Kinetic Studies Research Articles

Converting CO2 into natural gas within the autoclave: a kinetic study on hydrogenation of carbonates in aqueous solution.

Catalytic conversion of carbon dioxide (CO2) into value-added chemicals is of pivotal importance, well the cost of capturing CO2 from dilute atmosphere is super challenge. One promising strategy is combining the adsorption and transformation at one step, such as applying alkali solution that could selectively reduce carbonate (CO32-) as consequences of CO2 adsorption. Due to complexity of this system, the mechanistic details on controlling the hydrogenation have not been investigated in depth. Herein, Ru/TiO2 catalyst was applied as a probe to elucidate the mechanism of CO32- activation, in which with thermodynamic and kinetic investigations, a compact Langmuir-Hinshelwood reaction model was established which suggests that the overall rate of CO32- hydrogenation was controlled by a specific C-O bond rupture elementary step within HCOO- and the Ru surface was mainly covered by CO32- or HCOO- at independent conditions. This assumption was further supported by negligible kinetic isotope effects (kH/kD ≈ 1), similarity on reaction barriers of CO32- and HCOO- hydrogenation (ΔH‡hydr,Na2CO3 and ΔH‡hydr,HCOONa) and a non-variation of entropy (ΔS‡hydr ≈ 0). More interestingly, the alkalinity of the solution is certainly like a two sides in a sword and could facilitate the adsorption of CO2 while hold back catalysis during CO32- hydrogenation.

Efficient photocatalytic activity and selective adsorption of UiO-67 (Zr)/g-C3N4 composite toward a mixture of parabens

In this study, UiO-67 (Zr)/g-C3N4 composites (U67N) were synthesized at wt.% ratios of 05:95, 15:85, and 30:70 using the solvothermal method at 80 °C for 24 h followed by calcination at 350 °C. The composites were characterized using UV–Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, transmission electron microscopy, and nitrogen physisorption analysis. In addition, thermal stability analysis of UiO-67 was conducted using thermogravimetric analysis.The photocatalytic performance of the composites was assessed during the degradation and mineralization of a mixture of methylparaben (MeP) and propylparaben (PrP) under simulated sunlight. The adsorption process of U67N 15:85 was characterized through kinetic studies and adsorption capacity experiments, which were modeled using pseudo-first-order and pseudo-second-order kinetics and Langmuir and Freundlich isotherms, respectively.The influence of pH levels 3, 5, and 7 on the photocatalytic degradation of the mixture was investigated, revealing enhanced degradation and mineralization at pH 3. The U67N composite exhibited dual capability in removing contaminants through adsorption and photocatalytic processes. Among the prepared composites, U67N 15:85 demonstrated the highest photocatalytic activity, achieving removal efficiencies of 96.8% for MeP, 92.5% for PrP, and 45.7% for total organic carbon in 300 kJ/m2 accumulated energy (3 h of reaction time). The detoxification of the effluent was confirmed through acute toxicity evaluation using the Vibrio fischeri method.The oxidation mechanism of the heterojunction formed between UiO-67 (Zr) and g-C3N4 was proposed based on PL analysis, photoelectrochemistry studies (including photocurrent response, Nyquist, and Mott–Schottky analyses), and scavenger assays.

A comprehensive kinetic study on low-GHG hydrogen production from microwave-driven methane pyrolysis

The present study focuses on the cogeneration of hydrogen (H2) and solid carbon from microwave-driven methane pyrolysis in a fluidized bed of carbon pellets. Numerical simulations using a coupled gas-solid chemistry approach reveal that introducing microwave thermal effects improves methane conversion rate, H2 selectivity, and carbon deposition rate. The chemical pathways analysis divulges that once the leading reaction for decomposing CH4 into H2, i.e., CH4+H ↔ CH3+H2, is completed, the C2H2 deposition mechanism onto the carbon pellets is the dominant pathway for the solid carbon production, indicating almost no carbon black (i.e., nanoparticles) formation. Carbon pellets provide abundant surface area for the conversion of C2H2 to H2, enhancing H2 selectivity in the resulting products. More importantly, the importance of more complex molecules, such as polycyclic aromatic hydrocarbons, greatly diminishes when using carbon pellets in the pyrolysis process, implying that smaller kinetic mechanisms are equally effective and desirable.

