NaBH4 Concentration Research Articles

A stable flow hydrogen production of sodium borohydride hydrolysis using millimeter-scale Ru/Al2O3 spheres as catalyst

In this study, we investigated the performance of continuous flow hydrogen production from NaBH4 hydrolysis by loading Ru onto millimeter-scale Al2O3 spheres (0.5–1 mm in diameter) (Ru/m-Al2O3) using a simple impregnation method. The results from transmission electron microscopy (TEM) and N2 adsorption and desorption revealed that Ru particles, with an average size of 2.73 nm, were evenly distributed on the Al2O3 spheres, and the catalysts exhibited a typical mesoporous structure. The study investigated the impact of Ru loading, catalyst quantity, catalyst reduction temperature, hydrogen production temperature, feeding rate, and concentrations of NaBH4 and NaOH on the rate of hydrogen production (HPR). The evaluation of hydrogen production revealed that the top-performing Ru/m-Al2O3 catalyst achieved a HPR of 22.44 L min–1 gRu–1 at 30 °C, with an apparent activation energy (Ea) of 33.98 kJ mol–1. The catalyst could continuously produce hydrogen for 1700 min with a 20 % decrease in activity. The characterization results before and after hydrogen production revealed that Ru/m-Al2O3 exhibited excellent structural stability after a prolonged period of hydrogen production, with no apparent changes in its morphology, crystal structure, Ru particle size, and pore structure. In addition, the X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and hydrogen production performance results showed that the flow system could effectively prevent the aggregation of NaBO2 on the catalyst's surface, thereby significantly improving the hydrogen production activity.

Fabrication and characterization of Halloysite–Fe3O4–Ag nanocomposite as efficient catalyst for metronidazole degradation by using sodium borohydride: Artificial neural network modeling

In this work, halloysite–Fe3O4–Ag nanocomposite produced by doping Fe3O4 and Ag nanoparticles on the surface of halloysite nanotube after activation with HCl by co-precipitation method was used as a catalyst for the catalytic degradation of metronidazole antibiotic with sodium borohydride. The physical and chemical structure of synthesized nanocomposite were characterized by pHpzc, FTIR, XRD, SEM/EDX and TGA. The degradation process of metronidazole antibiotic with sodium borohydride in the presence of nanocomposite catalyst was investigated. According to this, metronidazole removal efficiency was determined as %93.1 (as 0.069 in terms of Ct/C0) at the end of 120-min contact time under determined optimum conditions (pH 7, 10 mM NaBH4 concentration, 2 g/L catalyst dosage, 25 °C temperature) for 30 ppm metronidazole solution. In the pH range in which the process is applied, metronidazole is in anionic form in solution. The used nanocomposite was efficiently recycled and it was determined that it could be reused at least 6 times as a catalyst. Moreover, the process was modeled with Artificial Neural Networks approach. Finally, it was revealed with HPLC analysis that metronidazole was converted into different products as a result of applied process.

Metal Organic Framework Derived Cu-Carbon Composite for the Effective Reduction of p-Nitrophenol

A Cu-carbon composite (Cu-C) was prepared via single-step carbonization of a metal-organic framework (MOF) composed of Cu2+ and 1,4-benzene dicarboxylate (BDC) and applied as a catalyst to degrade p-nitrophenol. The composite was characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM)/energy-dispersive X-ray (EDS), Fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies. The characterization affirmed the preservation of MOF-originated CuO and metallic Cu in the carbon network. In presence of NaBH4, the Cu-C composite resulted in a complete reduction of p-nitrophenol within a few min and exhibited much higher removal rate than commercial CuO. The role of NaBH4 concentration in p-nitrophenol reduction was highlighted in the context of relevant catalytic mechanisms. The composite displayed good reusability during four consecutive cycles of p-nitrophenol reduction with only a small loss of its reactivity, signifying its potential as an alternative to noble-metal catalysts.

