were synthesized using the co-precipitation method (Fe2+/Fe3+) and citric acid modification (CFe). Functionality and parameters of adsorbent were characterized by infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray. The magnetic hydrogels have a highly effective performance for Pb-ions and methylene blue dye (MB) removal from water due to the unique role of crosslinked CMC matrix in supporting synergy between embedded PC and CFe. Adsorption testing using time intervals (5–120 min) and Pb-ions and MB concentrations (5–500 mg/L) indicate that CMC-g-AM containing equal content of PC and CFe has substantially higher removal efficiency; 70.8 and 96.1 % against 47.8 and 30.2 % (without PC and CFe) for Pb-ions and MB adsorption respectively for CMC-g-AM. The equilibrium time and the maximum sorption capacity (qm) from the adsorption studies were found to be 60 and 30 min and 294.1 and 222.2 mg/g for Pb-ions and MB respectively. The kinetics and isotherms were studied to highlight the adsorption rate and mechanism of the adsorption process.

Removal Efficiency of Acid Red 18 Dye from Aqueous Solution Using Different Aluminium-Based Electrode Materials by Electrocoagulation Process

This work compares commercial aluminium electrode for use in the treatment of wastewater by electrocoagulation process against waste aluminium cans electrode. The applicability of the waste aluminium cans electrode was tested for decolorization of Acid Red 18 dye as a model pollutant. The batch electrocoagulation process using both types of electrode was conducted at a current density of 25 mA/cm2, a pH of 3, an initial concentration of 100 mg/L and 25 min of reaction time. The elemental composition and surface morphology of both electrode materials and the sludge produced were analyzed using SEM-EDX to establish the correlation between the properties and characteristics of both electrode materials with their dye removal performance. The results demonstrated that waste aluminium cans performed better than commercial aluminium electrode with a removal efficiency of 100% in 25 min of reaction time. This was due to the higher Al dissolution of waste aluminium cans electrode that contributed to the larger amount of Al3+ released into the solution to consequently form more flocs to remove the dye molecules. In conclusion, the proposed waste aluminium electrode was considered as efficient and cost-effective and had the potential to replace the conventional ones in treating colored industrial wastewater using electrocoagulation process.

Phosphoric Acid Activated Carbon from Melia azedarach Waste Sawdust for Adsorptive Removal of Reactive Orange 16: Equilibrium Modelling and Thermodynamic Analysis.

Waste wood biomass as precursor for manufacturing activated carbon (AC) can provide a solution to ever increasing global water quality concerns. In our current work, Melia azedarach derived phosphoric acid-treated AC (MA-AC400) was manufactured at a laboratory scale. This novel MA-AC400 was tested for RO16 dye removal performance as a function of contact time, adsorbent dosage, pH, temperature and initial dye concentration in a batch scale arrangement. MA-AC400 was characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering (DLS) and fluorescence spectroscopy. MA-AC400 is characterized as mesoporous with BET surface area of 293.13 m2 g−1 and average pore width of 20.33 Å. pHPZC and Boehm titration confirm the acidic surface charges with dominance of phenolic functional groups. The average DLS particle size of MA-AC400 was found in the narrow range of 0.12 to 0.30 µm and this polydispersity was confirmed with multiple excitation fluorescence wavelengths. MA-AC400 showed equilibrium adsorption efficiency of 97.8% for RO16 dye at its initial concentration of 30 mg L−1 and adsorbent dose of 1 g L−1. Thermodynamic study endorsed the spontaneous, favorable, irreversible and exothermic process for RO16 adsorption onto MA-AC400. Equilibrium adsorption data was better explained by Langmuir with high goodness of fit (R2, 0.9964) and this fitness was endorsed with lower error functions. The kinetics data was found well fitted to pseudo-second order (PSO), and intra-particle diffusion kinetic models. Increasing diffusion constant values confirm the intraparticle diffusion at higher RO16 initial concentration and reverse was true for PSO chemisorption kinetics. MA-AC400 exhibited low desorption with studied eluents and its cost was calculated to be $8.36/kg.

A comparative study between MMT-Fe3O4/PES, MMT-HBE/PES, and MMT-acid activated/PES mixed matrix membranes

In this study, polyethersulfone (PES) nanofiltration mixed matrix membranes (MMMs) were fabricated utilizing different types of modified montmorillonite (MMT) (Fe3O4-montmorillonite (MMT-Fe3O4), acid activated-montmorillonite (MMT-AA), and hyperbranched epoxy-montmorillonite (MMT-HBE)). The morphological and physiochemical characteristics of prepared modified clay nanoparticles and membranes were defined using FTIR, XRD, FESEM, TEM, AFM, pure water flux and water uptake analysis, contact angle (CA) measurement, fouling studies, zeta potential determination, porosity measurements, mechanical properties assessments, and membrane performance evaluation. The results demonstrated that increment of clay nanoparticles' (NPs) weight ratio in PES membranes considerably improved membrane properties such as pure water flux, salt, dyes, and heavy metal removal due to membrane hydrophilicity. Generally, the membrane containing 3 wt% of additive possessed the best performance in terms of salt rejection, dyes and heavy metal elimination, and pure water flux. Membranes containing MMT-HBE showed significantly better heavy metal and dye removal performance than other membranes despite their lower water flux.

A new stable and reusable nanoscale Cu(II) coordination polymer as an efficient dye adsorbent

A new two dimensional nanoscale Copper(II) coordination polymer (CP), [Cu2(pydc)2(bpy)(H2O)2]n (1), where pydc = pyridine-2,5-dicarboxylic acid and bpy = 4,4ʹ-bipyridine, was synthesized using a sonochemical method. CP1 was characterized by scanning electron microscopy (SEM), elemental analysis, FT-IR spectroscopy and X-ray powder diffraction (XRD) and its solid-state structure was determined using the single crystal X-ray diffraction technique. In CP1, each Cu atom is connected to two other Cu atoms through two pydc2− ligands resulting in a 1D helix chain in the b direction, which is then interlinked to the other chains via bpy ligands and produces a 2D coordination polymer. Considering the low cost and availability of CP1, its adsorption performance for dye removal specifically for the dye Congo red (CR), was examined. The maximum mono-layer adsorption capacity of CP1 towards CR could reach 833 mg.g−1, which is higher than most reported CPs. CP1 was successfully recovered using a green sonochemical method for five cycles of adsorption-desorption. The effects of various parameters including pH, initial concentration of CR, reaction time, and adsorbent dose were evaluated. Based on the above results, nano-CP1 could be considered as a potential candidate for the treatment of the pollutions arising from the production and application of dyes.