PubMed · 13004321
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
G LISI. 1952-10-15. [Ion-exchange resins].. https://pubmed.ncbi.nlm.nih.gov/13004321/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Ion-exchange resins (IER) offer alternative approaches to measuring ionic movement in soils that may have advantages over traditional approaches in some settings, but more information is needed to understand how IER compare with traditional methods of measurement in forested ecosystems. At the Bear Brook Watershed in Maine (BBWM), one of two paired, forested watersheds is treated bi-monthly with S and N (28.8 and 25.2kg ha(-1)yr(-1) of S and N, respectively). Both IER and ceramic cup tension lysimeters were used to study soil solution responses after approximately 11 years of treatment. Results from both methods showed treatments resulted in the mobilization of base cations and Al, and higher SO(4)-S and inorganic N in the treated watershed. Both methods indicated similar differences in results associated with forest type (hardwoods versus softwoods), a result of differences in litter quality and atmospheric aerosol interception capacity. The correlation between lysimeter and IER data for individual analytes varied greatly. Significant correlations were evident for Na (r=0.75), Al (r=0.65), Mn (r=0.61), Fe (r=0.57), Ca (r=0.49), K (r=0.41) and NO(3)-N (r=0.59). No correlation was evident between IER and soil solution data for NH(4)-N and Pb. Both IER and soil solution techniques suggested similar interpretations of biogeochemical behavior in the watershed.
Crystalline phases of Ti(IV) tungstosilicate and Ti(IV) tungstophosphate have been synthesised. The ion-exchange capacities of Ti(IV) tungstosilicate and Ti(IV) tungstophosphate have been reported as 0.44 and 0.80 mequiv./g, respectively. Both materials show monofunctional ion-exchange characteristic and are stable in 0.1 M solutions of HNO3, HCl, H2SO4 and acetone and benzene. Ti(IV) tungstosilicate is found to be more stable thermally than Ti(IV) tungstophosphate (loss in ion-exchange capacity was found as 58 and 80%, respectively for samples heated at 200 degrees C). The Kd values for heavy metals such as Pb, Hg, Cd, Sb, Co, Zn, Ni, Fe, Cr etc. have been reported in demineralised water and two surfactant media by batch processes. Cr3+, Fe3+ and Sn4+ are totally adsorbed on both the materials in demineralised water while a decrease in Kd value with increase in concentration of two surfactants is reported. On the basis of Kd values for metal ions, thirteen binary separations and five ternary separations on Ti(IV) tungstosilicate and thirteen different binary separations and four different ternary separations on Ti(IV) tungstophosphate have been achieved. Separation of methylamine from ethylamine has been done by GC on a column packed with Ti(IV) tungstophosphate.
Biodegradable, dextran-based ion-exchange microspheres (IE-MS) have been used for localized delivery of anticancer drugs and chemosensitizers. Because of their hydrophilic nature, the IE-MS release their payload quickly. The purpose of this work was to develop an IE-MS system that could provide a broad range of release rates for in vitro and in vivo applications. Sulfopropylated dextran microspheres (SP C25 MS) were surface-modified by acylation. These hydrophobically modified sulfopropylated dextran microspheres (HM-MS) were further coated with the cationic acrylic polymer Eudragit RL100 (EU-MS). The changes in chemical composition after the surface modification and coating were characterized by X-ray photoelectron spectroscopy. The effects of the modification and coating on the surface hydrophobicity, equilibrium swelling, surface morphology, and drug loading capacity were investigated. The HM-MS showed little change in swelling and functionality, despite significantly increased affinity to oil and carbon content on the surface. The coated microspheres (EU-MS) exhibited a profoundly decreased swelling ratio, an even higher affinity to oil, a higher loading capacity, and a lower drug release rate. Through further coating of the EU-MS with different amounts of corn oil, the rate of drug release could be tailored to cover a relatively wide range. These results suggest that a versatile delivery system with various release profiles can be prepared by a combination of hydrophobic modification, polymer coating, and oil coating.