Order Rate Law Research Articles

Adsorption kinetic modeling using pseudo-first order and pseudo-second order rate laws: A review

Adsorption for water and wastewater treatment has been the subject of many research in the scientific community, focusing mainly on either equilibrium or kinetic studies. Adsorption kinetics are commonly modeled using pseudo-first and pseudo-second order rate laws. Analyses of published works in the past two decades indicated that the pseudo-second order is considered to be the superior model as it can represent many adsorption systems. However, critical assessment of modeling techniques and practices suggests that its superiority could be a consequence of currently acceptable modeling norms which tend to favor the pseudo-second order model. The partiality was due to several modeling pitfalls that are often neglected. In addition, commonly used model validation tools are often used haphazardly and redundantly. As such, they cannot sufficiently provide any kind of certainty on the validity of a model. To eliminate modeling biasness, a new validation method was proposed and was then employed to re-examine previously published adsorption kinetic data.

Kinetics of solid reactions with gas intermediates in chemical looping combustion

• Reaction route of the CLC reactions with gas intermediates were identified. • The effect of solid particle size ranges was analyzed. • The sensitivity of reaction temperature was determined. • The kinetics models could be used in the solid reactions with gas intermediates. Chemical looping combustion (CLC) is an advanced technology for converting solid fuel with in-situ CO 2 capture in a low-cost and sustainable way. However, unlike gaseous fuel, the CLC process of solid fuel is lack of the reaction understanding between fuel particles and OC particles (solid-to-solid), and this result directly influences the design of the reactor. In this context, the study focused on the solid reactions with gas intermediates taking place in the CLC reactor. Well-mixed solid particles of the coal char and the hematite were investigated on the thermogravimetric and mass spectrometry (TG-MS) system. The effects of different particle size ranges and different reaction temperatures were determined. The kinetics on this kind of solid reactions was calculated and discussed. The result showed that the carbon gasification was identified as the control step in reactions. The diffusional resistance of 45–75 µm char particles could be ignored. Two models of kinetic reactions were developed based on the contracting sphere rate law and the first order rate law. The Activation Energy E a of the surface reaction model and the first order reaction model was 208.75 kJ/mol and 224.75 kJ/mol, respectively. Overall, the experiments and the kinetic models carried out in the present work improved the reaction understanding on the field of the solid reactions with gas intermediates in CLC.

Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2 and Propylene Oxide.

The ring-opening copolymerization of carbon dioxide and propene oxide is a useful means to valorize waste into commercially attractive poly(propylene carbonate) (PPC) polyols. The reaction is limited by low catalytic activities, poor tolerance to a large excess of chain transfer agent, and tendency to form byproducts. Here, a series of new catalysts are reported that comprise heterodinuclear Co(III)/M(I) macrocyclic complexes (where M(I) = Group 1 metal). These catalysts show highly efficient production of PPC polyols, outstanding yields (turnover numbers), quantitative carbon dioxide uptake (>99%), and high selectivity for polyol formation (>95%). The most active, a Co(III)/K(I) complex, shows a turnover frequency of 800 h–1 at low catalyst loading (0.025 mol %, 70 °C, 30 bar CO2). The copolymerizations are well controlled and produce hydroxyl telechelic PPC with predictable molar masses and narrow dispersity (Đ < 1.15). The polymerization kinetics show a second order rate law, first order in both propylene oxide and catalyst concentrations, and zeroth order in CO2 pressure. An Eyring analysis, examining the effect of temperature on the propagation rate coefficient (kp), reveals the transition state barrier for polycarbonate formation: ΔG‡ = +92.6 ± 2.5 kJ mol–1. The Co(III)/K(I) catalyst is also highly active and selective in copolymerizations of other epoxides with carbon dioxide.

Thermal Stability of a Eutectic Mixture of Bis(2,2‐dinitropropyl) Acetal and Formal: Part C. Kinetic Compensation Effect

AbstractThe aging behavior of a eutectic mixture of bis(2,2‐dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70 °C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55 °C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO2 follows a 1st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre‐factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55 °C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55 °C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NOx, water, and HNO3 serve as catalysts to auto‐catalyze (kinetics beyond the 1st order) and further degrade NP. The effect of headspace volume on this auto‐catalytic process will be discussed.

