Kinetic Model Research Articles

Evaluating the risk of data loss due to particle radiation damage in a DNA data storage system

DNA data storage is a potential alternative to magnetic tape for archival storage purposes, promising substantial gains in information density. Critical to the success of DNA as a storage media is an understanding of the role of environmental factors on the longevity of the stored information. In this paper, we evaluate the effect of exposure to ionizing particle radiation, a cause of data loss in traditional magnetic media, on the longevity of data in DNA data storage pools. We develop a mass action kinetics model to estimate the rate of damage accumulation in DNA strands due to neutron interactions with both nucleotides and residual water molecules, then utilize the model to evaluate the effect several design parameters of a typical DNA data storage scheme have on expected data longevity. Finally, we experimentally validate our model by exposing dried DNA samples to different levels of neutron irradiation and analyzing the resulting error profile. Our results show that particle radiation is not a significant contributor to data loss in DNA data storage pools under typical storage conditions.

Degradation of Remazol Brilliant Blue Dye Using Persulfate Activated by Fe3O4@PDA Nanoparticles: Kinetic Studies, Radical Determination, and Phytotoxicity Test.

In the current research work, an advanced oxidation process was applied to the degradation of Remazol brilliant blue dye (RBBD) using a sulfate radical. Fe3O4@PDA nanoparticles were synthesized using coprecipitation and self-polymerization techniques. Nanoparticle formation was confirmed by XRD, FTIR, FESEM-EDX, VSM, and XPS analyses. The crystalline nature of the material showed that it possessed a spherical shape with an Ms value of 58 emu/g. The elemental composition and binding energy from EDX and XPS analyses showed successful doping. Batch studies were conducted, and experimental studies showed that the optimum condition for degradation of 90 ppm of RBBD was 0.3 g/L of nanomaterial, 20 mM PS at pH 3, achieving 91.35% degradation. The kinetic model suitable for this study was a pseudo-second-order kinetic model with R2 value >0.9. From the radical identification tests, sulfate radicals played a dominant role in degradation, and to confirm it, EPR analysis was conducted using DMPO. A stability test was performed for 5 cycles in which the degradation efficiency was reduced appreciably. From XPS, XRD, and EDX analyses, the elemental composition and oxidation state of the recycled material used in the fifth cycle showed variation in a negligible manner when compared to the fresh catalyst used in the first cycle of the degradation experiment. Intermediate identification was done by GCMS analysis, and it disclosed the formation of aliphatic products from the degradation of RBBD with less toxicity. Phytotoxicity analysis was conducted using green grams for 10 days, and it proved that intermediates formed in the solution were nontoxic to the plants. Additionally, TOC and COD removal % were attained to be 80.021 and 80.903%, respectively, which confirm the mineralization efficacy. Hence, this research work proved the efficient performance of the catalyst for RBBD degradation with less formation of intermediates, and therefore, this technique is most suitable for the reduction of water pollution.

Enrichment of deoxynojirimycin in mulberry using cation exchange resin: Adsorption/desorption characteristics and process optimization

Deoxynojirimycin (DNJ) is an α-glucosidase inhibitor with high food values. However, the complex and costly enrichment processes have greatly prevented its application. Herein, this study aimed to propose a simple and efficient enrichment process for DNJ from Morus alba L. extracts using cation exchange resins. The LSI and D113 resins were chosen due to their excellent adsorption and desorption properties. The adsorption characteristics agreed with the pseudo-first-order kinetic model and the Langmuir isotherm model. This adsorption was chemisorption, spontaneous, endothermic and entropy-driven. Furthermore, the concentration and pH of the extracts, desorption solvent, breakthrough and elution curves, sample loading and elution rate were investigated to optimize the enrichment process by resin column chromatography. The results also showed that the purity of DNJ was improved to 44.00 % with a total recovery of 78.21 % using the LSI-D113 combination strategy. This research demonstrated the industrial feasibility of DNJ enrichment using cation exchange resins.