Chiral phosphoric acid-catalyzed asymmetric epoxidation of alkenyl aza-heteroarenes using hydrogen peroxide

The synthesis of chiral α-azaheteroaryl oxiranes via enantioselective catalysis is a formidable challenge due to the required complex stereoselectivity and diverse N-heterocyclic structures. These compounds play a crucial role in developing bioactive molecules, where precise chirality significantly influences biological activity. Here we show that using chiral phosphoric acid as a catalyst, our method efficiently addresses these challenges. This technique not only achieves high enantio- and diastereoselectivity but also demonstrates superior chemo- and stereocontrol during the epoxidation of alkenyl aza-heteroarenes. Our approach leverages a synergistic blend of electrostatic and hydrogen-bonding interactions, enabling the effective activation of both substrates and hydrogen peroxide. The resulting chiral oxiranes exhibit enhanced diversity and functionality, aiding the construction of complex chiral azaaryl compounds with contiguous stereocenters. Kinetic and density functional theory studies elucidate the mechanism, highlighting chiral phosphoric acid’s pivotal role in this intricate enantioselective process.

Impact of Iron Species Dispersion on Fe/ZSM‐5 Catalyst Performance for Methane Dehydroaromatization (MDA)

AbstractMethane dehydroaromatization (MDA) is one of the most promising technologies for directly transforming methane into aromatics. Unlike the extensively investigated Mo/ZSM‐5 catalysts, the structure and, consequently, the catalytic activity of Fe/ZSM‐5 are markedly influenced by the method of preparation, as shown here. In this study, we prepared 2 % and 4 % Fe/ZSM‐5 catalysts via wet impregnation (WI) and incipient wetness impregnation (IWI). Characterizations (XRD, STEM, UV‐Vis, NH3‐TPD and H2‐TPR) reveal that 2 %Fe‐WI mainly possesses isolated or low‐polymerized Fe species within zeolite channels, leading to a rapid activation and a higher benzene yield due to the faster reduction to iron suboxides under MDA conditions. In contrast, 2 %Fe‐IWI contains bulk iron oxide aggregates, resulting in a slower activation as these aggregates transform into iron carbide through successive reduction and carbonization. A deactivation kinetic study applied to the 2 % catalysts further demonstrates the quantitative relation between Fe site isolation and catalytic activity. Although both 4 % catalysts inevitably form sizable iron oxide clusters and particles due to the high Fe/Al ratio, similar trends are noted, with the WI catalysts exhibiting a shorter induction/activation period and a higher yield of benzene, paralleling observations made with 2 % catalysts.

Facile Fabrication of Hydroxyapatite and Bentonite Encapsulated Biopolymeric Hybrid Composites for Selective Removal of Methylene Blue

AbstractDyeing industries release their hazardous dyeing effluents into the environment which affects the human health and ecosystem. Hence, the removal of dye from waste‐water is mandatory one. In this present study, focus on the fabrication of bio‐clay‐ceramic hybrid composites by dispersing bentonite (BT) clay and ceramic hydroxyapatite (HA) into alginate (Alg) and gelatin (Gel) polymeric matrixes by in‐situ method which gives BTHAAlg and BTHAGel hybrid composites for methylene blue (MB) removal. The various adsorption influencing parameters such as shaking time, adsorbent dosage, pH and initial MB concentration were optimized under batch method. The highest MB adsorption capacities of BTHAAlg and BTHAGel composites were found to be 43.70 and 47.50 mg/g respectively with optimized conditions of 100 mg/L of initial MB concentration, 40 min shaking time and 0.1 g dosages. In pH studies, the high MB adsorption capacity of bio‐clay‐ceramic composites were noticed at pH 11. The characterization techniques like FTIR, SEM and EDAX analysis were performed to find the physico‐chemical properties of bio‐clay‐ceramic composites. The equilibrium data of hybrid composites towards MB adsorption was well fitted with Langmuir isotherm model than D‐R and Fruendlich models because of higher r and low sd values. The negative values of ▵Go at three different temperatures (303, 313 and 323 K) indicate that the spontaneous nature of MB adsorption, while positive values of ΔHo and ΔSo revealed that the MB adsorption onto hybrid composites was endothermic in nature and more randomness occurred at solid/liquid interfaces. In kinetic studies, the MB adsorption onto hybrid composites was well fitted with pseudo‐second‐order and intra‐particle diffusion models. The electrostatic attraction and hydrogen bonding plays a dominant role in MB adsorption onto BTHAAlg and BTHAGel bio‐clay‐ceramic composites. The regeneration studies proposed that the hybrid composites can be reusable upto five cycles. Hence, the developed bio‐clay‐ceramic hybrid composites were act as best adsorbents for MB removal.

