Oxide Sorbents Research Articles

Ranking traditional and nano-enabled sorbents for simultaneous removal of arsenic and chromium from simulated groundwater

Water from many municipal and private wells are treated to meet arsenic (As(V)) regulations, and new regulations for hexavalent chromium (Cr(VI)) are soon possible. Rather than adding costly capital infrastructure, we explored many types of sorbents' ability to remove both oxygenated anions simultaneously. In laboratory pseudo-equilibrium tests, metal (hydr)oxide sorbents demonstrated high affinity for As(V) but exhibited 30 to 100-fold lower capacities to remove Cr(VI). WBAX resins had some ability to sorb both Cr(VI) and As(V), but competing anions lowered their sorption capacity for As(V) by >90% compared to in a deionized water matrix. Nano-enabled sorbents with iron or titanium nanoparticles embedded inside the porous structure of an anion exchange resin demonstrated high ability to remove both pollutants simultaneously despite competition, with the tested sorbents showing 11μmol/g capacity for Cr(VI) and 19μmol/g for As(V) in simulated groundwater on average. To quantitatively rank sorbents' ability to remove multiple pollutants, a Simultaneous Removal Capacity scoring tool is proposed. This index uses both absolute removal capacity for each contaminant and relative capacity for multiple contaminants, and may be applied to simultaneous removal of any set of aqueous or atmospheric contaminants. Here, the five nano-enabled sorbents ranked in the top seven out of twelve sorbents tested for simultaneous Cr(VI) and As(V) removal. This work demonstrated traditional and novel nano-enabled sorbents can reduce multiple contaminants of health concern, resulting in groundwater treated to drinking water standards.

Effects of Oxygen Vacancy Order–Disorder Phase Transition on Air Separation by Perovskite Sorbents

Perovskite oxide sorbents offer promise for adsorption-based separation of air to produce an oxygen enriched stream. The oxygen desorption rate however should be further improved. This work studies the oxygen sorption properties of three La1–xSrxCo1–yFeyO3-δ (LSCF) perovskite oxides with and without oxygen vacancy disorder–order phase transition. The LSCF with lower iron content [La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991)] shows the highest sorption capacity in 500–800 °C. The material with disorder–order phase transition during desorption also exhibits enhanced oxygen desorption rate during the TGA measurement. However, in the fixed-bed desorption process, no obvious rate enhancement resulting from the disorder–order phase transition in oxygen desorption is observed for the LSCF1991 sorbent. The LSCF1991 sample in the fixed-bed quenched at 600 °C after 2 h of desorption shows occurrence of disorder–order phase transition for the perovskite sorbent in the fixed-bed environment. The difference in oxygen desorptio...

Engineering metal (hydr)oxide sorbents for removal of arsenate and similar weak-acid oxyanion contaminants: A critical review with emphasis on factors governing sorption processes

To create an integrative foundation for engineering of the next generation inexpensive sorbent systems, this critical review addresses the existing knowledge gap in factor/performance relationships between weak-acid oxyanion contaminants and metal (hydr)oxide sorbents. In-depth understanding of fundamental thermodynamics and kinetics mechanisms, material fabrication, and analytical and characterization techniques, is necessary to engineer sorbent that exhibit high capacity, selectivity, stability, durability and mass transport of contaminants under a wide range of operating and water matrix conditions requirements. From the perspective of thermodynamics and kinetics, this critical review examines the factors affecting sorbent performances and analyzes the existing research to elucidate future directions aimed at developing novel sorbents for removal of weak-acid oxyanion contaminants from water. Only sorbents that allow construction of simple and inexpensive water treatment systems adapted to overcome fiscal and technological barriers burdening small communities could pave the road for providing inexpensive potable water to millions of people. Novel sorbents, which exhibit (1) poor performances in realistic operating and water matrix conditions and/or (2) do not comply with the purely driven economics factors of production scalability or cost expectations, are predestined to never be commercialized.