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

Innovation in Idli batter preservation through betel leaf essential oil-based nanoemulsion: Evaluating fermentation kinetics and physicochemical analysis

Extending shelf life while maintaining quality of traditional fermented foods is a major challenge. This study aimed to investigate betel leaf essential oil nanoemulsions (BLEONE) as a clean-label preservative for fermented Idli batter. BLEONE (1–10 %) was incorporated into Idli batter and evaluated for physicochemical properties, sensory quality, and shelf life during ambient (30 °C) and refrigerated (4 °C) storage. Kinetic modeling and analysis of variance (ANOVA) were used to quantify BLEONE's effects on fermentation dynamics and assess statistical significance. At 5 % concentration, BLEONE significantly (p < 0.05) maintained pH (4.5 vs 3.8 in control), restricted acidity increases (1.2 % vs 1.8 % in control), and limited viscosity loss (15 % vs 40 % in control) during fermentation compared to untreated and sodium benzoate-treated samples. Sensory analysis showed acceptable attributes up to 5 % BLEONE. Optimally fermented Idli batter with 5 % BLEONE extended shelf-life to 7 days at 30 °C and 25 days at 4 °C storage. The nanoemulsion's enhanced antimicrobial efficacy and controlled release of active compounds significantly improved safety and quality preservation during storage. This research demonstrates the potential of essential oil nanoemulsions as effective clean-label preservatives for traditional fermented foods, offering a promising solution to extend shelf life while maintaining product quality.

Cu-Ni Bimetallic Nanowires with Various Structures Originating from Ni Reduction Kinetics.

Bimetallic nanowires play important roles in the fields of electronics and mechanics. However, their structure types and morphological control methods are limited, especially for systems with low lattice mismatch. Herein, for a Cu-Ni bimetallic system with lattice mismatch ratio less than 2.5%, a novel preparation approach of various Cu-Ni nanowires dominated by Ni(II) reduction kinetics is presented. With the increase of Ni(II) reduction rate, the core-shell Cu@Ni straight nanowires, the asymmetric Cu-Ni nanocurves, and asymmetric Cu-Ni nanocoils can be prepared, respectively. The formation of Cu-Ni nanowires with different structures can be divided into the growth of Cu nanowires and the deposition of Ni. The regulatory effects were revealed by establishing a kinetic model for Ni(II) reduction. For the novel Cu-Ni asymmetrically distributed nanocurves and nanocoils, the formation mechanism was proposed by considering the Cu nanowire bending due to the rearrangement of surface ligand and bending-induced symmetry breaking of Ni(II) reduction.

Monodispersed FeS nanoparticles decorated on kaolinite for synchronous removal of benzo [a]pyrene and Cr(VI) complex pollution

Novel FeS/kaolinite composite (K-FeS) were successfully prepared using an in-situ precipitation method. At 30 % FeS loading, 1 g/L of the composite material by activating peroxymonosulfate (PMS) was able to completely remove 20 mg/L benzo[a]pyrene (BaP) and 40 mg/L Cr(VI) within 20 min under optimized conditions. The simultaneous removal experiments of BaP and Cr(VI) for the influence factors of BaP concentration, Cr(VI) concentration, composites dosage and PMS dosage to be 20 mg/L, 40 mg/L, 1 g/L, and 0.75 mmol/L, respectively. Experiments on environmental factors show that low temperature and acidic conditions are more favorable for material activity, and the addition of Cl- could promote the removal of BaP and Cr(VI). Comparative experiments showed that the simultaneous presence of BaP and Cr(VI) did not affect the removal of each other. The pseudo second-order kinetic model and Langmuir adsorption isotherm model were better to fit the experimental data, and the thermodynamic analyses indicated that the removal processes of BaP and Cr(VI) were spontaneous and exothermic. Besides, the quenching experiments yielded that SO4− and OH played a dominant role in BaP removal, and Cr(VI) removal mainly depended on the reduction of composites. This study expands the application of clay minerals in water treatment and suggests new strategies for simultaneous treatment of multiple pollutants in the environment.