The ultrasound leaching kinetics of copper in the H2SO4 dissolution process

ABSTRACT The atmospheric immersion copper dissolution method, commonly employed in the current copper foil production process, is confronted with challenges such as low oxidation ability and the formation of passivation layers on the copper surface. These issues result in slow copper dissolution rates, significantly restricting copper foil production. To overcome this limitation, ultrasound is used to improve the copper dissolution process. The impact of ultrasound on the rate and kinetics of copper dissolution in a sulfuric acid solution was studied. Various factors, including ultrasound power, temperature, Cu2+ concentration, sulfuric acid concentration, and air flow rate, were analysed to assess their influence on the rate of copper dissolution. The optimised dissolution conditions were determined to be 30 g/L Cu2+, 120 g/L sulfuric acid, 300 mL/min air flow, 60°C, and 300 W ultrasonic power. The copper dissolution rate is 1.96 times higher when ultrasound is applied compared to conventional conditions. According to the kinetic study, ultrasound reduced the apparent activation energy from 61.12 kJ/mol to 46.44 kJ/mol, significantly lowering the potential barrier for copper dissolution. This study provides valuable insights for accelerating the dissolution process of copper using ultrasound-assisted technology.

Engineered Robust Hydrophobic/Hydrophilic Nanofibrous Scaffolds with Drug-Eluting, Antioxidant, and Antimicrobial Capacity.

Multifunctional nanofibrous architectures have attracted extensive attention for biomedical applications due to their adjustable and versatile properties. Electrospun fabrics stand out as key building blocks for these structures, yet improving their mechanobiological and physicochemical performance is a challenge. Here, we introduce biodegradable engineered hydrophobic/hydrophilic scaffolds consisting of electrospun polylactide nanofibers coated with drug-eluting synthetic (poly(vinyl alcohol)) and natural (starch) polymers. The microstructure of these composite scaffolds was tailored for an increased hydrophilicity, optimized permeability, water retention capacity of up to 5.1 g/g, and enhanced mechanical properties under both dry and wet conditions. Regarding the latter, normalized tensile strengths of up to 32.4 MPa were achieved thanks to the improved fiber interactions and fiber-coating stress transfer. Curcumin was employed as a model drug, and its sustained release in a pure aqueous medium was investigated for 35 days. An in-depth study of the release kinetics revealed the outstanding water solubility and bioavailability of curcumin, owing to its complexation with the hydrophilic polymers and further delineated the role of the hydrophobic nanofibrous network in regulating its release rate. The modified curcumin endowed the composites with antioxidant activities up to 5.7 times higher than that of free curcumin as well as promising anti-inflammatory and bacteriostatic activities. The cytocompatibility and cell proliferation capability on human dermal fibroblasts also evidenced the safe use of the constructs. Finally, the fabrics present pH-responsive color-changing behavior easily distinguishable within the pH range of 5-9. Thus, these designs offer a facile and cost-effective roadmap for the fabrication of smart multifunctional biomaterials, especially for chronic wound healing.

Adsorption of NMST from acetic acid on coconut activated carbon: Kinetics, isotherms and thermodynamics

ABSTRACT Exploration has been made into 2-nitro-4-methylsulfonyltoluene (NMST) adsorption on coconut activated carbon from acetic acid. The results demonstrate that the adsorption of NMST on activated carbon augments with its concentration in acetic acid. NMST adsorption on activated carbon is also improved with temperature. Though NMST adsorption on per gram of carbon will decrease with carbon dosage, more NMST will be adsorbed. The kinetic study depicts that NMST adsorption on activated carbon is in good agreement with the pseudo-second-order kinetic equation. Both of the Langmuir and Freundlich equilibrium isotherm models are well fit for the experimental results, with R2 = 0.9994 and 0.9979, respectively. The adsorption thermodynamic parameters (ΔH, ΔG, ΔS) calculated with Van’t Hoff equations indicate that NMST adsorption on carbon is spontaneous and endothermic.

