Liquid- liquid (Cyclohexanone: Cyclohexanol) separation using augmented tight nanofiltration membrane: A sustainable approach.

Organic solvent nanofiltration (OSN) is an incipient technology in the field of organic liquid-liquid separation. The incomplete separations and complexity involved in these, forces many organic liquids to be released as effluents and the adverse effects of these on environment is enormous and irreparable. The work prominences on the complete separation of industrially significant cyclohexanone: cyclohexanol (keto-alcohol oil) and heptane: toluene mixtures. The separations of these above-mentioned organic liquid mixtures were carried out using the fabricated Lewis acid modified graphitic carbon nitride (Cu2O@g-C3N4) incorporated polyvinylidene difluoride (PVDF) composite membranes. These fabricated membranes showed a separation factor of 18.16 and flux of 1.62 Lm-2h-1 for cyclohexanone: cyclohexanol mixture and separation of heptane and toluene mixture (with heptane flux of 1.52 Lm-2h-1) showed a separation factor of 9.9. The selectivity and productivity are based on the polarity and size of the organic liquids. The role of Cu2O@g-C3N4 is influencing the pore size distribution, increased divergence from solubility parameters, polarity, solvent uptake and porosity of the composite membranes. The developed composite membranes are thus envisioned to be apt for a wide range of liquid-liquid separations due to its implicit nature.

Review on Liquid-Liquid Separation by Membrane Filtration.

Liquid-liquid separation is crucial in the present circumstances. Substitution of the conventional types of separation like distillation and pervaporation is mandatory due to the high energy requirement of the two. The separation of organic mixtures has a huge potential in industries such as pharmaceutical, fine chemicals, fuels, textile, papers, and fertilizers. Membrane-affiliated separations are one of the prime techniques for liquid-liquid separations. Organic solvent nanofiltration, solvent-resistant nanofiltration, and ultrafiltration are a few methods through which organic liquid-liquid separation can be attained. Implementation of such a technology in chemical industries reduces the time consumption and is cost efficient. Even though a lot of research has been done, attention is needed in the field of organic-liquid separation aided by membranes. In this review, various membranes used for organic mixture separations such as polar-nonpolar, polar-polar, and nonpolar-nonpolar are discussed with a focus on membrane materials, additives, separation theory, separation type, experimental setup, fouling mitigation, surface modification, and major challenges. The review also offers insights and probable solutions for existing problems and also discusses the scope of research to be undertaken in the future.

Insights into the mechanically resilient, well-balanced polymeric membranes by incorporating Rhizophora mucronata derived activated carbon for sustainable wastewater decontamination.

In this study, hydrophilic activated carbon has been prepared and used to synthesize innovative activated carbon/polysulfone mixed matrix membranes (MMMs). These membranes were investigated in terms of membrane morphology, hydrophilicity, antifouling ability, and metal ions rejection. The activated carbon (AC) was prepared from a simple chemical activation method using Rhizophora mucronata propagules, which are rich in aerenchyma cells and possess a high surface area. The hydrophilicity of the MMMs is enhanced by the incorporation of activated carbon, which is confirmed by the measurement of equilibrium water contact angle, water uptake and pure water flux. The optimized concentration of 0.625 wt% activated carbon (A2) incorporated mixed matrix membrane exhibits better rejection efficiencies of 98 ± 0.5%, 99 ± 0.5%, 92 ± 2%, and 44 ± 1% for Pb+2, Cd+2, Hg+2, and F- with the permeate flux of 28.27, 31.88, 33.21, 43.82 L/m2/h, respectively. The fabricated mixed matrix membranes demonstrated an excellent flux recovery ratio and reversible fouling, when filtrating a mixed feed solution containing 200 ppm BSA, 10 ppm Pb+2 and 10 ppm Cd+2. The optimized A2 membrane showed excellent long-term stability up to 120 h without compromising in permeate flux and rejection efficiency. Finally, a numerical investigation using a usual transport model has shown that dielectric exclusion was the most probable mechanism that can physically explain experimental trends.

