Number Of Regeneration Cycles Research Articles

Sustainable application of surfactants in soil remediation: Selective pollutants adsorption and hydrogen peroxide-driven adsorbent regeneration

The uncontrolled disposal of the liquid lindane wastes have led to the formation of dense non-aqueous phase liquids (DNAPL), consisting of 28 chlorinated organic compounds (COCs), contaminating soil and groundwater. Surfactant-enhanced aquifer remediation is proposed as technology to treat these sites. However, the polluted emulsion generated must be manged on-site. In this work a two-step process is applied to treat emulsion composed of E-Mulse® 3 (4 g·L−1) as surfactant and a DNAPL (2 gCOCs·L−1). In the first, the COCs were selectively adsorbed in a granular activated carbon (GAC) column with Fe (II) previously adsorbed (10–20mg·g-1) onto the carbon surface, recovering an aqueous phase with surfactant for their reuse. In the second step, the spent GAC was regenerated with a 40 g·L−1 solution of hydrogen peroxide fed to the column at 2 mL·min−1 to promote the oxidation of the COCs adsorbed in the GAC. The kinetic and adsorption model in a multisolute (surfactant and DNAPL) system has been proposed. Five successive cycles of regeneration/adsorption have been successfully applied in the column process. About 50 % of the COCs were retained from the emulsion, and more than 70 % of the surfactant was recovered. The consumption of unproductive oxidants decreased with the number of regeneration cycles. The water effluent obtained after regeneration of GAC did not present chlorinated compounds desorbed and nontoxic by-products generated, such as short-chain acids.

Evaluation of the Use of Cold Plasma for Microtiter Plate Cleaning to Reduce Plastic Biohazard Waste.

Plastic pollution is the accumulation of plastic objects in the Earth's environment and is a global problem of increasing importance. The laboratory and health care industries contribute to this problem by the widely accepted single use of plastics, including microtiter plates used for compound testing. At AstraZeneca, we predict the use of more than 45,000 384-well and more than 11,000 1536-well microtiter plates per year. IonField Systems has developed a microplate cleaning system (MCS) powered by PlasmaKnife technology that uses cold plasma to clean microtiter plates. AstraZeneca proposed the use of this system for standard ANSI (https://slas.org/resources/information/industry-standards/) microtiter plate regeneration. Here we present the results of an evaluation using a model system involving the cleaning of plates following an enzyme-based biochemical assay, as well as the software and hardware enhancements that were incorporated into the production PlasmaKnife MCS. The method involved determining the level of inhibition achieved by residual compound following different cleaning protocols and showed that cleaning achieved in about 2 min was sufficient to remove trace compound contamination. Future work will focus on assessing the number of regeneration cycles that can be reliably achieved.

A Hybrid Ion-Exchange Fabric/Ceramic Membrane System to Remove As(V), Zn(II), and Turbidity from Wastewater

Ceramic membranes and ion exchangers are effective at removing turbidity and ionic contaminants from water, respectively. In this study, we demonstrate the performance of a hybrid ion-exchange fabric/ceramic membrane system to treat metal ions and turbidity at the same time in synthetic wastewater. The removal rate of As(V) and Zn(II) by the ceramic membrane increased with solution pH, while turbidity was completely removed regardless of the solution pH. The main reaction of As(V) removal was adsorption at solution pH 6 and precipitation at solution pH 8, whereas phase-change was the predominant reaction for Zn(II) removal at both solution pH values. The removal efficiency of the ion-exchange fabric was affected by the solution pH, with the maximum removal capacity of As(V) occurring at solution pH 4. The As(V) adsorption capacity of the ion-exchange fabric reached equilibrium within 120 min. The ion-exchange capacity of the ion-exchange fabric was compared with commercial ion-exchange fibers. The regeneration efficiency of the ion-exchange fabric using 0.1 M NaCl solution was around 95% on average and decreased slightly as the number of regeneration cycles was increased. Over 80% of As(V) and Zn(II) were steadily removed at solution pH 6 by the hybrid ion-exchange fabric/ceramic membrane system. Reduced flow rate and removal capacity were recovered through a backwashing process during continuous treatment with the hybrid ion-exchange fabric/ceramic membrane system.

