Sorbent Mixture Research Articles

МАТЕМАТИЧЕСКОЕ ОБОСНОВАНИЕ ЭФФЕКТИВНОСТИ ДЕЙСТВИЯ СМЕСИ ПРИРОДНЫХ МИНЕРАЛЬНЫХ СОРБЕНТОВ ДЛЯ ОЧИСТКИ МАЛОМИНЕРАЛИЗОВАННЫХ ДРЕНАЖНЫХ ВОД В ЗАВИСИМОСТИ ОТ ТЕМПЕРАТУРЫ

Purpose: to identify the relationship of sorption of a complex sorbent with a temperature factor and its mathematical substantiation. Material and methods. As a material for the study, a complex sorbent obtained from a mixture of perlite and agroionite in a ratio of 27:73 was used. The experiment was carried out in laboratory conditions at different temperatures. At certain intervals, when measuring the total salinity of the solutions, the temperature parameter was also measured. During the study, the air temperature was measured. For the experiment, a model water of three salinity levels: 3.1; 5; 7 g/l was used. The weighed portions of a mixture of sorbents weighing 27.5 g with model solutions, 300 ml each, were placed in a reservoir. Measurements were carried out after 5; 10; 20; 30 min; 1; 2; 24; 48 h using a HI 8733 conductometer from Hanna. Results. As a result of the study, the dynamics of the salinity of the model water under the action of a complex sorbent was obtained, a scatter diagram was constructed. It is a statistical analysis tool, with the help of which the dependence and the nature of the relationship between the two process parameters are revealed. According to the results obtained, it can be concluded that there is a positive relationship in the experiments performed. The efficiency of the process depends on temperature readings with a slight deviation. Thus, at an average temperature of 26.3 °C, the total mineralization index is lower than at an average temperature of 19.8 °C. Conclusions. By constructing a scatter diagram and a matrix scatter diagram, a nonlinear relationship between sorption by a complex sorbent and the temperature factor was revealed.

Residue determination of pyraclostrobin, picoxystrobin and its metabolite in pepper fruit via UPLC-MS/MS under open field conditions

In this study, a new, high-efficiency and sensitive method was determined to simultaneous analyze the residue of pyraclostrobin, picoxystrobin and its metabolite BF-500-3 in pepper fruit using modified QuEChERS pretreatment combined with ultra performance liquid chromatography–tandem mass spectrometry. The clean-up steps of QuEChERS procedure were optimized using the chemometric tools. Models of stepwise regression and surface response demonstrated that the optimal sorbent mixtures were 40 mg nano-zirconia + 10 mg C18 for pyraclostrobin and picoxystrobin and 30 mg nano-zirconia + 20 mg C18 for BF-500-3. The optimized purification procedures provided satisfactory recoveries for all tested fungicides with rates between 91% and 107% and relative standard deviations between 3.7% and 9.6%. The limits of detection and quantification were in the range of 0.0360–0.272 μg/kg and 0.120–0.910 μg/kg. Based on this method, the dissipation of pyraclostrobin, picoxystrobin and its metabolite in pepper fruit were determined under field conditions. Pyraclostrobin and picoxystrobin degraded rapidly with half-lives of 5.53–7.02 and 5.97–7.82 days and 5.09 and 5.68 days in 2016 and 2017, respectively. The residue levels of BF-500-3 increased first and then decreased. The terminal residues of all fungicides were below the maximum residue limits (MRLs). This research can not only provide guidance for the reasonable usage of pyraclostrobin and picoxystrobin in agriculture but also give a reference for the Chinese government to establish the MRL for pyraclostrobin in pepper.