Pengaruh Variasi Konsentrasi Nabh4 dan Suhu Operasi Terhadap Nilai Derajat Deasetilasi Kitosan Dari Limbah Cangkang Rajungan

Researchers aim to make chitosan with variations in operating temperature and the addition of NaBH4 at the deacetylation stage. Chitosan is produced through three stages namely demineralization, deproteination and deacetylation. The deproteination process with 3.5% NaOH ratio 1:10 (w/v) was reacted at 80°C for 2 hours, then continued with the demineralization process with HCl 1 N, 1:10 (w/v) ratio reacted at 38°C for 1 hour. For the final stage of making chitosan, a deacetylation process with 60% NaOH is carried out, a ratio of 1:20 (b / v) with the addition of NaBH4 (0.5 and 1) g and variations in operating temperature (100,110,120) °C at the deacetylation stage for 2 hours. In calculating the value of the degree of deacetylation, researchers use the ratio of absorption band A1655 / A3450 to calculate the value of the degree of deacetylation and the baseline method to assist in the calculation, from this calculation, the value of the degree of deacetylation of chitosan is obtained as much. (46.8%, 49.4%, 56.6%, 62.1%, 72.1%, and 74.8%). The best treatment in this study is the deacetylation process temperature of 120 ° C and the addition of NaBH4 concentration as much as 1 g with a deacetylation degree value of 74.8%.

A comparative and comprehensive study on robust silver-immobilized chitosan/carboxy methyl chitosan macromolecules for elimination of dyes

This study explores the potential of modified chitosan (CH) resulting from carboxy methyl (CM) group substitution in the chitosan skeleton, producing carboxy methyl chitosan (CMCH). Silver (Ag) was loaded to chitosan and modified chitosan (carboxy methyl substituted chitosan) supported on cellulose filter paper (FP) to tailor organic–inorganic macromolecule composites “Ag-Chi/CFP and Ag-CMCH/CFP” further applied as substantial composite for the reductive removal of methyl orange (MO) and rhodamine B (RB) dyes from wastewater. The synthesized catalyst was characterized via FTIR, 1H NMR, XRD, and SEM analysis. The degree of substitution was also measured, which was approximately 0.85. The reductive elimination efficiency of Ag-CMCH/CFP and Ag-Chi/CFP for MO dye was 95.31% and 88.85 %. In comparison, the elimination of RB was 98.28 and 94.04 %, respectively, in 16 min time, 0.6 mM Ag concentration, 40 mg/L, dye concentration and 0.3 M NaBH4 concentration. The synthesized catalysts were recycled three times. The degradation of MO and RB dyes using Ag-CMCH/CFP and Ag-Chi/CFP catalysts can be described by the first-order kinetic model. The determination coefficients (R2) and rate constants (k) values for MO degradation were found to be 0.9934 and 0.1736 s−1 for Ag-CMCH/CFP, and 0.9242 and 0.1001 s−1 for Ag-Chi/CFP, respectively. Similarly, for RB degradation, the R2 values were 0.9866 for Ag-CMCH/CFP and 0.9803 for Ag-Chi/CFP, with corresponding k values of 0.219 s−1 and 0.1548 s−1, respectively. The degradation process was optimized using response surface methodology (RSM) to determine the optimal conditions for maximum dye removal efficiency. The RSM models were statistically significant, as validated by ANOVA and correlation coefficient values. The F values of MO and RB models are significant as they have 2450.15 and 21999.37, respectively. The P value for both was <0.0001.

Natural lignin as efficient catalyst for H2 production from NaBH4 methanolysis at low temperature

Herein, natural lignin is used for the first time as a catalyst for the methanolysis of NaBH4. Lignin exhibits excellent catalytic activity for the methanolysis of NaBH4, and the HGR value is as high as 20425 mL H2·gcat−1·min−1 at room-temperature. It is still satisfactory even at − 20 ℃, with a HGR of 2182 mL H2·gcat−1·min−1, which is the highest value reported in the literature to date. In addition, the study of kinetic reaction orders for NaBH4 methanolysis catalyzed by lignin indicates that the catalytic methanolysis of NaBH4 obeys first-order kinetics with respect to both of NaBH4 concentration and catalyst dosage. The activation energy for the methanolysis catalysis by lignin is calculated to be 19.5 kJ·mol−1 at low temperature of − 20 ∼ 25 ℃. The lignin retain over 66% of the original catalytic activity at the end of fifth consecutive reuse, and the catalytic activity can be completely recovered through simple acid treatment.

