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Jordan limestone has a broad distribution and occurs in several stratigraphic levels. It is used for construction of composite wall for aesthetic purposes, as thin polished tiles (marble), floor tiles and monumental architecture or dry... more
Jordan limestone has a broad distribution and occurs in several stratigraphic levels. It is used for construction of composite wall for aesthetic purposes, as thin polished tiles (marble), floor tiles and monumental architecture or dry stonewalling that characterizes the countrysideof Jordan buildings. The main goal of this study is to characterize the limestone rocks in Ma'an area in southern part of Jordan and to assess their suitability for building stone. For this purpose a detailed geological, petrographic and physico-mechanical tests were carried out on some representative samples of this area aiming at establishing a better understanding of the important properties of these rocks. It is shown that the controlling factor of the classification of Ma'an area limestone is the uniaxial
Research Interests: Geology and Petrography
Thermal treatment of bromine-contaminated polymers (i.e., as in e-waste) with metal oxides is currently deployed as a mainstream strategy in recycling and resources recovery from these objects.
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Oil shale samples were pyrolysed at different heating rates. The effect of heating rate on fractional composition of shale oil is investigated in 0.2–6°Cmin−1 range. It is found that increasing the heating rate increases the content of... more
Oil shale samples were pyrolysed at different heating rates. The effect of heating rate on fractional composition of shale oil is investigated in 0.2–6°Cmin−1 range. It is found that increasing the heating rate increases the content of aliphatic of the liquid shale oil. Normal paraffins of (C10–C32) are identified in aliphatic fraction. The maximum concentration of these paraffin is found
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Abstract The performance of a modified solar still was investigated considering the following cases: solar still with glass cooling (SC), SC connected to an external collector (SCC), and SCC with phase change material (SCCP). Three... more
Abstract The performance of a modified solar still was investigated considering the following cases: solar still with glass cooling (SC), SC connected to an external collector (SCC), and SCC with phase change material (SCCP). Three different PCMs were used; sodium acetate trihydrate, sodium thiosulfate pentahydrate, and paraffin wax. The effect of various parameters; controllable (hot water circulation rate, PCM mass, and cooling water flowrate) and uncontrollable parameters (solar irradiation, ambient temperature, and wind speed) were investigated. Increasing the solar irradiation from 200 to 700 W/m2 increased the productivity from 0.9 to 3.4, 2.35 to 10, and 3 to 11.9 ml/min for the SC, SCC, and SCCP (with SAT as PCM) systems, respectively. The addition of external collector and PCM increased the productivity 2.4 times. Increasing the coolant mass flow rate from 0 to 10 kg/s, increased the productivity from 1 to 2.14, 1 to 6.65, and 1 to 7.5 ml/min for the SC, SCC, and SCCP systems, respectively. Additionally, increasing the hot water circulation rate of external collector from 0 to 0.1 kg/s increased the productivity from 2.4 to 6 and from 4 to 7.4 ml/min for SCC and SCCP system, respectively. The optimum mass ratio of basin water: PCM was found to be 2:1, while the best PCM type was found to be the one with the highest melting point and latent heat of fusion. The 24-h operation for a typical May month weather data in Jordan, revealed that the productivity improved 1.8 times for SCC and 2.3 times for SCCP-SAT compared with SC system.
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ABSTRACT
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In this paper, the Dead Sea (DS) environment as a carbon dioxide (CO2) potential storage site was investigated. Firstly, the storage capacity of CO2 in ultra-pure and Dead Sea water (DSW) was studied at ambient temperature and pressure.... more
In this paper, the Dead Sea (DS) environment as a carbon dioxide (CO2) potential storage site was investigated. Firstly, the storage capacity of CO2 in ultra-pure and Dead Sea water (DSW) was studied at ambient temperature and pressure. The effect of CO2 pressure on the storage capacity of CO2 in DSW was also studied at different contact times at the ambient temperature. Finally, for comparison purposes, CO2 gas was injected into a solution containing only dissolved calcium ions. Different analytical and instrumental analysis techniques were used to characterize both liquid and solid samples including acid base titration, Atomic Absorption Spectrometry (AAS), X-ray Diffraction analysis (XRD), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Based on the titration method, the storage capacity of CO2 in both pure water and DSW was found to be 1.7 and 1.53 mmole/L, respectively, at ambient temperature (15 °C) and ambient pressure. DSW water was found to contain...
