Apparent Rate Constant Research Articles

Self-regulated S-scheme heterojunction for synergistic removal of tetracycline and hexavalent chromium: Synergistic mechanism of trivalent chromium

The limitation of conventional photocatalysts in simultaneously removing Tetracycline (TC), hexavalent chromium (Cr (VI)) and trivalent chromium (Cr (III)) were addressed in mixed pollution treatment. The S-scheme heterojunction of titanate nanotubes/Bi2WO6 (TNTs/BWO) was successfully constructed to achieve efficient removal of TC, Cr (VI), and Cr (III). The theoretical calculations (DFT) demonstrated that TNTs’ ion exchange properties led to the partial replacement of interlayer Na+ by Cr (III), optimizing the S-scheme heterojunction during the photocatalytic reaction. Experimental results revealed that the coexistence of TC, Cr (VI), and Cr (III) had a mutual promotion effect, as evidenced by the apparent rate constant of Cr (VI) reaching 0.7 min−1, which was 87.5 times higher than that of the single pollutant system, while maintaining a high apparent rate constant for TC. The likely intermediate products, degradation pathways, and photocatalytic mechanism were also elucidated using DFT molecular orbitals and Fukui index analysis. This work provides new insights and strategies for simultaneously removing pollutants and contributes to wastewater purification.

Tunable Non-Enzymatic Glucose Electrochemical Sensing Based on the Ni/Co Bimetallic MOFs.

Constructing high-performance glucose sensors is of great significance for the prevention and diagnosis of diabetes, and the key is to develop new sensitive materials. In this paper, a series of Ni2Co1-L MOFs (L = H2BPDC: 4,4'-biphenyldicarboxylic acid; H2NDC: 2,6-naphthalenedicarboxylic acid; H2BDC: 1,4-benzenedicarboxylic acid) were synthesized by a room temperature stirring method. The effects of metal centers and ligands on the structure, compositions, electrochemical properties of the obtained Ni2Co1-L MOFs were characterized, indicating the successful preparation of layered MOFs with different sizes, stacking degrees, electrochemical active areas, numbers of exposed active sites, and glucose catalytic activity. Among them, Ni2Co1-BDC exhibits a relatively thin and homogeneous plate-like morphology, and the Ni2Co1-BDC modified glassy carbon electrode (Ni2Co1-BDC/GCE) has the highest electrochemical performance. Furthermore, the mechanism of the enhanced glucose oxidation signal was investigated. It was shown that glucose has a higher electron transfer capacity and a larger apparent catalytic rate constant on the Ni2Co1-BDC/GCE surface. Therefore, tunable non-enzymatic glucose electrochemical sensing was carried out by regulating the metal centers and ligands. As a result, a high-sensitivity enzyme-free glucose sensing platform was successfully constructed based on the Ni2Co1-BDC/GCE, which has a wide linear range of 0.5-2899.5 μM, a low detection limit of 0.29 μM (S/N = 3), and a high sensitivity of 3925.3 μA mM-1 cm-2. Much more importantly, it was also successfully applied to the determination of glucose in human serum with satisfactory results, demonstrating its potential for glucose detection in real samples.

Electrochemical enhanced heterogeneous activation of peroxymonosulfate by CoFe2O4 nanoparticles to degrade moxifloxacin

The catalytic mechanism of CoFe2O4 nanoparticles (NPs) was investigated in the system of electrochemical enhanced heterogeneous activation of peroxymonosulfate (EC/CoFe2O4/PMS) with moxifloxacin (MOX) as target contaminant. The removal efficiencies of MOX in PMS, CoFe2O4, EC, CoFe2O4/PMS, and EC/CoFe2O4/PMS system were 18.3%, 36.1%, 43.7%, 96.9%, and 98.3%, respectively. Although there was no synergy effect between EC and heterogeneous catalytic oxidation reaction (HCOR) on MOX removal, the value of apparent rate constant (karc) was much higher in EC/CoFe2O4/PMS system (0.24 min−1) compared with CoFe2O4/PMS system (0.13 min−1). Therefore, EC not only kept the structure of CoFe2O4 NPs stable, but also significantly accelerated the reaction rate of HCOR. Meanwhile, according to electrochemical impedance spectra of catalysts synthesized based on ion-substitution strategy and the EC-HCOR experimental results, the decisive role of Co in PMS activation and the electron transfer between Co and Fe were confirmed. The TOC removal efficiency was reached 74.4% as the ratio of PMS to CoFe2O4 NPs being 0.8 mM to 50 mg/L (30 min), and further improved to 87.6% with batch addition (0.25 mM per 30 min) of PMS (120 min, CoFe2O4 = 100 mg/L). The research results could improve the understanding of catalytic mechanism of spinel oxide in electrochemical system.