72.再生容易なZnO系高温脱硫剤の開発(石炭利用における科学と工学の融合)

72.再生容易なZnO系高温脱硫剤の開発(石炭利用における科学と工学の融合)

Study on the preparation of bimetallic oxide sorbent for mercury removal

Series of adsorbents based on Al2O3 supported Cu and Mn have been prepared and tested for mercury removal from gas streams under various conditions. The metal content, impregnating sequence and the gas composition have significant effect on the performance of the adsorbents. Co-impregnation of Cu and Mn solutions is simple but also of help to improve the Hg pickup capacity, due to the synergic effect of the CuMn oxide, the sorbent prepared using incipient wetness method containing 20% CuO and 20% wt MnO2 has Hg pick capacity of 12.0% wt. It is showed that the oxide form the adsorbent can reduce Hg from more than 11,600ppb to 0.1ppb in a single pass. The presence of H2S in the gas stream changes the Hg sorption mechanism and increase Hg pickup capacity. XRD and electron microscope characterization results of the fresh and spent sorbent show that the active phases of the sorbent are CuMn(OH)3Cl and the presence of Mn2O3 catalyses the metallic Hg to convert into HgCl2 or HgCl. There are no elemental Hg present in the spent sorbent, but in the chemical states.

Steam regenerative removal of hydrogen sulfide from hot syngas by a novel tin oxide and yttrium oxide sorbent

A novel H2S sorbent based on SnO2 and Y2O3 is developed by a co-precipitation method for steam regenerative removal of H2S from hot syngas at moderate temperatures (400–500 °C). SnO2-Y2O3 sorbent is stable in a reducing atmosphere (i.e. 500 °C, 50% H2) and achieves a 99.9% H2S removal during successive desulfurization and regeneration cycles. The addition of yttrium to SnO2 decreases the reduction property of SnO2 and no metallic Sn exists in the reducing atmosphere due to the formation of a pyrochlore-type compound, Y2Sn2O7. The SnO2-Y2O3 sorbent has a desulfurization performance deterioration with the increasing calcination temperature. The newly developed SnO2-Y2O3 sorbent can be regenerated by steam at 500 °C. In the eight successive desulfurization and regeneration cycles, SnO2-Y2O3 sorbent has a cyclic breakthrough sulfur capacity of 9 mg/g without significant sulfur capacity loss.

Three-dimensionally ordered macroporous metal oxide–silica composite for removal of mercaptan

A series of 3DOM and non-3DOM metal oxide–silica composites were prepared and tested dynamically in a packed-bed reactor at room temperature to remove ethanethiol from a gas stream containing ethyl mercaptan in moist N2.The obtained sorbents were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption techniques. The experimental results showed that the adsorption ability of different kinds of metal oxide–silica composites with 3DOM structure decreased in the sequence: 3D-CuO/SiO2 > 3D-NiO/SiO2 > 3D-Co3O4/SiO2 > 3D-ZnO/SiO2. The best ratio of CuO to SiO2 of 3DOM copper–silicon oxide sorbents for ethanethiol removal was found to be 1:2. The 3DOM structure could improve the removal activity of sorbents remarkably because of the high porosity with ordered interconnected macropores as well as the large surface area and high dispersion of CuO. It was also found that a moist atmosphere greatly benefited the adsorption of ethanethiol at ambient condition.

Sulfur dioxide removal by sol-gel sorbent derived CuO/Alumina sorbents in fixed bed adsorber

Nanostructured alumina supported copper oxide granular sorbents were prepared by the sol-gel method. The properties of the sol-gel derived sorbents were compared with a similar commercial sorbent which has been used in the pilot scale moving-bed copper oxide process for flue gas treatment. The crushing strength of the sol-gel derived sorbents is about 6–7 times that of the commercial samples, while the attrition rate of the former is at least 3 times smaller. At temperatures below 400 °C, SO2 sorption capacity of the sol-gel derived sorbent is about 3 times that of the commercial sorbent with a similar amount of CuO loading (7–9 wt%). The better mechanical properties and higher sulfation capacity of the sol-gel derived alumina supported copper oxide sorbents are due to their unique microstructure and the coating method for CuO.

