The remediation of wastewater containing 4-chlorophenol using integrated photocatalytic and biological treatment

In this work, the performance of integrated photocatalytic and biological treatment was studied for the degradation of 4-chlorophenol (MCP) present in wastewaters. Photocatalysis was used as a pre-treatment to biological degradation. Pollutant removal efficiency was quantified using MCP removal and total organic carbon (TOC) removal. Both photocatalytic as well as biological treatments were carried out in batch reactors, using TiO₂ as the photocatalyst. The inoculum for biological experiments was obtained from paper mill effluent treatment plant and was developed through a process of selection and acclimatization. Effect of TiO₂ concentration on the photocatalytic degradation of MCP was studied along with the effect of the duration of photochemical oxidation and glucose concentrations (0 g/L, 1 g/L and 2 g/L) on the biodegradation of MCP. Integrated biological and photochemical degradation was found to be more effective in treating MCP, especially at higher concentrations (400 mg/L). An initial MCP concentration of 400 mg/L required 96 h for complete mineralization when treated with the process combination, whereas the treatment went on up to 264 h when biodegradation alone was employed.     

Exploring the ellipsoidal and core-shell geometries of copper-seamed C-alkylpyrogallol[4]arene nanocapsules in solution

Small-angle neutron scattering (SANS) studies were used to probe the stability and geometry of copper-seamed C-alkylpyrogallol[4]arene (PgC(n)Cu; n = 11, 13, 17) hexamers in solution. Novel structural features are observed at chain lengths greater than 10 in both solid and solution phase. Scattering data for the PgC(11)Cu and PgC(13)Cu in chloroform fitted as core-shell spheres with a total spherical radius of about 22.7 and 22.9 ? respectively. On the other hand, the scattering curve for the PgC(17)Cu hexamer at both 1% and 5% mass fractions in o-xylene did not fit as a discrete sphere but rather as a uniform ellipsoid. The geometric dimensions of the ellipsoid radii are 24 ? along the minor axis and 115 ? along the major axis. It is expected that an individual hexamer with heptadecyl chains would exhibit a uniform radius of ca. 24 ?. However, an approximate ratio of 1:5 between radii lengths for the minor axis and major axis is consistent with interpenetration of the heptadceyl chains of adjacent hexamers to form a single ellipsoidal assembly.     

Synthesis of anionic hypervalent cyclic selenenate esters: relevance to the hypervalent intermediates in nucleophilic substitution reactions at the selenium(II) center

The synthesis of a diaryl diselenide that contains 2,6‐dicarboxylic acid groups, 2,2′‐diselanediylbis(5‐tert‐butylisophthalic acid) ( 10 ), is described. Diselenide 10 undergoes intramolecular cyclization in methanol to form a cyclic selenenate ester, 5‐tert‐butyl‐3‐oxo‐3H‐benzo[c][1,2]oxaselenole‐7‐carboxylic acid ( 11 ). The cyclization reaction proceeds more rapidly in the presence of organic bases, such as pyridine, adenine, and 4,4′‐bipyridine, to form pyridinium 5‐tert‐butyl‐3‐oxo‐3H‐benzo[c][1,2]oxaselenole‐7‐carboxylate ( 14 ), adeninium 5‐tert‐butyl‐3‐oxo‐3H‐benzo[c][1,2]oxaselenole‐7‐carboxylate ( 15 ), and 4,4′‐bipyridiniumbis(5‐tert‐butyl‐3‐oxo‐3H‐benzo[c][1,2]oxaselenole‐7‐carboxylate) ( 16 ), respectively. However, 2,2′‐diselanediyldibenzoic acid ( 22 ) does not undergo cyclization under similar conditions. Structural studies on cyclic selenenate esters 14 – 16 revealed that the Se???O (COO^?) secondary distances (2.170, 2.075, and 2.176 Å) were significantly shorter than the corresponding Se???O distances (2.465, 2.472, and 2.435 Å) observed for the selenenate esters stabilized by the neutral donors (CHO, COOH, and COOEt). ¹H, ¹³C, and ⁷⁷Se NMR spectroscopy of compounds 11 and 14 – 16 reveal that the aryl protons of compound 11 and the organic cations of compounds 14 – 16 exchange between the two carboxylate groups via a hypercoordinate intermediate. The corresponding hypercoordinate intermediate ( 14 b , pyridinium selenuranide) for compound 14 was detected at low temperatures using ⁷⁷Se NMR spectroscopy. The presumed hypercoordinate intermediates in the carboxylate‐exchange reactions at the selenium(II) center for a set of model reactions were optimized using DFT‐B3LYP/6–311+g(d) calculations and their structural features compared with the X‐ray structure of anionic selenenate esters 14 – 16 .     

