Ramesh Chitrakar

Synthetic inorganic ion-exchange materials. XLV. Recovery of lithium from seawater and hydrothermal water by titanium (iv) antimonate cation exchanger

Abstract The unusual selectivity for lithium ions shown by titanium (IV) antimonate cation exchanger (TiSbA) can be successfully applied for the recovery of lithium ions from seawater and hydrothermal water. The effects of the presence of other ions such as those of potassium, calcium and magnesium on the adsorption of lithium ions on TiSbA were investigated by a batch technique. The lithium adsorption decreased significantly with increasing the concentrations of K+, Mg2+ and Ca2+. The presence of silica has no effect on the adsorption of lithium from hydrothermal water. The enrichment of lithium ions from seawater and hydrothermal water was carried out on TiSbA columns. Adsorbed lithium can be eluted with nitric acid solution as eluent. Therefore, the TiSbA exchanger can be used repeatedly for the separation of lithium ions from seawater and hydrothermal water.

Synthetic inorganic ion exchange materials XLVII. Preparation of a new crystalline antimonic acid HSbO3.O.12H2O

A new crystalline antimonic acid HSbO3.O.12H2O was prepared by Li+H+ ion exchange reaction with concentrated nitric acid solution from LiSbO3. The LiSbO3 was obtained by heating LiSb(OH)6 at 900°C. The LiSb(OH)6 was prepared by the addition of LiOH solution to a Sb(V) chloride solution at 60°C. X-ray diffraction pattern of HSbO3.O.12H2O was indexed to a monoclinic cell (space group P21m or P21) with a=8.676 A, b=4.752 A, c=5.263 A and β=90.75°. This material showed equivalent exchange reaction of alkali metal ion to one proton per one antimony atom and a high ion exchange capacity for Li+ among the alkali metal nitrate solutions studied. This result suggests that lithium insertion/extraction reactions should lead to new types of lithium selective ion exchangers.

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS XXXIX. SYNTHESIS OF TITANIUM(IV) ANTIMONATES AND THEIR ION EXCHANGE PROPERTIES FOR ALKALI AND ALKALINE EARTH METAL IONS

ABSTRACT Titanium antimonate (TiSbA) cation exchanger, prepared under different molar ratios of titanium and antimony, has been characterized by X-ray diffraction, thermal analysis, infrared spectra, and pH-titration. The pH-titration curves showed apparently monobasic acid type. The uptakes of alkali metal ions increased with increasing pH of the solution and with decreasing the molar ratio (Ti/Sb) in the exchanger. An unusual selectivity sequence of the order Na < K < Rb < Cs was found for microamounts of alkali metal ions on TiSbA, while the regular selectivity sequence Mg < Sr < Ba was found for alkaline earth metal ions in nitric acid media. The maximum separation factors, ∝Li Na(=55) and ∝(=186) were found on the TiSbA with Ti/Sb molar ratio of 1.56, respectively. The effective separations of Li from Na and K, Mg from Ca and Sr have been achieved by using a relatively small column (2 cm × 0.5 cm i.d. ) containing TiSbA of Ti/Sb ratio 1.56.

Synthetic inorganic ion-exchange materials. Part XLIX. Adsorption and desorption behaviour of heavy metal ions on hydrated titanium dioxide

The ion-exchange selectivity of a number of divalent metal ions was studied as a function of pH in nitrate and chloride media. The order of selectivity was Pb2+ > Hg2+ > Cd2+ > Mg2+ in nitrate solution and Pb2+ > Cd2+ > Ca2+ > Mg2+ > Hg2+ in chloride solution. A good linear relationship between the logarithm of the distribution coefficient of the heavy metal ions and their effective ionic radius was found. On the basis of the Kd values, the separation of a mixture of Cd2+, Hg2+ and Pb2+ and the group separation of Hg2+ and Pb2+ from several common metal ions were achieved on an ion-exchange column containing amorphous hydrated titanium dioxide.

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XLVIII. ION-EXCHANGE REACTION OF ALKALI METAL IONS/H+ ON MONOCLINIC ANTIMONIC ACID

ABSTRACT The pH titration curves of monoclinic antimonic acid (M-SbA) showed apparently monobasic acid for the systems of alkali metal ions/H+. The uptake order of the metal ions were K+ < Rb+ < Cs+ < Na+ < Li+ throughout the pH range studied. The low uptakes of K+, Rb+, Na+ and Cs+ at high pH might be due to steric or ion sieve effects for large unhydrated cations on M-SbA. Thermodynamic data were derived for Li+/H+ exchange on M-SbA from pH titration curve.

Synthesis and Ion Exchange Properties of Lithium Ion Selective Inorganic Ion Exchanger By Applying Ion Memory Effect

A new crystalline antimonic acid HSbO3O.12H20 was prepared by Li+/H+ ion exchange reaction with concentrated nitric acid solution from LiSb03. The LiSbO3 was obtained by heating LiSb(OH)6 at 900°C. The Li Sb(OH)6 was prepared by the addition of LiOH solution to anSb(V) chloride solution at 60°C. The X-ray diffraction pattern(XRD) of HSbO3O.12H2O was indexed to a monoclinic cell (space group P21/m or P21) with a=8.676 A, b=4.752 A, c=5.263 A and β=90.75°. The pH titration curves of monoclinic antimonic acid (M-SbA) showed apparently monobasic acid for the systems of alkali metal ions /H+. The uptake order of the metal ions are K+ < Rb+ < Cs+ < Na+ < Li+ throughout the pH range studied. The low uptakes of K+, Rb+, Na+ and Cs+ at high pH might be due to steric or ion sieve effects for large unhydrated cations on M-SbA. Thermodynamic data were derived for Li+/H+ exchange on M-SbA from pH titration curve.