Alkaline Source Research Articles

Efficient photocatalytic degradation of ethylenethiourea with zinc oxide photocatalysts: Parameters optimization, mechanism insight, exploration of degradation pathways and toxicity assessment

Traditional advanced oxidation processes (AOPs) for the removal of toxic and refractory ethylenethiourea (ETU) is uneconomical because of the demand for continuous chemical input and full-scale systems. Herein, ETU was efficiently mineralized without sacrificial reagents for the first time through the utilization of ZnO nano-photocatalysts which were synthesized by the adjustment of ratio between the precursor ZnCl2 and alkaline source KOH during hydrothermal process. Compared to other ZnO samples, ZnO-1/3 (1:3 molar (M) ratio of ZnCl2 to KOH) exhibited higher apparent rate constant (0.00661 min−1) towards the degradation of ETU because of more effective electron-hole separation. The optimum conditions for ETU degradation (ZnO-1/3 dosage of 0.4 g/L, initial ETU concentration of 10 mg/L and photocatalytic reaction temperature of 35 °C) were acquired according to the outcome of the response surface methodology (RSM) based on the Box-Behnken design (BBD), and the predicted maximum removal efficiency of ETU reached 93.17 % and was consistent with the experimental results under this optimum conditions. The h+ and •OH were proved to the main reactive species during the photocatalytic process by the free radical capture experiments and electron spin resonance (ESR) analysis. Furthermore, the possible degradation pathways of ETU were suggested based on the identified degradation intermediates, and the reduced toxicity of intermediates was also demonstrated through the quantitative structure–activity relationship (QSAR) prediction and the growth of mung bean seedlings. Hence, photocatalysis with ZnO can be regarded as a promising alternative for ETU elimination.

A simulation-based approach for understanding CO2 capture and mineralization dynamics in desalination brine

In the pursuit of sustainability, it is crucial to repurpose waste resources into valuable chemicals. One promising avenue is sequential CO2 mineralization using natural seawater or desalination brine solution, which concurrently removes CO2 from the atmosphere while recovering valuable minerals. To realize this approach, it is paramount to grasp the factors influencing the process efficiency and product composition. Here, we present a simulation approach using the visual MINTEQ v3.1 and PHREEQC v3.7.0 models to investigate the impact of CO2 concentration and OH− (as an alkaline source) on the mineral recovery process. The findings reveal that both CO2 concentration and OH− significantly influence the mineral phase composition. Specifically, higher CO2 flow rates or elevated OH− levels promote calcite formation while suppressing the brucite phase, with limited hydromagnesite formation. Moreover, an interactive effect between OH− and CO2 is observed, with OH− essential for carbonate formation. We further validated these insights through preliminary experiments employing electrochemical methods as a source of OH−, wherein aqueous CO2 and applied current density (proportional to OH− concentration) regulated mineral phase composition. Notably, the weight percentage of the brucite phase in the precipitates ranged from 67 % to 73 %, while the calcite phase varied from 20 % to 26 % with alterations to the applied electric currents. The present study not only provides valuable insights into the recovery of potential elements and efficient capture of CO2 in non-synthesized brine solution with a combined theoretical and experimental approach but also demonstrates the viability of employing electrochemical-driven methods as a greener alkaline source for CO2 capture and mineral recovery.

Directly synthesis of H-form ZSM-5 zeolites with n-butylamine in the presence of seed and ethanol

In the research of directly synthesizing H-form ZSM-5, ammonium hydroxide is commonly used as an alkali source instead of NaOH to avoid multiple ion exchange steps. However, the volatile nature and the lack of structure-directing effect of ammonium hydroxide limit its application in practical. In this study, n-butylamine (NBA) was used as the main alkali source to directly prepare HZSM-5 zeolites with SiO2/Al2O3 ratios ranging from 40 to 300 under traditional hydrothermal conditions. The influence of the amount of NBA, ethanol, seed, and pre-crystallization on the synthesis products was investigated under the condition of SiO2/Al2O3 = 80. Theoretical simulation suggested that n-butylamine cations (NBA+) play the most potent directing role in the formation of the MFI structure but could lead to difficulties in removal during calcination. The addition of ethanol as the zeolite growth modifier (ZGM) could decrease the usage of NBA and reduce the difficulties in calcination, and the addition of seed provided the conditions for initiating crystallization in the system that could not spontaneously nucleate. HZSM-5 with different SiO2/Al2O3 ratios were prepared under the optimal crystallization conditions, and the as-synthesized samples exhibited superior textural and acid properties compared to commercial zeolite. Finally, the 1 L scale-up synthesis and MTP reaction were conducted to demonstrate the practicality of this economically and environmentally-friendly synthesis strategy.