Degradation kinetics of DDT in tropical soils: A proposed multi-phase zero order kinetic model that takes into account evaporation, hydrolysis, photolysis, microbial degradation and adsorption by soil particulates.

The Food and Agriculture Organization (FAO) and International Atomic Energy Agency (IAEA) commissioned a 5-year international programme during 1989 to 1993 to study the behaviour of DDT in 10 tropical countries: India, Indonesia, Pakistani, China, Philippines, Egypt, Tanzania, Kenya, Panama and Brazil. The traditional approach of plotting the residual pesticide concentration as a function of time was employed to treat the data in order to arrive at the half-life of the pesticide in the specific environment. However, most of the curves obtained were not first order, as the dissipation was observed to be biphasic, prompting the authors to suggest that the dissipation could best be characterized in terms of a multi-phase dissipation model. The aim of the present work was to derive a possible multi-phase dissipation kinetic model to account for the observed poly-phasic nature of the data from the FAO/IAEA study. Data are presented showing that when the loss in the pesticide concentration, rather than the residual pesticide concentration, is plotted as a function of time, the curve can be resolved into biphasic or triphasic linear curves, which are interpreted in terms of pseudo zero order rate equations derived taking into account dissipation of the pesticide via evaporation, hydrolysis, photolysis, microbial degradation and adsorption by soil and colloidal particles. The predictions of the zero order dissipation kinetic models when compared to the first order rate law are discussed.Capsule:The degradation of DDT in tropical soils is characterized in terms of multi-phase zero order kinetics.

Clean sandbox (Hura crepitans) oil methyl esters synthesis: A kinetic and thermodynamic study through pH monitoring approach

Abstract In this study, oil was extracted from underutilized sandbox seeds and converted into biodiesel via transesterification process using KOH as a base catalyst. The impact and optimum values of the essential process variables (methanol-to-sandbox seed oil (SSO) ratio, KOH loading, reaction temperature and reaction time) on the sandbox oil methyl esters (SBOME) yield were established via Taguchi orthogonal array design method. Kinetic modeling of the transesterification process was carried out by monitoring the pH of the reaction. Maximum SBOME yield of 97.10 ± 0.03 wt% could be achieved under optimal condition of methanol-to-SSO molar ratio of 6:1, KOH loading of 0.5 wt%, reaction temperature of 35 °C and reaction time of 25 min. The kinetics of the process followed a unimolecular pseudo-second order rate law with reaction rate of 0.0016 L/mol.min at 35 °C. The activation energy and frequency factor of the reaction were calculated to be 11.40 kJ/mol and 0.1362 L/mol.s, respectively. The ΔH‡, ΔS‡ and ΔG‡ for the process were determined as 8.76 kJ/mol, – 0.270 kJ/mol.K and 92.02 kJ/mol, respectively. The quality of the SBOME demonstrates that it could serve as a replacement for diesel as its properties complied with standard specifications for biodiesel. The kinetic data obtained in this study could be used in reactor design for the process.

The reactions of the Cu(II)-nitrilotris(methylenephosphonic acid) complex with alkyl radicals in aqueous solutions

The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were studied. The kinetics of formation of the transient complexes (ntp)CuIII-R fit pseudo first order rate laws. The mechanism of decomposition of the transient complex (ntp)CuIII-CH3 at pH ≥ 7 involves homolysis of the CuIII-C bond. However, at pH < 6 the decomposition mechanisms of the transient complexes (ntp)CuIII-R involve inter-molecular electron transfer to CuII(ntp)(H2O) and slow intra-molecular electron transfer.

Magnetic Sorbent for the Removal of Selenium(IV) from Simulated Industrial Wastewaters: Determination of Column Kinetic Parameters

A novel meso- and microporous tire-derived-carbon support with magnetic iron oxide nanoparticle adsorbents that selectively adsorbs Se(IV) ions from simulated contaminated water has been developed. In this work, the physicochemical characteristics of the composite adsorbent are characterized with respect to porosity and surface area, chemical composition, and microstructure morphology. The kinetics of this composite adsorbent in a fixed-bed setting has been determined. Several column runs were conducted and analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) to determine the concentration gradient vs time. These results were then fit to a pseudo-second order rate law to obtain equilibrium values. Combining calculated equilibrium values with effluent concentration data, enabled the application of the Adams–Bohart model to determine reaction constants and column coefficients. Column parameters obtained from different flow rates and fittings of the Adams–Bohart model were remarkably consistent. These findings enable the application of this sorbent to fixed-bed column systems and opens up further research into mixed pollutants tests with real wastewater and scaling of selenium pollutant removal.