Synthesis and characterization of MIL-101 (Fe) as efficient catalyst for tetracycline degradation by using NaBH4: Artificial neural network modeling

In this work, Fe-based metal organic framework (MIL-101 (Fe) MOF) was synthesized to use it as a catalyst for the catalytic degradation of tetracycline antibiotic with NaBH4. The synthesized MOF were characterized by Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy/Electron Dispersive X-ray and point of zero charge pH analysis. The effects of parameters such as contact time, pH, NaBH4 concentration and the amount of catalyst on the removal process were investigated and optimum parameters were determined. According to this, tetracycline removal efficiency was determined as 0.180 in terms of Ct/C0 at the end of 60-min contact time under determined optimum conditions for 60 ppm tetracycline solution. Moreover, the process was modeled with Artificial Neural Networks approach by using empirical results obtained from where process parameters were investigated. Finally, it was revealed with HPLC analysis that tetracycline was converted into different products as a result of applied process.

Chitosan-grafted hydrogels for heavy metal ion adsorption and catalytic reduction of nitroaromatic pollutants and dyes

Chitosan-grafted-poly(acrylic acid) (CS-g-PAA) and chitosan-grafted- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (CS-g-P(AA-co-AMPS)) hydrogels were synthesized and then employed as adsorbents for the effective removal of Cu2+ and other heavy metal ions. The effect of hydrogel's composition on the Cu2+ adsorption was explored. The CS-g-PAA hydrogel demonstrated a superior adsorption capacity compared to pristine CS, PAA hydrogel, and CS-g-P(AA-co-AMPS) hydrogels. The adsorption followed the Langmuir isotherm model, and the pseudo-second order kinetic model. Additionally, the CS-g-PAA hydrogel exhibited relatively high adsorption performances toward Cr3+, Co2+, Ni2+, Pb2+, and Zn2+. Metal ions adsorbed within CS-g-PAA hydrogels underwent reduction to their corresponding metallic states and were reutilized as catalysts for the reduction of 4-nitrophenol. The comparative catalytic performances of the metal species in the hydrogel were in the order of Cu > Ni > Co > Zn. The reduction efficiency of Cu-CS-g-PAA increased with increased catalyst dosage, NaBH4 concentration, and temperature. A very low activation energy of 3.7 kJ/mol was observed. The catalyst maintained high catalytic performance even when subjected to real water samples and proved its reusability for up to three cycles. Moreover, the catalyst could effectively reduce 2-nitrophenol and methyl orange.

Preparation of activated carbon-metal nanoparticle composite materials for the catalytic reduction of organic pollutants

This work focuses on the preparation of inexpensive composite materials based on activated carbon-containing metallic nanoparticles MNPs (M = Cu, Ag, Fe). The metal nanoparticles supported on the activated carbon were prepared by ultrasound followed by chemical treatment using a reducing agent NaBH4. The obtained materials were characterized by XRD, XRF, FTIR, XPS, TGA, SEM, and TEM analysis. The different samples were tested as catalysts for the catalytic reduction of organic pollutants (MB, MO, 4-NP) in a simple and binary system in the presence of NaBH4. The results confirmed that the content of metal nanoparticles was in the following sequence 2.12%, 11.15%, and 12.13% for the materials AC-Ag, AC-Cu, and AC-Fe, respectively. According to TEM analysis, the size and dispersion of nanoparticles differ from one catalyst to another, hence the AC-Cu material exhibited good dispersion of CuNPs having ultrafine particles in the range of 4–14 nm. In order to optimize the best conditions for the reduction reaction, the effect of the nature of the catalyst, the initial concentration of NaBH4, the concentration of the pollutant, the mass of the catalyst and the nature of the pollutant were studied, and discussed. In terms of efficiency, the AC-Cu sample was the most efficient catalyst compared to AC-Fe, and AC-Ag, mainly due to the good dispersion of CuNPs on the surface of activated carbon. The recorded rate constant for the MB, MO, and 4-NP in the single system using the same operating conditions was 0.0259 s−1, 0.0218 s−1, and 0.0074 s−1, respectively. In the binary system containing MB + MO or MB + 4-NP, the AC-Cu catalyst was more selective towards the MB dye in both systems. The reuse of the AC-Cu catalyst towards the reduction of the MB dye showed good performance during five consecutive cycles without losing its efficiency.

