Faculty Publications
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Item Ammonia recovery from water, wastewater, and radioactive wastewater(Elsevier, 2024) Gnani Peer Mohamed, S.I.G.P.; Isloor, A.M.; Padaki, M.The membrane-based separation process for the ammonia recovery from the water, wastewater, and radioactive wastewater retains great potential importance to reduce the environmental impacts. The traditional Haber–Bosch process for the production of ammonia is responsible for the 1.6% global CO2 emission and annual global energy consumption of 1.5%–2.5%. Ammonia is corrosive and causes severe irritation to the respiratory tract, eyes, and skin when its concentration is above 100ppm. Furthermore, the intense overexposure also leads to irreversible pulmonary damage. As the wastewater occurs in large quantities and comprises a high-level concentration of ammonia, it has been explored as a source of ammonia recovery. The ammonia recovery from the wastewater reduces the environmental footprint and increases the production of fertilizer. In this chapter, the developing membrane-based separation process such as nanofiltration, reverse osmosis, forward osmosis, membrane contactor, and electrodialysis for ammonia recovery has been reviewed. The benefits and challenges associated with these membrane-based separation processes for ammonia recovery are also discussed. © 2024 Elsevier Inc. All rights reserved.Item Preparation, characterization and performance study of poly(isobutylene- alt-maleic anhydride) [PIAM] and polysulfone [PSf] composite membranes before and after alkali treatment(2011) Padaki, M.; Isloor, A.M.; Belavadi, G.; Prabhu, K.N.Recently, nanofiltration (NF) membranes have been drawing much attention in the field of filtration and the purification process of water/industrial effluents, because of their energy efficiency and low cost. Although reverse osmosis (RO) membranes are widely used in present desalination units, NF membranes are considered as "future membranes" for desalination, because of the low operating pressure. In the present paper, we hereby report the synthesis of a new composite NF membranes of poly(isobutylene-alt-maleic anhydride) (PIAM) with polysulfone, using a diffusion-induced phase separation (DIPS) method. The anhydride groups were converted to acid group by alkaline treatment. Newly prepared composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) studies. The membranes were tested for salt rejection and water swelling. The resulted NF membranes exhibited significantly enhanced water permeability while retaining high salt rejection. The flux and rejection rate of the NF membrane to Na2SO4 (500 ppm) reached to 11.73 L/(m2 h) and 49% rejection under 1 MPa and also 70:30 composition of the membrane showed 54% water swelling; contact angle measurement, ion exchange capacity, and water uptake of the membrane were recorded. © 2011 American Chemical Society.Item Ethyl 2-[(4-chloro-phen-yl)hydrazono]-3-oxobutanoate(2009) Fun, H.-K.; Chantrapromma, S.; Padaki, M.; Radhika; Isloor, A.M.The mol-ecule of the title oxobutanoate derivative, C12H 13ClN2O3, 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].Item (E)-1-(4-Chloro-phen-yl)ethanone semi-carbazone(2009) Fun, H.-K.; Ching Kheng, C.K.; Padaki, M.; Malladi, S.; Isloor, A.M.In the title compound, C9H10ClN3O, the semicarbazone group is approximately planar, with an r.m.s. deviation from the mean plane of 0.054 (1) Å. The dihedral angle between the least-squares planes through the semicarbazone group and the benzene ring is 30.46 (5)°. In the solid state, mol-ecules are linked via inter-molecular N - H?O and N - H?N hydrogen bonds, generating R22(9) ring motifs which, together with R22(8) ring motifs formed by pairs of inter-molecular N - H?O hydrogen bonds, lead to the formation of a seldom-observed mol-ecular trimer. Furthermore, N - H?O hydrogen bonds form R21(7) ring motifs with C - H?O hydrogen bonds, further consolidating the crystal structure. Mol-ecules are linked by these inter-molecular inter-actions, forming two-dimensional networks parallel to (100).Item (E)-1-Phenyl-ethanone semicarbazone(2009) Fun, H.-K.; Yeap, C.S.; Padaki, M.; Malladi, S.; Isloor, A.M.In the title compound, C9H11N3O, 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) Å and ? = 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 P21/c. The semicarbazone group is essentially planar, with a maximum deviation of 0.046 (1) Å for 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?? inter-actions. © 2009 Fun et al.Item Ethyl 2-[(3-chloro-phen-yl)hydrazono]-3-oxobutanoate(2009) Fun, H.-K.; Padaki, M.; Holla, S.R.; Isloor, A.M.; Chantrapromma, S.The mol-ecule of the title oxobutanoate derivative, C12H 13ClN2O3, adopts a keto-hydrazo tautomeric form and is roughly planar, the angle between the benzene ring and the mean plane through the hydrazone and aliphatic chain being 1.49 (6)°. This planarity is further aided by the formation of an intra-molecular N - H?O hydrogen bond which generates an S(6) ring motif. The aromatic ring and aliphatic chain have a trans configuration with respect to the N - N bond. In the crystal packing, centrosymmetric R 2 2(16) dimers are formed through pairs of weak C - H?O(3-oxo) inter-actions. These dimers are linked together through weak C - H?O(carboxyl-ate C=O) inter-actions into ribbons along the b-axis direction. These ribbons are stacked along the a-axis direction. The crystal also exhibits Cl?Cl [3.4988 (6) Å] and C?O [3.167 (2)-3.335 (2) Å] short contacts.Item (E)-1-(4-Fluoro-phen-yl)ethan-1-one semicarbazone(2009) Fun, H.-K.; Yeap, C.S.; Padaki, M.; Malladi, S.; Isloor, A.M.In the title compound, C9H10FN3O, the semicarbazone group is nearly planar, with the maximum deviation of 0.044 (1) Å for one of the N atoms. The mean plane of semicarbazone group forms a dihedral angle of 30.94 (4)° with the benzene ring. The mol-ecules are linked into a supra-molecular chain by N - H?O hydrogen bonds formed along the c axis. The crystal structure is further stabilized by weak inter-molucular C - H?? inter-actions; the closest C?Cg contact is 3.6505 (11) Å.Item Ethyl 2-[(2,6-dimethylphenyl)-hydrazono]-3-oxobutanoate(2009) Fun, H.-K.; Jebas, S.R.; Padaki, M.; Hegde, C.; Isloor, A.M.The title compound, C14H18N2O3, crystallizes with two independent molecules in the asymmetric unit, having closely comparable geometries. Both molecules are essentially planar [maximum deviations from the mean plane of 0.069 (1) and 0.068 (1) Å for the two molecules] and contain an intramolecular N?H?O hydrogen bond which generates a ring with graph-set motif S(6). In the crystal, the molecules are linked into chains along the c axis by intermolecular C?H?O hydrogen bonds, and intermolecular C?H?? interactions are also present.Item 4-Amino-3-(p-tolyl-oxymeth-yl)-1H-1,2,4-triazole-5(4H)-thione(2009) Fun, H.-K.; Goh, J.H.; Vijesh, A.M.; Padaki, M.; Isloor, A.M.In the title triazole compound, C10H12N 4OS, 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?? inter-actions. © 2009 Fun et al.Item 4-Amino-3-(o-tolyl-oxymeth-yl)-1H-1,2,4-triazole-5(4H)-thione(2009) Fun, H.-K.; Liew, W.-C.; Vijesh, A.M.; Padaki, M.; Isloor, A.M.The asymmetric unit of the title compound, C10H 12N4OS, 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 ?-? inter-actions between the benzene and triazole rings [centroid-centroid distance = 3.5311 (6) Å] are also present. © 2009 Fun et al.