Langmuir-Hinshelwood Kinetic Model Research Articles

Introduction of Fe on rGO/TiO2 improves styrene visible light-driven photocatalytic oxidation: Characterization, stability, kinetics, and mechanism

Photocatalytic process is a preferable strategy for air pollutant removal due to its high efficiency and mild operating condition. In this study, co-doping of reduced graphene oxide (rGO) and Fe were performed on TiO2 to enhance styrene removal. Addition of 0.1 wt% rGO promoted the photocatalytic activity of TiO2 and further improvement was achieved by introduction of Fe. The best photocatalytic activity was achieved by 0.1 wt%rGO/Fe0.5%/TiO2 which might be carried out by changes in reduction of band gap and electron-hole pair recombination rate. This result was also proven by the characterization analyses along with the detection of OH radicals which played an important role in the photocatalytic degradation of styrene. 1 % relative humidity accelerated photocatalytic degradation of styrene due to supply of OH radical species, however, excess amount of water vapor led to declining of photocatalytic activity due to adsorption competition on active sites. Furthermore, kinetics study using Langmuir Hinshelwood kinetics model 4 performed the best fitting with experimental data and proposed photocatalytic reaction mechanism was also built from analysis of generated intermediates.

Feasibility of reactive chromatography for the production of 2‐phenyl ethyl acetate

AbstractReactive chromatography is a novel process intensification option when the progress of a reaction is hampered by reversibility (e.g., esterification and acetalization). In this work, we study its feasibility for the production of 2‐phenyl ethyl acetate (PEAct) by esterification of 2‐phenyl ethyl alcohol with acetic acid using Amberlyst‐15 as a catalyst/adsorbent. The reaction kinetics is investigated in a laboratory batch reactor by varying various parameters such as agitation speed, temperature, feed molar ratio, catalyst loading, and particle size, and a Langmuir Hinshelwood kinetic model is proposed. The reaction is then studied in a fixed‐bed chromatographic reactor (FBCR). Non‐reactive binary adsorption experiments are performed in the same setup to estimate the corresponding parameters of the Langmuir adsorption isotherm. The experimentally observed reactive breakthrough curves in FBCR reveal that RC is a promising process option for the production of PEAct. Furthermore, it is shown that the FBCR model, which uses kinetics and isotherms developed in this work, explains the reactive breakthrough curves and the regeneration performance reasonably well. The work reported here forms a base for the design of a simulated moving‐bed reactor that may be used for large‐scale production.

Photo-enhanced catalytic hydrogen production from ammonia borane dehydrogenation over cobalt doped n-type semiconductors

Aimed at achieving the photo-enhanced dehydrogenation of ammonia borane (NH3BH3) in aqueous solutions, p-type cobalt (Co) doped n-type semiconductors (TiO2, WO3 and TiO2-WO3) based heterojunction structures were proposed for hydrogen production. In the present study, the Co doped n-type semiconductors such as titanium dioxide (TiO2) and tungsten oxide (WO3) were synthesized by hydrothermal synthesis to obtain heterojunction structure and characterized by XRD, SEM/EDS, TEM, FT-IR and UV–Vis techniques. The photo-enhanced catalytic hydrogen production from NH3BH3 dehydrogenation over Co doped n-type semiconductors were tested under light-irradiation (UV-light and day-light) in presence of organic and inorganic scavengers. The experimental results showed that Co @TiO2-WO3 heterojunction structure improved hydrogen production almost three times in terms of TOF values (821 h−1) compared to Co@TiO2 (292 h−1) due to photoelectrons and hole pairs increases activity. The pseudo first order kinetics based on Langmuir-Hinshelwood (L-H) kinetic model fitting revealed that apparent adsorption constant calculated in presence of Co@TiO2-WO3 with lowest value as 4.99 h−1 and 9.75 h−1 for both region, respectively.