Influence of alkaline sources for the electrochemical performance of NiCo layered double hydroxide nanostructures

The morphology and composition of nanostructures play important role in their electrochemical properties. Herein, NiCo layered double hydroxide (LDH) nanostructures were prepared by hydrothermal method with NaOH, urea and ammonia as alkaline sources, respectively. The types of alkaline can affect the morphology of the obtained NiCo LDH nanostructures. Compared with the NaOH as alkaline source, NiCo LDHs with urea and ammonia as alkaline sources exhibit obvious nanoflower structure. And the electrode corresponding to ammonia has the highest specific capacity (1498.98 F/g) at a current density of 1 A/g. And the dosage of ammonia was also influenced the composition of the obtained NiCo LDH nanostructures. Moderate ammonia dosage (0.9 mL) would ensure the purity of NiCo LDH, and achieve high specific capacity and high retention rate (82.9 %) at high current density (10 A/g). These obtained results can provide a new idea and sight for the promotion of the related electrochemical devices based on NiCo LDH materials.

Factors Controlling Organic Matter Enrichment in Alkaline Lacustrine Source Rocks: A Case Study of the Late Paleozoic Fengcheng Formation in the Junggar Basin, NW China

AbstractThe late Paleozoic Fengcheng Formation shale (LPF shale) in the Junggar Basin, NW China, is the oldest alkaline source rock discovered in the world, providing a unique perspective with which to explore organic matter (OM) enrichment in alkaline lake environments. Combined with the organic carbon isotope profile and paleoenvironmental proxies, this study reveals that the LPF shale was deposited in an arid climate with high salinity and a strong reducing environment, accompanied by frequent volcanic activity. High TOC values are concentrated in two intervals with frequent fluctuations in OM types. A negative excursion due to changes in sedimentary OM source is found in the δ13Corg profile. The excursion corresponds to the OM enrichment interval and is accompanied by abnormally high values of Sr/Ba and Sr/Cu. This implies that the extreme arid climate has led to high salinity, resulting in strong reducibility and changes in paleontological assemblages, which in turn controlled the differential enrichment of OM. The Fengcheng Fm. high‐quality source rocks are the result of the combined action of climatic events, volcanism, high‐salinity water environment and superior hydrocarbon‐generating organisms. The results provide new insights into the formation conditions of terrestrial alkaline high‐quality source rocks and the factors controlling alkaline OM enrichment.

Direct Extraction of Sodium Hydroxide by Calix[4]pyrrole-Based Ion-Pair Receptors.

Described in this work are calix[4]pyrrole-based ion-pair receptors, cis/trans-1 and cis/trans-2, designed for the extraction of sodium hydroxide. An X-ray diffraction analysis of a single crystal of the cis-1·NaOH isomer isolated from a mixture of cis/trans-1 revealed a unique dimeric supramolecular structure. An average dimer in toluene-d8 solution was inferred on the basis of diffusion-ordered spectroscopy (DOSY). Support for the proposed stoichiometry came from density functional theory (DFT) calculations. The structural stability of the dimeric cis-1·NaOH complex in toluene solution was further confirmed by ab initio molecular dynamics (AIMD) simulation with explicit representation of solvent. Under conditions of liquid-liquid extraction (LLE), purified receptors cis- and trans-2 were both found to remove NaOH from a pH 11.01 aqueous source phase into toluene with extraction efficiencies (E%) of 50-60% when used equimolar to NaOH. However, in all cases, precipitation was observed. Complexities associated with precipitation could be avoided by immobilization of the receptors onto a chemically inert poly(styrene) resin by means of solvent impregnation. The use of solvent-impregnated resins (SIRs) eliminated precipitation in solution while retaining the extraction efficiency toward NaOH. This allowed both the pH and salinity of the alkaline source phase to be lowered.