Microwave based regenerating permeable reactive barriers (MW-PRBs): Proof of concept and application for Cs removal

The present study evaluates the concept of permeable reactive barrier (PRB) coupled with microwaves (MWs) as in situ-regenerating technology with focus on Cs-contaminated water. Experimental and modelling results data from batch and column tests were carried out, evaluating several chemical-physical and environmental parameters.Main results showed a very rapid increase in GAC temperature during MW irradiation up to ∼680 °C. This highlights the GAC strong ability to transform MW power into heat due to GAC excellent dielectric properties (ε′ = 13.8). Physical characterization revealed that GAC pore volume and specific surface area change with the number of regeneration cycles. GAC regeneration efficiency variation reflects this behaviour with a maximum value of ∼112% (5th cycle). The final GAC weight loss of ∼7% further demonstrates GAC life span preservation during MW irradiation.Results from column tests confirms that GAC can be regenerated by MW also in dynamic condition, due to sublimation/vaporization and vapour stripping Cs removal mechanisms and that the regeneration effectiveness is time-dependent. The breakthrough curve shape confirms significant benefits from MW irradiation. Overall, obtained finding demonstrated the feasibility of the proposed concept, also providing essential data to guide its scaling-up application.

Cellulose acetate/EDTA-chelator assisted synthesis of ordered mesoporous HAp microspheres for efficient removal of radioactive species from seawater

High exposure to radioactive metal ions, such as uranium (U(VI)) and cesium (Cs(I)), potentially has adverse effects and can cause severe health problems leading to a number of specific diseases. This study primarily aims to facile synthesis self-functionalized mesoporous ion-exchanger for the removal of trace concentrations of radioactive ions from water in an efficient way. The fabricated mesoporous flaky flower-like hydroxyapatite ion-exchanger (MFF-HAp) with its 3D hexagonal mesopore structure has advantages of high surface area, natural surfaces, and active acid sites can strongly induce ion-exchange with uranyl and cesium ions. It was characterized by X-ray diffraction (XRD), fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscope (HR-TEM), energy dispersive X-ray (EDX) spectroscopy, N2 adsorption/desorption and thermal analysis (TGA/DTA). From the engineering point of view, it offers a simple and one-step capture procedure for the decontamination of Cs(I) and U(VI) from their solutions. The interesting findings in this study are the ion-selectivity exhibited by MFF-Hap toward the target U(VI) and Cs(I) ions in environmental and nuclear waste disposal samples, and its reproducibility/durability over a number of regeneration cycles. These unique properties of MFF-HAp ion-exchanger render it as promising durable material for efficient radioactive species accommodation.

Effect of operating parameters of potassium carbonate supported on gamma alumina (K 2 CO 3 /γ-Al 2 O 3 ) on CO 2 capture capacity using depressurized regeneration

Abstract Potassium carbonate (K2CO3) loaded at 17% by weight (wt.%) on a gamma alumina (γ-Al2O3) support was prepared by impregnation and then employed to adsorb carbon dioxide (CO2) under a turbulent fluidized bed regime in a glass riser–sorber. The spent K2CO3/γ-Al2O3 sorbent was regenerated in situ by depressurization at 0.8 or 0.2 atm for 2 or 20 min. The CO2 sorption occurred by both chemical sorption and physical adsorption and the total sorption capacity was not significantly dependent on the sorbent regeneration time (2 or 20 min) or regeneration cycles (1–3), but was strongly dependent upon the regeneration pressure, being better at 0.2 than at 0.8 atm. There was no detectable formation of inactive species, such as KAl(CO3)(OH)2H2O), on the regenerated sorbent and the meso-pore type IV surface area was not affected by the number of regeneration cycles. Rather the relocation of water on the sorbent surface in the hydrothermal treatment after sorbent regeneration is hypothesized to have played an important role in the CO2 capture capacity. This was because the accumulation of water near the pore entrance rather than deep inside the pore reduced the average pore diameter and increased the average pore volume when regenerated at 0.8 atm, but not at 0.2 atm. The regenerated sorbent (at 0.2 atm for 2 min) had a CO2 capture capacity of about 95% of that of the fresh adsorbent. As the result of the short regeneration time, the depressurization regeneration unit can be much more compact than the conventional heat regeneration unit.

