Batch equilibration studies are conducted to determine the nature of adsorption of zinc (II) over chitosan. The factors affecting the adsorption process like particle size, contact time, dosage, pH, effects of chloride and nitrate are identified. The influence of temperature and co-ions on the adsorption process is verified. The fraction of adsorption, Y t and the intraparticle diffusion rate constant, k p are calculated at different environments and the results are discussed. The nature of adsorption of the zinc (II)-chitosan system is explained using Freundlich, Langmuir isotherms and thermodynamic parameters.

Adsorption of ferric ions by chitin was studied by the batch equilibration method. The influence of particle size and dosage of the adsorbant, contact time, initial concentration of the adsorbate and temperature were experimentally verified. The effect of anions like chloride, nitrate and sulphate and also of cations like zinc, chromium and copper on the adsorption of iron(III) was determined. The time dependence of fraction of adsorption, Y t , at varying particle sizes and doses of chitin and the intraparticle diffusion rate constants, k p , of the adsorption process were calculated. Thermodynamic and equilibrium parameters of the reaction were determined to understand the sorption behaviour of chitin. The results revealed that the adsorption of iron(III) by chitin is spontaneous, endothermic and favourable.

Ferromagnetic Sn–TiO2 nanocrystals were newly developed, and their photocatalytic activity showed structural, luminescent and magnetic dependences.

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For reactions involving electron transfer or nucleophilic attack on the transition state/excited state of metal complex in aquo-organic solvent mixtures, a linear relationship between logarithms of rate constant and solvent empirical parameters can be derived. The relationship, Y S ) Y 0 + a 1 X 1 + a 2 X 2 + ... + a n X n , fits well for both the measured quantity in a solvent and solvent dependent property. From the quantitative estimation of the coefficients, the dominant solvent stoichiometric and other substantial medium effects on reactivities can be confirmed. Electron-transfer reaction of Co(NH 3 ) 4 ox + complex with Fe(CN) 6 4in six different watercosolvent binary mixtures have been investigated (cosolvent: methanol or 1,4-dioxane 5-30% (v/v)) and the respective k et and K IP values have been experimentally determined. The k et values evaluated in mixed solvents show linearity with x org and r -1 , reflecting the individuality of the cosolvent and thereby suggesting that the relative stability of the ion pair is governed by the preferential solvation effect. The thermodynamic parameters (∆H # , ∆S # , and ∆G # ) are sensitive to the structural changes in the bulk solvent phase. Likewise, irradiation (at 254 nm) of the charge-transfer bands of Co(NH 3 ) 4 ox + in varying compositions of water-methanol/1,4dioxane mixtures results in reduction of Co(III) to Co(II); with respect to x org , φ Co(II) increases up to 1.6-fold (organic cosolvent 5-30% (v/v)). The predominance of Co(II) formation at higher x org is due to solventassisted reduction in mixture solvents. There is a linear relationship between φ Co(II) with r -1 of the medium indicating the solvational contributions. The experimentally determined k et and φ Co(II) are well correlated through multiple regression equations based on proposed models to understand the consequences of short range and long-range solvation effects. A quantitative estimation of relative importance of the components is attempted. A number of empirical solvent parameters are used in the multiple regression equations. The correlation analysis reveals significant information on the effect of solvent-solvent and solvent-solute interactions on reactivities. The investigation is a novel attempt to understand the "solvent tuning" of reactions and to obtain a quantitative measure of the relative importance of the influences of solvents.