Preparation,X-ray crystallography and thermolysis of transition metal nitrates of 2,2′-bipyridine (Part 63)

Recent work has described the preparation and characterization of the two complexes [Fe₂(C₁₀H₈N₂)₄O(OH₂)₂](NO₃)₄ and [Co(C₁₀H₈N₂)₃]₂[Co(OH₂)₆]·7(OH₂) (NO₃)₈ in which both the nitrogen atoms of 2,2′-bipyridine are directly bonded with the metals. Their structures were determined by single-crystal X-ray diffraction at 296 K. Thermolysis of these complexes has been detailed by the use of TG–DTA and ignition delay measurements. Kinetics of thermal decomposition has also been established. Model free isoconversional and model fitting kinetic approaches have been applied to isothermal TG data for the decomposition of these complexes.     

C-H/π-interaction-guided self-assembly in π-conjugated oligomers

We report CH/π hydrogen-bond-driven self-assembly in π-conjugated skeletons based on oligophenylenevinylenes (OPVs) and trace the origin of interactions at the molecular level by using single-crystal structures. OPVs were designed with appropriate pendants in the aromatic core and varied by hydrocarbon or fluorocarbon tails along the molecular axis. The roles of aromatic π-stack, van der Waals forces, fluorophobic effect and CH/π interactions were investigated on the theromotropic liquid crystallinity of OPV molecules. Single-crystal structures of hydrocarbon OPVs provided direct evidence for the existence of CH/π interactions between the π-ring (H-bond acceptor) and alkyl C-H (H-bond donor). The four important crystallographic parameters, d(c-x)=3.79 ?, θ=21.49°, φ=150.25° and d(Hp-x)=0.73 ?, matched in accordance with typical CH/π interactions. The CH/π interactions facilitate the close-packing of mesogens in x-y planes, which were further protruded along the c axis producing a lamellar structure. In the absence of CH/π interactions, van der Waals interactions drove the assembly towards a Schlieren nematic texture. Fluorocarbon OPVs exhibited smectic liquid-crystalline textures that further underwent Smectic A (SmA) to Smectic C (SmC) phase transitions with shrinkage up to 11%. The orientation and translational ordering of mesogens in the liquid-crystalline (LC) phases induced H- and J-type molecular arrangements in fluorocarbon and hydrocarbon OPVs, respectively. Upon photoexcitation, the H- and J-type molecular arrangements were found to emit a blue or yellowish/green colour. Time-resolved fluorescence decay measurements confirmed longer lifetimes for H-type smectic OPVs relative to that of loosely packed one-dimensional nematic hydrocarbon-tailed OPVs.     

Structural analysis of some sodium and alumina rich high-level nuclear waste glasses

Sodium- and aluminum-rich high-level nuclear waste glasses are prone to nepheline (NaAlSiO₄) crystallization. Since nepheline removes three moles of glass-forming oxides (Al₂O₃ and SiO₂) per mole of Na₂O, the formation of this phase can result in severe deterioration of the chemical durability in a given glass. The present study aims to investigate the relationships between the molecular-level structure and the crystallization behavior of sodium alumino-borosilicate-based simulated high-level nuclear waste glasses with infrared spectroscopy (FTIR) and X-ray diffraction, respectively. The molecular structure of most of the investigated glasses comprise a mixture of Q² and Q³ (Si) units while aluminum and boron are predominantly present in tetrahedral and trigonal coordination, respectively. The increasing boron content has been shown to suppress the nepheline formation in the glasses. The structural influence of various glass components on nepheline crystallization is discussed.     