Dehydration of fructose to 5‐HMF catalyzed by commercial faujasite zeolites: kinetic study and influence of the properties of the catalyst

We carried out a mechanistic investigation of the dehydration of fructose catalyzed by a series of proton‐exchanged faujasite zeolites. Using a combination of analytical tools (HPLC, GC, NMR), we could solve and quantify most of the variety of products formed, including (i) cyclic intermediates (ii) transient species (monomeric and dimeric) (iii) byproducts (oligomeric species and humins). The results prove that the reaction goes through a cyclic mechanism, and we could propose a kinetic model matching most of our experimental results and describing the interplay between the different categories of products. By comparing the performances of different catalysts with varying properties, we surprisingly find that increasing the concentration of Brønsted acid sites induces lower catalytic activity. Contrary to general expectations, the mesoporous volume seems to be the most determining parameter for the activity of the catalysts over the set of catalysts evaluated here, which may be explained by the importance of allowing the reactant a significant accessibility to the active sites.

A computational study of solidification kinetics in multicomponent alloys

Recent advances in materials processing technologies highlight the need to understand solidification kinetics in multicomponent alloys. Using a finite interface dissipation phase field model, we investigate planar front solidification rates in ternary alloys, used as a model system, as a function of various mass transport processes and nonequilibrium conditions. Simulation results reveal that the off-diagonal diffusion coefficients play an important role in controlling the solid–liquid (S–L) interface velocity and solute partition coefficients. Specifically, under various rapid solidification conditions negative values for the off-diagonal diffusion coefficients increase the solute partition coefficients due to the depletion of liquid phase concentrations ahead of the S–L interface. Given an undercooling, the S–L interface velocity increases with decreasing the off-diagonal diffusion coefficients. In broad terms, our work quantifies the role of coupled mass transport processes and nonequilibrium effects in solidification rates of multicomponent alloys.

Flotation performance and kinetics study of low-grade limestone with fatty acids-rich oilseed residue as green collector

With the depletion of mineral resources and increasing environmental protection requirements, researching and developing efficient and environmentally friendly flotation agents is crucial for the comprehensive utilization of mineral resources. Low-grade limestone deposits with high impurities pose a challenge for efficient processing and direct industrial applications. This study explores a novel and sustainable approach to address this challenge by evaluating the prospective use of a fatty-acid-rich oilseed residue as a bio-collector (referred to as collector SSFA) to recover carbonates from a low-grade limestone, characterized by high acid insolubles content and its influence on the kinetics of the flotation process. The bio-collector (SSFA) outperformed the conventional collector sodium oleate (referred to as SSO) by significantly increasing the recovery of total carbonates (TC) while simultaneously reducing acid insolubles (AI). A low-grade limestone feed containing 78.40 % TC and 20.90 % AI was upgraded through both mechanical and column flotation techniques. Mechanical flotation yielded a product with 92.9 % TC, 93.48 % TC recovery, 4.0 % AI, and 77.58 % yield at SSFA dosage of 0.87 kg/t. Column flotation, at the same dosage, yielded a product with slightly higher TC content (94.20 %), lower TC recovery (91.02 %), similar AI content (4.07 %), and slightly lower yield (74.68 %). The kinetics of the flotation process indicated that the limestone sample exhibited fast-floating behaviour, attributed to the enhanced selectivity of the SSFA collector. The bio-collector SSFA stands out as a promising and sustainable alternative to conventional collectors for large-scale low-grade limestone flotation due to its remarkable ability to selectively recover total carbonates while minimizing acid insolubles.

Green Synthesis, Characterization, and Evaluation of Photocatalytic and Antibacterial Activities of Co3O4-ZnO Nanocomposites Using Calpurnia aurea Leaf Extract.

The green synthesis of transition metal oxide nanocomposites using plant extracts is a new and effective method that avoids the involvement of hazardous chemicals. Nondegradable organic pollutants and antibiotic drug resistance have become serious public health issues worldwide. Hence, the main objective of this study is to synthesize Co3O4-ZnO nanocomposites using Calpurnia aurea leaf extract and evaluate its photocatalytic and antibacterial activities. The green synthesized particles were characterized using UV-vis spectra, Fourier transform infrared spectroscopy, X-ray diffraction techniques, and scanning electron microscopy combined with energy-dispersive X-ray studies. The synthesized particles were found to be crystalline in nature with average crystallite sizes of 23.82, 14.79, 15.99, 16.46, and 21.73 nm. Scanning electron microscopy shows the spherical morphology of Co3O4-ZnO NCs, and energy-dispersive X-ray analysis confirms the formation of highly pure ZnO NPs and Co3O4-ZnO NCs. The photocatalytic activity was performed under natural sunlight using malachite green as an organic dye pollutant. The green synthesized ZnO NPs, Co3O4 NPs, 1:4, 1:3, and 1:2 Co3O4-ZnO NCs showed high degradation efficiency after 60 min of irradiation. The synthetic material showed good potential against Staphylococcus aureus and Escherichia coli, with the highest growth inhibition recorded by 1:2 Co3O4-ZnO NCs. The kinetics study of the photocatalytic degradation was confirmed as pseudo first order, and the possible mechanisms for both photocatalytic and antibacterial activities were clearly determined.

