Ayman Seliman - Academia.edu (original) (raw)

Papers by Ayman Seliman

AGU Fall Meeting Abstracts, Dec 1, 2016

Microchemical Journal, 2020

The monitoring of the presence of plutonium isotopes is a very important issue in both nuclear en... more The monitoring of the presence of plutonium isotopes is a very important issue in both nuclear energy industry and environmental protection for human health risk assessment. The developed method for the determination of 239 Pu isotope with ICP-QMS detection is based on the use of sequential injection analysis (SIA) system for the pretreatment of samples to be analyzed with the use of a commercial sorbent called diglycolamide (DGA-b) for the analyte preconcentration and separation from 238 U, which is the source of the most significant isobaric interference 238 U 1 H +. Optimizing the size of the sorbent bed and the conditions of analyte sorption and elution of plutonium and uranium provides the analytical procedure for 239 Pu determination, where at total analysis time of 45 min (at flow rate 10 mL min −1) the evaluated method detection limit (MDL) for 100 mL sample volume was 88 mBq L −1. This is satisfactory detectability for applications in both technological and environmental samples.

Analytical Technique Purpose Confocal Microscopy Analyze fluorophore distribution and intensity p... more Analytical Technique Purpose Confocal Microscopy Analyze fluorophore distribution and intensity profile ATR-FTIR Verify the presence of ligands Silver Nitrate Titration Quantify accessible chloromethyl groups pH Titration Quantify binding sites Step 1: Suspension polymerization to produce poly(styrene-co-divinylbenzene-co-(4-chloromethyl styrene)) resin Step 2: Functionalization of resin with selective ligand, tetraethyl (dimethyl amino) methylene diphosphonate (PE)

Reactive and Functional Polymers

Environmental Science and Pollution Research, Feb 16, 2011

Introduction Understanding the sorption process in natural geomedia is necessary for effective ut... more Introduction Understanding the sorption process in natural geomedia is necessary for effective utilization of these materials as low-cost adsorbents and consequently as controlled release hazardous elements. This research was oriented to investigate the affinity of two natural zeolite minerals towards cobalt, zinc, and nickel mixture as an important industrial and radioactive waste. Method The uptake of metal ions as a function of different parameters has been studied using a batch equilibrium technique. Results The results revealed that the affinity and adsorption capacity of chabazite and mordenite follow the order: Zn 2+ > Co 2+ >Ni 2+ , with good fits being obtained using Langmuir and Freundlich adsorption isotherms. The metal uptake was found to be concentration-dependent and independent of the pH over 3.0 to 8.0 range; this reveals that the adsorption mechanism is controlled mainly by a pure ion-exchange reaction at the experimental conditions used. Kinetic curves showed a rather fast exchange reaction for three cations, as equilibrium was mostly reached within 20 min. Conclusion These materials especially chabazite are recommended to be used as a reactive barrier for hazardous heavy metals control.

Applied Radiation and Isotopes, 2014

Journal of Radioanalytical and Nuclear Chemistry, 2011

The affinity and removal efficiency of 137 Cs ? , 133 Ba 2? , 85 Sr 2? and 241 Am 3? mixture from... more The affinity and removal efficiency of 137 Cs ? , 133 Ba 2? , 85 Sr 2? and 241 Am 3? mixture from aqueous solutions using two synthetic ferrierites HSZ 700KOA and 700KOD commercially used as a catalyst in oil industry were investigated. The uptake of metal ions as a function of different parameters has been studied using batch equilibrium technique. Kinetic curves showed that the equilibrium was mostly reached within 45 min for Cs ? and Ba 2? and revealed to be longer for Sr 2? and Am 3?. Using Freundlich and Langmuir adsorption isotherms, the results showed that the affinity and adsorption capacity of 700KOA and 700KOD follow the order: Cs ? [ Ba 2? [ Sr 2? [ Am 3? with higher values for first material. Both adsorbents exhibited significant high capacity for Cs ? relative to other cations giving q max 1.97 and 1.78 mmol g-1 for 700KOA and 700KOD, respectively. All metals uptake found to be concentration dependant and independent of the pH over 2 to 10 range except Am 3? ; this reveals that the adsorption mechanism is controlled mainly by pure ion exchange reaction for Cs ? , Ba 2? , Sr 2? and by surface complexation mechanism for Am 3?. These simple nontoxic materials are recommended to be used for radioactive waste treatment especially fission product 137 Cs and activation product 133 Ba.

