Optimal Experimental Conditions Research Articles

Metolachlor Detection in Grain Using N‐Doped Carbon Quantum Dots and the Intramolecular Charge Transfer Effect

Herein, nitrogen is doped into carbon quantum dots (N‐CQDs) using a hydrothermal method for the rapid detection of metolachlor in grain. The morphological features, elemental compositions, and optical properties of the N‐CQDs are then analyzed and investigated using transmission electron microscopy, X‐ray photoelectron spectroscopy, and fluorescence spectroscopy, respectively. Based on the principle of intramolecular charge transfer, a fluorescent probe is constructed for the rapid detection of metolachlor. Under optimal experimental conditions, the fluorescence intensity change values of the N‐CQDs and metolachlor concentration have a good linear relationship when the concentration of metolachlor is in the range of 0.0125−2.5 μg mL−1. An evaluation of the method shows that the method has good selectivity, reproducibility, and stability, with a limit of detection of 1.63 μg kg−1 and a limit of quantification of 3.92 μg kg−1. The spiked recoveries of six real samples are tested using a spiked recovery assay that yielded spiked recoveries in the range of 105.05−87.13%, and their relative standard deviations (n = 3) ranged from 4.62% to 0.61%, indicating that the method can be used for detection in actual samples with good precision and stability.

Preparation of active zinc oxide from zinc-containing dust and synergistic recovery process of valuable elements

Zinc-containing dust generated from the iron and steel industry is enriched with a large amount of heavy metal substances and rare elements, which is a hazardous waste and a secondary resource. In this study, a new process for the preparation of active zinc oxide and synergistic recovery of valuable elements using zinc-containing dust was proposed. Firstly, a fire process was used to make the valuable components such as Zn, Cd, K, Na, Pb, Bi, In and Sn secondary enriched in the zinc-rich dust. Then the leaching and recovery of K (99.74 %) and Na (98.12 %) were realized by alkaline washing method taking advantage of the solubility difference. Thermodynamic analysis showed that controlling the pH of the leaching system could realize the selective separation of the valuable components. The experimental results showed that the leaching rates of Zn and Cd reached 86.95 % and 92.28 %, respectively, under the optimal experimental conditions, while Pb, Sn, Bi and In were enriched in the neutral leaching slag. Cd sponge (70.3 %) was obtained after the neutral leach solution was treated by Zn powder replacement process. The purified zinc sulfate solution was used to prepare active zinc oxide (97.04 %) by direct precipitation at a molar ratio of CO32–/Zn2+ of 1.15 and a temperature of 50 °C. The average particle size of the product was 21.95 nm, which was in accordance with the industry standard. Neutral leaching slag realized Bi (91.5 %), Sn (71.01 %) and In (94.0 %) in high acid leaching process, and Pb was enriched in slag in the form of PbSO4. The high acid leach solution is hydrolyzed, extracted and replaced to obtain BiOCl, crude tin and crude indium. This process realizes the comprehensive recovery and high-value utilization of various valuable elements in zinc-containing dust sludge, and has significant environmental, economic and social benefits.

The synergistic enhancement of photocatalytic activity by Fe3O4–TiO2 nanosheets for rhodamine B degradation

As an advanced oxidation material, Fe3O4-TiO2 nanocomposites have been widely used in wastewater treatment. However, conventional Fe3O4 nanoparticles suffer from drawbacks such as carrier recombination and aggregation, which seriously affect the catalytic activity. In this study, Fe3O4-TiO2 nanosheets with different TiO2 loading rates were synthesized by sol-gel method and solvothermal method. The unique two-dimensional nanostructure of Fe3O4 nanosheets facilitated the deposition of TiO2 nanoparticles, resulting in Fe3O4-TiO2 nanosheets with a high BET specific surface area of 121.67 m2·g−1. Under optimal experimental conditions, the degradation rate of RhB dye in the photocatalytic synergistic Fenton-like system constructed with Fe3O4-TiO2 nanosheets reached 98.12 % within 120 min, significantly surpassing that of single photocatalysis and Fenton-like systems. It was attributed to the unique surface structure of Fe3O4 nanosheets, which provided a larger contact area for TiO2 nanoparticles. It facilitated the effective reduction of Fe3+ to Fe2+ by photogenerated electrons in TiO2, inhibited the recombination of photogenerated electron-hole pairs, and consequently enhanced the degradation rate of RhB dye. Furthermore, Fe3O4-TiO2 magnetic nanosheets exhibited excellent reusability and stability, with the recovery rate and degradation rate of RhB dye remaining above 90 % even after five cycles. More importantly, the catalytic mechanism of Fe3O4-TiO2 nanosheets was elucidated, and •OH identified as the primary reactive species responsible for degrading RhB dye. This work provides a novel research direction for designing and preparing advanced catalytic degradation materials, offering a practical solution to the challenging issue of wastewater treatment.