Kinetic, equilibrium, and thermodynamic studies of adsorptive interactions of eosin-B on chemically treated orange peels

The present study investigated the adsorption of eosin B on the surface of powdered and chemically treated orange peels, along with this process’s condition optimizations, kinetics, and thermodynamics. The adsorbent dose (0.1–0.5 g), temperature (298, 303, 308, and 313 K), contact time (15–120 min), initial pH value (2–11) of the solution, and interfering salts (0.01 and 0.1 mol L−1) were all taken into consideration during the experiments. At all investigated temperatures and pH of 2, adsorption was more favourable. Although the Langmuir model might also represent the adsorption data, the Freundlich and Dubinin–Radushkevich (D–R) models provided a good description. The pseudo-second order kinetic model was followed during the adsorption process. The mechanics of the rate-controlling step were examined by applying the intra-particle diffusion-based mass transfer model to the experimental data. It was discovered that the only process that controlled the rate was intra-particle diffusion. The adsorption process appears to be spontaneous, and endothermic and involves van der Waals forces based on thermodynamic data.

323 Advances in using membrane vesicles for studying intestinal functions

Abstract Enterocytes are the major cell lineage of the small intestinal epithelia along the crypt-villus axis in gut mucosa. Enterocytes participate in the gut terminal nutrient digestion and absorption; and have essential roles in nutrient and metabolite recycling and efflux, nutrient and hormonal sensing, interactions with symbiotic microbiome and binding to infectious viruses, thus influencing the host homeostasis and whole-body physiological status. Intestinal membrane vesicles have been widely used for studying various gut functions in the past several decades. Villus enterocytic brush border membrane and the apical membrane vesicles along the crypt-villus axis in gut mucosa can be prepared and isolated by Mg2+- and Ca2+-precipitation and differential centrifugation procedures. Whereas, gut mucosal basolateral membrane vesicles can be prepared, fractionated and differentiated from other intracellular organelles such as the mitochondrial inner membrane by the Percoll gradient ultracentrifugation. Nutrient transport and exchange activities in the membrane vesicles in vitro are conducted often by rapid hand filtration, and in excess, in an automated fast sampling apparatus. Nutrient transport and exchange activity kinetics are derived according to the well-established classic Michaelis-Menten and the tracer inhibitory kinetic models with a simple linear diffusional component. Physiological and biochemical properties associated with various nutrient uptake systems such as pH optimum, requirements for co-transported ions (e.g., Na+, K+, Cl-), transporter affinity and substrate specificity can be effectively investigated in vitro with the membrane vesicles by altering the compositions of uptake buffers and intra-vesicular pre-loading buffers. Some of the fundamental gut functions are established via using the membrane vesicles in different mammalian species. And these include H+-peptide cotransport, Na+-cotransport and Na+-independent systems of hexose uptake across the apical membrane and the low-affinity Na+-independent hexose bidirectional uptake across the basolateral membrane that were characterized in rodents; Na+-dependent cotransport and Na+-independent systems of amino acid (AA) transport across the apical membrane that were revealed in rodents and pigs; as well as the Na+-hexose and AA cotransport and the co-expression of the coronavirus SARS-CoV-2 host epithelial apical membrane binding receptor, i.e., the angiotensin-converting enzyme-2 (ACE2), along the gut crypt-villus axis that were identified in liquid formula-fed piglets. In the post genomic and metagenomic sequencing era, further research efforts need to pursue understanding of expression and various functionality of the gut terminal hydrolases, nutrient transporters, nutrient exchangers, nutrient sensors, substrate and particle receptors, taste receptors, viral binding receptors such as ACE2 and hormonal receptors and their interactions with luminal factors such as nutrient, metabolites, symbiotic bacterial outer membrane vesicles etc., along the longitudinal and crypt-villus axes, through using the mammalian primary enterocytic apical and the basolateral membrane vesicles under various research settings.