Biomass-derived versatile activated carbon removes both heavy metals and dye molecules from wastewater with near-unity efficiency: Mechanism and kinetics.

Due to the ever-increasing industrialization, it is critical to protect the environment and conserve water resources by developing efficient wastewater treatment methods. Traditional methods that simultaneously remove heavy metal ions and complex dyes are too expensive and tedious to commercialize. This work demonstrates the versatility, effectiveness, and potential of a biomass-derived adsorbent (from a mangrove fruit of Rhizophora mucronata) synthesized using a simple route for rapid adsorption of complex dyes and heavy metals with an efficiency of near unity. The cartridges were prepared using activated carbon that removes both dye molecules and heavy metal ions simultaneously from wastewater, corroborating its applicability/feasibility to treat wastewater. Owing to the high surface area (1061.5 m2g-1) and the pore volume (0.5325 cm3g-1), the adsorbent showed >99% removal efficiency in just 12 min of exposure to wastewater. The cartridge exhibits >90% removal efficiency of both dyes and heavy metals from its mixed feed solution. The Langmuir and Freundlich models successfully explained the adsorption kinetics. These developed cartridges are versatile, rapid, efficient, and promising candidates for environmental remediation.

Fabrication of zinc doped aluminium oxide/polysulfone mixed matrix membranes for enhanced antifouling property and heavy metal removal.

Heavy metal removal from water resources is essential for environmental protection and the production of safe drinking water. In this direction, Zinc doped Aluminium Oxide (Zn:Al2O3) nanoparticles were incorporated into Polysulfone (PSf) to prepare mixed matrix membranes for the efficient removal of heavy metals from water. These Zn:Al2O3 nanoparticles prepared by the solution combustion method have a very high surface area (261.44 m2/g) with an approximate size of 50 nm. X-ray Photoelectron Spectroscopy analysis showed that the Al and Zn were in +3 and + 2 oxidation states, respectively. Cross-sectional Scanning Electron Microscopy images revealed the finger-like morphology and porous nature of the membranes. In this study, the optimum loading amount of Zn:Al2O3 nanoparticles was determined. Synthesized membranes showed enhanced hydrophilicity, surface charge, and porosity, which enabled the removal of arsenic and lead with efficiencies of 87% and 98%, respectively. A study of the antifouling properties carried out at various pressures with a feed solution containing Bovine Serum Albumin (BSA) showed 98.4% of flux recovery ratio and reusability up to three continuous cycles. Moreover, this work demonstrates a rational design of novel mixed matrix membranes exhibiting characteristics of hydrophilicity, surface charge, and porosity adequate to realize the efficient removal of heavy metals.

Supplementing multi-functional groups to polysulfone membranes using Azadirachta indica leaves powder for effective and highly selective acid recovery.

Moderate and eco-pleasing ion-exchange trade membranes are in need to recover acid from industrial waste. Present study is focused on incorporation of plant waste (Azadirachta indica, neem leaves powder (NP)) of different composition as filler to polysulfone (PSf) membrane matrix to achieve acid recovery. Membranes were characterized, their chemical, mechanical and thermal stabilities and effectiveness in acid recovery via diffusion has been inspected. Multi-functional groups (-COOH, -NH2, -OH, -OAc, -C = O) present in different components of NP contributes in their own means in H+ ion transportation through membrane in acid recovery. They assisted formation of hydrogen bond and provided channels for ion permeation, and facilitated selective transportation of H+ ion over Fe2+ ions and explained mechanism is in accordance with Grotthuss-type and vehicle mechanism. Membrane with 15% of NP showed better performance in terms of ion exchange capacity (IEC) and acid recovery, at optimum concentration of NP, composite the membrane showed highest IEC values of 3.9771 mmol/g, UH+ value of ≈46.499 × 10-3 m/h and greater separation factor ≈154, which is higher than commercially available DF-120 membrane. An original thought of utilizing NP in membrane matrix opens up promising opportunities for extremely straightforward, easy, cost-effective and greener methods of recovery acid.