Kinetics of water‐extractable zinc release from seaweed (Fucus serratus) as soil amendment

AbstractSoil fertilization with trace‐metal rich organic fertilizers such as Fucus serratus seaweed may be an effective way to combat micronutrient deficiency. In this study the kinetics of zinc release from Fucus serratus seaweed was investigated in a packed soil column leaching experiment over 1,776 h. The release of zinc from control (soil only) and treatment (soil + seaweed; equivalent zinc application rate of 1.42 kg ha−1) columns, measured by ICP‐MS, demonstrated two distinct release stages. The cumulative zinc release data for each phase were fitted to five kinetic models: zero order, first order, Elovich, power function and parabolic diffusion. In the first stage (0–400 hours) the release of zinc from both control and treatment was best described by a parabolic rate law, indicating release of zinc from a soluble soil reservoir. In the second stage (400–1,776 h) zinc release followed a zero order rate law indicative of slow release from an essentially insoluble reservoir. The modelled difference between the amount of zinc released from treatment and control columns in stage 1 (230 ± 11 µg) represented the total amount of zinc added via seaweed. The parabolic rate constant for seaweed zinc release was 12.09 µg g−1 h−0.5. In summary, the addition of F. serratus to soil is a viable source of labile zinc and a low cost agronomic option for mitigating zinc deficiency in soils.

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The inhibition effects of methanol leaf extract of Talinum triangulare on the corrosion of mild steel in 0.4, 0.5, 0.6 and 2.5M H2SO4 solution were determined in this study. The inhibition efficiency was evaluated and the mechanism of inhibition determined, with a view to determining the inhibitive potentials of the inhibitor with regard to corrosivity of acid solutions used in oil pipelines, water treatment systems and descaling of equipment. Weight loss and gasometric techniques were used for the corrosion study of the metal. The weight loss method of corrosion tests was carried out at 2, 4, 6, 8 and 10 hours of exposure using various concentrations of extract (0.2, 0.4 and 0.6) g/L at different temperatures (303K, 313K and 323K) in varying acid concentration (0.4M, 0.5M and 0.6M). The gasometric measurements were carried out at 5, 10, 15, 20, 25 and 30 minutes exposure time using various concentrations of extract (0.2, 0.4 and 0.6) g/L in 2.5M H2SO4 solution. Weight loss measurements were also carried out concurrently with gasometric measurements to compare methodological variation in data between them. The phytochemical screening results revealed the presence of tannins, saponnins, flavonoids, terpenes, steroids and alkaloids. From the results, the corrosion rates decreased with increase in inhibitor concentration. The maximum inhibition efficiency of the extract for the weight loss measurements are 70.77% for 0.6g/L in 0.4M H2SO4 at 303K, 54.86% for 0.6g/L in 0.5M H2SO4 at 303K and 61.66% for 0.6g/L in 0.6M at 303K. In 2.5M H2SO4, the maximum inhibition efficiency was observed to be 59.31% for 0.6g/L inhibitor concentration at 308K for the gasometric method and 53.38% for 0.6g/L at 308K for the weight loss method. The kinetic and thermodynamic studies showed that the activation energy (Ea) in the presence of inhibitor is greater than in the absence of inhibitor at all the temperatures studied. The reaction was proposed to be first order having shown good correlation (R2≈1) with the first order rate law, and the half-life (t1/2) values were obtained from the graphs of the rate law. The mechanism of physical adsorption was proposed for the extract, as within the temperature range investigated the Ea and ∆Goads values are less than 80kJ/mol and -20kJ/mol respectively.

Removal of reactive brilliant red X-3B by a weak magnetic field enhanced Fenton-like system with zero-valent iron.