An electrochemical biosensor based on MoS2-PANi@Fc for the detection of Golgi protein 73

Golgi protein 73 (GP73) is highly expressed in hepatocellular carcinoma (HCC) and has been regarded as a sensitive serum biomarker for HCC diagnosis. Herein, an electrochemical biosensor for the determination of GP73 was constructed based on the molybdenum disulfide-polyaniline@ferrocene (MoS2-PANi@Fc) nanocomposites. The MoS2-PANi@Fc was prepared with large surface area and excellent electrical properties. One aptamer for GP73 (GP73Apt1) immobilized on MoS2-PANi@Fc by π-π stacking and metal ligand interactions was used as an electrochemical signal reporter probe by Fc oxidation. Another GP73 aptamer (GP73Apt2) was immobilized on the surface of gold nanoparticles electrodeposition into screen-printed carbon electrode (Au NPs/SPCE) to capture the target GP73. In the presence of GP73, Fc electrochemical signal recorded by differential pulse voltammetry (DPV) increased gradually. The preparation processes, mechanisms and optimal experiment conditions of electrochemical biosensor were studied by electron microscope imaging, spectral curves and electrochemical measurements. Under optimized experimental conditions, the aptasensor was demonstrated to be capable of detecting GP73 with a linear range of 0.001–100.0 ng mL−1 and a limit of detection (LOD) of 0.001 ng mL−1 (σ = 3). Stability, specificity and reproducibility were well demonstrated. These results may provide new insights for clinical detection of HCC.

Optimized electrochemical treatment of semi-coking wastewater for enhanced degradation of biological toxicity using a Ru-Ir-Ti anode and Co-Ti cathode

The Co-Ti cathode was prepared to reduce the biological toxicity of semi-coke wastewater by electrochemical system with commercial ruthenium-iridium titanium (Ru-Ir-Ti) anode. Meanwhile, the removal rate of chemical oxygen demand (COD), volatile phenol (VP) and ammonia nitrogen (NH3-N) in wastewater were also evaluated. Hence, the influence of processing time (A), dilution multiple (B), initial pH (C), electrolyte concentration (D) and current density (D) were systematic explored. After treatment, with the optimized experiment condition of processing time (150 min), dilution multiple (300 times), initial pH (3.2), electrolyte concentration (0.15 mol/L), current density (16 mV/cm2), the B/C value of wastewater was greatly improved from 0.12 to 0.31, the removal rate of COD, NH3-N and VP was 96.82 %, 92.34 % and 97.07 %, respectively. The sequence of significance was B>D>E*E>B*D>A*D>D*D. This most effective degradation was owing to the simultaneously oxidization of both cathode and anode, turning the highly biological toxic wastewater to the biodegradable one. The direct oxidation reaction happened on anode, furthermore, the indirect oxidation reaction would be accelerated near the cathode because of active free radicals generation such as ·OH and O2•– when the cobalt’s valence changed from +2 to +3. It deserve to be mentioned in this research is that the direct and indirect oxidation simultaneously contributed to the degradation of biological toxicity, which is great beneficial for the further bio-chemical processing.

Assisted Active Learning for Model-Based Method Development in Liquid Chromatography.