Novel ZnO-biochar nanocomposites obtained by hydrothermal method in extracts of Ulva lactuca collected from Black Sea

The aqueous extract of Ulva lactuca, obtained from algae waste, has been used both as precursor for nanobiochar and source of phycocolloids, for obtaining of ZnO@C composites by hydrothermal method, through two synthesis routes, and capped ZnO nanopowders. The nanomaterials were characterized by XRD, SEM, thermal analysis, UV–vis, PL and FTIR spectroscopy. The presence of ZnO with hexagonal wurtzite structure was confirmed by XRD, while the presence of biochar and capping molecules was confirmed by FTIR spectroscopy and thermal analysis correlated with the total organic carbon determination. The band gap energy was calculated from diffuse reflectance spectra. The photocatalytic properties were tested in the degradation of Congo red azo dye under UV and visible light irradiations, the prepared zinc oxide-biochair nanocomposites demonstrating a good photocatalytic activity, superior to the pristine ZnO nanopowders obtained in similar conditions. The results confirmed a good fit with the Langmuir–Hinshelwood kinetic model. A correlation between photoluminescent and photocatalytic properties of nanomaterials was done. The properties of ZnO@C nanocomposites depended on the synthesis route were compared with those of capped and pristine ZnO samples.

Visible light degradation of ibuprofen using PANI coated WO3@TiO2 photocatalyst

A PANI-coated heterojunction of WO3@TiO2 nanocomposite was fabricated in three stages. The performance evaluation of the prepared photocatalyst for the degradation of ibuprofen was performed under visible light. Characterization of the photocatalyst using X-ray diffraction (XRD) analysis showed that the TiO2 prepared constituted of the anatase phase. Furthermore, results from in situ XRD analysis of WO3 show that it consisted of monoclinic and orthorhombic crystalline structures. These phases were not affected by the incorporation of PANI as revealed by XRD analysis. Results from Transmission electron microscopy (TEM) examination showed that sphere-like WO3 and TiO2 nanorods of different sizes were prepared In addition, fabrication of a heterojunction of WO3@TiO2 wrapped in PANI was shown by TEM analysis. Results from photoluminescence studies indicate that coupling TiO2 with WO3 enhanced the charge separation and the degradation performance of the nanocomposite. Supporting the heterojunction on PANI enhanced the degradation efficiency as indicated during the performance evaluation process. Diffuse reflectance spectra (DRS) calculations of the PANI/WO3@TiO2 catalysts showed that they can be used under visible light. The experimental results of X-ray Photon Spectroscopy (XPS) analysis showed the presence of elements W, C, O, Ti, and N. Solution pH influenced the degradation process and the maximum degradation efficiency was attained at pH 9. The degradation followed the Langmuir-Hinshelwood kinetic model with a Kinetic constant of 3.5 × 10−2. The rate of degradation increased in the presence of bicarbonate/carbonate ions and persulfate ions.

Structural and Photocatalytic Studies on Oxygen Hyperstoichiometric Titanium-Substituted Strontium Ferrite Nanoparticles

Doping of ferrites is an important domain of research for their application as photocatalysts. In the present work, the effect of Ti4+ substitution on the structural and photocatalytic properties of strontium ferrite nanoparticles (NPs) is studied. Ternary doped Sr1−xTixFe2O4+δ ferrite NPs (x = 0.0–1.0) were synthesized by sol–gel methodology. Tetravalent Ti4+ ions caused oxygen hyperstoichiometry and enhancement in the surface area from 44.3 m2/g for SrFe2O4 NPs to 77.6 m2/g for Sr0.4Ti0.6Fe2O4+δ NPs. The average diameter of NPs ranged between 25–35 nm as revealed by TEM analysis. The presence of two sextets in the Mössbauer spectrum of pristine SrFe2O4 and Ti4+-substituted ferrite NPs and a paramagnetic doublet in the TiFe2O5 confirmed their phase purity. The photocatalytic potential of pure and Ti4+-substituted ferrite NPs was studied using nitroaromatic compounds, viz. pendimethalin, p-nitrophenol and Martius yellow, as model pollutants. Doped ferrite NPs with a composition of Sr0.4Ti0.6Fe2O4+δ NPs showed the highest degradation efficiency ranging from 87.2% to 94.4%. The increased photocatalytic potential was ascribed to the lowering of band gap (Eg) from 2.45 eV to 2.18 eV, a fourfold decrease in photoluminescence intensity, increased charge carrier concentration (4.90 × 1015 cm−3 to 6.96 × 1015 cm−3), and decreased barrier height from 1.20 to 1.02 eV. O2●− radicals appeared to be the main reactive oxygen species involved in photodegradation. The apparent rate constant values using the Langmuir–Hinshelwood kinetic model were 1.9 × 10−2 min−1, 2.3 × 10−2 min−1 and 1.3 × 10−2 min−1 for p-nitrophenol, pendimethalin and Martius yellow, respectively. Thus, tuning the Ti4+ content in strontium ferrite NPs proved to be an effective strategy in improving their photocatalytic potential for the degradation of nitroaromatic pollutants.