The effect of a weak magnetic field (WMF) on the removal of reactive brilliant red X-3B (X-3B) by zero-valent iron (ZVI)/H2O2 was studied. The optimum conditions for the removal of X-3B by the ZVI/H2O2/WMF system were as follows: pH = 4.0, X-3B was 50 mg L−1, H2O2 was 8 mM, and ZVI with particle size of 20 μm was 0.5 g L−1. The X-3B decolorization rate could reach 99.41% in 10 minutes. The superposed WMF increased the working pH of ZVI from 3.0 to 4.0. The main part of ZVI/H2O2 removal kinetics of X-3B followed the zero order rate law. In this study, the removal effect of X-3B by pre-magnetization ZVI was not as good as that of real-time magnetization, but it was better than the removal of X-3B by the ZVI/H2O2 system. The ZVI/H2O2/WMF system still had the ability to remove X-3B after 4 consecutive cycles. The use of WMF improved the removal of X-3B by ZVI/H2O2 mainly due to the corrosion of ZVI. Under acidic conditions, WMF enhanced the activity of ZVI, which promoted the efficiency of the Fenton reaction. The use of WMF to enhance the ZVI/H2O2 removal X-3B was a promising and environmental friendly process because it did not require additional energy and expensive reagents and did not cause secondary pollution.

Co-precipitation synthesis of Mg-Al-CO3 layered double hydroxides and its adsorption kinetics with phosphate(V) ions

Phosphorus (P) is an essential mineral nutrient in crop production. Phosphorus runoff and leaching from agricultural lands leads to eutrophication, causing hypoxia and anoxia in bodies of water. Mitigation of this problem through P removal is essential to prevent detrimental damages to the environment. In this work, Mg-Al-CO3 layered double hydroxides (LDH) were synthesized via co-precipitation method and its capacity as a potential phosphate(V) adsorbent was investigated. Analysis of various material properties of the Mg-Al-CO3 LDH was performed using Fourier transform spectroscopy (FTIR), powder X-ray diffraction (pXRD), thermogravimetric analysis (TGA), and field emission-scanning electron microscopy (FE-SEM). Furthermore, The adsorption kinetics of phosphate(V) ions on Mg-Al-CO3 LDH was studied using spectrophotometric techniques and was found to fit the Langmuir isotherm model, following a pseudo-second order rate law. Moreover, the results suggest the adsorption of phosphate(V) ions unto Mg-Al-CO3 LDH is dependent on chemisorption.

CONTINUOUS IMPROVEMENTS IN THIRD YEAR CHEMICAL ENGINEERING DESIGN

An impending retirement has led us to reevaluate the course: should we keep it - and if so who teaches it, or should we look to change it? The course was co-taught with a new faculty member, coupled with internal reviews and discussions. Ultimately, we decided to keep the course, and also to work to broaden its base. &#x0D; Historically, the design problems have been petrochemical in nature. Each team gets a reaction, with a first order rate law, as well as a production rate and fractional conversion. From this, they do the design calculations for a reactor and separator, and also generate the base engineering drawings. &#x0D; This past year, the project types were expanded to include environmental remediation and hydrometallurgical extraction. The environmental remediation problems involved wastewater processing (eg., BOD oxidation) which can be treated as a first order reaction. The hydrometallurgical problem (Li leaching from spodumene) also was set up as first order. Additionally, we provided the option of a case study review. The students chose a classic chemical safety incident, reviewed the details, and created a summary report which included recommendations on how to incorporate learnings from the incident into the curriculum.&#x0D;

Kinetic study of the photocatalytic oxidation of ethylene over TiO2 thin films

The photocatalytic oxidation process has been recognized as an environmental friendly, sustainable and low-cost technology for air treatment. A photocatalytic batch reactor has been employed to assess the kinetics of the oxidation of ethylene (C2H4) over immobilized titanium dioxide (TiO2) and the effect of initial pollutant concentration on the kinetics. The rate model based on the simplified mono-molecular Langmuir-Hinshelwood (LH) kinetic model was found to represent the degradation satisfactorily, however with numerical constrains. These were overcome by employing two different approaches. On one hand the Langmuir-Hinshelwood model was solved by means of the Lambert W-function and on the other hand it was reduced to a pseudo-first order rate law, both resulting in a good fit to the experimental data, thus proving that the photodegradation of C2H4 over TiO2 can be modelled by a first order rate law under low concentration conditions. Moreover, both models give a linear dependence between the reaction rate and the initial C2H4 concentration, making an estimation of reaction rate as a function of concentration possible, for a larger interval of C2H4 concentrations.