In recent decades, there has been a growing interest in fully automated methods for tackling complex optimization problems across various fields. Active learning (AL) and its variant, assisted active learning (AAL), incorporating guidance or assistance from external sources into the learning process, play key roles in this automation by enabling the autonomous selection of optimal experimental conditions to efficiently explore the problem space. These approaches are particularly valuable in situations wherein experimentation is costly or time-consuming. This study explores the application of AAL in model-based method development (MD) for liquid chromatography (LC) by using Bayesian statistics to incorporate historical data and analyte information for the generation of initial retention models. The process involves updating the model parameters based on new experiments, coupled with an active data selection method to choose the most informative experiment to run in a subsequent step. This iterative process balances model exploitation and experimental exploration until a satisfactory separation is achieved. The effectiveness of this approach is demonstrated via two practical examples, resulting in optimized separations in a limited number of experiments by optimizing the gradient slope. It is shown that the ability of AAL to leverage past knowledge and compound information to improve accuracy and reduce experimental runs offers a flexible alternative approach to fixed design methods.

Optimization of Extraction Process of Total Alkaloids from Thalictrum delavayi Franch. and Their Therapeutic Potential on Pulmonary Infection Caused by Klebsiella pneumoniae and Escherichia coli

Bacterial co-infected pneumonia is an acute inflammatory reaction of the lungs mainly caused by Gram-negative bacteria. Antibiotics are urgently important but have the disadvantage of antibacterial resistance, and alternative treatments with medicinal plants are attractive. On the Qinghai–Tibet Plateau, Thalictrum delavayi Franch. (T. delavayi) is an important member of the buttercup family (Ranunculaceae), is rich in alkaloids and has been used in folk medicine for thousands of years. In this study, the extraction process of total alkaloids from the whole T. delavayi plant was optimized and the extract’s therapeutic potential against pulmonary infection caused by Klebsiella pneumoniae and Escherichia coli was investigated. The results showed that the optimum experimental conditions for the total alkaloids (2.46%) from T. delavayi were as follows: hydrochloric acid volume fraction of 0.8%, solid–liquid ratio of 1:12 and sonication time of 54 min. The treatment reduced bacterial counts, white blood cell counts and inflammatory cell classification in bronchoalveolar lavage fluid (BALF) and the levels of inflammatory cytokines interleukin-4 (IL-4), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), procalcitonin (PCT) and C-reactive protein (CRP), procalcitonin (PCT) and C-reactive protein (CRP) in the serum in experimental groups. The results in our experimental preliminary work suggested that the total alkaloids from T. delavayi had therapeutic effects on mice with Klebsiella pneumoniae and Escherichia coli mixed infectious pneumonia, providing experimental support for the plant’s therapeutic potential in treating pulmonary infections caused by Klebsiella pneumoniae and Escherichia coli.

Recovery of boron and zinc from wastewater via electrodialytic metathesis

With the development of industrial civilization, large amounts of wastewater containing boron and zinc are being produced. Such wastewater poses a great threat to human health if discharged without treatment. In this study, an integrated technology of electrodialytic metathesis (EDM) and a hydrothermal process was utilized to recover boron and zinc from wastewater in the form of zinc borate (Zn2B6O11·3H2O). Experimental results showed that electrolyte concentration, current density, and initial boron and zinc concentration clearly affected the recovery ratios for B4O72− and Zn2+ and their corresponding specific energy consumption and current efficiencies. Under the optimal experimental conditions (an electrolyte concentration of 1.0 mol/L in the recycling compartment in the experimental setup, a current density of 15 mA/cm2, initial ZnSO4 and Na2B4O7 concentrations of 0.1 mol/L, and a flow rate of 20 mL/min), the recovery ratio, specific energy consumption, and current efficiency were 85.6 %, 6.5 kW·h/mol, and 12.3 %, respectively, for recovering B4O72− and 80.6 %, 1.7 kW·h/mol, and 45.7 %, respectively, for recovering Zn2+. When one recovery compartment was employed, the current efficiencies for recovering B4O72− and Zn2+ were 12.3 % and 45.7 %, respectively, and these values were 11.4 % and 43.8 %, respectively, when two recovery compartment were used. After B4O72− and Zn2+ concentrated by EDM were treated via a hydrothermal process, a white precipitate was produced. The results of X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analyses showed that this precipitate exhibited physicochemical properties similar to those of commercial Zn2B6O11·3H2O. Thus, the integrated technology can be regarded as an effective method for recovering boron and zinc from wastewater.