A comprehensive evaluation of the integrated photocatalytic-fixed bed bioreactor system for the treatment of Acid Blue 113 dye

This work investigated the performance of the integrated system (i.e., a Photocatalytic reactor followed by a Fixed bed bioreactor (PC-FBR)) for the degradation of complex Acid Blue 113 from wastewater. Initially, a Photocatalytic reactor was employed to improve the biodegradability index (i.e., BOD/COD) of wastewater from 0.21 ± 0.0062 to 0.395 ± 0.0058. The preliminary photocatalytic oxidation study revealed a maximum of 86.42 ± 0.33 % dye removal at TiO2 loading of 1.5 g/L and an initial concentration of 50 mg/L of AB 113. An integrated reactor system significantly achieved a maximum of 92 ± 2.6 % of dye removal efficiency under a retention time of 120 hr. The stand-alone FBR dye shock loading study suggested that the reactor system was reasonably able to further restore its degradation efficiency. Langmuir–Hinshelwood kinetic model, Monod model, and Andrew-Haldane model were fitted. The bacterial toxicity assessment was carried out using the Pseudomonas fluorescens.

Exploring the Effect of Hierarchical Porosity in BEA Zeolite in Friedel-Crafts Acylation of Furan and Benzofuran

Hierarchical BEA zeolite was prepared through desilication or desilication followed by acid treatment. The catalytic performance of BEA zeolite samples was evaluated using Friedel-Crafts acylations with two substrates of different molecular sizes, furan (5.7 Å) and benzofuran (6.9 Å), in the presence of acetic anhydride as acylating agent. The application of the simplified Langmuir-Hinshelwood kinetic model showed that the size of the substrate leads to different catalytic activities, with improved rate constant and turnover frequency (TOF) solely in the presence of benzofuran for both desilicated and further acid treated samples. The mesopores developed during the zeolite treatments have an important role as transportation channels by reducing diffusion limitations. The application of Quantitative Structure–Property Relationships (QSPR) allowed the finding of the most relevant properties of the zeolite and substrate with impact on the catalytic parameters.

Enhancing the oxidation efficiency of elemental mercury in the presence of NO and SO2 by using Cu(II)O doped TiO2 photothermal catalysts: Kinetics and mechanisms

This study aimed to apply sol–gel synthesized Cu(II)O doped TiO2 to enhance the oxidation of gaseous elemental mercury (Hg0) in the flue gases containing NO and SO2 at the temperatures of 120-180℃ under the irradiation of near-ultraviolet (near-UV). The influences of SO2 and NO on the oxidation efficiency of Hg0 were investigated by in-situ diffuse reflection infrared spectroscopy (DRIFT) and density functional theory (DFT). Experimental results showed that an optimal 5 %Cu(II)O/TiO2 had the oxidation efficiencies of Hg0 from 40 to 100 % at 120-180℃. The oxidation efficiencies of Hg0 were 85 and 70 % at 120℃, and 40 and 5 % at 180 °C, in the presence of solely SO2 and NO, respectively. Surface characterization showed that Cu(II)O was evenly dispersed over the surface of TiO2 catalysts. NO could inhibit the oxidation of Hg0 since it consumed the chemisorbed oxygen (Oα) and compete with Hg0 at the surface active sites. In contrast, SO2 could promote the oxidation efficiency of Hg0 due to the formation of HgSO4 on the surface of Cu(II)O/TiO2 catalysts. In the exposure of NO/SO2, NO and SO2 can be adsorbed on the catalyst surface reacting with ̇OH. The photothermal oxidation reactivity of Hg0 was inhibited due to the competitive adsorption between NO/SO2 and Hg0. The Langmuir-Hinshelwood (L-H) kinetic model successfully simulated the oxidation rate of Hg0. Moreover, DFT was further applied to estimate the binding energies of different gas molecules confirming the competence for active sites on the surface of Cu(II)O/TiO2 between NO/SO2 and Hg0.

