Sangita Pal

Polyhydroxamic Acid Sorbents for Uranium Recovery

Crosslinked polyacrylamides were synthesized by solution polymerization using benzoyl peroxide as the radical initiator. The water–insoluble polymer obtained was functionalized by reacting with hydroxylamine to convert the amide group into hydroxamic acid group. The resultant functionalized polymer was characterized in terms of moisture uptake, elemental composition, IR spectra, thermal stability, exchange capacity and heavy metal sorption. The sorbent, obtained in particulate form, was investigated for its sorption properties with respect to uranium from uranyl nitrate solutions under unstirred batch conditions. This paper will concentrate on preparation, characterization and performance evaluation with respect to uranium sorption as a function of concentration, time, solution pH and temperature. The potential of this sorbent for uranium and other heavy metal ion recovery from sea water is ascertained.

Strategy of deriving 'wealth from waste' from concentrated brine of desalination plant

Research and technological developments are being pursued vigorously all over the world to reduce the cost of desalinated water. Thermal and membrane-based desalination processes are very well known and plants are being operated to augment the demand of fresh water essential for drinking in water-scarce countries and to sustain the industrial processes. Any further improvement in energy reduction can only be marginal considering the complexity of the desalination system. The alternative approach is to add value by recovering edible salt, rare and valuable metals, such as caesium, titanium, uranium and vanadium, from the reject brine streams. In this regard, a novel polymeric chelating resin was designed and developed in Desalination Division, BARC laboratory with significant potential for this achievement. In this paper, the characteristics and potential of the resin have been described for the recovery of valuable elements based on experimental findings.

Uranium Permeation from Nitrate Medium Across Supported Liquid Membrane Containing Acidic Organophosphorous Extractants and their Mixtures with Neutral Oxodonors

Permeation of U(VI) from nitric acid solution has been studied across supported liquid membrane (SLM) using bis[2,4,4 trimethyl pentyl] phosphinic acid (Cyanex 272) either alone or in combination with neutral donors like Cyanex 923 (a mixture of four trialkyl phosphine oxides viz. R3PO, R2R′PO, RR′2PO, and R′3PO where R: n-octyl and R′: n-hexyl chain), TBP (tri-n-butyl phosphate), and TEHP (tris-2-ethylhexyl phosphate) dissolved in n-paraffin as carriers. Effect of various other parameters such as nature and concentration of receiver phase, feed acidity, uranium concentration, pore size, and membrane thickness on U(VI) transport across SLM were investigated. Transport behavior of U(VI) was also compared with other derivatives of phosphoric acids like 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A), dinonyl phenyl phosphoric acid (DNPPA) under identical conditions and it followed the order: Cyanex 272 > PC88A > DNPPA. 2 M H2SO4 was suitable for effective U(VI) transport across SLM. Presence of neutral donors in carrier showed significant enhancement in U(VI) permeation in the order: Cyanex 923 > TBP > TEHP. U(VI) transport decreased with increased membrane thickness as well as decrease in pore size. The optimized conditions were tested for recovery of U(VI) from uranyl nitrate raffinate (UNR) waste generated during purification of uranium.

Mössbauer spectroscopic study of iron-chelate trammels

Any kind of waste effluent in the Indian context and other countries contains a lot of iron in any ore. During mining, milling, extraction and purification process iron acts as contaminant towards other metal’s purity. It is essential to remove iron to the maximum extent. In this case, an “IN-HOUSE” resin polyacrylamidehydroxamic acid (PHOA) has been designed and developed which is highly hydrophilic three dimensionally cross-linked. It has an excellent iron binding capacity with almost no leaching. Interaction of resin with ammonium ferrous sulphate and red-mod (Fe2O3) is studied using Mossbauer spectroscopy.

Separation and Recovery of Uranium from Wastewater Using Sorbent Functionalized with Hydroxamic Acid

A newly developed hydroxamic acids functionalized acrylic based solid phase sorbent, named as poly-acryl hydroxamic acid (PHOA) is used as an extractant for the recovery of uranium from nuclear waste solution. Various parameters such as sorbent solubility in different medium, effect of various cations on U(VI) sorption, desorption performance of different eluents with respect to U(VI) sorption has been investigated in detail. U(VI) sorption behaviors of the sorbent were studied in different concentration of competitive ions such as Mg2+, Fe3+, and NO3− and it was found that the sorbent was capable of removing the U(VI) efficiently in the presence of high concentration of these ions.