Investigation of europium(III) uptake from highly sulphate solution via cloud point extraction by mono-Schiff base combined with Triton X-100

ABSTRACT Owing to its unique physico-chemical properties, europium is one of the most precious and sought-after rare earth elements in the field of high technology. The major economic and commercial importance of such an element, combined with the pollution risks associated with its intensive use, require the development of efficient and eco-compatible recovery and recycling processes. This study focuses on the recovery of europium from highly saline sulphate media (0.5 mol/L) using an environmentally friendly two-phase aqueous extraction technique (known as cloud point extraction (CPE)), using 2((phenylimino)methyl)phenol mono-Schiff base (HPIMP) as the extractant and Triton X-100 as the non-ionic surfactant. The influence of key experimental parameters such as pH, extractant concentration, surfactant concentration and separation temperature on the europium extraction process was systematically studied and optimized. Under optimum experimental conditions, a quasi-quantitative extraction with a minimal volume fraction of surfactant-rich phase (φs = 0.025), and concentration factor of (CF = 38) was achieved at pH 9.8, in one stage. The analysis of the extraction data revealed that the CPE of europium(III) takes place by a cation exchange-solvation mechanism. The stoichiometry of the complex extracted into the surfactant-rich phase was ascertained to have a composition of 1:2 [Eu:HPIMP] with the slope analysis method. A higher extraction constant was obtained for CPE compared with conventional solvent extraction, confirming the feasibility and usefulness of CPE for Eu(III) recovery. On the other hand, this new HPIMP/Triton X-100 chelating system showed superior extractability for Eu(III) in the CPE process relative to other systems reported previously.

Assembly of ligation chain reaction and DNA triangular prism for miRNA diagnostics

Controllable assembly of DNA nanostructure provides a powerful way for quantitative analysis of various targets including nucleic acid molecules. In this study, we have designed detachable DNA nanostructures at electrochemical sensing interface and constructed a ligation chain reaction (LCR) strategy for amplified detection of miRNA. A three-dimensional DNA triangular prism nanostructure is fabricated to provide suitable molecule recognition environment, which can be further regenerated for additional tests via convenient pH adjustment. Target triggered LCR is highly efficient and specific towards target miRNA. Under optimal experimental conditions, this approach enables ultrasensitive exploration in a wide linear range with a single-base resolution. Moreover, it shows excellent performances for the analysis of cell samples and clinical serum samples.

Applying bimetallic gold/silver nanoclusters and gold nanoparticles for dairy trypsin and inhibitor analysis via inner-filter approach

Trypsin, a globular protein hydrolase, catalyzes the hydrolysis of peptide bonds at carboxyl groups of arginine and lysine residues, its detection holds paramount significance in the dairy industry, aiding in the diagnosis, management of animal diseases, and preservation of dairy products. This study introduces a highly sensitive fluorometric detection platform utilizing bimetallic gold/silver nanoclusters (Au/Ag NCs) and gold nanoparticles (AuNPs) in an "off-on-off" configuration for precise quantification of dairy trypsin and trypsin inhibitors. This fluorescence variation is leveraged to determine the concentration of trypsin and its inhibitors. Under optimal experimental conditions, the detection of trypsin demonstrates a linear range of 5 ∼ 2000 ng·mL−1 , a lowest detection limit of 1.18 ng·mL−1, and an observed IC50 of 5.94 μg·mL−1 for the soybean trypsin inhibitor (STI). Therefore, it could be inferred that the development of a fluorescence sensing platform presents an important basis for the detection of dairy trypsin.