Reaction Kinetics of Cinnamaldehyde Hydrogenation over Pt/SiO2: Comparison between Bulk and Intraparticle Diffusion Models

The liquid-phase hydrogenation of cinnamaldehyde over a Pt/SiO2 catalyst was investigated experimentally and theoretically. The experiments were conducted in a 300 cm3 stainless steel stirred batch reactor supplied with hydrogen gas and ethanol as a solvent. Five Langmuir–Hinshelwood kinetic models were investigated to fit the experimental data. The predictions from the bulk model were compared with predictions from the intraparticle diffusion model. Competitive and non-competitive mechanisms were applied to produce the main intermediate compound, cinnamyl alcohol. Reaction rate parameters for the different reaction steps were calculated by comparing between the experimental and mathematical models. All rate data utilized in the present study were obtained in the kinetic regime. The kinetic parameters were obtained by applying a nonlinear dynamic optimization algorithm. Nevertheless, the comparison between the methodology of the present model and these five models indicated that the non-competitive mechanism is more acceptable and identical with the single-site Langmuir–Hinshelwood kinetic model including mass transfer effects and it mimicked the reactant behavior better than the other models. In addition, the observed mean absolute error (MAE) for the non-competitive mechanism of the present model was 2.3022 mol/m3; however, the MAE for the competitive mechanism was 2.8233 mol/m3, which is an increase of approximately 18%. The prediction of the intraparticle diffusion model was found to be very close to that of the bulk model owing to the use of a catalyst with a very small particle size (<40 microns). Employing a commercial 5% Pt/SiO2 catalyst showed a result consistent with previous research using different catalysts, with an activation energy of ≈24 kJ/mol.

Degradation of Amido Black Dye Using Ultra-Violet Light Catalyzed by Iron Oxide Nanoparticles: Kinetics and Mechanism of Degradation

In this study, we investigated the degradation of amido black dye in an aqueous solution using ultra-violet (UV) light catalyzed by iron oxide nanoparticles (nano-Fe). The nano-Fe was synthesized by sodium borohydride reduction of ferric chloride solution and was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence spectrophotometry (XRF). The SEM of the nano-Fe showed regular spherical particles, the XRD examination showed a weak and broad peak at Fe (1 1 0), and the XRF study showed that the element with the highest composition was Fe2O3 (60.80%). The degradation experiments showed that the UV light catalyzed by nano-Fe could effectively degrade amido black dye. The nano-Fe/UV system could degrade 5 mg/L of amido black dye up to 93.2% at 254 nm after being irradiated for 60 min. The nano-Fe/UV system could be described by the Langmuir–Hinshelwood kinetic model, and the rate constants (kapp) were 0.0183–0.0323 min−1. Thus, UV light combined with nano-Fe can be applied for the efficient remediation of dye wastewater.