Sorption-enhanced ethanol steam reforming on Ce-Ni/MCM-41 with simultaneous CO2 adsorption over Na- and Zr- promoted CaO based sorbent

In this study, sorption-enhanced ethanol steam reforming (SEESR) is investigated using a Ce-Ni/MCM-41 as a catalyst in the presence of Na or/and Zr promoted CaO-based adsorbents. Ce-Ni/MCM-41 and promoted sorbents were synthesized by wet impregnation method. The catalyst was characterized by XRD, FTIR, TGA, EFSEM, TEM, H2-TPR and N2 adsorption/desorption and promoted sorbents were studied by XRD, EFSEM, BET, TEM and TGA analysis. Sorption experiments were performed to verify sorbent activity for CO2 removing. The results indicated that with doping different promoter on CaO sorbent and also with increasing Na loading, there was an increase in BET surface area, the reduction in particle size and thereupon an enhancement in CO2 sorption capacity. Higher BET surface area, smaller particle size, and superior CO2 sorption capacity were obtained on Na-Zr-CaO sorbent. Sorption-enhanced steam reforming process of ethanol on synthesized catalyst and sorbents were performed at 600 °C and water to ethanol molar ratio of 6. The effect of sorbent to catalyst ratio and the arrangement of sorbent and catalyst (like two separated layers and the mixture of sorbent and catalyst in a single layer) were also studied. The best results were demonstrated on Na-Zr-CaO sorbent and with the separated array. Hydrogen production via a SEESR process with Na-Zr-CaO as sorbent was ∼94% that is 24% more than that of conventional ethanol steam reforming (ESR) reaction.

Numerical simulation of a bubbling fluidized bed reactor for sorption-enhanced steam methane reforming under industrially relevant conditions: Effect of sorbent (dolomite and CaO-Ca12Al14O33) and operational parameters

Sorption-Enhanced Steam Methane Reforming (SE-SMR) is a promising technology for effective production of hydrogen with simultaneous CO2 capture from conventional fuels (e.g. methane, coal) and alternative fuels (e.g. biomass). SE-SMR combines steam methane reforming reaction and water-gas shift conversion reaction with a high temperature CO2 sorption system using a mixture of solid catalyst and sorbent. In this work, a methodology that combines Taguchi robust Design of Experiments (DoE) with previously validated CFD simulations [19] is presented. The main objective is to carry on a multi-criteria analysis of the effect of different sorbents and pretreatments and operation parameters in the response of the 500 kWth bubbling fluidized bed (BFB) reactor installed in the ZECOMIX (Zero Emissions of CarbOn with MIXed technologies) research infrastructure of ENEA. The effect of different sorbents (i.e. naturally occurring dolomite and synthetic CaO-Ca12Al14O33) and pretreatment seems to be negligible at high scales compared with heat and mass transfer mechanisms. Other parameters (i.e. temperature, pressure, particle diameter, gas velocity, bed height, presence of catalyst and sorbent, treatment of sorbent, syngas composition) have been also evaluated. The present methodology can be a useful approach for a preliminary design and optimization of a full-scale SE-SMR reactors.

Comprehensive multiresidue determination of pesticides and plant growth regulators in grapevine leaves using liquid- and gas chromatography with tandem mass spectrometry

Grape leaf, which is known for its nutritional and medicinal properties, is finding increased applications for cuisine and remedial purposes. This article reports a comprehensive analytical method for the identification and quantification of a broad range of pesticides and plant growth regulators (PGRs) in the grape leaf matrix. The sample preparation method for pesticides involved an optimized QuEChERS-based extraction protocol, with subsequent clean-up by the dispersive solid phase extraction (dSPE) using a mixture of sorbents (25 mg PSA + 5 mg GCB + 150 mg MgSO4). The PGRs were extracted with methanol. The performance of the method was investigated and validated for a mixture of 363 pesticides (148 in GC–MS/MS and 203 in LC–MS/MS) and 12 PGRs (LC–MS/MS) in compliance with the analytical quality control criteria of the SANTE/11813/2017 guidelines. The matrix effects were comparatively higher against grape berries. The findings indicated satisfactory recoveries at 10 ng/g and higher levels with precision RSDs less than 20%. This method has potential applications in commercial residue testing laboratories and also for the regulatory compliance check purposes for its lower LOQs compared to the corresponding EU-MRLs.