Enhanced microplastics removal from sewage effluents via CTAB-modified magnetic biochar: Efficacy and environmental impact

Sewage treatment plants (STPs) are identified as a significant pathway of microplastics (MPs) re-entry into the environment through effluent discharge, thereby emphasizing the need for reliable and efficient treatment methods. This study investigated MPs removal from sewage effluents using cetyl trimethyl ammonium bromide (CTAB)-modified magnetic biochar (RH-MBC-CTAB) as an adsorbent. Biochars from different biomass were synthesized, surface modified, characterized, and compared for their MPs removal efficacy from aqueous matrices. Batch adsorption studies were initially conducted on synthetic water with 1 μm sized polystyrene (PS) MPs using different MP concentrations (1–10 mg/L) and varying adsorbent dosages (1–10 mg/50 mL) to assess the effect of different process parameters, viz. pH (2–10), humic acid (6–25 mg/L), and competitive ions (0.01–0.2 M). The maximum MPs removal (98%) was achieved at the favorable conditions: initial MPs concentration: 10 mg/L, RH-MBC-CTAB dose: 7 mg/50 mL, pH 4, mixing speed: 180 rpm, and contact time: 3 min. Electrostatic attraction and hydrogen bonding were likely to remove MPs while the MPs adsorption was best fitted by the pseudo-second-order kinetics model (R2 = 0.91) and Langmuir isotherm model (R2 = 0.94) with the maximum adsorption capacity of 247.52 mg/g. Further, the application of RH-MBC-CTAB on the real-time sewage effluents from sequencing batch reactor (SBR) and moving bed biofilm reactor (MBBR)-based STPs spiked with MPs showed up to 96% MPs removal. The reusability results revealed that developed RH-MBC-CTAB could maintain good stability for up to three reusability cycles, therefore offering extensive potential for the removal of MPs from sewage effluents.

3D carbon corrosion kinetic mechanism modeling study for proton exchange membrane fuel cells under localized flooding

Localized anode flooding often occurs in proton exchange membrane fuel cells (PEMFCs) during operation, which leads to localized H2 deficiency and triggers the carbon support corrosion in the catalyst layer, thus seriously weakening the performance and service life of PEMFCs. In this work, a 3D carbon corrosion kinetic mechanism model under localized anode flooding is developed to analyze in detail the multi-physics field distributions during carbon corrosion. The developed model is also coupled with a PEMFC performance model to focus on the carbon corrosion rate spatial distribution and its effect on the PEMFC performance. In addition, the effect of the cathode catalyst layer (CCL) added with oxygen evolution reaction (OER) catalyst on the carbon corrosion rate is analyzed in detail. Considering the particularly expensive OER catalysts and the non-uniform carbon corrosion distribution, a scheme of multi-area ordered adding with OER catalysts is further proposed to reduce the OER catalyst loading, and it is found that such a scheme can more effectively reduce the non-uniform carbon corrosion within the CCL. The electrochemical surface area loss is reduced by 7.38 % and the performance is improved by 5.69 % with scheme 2 compared to without the addition of OER catalyst.

Negative damping of terahertz plasmons in counter-streaming double-layer two-dimensional electron gases

Abstract The plasmon excitation in two-dimensional electron gases (2DEGs) is a significant way of achieving micro-nanoscale terahertz (THz) devices. Here, we establish a kinetic simulation model to study the THz plasmons amplification in a semiconductor double-quantum-well system with counter-streaming electron drift velocities. By comparing the simulation results with theoretical dispersion relations, we confirm two competing mechanisms of negative damping suitable for THz amplification: Cherenkov-type two-stream instability and a new non-Cherenkov mechanism called kinetic relaxation instability. The former is caused by the interlayer coupling of two slow plasmon modes and only exists when the drift velocities are much greater than the fermi velocities. The latter is a statistical effect caused by the momentum relaxation of electron-impurity scattering and predominates at lower drift velocities. We show that an approximate kinetic dispersion relation can accurately predict the wave growth rates of the two mechanisms. The results also indicate that the saturated plasmonic waves undergo strong nonlinearities such as wave distortion, frequency downshift, wave-packet formation, and spectrum broadening. The nonlinear evolution can be interpreted as the merging of bubble structures in the electron phase-space distribution. The present results not only reveal the potential mechanisms of the plasmonic instabilities in double-layer 2DEGs, but also provide a new guideline for the design of on-chip THz amplifiers.

