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Adsorption of crystal violet, a hazardous dye, from aqueous solution on activated carbon prepared from carbonized bamboo leaves powder with ZnCl 2 activation is reported in this article using a novel air agitated tapered bubble column adsorber. The adsorbent prepared was characterized by determining the pH PZC , multipoint BET surface area and pore analyses, SEM analysis and FTIR analysis. The pH PZC of the prepared adsorbent was 6.6. The multipoint BET area measured was 291.3 m 2 /g. Batch experiments were conducted as functions of initial concentration (50 to 150 mg/L), contact time (1 to 40 min), adsorbent dose (0.2 to 0.9 g/L) and air flow rate (8.75 × 10 − 5 to 70.00 × 10 − 5 m 3 /s). The maximum percentage removal observed was 99.99% at equilibrium time of 20 min under optimum conditions. The maximum adsorption capacity observed was 393.16 mg/g. Results followed Freundlich isotherm (amongst seven isotherms examined) and pseudo-second order kinetics with intra-particle diffusion. The observed pressure drop was ranging from 2719 to 2837 N/m 2 and the energy dissipation per unit volume of colored liquid was ranging from 82.75 to 634.51 W/m 3 in the system studied. Very high removal and adsorption capacity of the prepared adsorbent observed in the novel tapered air agitated bubble column adsorber is the novelty achieved in the present investigation.

• Used raw biomass combustion residue for adsorptive removal of Crystal Violet following energy and cost saving approach.

The Ichamati River drains the east and south side of the North 24 Parganas district which belongs to the Ganga-Brahmaputra Delta (GBD), covered by deep Quaternary sediments produced under tropical monsoon climate in India. The district is densely populated. The river has huge impact on its population. In this paper, particular attention has been paid to a new method, named optimum cross section index (OCI), which is a numerical representation of a river cross section with respect to its optimum condition. To establish the validity and reliability of OCI, as circumstantial evidences, we have measured and analyzed the geometric parameters, such as width, depth, hydraulic radius, wetted perimeter, and bank profile at 22 points, and applied the areal difference asymmetric index (ADAI). The paper considers that the changing characters of the geometric form of the cross sections and ADAI stand for the OCI. All the techniques reveal that (1) the area of channel decreases abruptly upstream downward, (2) the upstream channel is more symmetrical than the lower reach, and (3) the area of optimum channel gradually increases upstream downward. Results of the study show that the river is going to be deteriorating from upstream downward. OCI has been constructed based on width and depth, which are relatively easily available data. So, this model may be well assessable to identify the optimum channel for a river management.

The structure and energetics of TBP (tri-butyl phosphate), THPO (Tri-hexyl phosphine oxide), and CYANEX925 (bis (2, 4, 4-trimethylpentyl) octylphosphine oxide) and their complexes with Hf and Zr oxycation (ZrO2+ and HfO2+) with BP86 density functional employing TZVP basis set have been presented. The calculated gas phase binding energy was shown to follow the order CYANEX925 > THPO > TBP >. The calculated gas phase binding energy for Hf oxycation is found to be higher than that of Zr oxycation for all the ligands which is contradictory to the observed experimental trend. The experimental selectivity trend was recovered by inclusion of the second solvation sphere of the metal ion both in gas and aqueous phase for a particular ligand. Both the implicit and explicit solvation model fail to predict the high selectivity of ZrO2+ with CYANEX925 over TBP in the absence of nitrate anion. The presence of nitrate anion along with the second solvation shell (n = 24 water molecules) around the oxycation, either in th...

In this article, removal of crystal violet (CV) by adsorption on acidic fly ash collected from an Indian wet ESP with and without biomass combustion residue (BCR), another industrial waste is reported. Initially, fly ash was characterized by its solid density, slurry pH, particle size, pHPZC, Brauner–Emmette–Teller (BET) surface area and pore volume analyses, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The pHPZC and BET surface area of fly ash were 3.30 and 8.57 m2/g, respectively. Batch results revealed high removal (98.33 %) with equilibrium time and optimum dose of 90 min and 7 g/50 mL, respectively. Later, experiments were repeated with the mixed adsorbent (1:1 mass ratio of fly ash and BCR) showing the equilibrium time of 10 min with ~100 % removal. The mixed adsorbent enhanced the adsorption capacity from 1.125 to 9.146 mg/g, i.e., almost by 9 times. Investigations were carried out at various mass fractions of fly ash showing maximum removal of 99.16 % at a mass fraction of 0.1. The response surface modeling revealed the optimum mass fraction and initial concentration of CV of 0.5 and 125 mg/L, respectively, to achieve 94.93 % removal. The corresponding experimental removal observed was 95.99 ± 0.3374 % (mean ± SD of five replicates). The mixed adsorbent showed twofold benefits in the proposed use through extensive pH analyses, such as improving the removal efficiency and maintaining the solution pH well within the safe discharge limit. Experimental results followed the Freundlich isotherm and pseudo-second order kinetics with negligible intra-particle diffusion for both acidic fly ash and mixed adsorbent.