Improved multi-stage cross-flow fluidized bed classifier

In the present work, improvements to a novel fluidized bed solids classification system previously published by Jayarathna et al. are discussed (Jayarathna et al., 2018 [1]). The system is designed for a high temperature application, namely solids classification in a CO2 capture plant incorporated with a coal-fired power plant. The capture plant is proposed to be equipped with the latest calcium looping technology, fully integrated calcium looping (FICaL). The classifier will be fed with a mixture of sorbent and heat transfer (inert) particles in the real plant at the operating temperature in between 910 °C and 600 °C. Due to the higher temperature it is not possible to use any sensitive process equipment such as filters or metal screens or any mechanically moving parts. Stepwise development of a such a system is explained in the previous publication by the authors (Jayarathna et al., 2018 [1]). In this work, the system is down-scaled into a smaller cold flow system, and zirconia and steel particles are used to mimic the sorbent and heat transfer solids particles in the hot flow system, respectively. Experiments and CFD simulations are carried out for the cold flow classification system. The previous fluidized bed design (Jayarathna et al., 2018 [1]) reached an efficiency of 90% and 99% recovery (10% and 1% loss) of the lighter (zirconia) and heavier (steel) components, respectively, but a 10% loss of sorbent particles in the real system would not be economical. The new modified system reached recovery efficiencies of 97% and 98% (3% zirconia loss and 2% steel loss) of the lighter and heavier component, respectively. CFD is used as a supporting tool in the design process, and also in making improvements to the design. Improvements are made by modifying the classifier geometry such as shape, height and internal design features. The experimental results from the improved classifier are compared with the CFD predictions made by the commercially available CFD software Barracuda® 17.1. Discrepancies between the experimental and simulated results are discussed, and the Barracuda CFD model is recommended as a good simulation tool for such studies and for upscaling the simulations for the hot flow system. The improved solid classifier design obtained good enough classification performances to proceed with upscaling and continue to make further improvements in the hot flow system. The iterative design and modeling effort from this research work has produced a functional, high-efficiency classification concept that can be used for the 1000 μm HT-solids particles and the 175 μm sorbent particles in the full-scale hot-flow system.

Determination of tricyclic antidepressants in human urine samples by the three-step sample pretreatment followed by HPLC-UV analysis: an efficient analytical method for further pharmacokinetic and forensic studies.

In this work, an efficient sample pretreatment method has been developed by combining salt induced-homogenous liquid-liquid extraction, dispersive solid phase extraction, and dispersive liquid-liquid microextraction based on the solidification of floating organic droplet for the extraction of some widely used tricyclic antidepressant (TCA) drugs (nortriptyline, amitriptyline, desipramine, clomipramine, and imipramine) in human urine samples before their determination by high performance liquid chromatography-ultraviolet detection. In brief, the target analytes are first isolated from urine samples into acetonitrile (ACN) separated by adding a salt. Then the obtained ACN phase is treated with a mixture of appropriate sorbents to remove interferences. Afterward, the purified ACN is mixed with menthol as an extractant and rapidly injected into alkaline HPLC-grade water as a preconcentration step. Next, the obtained solution is placed in an ice bath and menthol collects on top of the solution after solidification. The solidified drop is then withdrawn and injected into separation system after dissolving in 10 µL ACN. Under the optimum experimental conditions, extraction recoveries and enrichment factors of the selected drugs ranged from 69-84 % and 345-420, respectively. The limits of detection and quantification were obtained at the ranges of 0.22-0.31, and 0.71-1.1 µg L-1, respectively. The relative standard deviations of the proposed method were ≤ 6 % for intra- (n=6) and inter-day (n=4) precisions at a concentration of 10 µg L-1 (each drug). Finally, the suggested approach was applied to determine of TCA drugs in different patients' urine samples. The method could be applied in further TCAs pharmacokinetic and forensic studies.

