Dayamoy Banerjee

Separation and Recovery of Cs from High Active Waste Simulant using Resorcinol Formaldehyde Polycondensate Resin: Batch and Column Studies

Resorcinol formaldehyde polycondensate resin has been extensively used for the separation of 137Cs from low and medium active alkaline waste solutions. The present study examines the suitability of the resin for separation of Cs from high active solutions. Batch uptake of Cs by RFPR has been evaluated from test solutions containing varying Na (0.6–3.0 M) and Cs (1.00 × 10−4 to 0.10 M) concentrations. Batch results have been used to establish Cs exchange isotherms of the resin and were found to follow Freundlich as well as Dubinin-Radushkevich (D-R) isotherm equations. The loading behavior of Cs on RFPR column has been evaluated by conducting five column runs using different Cs bearing solutions. Based on these results, it is concluded that the D-R equation can be used to predict saturated loading of Cs in the column. The saturation loading of Cs on 1 L bed was estimated to be as high as 13 g and 34 g from feed solution containing Cs concentration 2.57 × 10−4 and 4.30 × 10−3 mol/L respectively. Sequential elution of Na and Cs resulted in a high Cs bearing concentrate containing very low concentration of sodium. This study is relevant in the preparation of gamma source for radiation technology applications after immobilization of the concentrate in glass.

Removal of 137Cs and 90Sr from low-level radioactive effluents by hexacyanoferrate loaded synthetic 4A type zeolite

Copper hexacyanoferrate was imbued on pores of synthetic zeolite and the formation of needle shaped copper hexacyanoferrate microcrystals was confirmed by XRD and SEM. Batch equilibrations showed that the sorbent has good affinity for Cs and Sr which was further confirmed from column studies. It is established that a substantial amount (>8000 bed volumes) of low level waste contaminated with 137Cs and 90Sr can be treated in fixed bed column. The sorbent, owing to its low cost, simple preparation process and excellent 137Cs and 90Sr removal performance, is expected to find wide spread application in nuclear industry.

Denitrification of high sodium nitrate bearing effluents using flow-through bioreactor

ABSTRACT Denitrification of sodium nitrate solution has been studied by isolating biomass, identification of suitable growth medium and finally its use in batch bioreactor. The progress of denitrification of 730 mg/l nitrate as NaNO3 solution has been evaluated for 10 consecutive cycles. The use of harvested cells with gradual increase of nitrate concentration in the batch bioreactor resulted in better acclimatized biomass. Complete denitrifi cation of different concentrations of NaNO3 solution up to 8800 mg/l NO3 – was reached in batch studies. A flow through bioreactor was assembled by growing biomass on to interstices of stainless steel modules and this system was used to study the effects of process variables like C/N ratio, addition of trace elements, etc., on denitrification of high nitrate laden solutions. Based on the gradual acclimatization of biomass to high nitrate bearing solutions, complete denitrification of 12,400 mg/l of nitrate was achieved. Successful demonstration of the process by cont...

Preparation of poly (4-vinylpyridine-DVB) based anion exchangers and its applications on the separation of 99TcO4− ions from reprocessing waste solution

ABSTRACT Three strong-base anion exchange resins were prepared by quaternization of poly(4-vinylpyridine-DVB) with different alkyl (-CH3, -C2H5, and -n-C4H9) halides. The base polymer in granular form was also synthesized in the laboratory. All three synthesized anion exchangers and a conventional strong-base anion exchanger were tested for separation of TcO4 − ions from acidic and alkaline test solutions, each containing 1.0 M NO3 − ions and 99mTc radiotracer. These resins were also evaluated for batch uptake of 99TcO4− ions from actual reprocessing waste solution. Both batch results showed that the resin with n-butyl group on the pyridine nitrogen has higher affinity for 99TcO4 − ions. Further, removal of 99TcO4 − ions from actual reprocessing waste solution was examined using column of poly(4-vinylpyridine-DVB) resin containing n-butyl group on the pyridine nitrogen. Almost complete removal of 99TcO4 − ions was obtained for 150 bed volumes of waste treated, indicating excellent column performance of th...

Removal of radiocesium from low level radioactive effluents by hexacyanoferrate loaded synthetic zeolite: laboratory to pilot plant scale demonstration

Abstract Present paper reports removal of radiocesium from low level waste using a modified sorbent (13X-CFC) prepared by in-situ precipitation of potassium copper hexacyanoferrate(II) inside the macropores of a synthetic zeolite. The Cs exchange isotherm of the sorbent is established and it found to follow Fruendlich absorption isotherm equation. It is varified that presence of hexacyanoferrate on zeolite facilitates rapid Cs uptake performance. This is further confirmed in laboratory scale column tests, wherein excellent Cs removal performance from low level waste simulant was observed even at higher flow rates (40 bed volumes per hour). The utility of the sorbent is established through successful demonstration in a pilot scale (50 L) trial with almost complete removal of 137Cs from more than 14,000 bed volumes of actual low level waste. The sorbent, owing to its low cost and excellent 137Cs removal performance, is expected to find application in treatment of very low active waste streams.

Development of De-NOx selective catalytic reduction catalyst using V2O5 –TiO2 supported on a ceramic filter candle

ABSTRACT This study reports the development of a V2O5-TiO2-based selective catalytic reduction (SCR) catalyst supported on alumina-silicate water filter candles for NOx abatement. The synthesised catalysts have been characterised by thermogravimetry/differential scanning calorimetry, X-ray diffraction, scanning electron microscope and measurement of NOx removal performance. The catalyst synthesised under optimal conditions shows NOx reduction efficiency of >97%. SCR performance has been augmented using O2 as a carrier gas. This simple, reproducible procedure can have wide applications in NOx abatement.

Effect of NOx on AgI formation in Ag-mordenite

Abstract Ag loaded mordenite can be used as a trap for radio-iodine arising from nuclear reprocessing operations. Typically, iodine is trapped in the Ag loaded mordenite by the formation of AgI in the pores of the mordenite, through a solid-vapour reaction. In the presence of NOx and water vapour, AgI is most likely formed by liquid-vapour reaction between AgNO3 and I2. This reaction results in the formation of large aggregates of AgI crystals on the surface of the mordenite, also leading to a yellow colouration of the mordenite, which is not observed when NOx and water vapour is absent.

Decontamination of 106Ru and 99Tc bearing effl uents by chemical treatment

ABSTRACT Ion exchange separation of 137Cs and 90Sr from alkaline intermediate level waste (ILW) generated at back-end of nuclear fuel cycle results in downstream effluent containing substantial amounts of 106Ru and 99Tc activity. Efforts were made to develop suitable chemical treatment based processes for decontamination of these effluents. Feasibility of using various metal sulphides alone or in combination was examined for simultaneous removal of 106Ru and 99Tc. Based on these studies, a formulation involving precipitation of CoS in conjunction with FeS has been proposed for effective decontamination of the effluent. Presence of dibutyl phosphate (DBP) in some of the streams of ILW interfered with decontamination of 106Ru. A process involving removal of DBP as Fe-DBP complex followed by CoS and FeS precipitation developed in this study was found to be effective in decontamination of the effluent containing gross beta activity of 5550 to 37 Bq ml−1. It is inferred that the process is promising for practi...