Cyclic Regeneration of Pyrolusite-Modified Activated Coke by Blending Method for Flue Gas Desulfurization

The regeneration properties of a novel pyrolusite-modified activated coke (ACP) by blending method were investigated. Cyclic regeneration of ACP (ACP-Rn) shows the ACP was a good desulfurizer. The sample had the best desulfurization performance after five regeneration cycles (ACP-R5), and its sulfur capacity was 178 mg/g, 10.8% higher than that of ACP (161 mg/g). The SBET and pore volume were increased with the number of regeneration cycles, but they were not the limiting factors of the SO2 removal. The better surface functional groups, especially the basic sites, contributed more to the improvement of desulfurization performance of ACP-Rn. The loaded metals played an important role in SO2 removal. The accumulation of metal sulfate in ACP rapidly increased from the first to fifth regeneration cycles and then remained relatively stable during further reuse. The ACP regeneration process divided into three stages: drying, reaction, and pyrolysis. The wrapped metals relatively enhance the pyrolysis and acted ...

Electrospun mesoporous carbon nanofibers produced from phenolic resin and their use in the adsorption of large dye molecules

Mesoporous carbon nanofibers (CNFs) were prepared by a sol–gel/electrospinning process using phenolic resin precursor as carbon source and triblock copolymer Pluronic F127 as template. The final CNFs were obtained after carbonization of as-spun nanofibers and removal of SiO2. Three samples (C-1, C-2, and C-3) with different pore textures were synthesized. The CNF structures were characterized by scanning and transmission electron microscopy, and N2 adsorption–desorption measurements, demonstrating that the samples consisted of nanofibers with mesopores and the mesopore volumes depended on the amount of tetraethyl orthosilicate in the spinnable sols. According to thermogravimetric analysis, the CNF yields of 2.57%, 2.78%, and 2.13% from the spinnable sols for sample C-1, C-2, and C-3 were obtained, respectively. The mesoporous CNFs were used as highly efficient adsorbents for large dye molecules. The relationship between the pore textures and adsorption properties was studied. It is suggested that the adsorption of different dyes depend on an appropriate pore size distribution in addition to surface area. However, the adsorption capacity of the regenerated adsorbents gradually decreased with the number of regeneration cycles. The adsorption of acid red 1 could reach 186mgg−1 for C-3 after seven regeneration cycles. Furthermore, the mechanical strength of CNFs needs improvement.

Combined ion exchange treatment for removal of dissolved organic matter and hardness

Dissolved organic matter (DOM) and hardness cations are two common constituents of natural waters that substantially impact water treatment processes. Anion exchange treatment, and in particular magnetic ion exchange (MIEX), has been shown to effectively remove DOM from natural waters. An important advantage of the MIEX process is that it is used as a slurry in a completely mixed flow reactor at the beginning of the treatment train. Hardness ions can be removed with cation exchange resins, although typically using a fixed bed reactor at the end of a treatment train. In this research, the feasibility of combining anion and cation exchange treatment in a single completely mixed reactor for treatment of raw water was investigated. The sequence of anion and cation exchange treatment, the number of regeneration cycles, and the chemistry of the regeneration solution were systematically explored. Simultaneous removal of DOM (70% as dissolved organic carbon) and hardness (>55% as total hardness) was achieved by combined ion exchange treatment. Combined ion exchange is expected to be useful as a pre-treatment for membrane systems because both DOM and divalent cations are major foulants of membranes.

Multi-analyte SPR immunoassays for environmental biosensing of pesticides

Multi-analyte detection of environmentally relevant pesticides is performed by using a two-channelled surface plasmon resonance (SPR) biosensor. The special design of the SPR instrument allows the determination of several analytes (DDT, chlorpyrifos and carbaryl) via different immobilization formats. First, simultaneous pesticide monitoring is possible by flowing chlorpyrifos, carbaryl or DDT samples separately over each channel of the SPR system, wherein their corresponding recognition element was previously immobilized. The second approach is based on the multiple and combined immobilization of several analyte recognition elements on the sensing surface of one individual flow cell. In this format, the analysis time for all three pesticides varied from 40 to 60 min depending on the number of regeneration cycles. In most cases, similar detection limits were attained for the target analyte irrespective of the assay format, with sensitivity values at the nanogram per litre level (18-50 ng L(-1)). The assay reproducibility was proved through the repeated use of the same sensor surface for over more than 200 assay cycles, whereas the absence of biosensor response to non-related analytes showed the specificity and reliability of the analysis. The SPR instrument, including optics, electronics and microfluidics, is already commercialised by the company SENSIA, SL.