Inorganic nanoparticles fabricated alginate based nanocomposites for the treatment of brilliant blue dye

The present research work addresses the importance and preparation of polyurethane-sodium alginate (PU-NaAL) composite and silver nanoparticles fabricated PU-NaAL (Ag@PU-NaAL) nanocomposites. Polyurethane was fabricated with sodium alginate to enhance its mechanical properties as well as maintained biocompatibility of the polymer. These polymers based composites were used as micro-reactors for the loading of AgNPs. SPR band appeared at 410 nm in UV–visible (UV-visible) spectra confirmed the successful fabrication of NPs. Fourier transform infrared spectroscopy (FTIR) illustrated the involvement of carbonyl group in the stabilization of mNPs. Thermo-gravimetric analysis (TGA) gives the interpretation of thermal behavior of nanocomposite polymer. It explained that AgNPs were remained stabilized even at high temperature (600 °C) at which major part of polymer campsite was degraded. This analysis also showed that 9.378% AgNPs contents were loaded in polymer chains to prepare nanocomposite. Catalytic activity of Ag@PU-NaAL nanocomposite polymers was investigated by reducing brilliant blue (BB) dye while using NaBH4 as reductant. Dye was degraded catalytically in just 17 min while using NaBH4 as reducing agent. It was also concluded that rate of reduction of BB was also changed by changing the amount of BB dye, NaBH4 concentration and catalyst dose in the reaction mixture. Reported catalyst was also found efficient for the treatment of mixture of toxic dyes and dyes polluted textile industry wastewater.

Metallic and metal oxide nanoparticles synthesized from melon juice. Synthesis, biological application, antioxidant, anticancer, and green catalyst in p-nitrophenol reduction

In this research, melon extract was used as a natural fuel for the synthesis of various nanoparticles. The average particle size was 60–140 nm for Ag, 30–50 nm for La2CO5, and 27–34 nm for ZnO NPs. The three synthesized nanoparticles presented an excellent performance for the reduction of p-nitrophenol to p-aminophenol (k = 0.029, 0.078, and 0.008 min−1 for Ag, La2CO5, and ZnO NPs, respectively). La2CO5 NPs were the most efficient catalyst for p-nitrophenol reduction. The optimal conditions for this catalyst were a catalyst concentration of 0.6 g/L, a NaBH4 concentration of 0.07 mM, and a reaction time of 20 min. The NPs showed a hopeful antioxidant capacity in scavenging DPPH radicals. In vitro anticancer assay confirmed their potent anticancer action. They interacted with human serum albumin (HSA) and quenched its fluorescence emission by static mechanism. During the interaction, the main forces between them and the protein were van der Waals interactions and hydrogen bonds. The structural changes of the HSA were not too great and the protein maintained its overall structure. The results presented in this research confirm that biosynthesized NPs can be promising candidates in catalytic, antioxidant, and anticancer applications.

Reduced porous 2D Co3O4 enhanced peroxymonosulfate activation to form multi-reactive oxygen species: The key role of oxygen vacancies

The introduction of oxygen vacancies (Ov) into Co-based metal oxides has been considered a promising strategy for activating peroxymonosulfate (PMS) to effectively degrade refractory organic contaminants. However, the types of reactive oxygen species (ROS) generated in Ov-catalyst/PMS systems exhibited variability. Therefore, the effect of the interaction between Ov and PMS on ROS generation required further research. Herein, the Ov-tuned 2D porous Co3O4 catalysts were easily constructed by simply controlling the NaBH4 concentration. The as-prepared 2D Co3O4-1.6 had the highest Ov content (2.88 × 1014 spins/g, δ = 0.726), and its catalytic activity for benzotriazole (BTA) degradation (k = 0.032 min−1) was three times higher than that of pristine 2D Co3O4 (k = 0.011 min−1). A series of characterizations and DFT calculations demonstrated that the major active site was Co(II), with Ov serving as an localized electron-rich co-site. These dual sites synergistically improved the adsorption capacity for PMS, enabling rapidly electrons transfer to PMS while promoting the dissociation of O-O bond in PMS to form multiple ROS. Compared to the pristine 2D Co3O4/PMS system, which was dominated only by SO4−, the key ROS in the 2D Co3O4-1.6/PMS system were found to be 1O2 (3.56 µM) and SO4− (2.53 µM), while both O2– (0.72 µM) and OH (0.65 µM) were involved in the activation reaction, the contributions of these four ROS were as follows: 1O2 (36.8%) > SO4− (25.4%) >O2– (9.5%) >OH (6.3%). Finally, three possible degradation pathways of BTA were proposed, and the toxicity of BTA degradation decreased with time, which was consistent with the toxicity prediction results of eleven intermediates. This study provides new insights into the key role of Ov in the heterogeneous catalytic system of PMS-based advanced oxidation processes.