General synthetic iterative scheme for rarefied gas mixture flows

The numerical simulation of rarefied gas mixtures with disparate mass and concentration is a huge research challenge. Based on our recent kinetic modeling for monatomic gas mixture flows, this problem is tackled by the general synthetic iterative scheme (GSIS), where the mesoscopic kinetic and macroscopic synthetic equations are alternately solved by the finite-volume discrete velocity method. Three important features of GSIS are highlighted. First, the synthetic equations are precisely derived from the kinetic equation, naturally reducing to the Navier-Stokes equations in the continuum flow regime; in other flow regimes, the kinetic equation provides high-order closure of the constitutive relations to capture the rarefaction effects. Second, these synthetic equations, which can be solved quickly, help to adjust the kinetic system to relax rapidly toward the steady state. Furthermore, in such a two-way coupling, the constraint on the spatial cell size is relieved. Third, the linear Fourier stability analysis demonstrates that the error decay rate in GSIS is smaller than 0.5 for various combinations of mass, concentration and viscosity ratios, such that the error can be reduced by three orders of magnitude after 10 iterations. The efficiency and accuracy of GSIS are demonstrated through several challenging cases covering a wide range of mass ratio, species concentration, and flow speed.

Quantification of competitive adsorptions between sulfur and olefinic model compounds representative of a FCC gasoline over a CoMoS/Al2O3 catalyst: Theoretical and experimental approaches

The reinforcement of regulations for the production of cleaner fuels along with the larger demand for energy urge us to optimize the HDS processes. The transformation of various olefins alone and in mixture with sulfur compounds was investigated over a CoMoS/Al2O3 catalyst under HDS of FCC gasoline operating conditions. A reactivity scale was established with hex-1-ene being more reactive than 4methylpent-1-en was more reactive than 4-methylpent-1-ene, 3,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene. The transformation of these olefins involves two main reactions ie isomerization and hydrogenation. In the presence of sulfur compounds (3-methythiophene and benzothiophene), a mutual inhibiting effect was observed with benzothiophene 3,3- dimethylbut-1-ene being respectively the most inhibiting sulfur and olefin compounds. These results were explained with a unique kinetic model from which the adsorption constants calculated were the highest for benzothiophene and 3,3-dimethylbut-1-ene.

Acid precipitation-hydrothermal synthesis of needle-like hydroxyapatite for protein adsorption from waste phosphogypsum

ABSTRACT In order to promote the high-value utilization of waste phosphogypsum (PG), hydroxyapatite was directly synthesized from PG by acid precipitation-hydrothermal method (PGHAP), which was used for the adsorption of bovine serum albumin (BSA) and lysozyme (LYS). The synthesized PGHAP was characterized by XRD, SEM, FTIR and BET, and the effects of various factors on protein adsorption capacity were studied. The results showed that PGHAP exhibits a clear needle-like morphology, high crystallinity, and an average size of about 200 nm. The pH had the greatest effect on the adsorption of protein, and the highest adsorption capacity was obtained at pH 4.0. In addition, the adsorption mechanism of protein on PGHAP was explored by adsorption kinetics and adsorption isotherm. The adsorption of protein on PGHAP conforms to the Intra-particle diffusion model kinetic model, the maximum adsorption capacity of protein on PGHAP can reach 31 mg/g, which is comparable to other adsorbents in this field. In addition, the adsorption behaviour of PGHAP on protein is more appropriately described by Langmuir isotherm model, which indicates that the binding site with uniform energy on the surface of PGHAP realizes the monolayer adsorption of protein. The main adsorption mechanisms are ion exchange, co-precipitation, complexation reaction and so on. Therefore, the needle-like PGHAP synthesized from waste PG is a protein adsorbent with industrial application potential.