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Microwave assisted leaching has been investigated in an attempt to improve both the yield of extracted metal and reduce processing time. This is especially pertinent in view of the increased demands for metal and more environmentally... more
Microwave assisted leaching has been investigated in an attempt to improve both the yield of extracted metal and reduce processing time. This is especially pertinent in view of the increased demands for metal and more environmentally friendly processes. This work reports a fundamental study on the influence of microwave energy on the dissolution of sulphide minerals. Chalcopyrite and sphalerite were chosen as model materials due to their economic importance and the diversity of their heating behaviour in a microwave field (chalcopyrite being an excellent microwave heater and sphalerite being an extremely poor microwave receptor). Chalcopyrite leaching has been carried out in ferric sulphate and ferric chloride under both microwave and conventional conditions. Conventionally, it was found that chalcopyrite dissolution in ferric sulphate seems to be limited by surface reaction control. More importantly, it has been shown that specific fracture planes on chalcopyrite particle surfaces ...
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Abstract In this work, carbon-coated magnetic iron oxide nanoparticles (CCM) functionalized with polyethyleneimine/amide (PEIA) were successfully prepared. The prepared nanocomposite (CCMNPs-PEIA) was characterized by XRD, TEM, FT–IR, TGA... more
Abstract In this work, carbon-coated magnetic iron oxide nanoparticles (CCM) functionalized with polyethyleneimine/amide (PEIA) were successfully prepared. The prepared nanocomposite (CCMNPs-PEIA) was characterized by XRD, TEM, FT–IR, TGA and VSM techniques. The stability of CCM was tested in both acidic and basic media and they showed a high stability with good magnetic properties. CCMNPs-PEIA were used for separation of U (VI) from aqueous solutions. Several process parameters were tested to investigate the removal efficiency, adsorption capacity and reusability of the CCMNPs-PEIA including, pH, initial concentration of uranium, and desorption and activation media. The CCMNPs-PEIA nanocomposite was found to have excellent affinity toward U over a wide pH range. Surface oxidation of CCM was found to be of major effect of the adsorption capacity of CCMNPs-PEIA due it carboxylation which enhanced PEIA attachment to the carbon surface. The experimental uptake of the prepared nanocomposite was found to be 127.5 mg (U/g (nanocomposite), while the one calculated according to Langmuir model was found to be 123.45 mg/g with a correlation coefficient (R2) of 0.991. The kinetics analysis of the adsorption process suggests that the kinetics can be described well by the pseudo-second order model suggesting that the rate limiting step is chemisorption.
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Abstract In this study, a novel surface functional layer based on quaternary ammonium is synthesized in situ on the surface of silica coated magnetic nanoparticles. The composite is characterized by XRD, FTIR, SEM, VSM, TGA and zeta... more
Abstract In this study, a novel surface functional layer based on quaternary ammonium is synthesized in situ on the surface of silica coated magnetic nanoparticles. The composite is characterized by XRD, FTIR, SEM, VSM, TGA and zeta potential measurements. Sorption/desorption experiments were performed to evaluate its potential to remove uranium (VI) from aqueous solutions. The results indicated that the new composite has a capacity of ∼87 mg/g with 120 min equilibrium time with good recyclability and strong magnetic response. The pseudo-second order kinetic model was found to fit the experimental data fairly well, the data also suggested the presence of intra-particle diffusion. The adsorption isotherm befitted Langmuir equation. Thermodynamic analysis for the adsorption process was performed and the values of ΔG, ΔH and ΔS are reported.