The structures, energetic and thermodynamic parameters of model crown ethers with different donor, cavity and electron donating/ withdrawing functional group have been determined with ab initio MP2 and density functional theory in gas and solvent phase. The calculated values of binding energy/ enthalpy for lithium ion complexation are marginally higher for hard donor based aza and oxa crown compared to soft donor based thia and phospha crown. The calculated values of binding enthalpy for lithium metal ion with 12C4 at MP2 level of theory is in good agreement with the available experimental result. The binding energy is altered due to the inductive effect imparted by the electron donating/ withdrawing group in crown ether, which is well correlated with the values of electron transfer. The role of entropy for extraction of hydrated lithium metal ion by different donor and functional group based ligand has been demonstrated. The HOMO-LUMO gap is decreased and dipole moment of the ligand is increased from gas phase to organic phase because of the dielectric constant of the solvent. The gas phase binding energy is reduced in solvent phase as the solvent molecules weaken the metal-ligand binding. The theoretical values of extraction energy for LiCl salt from aqueous solution in different organic solvent is validated by the experimental trend. The study presented here should contribute to the design of model host ligand and screening of solvent for metal ion recognition and thus can contribute in planning the experiments.

The partition coefficients of large number of organic solute including macrocyclic crown ethers in different water-ionic liquid (IL) bi-phasic systems based on Hartree-Fock (HF) and density functional theory (DFT) are presented here. The structure of imidazolium cation based ILs were optimized at HF-6-311G (d,p) level of theory and then surface charge density were calculated at BP-TZVP level of theory using novel conductor like screening model for real solvents (COSMORS) approach. The calculated value of density is decreased with increasing alkyl chain length for all the ILs considered here. The calculated values of partition coefficient for various organic solutes obtained from the first principle based COSMO-RS theory are reasonably in good agreement with the available experimental results. The predicted values of partition coefficient will help in the screening and thus selection and design of suitable ILs prior to solvent extraction experiments.

With the development of industries, an increase in the discharge of toxic effluent has been observed which causes detrimental effects on living creatures and the environment. This study is mainly focused on estimation methods of hexavalent chromium in drinking water samples and their comparison. The study area is the state of Gujarat in India, and touches South Gujarat where industries have proliferated. In the present work, a comparative study has been done using two different methods for the estimation of hexavalent chromium in drinking water. The results show that chelation extraction method (CEM) is better as compared to direct aspiration method (DAM). Furthermore, we have established that the hexavalent chromium content in drinking water samples collected from the South Gujarat area is several folds higher as compared to the permissible limits suggested by Public Health Goal which is 0.02 ppb.

Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′ N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007. Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered by long-term changes in climate.

We report density functional theory (DFT) based study to predict various conformation of free 12-crown-4 ether and its complexes with alkali metal cations. The optimized geometries, binding energies, and binding enthalpies of crown ether–cation complexes have been determined with a correlated hybrid density functional, namely Becke’s three-parameter functional, B3LYP using split valence basis function, 6-311++G(d, p). Geometry optimizations for all the conformers of free 12-crown-4 ether and its metal cation complexes are carried out with several initial guess structures based on semi-empirical PM3 optimized results. The optimized structure for free 12-crown-4 ether and its metal cation complexes obtained from the present DFT calculation confirmed the experimentally reported structures. The calculated values of the gas phase binding energy for lithium ion is always found to be higher than that of the sodium ion for all the conformers of macrocyclic 12-crown-4 ethers reported in the present study. Expected...

An experimental helium refrigerator/liquefier is being designed and developed by Cryo-Technology Division to be installed at Bhabha Atomic Research Centre, Mumbai. During first trial runs, certain limitations of the process were observed and some other fabrication/development issues came to light. After detailed steady state cycle simulation studies, it was decided to undertake some major modifications to achieve the target of about 200W refrigeration capacity at around 4.7K. The most significant modification involved changing the basic thermodynamic cycle from Collins to a modified Claude cycle which is more suited to turboexpanders. To this effect, simulation studies on the new cycle, with two turboexpanders in series interspaced with a multi stream heat exchanger, was taken up and the process computed. The present paper aims to describe in details different studies taken up on the helium refrigerator. It also aims to provide an update on the present status of development of the helium refrigerator/liquefier.