Chloride-mediated transformation of sulfate radicals to hydroxyl radicals for enhanced contaminant degradation in high-temperature wastewater

Using the excess heat in high-temperature industrial wastewater to activate oxidant precursors for organic contaminant degradation would make advanced oxidation processes more sustainable in the context of carbon neutrality, while the salt-mediated radical transformation chemistry in such wastewater is poorly understood. We herein demonstrate that chloride (Cl–) in the range of 0.28–56.34 mM accelerates the degradation of organic contaminants in the heat activated persulfate process in both synthetic and authentic wastewater. We use laser flash photolysis technique together with kinetic modeling to directly determine the bimolecular rate constants of radical–radical (e.g., kSO4·--SO4·- = 2.50 × 109 M−1 s−1), Cl–-radical (e.g., kSO4·--Cl- = 3.75 × 108 M−1 s−1), and radical-contaminant (e.g., kHO·-BA = 1.02 × 1010 M−1 s−1) reactions at 55 °C, which are substantially higher than those at ambient water temperature (25 °C). We also combine experimental and modelling results to calculate the contribution of different radicals to contaminant removal at 55 °C. The results clearly demonstrate that Cl– in the range of 0.28–56.34 mM promotes the transformation of SO4– to HO at 55 °C, with reactive chlorine species involved as the intermediates. The findings improve fundamental understanding of Cl–-mediated radical chemistry in high-temperature water and provide an engineering strategy to recycle the heat in wastewater to enhance contaminant remediation.

Enabling highly efficient navy-blue dye degradation over the LaFeO3/B-g-C3N4/WO3 double z-scheme heterostructure

Chemical reactivity, optical and electronic features of conventional photocatalysts can be improved by chemical modification and nanocomposites fabrication techniques. Herein, a double Z-scheme LaFeO3/B-g-C3N4/WO3 (LFO/B-CN/WO) heterostructure nanocomposite has been successfully fabricated via a hydrothermal approach. XRD, FT-IR, SEM/EDS, TEM, TGA/DSC, and UV–visible spectroscopy confirmed crystallographic planes, phase purity, and heterojunction between LFO, WO and B-CN. From UV visible absorption spectroscopy, it was confirmed that optical band gap energy of CN is remarkably reduced after boron doping. The LFO/B-CN/WO photocatalyst revealed 96 % degradation performance for Navy Blue (NB) dye after visible light irradiation for 130 min under neutral pH conditions. The data were analyzed using pseudo-first and pseudo-second order kinetics models to evaluate the dye degradation kinetics. Compared to the CN, B-CN, LFO-CN and WO-CN photocatalysts, the performance of LFO/B-CN/WO was much significant. Improved light absorption capability, effective spatial separation and prolonged charge-carrying capacity of the double Z-scheme system resulted in enhanced photocatalytic performance. This study offers new insights into the design and synthesis of highly efficient Z-scheme heterojunction photocatalysts for environmental decontamination and clean energy purposes.

Insights into transition metal encapsulated inside carbon aerogel for accelerated electro-peroxone oxidation: Activity evaluation and reactive oxygen species generation