Ultrasensitive determination of selenium in water and food samples by ICP-MS: UiO-66-NH2 for preconcentration and direct slurry hydride generation

BackgroundSelenium is an indispensable microelement for humans and food is the main source of selenium intake. As one of the best techniques for the determination of selenium, inductive coupling plasma-mass spectrometry (ICP-MS) features some unique advantages, such as wide linear range and high sensitivity. Nevertheless, it still remains a challenge to achieve the accurate and high sensitivity determination of ultra-trace selenium in food samples by ICP-MS owning to the high first ionization energy of selenium and interferences from sample matrices as well as isobaric interferences. ResultsIn this work, UiO-66-NH2 (metal organic framework, MOF) was fast synthesized by microwave method and employed for the preconcentration of ultra-trace selenium with an adsorption efficiency of nearly 100%. The selenium-adsorbed MOF was collected by filtration, and then simply converted to slurry for in situ hydride generation (HG) for sensitive detection of selenium by ICP-MS. Various factors affecting the adsorption of selenium by the MOF (including pH, adsorption time, and amount of MOF) together with main parameters of hydride generation (including concentrations of HCl and NaBH4) were carefully evaluated. Experimental results show that effective matrix separation can greatly reduce interference, with an excellent detection limit of 1 ng/L. The practicability and accuracy of this method were successfully confirmed by the determination of trace selenium in several food samples. SignificanceUiO-66-NH2 (MOF) was used as an effective adsorbent for the preconcentration of selenium prior to direct slurry sampling HG-ICP-MS determination. Direct slurry sampling avoided additional elution procedures and was conducive to eliminating matrix and isobaric interferences. High sensitivity and anti-interference determination were achieved for determination of ultra-trace Se in complex food samples.

Ultralong hydroxyapatite nanowires-based flow-through reactor with high loading of silver nanoparticles for fast continuous catalytic reduction of organic dyes and disinfection of wastewater

The noble metal nanoparticles (NPs) immobilized flow-through reactors have attracted significant attention for the continuous and efficient purification of wastewater contaminated with organic dyes and microorganisms without the need of subsequent recycling processes. However, achieving both high loading of noble metal NPs and high permeation flux concurrently has been a challenge for most reported flow-through reactors. In this study, inspired by the mussel bio-adhesion strategy, we have employed the tannic acid coating method and successfully synthesized Ag NPs-loaded ultralong hydroxyapatite (HAP) nanowires that exhibited an ultra-high loading amount (21.8 wt%). These nanowires were utilized as building blocks alongside chitosan (CS) to fabricate robust and highly porous flow-through reactors (Ag@HAP/CS) for continuous catalytic reduction of organic dyes and water disinfection. The Ag@HAP/CS reactor demonstrates excellent catalytic reduction efficiency (99.3 %) towards MEB at a high flux (2000 L m−2 h−1) with an extremely low concentration of NaBH4 (MEB:NaBH4 = 1:1). This result is attributed to the high loading of Ag NPs, great structural stability in flowing water, and sufficient length along the flowing direction. The reactor also shows remarkable recyclability through water flushing. Ag@HAP/CS exhibits remarkable water disinfection performance against Escherichia coli and diverse bacteria in natural river water, achieving nearly 100 % disinfecting efficiency. This study provides new insights into the strategy of using nanomaterials as intermediate carriers of noble metal nanoparticles to fabricate 3D flow-through reactors, which enable fast and continuous purification of wastewater with ultra-high catalytic efficiency and antimicrobial performance.

Cobalt-free CuO catalyst for hydrolytic dehydrogenation of sodium borohydride and ammonia borane