Journal of Environmental Radioactivity, 2013

New dual functionality scintillating anion-exchange resins were developed for selective determina... more New dual functionality scintillating anion-exchange resins were developed for selective determination of 99 TcO 4 À in various natural freshwater samples. Stable scintillating particles were formed by preparing the vinyl monomer 2-[4-(4 0-vinylbiphenylyl)]-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (vPBD), starting with the commercial organic flour TBut-PBD and its subsequent copolymerization with styrene, divinylbenzene, and p-chloromethylstyrene mixture. To integrate the radiochemical separation and radiometric detection steps within the same bead, the chloromethyl groups of the scintillating resins were subjected to amination reactions with dioctylamine (DOA) and trioctylamine (TOA). On-line quantification of 99 TcO 4 À was achieved by packing the scintillating anion-exchange resin into Teflon tubing for quantification by a flow scintillation analyzer (FSA). The two functionalized resins were selective for pertechnetate over the common anions in natural freshwaters, especially Cl À and SO 4 2À with up to 1000 ppm and with up to 10 ppm I À and Cr 2 O 7 2À. The uptake efficiency of the TOA sensor decreased from 97.88% to 85.08% in well water and river water, respectively, while the counting efficiency was almost constant (69.50%). The DOA performance showed lower efficiency in the two water types relative to TOA. On the other hand, the DOA sensor could be regenerated by 5 M HNO 3 for reuse at least four times without losing its chemical or optical performance. The detection limit was 1.45 Bq which could be achieved by loading 45 mL from well and tap water containing the maximum contaminant level (MCL) of 99 Tc (33 Bq/L).

Conventionally, the sorption methods of rare earth elements were done with cationic ion exchanger... more Conventionally, the sorption methods of rare earth elements were done with cationic ion exchangers. The present work was mainly oriented to find an alternative method for sorption of light rare earth elements (LREEs) based on anionic ion exchangers. Two different anionic exchangers have been tested including Dowex-1 and Sybron SR-7. The selection of these two exchangers was mainly done to investigate the effect of chain length in the polymeric structure on the sorption performance of REEs complexes. Dowex-1 contains tri-methyl amine while SR-7 contains longer chain length of tri-propyl amine as a function group. Sorption of LREEs complexes with nitrilotriacetic acid (NTA) on the two anionic exchangers has been tested by batch technique at various pH and metals concentrations. Aqueous speciation modeling was applied to predict the chemical species distribution of REEs complexes at various pH value of the aqueous phase.

Journal of Environmental Radioactivity, 2021

A hybrid extractive scintillating resin (HESR) was developed for the concentration and detection ... more A hybrid extractive scintillating resin (HESR) was developed for the concentration and detection of radiocesium. The HESR comprised a cesium-selective potassium ferrierite ion-exchange powder embedded in porous polymeric scintillating beads. It was prepared by carrying out suspension polymerization of 4-methylstyrene with divinylbenzene, 2-(1-naphthyl)-4-vinyl-5-phenyloxazole fluor and ferrierite-K powder. A translucent column packed with the HESR was placed in a commercial flow-cell radiation detector for real-time detection of radiocesium. Measurements using the HESR detection system were compared with an on-line gamma-ray measurement using a NaI:Tl well detector containing a column of ferrierite-K powder/SiO2 or potassium-nickel ferrocyanate-polyacrylonitrile (KNiFC-PAN). The NaI:Tl well detector configuration quantified the gamma-ray from 137mBa, while the flow-cell detector primarily quantified the beta particles and conversion electrons of 137Cs. The minimum detectable concentration of the two detection modalities were calculated and shown to be lower than the maximum contaminant level in drinking water of 7.4 Bq/L (200 pCi/L).