Functionalized sea urchin-like MnO2 with chitosan to load CaCo layered double hydroxides for advanced catalytic oxidation of antibiotics through activation of peroxymonosulfate

Novel composite catalysts based on the functionalization of sea urchin-like MnO2 with chitosan (CS) to load CaCo layered double hydroxides were prepared by a simple hydrothermal method, and the physicochemical properties of the resulting MnO2@CS-CaCo LDHs were analyzed by various characterization methods. Then advanced oxidation processes (AOPs) were constructed based on MnO2@CS-CaCo LDHs through activation of peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP), norfloxacin (NOR) and sulfamethoxazole (SMX) in water. Sea urchin-like MnO2 modified by CS created a unique interface and a variety of active functional groups for the loading of CaCo LDHs where MnO2 particles were uniformly attached to the surface of CaCo LDHs. The results showed that the MnO2@CS-CaCo LDHs composites had excellent catalytic performances compared with monomeric MnO2, MnO2@CS and CaCo LDHs, and the enhanced catalytic performances were mainly due to the synergistic effects between LDHs, CS and MnO2. Under optimal experimental conditions, the removal efficiencies of CIP and NOR reached up to 96.45 % and 96.58 % within 20 min, respectively, and the removal of SMX was 93.12 % within 30 min. Quenching experiments demonstrated that 1O2 was the main active oxygen species for catalytic degradation through a non-radical pathway. In addition, the degradation efficiency of NOR was still as high as 93.78 % after the 10th cycle of degradation experiments, indicating that the composite catalysts had excellent reproducibility and stability. Finally, the activation mechanisms of MnO2@CS-CaCo LDHs/PMS and degradation pathways of SMX were proposed. The catalytic performances of MnO2@CS-CaCo LDHs/PMS for removal of three drugs in actual water bodies were further evaluated their practical application ability.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Preparation of CoFe@C composite modified electrode for neohesperidin dihydrochalcone sensing and its application in Chinese medicine.

CoFe@C was first prepared by calcining the precursor of CoFe-metal-organic framework-74 (CoFe-MOF-74), then an electrochemical sensor for the determination of neohesperidin dihydrochalcone (NHDC) was constructed, which was stemmed from the novel CoFe@C/Nafion composite film modified glassy carbon electrode (GCE). The CoFe@C/Nafion composite was verified by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) was used to evaluate its electrical properties as a modified material for anelectrochemical sensor. Compared with CoFe-MOF-74 precursor modified electrode, CoFe@C/Nafion electrode exhibited a great synergic catalytic effect and extremely increased the oxidation peak signal of NHDC. The effects of various experimental conditions on the oxidation of NHDC were investigated and the calibration plot was tested. The results bespoken that CoFe@C/Nafion GCE has good reproducibility and anti-interference under the optimal experimental conditions. In addition, the differential pulse current response of NHDC was linear with its concentration within the range0.08 ~ 20µmol/L, and the linear regressioncoefficient was 0.9957. The detection limit was as low as 14.2nmol/L (S/N = 3). In order to further verify the feasibility of the method, it was successfully used to determine the content of NHDC in Chinese medicine, with a satisfactory result, good in accordance with that of high performance liquid chromatography (HPLC).

A signal-on electrochemiluminescence (ECL) sensor based on luminol@carbon nanotubes and CdTe-ZnS@hydroxyapatite for the detection of paclitaxel

A signal-on solid-state electrochemiluminescence (ECL) sensor based on luminol@carbon nanotubes (luminol@CNTs) and CdTe-ZnS@hydroxyapatite (CdTe-ZnS@HAP) was constructed for the detection of paclitaxel (PTX). In this sensing platform, luminol was used as the main luminophore and CdTe-ZnS was used as a co-reaction accelerator. CNTs and HAP were acted as carriers to adsorb more luminophores and co-reaction promoters. In addition, due to the enhanced effect of PTX on the ECL intensity of the luminol-O2 system, PTX was introduced as the final detection target. Under the optimal experimental conditions, the ECL intensity change values (ΔI) of the sensor showed a good linear relationship with the logarithm of PTX concentration in the range of 3 × 10-12 − 3 × 10-7 molL-1, and the limit of detection was 1 × 10-12 mol L-1(S/N = 3). This method was successfully applied to the determination of trace PTX concentration in serum.