Mesoporous manganese oxides prepared by sol-gel method: Synthesis, characterization and sorption properties towards strontium ions

Radionuclides of strontium 85,90Sr are one of the main components of low active liquid radioactive wastes. In present work mesoporous manganese oxides were synthesized by non-template sol-gel method and their sorption properties towards strontium 85Sr ions from model aqueous solutions were studied. Influence of phase composition and parameters of porous structure of manganese oxide sorbents on their sorption and selective properties towards radioactive 85Sr ions was established. The samples of manganese oxide prepared with hydrogen peroxide and calcined at 200–400°C were characterized by the highest values of sorption capacity and distribution coefficient of approximately 200–220mgg−1 and (0.72–3.67)×105cm3g−1 respectively. It was shown that the presence of 0.1M NaCl solution practically doesn’t influence on removal efficiency of stable strontium ions and leads to decreasing distribution coefficient on a decimal order. In case of the presence of 0.05M CaCl2 solution falling strontium removal efficiency was observed for all synthesized sorbents regardless of the properties of reducing reagent and its calcination temperature. Sorption characteristics in this case significantly decreased and amounted to 12–18mgg−1 for sorption capacity and (1.1–8.7)×102cm3g−1 for distribution coefficient.

Carbonation and deactivation kinetics of a mixed calcium oxide–copper oxide sorbent/oxygen carrier for post-combustion carbon dioxide capture

Removing carbon dioxide from industrial effluents via solid carbonate sorbents is a potential greenhouse gas mitigation strategy that can also produce hydrogen from the effluent in water gas shift reactors downstream. However, to regenerate the calcium oxide (from the carbonate) requires high temperature that is provided via an oxidation step. To avoid costly oxycombustion to regenerate the CaCO3, it is possible to use the heat generated during the reduction of copper oxide and manganese oxides as chemical looping agents. Unfortunately, sorbents sinter thereby and consequently the surface area drops in the regeneration step. A mixed CuO–CaO sorbent with 10% calcium aluminate binder lost 84% of its initial BET surface area during the first 100min on stream. Homogeneous calcium–copper–cement oxide sorbent deactivate to the 0.5 order with respect to the remaining surface area and a decay constant equal to 2.86min−1. An empirical equilibrium power law model characterizes the carbonation rate from 425°C to 665°C with 10% to 20% CO2 in a 45mm fixed bed. The apparent activation energies of the forward and reverse reaction are 220 and 120kJmol−1, respectively. In addition to sintering, the reaction rate of the regeneration step decreases with time on stream following a zero order process. We attributed this gradual irreversibility to increased crystallinity, reducing the diffusion rate of CO2 to the active carbonate phase. By integrating this resistance to the kinetic model, we are able to explain 99% of the variance in the gas profiles measured by a mass spectrometer.

Simultaneous extraction and preconcentration of aniline, phenol, and naphthalene using magnetite–graphene oxide composites before gas chromatography determination

The coextraction of acidic and basic compounds from different mediums is a significant concept in sample preparation. In this work, simultaneous extraction of acidic, basic, and neutral analytes in a single step was carried out for the first time. This procedure employed the dispersive solid-phase microextraction of analytes with magnetic graphene oxide (graphene oxide/Fe3 O4 ) sorbent followed by gas chromatography with flame ionization detection. After the adsorption of analytes by vortexing and decantation of the supernatant with a magnet, the sorbent was eluted with acetonitrile/methanol (2:1) mixture. The parameters affecting the extraction efficiency were optimized and obtained as follows: sorbent amount 60 mg, desorption time 1 min, extraction time 5 min, pH of the sample 7, sample volume 20 mL, and elution solvent volume 0.3 mL. Under the optimum conditions, linear dynamic ranges were achieved in the range of 0.5-4, 0.25-4, and 0.25-2 μg/mL and limits of detection were 0.341, 0.110, and 0.167 μg/mL for aniline, phenol, and naphthalene, respectively. The relative standard deviations were in the range of 3.3-5.7% in eight repeated extractions. Finally, the applicability of the method was evaluated by the extraction and determination of analytes in stream water and drinking water samples and satisfactory results were obtained.