Force Constants and Mean Amplitudes of Vibration of the Thiazyl Halides Cisn and BrSN

The force constants have been calculated for thiazylnalides CISN and BrSN employing general valence force field and Urey-Dradley force field. The computed results show some interesting features. The mean amplitudes of vibration have also been calculated at temperatures, O°K, 298.15°K and 500°K. These results will be helpful for the interpretation of the electron diffraction data whenever available.     

Microenvironment in the corona region of triblock copolymer micelles: temperature dependent solvation and rotational relaxation dynamics of coumarin dyes

Dynamic Stokes' shift and fluorescence anisotropy measurements using coumarin-153 (C153) and coumarin-151 (C151) as the fluorescence probes have been carried out in aqueous poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123) and poly(ethylene oxide)100-poly(propylene oxide)70-poly(ethylene oxide)100 (F127) block copolymer micelles with an aim to understand the water structures and dynamics in the micellar corona region. It has been established that the probes reside in the micellar corona region. It is indicated that the corona regions of P123 and F127 micelles are relatively less hydrated than the Palisade layers of neutral micelles like Triton-X-100 and Brij-35. From the appraisal of total Stokes' shift values for the probes in the two block copolymer micelles, it is inferred that the F127 micelle is more hydrated than the P123 micelle. It is observed that the dynamic Stokes' shift values for both of the probes remain more or less similar at all the temperatures studied in the P123 micelle. For C153 in F127, however, the observed Stokes' shift is seen to decrease quite sharply with temperature, though it remains quite similar for C151. Moreover, the fraction of the unobserved initial dynamic Stokes' shift is appreciably higher for both the probes in the F127 micelle compared to that in P123. Over the studied temperature range of 293-313 K, the spectral shift correlation function is described adequately by a bi-exponential function. Rotational relaxation times for C153 in both the micelles show a kind of transition at around 303 K. These results have been rationalized assuming collapse of the poly(ethylene oxide) (PEO) blocks and formation of water clusters in the corona region due to dehydration of poly(ethylene oxide) blocks with an increase in temperature. A dissimilar probe location has been inferred for the differences in the results with C153 and C151 probes in F127. Comparison of the microviscosity and the hydration of the block copolymer micelles has also been made with those of the other commonly used neutral micelles, for a better understanding of the results in the block copolymer micelles.     

The synthesis and structural characterization of N-ortho-ferrocenyl benzoyl amino acid esters. The X-ray crystal structure of N-{ortho-(ferrocenyl)benzoyl}-l-phenylalanine ethyl ester

A series of N-ortho-ferrocenyl benzoyl amino acid ethyl esters 3-9 have been prepared by coupling ortho-ferrocenyl benzoic acid 2 to the amino acid ethyl esters of glycine, l-alanine, l-leucine, l-phenylalanine, β-alanine, 4-aminobutyric acid and (±)-2-aminobutyric acid using the conventional 1,3-dicyclohexylcarbodiimide, 1-hydroxybenzotriazole protocol. The compounds were fully characterized by a range of NMR spectroscopic techniques and by mass spectrometry (MALDI-MS, ESI-MS). The X-ray crystal structure of the l-phenylalanine derivative 6 has been determined.     

Fabrication of polyindene and polyindole nanostructures

One-dimensional (1D) nanostructures of fused ring polymeric systems: polyindene (PIn) and polyindole (PInd) were fabricated onto glass substrates using a chemical vapor deposition (CVD) method. Morphology of fabricated PIn and PInd structures studied using Olympus microscope reveals formation of 1D straight tubular, smooth and fluorescent nanostructures. The results obtained were further correlated with scanning electron microscopic (SEM) studies of PIn and PInd nanostructures, indicating appearance of fine nanothread entangled network (having diameter ∼ 50 nm) for PIn, and well-defined, straight and aligned nanotubes (having diameter ∼ 60 nm) for PInd. A comparative study on the morphology/dimensions of fabricated PIn and PInd nanostructures with the nanosized PIn and PInd structures obtained by oxidative synthetic routes is also discussed. The structural composition of fabricated PIn and PInd nanostructures is confirmed by Fourier transform infrared (FTIR) spectroscopy, thereby indicating existence of all infrared markers corresponding to the characteristic bands present in PIn and PInd. The study suggests that the fabricated PIn and PInd nanodimensional structures may find potential applications in the field of nanotechnology.