Fouling resistant functional blend membrane for removal of organic matter and heavy metal ions.

This study investigates the removal of heavy metal ions and humic acid using Cellulose acetate (CA) and Poly (methyl vinyl ether-alt-maleic acid) (PMVEMA) blend membranes. Antifouling properties of blend membranes were also investigated. Flat sheet membranes were prepared by phase inversion technique using different concentrations of CA and PMVEMA. The prepared membranes were characterized and their performance was evaluated by measuring pure water flux, water uptake capacity and humic acid removal. Rejection of humic acid (HA) was observed to be around 97% for all the blend membranes because of electrostatic interactions between the functional groups of HA and blends. The fouling characteristics of the membranes was assessed using HA as a foulant and the antifouling capacity of blend membranes was observed to be greater with a flux recovery ratio of almost 95% when compared to bare CA, commercial CA (TechInc) and other reported CA blends used for HA rejection. Also, the blend membranes were very effective in removing heavy metal ions (Pb2+, Cd2+ and Cr+6) and humic acid simultaneously. Overall, the PMVEMA modified CA membranes can open up new possibilities in enhancing the hydrophilicity, permeability and antifouling properties.

Eco-friendly membrane process and product development for complete elimination of chromium toxicity in wastewater.

Hydrophobic polysulphone (PSf) was reformed into a hydrophilic polymer by sulphonation (via electrophilic substitution) and was subsequently made into a composite by incorporating nano titania to reduce Cr (VI) in the concentrated feed to Cr (III), thus eliminating the hazards of Cr (VI). The modified polymer and its composites were characterized by spectroscopic and microscopic techniques. The composite membranes exhibited enhanced hydrophilicity and flux and were evaluated for the rejection of chromium. The effect of pH and interference of counter ions towards rejection was studied. The charges fixed on the surface of the membrane due to titania, support ionic interactions and facilitated the rejection process. Essentially, rejection of up to 98% was achieved. The innovation of using a bifunctional membrane for the rejection of Cr (VI) together with the removal of its toxicity by photocatalytic reduction, leading to the potential recovery of Cr (III), highlight the uniqueness of this work.

Novel modified poly vinyl chloride blend membranes for removal of heavy metals from mixed ion feed sample.

Herein, an attempt has been made to prepare a novel membrane with good efficiency for removal of heavy metal ions namely lead (Pb), cadmium (Cd) and chromium (Cr). 4-amino benzoic acid (ABA) was covalently grafted onto the poly vinyl chloride (PVC) backbone by CN bond to enhance the hydrophilicity. 1H NMR and ATR-IR spectroscopy analysis confirmed the chemical modification of PVC. Further the modified polymer was blended in different compositions with polysulfone (PSf) for optimization. Morphological changes that occurred in blend membranes, due to the incorporation of modified PVC was studied by AFM and SEM techniques. The effect on hydrophilicity and performance of blends owing to incorporation of modified PVC was evaluated by water uptake, contact angle and flux studies. The density of functional groups in blends was analyzed by its ion-exchange capacity. Batch wise filtration of metal ions was carried out and the effect of pressure, feed pH and interference of ions was thoroughly investigated. Essentially, 100% rejection was obtained for all the metal ions in acidic pH with a productivity of 2.56l/m2h. The results were correlated with the results of commercially available NF 270 membrane under the same operating conditions.

Preparation and Characterization of Chitosan Thin Films on Mixed-Matrix Membranes for Complete Removal of Chromium.

Herein we present a new approach for the complete removal of Cr(VI) species, through reduction of Cr(VI) to Cr(III), followed by adsorption of Cr(III). Reduction of chromium from water is an important challenge, as Cr(IV) is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO2 membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSf < PSf/TiO2 < PSf/TiO2/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

2-Cyclo-pentyl-idenehydrazine-carboxamide.