Dual metal ions/BNQDs boost PMS activation over copper tungstate photocatalyst for antibiotic removal: Intermediate, toxicity assessment and mechanism

In the metal-based peroxymonosulfate (PMS) activation process, the sluggish surface redox cycle of metal ions generally hampered the efficiency of PMS activation for pollutant removal. Herein, Co-doped CuWO4/BN quantum dots (CW/Co/BNQDs) photocatalysts were developed to realize Cu2+/Cu+ and Co2+/Co3+ dual ions redox cycles for PMS activation, which would facilitate the tetracycline (TC) removal. CW/4Co/2BNQDs could degrade 94.8% TC within 30 min in PMS/Vis system, and the apparent rate constant of CW/4Co/2BNQDs was 2.7 times and 1.2 times higher than those of CW and CW/4Co, respectively. The improved TC degradation performance could be attributed to the synergetic effect between BNQDs and dual redox cycles. X-ray photoelectron spectroscopy (XPS) spectra of samples before and after the reaction demonstrated that BNQDs were beneficial for accelerating the Cu2+/Cu+ and Co2+/Co3+ redox cycles in CW/4Co/2BNQDs, further boosting the activation of PMS in TC degradation. Experiments of different radical scavengers revealed that the SO4·−/·OH/h+/1O2 reactive species participated in the PMS activation for the TC degradation process. The possible TC degradation pathway and intermediate toxicity were detailed investigated. In addition, CW/4Co/2BNQDs exhibited outstanding photocatalytic activity over five consecutive cycles, which illustrated that it was supposed to be a reliable PMS activator over antibiotic elimination for practical application. And this work shed new light on constructing dual redox cycles for efficient PMS activation.

Fe-zeolites for the adsorption and oxidative degradation of nitroaromatic compounds in water

Nitroaromatic compounds (NACs) are prominent explosives. In this context, these toxic substances were released into the environment and cause long-lasting groundwater contamination. In preparation of a possible in-situ remediation, colloidal Fe-zeolites were investigated for their capabilities as adsorbents and oxidation catalysts. It was shown that the Fe-zeolites FeBEA35 and FeFAU55 are potent inorganic adsorbents for NACs and simultaneously capable of activating H2O2 as Fenton-like oxidation catalysts. Adsorption isotherms of 15 NACs on both zeolites were measured to evaluate the option of coupling adsorptive contaminant enrichment with oxidative degradation. The faujasite-type zeolite FeFAU55 showed a distinct S-type adsorption behaviour and reached significantly higher NAC loadings of > 20 wt%. For FeBEA35, L-type adsorption isotherms and maximum loadings qmax of about 4 wt% were obtained. Degradation of all NACs, monitored by nitrate formation, was observed. Apparent rate constants of the NACs with hydroxyl radicals in a homogeneous, stoichiometric Fenton reaction were related to the heterogeneous system to examine the role of adsorption on the oxidative degradation. Beneficial influence of the adsorption on the oxidation rates was identified. The results of this work open up promising prospects for future application of Fe-zeolites for the in-situ remediation of NAC-contaminated groundwater.

Kinetic model describing self-limiting CO2 diffusion in supported amine adsorbents