High-Temperature Capture of CO2 by Strontium Oxide Sorbents

This article reports on the use of strontium oxide (SrO)-based sorbents for chemical sorption of carbon dioxide (CO2) at high temperatures (>1000 °C). Two different sizes of the SrO granules were tested as potential sorbent materials through cycles of carbonation and calcination at high temperature in a fixed-bed reactor, under flux of argon (Ar) and Ar/CO2. Thermogravimetric analysis (TGA) assessed their carrying capacity and effectiveness at increasing numbers of cycles. Further investigation was dedicated to the SrO granules in combination with alumina or hydroxyapatite to prevent the material from sintering under high-temperature conditions and to improve the sorbent durability. A simple kinetic analysis was also performed on the basis of TGA data. The sorbent materials, before and after the cycling steps, were characterized through mercury intrusion porosimetry, environmental scanning electron microscopy, and X-ray diffraction analysis to evaluate any change in the microstructure, thus including the ...

The Regeneration Properties of Manganese Oxide Sorbent under SO<sub>2 </sub>Atmosphere<sub> </sub>

The effects of temperature and concentration of sulfur dioxide on regeneration behavior of manganese oxide sorbent were studied in a fixed-bed reactor. The sorbents were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. Subsequently, the regeneration mechanism was inferred and the yield of export elemental sulfur was calculated. The study shows that, the major regeneration products are Mn3O4, MnSO4 and a small amount of elemental sulfur under SO2 atmosphere.The sulfate can be converted to Mn3O4and Mn2O3 at 800 °C under N2 atmosphere. The elemental sulfur productivity increases with the increase of temperature and concentration of sulfur dioxide.The regeneration conversion attains maximum value (68%) at 800 °C under the atmosphere of 1.68% SO2, and the productivity of elemental sulfur reaches to maximum value (29%) under the conditions.

Characteristics and Regeneration Properties of Manganese Oxide Sorbent under O<sub>2</sub> Atmosphere

The regeneration behavior of manganese oxide sorbent under O2atmosphere was investigated in a fixed bed micro-reactor under the influence of different temperatures and O2 concentrations. The change in phase of the sulfided and the regenerated sorbents was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. MnS, Mn3O4 and MnSO4 were found in regenerated sorbent at 400 °C, which indicated that the regeneration of the sulfided sorbent was not complete, however, MnS was converted to Mn3O4, Mn2O3 and few MnSO4 at 800 °C. The manganese sulfate formed during the regeneration but decomposed to Mn2O3 at 800 °C. MnS reacts with O2 to form Mn3O4 and MnSO4, and then MnSO4 was decomposed at 800 °C. The results show that the optimum regeneration temperature and O2 concentration obtained from this experiment are 800 °C and 2.2 vol %, respectively, and the regeneration conversion ratio was about 95%.

Sorption behavior of slightly reduced, three-dimensionally macroporous graphene oxides for physical loading of oils and organic solvents

High pollutant-loading capacities (up to 319 times its own weight) are achieved by three-dimensional (3D) macroporous, slightly reduced graphene oxide (srGO) sorbents, which are prepared through ice-templating and consecutive thermal reduction. The reduction of the srGO is readily controlled by heating time under a mild condition (at 1 10^−2 Torr and 200℃). The saturated sorption capacity of the hydrophilic srGO sorbent (thermally reduced for 1 h) could not be improved further even though the samples were reduced for 10 h to achieve the hydrophobic surface. The large meso- and macroporosity of the srGO sorbent, which is achieved by removing the residual water and the hydroxyl groups, is crucial for achieving the enhanced capacity. In particular, a systematic study on absorption parameters indicates that the open porosity of the 3D srGO sorbents significantly contributes to the physical loading of oils and organic solvents on the hydrophilic surface. Therefore, this study provides insight into the absorption behavior of highly macroporous graphene-based macrostructures and hence paves the way to development of promising next-generation sorbents for removal of oils and organic solvent pollutants.