Flower-like hierarchical Sn3O4/montmorillonite nanostructure for the enhanced microwave-induced degradation of rhodamine B

A flower-like hierarchical nanostructure of Sn3O4/montmorillonite is first reported in this work. The nanomaterial was prepared by a one-pot hydrothermal synthesis method using tin chloride as the precursor, and the physicochemical characteristics of the material were examined by instrumental analyses. The prepared nanostructure was evaluated as a catalyst in the microwave-induced removal of rhodamine B (RhB). The influences of Sn content, oxidant, time of irradiation, and initial concentration of RhB were investigated. The results showed homogeneously dispersed Sn3O4 in a montmorillonite support with a cubic phase, and crystallite size smaller than to Sn3O4 was obtained. XPS investigation revealed the Sn3O4 phase, which is consistent with the band gap energy of 2.75 eV from UV-DRS measurements. The homogeneous distribution of the Sn3O4 nanoparticles influenced the increasing specific surface area of the nanocomposite compared to montmorillonite. The enhanced physicochemical properties significantly enhanced the catalytic activity in microwave induced RhB oxidation, with the degradation efficiency reaching 99.9% after 20 min of treatment. The kinetics of catalytic oxidation were best fitted to the pseudo-second-order equation and obeyed the Langmuir-Hinshelwood kinetics model. Furthermore, the catalytic oxidation condition optimization using a Box-Behnken Design revealed the contribution of oxidant, pH and catalyst dose as influencing factors for the efficiency.

Photolytic and photocatalytic removal of a mixture of four veterinary antibiotics

The removal of a mixture of four veterinary antibiotics (VA) – tetracycline (TET), ciprofloxacin (CIP), sulfadiazine (SDZ) and sulfamethoxazole (SMX) – via photo-degradation (UVC) and photocatalysis with TiO2 (UVC/TiO2) was investigated in a batch reactor under different initial concentrations (20, 100, 500 and 1000 μg/L per antibiotic). Ultra-high performance liquid chromatography coupled to a mass spectrometry (UHPLC-MS/MS) was used to determine the removal of these veterinary antibiotics. The removal of all antibiotics via photolysis was around 98–99% after 100 h for TET, 122 h for CIP, 212 h for SDZ and 240 h for SMX. Nevertheless, the removal of all antibiotics via photocatalysis was around 99–100% after 4.2 h for TET, 3.5 h for CIP, 7.1 h for SDZ and 16.5 h for SMX. The photolysis for the four veterinary antibiotics followed a first-order irreversible kinetic model. The photocatalysis of TET, CIP and SDZ followed a Langmuir-Hinshelwood kinetic model, and adsorption was considered the limiting step. SMX followed a first-order irreversible kinetic model. The photolytic degradation rate constant (k1) was 0.00073 min−1 for TET, 0.00055 min−1 for CIP, 0.00031 min−1 for SDZ and 0.00027 min−1 for SMX. While for photocatalysis k1 was 0.0044 min−1 for SMX; kL-H was 0.0284 min−1 for TET, 0.0379 min−1 for CIP and 0.0141 min−1 for SDZ. The VA degradation was enhanced by the use of a catalyst. Additionally, electrical energy per order (EEO) was assessed to estimate the electrical energy efficiency of each process. EEO values for photolysis were 339.06 kWh/m3/order for TET, 449.84 kWh/m3/order for CIP, 795.31 kWh/m3/order for SDZ and 897.71 kWh/m3/order for SMX. On the other hand, EEO values for photocatalysis were 14.96 kWh/m3/order for TET, 12.07 kWh/m3/order for CIP, 20.39 kWh/m3/order for SDZ and 62.10 kWh/m3/order for SMX. The energy consumption for photocatalysis was considerably lower than for photolysis. This study determined an overall degradation rate constant for a wide range of TET, CIP, SDZ and SMX concentrations. Furthermore, when working with a pH of 8 (a typical pH from wastewater from livestock farms) and a VA mixture whose concentrations resemble the characteristics of real water samples, that photolysis and photocatalysis are potential processes for wastewater treatment with low energy consumption.