Multiresidue Analysis of 113 Pesticides in Different Maturity Levels of Mangoes Using an Optimized QuEChERS Method with GC-MS/MS and UHPLC-MS/MS

In this study, a simple and high-throughput multiresidue pesticide analysis method based on the quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction combined with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) is presented for the determination of 113 pesticides in green and ripe mangoes. Different buffer systems and purification sorbents were optimized to get better recovery. Extracts from mangoes after acid acetonitrile and ammonium acetate extraction were directly injected to UHPLC-MS/MS analysis, whereas other GC-amenable compounds were treated with cleanup approaches with a mixture of sorbents [400 mg primary-secondary amine (PSA) and 400 mg graphitized carbon black (GCB)] for GC-MS/MS analysis. Recoveries for the majority of pesticides at spike levels of 10, 50, and 100 μg/kg were ranged between 70 and 120% with RSD values below 20%. Limits of detection (LODs) were below 4 μg/kg, whereas limits of quantification (LOQs) were below 10 μg/kg. Response linearity was good in the range between 5 and 500 μg/kg. The matrix effect for 56 pesticides by GC-MS/MS analysis exhibited a non-significant matrix effect (≤ 25%) in green and ripe mangoes. For 57 pesticides used for UHPLC-MS/MS analysis, the optimized method in green mango provided no significant matrix effect (≤ 25%) for 63% of the compounds, whereas only for 16 and 21% compounds, the matrix effect was medium (25–40%) and strong (> 40%); the optimized method in ripe mango provided no significant matrix effect (≤ 25%) for 61% of the compounds, whereas only for 26 and 12% compounds, the matrix effect was medium (25–40%) and strong (> 40%). Following the application of a “top-down” approach, the expanded measurement uncertainty was both 21% on average (coverage factor k = 2, confidence level 95%) in green and ripe mangoes. The application of GC-MS/MS and UHPLC-MS/MS coupled with the modified QuEChERS extraction procedures was proved to adequately quantitate these pesticides in different maturity levels of mangoes.

Metal-organic framework and Tenax-TA as optimal sorbent mixture for concurrent GC-MS analysis of C1 to C5 carbonyl compounds

We report a multi adsorbent-based method using combinations of metal-organic frameworks (MOFs) and a commercial sorbent Tenax-TA for sampling and thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) quantification of mixtures of six (C1 to C5) aldehydes. The feasibility of this approach was demonstrated along with the optical analytical conditions for maximum recovery. Optimal TD conditions for adsorption and desorption of aldehydes using MOF-5 (Zn-based MOF)+ Tenax-TA were determined as −25 °C and 150 °C, respectively (purge volume: 100 ml). These conditions yielded good linearity (R2 = 0.997), precision, and high sensitivity. Analysis of the aldehyde mixtures yielded slightly smaller R2 values than the analysis of single species. Additionally, the performance of MOF-5+ Tenax-TA was compared with other combinations comprising of Cu-based MOF-199 and Zr-based MOF of UiO-66 topology. The results of the theoretical modelling analyses propose simultaneous interaction of the C=O group of aldehydes with open metal sites of the studied MOFs and van der Waals interaction of hydrocarbon “tail” of aldehydes with linkers of MOFs. The combined interactions significantly increased the enthalpy (eV/molecule) of formaldehyde adsorption on MOF. Our findings unravel a potential way to extend the application of GC-based detection toward concurrent analysis of organic molecules of variable sizes.