The kinetics of lattice distortion introduction and lattice relaxation at the surface of thermally-oxidized 4H-SiC (0001)

The kinetics of lattice distortion introduction and lattice relaxation at the surface of thermally-oxidized 4H-SiC (0001) were investigated. Our results suggested that lattice distortion introduction and lattice relaxation seem to follow zeroth and second order rate laws, respectively. The obtained activation energy of ∼3.9 eV for lattice distortion introduction and ∼1 eV for its relaxation indicate that the lattice distortion is determined by a bond rearrangement or movement process with a relatively low activation energy. Furthermore, the formation of byproducts which remain at the surface region of 4H-SiC was predicted to be a possible origin of the significant lattice distortion.

Development of a rate law for arsenite oxidation by manganese oxides

Abstract Arsenite (As(III)), may be rapidly oxidized to arsenate (As(V)) by manganese oxides over a wide range of pH. Interestingly, pseudo-first order rate constants for Mn(IV) oxides (MnO2) reported in the literature differ by orders of magnitude, mainly due to the fact that experimental conditions have not been normalized and surface passivation may hinder the reaction rate. As a result, a formal kinetic rate law for the oxidation of As(III) by MnO2 does not exist. In this study, a comprehensive rate law that describes the abiotic oxidation of As(III) by vernadite (δ-MnO2) was developed by systematically varying pH and the concentrations of δ-MnO2 and As(III). Experiments were performed with excess δ-MnO2 compared to As(III) in buffered solutions with an ionic strength typical of freshwater environments to reflect the geochemical conditions of most environments. The half-life of the pseudo-first order reaction is less than three minutes in all experiments. Results show the initial reaction rate is proportional to the concentrations of δ-MnO2 and As(III) and independent of pH in the pH range 4–9. However, below pH 6 and above pH 8 the pseudo-first order rate constant is slightly lower due to the protonation of the surface δ-MnO2 and the deprotonation of As(III). Overall, the reaction follows a first order rate law with respect to As(III) and effective surface sites of δ-MnO2 and zeroth order with respect to pH. The overall second order rate constant, k, was calculated to be 0.36 ± 0.11 L h−1 m−2. This rate constant is comparable to the vast majority of rate constants derived from previously published data when using the effective surface sites of MnO2 as reactive species only, indicating the most influential factors of As(III) oxidation by MnO2 are constrained in the developed rate law. Based on the present experiments, the oxidation of As(III) by MnO2 is proposed to proceed as one two-electron transfer reaction between As(III) and Mn(IV) to eventually form As(V) and Mn2+ species. Two steps of one-electron transfer, however, may be possible though it is likely that both Mn(IV) and Mn(III) species are ultimately reduced to Mn2+. Comproportionation of Mn2+ and Mn(IV) to Mn(III) does not seem to be important on the time scale of these experiments.

The Kinetics of Cd2+ and Pb2+ Leaching from Fly Ash Geopolymers

This research is aimed to reveal the kinetics of Cd2+ and Pb2+ leaching from fly ash geopolymer as a promising and sustainable method to solve the problems of heavy metals contamination. The geopolymer was made by using fly ash of PT. IMPOMI in East Java, Indonesia and the ratio of SiO2/Al2O3 = 6.5, Solid/Liquid (S/L) = 3.59 and Na2SiO3/NaOH = 2.5. A solution of Cd (NO3)2 or Pb(NO3)2 were added at 1,000, 4,000, 8,000 or 16,000 ppm relative to the weight of fly ash. Compressive strength test of geopolymers was carried out at the end of day 7 after curing the geopolymer mixture at room temperature. Leaching tests for the kinetics and mechanisms studies were carried using TCLP method by immersing the resulted geopolymers into 0.01 M acetic acid solution. The ratio of geopolymer mass to the volume of acetic acid solution was 1:25. ICP-OES was used to measure the leached Cd2+ and Pb2+ while SEM-EDS was used to study the morphology and heavy metal distribution on the polished geopolymer cross section. It was found that the compressive strength of Cd2+ geopolymer was slightly higher than those of Pb2+-geopolymer. The strength of geopolymer decreased at higher concentration of heavy metal cations. The maximum strength (24.4 MPa) was shown by 4,000 ppm Cd2+ geopolymer while SEM-EDX images showed that Cd2+ and Pb2+ were distributed uniformly from the surface to the core of geopolymers. The leaching test reveals that more than 99.5 % of Cd2+ and Pb2+ were retained by geopolymer while in depth kinetics investigation of both Cd2+ and Pb2+ leaching shows that the leaching rate follows the first order rate law with two step leaching processes. The first originates from cations at the surface followed by cations from the bulk of geopolymer.