Solar Light-Assisted Oxidative Degradation of Ciprofloxacin in Aqueous Solution by Iron(III) Chelated Cross-Linked Chitosan Immobilized on a Glass Plate

The massive worldwide use of antibiotics leads to water pollution and increasing microbial resistance. Hence, the removal of antibiotic residues is a key issue in water remediation. Here, we report the solar light-assisted oxidative degradation of ciprofloxacin (CPF), using H2O2 in aqueous solution, catalyzed by iron(III) chelated cross-linked chitosan (FeIII-CS-GLA) immobilized on a glass plate. The FeIII-CS-GLA catalyst was characterized by FTIR and 57Fe-Mössbauer spectroscopies as well as X-ray diffraction, revealing key structural motifs and a high-spin ferric character of the metal. Catalytic degradation of CPF was investigated as a function of solar light irradiation time, solution pH, concentration of H2O2 and CPF, as well as cross-linker dosage and iron(III) content in FeIII-CS-GLA. The system was found to serve as an efficient catalyst with maximum CPF degradation at pH 3. The specific ·OH scavenger mannitol significantly reduces the degradation rate, indicating that hydroxyl radicals play a key role. The mechanism of catalytic CPF degradation was evaluated in terms of pseudo-first-order and Langmuir-Hinshelwood kinetic models; adsorption of CPF onto the FeIII-CS-GLA surface was evidenced by field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. FeIII-CS-GLA can be reused multiple times with only minor loss of catalytic efficiency. Antimicrobial activity tests performed against both Gram-negative (Escherichia coli DH5α, Salmonella typhi AF4500) and Gram-positive bacteria (Bacillus subtilis RBW) before and after treatment confirmed complete degradation of CPF. These results establish the immobilized FeIII-CS-GLA as a rugged catalyst system for efficient photo-Fenton type degradation of antibiotics in aqueous solutions.

Photodegradation of tetracycline by asymmetrical zinc(II)phthalocyanines conjugated to cobalt tungstate nanoparticles

This work focused on syntheses of novel asymmetrically tetra substituted Zn phthalocyanines (ZnPc) each containing a single carboxyl group, with the other substituents bearing alkynyl (complex 1) and fluorine containing groups (complexes 2 and 3). The complexes were conjugated to cobalt tungstate nanoparticles and employed as efficient photocatalysts for degradation of tetracycline in water. ZnPc complexes and their conjugates showed good photophysical and photochemical properties behaviour with complex 1 giving higher triplet and singlet oxygen quantum yields compared to 2 and 3. Complex 1 showed higher activity towards the photodegradation of tetracycline compared to complexes 2 and 3, with higher kobs and initial rates for the former. The photocatalysis obeyed the Langmuir-Hinshelwood kinetic model.

Syngas analysis by hybrid modeling of sewage sludge gasification in downdraft reactor: Validation and optimization

In general, sewage sludge obtained from the municipal wastewater treatment plant is one of the significant sources of waste for renewable energy production. In this article, the thermochemical conversion of sewage sludge through a downdraft gasifier is addressed. Two-zone equilibrium and one-zone kinetic model as the hybrid modeling of the sewage sludge gasification is proposed. Three zones of drying & pyrolysis, oxidation, and (char) reduction are modeled by using an integrated thermodynamic stoichiometric equilibrium and Langmuir-Hinshelwood kinetic model. Through the validation and sensitivity analysis, the syngas compositions and cold gas efficiency show to be sensitive to the variations of inlet flow rates of gasifying agents (air and steam), the inlet flow rate of feedstock (sewage sludge), and the temperature and pressure of the gasifier. Through the response surface methodology-based optimization algorithm, the proper operating conditions of the process can be found under the prescribed operating constraints.

In vitro photoinactivation of S. aureus and photocatalytic degradation of tetracycline by novel phthalocyanine-graphene quantum dots nano-assemblies

A novel asymmetrical zinc (II) phthalocyanine (Pc) 4 bearing three dimethoxy groups and one carboxyl group was linked to glutathione capped graphene quantum dots (GQDs) by the reaction of carboxylic acid substituent on Pc 4 with the amino group on the GQDs. On the other side, the symmetrical Pc analog 3 was linked to the same nanoparticles through π-π interactions. The as-formed nano-photosensitizers were fully characterized by spectroscopic methods and their photophysicochemical properties were investigated as well. Photodynamic antimicrobial chemotherapy was performed on the planktonic cells of S. aureus strain. And the results show that these nano assemblies were able to completely inhibit the metabolic activity of the resistant bacteria strain S. aureus with a 10.26 log reduction in the viable count. Again, asymmetrical Pc showed higher photocatalytic activity compared to the symmetrical complex with higher kobs and fast initial rates for the former. The photocatalysis obeyed the Langmuir-Hinshelwood kinetic model. The target conjugates showed all the advantages of two different groups existing on a single entity.