DETERMINATION OF 2,4-D IN SOME FOOD PRODUCTS (MILK, EGGS, LIVER, KIDNEYS) BY CHROMATOGRAPHY METHODS

The modern technique for the determination of 2,4-D, that belongs to global environmental pollutants, including the use of the technology of sample preparation - dispersive solid-phase-liquid extraction (QuEChERS), new for products of animal origin, has been developed. The sample preparation procedure includes the steps of: preliminary freezing of the sample to be analyzed, extraction with acetonitrile containing 1% acetic acid in the presence of MgSO4 and NaCl, purification by dispersive solid-phase extraction using a mixture of sorbents based on primarysecondary amine, octadecylsilane and graphitized carbon black, the freeze of the solution - at the last stage. Using the proposed technique allows to isolate the desired component from a matrix with a high content of animal fat into a selected organic solvent with high efficiency, that made it possible to expand significantly the arsenal of analytical equipment used to detect residual amounts of 2,4-D in food products of agricultural production, for example milk, eggs and offal (liver, kidney): tandem liquid mass-spectrometry (HPLC-MS/MS), gas-liquid chromatography with mass-selective and electron-capture detectors (GLC-MSD, GLC-ECD). The lower limit of the quantitative determination is 2,4-D: 0,005 mg/kg for milk and eggs, 0.05 mg/kg for the liver and kidneys. Completeness of extraction is 85-94%, RMS of repeatability is 3,4-11,4%.

Uranium(VI) adsorption and surface complexation modeling onto vadose sediments from the Savannah River Site

Uranium U(VI) adsorption was measured as function of pH (3–10) on goethite, kaolinite, quartz, two binary mixtures of goethite and kaolinite, and a vadose zone sediment collected on The Department of Energy’s Savannah River Site (SRS), the clay mineral fraction of which is composed largely of kaolinite and goethite. Diffuse-layer surface complexation models were parameterized using the code PEST together with PHREEQC to fit U(VI) sorption data for the pure goethite, kaolinite, and quartz. U(VI) adsorption on kaolinite and goethite was modeled as the formation of two bidentate U(VI) complexes at mineral edge sites on a variable charge site. U(VI) adsorption on quartz was described using a one-site diffuse-layer with the formation of bidentate complex on a variable charge site. These models were used to predict U(VI) adsorption on the binary sorbent mixtures and the SRS sediment using a simple component-additivity approach. In general, the predicted adsorption edges were in good agreement with measured data, with statistically similar goodness of fit compared to that obtained for the pure mineral systems.

Determination of bisphenols with estrogenic activity in plastic packaged baby food samples using solid-liquid extraction and clean-up with dispersive sorbents followed by gas chromatography tandem mass spectrometry analysis

Bisphenols (BPs) are a family of chemicals with known endocrine disrupting activity. Bisphenol A (BPA) is the most representative prototype of this group of chemicals. Recently, the use of BPA, a prototype of endocrine disruptors, has been reduced and replaced with structural analogs due to its negative effects on both the environment and consumers. In this work, a new method is presented for the determination of seven BPs, with estrogenic activity in ready-to-eat plastic packaged baby foods. The procedure involves the isolation of the analytes using solid-liquid phase extraction with acetonitrile followed by a clean-up step with a mixture of dispersive-SPE sorbents (C18 and PSA) and magnesium sulphate, to reduce matrix effect from proteins, sugars and lipids. Extraction parameters were optimized using multivariate optimization methods. The compounds were detected and quantified by gas chromatography tandem mass spectrometry (GC–MS/MS). The limits of quantification were between 0.1 and 1.2ngg−1 for the studied analytes. The method was validated using matrix–matched calibration and recovery assays with spiked samples. Recovery rates were between 91% and 110% and % RSD was lower than 13% in all cases. The method has been successfully applied for the determination of these endocrine disrupting chemicals (EDCs) in samples of a novel type of food consumed by pre-schoolers. This is the first study to analyze EDCs in plastic packaged foods consumed by this target group.