The asymmetric unit of the title compound, C(6)H(11)N(3)O, consists of two independent mol-ecules in which the cyclo-pentane rings adopt envelope conformations with CH(2) grouping as the flap and the semicarbazone groups are essentially planar, with maximums deviation of 0.0311 (12) and 0.0285 (12) Å. In the crystal, N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds link the mol-ecules to form sheets lying parallel to the ab plane.

(2E)-3-(6-Meth-oxy-naphthalen-2-yl)-1-[4-(methyl-sulfan-yl)phen-yl]prop-2-en-1-one.

The asymmetric unit of the title compound, C(21)H(18)O(2)S, consists of two crystallographically independent mol-ecules (A and B). The mol-ecules exist in a trans conformation with respect to the central C=C bond. The naphthalene ring system makes dihedral angles of 51.62 (12) (mol-ecule A) and 52.69 (12)° (mol-ecule B) with the benzene ring. In mol-ecule A, the prop-2-en-1-one group forms dihedral angles of 22.84 (15) and 29.02 (12)° with the adjacent naphthalene ring system and benzene ring, respectively, whereas the corresponding angles are 30.04 (12) and 23.33 (12)° in mol-ecule B. In the crystal, mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds into head-to-tail chains along the a axis. The crystal packing also features C-H⋯π inter-actions. The crystal studied was a pseudo-merohedral twin with twin law (100 0-10 00-1) and a refined component ratio of 0.6103 (16):0.3897 (16).

6-(4-Bromo-phen-yl)-2-eth-oxy-4-(2,4,5-trimethoxy-phen-yl)nicotinonitrile.

There are two mol-ecules in the asymmetric unit of the title compound, C(23)H(21)BrN(2)O(4), which differ in the conformation of their ethoxy residues, i.e. almost co-planar with the pyridine ring in one mol-ecule [C-O-C-C = -174.0 (2)°] but almost perpendicular in the other [C-O-C-C = 92.8 (3)°]. The dihedral angles between the central pyridine ring and the 4-bromo-phenyl and 2,4,5-trimethoxy-phenyl rings are 11.05 (12) and 63.78 (12)°, respectively, in one mol-ecule; the corres-ponding angles in the other mol-ecule are 30.38 (13) and 65.38 (13)°, respectively. In the crystal structure, pairs of mol-ecules are arranged in a face-to-face sandwich structure which further stacks along the b axis. The crystal packing features C-H⋯π inter-actions and Br⋯O [3.5417 (17) Å], Br⋯C [3.748 (3) Å], C⋯N [3.376 (4) Å] and C⋯O [3.351 (3)-3.409 (3) Å] contacts. Finally, π⋯π inter-actions [centroid⋯centroid distances = 3.6346 (19) and 3.6882 (19) Å] are observed.

6-(4-Amino-phen-yl)-2-eth-oxy-4-(2-thien-yl)nicotinonitrile.

In the title nicotinonitrile derivative, C(18)H(15)N(3)OS, the central pyridyl ring makes dihedral angles of 25.22 (10) and 24.80 (16)° with the 4-amino-phenyl and thio-phene rings, respectively. The thio-phene ring is disordered over two orientations by rotation around the C(thio-phene)-C(pyridine) bond; the occupancies are 0.858 (2) and 0.142 (2). The eth-oxy group is slightly twisted from the attached pyridyl ring [C-O-C-C torsion angle = 171.13 (16)°]. In the crystal structure, mol-ecules are linked by N-H⋯N hydrogen bonds into chains along [010]. These chains are stacked along the a axis. C-H⋯π weak inter-actions involving the thio-phene ring are observed.

Diethyl 4-hy-droxy-4-methyl-6-oxo-2-phenyl-cyclo-hexane-1,3-dicarboxyl-ate.

In the title mol-ecule, C(19)H(24)O(6), the cyclo-hexa-none ring adopts a chair conformation. The dihedral angle between the phenyl ring and the best plane through the six atoms of the cyclo-hexa-none ring is 89.68 (7)°. In the crystal structure, mol-ecules are linked via pairs of inter-molecular O-H⋯O hydrogen bonds into centrosymmetric dimers and these dimers are connected by C-H⋯O inter-actions into columns down the a axis.