A reaction–diffusion shrinking core model describing the decay in diffusivity of supported amine sorbents upon CO2 sorption under both simulated direct air capture and point source capture conditions is described. The decay in CO2 diffusivity is associated with crosslinking in the aminopolymer samples and general pore blockage in the amino-silane derived samples, which occurs as CO2 is adsorbed. The model is used to extract four kinetic parameters that govern the CO2 uptake kinetics and working capacity: an apparent reaction rate constant, an initial effective diffusivity, and two dimensionless decay parameters. Ideally, an initially reaction limited system would allow for direct determination of the intrinsic reaction rate constant; however, sorption experiments suggest mass transfer resistances related to gas mixing, external boundary layers and intraparticle diffusion are present. Reaction rate constants are determined and agree well with theoretical values predicted with the Eyring equation parameterized using density functional theory energies from literature sources. The kinetic performance is expressed as the average effective diffusivity as a function of average conversion, which can be correlated to the dispersion of sorption sites on the support and the morphology of the active sorbent phase. Four supports are impregnated or grafted with amines, SBA-15, single-walled zeolite nanotubes (ZNT), Syloid SiO2, and γ-Al2O3. Due to its pore structure, γ-Al2O3 supported amines can be modeled at the μm scale or at the nm scale, where the shell balance is on the μm-sized macroporous particle aggregate or on the nm-sized amine film on the surface of the Al2O3 nanoparticles, which comprise the spherical particle aggregates. Faster diffusion rates are maintained under 400 ppm rather than 10% CO2 due to a slower reaction rate giving a slower decay in diffusivity. This work provides a first principles kinetic analysis of CO2 sorption where previous models are semi-empirical and use arbitrary kinetic parameters.

A facile synthesis of coral tubular g-C3N4 for photocatalytic degradation RhB and CO2 reduction

Photocatalysis is an ecofriendly technique that emerged as a promising alternative for solar-to-clean energy conversion and pollutant degradation. Such g-C3N4 have demonstrated chemical stability and proper band position but with low specific surface area, limited light absorption, and easy recombination of photo-generated carriers. In this paper, we report on the successful synthesis of coral tubular g-C3N4 photocatalyst using a supramolecular-based approach. Among the as-synthesized samples, M1C2 (melamine-to-cyanuric acid molar ratio of 1:2) exhibited the best photocatalytic performance. The apparent rate constant of RhB degradation was 1.53 times greater than that of M1C0 (pure melamine), and the yield of CO is about 3 times higher than that of M1C0 during CO2 reduction. The formation of tubular structures increased the specific surface area and reduced the recombination efficiency of electron-hole pairs. Moreover, the position of the conduction band became more negative, generating more radicals that accelerated the process of photocatalysis. This work offered a practical and achievable approach to creating superior g-C3N4 and facilitating its application in diverse fields.

Selective Thermal and Photocatalytic Decomposition of Aqueous Hydrazine to Produce H2 over Ag-Modified TiO2 Nanomaterial.

An Ag-modified TiO2 nanomaterial was prepared by a one-pot synthesis method using tetra butyl titanate, silver nitrate, and sodium hydroxide in water at 473 K for 3 h. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to determine the structure and morphology of the synthesized Ag-modified TiO2 nanomaterial. The diffuse reflectance UV-visible and photoluminescence spectroscopy results revealed that metallic Ag nanoparticles decreased the optical band gap and photoluminescence intensity of the TiO2. In addition, the Raman peak intensity and absorbance were increased after Ag modification onto TiO2. The photocatalytic efficiency of the synthesized samples was tested for decomposition of aqueous hydrazine solution under visible light irradiation. The photocatalytic efficiency of Ag-modified TiO2 nanomaterials was higher than that of bare TiO2 and Ag metal NPs due to the synergistic effect between the Ag metal and TiO2 structures. In addition, the surface plasmon resonance (SPR) electron transfer from Ag metal particles to the conduction band of TiO2 is responsible for superior activity of TiO2-Ag catalyst. The Ag-modified TiO2 nanomaterials offered a 100% H2 selectivity within 30 min of reaction time and an apparent rate constant of 0.018 min-1 with an activation energy of 34.4 kJ/mol under visible light radiation.