Controlled release and antibacterial activity of corn starch-based films containing nanocellulose and thymol

The use of nanomaterials such as cellulose nanofiber (CNF) and antimicrobial compounds such as thymol (Thy), in starch films may improve the functional properties of films as active packaging films. This study quantifies the retention of thymol in corn starch (CS) and CS films containing cellulose nanofibers (CS/CNF) and investigates the migration of thymol from the films into a food simulant. A kinetic study was performed to evaluate the release of thymol from films into fatty acid food simulant (95% v/v ethanol) at 40 °C. The antibacterial activity of films was investigated via liquid culture assay. It was found that the addition of thymol significantly affects the surface morphology and cross-section of the films. CS/Thy and CS/CNF/Thy films retained thymol at 2.88 ± 0.50 and 11.21 ± 0.75 mg per g of CS/Thy and CS/CNF/Thy films, respectively. The release of thymol was affected by the presence of an intercalating network of CNF, which exhibited Fickian diffusion behavior. The release of thymol reached equilibrium within 48 h for CS/Thy, and 72 h for CS/CNF/Thy films. The CS/CNF/Thy film had a greater inhibitory effect than the CS/Thy film against Listeria monocytogenes and Salmonella Typhimurium. These findings demonstrate the potential applications of these films in improving the shelf life of perishable food products.

Nobody's Perfect: Choice of the Buffer and the Rate of Cu2+ Ion-Peptide Interaction.

The choice of correct pH buffer is crucial in chemical studies modeling biological processes involving Cu2+ ions. Popular buffers for physiological pH are known to form Cu(II) complexes, but their impact on kinetics of Cu(II) complexation has not been considered. We performed a stopped-flow kinetic study of Cu2+ ion interactions with four popular buffers (phosphate, Tris, HEPES, and MOPS) and two buffers considered as nonbinding (MES and PIPPS). Next, we studied their effects on the rate of Cu2+ reaction with Gly-Gly-His (GGH), a tripeptide modeling physiological Cu(II) sites, which we studied previously at conditions presumably excluding the buffer interference [Kotuniak, R.; Angew. Chem., Int. Ed. 2020, 59, 11234-11239]. We observed that (i) all tested pH 7.4 buffers formed Cu(II) complexes within the stopped-flow instrument dead time; (ii) Cu(II)-peptide complexes were formed via ternary complexes with the buffers; (iii) nevertheless, Good buffers affected the observed rate of Cu(II)-GGH complex formation only slightly; (iv) Tris was a competitive inhibitor of Cu(II)-GGH complexation; while (v) phosphate was a reaction catalyst. This is particularly important as phosphate is a biological buffer.

EDOT substitution site effect on fluorenone acceptor units: electrochemical polymerization and electrochromic properties of D-A systems

A series of donor-acceptor-donor type molecules (P(2,7-DEF) and P(3,6-DEF)) based on fluorenone acceptor units and 3,4-ethylenedioxythiophene (EDOT) donor units were successfully obtained by Stille coupling reaction in this work, and then generated their corresponding D-A polymers by electrodeposition method. As prepared P(2,7-DEF) and P(3,6-DEF) were characterized by CV, UV–vis spectroscopy, SEM, spectroelectrochemistry, and kinetic studies. Both of these two monomers revealed bright red/yellow light-emitting property in dilute solution. Since the π-conjugation length is longer, the oxidation potential of 2,7-DEF was reduced to 0.85 V, accompanied with red-shifted electronic spectra and emission spectra. The resulting P(2,7-DEF) demonstrated distinct electrochromic properties under various potentials with two different colors from dark-brown to blue-purple. Due to its more porous structure, P(2,7-DEF) also showed favorable optical contrast (26.3 %), very fast switching time (0.32 s), and decent coloration efficiency (221.25 cm2 C−1). However, P(3,6-DEF) displayed much worse electrochromic performances due to its bad electroactivity. P(2,7-DEF) also displayed better redox stability (remaining 79 % electroactivity after 1000 cycles), good optical stability (6 % reduction in optical contrast after 3200 s), and stable optical memory. From these results, P(2,7-DEF) can be further used as a promising near-infrared electrochromic materials.