(E)-1-Phenyl-ethanone semicarbazone.

In the title compound, C(9)H(11)N(3)O, the benzene ring is disordered over two positions with refined occupancies of 0.922 (5) and 0.078 (5). The program PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155] recommends the solution in the space group C2/m with a = 7.3050 (3), b = 6.6745 (2), c = 18.3853 (6) Šand ß = 96.986 (2)°. However, the large number of non-extinct reflections needed to be ignored if C2/m is chosen suggested that the space group is incorrect, even though the R values are lower than that for P2(1)/c. The semicarbazone group is essentially planar, with a maximum deviation of 0.046 (1) Šfor one of the N atoms. The mean plane of the semicarbazone group forms dihedral angles of 33.61 (8) and 39.1 (9)° with the benzene ring of the major and minor components, respectively. In the crystal structure, mol-ecules are linked by inter-molecular N-H⋯O hydrogen bonds into extended chains along the c axis. The crystal structure is further stabilized by weak inter-molucular C-H⋯π inter-actions.

4-Amino-3-(o-tolyl-oxymeth-yl)-1H-1,2,4-triazole-5(4H)-thione.

The asymmetric unit of the title compound, C(10)H(12)N(4)OS, contains two independent mol-ecules, A and B, which differ significantly in the relative orientations of the benzene and triazole rings. The dihedral angle between the above two rings is 6.94 (5)° in mol-ecule A and 77.60 (5)° in mol-ecule B. In the crystal, mol-ecules are linked into a three-dimensional network by N-H⋯S, N-H⋯O, N-H⋯N and C-H⋯S hydrogen bonds and π-π inter-actions between the benzene and triazole rings [centroid-centroid distance = 3.5311 (6) Å] are also present.

4-Amino-3-(p-tolyl-oxymeth-yl)-1H-1,2,4-triazole-5(4H)-thione.

In the title triazole compound, C(10)H(12)N(4)OS, the triazole ring is essentially planar [maximum deviation = 0.009 (1) Å] and forms a dihedral angle of 5.78 (4)° with the benzene ring. In the crystal structure, mol-ecules are linked into dimers by centrosymmetric N-H⋯S inter-actions. These dimers are linked into two-mol-ecule-wide tapes by N-H⋯N and S⋯S [3.2634 (3) Å] inter-actions. In addition, they are further inter-connected by weak N-H⋯S inter-actions into sheets parallel to the ab plane. The crystal structure is further stabilized by weak inter-molecular C-H⋯π inter-actions.

Ethyl 2-[(4-chloro-phen-yl)hydrazono]-3-oxobutanoate.

The mol-ecule of the title oxobutanoate derivative, C(12)H(13)ClN(2)O(3), is nearly planar; the inter-planar angle between the benzene ring and the mean plane through the hydrazono-3-oxobutanoate unit is 2.69 (3)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal packing, C-H⋯O(3-oxo) inter-actions link mol-ecules into dimers. The dimers thus formed are linked through C-H⋯O(carboxyl-ate C=O) inter-actions, leading to the formation of ribbons along the [01] direction, which are stabilized via Cl⋯Cl [3.2916 (3) Å] contacts. The ribbons are stacked via C⋯O contacts [3.2367 (12)-3.3948 (12) Å].

4-Amino-3-[(4-methoxy-phen-yl)amino-meth-yl]-1H-1,2,4-triazole-5(4H)-thione.

The mol-ecule of the title compound, C(10)H(13)N(5)OS, is approximately planar, the dihedral angle between the triazole and benzene rings being 4.53 (10)°. The amino group adopts a pyramidal configuration. In the crystal structure, mol-ecules are linked into two-dimensional networks parallel to (001) by inter-molecular N-H⋯S and N-H⋯N hydrogen bonds. In addition, an S⋯S short contact of 3.3435 (7) Šis observed.