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A solar desalination unit with humidification and dehumidification is presented. Experiments on the unit were conducted. It was found that the performance of the system was strongly dependent on the temperature of inlet salt water to the... more
A solar desalination unit with humidification and dehumidification is presented. Experiments on the unit were conducted. It was found that the performance of the system was strongly dependent on the temperature of inlet salt water to the humidifier, the mass flow rate of salt water, and the mass flow rate of the process air. There existed an optimum rotation speed
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Deep hydrodesulfurization (HDS) is the key method for clean oil production to meet the strict environmental regulations. Density functional theory (DFT) was performed to provide theoretical insight into the influence of microwave electric... more
Deep hydrodesulfurization (HDS) is the key method for clean oil production to meet the strict environmental regulations. Density functional theory (DFT) was performed to provide theoretical insight into the influence of microwave electric field on the adsorption of H2 molecular and sulfur vacancy formation on different edges of MoS2 nanocrystallite. The influence of the electric field on the structure and electrical properties of MoS2 nanocrystallites with sulfur vacancies was also theoretically analyzed. It was found that electric field in a specific direction enhances the adsorption of H2 on the edge of MoS2 cluster. Its application also benefits the spontaneous formation of specific S vacancy on the S edge and increases the active site number of the cluster. The presented results would provide new insights into understanding the promotion mechanism of microwave on the HDS process.
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Co-pyrolysis of brominated flame retardants (BFRs) with polymeric materials prevails in scenarios pertinent to thermal recycling of bromine-laden objects; most notably the non-metallic fraction in e-waste. Hydro-dehalogenation of aromatic... more
Co-pyrolysis of brominated flame retardants (BFRs) with polymeric materials prevails in scenarios pertinent to thermal recycling of bromine-laden objects; most notably the non-metallic fraction in e-waste. Hydro-dehalogenation of aromatic compounds in a hydrogen-donating medium constitutes a key step in refining pyrolysis oil of BFRs. Chemical reactions underpinning this process are poorly understood. Herein, we utilize accurate density functional theory (DFT) calculations to report thermo-kinetic parameters for the reaction of solid polyethylene, PE, (as a surrogate model for aliphatic polymers) with prime products sourced from thermal decomposition of BFRs, namely, HBr, bromophenols; benzene, and phenyl radical. Facile abstraction of an ethylenic H by Br atoms is expected to contribute to the formation of abundant HBr concentrations in practical systems. Likewise, a relatively low energy barrier for aromatic Br atom abstraction from a 2-bromophenol molecule by an alkyl radical site, concurs with the reported noticeable hydro-debromination capacity of PE. Pathways entailing a PE-induced bromination of a phenoxy radical should be hindered in view of high energy barrier for a Br transfer into the para position of the phenoxy radical. Adsorption of a phenoxy radical onto a Cu(Br) site substituted at the PE chain affords the commonly discussed PBDD/Fs precursor of a surface-bounded bromophenolate adduct. Such scenario arises due to the heterogeneous integration of metals into the bromine-rich carbon matrix in primitive recycling of e-waste and their open burning.
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Abstract Nanocomposite materials as innovative environment and energy materials require superbly isolation performance to apply in practice. Here we report successful grafting of polyethylenimine (PEI) on multiwall carbon nanotubes... more
Abstract Nanocomposite materials as innovative environment and energy materials require superbly isolation performance to apply in practice. Here we report successful grafting of polyethylenimine (PEI) on multiwall carbon nanotubes (MWCNTs-PEI) which was characterized using different techniques. The forier transform infrared (FTIR) and thermogravimetric analysis (TGA) analyses showed that PEI was successfully grafted on the oxidized surface of MWCNTs, which shows exceptionally high uptake capacity and stability towards U(VI) ions. The performance of MWCNTs-PEI adsorption characteristics was evaluated at different conditions including initial U(VI) concentration, adsorbent dosage, pH and contact time. The pH was found to have great effect on the adsoption process; the highest adsorption capacity obtained was found in pH range of 6.5–8.7. The experimental uptake of the fabricated MWCNTs-PEI nanocomposite ion-exchanger was found to be 947 mg U/g (nanocomposite), while the one calculated according to Langmuir model was found to be 997 mg/g with an (R2) of 0.978; the largest value reported to date for uranium extraction using MWCNTs based adsorbents from aqueous solutions. Additionally, four consecutive adsorption–desorption cycles suggesting that the synthesized MWCNTs-PEI had exceptional reversibility and stability for uranium isolation from aqueous solutions. This could be due to the synergetic effect of both carboxyl and amine groups attached to the surface of MWCNTs-PEI nanocomposite. The kinetics of the adsorption were best fitted to the pseudo 2nd order model. The MWCNTs-PEI prepared in this work could have great potential for U(VI) separation from aqueous solutions if turned into magnetic for easy separation.