Synthesis of a novel In2O3 hollow cube using in-situ partial oxidation with enhanced gas sensing platform to detect C3H8

Indium oxide hollow cubes were made using a simple hydrothermal technique and calcination process, its crystalline form was cubic bixbyite-type, and had high purity of the calcined sample. Urea was selected as alkaline source, which was capable of cooperating with In3+ to create indium-urea complexes, hindering the growth of certain surfaces, further controlled the shape of the product. Comparing with In2O3 prepared with different amounts of urea, it was found that the best performing In2O3 hollow cube (In2O3-5) synthesized at a molar ratio (InCl3:CH4N2O) of 1:5, its form was a hollow cubic structure made of regular spherical particles stacked, possessed a relatively large specific surface area (64.9 m2/g) which was 1.2 times greater than In2O3-1, and it had smallest grain size (15 nm) compare with In2O3-1 (28 nm), In2O3-3 (23 nm), In2O3-8 (16 nm), and In2O3-10 (20 nm). The In2O3-5 sensor's sensitivity peaked at 180 °C, which is its ideal operating temperature (response value could reach 84.1), the response recovery time was 9s, also exhibited excellent selectivity for C3H8 (CO: 21.7, C2H4: 24.8, C2H5OH: 28.6, H2: 17.9 and H2S: 12.2). The results showed that In2O3-5 with a hollow cube structure formed more necessary channels for vacant oxygen species transport and further contributed to the sensitivity of the material to gases.

Sensitive determination of polybrominated diphenyl ethers (PBDEs) in water and milk by effervescence-enhanced switchable hydrophilic-hydrophobic solvent-based salting-out microextraction and high-performance liquid chromatography with photodiode array detection (HPLC-PDA)

Here is reported effervescent reaction-enhanced switchable hydrophilic-hydrophobic solvent-based salting-out microextraction (ERSSM) with high-performance liquid chromatography with photodiode array detection (HPLC-PDA) for the preconcentration, extraction, and trace-level determination of polybrominated diphenyl ethers (PBDEs) in milk and water. The important variables were rigorously optimized to be 150 µL of hexanoic acid as the extraction solvent, 400 µL of Na2CO3 as the alkaline source, 350 µL of H2SO4 solution as the acid source, and NaCl as the salting-out agent. The optimized conditions provided a linear range from 0.2 to 50 µg L−1 with limits of detection and quantitation from 0.026 to 0.085 µg L−1 and 0.087 to 0.28 µg L−1 for six PBDEs. The intra-day and inter-day precision values were from 2.48% to 6.75%, and the fortified recoveries for PBDEs were between 78.06% and 103.07% in water and milk samples. The developed procedure avoids the use of a traditional organic disperser and mechanical mixing allowing the determination of PBDEs outdoors by synchronous extraction method and high efficiency for the analytes. These advantages suggest a high potential for the routine monitoring of PBDEs in liquid food and environmental samples.

Detection and quantitative evaluation of pumping distress on bridge deck pavement through field and laboratory experiments

Pumping distress refers to the phenomenon of dynamic water entering a pavement, soaking the cement concrete layer to form slurry, and being pumped out of the pavement void under the action of traffic loading. Pumping distress is frequently reported in high temperature and rainy regions, such as Sichuan province in China. Various factors contribute to pumping distress on bridge decks, but most of these factors have merely been subjected to qualitative assessment. The aim of the study is to conduct a comprehensive quantitative analysis through three years of field investigations and laboratory experiments. The field investigations include ground penetrating radar (GPR), pavement permeability tests, skid resistance tests, and drainage facilities surveys. The quantitative analysis of the field and laboratory inspections revealed that the formation reason, deterioration rate, and damage degree of pumping distress were different between the truck and emergency lanes. The occurrence of pumping distresses was significantly related to the uneven construction of the bridge deck leveling layer, compaction segregation, and poor drainage. Additionally, the influence of pavement thickness uniformity on pumping distress was evaluated by incorporating GPR techniques. Failure in the waterproof adhesion layer resulted in the barrier between the cement concrete deck and the asphalt mixture breaking, which allowed alkaline sources to move and transfer to the pavement layer easily. The outcomes of this study can help bridge authorities and construction contractors choose appropriate design and construction measures to prevent pumping distress.