The environmental and economic impact of Co-based catalysts necessitates the use of a more environmentally friendly and less expensive catalyst, such as CuO. A cobalt-free CuO catalyst was developed via a simple low-temperature hydrothermal process. The efficiency of the catalyst was analysed for the dehydrogenation of NaBH4 as well as NH3BH3. Compared with the commercial particulate CuO, hydrothermally prepared CuO nanoplate (CuO HT) exhibits a good hydrogen evolution rate, the rate of hydrogen evolution for CuO_Commercial and CuO HT was experimentally measured to be 240 ml H2/min/g and 470.5 ml H2/min/g respectively for 0.2 g catalyst for the dehydrogenation of NaBH4. At a 10 times lower concentration of NaBH4 with 0.2 g of CuO HT catalyst, the rate of HER recorded was 1086 ml H2/min/g. The high catalytic activity of CuO HT could be related to the surface oxygen vacancies or defects generated due to the participation of high molar concentrations of NaOH during the reaction. The stability of both catalysts was investigated, and the rate of hydrogen evolution reaction after three cycles was determined to be 492 ml H2/min/g for CuO_Commercial and 925.1 ml H2/min/g for CuO HT. Despite the fact that the rate of hydrogen evolution was observed to be increased for the third cycle, the volume of water displaced was decreased when compared to the first cycle, which could be due to the presence of a less active Cu2O phase retained after temperature treatment. Similarly, with the best catalyst concentration of CuO HT (0.2 g), the hydrogen evolution rate of NH3BH3 was also measured to be 1175 ml H2/min/gm. The result evokes a new insight into the evolution of sustainable and eco-friendly catalysts for a better hydrogen economy.

Selective and sensitive colorimetric detection of endocrine disrupter fungicide carbendazim through secnidazole capped silver nanoparticles

Pesticides and fungicides are extremely useful to hinder the attacks of pests and fungi to secure crops, vegetables, fruits and other plants but due to their endocrine disrupting and carcinogenic risks in humans and animals through their continued addition in water resources they are extremely important to monitor carefully. In this investigation we synthesized silver nanoparticles (AgNPs) via the reducing action of sodium borohydride in the presence of secnidazole (SEC) as capping agent under various optimized parameters such as the concentration of NaBH4, silver nitrate (AgNO3), SEC and pH. These SEC-AgNPs were characterized through various techniques including ultra-violet visible (UV–Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and zeta-potential analysis (ZPA) in order to investigate their diverse properties. As prepared SEC-AgNPs were proved as extremely sensitive for trace level sensing of fungicide carbendazim (CARB) in the range of 0.5–22 µM with limit of detection (LOD) equal to 0.021 µM and R2 value of 0.9964. SEC-AgNPs were tested for CARB sensing under the presence of several pesticides with negligible interference thus verifying its exclusive selectivity for the targeted analyte. This SEC-AgNPs was further applied to find out the concentration of CARB in real samples of tap water and human blood plasma with reference to standard addition method.

Rapid Colorimetric Sensor Based on Gold Nanoparticles Functionalized 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole for Cortisol Detection in Saliva Sample

The rapid, simple, and selective colorimetric sensing method of cortisol has been successfully developed using AuNPs modified with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AuNPs-AHMT). The principle of this method is based on the color change from wine red to purple (redshift) when AuNPs-AHMT interacts with cortisol. The hydrogen bonding between the hydroxyl group from cortisol and the amine group from AHMT induces the aggregation of AuNPs. The modification of the AuNPs surface with AHMT aims to increase its stability. The properties of AuNPs and AuNPs-AHMT were characterized by UV-vis spectrophotometer. The interaction between AuNPs-AHMT and cortisol was studied by UV-vis and FTIR spectroscopies. The proposed method was optimized and validated. Au(III) was reduced to AuNPs at an optimum NaBH4 concentration of 1.0 mM. Validation of the proposed method showed good analytical performance with linearity from 1.0–50.0 nM, accuracy 91.07–102.77%, intra-day precision &lt; 2.22% and inter-day precision &lt; 2.17%, detection limit 0.76 nM, quantification limit 2.54 nM, and sensitivity 0.0112 nM/mL. The proposed method also showed good selectivity with the presence of some interferences in the sample. The proposed method was successfully applied for the determination of cortisol in the saliva by the standard addition method with acceptable recovery.

Study of morphological aspects in the efficient adsorptive removal of heavy metal ions using graphene oxide-chitosan based magnetic nanocomposite (0.4Fe0x:6x@GCS)