Relative reactivity of methyl anisole isomers: An experimental and kinetic modelling study

Due to the current interest in biomass derived carbon neutral fuels and fuel additives for gasoline engines and to the growing need of understanding the fundamentals of gas phase combustion in the context of wildfires, this study investigates the combustion behavior of key components of biomass pyrolysis oils, namely the three methylanisole isomers (ortho-, meta- and para-methylanisole). Specifically, this study presents the first experimental ignition delay time measurements for such fuels using a shock tube and a rapid compression machine. Ignition experiments were carried out for stoichiometric fuel/air mixtures (φ = 1) at compressed pressure pc = 10 and 20 bar, covering a temperature range Tc = 880–1220 K. A kinetic model based on previous efforts in the area of oxygenated aromatic hydrocarbon fuels is proposed to reproduce and interpret the experimental findings, specifically focusing on capturing the observed different reactivity of the three isomers. To this aim, thermodynamic properties of primary intermediates and bond dissociation energies were calculated highlighting relevant differences originated from the relative position of the O–CH3 and –CH3 substituents. In addition, an isomerization pathway specific to the ortho isomer was theoretically investigated and found to motivate the observed higher reactivity with respect to the meta and para isomers

Advancing Nitrile-Aminothiol Strategy for Dual and Sequential Bioconjugation.

Nitrile-aminothiol conjugation (NATC) stands out as a promising biocompatible ligation technique due to its high chemo-selectivity. Herein we investigated the reactivity and substrate scope of NAT conjugation chemistry, thus developing a novel pH dependent orthogonal NATC as a valuable tool for chemical biology. The study of reaction kinetics elucidated that the combination of heteroaromatic nitrile and aminothiol groups led to the formation of an optimal bioorthogonal pairing, which is pH dependent. This pairing system was effectively utilized for sequential and dual conjugation. Subsequently, these rapid (≈1 h) and high yield (>90%) conjugation strategies were successfully applied to a broad range of complex biomolecules, including oligonucleotides, chelates, small molecules and peptides. The effectiveness of this conjugation chemistry was demonstrated by synthesizing a fluorescently labelled antimicrobial peptide-oligonucleotide complex as a dual conjugate to imaging in live cells. This first-of-its-kind sequential NATC approach unveils unprecedented opportunities in modern chemical biology, showcasing exceptional adaptability in rapidly creating structurally complex bioconjugates. Furthermore, the results highlight its potential for versatile applications across fundamental and translational biomedical research.

Hybrid photocatalytic/photochemical degradation of 1,2-dichlorobenzene: kinetic, thermodynamic, operating cost, synergism and mineralization study

Hybrid photocatalytic/photochemical degradation of 1,2-dichlorobenzene: kinetic, thermodynamic, operating cost, synergism and mineralization study

The monodomain Kunitz protein EgKU-7 from the dog tapeworm Echinococcus granulosus is a high-affinity trypsin inhibitor with two interaction sites.

Typical Kunitz proteins (I2 family of the MEROPS database, Kunitz-A family) are metazoan competitive inhibitors of serine peptidases that form tight complexes of 1:1 stoichiometry, mimicking substrates. The cestode Echinococcus granulosus, the dog tapeworm causing cystic echinococcosis in humans and livestock, encodes an expanded family of monodomain Kunitz proteins, some of which are secreted to the dog host interface. The Kunitz protein EgKU-7 contains, in addition to the Kunitz domain with the anti-peptidase loop comprising a critical arginine, a C-terminal extension of ∼20 amino acids. Kinetic, electrophoretic, and mass spectrometry studies using EgKU-7, a C-terminally truncated variant, and a mutant in which the critical arginine was substituted by alanine, show that EgKU-7 is a tight inhibitor of bovine and canine trypsins with the unusual property of possessing two instead of one site of interaction with the peptidases. One site resides in the anti-peptidase loop and is partially hydrolyzed by bovine but not canine trypsins, suggesting specificity for the target enzymes. The other site is located in the C-terminal extension. This extension can be hydrolyzed in a particular arginine by cationic bovine and canine trypsins but not by anionic canine trypsin. This is the first time to our knowledge that a monodomain Kunitz-A protein is reported to have two interaction sites with its target. Considering that putative orthologs of EgKU-7 are present in other cestodes, our finding unveils a novel piece in the repertoire of peptidase-inhibitor interactions and adds new notes to the evolutionary host-parasite concerto.