Jayashree Biswal

Electron Beam Grafted Polymer Adsorbent for Removal of Heavy Metal Ion from Aqueous Solution

Abstract An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non‐woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO‐g‐PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co2+, Ni2+, Mn2+, and Cd2+ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd2+>Co2+>Ni2+>Mn2+. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd2+ was faster than that of other ions studied.

Synthesis, characterization and application of Au-198 nanoparticles as radiotracer for industrial applications

This paper describes synthesis and characterization of radioactive gold nanoparticles ((198)Au-NPs), and explores their utility as a radiotracer for tracing an aqueous phase in a continuous laboratory-scale bubble column at ambient conditions. The performance of the (198)Au-NPs as a radiotracer was compared with the results obtained with a conventional radiotracer i.e. bromine-82 ((82)Br) as ammonium bromide and found to be identical. A tank-in-series with backmixing model (TISBM) was used to simulate the RTDs of the aqueous phase and characterize flow in the bubble column.

Synthesis of CdSe quantum dots in PVA matrix by radiolytic methods

Polymer films of polyvinyl alcohol (PVA) containing CdSe quantum dots of various sizes from 3 nm to 5 nm have been synthesised by the radiation-chemical route using CdSO4 and Na2SeSO3 as the starting materials under a reducing condition. 2 MeV electron beam from an electron accelerator and the gamma radiation from a cobalt-60 gamma chamber were used as the irradiation sources for the syntheses. The particle sizes were small in the case of electron beam irradiation as compared to those in the case of the gamma irradiation. The sizes of the quantum dots were strongly dependent on the absorbed dose rate and the initial precursor concentrations. The CdSe quantum dots exhibit excitonic absorption at room temperature. The films containing these quantum dots were quite stable for months.

Leak detection in a high-pressure heat exchanger system in a refinery using radiotracer technique

A radiotracer investigation was carried out in a diesel hydrotreater (DHDT) unit in a refinery for leak detection in a breech-lock heat exchanger system. The main objectives of the study were to identify the leaking heat exchanger in a system with six heat exchangers and estimate the leak rate. Bromine-82 as dibromobiphenyl was selected and used as radiotracer for the investigation. The radiotracer was instantaneously injected into the suction end of the feed pump line to the heat exchanger of the DHDT unit. The movement of the tracer was measured at strategically selected locations using NaI(Tl) scintillation detectors. Based upon the results of the radiotracer investigation, it was found that out of six heat exchangers, exchanger E-1F was leaking.

Discharge rate measurements in a canal using radiotracer methods.

Discharge rates of water were measured in a canal using radiotracer methods with an objective to validate the efficacy of Concrete Volute Pumps (CVPs) installed at various pumping stations along the canal. Pulse velocity and dilution methods were applied to measure the discharge rates using Iodine-131 as a radiotracer. The discharge rate measured in one of the sections of the canal using the pulse velocity method was found to be 22.5m(3)/s, whereas the discharge rates measured using the dilution method in four different sections of the canal varied from 20.27 to 20.62m(3)/s with single CVP in operation. The standard error in discharge rate measurements using dilution method ranged from ±1.1 to ±1.8%. The experimentally measured values of the discharge rate were in good agreement with the design value of the discharge rate (20m(3)/s) thus validating the performance of the CVPs used in the canal.

Measurement of residence time distribution of liquid phase in an industrial-scale continuous pulp digester using radiotracer technique

A series of radiotracer experiments was carried out to measure residence time distribution (RTD) of liquid phase (alkali) in an industrial-scale continuous pulp digester in a paper industry in India. Bromine-82 as ammonium bromide was used as a radiotracer. Experiments were carried out at different biomass and white liquor flow rates. The measured RTD data were treated and mean residence times in individual digester tubes as well in the whole digester were determined. The RTD was also analyzed to identify flow abnormalities and investigate flow dynamics of the liquid phase in the pulp digester. Flow channeling was observed in the first section (tube 1) of the digester. Both axial dispersion and tanks-in-series with backmixing models preceded with a plug flow component were used to simulate the measured RTD and quantify the degree of axial mixing. Based on the study, optimum conditions for operating the digester were proposed.

Seedless synthesis of gold nanorods employing isopropyl radicals generated using gamma radiolysis technique

The one step synthesis of short aspect ratio gold nanorods using gamma radiation method by incorporating cetyltrimethyl ammonium bromide (CTAB) as a directing agent is reported in this communication. In present method of synthesis, isopropyl radical is selectively generated in the system by carrying out radiolysis of aqueous solution containing 2.75 × 10−2 mol dm−3 of acetone, 0.2 mol dm−3 isopropanol, 4 × 10−4 mol dm−2 Au1+ and 6 × 10−5 mol dm−3 Ag+. The isopropyl radical brings about the reduction of Au1+ to Au0, which undergoes coalescence with other Au0 resulting in formation of Au nanorods. The formation of nanorods is attributed to slower reaction of isopropyl radical with Au1+. The TEM of as-prepared nanoparticles confirmed the formation of uniform sized nanorods having aspect ratio 3.

Radiotracer investigation in a glass production unit.

A radiotracer investigation was carried out in a glass production unit in a glass industry. Lanthanum-140 as lanthanium oxide mixed with silica was used as a radiotracer to trace the molten glass in various sections of the unit. Residence time distributions of molten glass were measured and analyzed to identify the flow abnormities. The flow parameters such as breakthrough time, mean residence time, homogenization time, dead volume and flow patterns in different sections of the unit were obtained from the measured RTD data. The results of the investigation were used to improve and optimize the operation of the glass production unit.

Application of thin layer activation technique for monitoring corrosion of carbon steel in hydrocarbon processing environment

Acidic crude oil transportation and processing in petroleum refining and petrochemical operations cause corrosion in the pipelines and associated components. Corrosion monitoring is invariably required to test and prove operational reliability. Thin Layer Activation (TLA) technique is a nuclear technique used for measurement of corrosion and erosion of materials. The technique involves irradiation of material with high energy ion beam from an accelerator and measurement of loss of radioactivity after the material is subjected to corrosive environment. In the present study, TLA technique has been used to monitor corrosion of carbon steel (CS) in crude oil environment at high temperature. Different CS coupons were irradiated with a 13 MeV proton beam to produce Cobalt-56 radioisotope on the surface of the coupons. The corrosion studies were carried out by subjecting the irradiated coupons to a corrosive environment, i.e, uninhibited straight run gas oil (SRGO) containing known amount of naphthenic acid (NA) at high temperature. The effects of different parameters, such as, concentration of NA, temperature and fluid velocity (rpm) on corrosion behaviour of CS were studied.