A one pot approach is followed to achieve an optimized synthesis of a benign magnetic nano composite and its applicability is explored in alleviation of toxic heavy metal ions from contaminated water. Untreated industrial effluents are among one of the major contributors in escalating the levels of heavy metals in residual water and soil, hence posing a serious threat to the humankind and the environment. With the motive in mind to treat such effluents, we fabricated a magnetic ternary nano-composite (NC) Fe0x:x@GCS (x:x is the concentration of Fe(II): concentration of NaBH4) aiming to reduce the levels of heavy metal ions (Pd, Cd, Cu & Ni) in polluted water. The initial concentration of Fe (II) precursor salt and the dosage of the reducing agent (NaBH4) were tactically adjusted to get desirable morphological and structural features in ultimate magnetic Fe0x:x@GCS NC with profound effect in eliminating the heavy metals ions from waste water. The effects of varying these two factors on the overall removal efficiency of heavy metal ions of the Fe0x:x@GCS are studied and analyzed. XRD, SEM & EDS techniques are used for the study of morphological and structural aspects of the synthesized materials and their comparative analysis. The reaction kinetics of the removal process of Pb(II) ions by the Fe0x:x@GCS NC was found best fitted to pseudo second order kinetics and the reaction isotherm was found better explained by Langmuir isotherm. Mechanistic aspects of the removal process of Pb (II) ions could be explained by XRD analysis of NC before and after the treatment with polluted water. Furthermore, to simulate the real waste water conditions, a mixture containing Pb (II), Cd (II), Ni (II) and Cu (II) heavy metal ions was also treated with NC which exhibited the removal efficiency of >99% .

Facile “Green” synthesis of a novel Co–W–B catalyst from Rheum ribes shell extract and its effect on sodium borohydride hydrolysis: Kinetic mechanism

The present investigation aimed to assess the influence of the Co–W–B NPs catalyst on the process of sodium borohydride hydrolysis. The study involved the synthesis of Co–W–B NPs through the utilization of an eco-friendly green synthesis extract derived from the Rheum ribes shell in conjunction with the chemical reduction technique for catalyst production. The investigation of catalysts' structure and surface morphology was conducted through the utilization of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) techniques. The average particle size was determined to be 35 nm in TEM analysis. The presence of Co–W–B nanoparticles and their elemental composition % were determined through EDX analysis, revealing values of 63.9% (Co), 31.89% (C), 1.75% (B), and 2.46% (W) within the nanoparticle. The manufactured Co–W–B catalyst's use for hydrolysis of sodium borohydride was studied under various conditions, including different concentrations of NaOH and NaBH4, different amounts of catalyst, and different temperature parameters. The hydrogen production rate for the Co–W–B NPs catalyst in NaBH4 hydrolysis was determined to be 5367 mLg−1min−1 at 30 °C. The study involved the determination of TOF values for a catalyst composed of Co–W–B NPs, which were subjected to varying temperatures. The activation energies were determined through the utilization of the n-th order and Langmuir-Hinshelwood kinetic models and subsequently calculated using the Arrhenius equation, resulting in values of 35.36 and 31.70 kJ/mol, respectively. The values of enthalpy and entropy, ΔH and ΔS, were determined through the utilization of Eyring's equation, 18.49 kJ/mol and −80.7 J/mol.K, respectively.

Synthesis of waste eggshell-derived Au/Co/Zn/eggshell nanocomposites for efficient hydrogen production from NaBH4 methanolysis

Developing new pathways to transform biological wastes into value-added products is inevitable in order to mitigate environmental pollution and providing sustainability. Utilisation of eggshell as a substrate, a naturally abandoned organic-inorganic waste, was explored in this study. Herein, Au/Co/Zn/eggshell nanocomposites were synthesised by utilizing waste eggshell as substrate. At the experimental stage, different metal combinations namely unary, binary and ternary combination of Co, Zn and Au and different ratios ranges from %10 to %50 were tested. The catalytic activity of the synthesised materials were investigated in terms of hydrogen production from NaBH4 methanolysis. The catalyst fabricated with the addition of %40 Co + %40 Zn + 3 ppm Au showed the best catalytic activity and the reaction completion time was as low as 2.4 min. The results revealed that the fabricated catalyst showed a superior catalytic activity with the maximum hydrogen production rate of 4394.6 mL/min/gcat. The obtained maximum hydrogen production rate is highly compatible with the existing literature. Different NaBH4 concentrations and catalyst concentrations were also tested to investigate the fabricated catalyst behaviour. The fabricated catalyst was also experimented in different temperatures range from 30 °C to 60 °C to determine the Arrhenius kinetics and subsequently activation energy. The activation energy was calculated to be 13.25 kJ/mol. SEM-EDX, BET, XRD and FT-IR analysis were finally performed to determine morphological and structural characterization of the superior catalyst.