Some features of crystalline α-titanium hydrogenphosphate, modified sodium and n-butylammonium forms and thermodynamics of ionic exchange with K+ and Ca2+

Two Independent Routes to Synthesize Identical Silicas by Grafting Ethylenimine or 2-Aminoethanethiol, Their Cation Adsorbing Abilities, and Thermodynamic Data

“…An initial 1.0% of weight loss in the 298 to 473 K range is attributed to the water physically adsorbed on surface. The following mass loss, up to 1170 K, is related to the condensation of free silanol groups on the surface to form siloxane groups (27,29). For compound ≡Sil-Cl three stages of mass losses are shown.…”

“…The modified surface containing two basic centers composed of sulfur and nitrogen donor atoms, are potentially available as chelating moieties to complex cations such as copper, nickel, and cobalt from aqueous solution (8,9,27,28). The results of the adsorption of these cations on modified surfaces are presented in the Table 1.…”

“…Calorimetry is a suitable technique to obtain information about the interactions of cations with organofunctionalized silicas even though, when this kind of measurement is provided in heterogeneous conditions, the interaction has occurred at a solid/liquid interface of a suspension of the grafted silica gel surface in water (9,27,30,32).…”

“…Under the same experimental conditions, the corresponding thermal effect of the dilution of the cation solution was obtained in the absence of the support (Qd). The thermal effect of the hydration of the immobilized silica in water was determined as before (9,26,27). Under such experimental condition the net thermal effect of adsorption ( Qr), was obtained through the equation:…”

Cation Exchange and Sorption Properties of Crystalline α-Titanium(IV) Phosphate

“…The free energy changes for the metal ion-H + exchange as a function of the radius of the ingoing cation show a departure from a linear relationship. This behavior is interpreted in terms of increasing distortion of the ion-exchanger matrix with size of the in-coming ion (40)(41)(42).…”