Optimization of Fly Ash—Slag One-Part Geopolymers with Improved Properties

One-part geopolymer concrete/mortar is a pre-mixed material made from industrial by-products and solid alkaline activators that only requires the addition of water for activation. Apart from being environmentally friendly, it also reduces complexity and improves consistency in the mixing process, leading to more efficient production and consistent material properties. However, developing one-part geopolymer concrete with desirable compressive strength is challenging because of the complexity of the chemical reaction involved, the variability of the raw materials used, and the need for precise control of curing conditions. Therefore, 80 different one-part geopolymer mixtures were compiled from the open literature in this study, and the effects of the constituent materials, the dosage of alkaline activators, curing condition, and water/binder ratio on the 28-day compressive strength of one-part geopolymer paste were examined in detail. An ANN model with the Levenberg-Marquardt algorithm was developed to estimate one-part geopolymer's compressive strength and its sensitivity to binder constituents and alkaline dosage. The ANN model's weights and biases were also used to develop a CPLEX-based optimization method for achieving maximum compressive strength. The results confirm that the compressive strength of one-part geopolymer pastes increased by increasing the Na2O content of the alkaline source and the slag dosage; however, increasing the Na2O content in alkaline sources beyond 6% by fly ash weight led to decreasing the compressive strength; therefore, the optimum alkaline activator dosage by weight of fly ash was to be 12% (i.e., 6% Na2O). The proposed ANN model developed in this study can aid in the production and performance tuning of sustainable one-part geopolymer concrete and mortar for broader full-scale applications.

The Preparation and Physicochemical Analysis of Local Black Soap from Coconut Oil and Plantain Peel Biochar

Local black soap, produced from coconut oil and plantain peel biochar (alkaline source) was presented in this study since the agricultural raw materials gain significance in environmentally benign feedstocks for saponification reactions. The physicochemical analysis of the coconut oil and plantain peel biochar shows remarkable free fatty acid (FFA) and alkalinity contents respectively suitable for soap making. The physicochemical properties of the as-prepared local black soap demonstrated a good moisture content (15.1 %) showing that it can be stored for long periods without any water-associated deteriorations. The percentage of matter insoluble in water (4.4 %), matter insoluble in alcohol (12.3 %), FFA content (2.1 %), and pH (9) were found to be higher than the acceptable limit according to the Nigerian Industry Standards (NIS). Also, the total fatty matter (TFM) was higher (67.6 %) than the minimum acceptable level with a good foam height of 2.5 cm. The overall results show good soap properties and are suitable for domestic purposes.

Simulating the source waters for the Wilkins Peak Member evaporite sequence with modern soda spring analogues

Chemical sediments of the lacustrine Wilkins Peak Member of the Eocene Green River Formation potentially preserve detailed paleoclimate information relating to the conditions of their formation and preservation within the lake basin during the Early Eocene Climatic Optimum. The Green River Formation comprises the world's largest sodium-carbonate evaporite deposit in the form of trona (Na2CO3⋅NaHCO3⋅2H2O) in the Bridger Basin and nahcolite (NaHCO3) in the neighboring Piceance Creek Basin. Modern analogues suggest that these minerals necessitate the existence of an alkaline source water. Detrital provenance geochronometers suggest that the most likely source for volcanic waters to the Greater Green River Basin is the Colorado Mineral Belt, connected to the basin via the Aspen paleoriver.Here, we test the hypothesis that magmatic waters from the Colorado Mineral Belt could have supplied the Greater Green River Basin with the alkalinity needed to precipitate sodium-carbonate evaporites that are preserved in the Wilkins Peak Member by numerically simulating the evaporation of modern soda spring waters from northwestern Colorado at various temperature and atmospheric pCO2 conditions. The resulting simulated evaporite sequence is then compared to the mineralogy and textures preserved within the Wilkins Peak Member. Simulated evaporation of Steamboat Springs and Mineral Spring waters produce a close match to core observations and mineralogy. These simulations provide constraints on the salinities at which various minerals precipitated in the Wilkins Peak Member as well as insights into the regional temperature (>15 °C for gaylussite and trona; >27° for pirssonite and trona) and pCO2 conditions (<1200 ppm for gaylussite and trona) during the Early Eocene Climatic Optimum.