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Abstract This contribution provides a systematic theoretical thermo-kinetic study of the initial reactions between Fe3O4(111) surface, as a representative model for metal oxides in electric arc furnace dust (EAFD) with HCl and selected... more
Abstract This contribution provides a systematic theoretical thermo-kinetic study of the initial reactions between Fe3O4(111) surface, as a representative model for metal oxides in electric arc furnace dust (EAFD) with HCl and selected chlorinated hydrocarbons, as major products from thermal degradation of PVC. Formation of the experimentally observed iron chloride occurs by subsequent dissociative addition of HCl molecules followed by H migration into a surface hydroxyl group. We provided Arrhenius parameters for reactions dictating the conversion of iron oxide into its chloride. In the course of the interaction of chlorinated alkanes and alkenes with the Fe3O4 surface, the opening channel in the dissociative addition route requires lower activation barriers in reference to the direct HCl elimination pathways. However, sizable activation barriers are encountered in the subsequent β C H bond elimination step. Estimated electronic charges confirm the nature of surface Fe Cl bonds as Lewis acid−base pair. The obtained accessible reaction barriers for reactions of chlorinated alkanes and alkenes with the title iron oxide demonstrate that the latter serve as active catalysts in producing clean olefins streams from chlorinated alkanes. Results from this study should be instrumental to understand, on a precise atomic scale, mechanisms operating in fixation of halogens on transitional metal oxides; a viable thermal recycling approach for polymeric materials laden with halogenated constituents.
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The present study uses DRASTIC model on a national rate and assess the groundwater contamination through phosphate release from the mining activities in south of Jordan (Al-Abiad area) using GIS environment. It is found that about 58.6%... more
The present study uses DRASTIC model on a national rate and assess the groundwater contamination through phosphate release from the mining activities in south of Jordan (Al-Abiad area) using GIS environment. It is found that about 58.6% of the area was considered to be of moderate vulnerability, while high and low vulnerability was found to be at 0.6% and 42.8% respectively of the total area. On the other hand, investigation of infiltration process of selected pollutants (soluble phosphate and chloride ions) through the surface layer of study area has confirmed the vulnerability of the groundwater quality toward such as pollutants. Chemical analysis of the effluent washing water from the phosphate beneficiation process showed high concentration of P2O5 (TCP), Cl− and SiO2 comparing with influent washing water. Currently, the effluent water from Al-Abiad and other Jordanian phosphate mining industry is discharged into the desert without treatment or any attempt for reuse.
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Abstract A theoretical model is developed in this work to simulate a solar still connected to an external solar collector and incorporating Sodium Thiosulfate Pentahydrate as phase change material (PCM). Excellent agreement is obtained... more
Abstract A theoretical model is developed in this work to simulate a solar still connected to an external solar collector and incorporating Sodium Thiosulfate Pentahydrate as phase change material (PCM). Excellent agreement is obtained between the theoretical and experimental results for the unit productivity of fresh water and the basin water temperature profile. Sodium thiosulfate pentahydrate worked well as PCM to supply energy during night time for continuous water production and has improved the overall productivity. Incorporating large PCM mass in the system reduced the productivity; increasing the ratio of PCM mass to water mass from 10 to 100% reduced the productivity by up to 30%. While, incorporating large PCM mass in the system has kept the basin water temperature higher for longer time. This is useful if the unit is to be used for supplying potable water and hot water mainly after sunset and for heating purposes especially in cold places. Reducing the overall heat transfer coefficient from 10.4 to 2.6 W/m2·K can increase the productivity by >100%. The cooling water through the glass cover can have significant effect (37% increase) on the unit productivity of fresh water if its flow rate is increased from 0.01 to 0.1 kg/s.