Aegle marmelos Leaf Extract Based Synthesis of Nanoiron and Nanoiron+Au Particles for Degradation of Methylene Blue

Abstract In this study, nanoiron and nanoiron+Au particles were synthesised using aqueous Aegle marmelos extract using a facile and one-pot approach. Lower size non-magnetic nanoiron (~34 nm) and nanoiron (~34 nm) +Au particles (1 to 1.5 µm) were produced from the same medium individually. Nanoparticles suspension behaviour and structural characterisations were carried out by UV-Vis spectroscopy, electron microscopy and by X-ray diffraction techniques. Primarily, for synthesis, a simple bioreduction approach generated amorphous nanoiron particles, which on annealing produced magnetic maghemite, γ-Fe2O3 type nanoparticles with sizes 100 to 1000 nm. Posteriorly, the bioreduction process also produces nanoiron+Au particles and can be used for multifunctional applications. As a model application, catalytic application of the as-prepared nanoiron and nanoiron+Au particles towards methylene blue, a thiazine dye degradation is investigated and found to be effective within 20 min. Langmuir-Hinshelwood kinetic model was exploited to know the degradation behaviour, and the model was found to be fit based on R 2 values with the observed experimental data. We suggest that the formed highly stable nanoiron particles with in situ stabilisation offer benefits like consistency, environmental friendliness and suits well for large-scale applicability.

A comparative study of kinetics of methylene blue dye using adsorbent andisol and humic acid from lighnite by KOH-hydrothermal method

A comparative study of adsorption kinetics model of methylene blue (MB) dye using andisol and humic acid (HA) adsorbents from the isolation of lignite with KOH-Hydrothermal has been carried out. The adsorption process was measured by using a UV-Vis Spectrophotometer to determine concentration of the adsorbed MB. The adsorption kinetics was determined using the first-order Langmuir-Hinshelwood kinetic model, the first-order kinetic model of Lagergren (1898), and the pseudo-second-order kinetic model of McKay and Ho. The adsorption kinetic model of MB on andisol and HA followed second-order kinetic model of McKay and Ho, with the reaction rate constant for MB adsorption on andisol higher than the rate constant for MB adsorption on HA. The reaction rate constant for MB adsorption on andisol was 0.0532 g mg−1 minute−1 and the adsorption capacity was 18.9753 mg/gr, while the reaction rate constant for MB adsorption on andisol was 0.0241 g mg−1 minute−1 and the adsorption capacity was 19.7628 mg/gr.

Highly dispersed and stable Fe species supported on active carbon for enhanced degradation of rhodamine B through peroxymonosulfate activation: Mechanism analysis, response surface modeling and kinetic study

Herein, highly dispersed Fe species supported on activated carbon (CA-Fe-C) was fabricated with the aid of citric acid, showing excellent catalytic performance and stability for the degradation of rhodamine B (RhB) through peroxymonosulfate (PMS) activation. The radical quenching study, electron paramagnetic resonance (EPR) measurement and PMS consumption analysis confirmed the RhB degradation mechanism involving reactive radical species attacking RhB and non-radical oxidation pathway. The main degradation intermediates were identified by LC-MS, and the possible RhB degradation pathways were deduced. A multivariate quadratic polynomial model was developed using the response surface methodology (RSM) to examine how the removal of RhB was influenced by several quantifiable factors, with the objective of optimizing RhB removal. The analysis of variance (ANOVA) was used to evaluate the adequacy and significance of the proposed model. The effects of solution pH values, initial concentration, inorganic anions, PMS dosage, catalyst dosage, and metal loading amount on RhB removal were investigated. The method of initial rates was employed to determine the intrinsic reaction rate law, and the reaction was identified to follow the Langmuir-Hinshelwood (L-H) kinetics model.