Development and characterization of a latex turbidimetric immunoassay using rabbit anti-CRP single-chain Fv antibodies

In this study, we developed and demonstrated a latex turbidimetric immunoassay (LTIA) using latex beads immobilized with rabbit monoclonal single-chain variable fragments (scFvs) selected from an scFv-displayed phage library. Sixty-five different anti-c-reactive protein (anti-CRP) scFv clones were identified after biopanning selection using antigen-coupled multi-lamellar vesicles. By ranking antigen-binding clones using the apparent dissociation rate constant (appkoff) as a sorting index, scFv clones with a dissociation constant (KD free) ranging from 4.07 × 10−9 M to 1.21 × 10−11 M were isolated. Among them, three candidates (R2–6, R2–45, and R3–2) were produced in the culture supernatant at concentrations of 50 mg/L or higher in flask culture and maintained at considerably high antigen-binding activity in immobilized state on the CM5 sensor chip surface.All the scFv-immobilized latexes (scFv-Ltxs) prepared were well-dispersed in 50 mM MOPS at pH 7.0, without additives for dispersion, and their antigen-dependent aggregation was sufficiently detectable. The reactivity of scFv-Ltx to antigen differed among the scFv clones, in particular, R2–45 scFv-Ltx detected the CRP with the highest signal. Furthermore, the reactivity of scFv-Ltx varied significantly with salt concentration, scFv immobilization density, and the type of blocking protein. Particularly, antigen-dependent latex aggregation improved significantly in all rabbit scFv clones when scFv-Ltx was blocked with horse muscle myoglobin compared with conventional bovine serum albumin; while their baseline signals in the absence of antigen were fully stable. Under optimal conditions, R2–45 scFv-Ltx exhibited greater aggregation signals with antigen concentrations higher than those produced by conventional polyclonal antibody-immobilized latex for CRP detection in LTIA. The methodology for rabbit scFv isolation, immobilization, and antigen-dependent latex aggregation demonstrated in the present study can be applicable to scFv-based LTIA for various target antigens.

Disulfides form persulfides at alkaline pH leading to potential overestimations in the cold cyanolysis method

It is well established that proteins and peptides can release sulfur under alkaline treatment, mainly through the β-elimination of disulfides with the concomitant formation of persulfides and dehydroalanine derivatives. In this study, we evaluated the formation of glutathione persulfide (GSSH/GSS-) by exposure of glutathione disulfide (GSSG) to alkaline conditions. The kinetics of the reaction between GSSG and HO- was investigated by UV–Vis absorbance, reaction with 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB), and cold cyanolysis, obtaining an apparent second-order rate constant of ∼10-3 M-1 s-1 at 25 °C. The formation of GSSH and the dehydroalanine derivative was confirmed by HPLC and/or mass spectrometry. However, the mixtures did not equilibrate in a timescale of hours, and additional species, including thiol and diverse sulfane sulfur compounds were also formed, probably through further reactions of the persulfide. Cold cyanolysis is frequently used to quantify persulfides, since it measures sulfane sulfur. This method involves a step in which the sample to be analyzed is incubated with cyanide at alkaline pH. When cold cyanolysis was applied to samples containing GSSG, sulfane sulfur products that were not present in the original sample were measured. Thus, our results reveal the risk of overestimating the amount of sulfane sulfur compounds in samples that contain disulfides due to their decay to persulfides and other sulfane sulfur compounds at alkaline pH. Overall, our study highlights that the β-elimination of disulfides is a potential source of persulfides, although we do not recommend the preparation of GSSH from incubation of GSSG in alkali. Our study also highlights the importance of being cautious when doing and interpreting cold cyanolysis experiments.

Silver/Titanium nanoparticles encapsulated microgel for catalytic reduction

Organic dyes and nitro compounds have become major pollutants that effect our ecosystem and hazardous to living things. Bimetallic nanoparticles loaded with microgel catalytic system was synthesized for the reduction of these pollutants. Poly (N-isopropylacrylamide-co-methacrylic acid) p(NIPAM-MAAc) microgel was synthesized by free radical precipitation method and latterly silver (Ag) and titanium (Ti) nanoparticles were loaded inside the microgel by in-situ chemical method. Different techniques were used to characterize the hybrid microgel such as Fourier transform-infrared spectroscopy, scanning electron microscopy, dynamic light scattering as well as UV-visible spectroscopy. The average size of hybrid microgels were observed 139 nm with the Polydispersity index of 0.313 by DLS. The smaller value of PDI indicates that nanoparticles were homogeneously dispersed inside the microgel. The synthesized hybrid microgels were used as catalyst for reduction of various compounds such as, 2,4-dinitrophenol (2,4-DNP), congo red (CR), 4-nitrophenol (4-NP), methyl orange (MO), methyl red (MR), 2-nitrophenol (2-NP), crystal violet (CV), 3-nitrophenol (3-NP), methyl blue (MB) and eriochrome black T (EBT) in the presences of NaBH4 reducing agent. Apparent rate constant of CV, CR and EBT 0.3234, 0.2315 and 0.1697 min-1 were observed highest among other substrate.