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Abstract This paper reviews the latest research findings on the combined treatment of both electric arc furnace dust (EAFD) and halogenated plastic wastes, mainly polyvinyl chloride (PVC) and brominated flame-retardants (BFRs). EAFD... more
Abstract This paper reviews the latest research findings on the combined treatment of both electric arc furnace dust (EAFD) and halogenated plastic wastes, mainly polyvinyl chloride (PVC) and brominated flame-retardants (BFRs). EAFD contains heavy metals (Zn, Pb, Fe, Cd, etc.); its disposal using the traditional landfilling method threatens the environment. On the other hand, halogenated plastic wastes accumulate annually at an alarming rate due to their excessive production, consumption, and disposal. PVC, for example, does not decompose naturally; it remains one of the most dangerous plastics, as it contains high proportions of chlorine that is responsible for hazardous emissions of chlorinated organic compounds (dioxins) and hydrochloric acid vapour. Recent research have focused on the combined treatment of PVC/BFRs and EAFD. HCl/HBr acids produced from the pyrolysis of PVC/BFRs can react with the metal oxides in the EAFD to convert them into readily separable metal halides. Alternatively, several researches illustrated the advantages of using additives such as metal oxides during the incineration treatment of waste PVC/BFRs to fix gaseous HCl/HBr, and consequently, EAFD would be considered an excellent and cheap candidate for PVC dechlorination, as well as dehalogenation of other halogenated plastics during thermal recycling processes. In this review we critically discuss literature findings on thermal treatment of PVC/BFR materials under oxidative and pyrolytic environments, typically at temperatures of 200–900 °C in presence of metal oxides or EAFD. We also discuss the treatment/disposal routes for both waste materials (EAFD and halogenated plastic wastes) and the environmental impact of these disposal options. The review, finally, proposes the research necessary to minimize the hazards of these waste materials; Several future research areas were identified including the need to study the behaviour of real EAFD-plastic waste mixtures under oxidative thermal conditions with focus on both the selective recovery of metals and identification, quantification, and minimization of halogenated organic compounds released during the combined thermal treatment.
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The leachability of bottom medical waste ash from a Jordanian incinerator was studied in this work. The ash was characterized in terms of particle size distribution, chemical and mineralogical composition followed by leaching of several... more
The leachability of bottom medical waste ash from a Jordanian incinerator was studied in this work. The ash was characterized in terms of particle size distribution, chemical and mineralogical composition followed by leaching of several size fractions at different conditions (leaching time, temperature, initial pH, particle size, and solid liquid ratio). The major elements found in the ash were Ca, Si, Al, Cl, Na, Fe, Ti, S, Mg, Ba, and K, while the main mineral phases found in the ash were calcite, halite, sylvite, anhydrite, hematite, hydrochlorborite, cristobalite, melanterite, and chlormayenite. Leaching data indicates that as leaching time and S/L increased, the concentration of metals increased in the leachate. The highest leaching level was at a S/L ratio of 60 mg/ml. As the particles sizes decreased, the concentration of the majority of metals studied increased. Meanwhile, the effect of particle size on other metals was not regular due to the fact that sieving resulted in more concentrated metals in certain particle size fractions. Leachability results also indicate that variation in the initial pH has a slight effect on the degree of leaching. The concentration of some metal ions increased with temperature, while others increased initially but subsequently decreased. The extracted quantities of all the heavy metals were less than the limits set by EPA.
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This work reports a thermodynamic assessment of EAFD chlorination products stem from thermal decomposition products of PVC. Upon PVC pyrolysis, HCl gas is liberated in conjunction with several volatile organic matters leaving solid... more
This work reports a thermodynamic assessment of EAFD chlorination products stem from thermal decomposition products of PVC. Upon PVC pyrolysis, HCl gas is liberated in conjunction with several volatile organic matters leaving solid carbonaceous residue. EAFD contains appreciable quantities of zinc, iron and lead oxides. These react with HCl to form metal chlorides, if EAFD is added to the PVC as a dechlorination agent. Selective chlorination of zinc and lead present in EAFD leaving iron in its oxide form is of an apparent commercial value. Detailed thermodynamic analysis of EAFD chlorination by HCl was performed considering the effects of several variables. These include temperature, amount of chlorination agent, presence of oxidizing agent and the effect of presence of other EAFD constituents such as sodium, potassium, calcium, silicon and sulfur. It was found that 100% recovery of both zinc and lead can be achieved for mixture containing 50% EAFD and 50% PVC when pyrolyzed under inert conditions, but contaminated with at least 20% of the iron chloride. However, when thermal treatment is performed in the presence of oxygen, the 100% zinc and lead recoveries were achieved at lower temperature with a minimal iron contamination (< 2.6%). Removal of sodium and potassium chloride from EAFD prior to pyrolysis by washing, under oxidizing condition, has also resulted in great selectivity in zinc and lead chlorination. The behavior of other elements during chlorination process was also discussed. The results obtained shall be instrumental in efforts aiming to achieve optimum recycling operations for both categories of pollutants.