Fe–Al binary oxide nanosorbent: Synthesis, characterization and phosphate sorption property

Phosphorous removal using efficient treatment approach such as adsorption is vital for the control of eutrophication. In this study, nanosized Fe-Al binary oxide sorbent was synthesized through a modified gel evaporation method and employed for adsorption of phosphate from aqueous system. The nanosorbent was characterized by x-ray diffraction (XRD), scanning electron microscope coupled with energy dispersive x-ray spectroscopy (SEM/EDX), tunneling electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and flame atomic absorption spectroscopy (FAAS). Langmuir model showed the best fit to the experimental data with a maximum adsorption efficiency of 16.4mg/g. Having all parameters optimized, it has been found that the nanosorbent exhibited 99.86% phosphate adsorption efficiency. The effect of co-existing anions on the adsorption of phosphate was also studied and no significant effect on the efficiency of the nanosorbent was observed due to competing ions such as fluoride. Desorbabilty of phosphate was investigated and found to be increased with increasing pH. The results of thermodynamic studies indicated that the process is spontaneous and endothermic. Both macroscopic and microscopic approaches were employed to predict the mechanism of phosphate adsorption on the Fe-Al binary oxide nanosorbent. Accordingly, the phosphate adsorption is presumed to occur via the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface.

Release of arsenic from metal oxide sorbents under simulated mature landfill conditions

• Non-redox sensitive sorbents leach arsenic to an equal or greater extent than a ferric sorbent.

Nanostructured Metal Oxide Sorbents for the Collection and Recovery of Uranium from Seawater

The ability to collect uranium from seawater offers the potential for a long-term green fuel supply for nuclear energy. However, extraction of uranium, and other trace minerals, is challenging because of the high ionic strength and low mineral concentrations in seawater. Herein we evaluate the use of nanostructured metal oxide sorbents for the collection and recovery of uranium from seawater. Chemical affinity, chemical adsorption capacity, and uptake kinetics of sorbent materials were evaluated. Materials with higher surface area clearly produced better sorbent performance. Uptake kinetics showed that the materials could rapidly equilibrate in a few hours with effective solution contact. Manganese, iron oxide, and especially Mn–Fe nanostructured composites provided the best performance for uranium collection from seawater. The preferred materials were demonstrated to extract uranium from natural seawater with up to 3 mg U/g-sorbent in 4 h of contact time. Inexpensive nontoxic carbonate solutions were dem...

Разработка системы глубокой сероочистки синтез-газов

Experiments with thermogravimetrical analyzer determined kinetic characteristics of clean zinc oxide (GOST 10262–73) and dynamic characteristics of Katalco 32-4 Johnson Matthey sorbent. Obtained data enable calculation of the sorbent volume required for a complete synthesis gas desulfurization, duration of sorbent working cycle, sorbent conversion rate and general kinetic characteristics of hydrogen sulfide absorption by zinc oxide. Chemical process simulation considering transient multiphase hydrodynamics resulted in the conversion rate of ZnO2SC oxide zinc with different isotherms and parameters of process involving pure zinc oxide and Katalco sorbent within 250 – 950 °C temperatures range.

Effects of microwave irradiation on H2S removal activity from hot coal gas by modified semicoke-supported ZnO sorbents

To improve the desulfurization performance of sorbents at a low cost, modified semicoke-supported zinc oxide sorbents were prepared for hot coal gas by calcining the precursors using microwave and conventional heating. The desulfurization performances of these sorbents were evaluated over a fixed-bed reactor. The effects of microwave-assisted calcination temperature and time on the properties of sorbents were also investigated. These sorbents were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption. The results show that the sorbents calcined by microwave exhibited a much higher sorbent utilization and desulfurization efficiency than those heated by conventional method. Compared to conventional heating, even and rapid heating of microwave led to smaller crystal size and better dispersion of active species. The Brunauer–Emmett–Teller results confirm that microwave irradiation modified the microstructure improved the pore structure (an increase in the specific surface area and pore volume), thus facilitating the gas–solid interactions during the desulfurization processes. A higher concentration of elements Zn and O was observed on the surface of sorbents by XPS analysis, facilitating the reaction of active species with H2S. The performance of the sorbents heated by microwave irradiation appeared to be stable over multiple sulfidation–regeneration cycles.