Influence of the number of regeneration cycles on the removal of ammoniacal nitrogen with zeolite clinoptilolite

The aim of this work was to investigate the influence of the number of regeneration cycles on the removal of ammoniacal nitrogen from aqueous solutions with zeolite clinoptilolite (in its sodium or homo-ionic form). In addition, the obtained results were correlated with the physicochemical properties of regenerated homo-ionic zeolites. A unifactorial experimental design, balanced with permanent effects, was applied to assess the removal of ammoniacal nitrogen with homo-ionic zeolites presenting 0–10 sodium regeneration cycles (Z0–Z10). The experimental conditions of trials were as follows: pH 7, contact time was 30 min, stirring speed was 100 rpm, in completely mixed batch reactors. Samples of natural zeolite (ZN without sodium homo-ionization) and homo-ionic zeolites (Z0–Z10) were used to determine their surface properties by using the BET-N2 method (surface area (m2/g), pore volume (cm3/g) and pore diameter (Å)). Other determined properties were the zeta potential (by micro-electrophoresis), percentage of elements (by the X-ray disperse spectrometric method) and particle morphology by scanning electronic microscopy. The results have shown that homo-ionic zeolites had a high removal capacity of ammoniacal nitrogen; this and other properties did not change in a significant way, even after a number of regeneration cycles as high as 10.

Statistical Genetics and Simulation Models in Genetic Resource Conservation and Regeneration

A major objective when regenerating germplasm collections is to maintain as many genes (or alleles) as possible. Two stages, sampling and propagating, can be identified in any regeneration cycle. A rare allele can be lost at either stage, when a cross-pollinated population is being regenerated. The objectives of this study were (i) to derive the theoretical probability that one or a few rare alleles will be retained after one regeneration cycle and (ii) to determine, through computer simulation, the average number of alleles lost after a certain number of regeneration cycles. The effects of four mating methods commonly used on cross-pollinated crops (i.e., random pollen pollination, chain cross, paired cross, and self-pollination) were compared. If more than five seeds are harvested from each regenerated plant, the probability that an allele will be lost during Stage 2 can be ignored. However, harvesting and maintaining more seeds than are required for subsequent regeneration cycles will have some negative effects on the retention of genetic diversity. Self-pollination is the best mating strategy for retaining rare alleles only if the germination rate is 100% and all the reserved seeds are regenerated. It can be used for species where inbreeding depression is not serious and the seeds of individual plants from an accession can be stored separately. Paired cross without reciprocal is recommended for regenerating cross-pollinated species, as it results in the same genetic consequence as paired cross with reciprocal or chain cross, but requires only half the number of labor-intensive crosses.

Adsorption of methyl ethyl ketone and trichloroethene from aqueous solutions onto silicalite fixed-bed adsorbers

This work addresses the adsorption of methyl ethyl ketone (MEK) and trichloroethene (TCE) from aqueous solutions on agglomerated silicalite. Results from both equilibrium and fixed-bed adsorption studies in aqueous solutions are given. The breakthrough curves of MEK could be described adequately with a bidisperse model. It was observed that the mass transfer of MEK is controlled by both the external and the macropore transport. The breakthrough curves of TCE are also adequately described with the same model, for which the micropore resistance was the most important one. The thermal regeneration of the agglomerated silicalite loaded with MEK by passing a purging gas through the bed (nitrogen and air) was also studied. No decrease of the adsorption capacity with the number of regeneration cycles was observed.

N-Octane reforming over modified catalysts: effect of regeneration on the catalyst performance

The effect of multiple oxidation-reduction cycles on the catalyst performance was studied. Pt-Sn-Sn, Pt-Sn-Ir, Pt-Sn-Au and Pt-Sn-Pd supported on g-Al2O3 were compared with the reference Pt-Sn/γ-Al2O3 catalyst in n-octane test reactions. The carbonaceous deposits were burned off from the catalysts after each reaction. The regeneration procedure consisted only two steps: the burn off in air and the reduction in hydrogen. No significant change, as a consequence of the regeneration, was observed in the conversion, the liquid yield and the product distribution, except at the Pt-Sn-Pd and Pt-Sn-Au catalysts. These catalysts lost part of their activity. With the palladium modified catalyst the rupture reactions became more dominant with the number of regeneration cycles. The aromatic part of the product decreased, the isoparaffin part increased in the case of both modified catalysts. The reference, the tin and iridium modified catalysts had stable catalytic performance: the activity and selectivity of the catalysts remained constant after a few oxidation cycles.