In situ deposition of double Fe-based Fenton catalysts on the porous membrane for the development of multi-defense against various foulants toward highly efficient water purification

Membrane separation technology has been widely employed in wastewater separation, although, it is restricted by terrible membrane fouling. The acceptable “single defense” is insufficient to generate a desirable antifouling surface against various organic foulants in complex wastewater. Therefore, this work designs and constructs a porous surface with “multi-defense” by integrating hydrophilic, underwater superoleophobic, and anti-bacterial nano Fe-based Fenton catalysts of β-FeOOH nanorods and CuFeO2 nanoparticles on the polyvinylidene difluoride membrane via metal-ion-induced deposition process. The obtained composite membrane (MFeOOH/CF) has ultra-stable underwater superoleophobicity and ultra-low oil adhesion, which prevent oils from adhering to the membrane and benefit to separate various surfactant-stabilized oil-in-water emulsions with high water flux and separation efficiency of 99%. MFeOOH/CF also exhibits nearly 100% bactericidal activity against Escherichia coli. Moreover, the various foulants (such as bovine serum albumin, methylene blue, and crude oil) adhered to the membrane after filtration can be successfully degraded by MFeOOH/CF under the solar-driven Fenton process, leading to ultrahigh flux recovery ratio (FRRV) of 98.2 ± 0.3% and a low irreversible fouling ratio (RirV) of 2.0 ± 0.1%. The apparent degradation rate constant (k) of MFeOOH/CF is 2.5 times the β-FeOOH coated membrane (MFeOOH) because the introduction of CuFeO2 nanoparticles provides more reactive sites and lowers the Fe3+/Fe2+ redox potential. This study is working to bring about a highly efficient “multi-defense” on the porous membrane, which will realize membrane regeneration and boost wastewater purification.

Effects of Internal Electron Donor on Distribution and Reactivity of Active Centers in Ethylene/1‐Hexene Copolymerization with MgCl2‐Supported Ziegler‐Natta Catalyst

AbstractEthylene/1‐hexene copolymerization with two MgCl2‐supported Ziegler‐Natta catalysts containing no internal electron donor or diethylphthalate (DEP) is conducted for different polymerization time . Effects of DEP on active center distribution are studied by fractionating each copolymer sample into boiling n‐heptane soluble (C7‐sol) and insoluble (C7‐ins) fractions, and counting the number of active centers in the copolymer fractions . The main effect of introducing DEP in the catalyst are reduction in the Ti content and significant increase in the proportion of active centers producing C7‐ins fraction. The propagation rate constants of ethylene insertion (kpE) and 1‐hexene insertion (kpH) are respectively estimated by linear fitting/extrapolating the change of apparent propagation rate constants (kpi)a with polymer yield according to a simplified multi‐grain particle model. In both catalysts, kpE in the C7‐ins fraction is 9–12 times larger than that in the C7‐sol fraction, and kpH in the C7‐ins fraction is 3–4 times larger than that in the C7‐sol fraction. The two groups of active centers have distinctly different catalytic properties. Introducing DEP reduced the kpE and kpH values and the extent of diffusion limitation . In summary, addition of electron donor in MgCl2‐supported Z‐N catalyst significantly changed the active center distribution and catalytic properties of its two groups of active centers.

The kinetics of Ni/Al2O3 and Ni-Fe/Al2O3 catalysts for the CO2 methanation reaction and the reasons for promotion