Potential of industrial waste as alternative alkaline activator for development of eco-efficient mortars

The alkali-activated materials (AAMs) design can be viewed as one of the most investigated fields in building materials engineering. However, despite numerous studies aimed at the utilization of various precursors, very limited attention is paid to the utilization of waste alkali sources as an alternative to commercial activators. In this regard, this study provides a novel approach to the utilization of industrial waste alkalis as a replacement for commercial alkali activators to reduce costs and reduce the environmental burden. The main innovation consists in the utilization of a waste-cleaning solution (SWCA) as an alternative alkaline activator for blast furnace slag to improve the environmental and economic efficiency and preserve functional properties. The functional properties of designed alkali-activated mortars are described by the setting time, pore size distribution, and mechanical strength. To comply with sustainable measures, the carbon dioxide emissions and costs analysis associated with the material production are carried out. The obtained results reveal the great potential of waste alkaline sources as a replacement for commercial activators. The increase in the applied SWCA concentration induced a shortening in the initial setting time from 240 to 120 min and the final setting time from 480 to 245 min. The designed mixtures reached a satisfactory level of mechanical strength (25 MPa) in comparison to low-grade cement mortars together with a substantial reduction in environmental burden excluding the avoided production. Specifically, a carbon footprint of 75 kg/m3 CO2 equivalent was achieved which represents 5 times lower values compared to low-grade concrete and even better value than AAMs based on a commercially-produced activator. Significant improvements were achieved also in cost efficiency per cubic meter as it was dropped to approx 40 €/m3, thus designed alkali-activated mortars provide better cost efficiency per cubic meter over traditional binders. The findings show that AAMs based on waste alkaline activator should of particular attention to materials science as lowers the consumption of energy-intensive sources and represent a valuable step toward a circular economy.

Use of activated quartz powder as an alkaline source for producing one-part Ca-rich slag based cementitious materials: Activation mechanism, strength, and hydration reaction

As one of the most typical mineral phases in the mine tailings (MTs), the reactivity of quartz has a remarkable influence on the hydration properties of MTs based cementitious materials. In this study, the pure quartz powder (QP) through the alkali-hydrothermal activation was used as an alkaline source for producing one-part Ca-rich slag based cementitious materials (OPM), and the activation mechanism of QP, compressive strength, hydration heats, hydration reactants, and microstructure of OPM samples were investigated, which contributes to evaluate the performance of MTs-based cementitious materials. The reactivity of crystalline QP was enhanced via an alkali-hydrothermal treatment at 200–300 °C in the presence of NaOH. Sodium silicate reactant in the activated QP can dissolve in water to release OH− and Si species, making it an alkaline source for the OPM preparation. Just like cement, OPM samples were synthetized by only adding water to the mixture of activated QP and Ca-rich slag. Appropriate ratios of starting materials were beneficial for the increase in hydration rate, generation of numbers of hydration products, and refinement of microstructure of OPM samples. When the weight ratio of activated QP and slag was 40:60, the OPM sample showed a 28-day strength of 47.6 MPa. Based on the Chinese GB/T 175–2007 standard, this strength development reaches the requirement of 42.5 cement and exhibits the possibility that the OPM sample may be applied in the general construction field.

Alteration at the Base of the Siccar Point Unconformity and Further Evidence for an Alkaline Provenance at Gale Crater: Exploration of the Mount Sharp Group, Greenheugh Pediment Cap Rock Contact With APXS