Transition metals have critical influences on the generation of reactive oxygen species in activating O3 and H2O2, as the binary oxidant sources in electro-peroxone (EP). To evaluate the catalytic activity of different metals and reveal the reactive oxygen species generation in heterogeneous EP, series of metals encapsulated inside carbon aerogel spheres (M@CS, M=Fe, Co, Ni, Zn) were fabricated for strengthening EP. Atrazine was used as model pollutant due to its low reactivity with O3, and the abatement trends followed Co@CS > Fe@CS > Ni@CS > Zn@CS. Co@CS exhibited the superior catalytic activity with maximum metal active site utilization (1.28 × 103 min-1 mol-1 per mole Co atom sites at pH 7) and minimum electric energy consumption (0.106 kWh/m3-log). The catalytic activity of M@CS was related to the adsorption energies for O3 and H2O2 (Fe@CS > Co@CS > Ni@CS > Zn@CS) and the graphitization degree (Co@CS > Fe@CS > Ni@CS > Zn@CS). Verified by theoretical calculation and in-situ Fourier transformed infrared, the metal effectively promoted the adsorption and decomposition of O3 and H2O2 into the surface oxygen intermediates, finally generating ·OH/·O2-/1O2. The carbon layer was conducive to the reduction of internal metal, ensuring catalyst durability. Electronic paramagnetic resonance and kinetic model revealed the occurrence, ratio and transient concentration of ·OH/·O2-/1O2 in M@CS/EP. M@CS/EP showed good performance for pollutant removal in coexistence of anions, humic acid and real water. This study provides guidance for selecting the metal–carbon catalyst in heterogeneous EP.

Removal of hexavalent chromium using activated and magnetic Ziziphus Jujube seed biochar — a column study

ABSTRACT In this study, activated and magnetic biochar prepared from Ziziphus Jujube Seeds (ZJS) is used to remove Hexavalent Chromium (Cr(VI)) using Fixed Bed Column Experiment. Physicochemical characteristics of the activated and magnetic biochar such as functional groups, surface area, morphological study, and magnetic properties were analyzed. The column experiment was carried out for varying bed heights (2, 4, 6, 8, 10 cm), flow rates (20, 30 ml/min), and initial chromium concentrations (40, 60, 80 ppm) to determine adsorption performance of the studied biochar. The characteristic study found that magnetic biochar (MB) has good magnetic properties and crystallinity nature with essential functional groups such as C-O, FeO. The study found that Magnetic Biochar (MB) effectively removed 99% of hexavalent chromium through column adsorption under optimal conditions, including bed height of 6 cm, 60ppm Chromium concentration, and flow rate of 20 ml/min. Kinetic model study showed that Magnetic Biochar (MB) showed very good agreement with Adam Bohart Model, with R2 of 0.97, which is best fit model than other model studies whereas the other model showed a lesser R2 value. The study reveals that magnetic biochar from Ziziphus Jujube Seed is optimal adsorbent for removal of Cr(VI) through column adsorption experiment.

Synthesis of ZIF-8/chitosan composites for Cu2+ removal from water

ABSTRACT In this work, a kind of novel Chitosan (Cs)-doped zeolite imidazole framework (ZIF-8@Cs) with a larger surface area and a smaller pore size was synthesised via a facial solvothermal approach and applied to remove Cu2+ from mine wastewater. Compared to nondoped ZIF-8, ZIF-8@Cs exhibited a stronger adsorption performance and removal efficiency. The reason was that ZIF-8@Cs doped by the Cs could suppress the aggregation and increase the monodispersity of ZIF-8. Using the high-performance ZIF-8@Cs, as a novel adsorbent, was successfully developed for the efficient removal of Cu2+ from mine wastewater. Various parameters, such as contact time, initial Cu2+ concentration, adsorbent dosage, and pH, were investigated. The results showed that a removal efficiency of 85% was obtained at 4 h contact time for a Cu2+ concentration of 30 mg/L at the optimum pH of 6.0. Equilibrium data were analysed using different isothermal models and kinetic models, analytic results indicated that the capture of Cu2+ by ZIF-8@Cs could favourably comply with the pseudo-first-order kinetic model and Langmuir isotherm model. The single-layer adsorption of Cu2+ on ZIF-8@Cs was dominated by diffusional mass transfer. Additionally, the results of the thermodynamic analysis indicated that the adsorption of Cu2+ by ZIF-8/Cs was a spontaneous, exothermic, and ordered process. Overall, the results reported herein indicated that ZIF-8/Cs with high adsorption efficiency are very attractive and imply a potential practical application for the removal of potentially toxic elements in wastewater.