Magnetic Resonance Spectra and Statistical Geometry

Methods of statistical geometry are introduced which allow one to estimate, on the basis of computable criteria, the conditions under which maximally informative data may be collected. We note the important role of constraints which introduce curvature into parameter space and discuss the appropriate mathematical tools for treating curvature effects. Channel capacity, a term from communication theory, is suggested as a useful figure of merit for estimating the information content of spectra in the presence of noise. The tools introduced here are applied to the case of a model nitroxide system as a concrete example, but we stress that the methods described here are of general utility.     

Alkanolamide as an accelerator,filler-dispersant and a plasticizer in silica-filled natural rubber compounds

A feasibility study was carried out on the utilization of Alkanolamide (ALK) on silica reinforcement of natural rubber (NR) by using a semi-efficient cure system. The ALK was incorporated into the NR compound at 1.0, 3.0, 5.0, 7.0 and 9.0 phr. An investigation was carried out to examine the effect of ALK on the cure characteristics and properties of NR compounds. It was found that ALK gave shorter scorch and cure times for silica-filled NR compounds. ALK also exhibited higher torque differences, tensile modulus, tensile strength, hardness and crosslink density of up to 5.0 phr of ALK loading, and then decreased with further increases of ALK loading. The resilience increased with increased ALK loading. Scanning electron microscopy (SEM) micrographs proved that 5.0 phr of ALK in the silica-filled NR compound exhibited the greatest matrix tearing line and surface roughness due to higher reinforcement level of the silica, as well as better dispersion and cure enhancement.     

First principles study and database analyses of structural preferences for sodium ion (Na+) solvation and coordination

Extensive computations were performed on aqueous clusters of monovalent sodium cation [Na⁺(H₂O) _n ; (n = 1–20)] using MP2/cc-pVTZ and density functional theory. The structure, energy, and coordination number (CN) preference of a large number of competing conformations of different complexes have been explored. For complexes up to n = 12, the CN 4 is most preferred while 5, 6 CNs are favored in case of larger complexes containing up to 20 water molecules. These results are in very good agreement with experimental observations. The strength of hydrogen bonding among the waters coordinated to the Na⁺ ion is found to play a major role in the stability of the complexes. The varying preferences for CN of Na⁺ ion were explored by screening two important databases: Protein Databank and Cambridge Structural Database. A linear correlation is observed between the M (Metal)–O distance and the charge on metal ion in complex with the increase in CN of metal ion.     

Removal of cadmium(II) and zinc(II) metal ions from binary aqueous solution by rice husk ash

The present study reports the competitive adsorptive removal of cadmium (Cd(II)) and zinc (Zn(II)) ions from binary systems using rice husk ash (RHA), a waste obtained from the rice husk-fired furnaces, as an adsorbent. The initial pH (pH₀) affects significantly the capacity of RHA for adsorbing the metallic ions in the aqueous solution. The pH₀ ≈ 6.0 is found to be the optimum for the removal of Cd(II) and Zn(II) ions by RHA. The single ion equilibrium adsorption from the binary solution is better represented by the non-competitive Redlich–Peterson (R–P) and the Freundlich models than by Langmuir model in the initial metal concentration range of 10–100 mg/l. The adsorption of Zn(II) ion is more than that of Cd(II) ion, and this trend is in agreement with the single-component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined effect of Cd(II) and Zn(II) ions on RHA is generally found to be antagonistic. Non-modified Langmuir, modified Langmuir, extended-Langmuir, extended-Freundlich, Sheindorf–Rebuhn–Sheintuch (SRS), non-modified R–P and modified R–P adsorption models were tested to find the most appropriate competitive adsorption isotherm for the binary adsorption of Cd(II) and Zn(II) ions onto RHA by minimizing the Marquardt's percent standard deviation (MPSD) error function. The extended-Freundlich model satisfactorily represents the adsorption equilibrium data of Cd(II) and Zn(II) ions onto RHA.     

Treatment of pulp and paper mill wastewaters with poly aluminium chloride and bagasse fly ash

The present study deals with the use of poly aluminium chloride (PAC) as a coagulant and bagasse fly ash (BFA), which is generated in sugar mills, as an adsorbent for the removal of chemical oxygen demand (COD) and colour of pulp and paper mill effluents. Under optimal conditions of pH 3 and initial PAC dosage of 3 g/l, about 80% COD removal and 90% colour removal were obtained. The optimal conditions for the adsorptive removal of COD and colour with BFA were pH 4 and BFA dosage of 2 g/l. Under these conditions, COD and colour removal were, respectively, 50 and 55%. Adsorptive removal of COD by BFA followed second-order kinetics. Intra-particle diffusion was found to be rate controlling. Freundlich and Langmuir adsorption isotherms were found to fit the equilibrium adsorption data with BFA. Two-stage treatment using PAC (3 g/l) as a coagulant in the first stage and BFA (2 g/l) as an adsorbent in the second stage gave the combined COD and colour removal of nearly 87 and 95%, respectively, for different effluents without any pH adjustment. Two-stage adsorptive treatment using BFA (2 g/l) in both the stages gave a combined COD and colour removal of about 70%. The sludge obtained can be dewatered by centri-clarifiers, dried, briquetted and incinerated to recover its energy content.     

Fixed-bed study for adsorptive removal of furfural by activated carbon

In our previous study [A.K. Sahu, V.C. Srivastava, I.D. Mall, D.H. Latye, Sep. Sci. Technol. 43 (5) (2008) 1239], commercial grade activated carbon (ACC) was used for adsorptive removal of furfural from aqueous solution using batch studies. In the present study, continuous fixed-bed adsorption was carried out in ACC packed bed for the removal of furfural from aqueous solution. The effects of important factors namely bed height (Z = 15–60 cm), influent concentration of furfural (C_o = 50–200 mg/l), the flow rate (Q = 0.02–0.04 l/min) and column diameter (D = 2–4 cm) were studied. Capacity of the bed to adsorb furfural was found to increase with an increase in the value of Z, C_o and D; and with decrease in the value of Q. Adams–Bohart, Bed-Depth Service-Time, Thomas, Yoon–Nelson, Clark and Wolborska models were applied to the experimental data for the prediction of the breakthrough point, and to determine the characteristic parameters of the column. Error analysis showed that the Yoon–Nelson model best described the experimental breakthrough curve, while Wolborska model showed good prediction of breakthrough curve for the relative concentration region up to 0.5.