Jayshree Ramkumar

Transport of uranyl ion across a bulk liquid membrane using calixarene and synergistic agents as carriers

Transport of uranyl ion across a bulk liquid membrane using chloroform solutions of calixarenes (as carriers) has been studied. Various factors that affect the transport have been optimised in order to obtain maximum transport. It has been observed that the use of tri-n-octyl phosphine oxide (TOPO) as a synergistic reagent showed a marked enhancement of transport of uranyl ion. Crown ether 18 Crown 6 (18C6) also exhibited synergistic behaviour when used in combination with calixarenes. The use of these synergistic reagents resulted in high transport of uranyl ion with 0.1 M nitric acid as the receiving solution. The interference from different transition metal ions was found to be negligible. The serious interference from Th(IV) could be minimised by using EDTA as masking agent. A possible application of this carrier system and transport process to the pre concentration and recovery of uranium from seawater has also been examined.

Selective permeation of Cu2+ and UO22+ through a Nafion ionomer membrane

Abstract The selective permeation of Cu 2+ and UO 2 2+ in the presence of common cations through a Nafion 117 ionomer membrane have been studied. EDTA served as a receiving agent for an effective permeation of Cu 2+ , whereas the same has been used as masking agent for Fe 3+ , Cu 2+ , Ni 2+ and Zn 2+ during the selective permeation of UO 2 2+ using Na 2 CO 3 or Tiron as a receiving solution. Selective permeation of Cu 2+ from a mixture of Fe 3+ and Cu 2+ after masking Fe 3+ with F − , SCN − and PO 4 3− was studied in detail. A lowering of permselectivity and the permeation of anions has been attributed to the simultaneous permeation of Fe 3+ through metal speciation.

Serendipitous discovery of super adsorbent properties of sonochemically synthesized nano BaWO4

The superior adsorbent properties of BaWO4 nanostructures have been reported for the first time. Flower shaped aggregates (∼250 nm) of BaWO4 nanoparticles, having an average size of ∼10–15 nm with a high surface area of ∼148.0 ± 0.2 m2 g−1, have been synthesized sonochemically and used for the adsorption of various cationic dyes from aqueous solutions. The sonochemically synthesized BaWO4 have been characterized by scanning electron microscopy (SEM), selected area electron diffraction (SAED), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The adsorbent capacity of this tungstate is much higher than that reported for other nanomaterials like Fe2O3, MnO2, WO3, etc. Complete removal of dyes like rhodamine B and methylene blue was possible within a short time span of 10–15 minutes. The adsorption process was followed using UV-Visible spectroscopy, while the material before and after adsorption has been characterized using physicochemical and spectroscopic techniques. Various isotherms have been used to fit the data, and kinetic parameters were evaluated. Moreover, the adsorbed dyes could be desorbed completely from nanoparticle surfaces by annealing at moderate temperature and were found to be efficient for multicyclic use. Thus this sonochemically synthesized nano BaWO4 has great significance in treatment of dye industry effluents as a promising adsorbent for cationic dyes from aqueous solution.

Barium borosilicate glass as a matrix for the uptake of dyes

Barium borosilicate (BBS) and sodium borosilicate (SBS) glass samples, prepared by the conventional melt-quench method, were used for the uptake of Rhodamine 6G dye from aqueous solution. The experimental conditions were optimized to get maximum uptake and was found to be 0.4 mg of dye per gram of BBS glass sample. For the same network former to modifier ratio, barium borosilicate glasses are found to have improved extent of uptake for the dye molecules from aqueous solutions compared to sodium borosilicate glasses. Based on 29Si MAS NMR studies on these glasses, it is inferred that significantly higher number of non-bridging oxygen atoms present in barium borosilicate glasses compared to sodium borosilicate glasses is responsible for its improved uptake of Rhodamine 6G dye. 11B MAS NMR studies have confirmed the simultaneous existence of boron in BO3 and BO4 configurations in both barium borosilicate and sodium borosilicate glasses. The luminescence studies have established that the dye molecule is incorporated into the glass matrix through ion exchange mechanism by replacing the exchangeable ions like Na+/Ba2+ attached with the non-bridging oxygen atoms present in the glass.

Crown Ethers as Carriers for the Transport of Anionic Thiocyanate Complex of Uranyl Ion Across a Bulk Liquid Membrane

Transport of UO2+ 2 as its anionic thiocyanate complex [UO2(SCN)4]2− across a bulk liquid membrane using 18 Crown 6 (18C6) and Dibenzo 18 Crown 6 (DB18C6) as carriers in the membrane phase has been studied. The anionic complex is formed by the addition of KSCN to the feed solution at a pH of 1. A dilute acid (pH = 5) served as the stripping agent in the receiving compartment. The interference from Th(IV) and a few other cations could be eliminated by using EDTA as a masking agent in the feed solution. Various factors influencing the transport process have been studied and an uphill transport (>89%) of UO2+ 2 from the feed solution could be accomplished under optimum conditions.