Replacing nickel with iron is known to promote supported nickel catalyst for CO2 methanation. This promotion is often attributed to the presence of Ni-Fe alloy. However, the effect of replacing Ni with Fe on a common rate expression of CO2 methanation and the specific causes leading to the promotion are not addressed. To achieve these objectives, we synthesize and characterize an alumina supported Ni, 15NiAl, and two alumina supported Ni-Fe catalysts, 15Ni7FeAl and 15Ni3FeAl. These catalysts contain 15 wt% of Ni or Ni + Fe. In 15Ni7FeAl and 15Ni3FeAl the Ni/Fe ratio = 7 and 3, respectively. Characterization studies reveal the presence of smaller Ni-Fe alloy particles in the reduced and spent 15Ni7FeAl and 15Ni3FeAl catalysts. Other characteristics of the catalysts are also identified. With these catalysts we carry out the CO2 methanation reaction under different operating conditions. The enhancement in rate of CH4 formation, rCH4, while using the two bimetallic supported catalysts strongly depends on the Ni/Fe ratio, reactant partial pressures and temperatures. We modify an existing rate expression to adequately represent the reaction data of the three catalysts. In this rate expression, the surface reaction between molecularly adsorbed reactant gases is the rate-determining-step. As Ni is progressively replaced with Fe in the bimetallic catalysts, the apparent rate constants and equilibrium constants for the adsorption of CO2 and H2 of the rate expression increases, which increases rCH4. Under all operating conditions the 15Ni3FeAl catalyst shows the best rCH4 and the apparent rate constants and equilibrium constants are the largest. It appears that the Ni-Fe alloy increases the number of adsorption-sites and the fractional coverage of adsorbed CO2 and H2, which then results in enhanced rCH4 values.

Study of norfloxacin degradation by advanced oxidation process using UV/TiO2/H2O2 in an annular reactor

Norfloxacin (NFX) residual was frequently found in domestic wastewater, sewage treatment plants, hospital wastewater, and surface water like lakes and rivers. This threatens the ecological balance of the environment. Moreover, normal biological treatment methods (including membrane bioreactor - MBR) are not feasible for the removal of NFX. In this study, the degradation of NFX through advanced oxidation processes (AOPs) utilising UV/TiO2 and H2O2 as reagents in a laboratory-scale tubular reactor system was conducted. The degradation reactions of NFX could be represented by the Langmuir-Hinshelwood kinetic model. The influence of factors, including TiO2and H2O2 concentrations, UV irradiation intensity, and hydrodynamic conditions (specifically, Reynolds number), on the apparent reaction rate constant (kapp) was evaluated. The results demonstrated that the advanced oxidation process employing the combined reagents of UV/TiO2/H2O2 under the following reaction conditions: TiO2 and H2O2concentrations of 0.2 g/l and 0.0492 mol/l, UV irradiation intensity of 225 W/m2, and Reynolds number of 6700, achieved an apparent degradation reaction rate constant for NFX of 0.052 min-1.

Structure‐Induced Enhanced Dissolving Properties of Mg(OH)2 Prepared by Glycine‐Assisted MgO Hydration

AbstractMg(OH)2’s dissolving properties have a considerable influence on its application performance. This study aims to improve the dissolving properties of Mg(OH)2 by modifying its crystal structure. Mg(OH)2 crystals with a large diameter‐to‐height ratio (≈40) structure are synthesized via a glycine‐assisted MgO hydration method utilizing glycine's differing adsorption energy on the (001) and (110) surfaces of Mg(OH)2 (−306.2 and −277.4 kJ mol−1). Compared to the control sample, the results of the dissolution kinetics investigation indicate that glycine‐assisted hydration considerably improves the apparent reaction rate constant of dissolution from 0.0020–0.0071 to 0.0039–0.0120 min−1. The enhanced dissolving properties are mostly induced by the large and thin crystal grain structure, which disintegrates easily during the dissolution process, exposing more reactive sites. The findings reported in this study provide a new approach to improving the dissolving properties of Mg(OH)2 that can enable its enhanced use in various applications.

Synthesis of Dual Z-Scheme CuBi2O4/Bi2Sn2O7/Sn3O4 Photocatalysts with Enhanced Photocatalytic Performance for the Degradation of Tetracycline under Visible Light Irradiation

The dual Z-scheme heterojunction CuBi2O4/Bi2Sn2O7/Sn3O4(CBS) was successfully constructed through in situ growth methods, and its photocatalytic performance was evaluated via degradation of tetracycline hydrochloride under visible light. Out of all samples, CBS-2 exhibited the highest photocatalytic activity, with an apparent rate constant of 2.34, 20.16, and 44.17 times that of Bi2Sn2O7, CuBi2O4, and Sn3O4, respectively. Even after four cycles, the photocatalytic efficiency remained above 85%. The improvement can be attributed to the construction of the Z-scheme heterojunction, which effectively promotes the separation and migration of photogenerated carriers. The possible photocatalytic degradation mechanism of dual Z-scheme heterojunction CBS was deduced based on the theory of free radical capture and energy band.

