A new selective adsorbent was prepared by the acid treatlnent of Li1.33Mn1.67O4 with spinel structure, followed by granulation with PVC as a binder. The absorbent showed the highest capacities for lithium from seawater; the equilibrium lithium uptakes reached 25.5mg·g-1 by the powdered adsorbent and 18 mg·g-1 by the granulated one at 25°C. The column adsorption study with the granulated adsorbent (diameter 0.7-1.4mm) showed that the lithium uptake reached about 14 mg°g-1 by passing seawater for 30 days. This lithium content is nearly equal to that of lithium ore. Although the lithium adsorption capacity of the granulated adsorbent decrensed slightly by repeating the adsorption-desorption cycle, it kept a high capacity as well as a high strength against abrasion during the repetition of 10 cycles.
The desorption properties of lithium was investigated by both a batch and a column method using granulated adsorbent (diameter 0.7-1.0 mm) with a lithium content of 16.5 mg·g-1 at 25°C. The batch study showed that 83% of lithium was desorbed by treatment with a 0.5 N HCl solution for 1 h. A little amount (1%) of manganese was dissolved during the acid treatment. A solution containing 2,100 mg·dm-3 lithium was obtained by a multistage desorption (5 stages). The column desorption study showed that the elution curves varied depending on HCl concentration. More than 92% of the adsorbed-lithium was eluted by passing a 0.5 N HCl solution with a volume of 1.5 time that of the adsorbent. The lithium concentration of the eluate reached 1,400 mg·dm-3. Alkaline earth metal ions and the other alkali metal ions in the adsorbent were also eluted to the HCl solution at nearly the same retention time as that of lithium
Dyes in pickles are extracted from aqueous solutions as ion-pairs with a series of amine such as tri-n-octylamine (TOA), tri-iso-octylamine (TiOA), di-n-octylamine (DOA), and tri-n-hexylamine (THA) in chloroform. The influences of pH and the concentrations of sodium chloride and the amines on the extraction were examined. The equilibrium is attained in 2 min or less. The extractability of amines for tartrazine was in the order TOA>THA>DOA>TiOA. Tartrazine, sunset yellow and sorbic acid are separated from pickles by elution with aqueous ammonia system. The extract was purified by ion-pair extraction with TOA, and the dyes and sorbic acids were analyzed by high-performance liquid chromatography. The detection limits were approximetely 2.0, 1.0 and 0.5 μg cm-3 for tartrazine, sunset yellow, and sorbic acid, respectively.
The cation-exchange characteristics of Na-substituted taeniolite (NaT) and Na-substituted hectorite (NaH) for Cs+ were investigated in aqueous solutions at 25°C. These synthetic fluoromicas swell in water. Cs+ exchange reaction on NaT appeared to attain steady states within 8 h. The most uptake amount of Cs+ on NaT was 1.15 mmol/g. The Na+⇔Cs+ exchange isotherm on NaT rose steeply and reached a plateau above the diagonal line in the lower concentration region. It was found that NaT had high selectivity for Cs+ in the low concentration region of Cs+. The distribution coefficient, Kd, for Cs+ on NaT under a large excess of Na+ or Ca2+ was 4.7×104ml/g and 3.1×106ml/g, respectively. NaT takes up Cs+ from mixed solutions of large amount of Na+ or Ca2+and small amount of Cs+. These results suggest that NaT is useful for separation and immobilization of Cs+.