A Novel Electrochemical Sensing Based on Cerium Oxide/Nitrogen-Doped Reduced Graphene Oxide for Sensitive Detection of Acetaminophen

Acetaminophen (ACP), a common analgesic and antipyretic medication, can harm the liver when overdosed and its metabolites can contaminate the environment, so it is necessary to monitor the concentration precisely and reliably. In this work, we successfully synthesized cerium oxide/nitrogen-doped reduced graphene oxide (CeO2/N-rGO) composite nanomaterials using a one-step hydrothermal method. Using composite nanomaterials, we created an electrochemical sensing detection platform for ACP detection. The synthesized materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The constructed electrochemical sensor exhibits good ACP detection ability under the synergistic effect of CeO2 and N-rGO. Under optimal experimental conditions, the sensor displayed a linear range for the detection of ACP of 1 ∼ 200 μM and the lowest detection limit of 0.79 μM, exhibiting outstanding selectivity, stability, and repeatability. Furthermore, the sensor was effectively applied to detect ACP in tap water samples, which offers a wide range of possible applications in actual sample testing.

Simulation and experimental study of InN nanoparticles synthesized by ion implantation technology.

In order to synthesize InN nanoparticles (NPs), we have simulated the co-implantation of indium (In) and nitrogen (N) ions on silicon (Si) and silicon oxide (SiO2) substrates with flat-top profiles. The choice of flat-top profile is to increase the possibility of creating homogeneous zone with well-distributed InN nanoparticles over the entire implanted layer. In this view and to obtain these flat-top profiles, we must do several implantations with different doses and energies optimized by our program. The simulation results performed on a silicon substrate < 111 > , give an average dose of 4.30 × 1016 at./cm2 and the implantation energies were In (10, 46, and 180 keV) and N (13 and 35 keV). But for the SiO2 substrate, the total mean dose is about 5.20 × 1016at./cm2 for each Indium and nitrogen ion. The respective implantation energies were In (23, 63, and 120 keV) and N (12 and 28 keV) in an average depth of approximately 100 nm. The implantations were performed in a 206-nm-thick (SiO2) layer thermally grown on < 100 > silicon. Subsequent thermal treatments (500-900°C) lead to the formation of nanoparticles precipitates of the compound semiconductor (InN) and to cure the oxide defects during different periods of time. To verify that indium (In) and nitrogen (N) ions were located according to flat curves, we used RBS technical and study the formation (InN) stoichiometric compound several techniques, were used such as X-ray diffraction, UV-visible-IR, and photoluminescence (PL) spectroscopy. The simulated profiles have been chosen with the aim that the implanted element not exceeding 5-10 at %maximum concentration for each species. We have elaborated our program to simulate these profiles using data as input values from SRIM2008 code taking into account the sputtering factor. The optimal conditions are determined, which are the expected depth impact energies (Rp), the standard deviation (ΔRp) and the sputtering corrosion factor (Fs). Through these results, a simulation program has been created which allows building flat "distribution" curves for ion implantation for each element (In and N), so that each curve is obtained from three Gaussian functions whose values are carefully chosen in relation to the optimal experimental conditions.

Chemometrically-aided general approach to novel adsorbents studies: Case study on the adsorption of pharmaceuticals by the carbonized Ailanthus altissima leaves

A chemometrically based approach was applied to select the most efficient drug adsorbent among the biochars obtained from the novel feedstock, the leaves of the invasive plant (Ailanthus altissima). The representative target adsorbates (atenolol, paracetamol, ketorolac and tetracycline) were selected on the basis of their physicochemical properties to cover a wide chemical space, which is the usual analytical challenge. Their adsorption was investigated using design of experiments as a comprehensive approach to optimise the performance of the adsorption system, rationalise the procedure and overcome common drawbacks. Among the response surface designs, the central composite design was selected as it allows the identification of important experimental factors (solid-to-liquid ratio, pH, ionic strength) and their interactions, and allows the selection of optimal experimental conditions to maximise adsorption performance. The biochars were prepared by pyrolysis at 500 °C and 800 °C (BC-500 and BC-800) and the ZnCl2-activated biochars were prepared at 650 °C and 800 °C (AcBC-650 and AcBC-800). The FTIR spectra revealed that increasing the pyrolysis temperature without activator decreases the intensity of all bands, while activation preserves functional groups, as evidenced by the spectra of AcBC-650 and AcBC-800. High temperatures during activation promoted the development of an efficient surface area, with the maximum observed for AcBC-800 reaching 347 m2 g−1. AcBC-800 was found to be the most efficient adsorbent with removal efficiencies of 34.1, 51.3, 55.9 and 38.2 % for atenolol, paracetamol, ketorolac and tetracycline, respectively. The models describing the relationship between the removal efficiency of AcBC-800 and the experimental factors studied, showed satisfactory predictive ability (predicted R2 > 0.8) and no significant lack-of-fit was observed. The results obtained, including the mathematical models, the properties of the adsorbates and the adsorbents, clearly indicate that the adsorption mechanisms of activated biochars are mainly based on hydrophobic interactions, pore filling and hydrogen bonding.