Application of surface complexation modeling to trace metals uptake by biochar-amended agricultural soils

Biochar has emerged as a useful amendment to release nutrients into agricultural soil, to increase crop productivity, and as a sorbent to remediate metals and organics contamination. Since soils have heterogeneous physical properties across a given crop field, and even over a growing season, it is imperative to select the most appropriate biochar for the intended purpose and in defining the amendment level. In this study, we investigate the adsorption of Cd(II) and Se(VI) as model pollutant cations and anions, respectively, to two agricultural soils amended with a wood pin chip biochar (WPC). The proton reactivity of each sorbent was determined by potentiometric titration, and single-metal, single-sorbent experiments were conducted as a function of pH. The resulting data were modeled using a non-electrostatic surface complexation modeling (SCM) approach to determine the proton and metal binding constants and surface functional group concentrations of each soil and WPC. The SCM approach is a considerable advance over empirical modeling approaches because SCM models can account for changes in pH, ionic strength, temperature, and metal-to-sorbent ratio that may happen over the course of a growing season. The constants derived from the single-metal, single-sorbent experiments were then used to predict the extent of metal adsorption in more complex mixtures of Cd, Se, soil and WPC. Overall the SCM approach was successful in predicting metal distribution in multi-component mixtures. In cases where the predictions were poorer than expected, we identify reasons and discuss future experiments needed to further the application of SCM to sorbent mixtures containing biochar.

Investigate the influence of halloysite and activated carbon mixtures in phytostabilization of Pb-contaminated soil with Lolium perenne L.

Abstract A pot experiment was conducted to investigate the effects of halloysite and activated carbon mixtures on the biomass and distribution of macronutrients (Mg, K, Ca, Na, P) in ryegrass grown in Pb-contaminated soil. The soil was spiked with four different levels of lead contamination, i.e. 0 (control), 200, 400, 800 mg·kg−1 were applied in an analytical grade Pb(NO3)2 solution mixed thoroughly with the soil. Raw halloysite (3%) and activated carbon (1% relative to soil mass) mixtures were used to reduce the effect of soil lead contamination. Ryegrass of the Bokser variety was harvested after 42 days, and soil samples were collected for laboratory tests. The mixture of sorbents applied in the experiment which turned out to be most effective at doses of lead amounting to 400 and 800 mg·kg−1 of soil, with the increase in the yield of ryegrass being the highest. Increasing contamination of soil with lead in the series without the mixture of sorbents increased the contents of phosphorus, sodium, calcium and magnesium in ryegrass. The applied mixture of halloysite and activated carbon changed the macronutrient concentration in ryegrass, with the greatest changes found in that of potassium and sodium.

Leaching and retention of dissolved metals in particulate loaded pervious concrete columns

This study examined metal leaching and retention in pervious concrete with or without embedded particulate matter. Particulate matter was collected from an adjacent parking lot and from a nearby parking garage as examples of weathered and un-weathered particulate matter. Particle size distributions were similar, but metal content was 3–35-fold higher and organic matter content was 3-fold higher in the parking garage particulate matter compared to the parking lot particulate matter. Replicate columns were established with either no particulate added as the control, or 20 g of parking lot or parking garage particulate matter. Synthetic rainwater was passed through the columns at variable rainfall intensity or fixed intensity to assess leaching. Metals were leached at higher concentrations from the parking garage particulate amended column, but from all columns less than 1% of the metal mass leached. Rainfall intensity did not have a large effect on leached metal concentrations, only varying effluent by about 2-fold. Synthetic stormwater with elevated dissolved Cu, Zn, Cd and Pb concentrations was passed through the same columns and metal removal efficiencies were on the order of 85–95%, 30–95%, 60–90%, and 95+% for each metal, respectively. After loading the column with a year's worth of stormwater metal exposure, removal efficiencies in the no particulate and parking lot particulate amended columns decreased, while parking garage particulate amended columns performed similarly with a small drop in Cu and Pb removal efficiencies. Generally, columns with no particulate and parking lot particulate amendments performed similarly, suggesting the pervious concrete is responsible for the majority of the initial metal retention. The parking garage particulate amended columns retained more metals from stormwater, perhaps due to an increase in pH that promoted surface precipitation as hydroxides or carbonate species on the pervious concrete, or due to complexation in the higher concentrations of organic matter and iron oxides in the particulate matter. Overall, metal retention was aided by the presence of organic matter in the particulate matter, but the pervious concrete itself was more important than particulates for metal retention. A strategy to increase metal retention and removal from the environment could involve amending pervious concrete with mixtures of well-defined sorbents to enhance metal retention.