Macromolecular Materials and Engineering, 2018

Cs are major long-lived radionuclides in spent nuclear fuel and high-level radioactive wastes. [1... more Cs are major long-lived radionuclides in spent nuclear fuel and high-level radioactive wastes. [1] Strontium-90 is present in surface soil around the world mainly as a result of fallout from past atmospheric nuclear weapons tests, as well as nuclear plant accidents. [2] Moreover, strontium as an element is relatively mobile and can move down with percolating water to underlying layers of soil and into groundwater. [3] The maximum contaminant level allowable by the United States Environmental Protection Agency (EPA) for 90 Sr in public drinking water supplies is 0.33 Bq L −1 (USEPA, 2008). [4] This low level reflects the fact that radiostrontium is known as a "bone seeker" that exhibits biochemical behavior similar to calcium. 90 Sr concentrates in bone surfaces and bone marrow potentially causing bone cancer, cancer of nearby tissues, and leukemia. [5] The relatively long radioactive half-life of 90 Sr isotope combined with the long biological half-life makes it one of the most hazardous products of radioactive fallouts. [5,6] In many cases, reliable detection of 90 Sr is problematic due to its generally low concentration in the environment. A reliable radiological monitoring system requires highly selective, sensitive, and stable techniques, especially for pure beta emitters such as 90 Sr. A variety of methods, including solvent extraction, ion exchange, precipitation, among others, have been developed for the separation of strontium. [1,5-11] In all cases, a selective molecule or a functional group (such as crown ether derivatives) is used that has a higher affinity for Sr 2+ relative to other similar ions (Ca 2+ , Pb 2+) and especially radioactive isotopes of Ba and Ra that have a similar chemical behavior. Traditional methods of extracting groundwater samples and conducting laboratory analyses are expensive, time-consuming, and induce significant disposal challenges. The ideal real-time in situ monitoring system should have limited handling and should measure the radioactivity in aqueous samples directly under environmental conditions without using harsh chemicals. One successful detection scheme is based on detection of Cherenkov radiation generated by the high-energy electrons produced by 90 Y, the daughter element of 90 Sr beta decay. [9,10] This approach assumes that the 90 Sr and 90 Y are in a secular equilibrium in the groundwater environment that is both Halloysite Clay Nanotubes Combining extraction and scintillation properties within the same material is a relatively new approach in development of sensors for detection of radioactive elements. Structural organization of such materials at a nanoscale typically offers higher efficiency of detection and shorter response time. In this contribution, several new protocols are discussed for fabrication of stable extractive scintillating systems based on commercial Superlig 620 (SL) material with high affinity to radiostrontium. Application of hybrid organicinorganic beads with SL particles used as core and halloysite clay nanotubes (HNT) modified with a polyvinyltoluene (PVT) brush as a permeable shell combines high-performance extracting properties of the SL material with efficient light emission properties of the polymer scintillator. The developed SL-HNT-PVT hybrid extractive scintillating material allows real-time detection of low-level concentrations of radiostrontium in water. Moreover, the suggested approach is not limited to detection of Sr but can find broader application in development of chemical, biological, or radioluminescent sensors and multifunctional materials.

Microchemical Journal, 2019

Journal of Environmental Radioactivity, 2018

An on-line radiation monitoring system that simultaneously concentrates and detects radioactivity... more An on-line radiation monitoring system that simultaneously concentrates and detects radioactivity is needed to detect an accidental leakage from a nuclear waste disposal facility or clandestine nuclear activity. Previous studies have shown that classical control chart methods can be applied to on-line radiation monitoring data to quickly detect these events as they occur; however, Bayesian control chart methods were not included in these studies. This work will evaluate the performance of a Bayesian control chart method, the Shiryaev-Roberts (SR) procedure, compared to classical control chart methods, Shewhart 3-σ and cumulative sum (CUSUM), for use in on-line radiation monitoring of 99 Tc in water using extractive scintillating resin. Measurements were collected by pumping solutions containing 0.1-5 Bq/L of 99 Tc, as 99 TcO − 4 , through a flow cell packed with extractive scintillating resin coupled to a Beta-RAM Model 5 HPLC detector. While 99 TcO − 4 accumulated on the resin, simultaneous measurements were acquired in 10-s intervals and then re-binned to 100-s intervals. The Bayesian statistical method, Shiryaev-Roberts procedure, and classical control chart methods, Shewhart 3-σ and cumulative sum (CUSUM), were applied to the data using statistical algorithms developed in MATLAB®. Two SR control charts were constructed using Poisson distributions and Gaussian distributions to estimate the likelihood ratio, and are referred to as Poisson SR and Gaussian SR to indicate the distribution used to calculate the statistic. The Poisson and Gaussian SR methods I would like to express my sincere gratitude to my advisor, Dr. Tim DeVol, for supporting me through my Master's degree the last two years. I am forever grateful for the freedom he gave me to work on my research, but am also grateful for his willingness to help when needed, particularly when equipment did not work. His expertise and guidance were also greatly appreciated when filling out applications for scholarships, fellowships, and doctoral programs. I do not believe that I would have been as successful without his advice and recommendation. I would also like to thank my other committee members, Dr.