AbstractChemical data acquired by Curiosity's Alpha Particle X‐ray Spectrometer during examination of the contact between the upper Mount Sharp group and overlying Stimson formation sandstones at the Greenheugh pediment reveal compositional similarities to rocks encountered earlier in the mission. Mount Sharp group strata encountered below the Basal Siccar Point group unconformity at the base and top of the section, separated by &gt;300 m in elevation, have distinct and related compositions. This indicates enhanced post‐depositional fluid flow and alteration focused along this contact. Sandstone targets exposed immediately above the unconformity have basaltic compositions consistent with previously encountered eolian Stimson formation sandstones, except at the contact, where they show the addition of S. Resistant sandstone outcrops above the contact have higher K, Mn, and Na and lower Ni concentrations that primarily reflect changes in provenance. They are compositionally related to cap rock float blocks encountered as Curiosity climbed through the Mount Sharp group, and Bradbury group sandstone outcrops. The higher K, pediment sandstones are interpreted to have a similar provenance to some Bradbury group sandstones, further evidence for widespread, alkaline source rock within and/or in the vicinity of Gale crater. The Bradbury and Siccar Point groups may both be younger than the Mount Sharp group. Alternatively, an alkaline source area in and around Gale crater has been eroded by both water and wind at different times (both before and after deposition of the Mount Sharp group), during the evolution of the crater and its infill.

The Effect of Sodium and Magnesium Sulfate on Physico-Mechanical and Microstructural Properties of Kaolin and Ceramic Powder-Based Geopolymer Mortar

Recent trends in reducing the ecological footprint of the construction industry have increased the attention surrounding the use of alternative binding systems. Among the most promising are geopolymer binders, which were found to have the capability to substantially reduce the environmental impact of Portland cement use. However, even the use of this alternative binding system is known to be heavily dependent on the use of industrial byproducts, such as precursors and an alkaline source, produced through an energy intensive process. To address this and provide a greener route for this binding system, this study adopts the use of natural kaolin and raw ceramic powder as the main precursors. The activation process is performed by using solid potassium hydroxide in conjunction with sodium and magnesium sulfate, which are naturally available, to produce geopolymers. To assess the resulting geopolymer samples, 28 mixes are produced and a series of physico-mechanical and microstructural analyses is conducted. The results show that the use of ceramic powder can improve the physico-mechanical properties by reducing porosity. This, however, requires a relatively higher alkalinity for activation and strength development. These findings are further confirmed with the XRD and FTIR results. Nonetheless, the use of ceramic powder with sodium and magnesium sulfate is found to result in a more coherent and homogenous microstructure, compared to the geopolymers produced with potassium hydroxide and kaolin. The findings of this study point to the suitability of using sodium and magnesium sulfate for the cleaner production of kaolin and ceramic powder-based geopolymers.

Direct synthesis of HZSM-5 zeolites with enhanced catalytic performance in the methanol-to-propylene reaction

HZSM-5 zeolites were directly synthesized via a two-stage crystallization method using ammonia hydroxide as an alkaline source instead of the conventional sodium hydroxide, and their performance in the methanol-to-propylene (MTP) reaction was investigated at 470 °C. The use of ammonia hydroxide as the alkaline source can overcome the inherent drawback of requiring multiple ion exchanges for converting Na-form zeolites to NH4+-form derivatives. Bulk and surface characterization techniques were combined to study the changes in crystallinity, porosity, morphology, aluminum distribution, and acidity with the experimental conditions. It was found that ammonia hydroxide had limited effect on the crystallinity and morphology of HZSM-5 zeolites, whereas the silicon and aluminum sources affected significantly the morphology and aluminum distribution. The acid properties and aluminum distribution induced important changes in the MTP activity and selectivity. Thus, increasing the framework SiO2/Al2O3 ratios in HZSM-5, in other words, reducing the acid density and the amount of framework aluminum species in the channel intersections, could improve the selectivity to propylene by favoring the olefinic-based cycle reaction. The catalyst lifetime was found to depend on not only the acid density but also on the acid distribution (or framework aluminum distribution).

Organic geochemistry and controlling factors of alkaline source rocks within sequence stratigraphic framework in the Fengcheng Formation, Mahu sag, Junggar Basin, NW China