Crown ether architectures were explored for the inclusion of Cs(+) and Sr(2+) ions within nano-cavity of macrocyclic crown ethers using density functional theory (DFT) modeling. The modeling was undertaken to gain insight into the mechanism of the complexation of Cs(+) and Sr(2+) ion with this ligand experimentally. The selectivity of Cs(+) and Sr(2+) ions for a particular size of crown ether has been explained based on the fitting and binding interaction of the guest ions in the narrow cavity of crown ethers. Although, Di-Benzo-18-Crown-6 (DB18C6) and Di-Benzo-21-Crown-7 (DB21C7) provide suitable host architecture for Sr(2+) and Cs(+) ions respectively as the ion size match with the cavity of the host, but consideration of binding interaction along with the cavity matching both DB18C6 and DB21C7 prefers Sr(2+) ion. The calculated values of binding enthalpy of Cs metal ion with the crown ethers were found to be in good agreement with the experimental results. The gas phase binding enthalpy for Sr(2+) ion with crown ether was higher than Cs metal ion. The ion exchange reaction between Sr and Cs always favors the selection of Sr metal ion both in the gas and in micro-solvated systems. The gas phase selectivity remains unchanged in micro-solvated phase. We have demonstrated the effect of micro-solvation on the binding interaction between the metal ions (Cs(+) and Sr(2+)) and the macrocyclic crown ethers by considering micro-solvated metal ions up to eight water molecules directly attached to the metal ion and also by considering two water molecules attached to metal-ion-crown ether complexes. A metal ion exchange reaction involving the replacement of strontium ion in metal ion-crown ether complexes with cesium ion contained within a metal ion-water cluster serves as the basis for modeling binding preferences in solution. The calculated O-H stretching frequency of H(2)O molecule in micro-solvated metal ion-crown complexes is more red-shifted in comparison to hydrated metal ions. The calculated IR spectra can be compared with an experimental spectrum to determine the presence of micro-solvated metal ion-crown ether complexes in extractant phase.

Cetirizine, a derivative of hydroxyzine, is a new compound with potent antihistaminic property without antiserotonin and anticholinergic activities. The effect of both a single dose (15 mg) and 7 days of treatment (15 mg twice daily) with cetirizine, a potent H1 antagonist on bronchoconstriction induced by histamine and leukotriene D4 (LTD4) has been examined in 10 patients with mild atopic asthma in a placebo-controlled, double-blind, crossover study. Cetirizine, after a single dose and 7 days of treatment with placebo, the geometric mean values of the provocative concentration of histamine causing a 20% fall in FEV1 (millimolars) were 1.60 (95% confidence interval, 0.82 to 3.11) and 1.67 (0.77 to 3.65), compared with 118.07 (77.22 to 180.54) (p less than 0.0001) and 53.16 (20.50 to 137.84) after cetirizine administration (p less than 0.0002). The mean inhibition after a single dose was twofold higher than after 1 week of treatment (p less than 0.05). After a single dose and 7 days of treatment with placebo, the geometric mean values of the provocative concentration of LTD4 causing a 20% fall in FEV1 (micromolars) were 2.26 (1.74 to 2.94) and 2.37 (1.77 to 3.17), compared with 3.90 (2.60 to 5.86) (p less than 0.05) and 3.21 (2.28 to 4.52) after cetirizine administration. This result suggests that cetirizine is a potent H1 antagonist in the human airways. Diminished activity after 1 week of treatment suggests subsensitivity of H1 receptors developing in human airways. The small protective effect after a single dose against LTD4-induced bronchoconstriction indicates a nonspecific rather than a specific receptor antagonism.

The authors examined biomarkers for environmental tobacco smoke exposure (ETS) from bidis (Indian cigarettes) among male smokers, their nonsmoking female family members (passive smokers), and an unexposed control group (N = 66). The 3 parameters used to determine the magnitude of exposure were cotinine (a tobacco-specific alkaloid indicating nicotine exposure) and thioethers and glucuronides (indicators of electrophilic burden). Urinary excretion of cotinine was significantly higher among active smokers (4.30 +/- 1.18), compared with passive smokers (wives = 1.76 +/- 0.50; daughters = 0.50 +/- 0.26). Similar trends were noted for thioethers and glucuronides. The authors found that cotinine and glucuronide levels were correlated significantly with exposure to ETS among both active and passive bidi smokers.