Feasibility study of novel sorbent for chromium sequestration and enhanced immobilization

ABSTRACT The present solid phase sorption studied for the treatment of water containing mainly chromium by “In-house” synthesized specific amphoteric chelator have been evaluated w.r.t. basic parameters like concentration, time, and elution etc. High uptake values of the metal ions proves its selectivity, whereas negligible elution or high immobilization factor (0.97) confirm further decontamination of run-off water during natural calamities. This polymeric ligand exchanger displayed minimum and maximum level sorption of 41.2% and 99.6% at the feed concentration of 50 and 500 ppm respectively.

Selection and design criteria of supported liquid membrane for the treatment of rad-waste

Supported Liquid Membrane (SLM) is an emerging trace metal pre-concentration technique. It has the ability to decontaminate radionuclides even from lean secondary effluent. SLM can be considered as a part of process intensification, which implies a closed loop operation. It has reduced space requirement as well as minimised secondary effluent generation and the number of unit steps. Proper selection of molecular design criteria helps in deciding performances such as selectivity, compatibility, permeability, etc., that is attributed to both feed and desired strippant characteristics, and great effort has been applied for nuclear plant waste treatment generated in the uranium metal plant of Trombay, India. This paper articulates basic views of SLM, selection of carrier by experimental verification with respect to both feed and strippant for further processing, and structural aspects with evidences (from FT-IR studies).

DPASV analytical technique for ppb level uranium analysis

Determining uranium in ppb level is considered to be most crucial for reuse of water originated in nuclear industries at the time of decontamination of plant effluents generated during uranium (fuel) production, fuel rod fabrication, application in nuclear reactors and comparatively small amount of effluents obtained during laboratory research and developmental work. Higher level of uranium in percentage level can be analyzed through gravimetry, titration etc, whereas inductively coupled plasma-atomic energy spectroscopy (ICP-AES), fluorimeter are well suited for ppm level. For ppb level of uranium, inductively coupled plasma - mass spectroscopy (ICP-MS) or Differential Pulse Anodic Stripping Voltammetry (DPASV) serve the purpose. High precision, accuracy and sensitivity are the crucial for uranium analysis in trace (ppb) level, which are satisfied by ICP-MS and stripping voltammeter. Voltammeter has been found to be less expensive, requires low maintenance and is convenient for measuring uranium in presence of large number of other ions in the waste effluent. In this paper, necessity of uranium concentration quantification for recovery as well as safe disposal of plant effluent, working mechanism of voltammeter w.r.t. uranium analysis in ppb level with its standard deviation and a data comparison with ICP-MS has been represented.Determining uranium in ppb level is considered to be most crucial for reuse of water originated in nuclear industries at the time of decontamination of plant effluents generated during uranium (fuel) production, fuel rod fabrication, application in nuclear reactors and comparatively small amount of effluents obtained during laboratory research and developmental work. Higher level of uranium in percentage level can be analyzed through gravimetry, titration etc, whereas inductively coupled plasma-atomic energy spectroscopy (ICP-AES), fluorimeter are well suited for ppm level. For ppb level of uranium, inductively coupled plasma - mass spectroscopy (ICP-MS) or Differential Pulse Anodic Stripping Voltammetry (DPASV) serve the purpose. High precision, accuracy and sensitivity are the crucial for uranium analysis in trace (ppb) level, which are satisfied by ICP-MS and stripping voltammeter. Voltammeter has been found to be less expensive, requires low maintenance and is convenient for measuring uranium in prese...

Pre-concentration technique for reduction in “Analytical instrument requirement and analysis”

Availability of analytical instruments for a methodical detection of known and unknown effluents imposes a serious hindrance in qualification and quantification. Several analytical instruments such as Elemental analyzer, ICP-MS, ICP-AES, EDXRF, ion chromatography, Electro-analytical instruments which are not only expensive but also time consuming, required maintenance, damaged essential parts replacement which are of serious concern. Move over for field study and instant detection installation of these instruments are not convenient to each and every place. Therefore, technique such as pre-concentration of metal ions especially for lean stream elaborated and justified. Chelation/sequestration is the key of immobilization technique which is simple, user friendly, most effective, least expensive, time efficient; easy to carry (10g - 20g vial) to experimental field/site has been demonstrated.