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Abstract The interplay of halogenated compounds with metal surfaces has been the focus of many experimental and theoretical studies. These investigations have mainly aimed to illustrate the potential dual role of transition metals and... more
Abstract The interplay of halogenated compounds with metal surfaces has been the focus of many experimental and theoretical studies. These investigations have mainly aimed to illustrate the potential dual role of transition metals and their oxides in mediating formation of toxic halogenated aromatics as well as their catalytic-assisted decomposition over these surfaces. An initial and prominent step in conversion of these precursors into heavier halogenated aromatics signifies their dissociative adsorption on metallic species readily present in the combustion media. This contribution represents a systematic computational study to examine thermo-kinetic parameters underlying rupture of Cl/Br C bonds in halogenated model compounds (namely; 2-chloropropane, chloromethane, chloroethyne, chloropropene, chlorobenzene, 2-bromopropane, bromomethane, bromoethyne, bromopropene, and bromobenzene) over the Cu(100) surface. These compounds adapt very weak physisorbed molecular states evidenced by marginal adsorption energies and minimal structural changes, in reference to their gas phase molecules. The calculated reaction barriers for Cl/Br-C bond fissions are scattered in the range of 8.3–37.2 kcal mol−1. Stronger Cl C bonds in reference to Br C bonds (in the gas phase) translate into higher corresponding reaction barriers for the former. The calculated reaction rate constants and activation energies reveal faster rate for the decomposition of the brominated species. Our calculations of the activation energies correlate very well with analogues experiment values.
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Abstract Brominated flame retardants (BFRs) are bromine-bearing hydrocarbons added or applied to materials to increase their fire resistance. As thermal treatment and recycling are common disposal methods for BFR-laden objects, it is... more
Abstract Brominated flame retardants (BFRs) are bromine-bearing hydrocarbons added or applied to materials to increase their fire resistance. As thermal treatment and recycling are common disposal methods for BFR-laden objects, it is essential to precisely describe their decomposition chemistry at elevated temperatures pertinent to their thermal recycling. Laboratory-level and pilot-scale investigations have addressed the thermal decomposition of pure BFRs and/or BFR-laden polymers under oxidative and pyrolytic environments, typically at temperatures of 280–900 °C. These studies shed light on the effects of various factors influencing the decomposition behaviour of BFRs such as chemical character, polymer matrix, residence time, bromine input, oxygen concentration, and temperature. Although BFRs decomposition mainly occurs in a condensed phase, gas phase reactions also contribute significantly to the overall decomposition of BFRs. Exposing BFRs to temperatures higher than their melting points results in evaporation. Quantum chemical calculations have served to provide mechanistic and kinetic insights into the chemical phenomena operating in decomposition of BFRs and subsequent emissions of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs). Under thermal conditions such as smouldering, municipal waste incineration, pyrolysis, thermal recycling, uncontrolled burning and fires, BFRs degrade and form brominated products of incomplete combustion (BPICs). Thermal degradation of BFRs often proceeds in the presence of bromine atoms which inhibit complete combustion. Major BPICs comprise brominated benzenes and phenols in addition to a wide range of brominated aromatics. Pyrolytic versus oxidative conditions seems to have very little influence on the thermal stability and decomposition behaviour of commonly-deployed BFRs. Thermal degradation of BFRs produces potent precursors to PBDD/Fs. Experimental studies have established inventories of PBDD/F emissions with alarming high yields for many BFRs. Co-combustion of BFRs-containing objects with a chlorine