The Fengcheng Formation (P1 f) source rock, which was deposited in an alkaline water body, is one of the most significant source rocks in the Mahu sag, Junggar Basin. However, its evolution and mechanism of organic matter accumulation are still not understood. Using seismic, core, and log data, P1 f is divided into 3 third-order sequences, i.e., SQ1, SQ2, and SQ3, from bottom to top. Pyrolysis data of core samples shows that SQ1 and SQ3 mainly are characterized by poor to fair source rocks, with Type III to Type II2 kerogen, while SQ2 mainly are characterized by fair to good to excellent source rocks, with Type II2 to Type I kerogen. The biomarker parameters of 40 source rock samples from different sequences suggest that the reducibility of sedimentary water is characterized by SQ2 &gt; SQ1 &gt; SQ3. The organic matter contribution in different sequences is obviously different. SQ1 organic matter contain more bacteria and algae than that of SQ2 and SQ3, and terrigenous higher plants may have contributed to SQ3 organic matter. Lake level changes and water salinity dominate organic matter origin, accumulation, and preservation. During SQ1 deposition, the lake level was the highest, the salinity of sedimentary water was moderate, and the organic matter contained more conventional algae sources. During SQ2 deposition, the lake level was the lowest and the salinity was the highest, and the organic matter contained special algae characterized by C29 regular steroids. The lake level of SQ3 was higher than that of SQ2, the salinity was the lowest, and terrigenous higher plants may have contributed to organic matter during this period.

Environmental-assisted shape-controlled synthesis and electrocatalytic performance of CuS nanostructures for vanillin detection in commercial food products

Vanillin is broadly used as a food additive in various foods and beverages. The rampant intake of vanillin has major side-effect on human health and hence the development of vanillin sensor is highly important in various fields. In this work, simple and eco-friendly approach for the fabrication of shape-controlled copper sulfide (CuS) nanostructures were studied by changing the type of alkaline sources in solvothermal method. Three specific nanostructures i.e. CuS hexagonal (without alkaline source), CuS intersect-hexagonal (sodium hydroxide) and CuS micro-flower (ammonia) shapes were formed and significantly depended on the choice of alkaline source. The XRD, FE-SEM and HR-TEM results revealed that as-formed CuS products had good crystallinity with high phase purity, and uniform surface morphologies. The shape-specific electrochemical detection of vanillin (VN) in neutral pH medium was performed over the prepared CuS nanostructures. It was observed that hexagonal shaped CuS nanostructure having thin and smooth surface showed the best performances with lower oxidation potential (610 mV), and higher oxidation peak current density (2.5 µA) when compared to other CuS nanostructures, suggesting that the CuS-hexagonal shape could be used as an effective sensing platform for the sensitive determination of VN. The fabricated CuS-hexagonal-based sensor showed a good linear detection range between 0.1 and 46.5 µM, low detection limit (53 nM), excellent sensitivity (0.85 µA/µM cm−2), selectivity, outstanding stability and repeatability. The optimized sensor was further applied into the determination of VN with acceptable recovery in real samples (biscuit, chocolate and milk powders).

Novel nanohybrids for effervescence enhanced magnetic solid-phase microextraction of wide-polarity organic pollutants in roasted meat samples.

To simultaneously and efficiently extract pollutants with differential polarities, we herein fabricated and characterized a multifunctional nanocomposite. The novel nanohybrids used NiFe2 O4 as magnetic cores, and NH2 -MIL-101(Al), β-cyclodextrin and graphene oxide as functional components combined with magnetic cores. With the aid of graphene oxide's large π-conjugated system, NH2 -MIL-101(Al)'s strong adsorption to moderately/strongly polar chemicals, and β-cyclodextrin's specific recognition effect, the nanohybrids realized synergistically efficient extraction of polyaromatic hydrocarbons and bisphenols with a logKow range of 3-6. Combined with acidic and alkaline sources, the nanohybrids-based effervescent tablets were prepared. Based on effervescent reaction-enhanced nanohybrids-based efficient adsorption/extraction and high performance liquid chromatography and fluorescence detection, we successfully developed an excellent microextraction method for the simultaneous determination of both polyaromatic hydrocarbons and bisphenols in roasted meat samples. Several important variables were optimized as follows: Na2 CO3 and tartaric acid as acidic and alkaline sources, 900 μLof the mixed solvent (acetone and hexane at 2:1 by v/v) as the eluent, 5min of elution time. Under optimized conditions, the novel method gave low limits of detection (0.07-0.30 μg kg-1 ), satisfactory recoveries (86.9-103.9%), and high precision (relative standard deviations of 1.9-6.7%) in roasted lamb, beef, pork, chicken, and sausage samples.