Synthesis, characterization, and metal uptake capacity of a new polyaniline and poly(acrylic acid) grafted sodium alginate/gelatin adsorbent

AbstractThe present work reports the development of new (sodium alginate-gelatin (SAG))-g-poly(acrylic acid)/polyaniline (SAPAPN) from sodium alginate/gelatin blend by cross-linking with glutaraldehyde, followed by grafting with poly(acrylic acid) and polyaniline by free radical polymerization using ammonium persulfate. The structure, thermal stability, and morphology of SAPAPN adsorbent was characterized by Fourier transform infrared spectroscopy, thermo gravimetric analysis, and scanning electron microscopy, and results were consistent with the expected structures. The influence of various experimental conditions like pH, time, and initial feed concentrations on the uptake of metal ions like Cu2+, Ni2+ by SAPAPN adsorbent was tested. It was seen that the adsorption equilibrium data could be fitted to the Langmuir isotherm. Desorption studies were performed in acid media and EDTA, to examine whether the SAPAPN adsorbent can be recycled for the metal ion removal. The results showed that with SAPAPN adsorb...

Facilitated Transport of Alkali Metal Ions Across Bulk Liquid Membrane Containing Phenoxy Compounds as Carrier

The carrier activity of several phenoxy ethers toward the facilitated transport of alkali metal ions through a chloroform bulk liquid membrane has been studied. A brief description of the synthesis of carrier compounds has been given, and the mechanism of transport process has been discussed. The organic carriers are protonated on the receiving side of a permeation cell, and the protons are exchanged with the metal ions at the membrane interphase of the feed side. Protonation of carriers has been confirmed from electronic spectral studies. A high degree of selectivity for Na+ transport has been observed when 1,2-bis-(2-acetyl phenoxy) ethane is used as carrier whereas dibenzo-[a,e]-3,4-dihydroxy-3,4-dimethyl-7,10-dioxocyclodeca-1,5-dione facilitated selective transport of K+.

Transport of some nitrogen heterocyclic and aromatic compounds through metal ion containing Nafion ionomer membrane

Abstract The permeation of some nitrogen heterocyclic bases, such as 1,10-phenanthroline, 2,2′-bipyridyl and 2-aminopyridine, and several aromatic compounds, namely styrene, toluene, nitrobenzene, aniline and biphenyl, through Nafion 117 ionomer membrane in H + , Na + , Cu 2+ and Ag + form has been studied. The permeation fluxes of the organic solutes through the membrane were measured by determining the concentration of the compounds in the sweep solutions using HPLC or flow injection technique. The positive role of metal ions in enhancing the permeation flux has been attributed to the complex formation of the solutes with the metal ions in the membrane. The contribution of the molecular structure of the permeates and steric effects are also discussed. The separation of some binary mixtures under favourable conditions is also shown.

Sorption of dyes and Cu(II) ions from wastewater by sonochemically synthesized MnWO4 and MnMoO4 nanostructures

MnWO4 and MnMoO4 nanoparticles have been synthesized using a facile sonochemical technique. The nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption–desorption measurements. The as-prepared spherical MnWO4 and MnMoO4 nanostructures have a high specific surface area and their excellent adsorbent properties to remove organic pollutants have been demonstrated for the first time. Complete removal of dyes like Rhodamine B and Methylene blue was possible within 2–10 minutes. The influences including initial pH, dosage of adsorbent and contact time have been researched in order to find the optimum adsorption conditions. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. MnWO4 also proved to be a good sorbent for Cu(II) ions. The kinetic modeling for Cu(II) sorption has been discussed. These studies showed that there is a possible application for the complete and fast removal of the organic dyes in the presence of inorganic cations using MnWO4/MnMoO4 sorbents. The thermal regeneration of the sorbents is possible and they show similar adsorption efficiency up to ten consecutive cycles. The sonochemically synthesized MnWO4 and MnMoO4 nanomaterials could serve as promising adsorbents for the removal of organic dyes, especially, cationic dye, and Cu(II) ions from polluted water.

Boroaluminosilicate glasses: novel sorbents for separation of Th and U.

Boroaluminosilicate glass having a specific composition could be successfully used for the selective uptake of thorium from a mixture containing uranium by controlling the solution pH only. Single ion uptake studies showed that the uptake of uranium and thorium was maximum at pH of 4.5 and 7.5, respectively. But uptake studies using mixtures with uranium and thorium showed that irrespective of the pH, the uptake of thorium was higher than that of uranium.