Advances in bone preservation: Identifying possible collagen preservation using sulfur speciation mapping

The complexity and heterogeneity of bone chemistry makes it difficult to discern information on physiological and taphonomic processes stored within the bone matrix. Analysis of archaeological and palaeontological bone becomes more difficult because in many cases the most pivotal specimens are too scientifically valuable for destructive analysis. This problem is further escalated by the fact that the heterogeneity of the bone may cause small “pockets” of preservation that can be missed during sampling. Therefore, a non-destructive technique that can spatially resolve such heterogeneity within the bone is needed. Here we use microfocus, non-destructive synchrotron-based X-Ray Fluorescence (XRF) imaging and X-ray Absorption Spectroscopy (XAS) to map the organic constituents within extant and fossil bovid bones. XAS analysis of sulfur allowed organic sulfur (within collagen as methionine) to be distinguished from inorganic sulfate (within bone apatite). Mapping and quantification of organic sulfur within the samples were made by setting the beam to the methionine resonance, allowing for the detection, distribution and quantification of collagen present by using organic sulfur as an internal marker. Results show organic sulfur to be distributed in small “pockets” throughout the bone matrix in both extant and fossil specimens. Significant loss of organic sulfur was seen in specimens between 100 ka and 650 ka with little organic sulfur preservation persisting after this date. Comparison of residual organic sulfur concentrations as a function of sample age revealed a second order rate law for organic sulfur oxidation (k ≈ 1 × 10−5 y−1) within bone. These results show that non-destructive, synchrotron-based XRF mapping of organic sulfur is a useful tool for not only calculating rates of collagen degradation through time, but also identifying areas of potential collagen preservation for other paleobiological applications such as proteomics and stable isotope analyses.

Efficient removal of bisphenol A from wastewaters: Catalytic wet air oxidation with Pt catalysts supported on Ce and Ce–Ti mixed oxides

Catalytic wet air oxidation (CWAO) of an aqueous solution of bisphenol A (BPA) was investigated at 160 ℃ and 2.0 MPa of air in a batch reactor. Activity of supported platinum catalysts (2.5 wt%), prepared by wet impregnation, was compared with pure cerium and cerium–titanium oxide catalysts. Supported platinum catalysts showed higher activities in the removal of BPA than pure CeO2, Ce0.8Ti0.2O2 and Ce0.2Ti0.8O2. The oxidation reaction was followed the pseudo-first order rate law and the highest BPA removal, 97% and 95%, was achieved with Pt/CeO2 and Pt/Ce0.8Ti0.2O2 catalysts respectively. The CWAO of BPA aqueous solution was not a surface area specific reaction but the more important factor affecting the activity of studied catalysts was the amount of chemisorbed oxygen of these samples.

Catalytic Cleavage of the Amide Bond in Urea Using a Cobalt(III) Amino‐Based Complex

The urease mimetic activity of CoIII amine complexes with respect to cleavage of urea was explored using SCXRD and spectroscopic techniques. The reaction of [CoIII(tren)Cl2]Cl [tren = tris(2‐aminoethyl)amine] with urea results in the formation of an isocyanato complex {[CoIII(tren)(NH3)(NCO)]Cl2} and ammonia, following the cleavage of the amide bond. The reaction progress and the subsequent formation of cleavage products were confirmed by SCXRD analysis of the reactants as well as the products obtained during the reaction. The reaction was found to be pH and temperature dependent, and the reaction conditions were optimized to maximize conversion. The reaction kinetics was followed spectroscopically (1H NMR and UV/Vis), following the decrease in urea concentration or the increase in pH succeeding ammonia formation. A detailed kinetic study revealed an overall second order rate law and kobs was found to be 3.89 × 10–4 m–1 s–1.