Talanta, 2019

Diglycolamide ligands are widely applied in the analysis of radionuclides, especially lanthanides... more Diglycolamide ligands are widely applied in the analysis of radionuclides, especially lanthanides and actinides. They are used in liquid-liquid extraction procedures or in solidphase extraction sorbents where they are adsorbed on the surface of hydrophobic polymers. The main objective of this study was to synthesize the N,N,N′,N′-tetrahexyl diglycolamide with one vinyl terminating group (vTHDGA) for further covalent immobilization on the polystyrene-divinylbenzene polymeric support. The obtained complexing resin (THDGA) was employed for the mechanized sample pretreatment in the Sequential Injection Analysis-Lab-on-Valve (SIA-LOV) flow system for the determination of 239 Pu using ICP-MS detection. The analytical procedure was optimized in the field terms of selectivity towards several other radionuclides and elements forming potentially isobaric interferences in mass spectrometry. For 100 mL volume of sample to be analyzed, the method detection limit (MDL) was 96 mBq L-1 (41 pg L-1). The developed method was employed for the determination of 239 Pu in real samples of a nuclear reactor coolant and spent fuel pool water from a nuclear reactor.

Journal of Radioanalytical and Nuclear Chemistry, 2017

Journal of Radioanalytical and Nuclear Chemistry, 2016

This contribution characterizes the stability of scintillating resins for ionizing radiation dete... more This contribution characterizes the stability of scintillating resins for ionizing radiation detection that were synthesized with 2-(1-naphthyl)-5-phenyloxazole (a-NPO) or 2-(1-naphthyl)-4-vinyl-5-phenyloxazole (v-NPO) fluor in polystyrene (PS) or poly(4-methyl styrene) (PVT) matrices. Leaching studies of the PS and PVT resins with methyl acetate show a 60 % reduction in luminosity and 80 % reduction in detection efficiency for a-NPO samples; while v-NPO resins retained detection properties. Degradation studies indicate the nitration of PS resins and the fluors after nitric acid exposure, resulting in a 100 % reduction in optical properties; whereas PVT resins with v-NPO fluor maintained 20 % detection efficiency. Heuristics are reported for designing stable scintillating resins.

ACS Applied Materials & Interfaces, 2016

We report on the synthesis, spectroscopic and scintillation properties of three new pyrazoline co... more We report on the synthesis, spectroscopic and scintillation properties of three new pyrazoline core based fluorophores. Fluorescence properties of the fluorophores have been studied both in a solution state and in a solid polyvinyltoluene (PVT) resin matrix of different porosity. The synthesized fluorophores were found to be promising candidates for application in plastic scintillators for detection of ionizing radiation (alpha, beta particles, γ rays and neutrons) and demonstrated superior efficiency in comparison to the existing commercially used fluorophores (2-(1-naphthyl)-5-phenyloxazole (αNPO), 9,10-diphenylanthracene, etc.). Moreover, the suggested synthetic route allows functionalization of the fluorophores with a vinyl group for further covalent bound to the PVT or other vinyl polymer matrices, which dramatically improves chemical stability of the system simultaneously improving the photoluminescence quantum yield. Possible mechanisms of the enhanced scintillation properties are discussed based on preliminary quantum mechanical calculations and spectroscopic characteristics of the fluorophores under study.