source (e.g. polyvinyl chlorides) results in the emission of significant concentrations of mixed halogenated dibenzo-p-dioxins and dibenzofurans (i.e. PXDD/Fs). Formation of PBDD/Fs from incomplete BFRs decomposition occurs primarily due to the condensations of gas phase precursors, including unaltered structural entities of some BFRs in their own right. Complete destruction of BFRs promotes PBDD/Fs formation via de novo synthesis. Bromination of PBDD/Fs in gas phase reactions is more prevalent if compared with chlorination mechanisms of PCDD/Fs, which is largely dominated by heterogeneous pathways. In uncontrolled burning and in simulated fly ash experiments, a strong correlation between congeners patterns of polybrominated diphenyl ethers (PBDEs) and PBDD/Fs indicate that PBDEs function as direct precursors for PBDD/Fs, even in the de novo synthesis route. In this review, we critically discuss current literature on BFRs thermal decomposition mechanisms; gather information regarding the contribution of homogenous and heterogeneous routes to overall BFRs decomposition; survey all studies pertinent to the emission of PBDD/Fs and their analogous mixed halogenated counterparts from open burning of e-waste, and finally, highlight knowledge gaps and potential directions that warrant further investigations.
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The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both... more
The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both materials with varying TBBPA loads (1:1 and 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at heating rates of 5 and 10 °C/min. The mixtures degraded through several steps, including decomposition of TBBPA yielding mainly HBr, bromination of metal oxides, followed by their evaporation in the sequence of CuBr3, ZnBr2, PbBr2, FeBr2, MnBr2, KBr, NaBr, CaBr2, and MgBr2, and finally reduction of the remaining metal oxides by the char formed from decomposition of TBBPA. Thermodynamic calculations suggest the possibility of selective bromination of zinc and lead followed by their evaporation, leaving iron in its oxide form, while the char formed may serve as a reduction agent for iron oxides into metallic iron. However, at higher TBBPA volumes, iron bromide forms, which can also be evaporated at a temperature higher than those of ZnBr2 and PbBr2. Results from this work provide practical insight into selective recovery of valuable metals from EAFD while at the same time recycling the hazardous bromine content in TBBPA.
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Abstract This work reports on the bromine fixing ability of a typical electric arc furnace dust (EAFD) upon its co-pyrolysis with tetrabormobisphenol (TBBA), the most widely used brominated flame retardant) both experimentally and... more
Abstract This work reports on the bromine fixing ability of a typical electric arc furnace dust (EAFD) upon its co-pyrolysis with tetrabormobisphenol (TBBA), the most widely used brominated flame retardant) both experimentally and theoretically following thermodynamic calculations. Experimentally, the following variables were considered in this investigation: EAFD: TBBA mass ratio (1:1, 1:2 and 1:3), pyrolysis heating rate and its final temperature and the effect of the NaCl and KCl presence in the dust. In the thermodynamic analysis the same parameters were studied excluding the heating rate. According to thermodynamic calculations, it was found that almost 100% of bromine, released as HBr during the thermal decomposition of TBBA, can be fixed by EAFD as metal bromides when 1:1 and 1:2 ratios where used. These metal bromides remain mainly in the solid form below 400 °C; above this temperature they commence evaporation leaving the reaction system. At 1:3 ratio almost 10% of the initial bromine contents is released in HBr gaseous form. Experimentally, it was found that about 70% of HBr is captured by EAFD when 1:1 and 1:2 ratios were used at temperatures below 350 °C, however, only 53% were captured when ratio 1:3 was used. At all conditions, the escaped gaseous HBr was as low as 6%. It was also found that high heating rates negatively affected the metal oxides ‘capacity to capture emitted HBr.