In-line micro-matrix solid-phase dispersion extraction for simultaneous separation and extraction of Sudan dyes in different spices

A novel, simple, fast, and miniaturized method, termed in-line micro-matrix solid-phase dispersion (in-line MMSPD), coupled with high performance liquid chromatography (HPLC) was developed for the simultaneous extraction and determination of Sudan dyes (i.e. Sudan I–IV, Sudan orange G, Sudan black B, and Sudan red G) with the aid of an experimental design strategy. In this method, a matrix solid-phase dispersion (MSPD) column including a suitable mixture of polar sorbents was inserted in the mobile phase pathway, and while the interfering compounds were retained, the analytes were eluted and entered into the analytical column. In this way, the extraction, elution, and separation of the analytes were performed sequentially. Under the optimal experimental conditions (including the amount of sample, 0.0426g; amount of dispersant phase, 0.0216g of florisil, 0.0227g of silica, 0.0141g of alumina; and blending time, 112s), the limits of detection (LODs), limits of quantification, linear dynamic ranges, and recoveries were obtained to be 0.3–15.3μgkg−1, 1–50μgkg−1, 50–28,000μgkg−1, and 94.5–99.1%, respectively. The results obtained showed that determination of the selected Sudan dyes in food samples using an enough sensitive and a simple analytically validated method like in-line MMSPD may offer a suitable screening method, which could be useful for food analysis and adulteration.

Enhanced hydrogen production by sorption-enhanced steam reforming from glycerol with in-situ CO2 removal in a fixed-bed reactor

For the fixed-bed reactor configuration in the sorption-enhanced steam reforming process (SERP), solid mixture of catalyst and sorbent is stationary and alternatively exposed to reaction and regeneration conditions for multi-cycles by periodically switching the feed gases for enhanced hydrogen production with in-situ CO2 removal. A NiO/NiAl2O4 catalyst was synthesized by the co-precipitation method with rising pH technique and the crystalline spinel phase of NiAl2O4 was formed under the calcination temperature of 900°C. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermo-gravimetric analysis (TGA), and N2 adsorption–desorption. The non-stoichiometric thermodynamic calculation was carried out to determine the effects of temperature and in-situ CO2 removal on the enhancement of hydrogen production by SERP from glycerol at 425–700°C. The multi-cycles on reaction and regeneration for hydrogen production by SERP from glycerol were performed by NiO/NiAl2O4 catalyst and CaO based sorbent in a fixed-bed reactor. The results showed that hydrogen production by SERP can be clearly divided into three periods, and the experimental gaseous products were compared with non-stoichiometric thermodynamic calculations. It is obvious that H2 purity was greatly increased, and CO2, CO and CH4 concentrations were reduced by in-situ CO2 removal during the pre-breakthrough period. It is found that enhanced hydrogen production was mainly depended on in-situ CO2 removal. The operation durations for producing high-purity hydrogen of more than 90% were decreased with the increase of the cycles. It may due to the decrease in the reactivity of CaO based sorbent after multi-cycles reaction and regeneration.