Cerium oxide-based catalysts for production of ketones by acid condensation

Cerium oxide-based catalysts proved superior in activity, selectivity, and stability to several other oxides for the condensation of two carboxylic acids to produce non-symmetric ketones. The effects of CeO 2 loading on the catalysts and the addition of more basic or acidic oxides to CeO 2 were also studied. The catalysts were characterized by surface area, XRD, and redox behavior using TGA. CeO 2-based catalysts began deactivating after >12 h operation at WHSV∼4, but could be completely regenerated by high temperature air. The optimum temperature range for methylcyclopropylketone (MCPK) production from acetic and cyclopropanecarboxylic acids (CCA) were 690–730 K, and 670–680 K for methylnonylketone (MNK) production from acetic and decanoic acids. The optimal loadings of CeO 2 on supports approached a monolayer, but the maximum yield appeared almost independent of support. Both acidic and basic oxide additives to CeO 2 increased the rates to isomers of both CCA and MCPK, and to aldol condensation products. Catalyst performance improved with respect to time on stream and the number of regeneration cycles. This behavior resulted from the gradual dispersion of CeO 2 on the support during reduction/oxidation cycles. Acetic acid/air could also be used to activate the catalysts prior to feeding the second acid.

An improvement in the properties of hydrogen storage alloy by copper microencapsulation

A hydrogen storage alloy of LaNi 5 was microencapsulated by electroless chemical plating with metallic copper. The surface morphology of the microencapsulated LaNi 5 was studied for different electroless plating conditions. The deactivation, regeneration, and catalytic activity of LaNi 5 were compared before and after the microencapsulation. The amount of Cu deposited on the LaNi 5 surface increased with increasing concentration of the plating solution. A relatively smooth morphology was obtained by decreasing the plating rate. The extent of the deactivation of the microencapsulated LaNi 5 was very low compared to that of LaNi 5 and decreases with the number of the microencapsulation. Almost complete regeneration was achieved for microencapsulated LaNi 5, but the extent of the regeneration decreased with the number of regeneration cycles at higher temperatures. The microencapsulated LaNi 5 showed a higher catalytic activity for methanation of carbon monoxide, where the conversion was almost quantitative.

Adsorption removal of carbon dioxide from the helium coolant of high-temperature gas-cooled reactors

This paper conducts experiments on the removal of CO/sub 2/ from helium by means of a Soviet-made adsorbent under the conditions characteristic of high-temperature gas-cooled reactor cleaning systems. The adsorption of CO/sub 2/ from helium was studied under dynamic conditions with a fixed layer of adsorbent in a flow-through apparatus with an adsorber 16 mm in diameter. The analysis of the helium was carried out by means of a TVT chromatograph. In order to compare the adsorption of CO/sub 2/ on CaA zeolite under dynamic conditions from the helium stream under pressure with the equilibrium adsorption on the basis of pure CO/sub 2/, the authors determined the adsorption isotherm at 293 K by the volumetric method over a range of CO/sub 2/ equilibrium pressures from 260 to 11,970 Pa. Reducing the adsorption temperature to 273 K leads to a considerable reduction in the energy costs for regeneration, owing to the increase in adsorption and the decrease in the number of regeneration cycles; the amount of the heating gas used is reduced to less than half.

Characteristics of filters from loosely poured metal powders

The stopping power of granular filters from metal powders in the purification of water and nitric acid solutions from mechanical contaminants is comparable to that of sintered P/M filters. A protective layer from a coarser spherical powder fraction located under a fine purification layer improves the latter's hydraulic characteristics and increases its debris holding capacity. The coefficient of effectiveness of regeneration of such a filter by 90-sec flow reversal is equal to 0.98 and is virtually unaffected by the number of regeneration cycles.