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Abstract In this work, an experimental study on water desalination using a solar still having phase change material (PCM) and connected to a solar collector was carried out. The PCM is used to store solar thermal energy collected by the... more
Abstract In this work, an experimental study on water desalination using a solar still having phase change material (PCM) and connected to a solar collector was carried out. The PCM is used to store solar thermal energy collected by the system at daytime as latent heat, to provide heat during night time thus continuous operation. Water in the basin and the PCM were heated by direct solar radiation and by hot water flowing through a coil heat exchanger, fixed in the basin, heated by a solar collector. The produced water vapor from the basin condensed on the inner side of the water cooled double-glass cover. The condensate was withdrawn as fresh water. The effect of hot water circulation flow rate, cooling water flow rate, and basin water level on the amount of fresh water produced were studied. The production rate of desalinated water was proportional to the increase in ambient temperature and hot water circulation flow rate. There also is an optimum value of cooling water flowrate (about 10 ml/s) at which the unit productivity was the highest. Additionally, as the water level in the basin increased the productivity decreased. The unit was capable of producing 4300 ml/day·m2, of which about 40% was produced after sunset. The economic evaluation reveal that such units are feasible mainly in remote areas.
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Abstract Barium hexaferrite (BaM)/ultrahigh molecular weight polyethylene (UHMWPE) composite with remarkably high electrical charge storage capabilities has been developed. The BaM particles were synthesized by the chemical... more
Abstract Barium hexaferrite (BaM)/ultrahigh molecular weight polyethylene (UHMWPE) composite with remarkably high electrical charge storage capabilities has been developed. The BaM particles were synthesized by the chemical co-precipitation approach followed by sintering at high temperatures. The composites were prepared by dry compounding followed by molding at high temperature and pressure. The BaM nanoparticles were localized at the surface of the UHMWPE microparticles and consequently formed a mesh-like network of honeycomb structure within the composite matrix. The impedance analysis showed that the composite filled with only 2 wt% BaM exhibits a dielectric ( e ′ ) constant and dissipation factor ( tan δ ) of 116 and 0.01, respectively, revealing that this composite is attractive for electric charge storage applications.
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Abstract Wastewater generated from phosphoric acid industry poses a real environmental challenge. This water contains valuable components the utilization of which can contribute to the conservation of natural resources. Water sample from... more
Abstract Wastewater generated from phosphoric acid industry poses a real environmental challenge. This water contains valuable components the utilization of which can contribute to the conservation of natural resources. Water sample from an effluent pond of a phosphoric acid plant was collected and characterized for its physical and chemical properties. The collected samples were subjected to a hybrid process of chemical precipitation followed by nanofiltration. Both sulphate and fluoride ions were separated by precipitation using Ca(OH) 2 . Silicon exhibited complex behaviour during the precipitation stage. The observed flux using the different tested membranes (NF90, NF270, and BW30) indicated the success of the pre-treatment method in preventing heavy fouling. Very high rejections were obtained using the NF90 and BW30 membranes and, generally, the rejection increased with pressure. As expected, higher flux and lower rejections were observed with NF270 for Si and H 3 PO 4 species. At a pressure of 20 bar the rejection increased with feed concentration which can be attributed to Donnan effects. It is concluded that NF270 could be potentially applied to separate PA from the rest of the species present in water. However, the main challenge is the low rejection of Si.
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Research Interests:
Hydrogen halides (HCl/HBr) represent major halogen fragments from the thermal decomposition of halogen laden materials, most notably PVC and brominated flame retardants (BFRs). Co-pyrolysis of halogen-containing solid waste with metal... more
Hydrogen halides (HCl/HBr) represent major halogen fragments from the thermal decomposition of halogen laden materials, most notably PVC and brominated flame retardants (BFRs). Co-pyrolysis of halogen-containing solid waste with metal oxides is currently deployed as a mainstream strategy to treat halogen content as well as to recycle the valuable metallic fraction embedded in electric arc furnace dust (EAFD) and e-waste. However, designing an industrial-scale recycling facility necessitates accurate knowledge on mechanistic and thermo-kinetic parameters dictating the interaction between metal oxides and hydrogen halides. In this contribution, we investigate chemical interplay between HCl/HBr and zincite surfaces as a representative model for structures of zinc oxides in EAFD by using different sets of functionals, unit cell size and energy cut-off. In the first elementary step, dissociative adsorption of the HCl/HBr molecules affords oxyhalide structures (Cl/Br-Zn, H-O) via modest a...