Degradation of Lignin Pollutants by Persulfate Activated with a Graphene Oxide Loaded Cu2(OH)3NO3 Composite

AbstractGraphene oxide (GO)‐Cu2(OH)3NO3 composite was prepared by a thermal calcination process and evaluated as an effective heterogeneous catalytic material. The composite displayed prominent activated performance to persulfate, which was influenced by preparation condition and the reaction parameters in catalytic system. Under optimal reactive conditions, the GO‐Cu2(OH)3NO3 composite yielded rapid degradation of ferulic acid, which the corresponding apparent rate constant was 1.12×10−1 min−1. Catalytic mechanism analysis showed that the main oxygen species were ⋅SO4− and ⋅OH. Among them, ⋅OH made the main contribution in the catalytic system. The analysis of degradation intermediates of ferulic acid showed that the compound could be mineralized to small molecules. The remarkable enhanced heterogeneous catalytic performance of GO‐Cu2(OH)3NO3 was due to a larger specific surface area, high adsorption capacity and a high mass transfer efficiency of oxidizing radicals in the reactive system.

Kinetics of base-promoted transformation of berberrubine-cucurbit[7]uril inclusion complex: Active role of alkali cations

A pH-responsive inclusion complex was created from berberrubine, a pharmacological active natural isoquinoline alkaloid and cucurbit[7]uril (CB7) macrocycle exploiting the more than four orders of magnitude larger binding affinity of the cationic guest (BOH+) compared to the deprotonated uncharged conjugate base (BO). Since only the CB7-encapsulated BOH+ emitted strong fluorescence, the transformation of this host–guest complex could be selectively monitored in real time by stopped-flow measurements. Alkali cations accelerated the exit of BOH+ from the CB7 cavity in a pseudo-first order reaction and their impact grew with the ion radius. In contrast, the gradual rise of alkali hydroxide concentration brought about parabolic increase in the apparent rate constant of the deprotonation of the CB7-embedded BOH+ and the reaction had the partial order of 1 with respect to alkali and hydroxide ions alike. LiOH induced the proton loss of the BOH+-CB7 complex much more efficiently than NaOH or KOH. These unexpected findings highlight the active role of alkali cations in the control of the kinetics of pH-responsive guest release from CB7 and provide a new way for the tuning of the temporal behavior of base-induced transformations of host–guest complexes.

Sandwich composites of bismuth sulfide nanoparticles decorated with cobalt ferrite oxide for waste water treatment

To detect cadmium (Cd2+) ions, electrochemical and calorimetric studies have been performed due to their high sensitivity and selectivity. Heterogeneous photocatalysts have been used to degrade and decolorize azo dyes because they are adaptable, cause less secondary pollution, and are cost-effective. In this study, synthesized Bi2S3 nanoparticles adorned on CoFe2O4 (BiSNPs@CFO) substrates by using chemical methods. The primary source of Cd2+ ions in digested detergent samples was detected and coded as samples A, B, and C. Laundry wastewater was denoted as sample D. Both photoluminescence spectroscopy (PL) and cyclic voltammetry techniques (CV) were employed to detect the presence of cadmium ion in the selected samples. Pollution assessment risk index values indicated that samples B and C contributed to Cd2+ ions pollution more compared with sample A. The Igeo (geo-accumulation) values were 4.08 (sample B), 3 (sample C), and 13.5 (sample D), which indicated a high pollution level. Then, the methylene blue (MB) dye was periodically degraded at a fixed concentration and pH, and the efficiency reached 83%, with the apparent rate constant of 0.0106/min with a high R2 value of approximately 0.9015. In this study, the two pathogens were isolated from laundry wastewater, namely, Aspergillus sp. and Trichoderma sp, and their growth and biomass production were examined. The antifungal activity of BiSNPs@CFO composites was studied using the standard fluconazole. The nanocomposites can be used as a probe to detect the presence of Cd2+ ions and degrade azo dyes and Aspergillus sp. and Trichoderma sp. predominantly grown in laundry wastewater.