Continuous alkylation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene in microreactor: Process intensification and reaction kinetics

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an essential insensitive energetic material. The alkylation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene (Trinitrophloroglucinol, TNPG), which yields 1,3,5-triethoxy-2,4,6-trinitrobenzene (TETNB), is a pivotal step for the synthesis of TATB. The conventional synthetic process has suffered from long reaction time (∼165 min), intricate procedures, and intensive evaporation of a large number of volatile by-products, which increases the risk of spill and eruption of the reaction system, and necessitates in situ continuous gas–liquid separation. A new process for continuous alkylation in microreactors was proposed in this study. Firstly, a parametric investigation in the batch reactor was performed to explore the effects of various process parameters on the yields, resulting in the optimal experimental conditions, i.e., no reflux condensation, triethyl orthoformate (TEOF) as alkylation reagent, molar ratio of 12, reaction temperature of 120 °C and reaction time of 40 min. Subsequent continuous synthesis in microreactors was conducted, which realized the convenient process operation and no need of gas–liquid separation, leading to substantial improvement in the reaction efficiency and safety. Remarkably, within a packed microreactor, under the reaction temperature of 130 °C and residence time of 3 min, 99.24 % in the yield of TETNB was achieved. Comparing with conventional batch reactors, the required reaction time was reduced to approximately 1/50. Taking the advantages of precise control of temperature and reaction time in the microreactors, the kinetics of alkylation reaction were determined. This innovative approach of continuous synthesis can provide an efficient and alternative route for the synthesis of TATB, as well as other energetic materials and similar processes.

Mesoporous pineapple crown-derived activated carbon modified matrix for the detection of carbendazim in the presence of anionic surfactant

Carbon paste electrodes (CPEs) are commonly employed in electroanalysis because of their chemical stability, broad electrochemical window, low capacitive current, ease of fabrication, and surface renewability. Electrocatalysts can easily be embedded into CPEs to make them suitable for a variety of applications. Poor biowaste management presents a significant challenge in the agro-industry and agriculture due to the rapid decomposition of biowaste, driven by its high water content and limited biological stability, which leads to pest attraction and greenhouse gas emissions. Consequently, this green waste can be utilized for the development of electrocatalysts. Activated carbon (AC) has been utilized in progressive electrochemical applications as it exhibits high conductivity and porosity that help to enhance electrocatalytic activity. Herein, pineapple fruit crown (PC) peel-derived AC (PCAC) is utilized as the sensing material for the determination of fungicide, carbendazim (CBM). The synthesized material was characterized using SEM, FT-IR, XRD, EDX, AFM, CV and EIS. Besides, to enhance the surface properties, Sodium dodecyl sulfate (SDS) surfactant is used as a mediator in detecting CBM. The CV and SWV approaches were employed to assess the electrochemical response of the developed electrodes for the CBM determination. Under optimum experimental conditions, the SDS/PCAC/CPE exhibits low DLim and QLim values of 32.0 nM and 128.0 nM with considerable selectivity. Furthermore, the SDS/PCAC/CPE was employed in real-time analysis of CBM in spiked environmental samples, which showed satisfying recovery results. Moreover, the electrode showed good stability over multiple measurements, and these results demonstrate that SDS/PCAC/CPE is a promising sensor for CBM detection.