Application of the QuEChERS procedure and LC–MS/MS for the assessment of neonicotinoid insecticide residues in cocoa beans and shells

The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure was applied and validated for the analysis of neonicotinoid insecticide residues in cocoa bean matrix with high fat and high pigments. Samples employed in the study were fermented and dried beans obtained from major cocoa producing regions in Ghana where neonicotinoids are extensively used. Shells covering the beans were removed and analyzed separately to examine insecticide distribution. Analytes in both matrices were extracted in acetonitrile with sodium acetate and magnesium sulfate salts, cleaned up using a sorbent mixture of primary secondary amine (PSA), C18 and graphitized carbon black (GCB), and quantified using liquid chromatography tandem mass spectrometry (LC–MS/MS). Average recoveries at four levels of fortification ranged from 92 to 111% with relative standard deviation of ≤16% for all analytes. Limits of quantification ranged from 3 to 10μg/kg for all neonicotinoids. Imidacloprid was the most frequently encountered neonicotinoid and was quantified in more than 10% of deshelled bean and 30% of cocoa shell samples, with concentrations ranging from 11.5 to 35.6μg/kg and 11.8 to 214μg/kg in cocoa beans and shells, respectively. The findings from this study suggest a need for greater efficiency in neonicotinoid application, to avoid the build-up of these insecticides to unsafe levels in cocoa beans.

Catalytic performance of Ni/CaO-Ca5Al6O14 bifunctional catalyst extrudate in sorption-enhanced steam methane reforming

In this work, mm-sized shaped Ni/CaO-Ca5Al6O14 bifunctional catalyst extrudates were prepared by extruding sol–gel-derived Ni/CaO-Ca5Al6O14 powder, and applied to the sorption-enhanced steam methane reforming (SESMR) process. The Ca5Al6O14-stabilized bifunctional catalysts exhibited higher stability and CaO utilization efficiency than that of Ni/CaO when subjected to 50 carbonation–calcination cycles for CO2 capture, indicating the positive effect of Ca5Al6O14 incorporation. The Ni/CaO-Ca5Al6O14 extrudates possessed good activity and stability over 10 SESMR cycles, and showed advantages over the use of catalyst and sorbent mixture, including an extended prebreakthrough time and a higher catalytic activity. In particular, the Ni/CaO-Ca5Al6O14 extrudate consisting of 15wt% (mass fraction) Ni, 61.7wt% CaO and 23.3wt% Ca5Al6O14 provided high activity and stability for the SESMR process, even at a low H2O/CH4 molar ratio of 2 over 20 SESMR cycles. These results clearly demonstrate that the Ni/CaO-Ca5Al6O14 extrudate is an interesting candidate for the SESMR process.

Sorption-enhanced steam reforming of glycerol on Ni-based multifunctional catalysts

The Ni-based multifunctional catalysts for the sorption-enhanced steam reforming process (SERP) with simultaneous in-situ CO2 removal were synthesized by the co-precipitation method with rising pH technique, and the crystalline spinel phases of NiAl2O4 and MgAl2O4 in the catalysts were formed under the calcination temperature of 900 °C. The catalysts were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analysis (TGA), and N2 adsorption-desorption. Nonisothermal and isothermal CO2 sorption experiments were carried out to evaluate the activity of catalysts for CO2 removal. Desorption and optimum sorption temperatures for CO2 removal were determined. Hydrogen production from SERP of glycerol over the multifunctional catalysts has been experimentally evaluated under 550 °C and steam to carbon (S/C) ratio of 3. The multifunctional catalyst with the composition of 41.21 wt% NiO, 28.02 wt% Al2O3 and 30.77 wt% CaO presented satisfactory hydrogen purity in the multi-cycles of reforming and regeneration processes. Enhanced hydrogen production was mainly depended on in-situ CO2 removal, and the operation durations for producing high purity hydrogen in the initial 30 min were relatively stable. The multifunctional catalyst possesses uniform distribution of Ni, Ca and Al, contributing significantly to the excellent CO2 sorbent capacity and reforming activity. This multifunctional catalyst synthesized offers a new scheme other than the conventional mixture of sorbent and catalyst for SERP.