Effect Of Chemical Activation Research Articles

Effects of Fly Ash Particle Size and Chemical Activators on the Hydration of High-Volume Fly Ash Mortars

This study investigated the effects of the fly ash (FA) particle size and chemical activators on the hydration reactions of high-volume fly ash (HVFA) cement pastes and the mechanical properties of HVFA mortars, with five types of FA with varying proportions of particles smaller than 10 μm prepared to assess the influence of particle size. In addition, the effect of chemical admixtures on the early-age hydration of the HVFA cement paste was evaluated. Quartz powder with the same fineness as that of normal FA was prepared to specifically examine the pozzolanic reaction of FA. The hydration reactions of the HVFA cement pastes were analyzed using isothermal calorimetry to measure the heat of hydration for 72 h. The results showed that an increase in the contents of FA particles with a diameter lower than 10 μm increases specific heat flow. Chemical activators, including Na2SO4, triethanolamine (TEA), and triisopropanolamine (TIPA), promote early-age hydration of HVFA cement pastes. The mechanical properties of the HVFA mortar were evaluated by measuring its compressive strength at 3 d, 7 d, and 28 d, with the findings revealing that the compressive strength of HVFA mortar improved with an increased proportion of FA particles smaller than 10 μm. Na2SO4, TEA, and TIPA consistently increased the compressive strength of the HVFA mortars.

Influence of MgO chemical activity on the drying shrinkage of the MgO-SiO2-H2O system

The magnesium silicate hydrate (MgO-SiO2-H2O) system is an innovative eco-friendly cementitious material. However, its poor volume stability and significant shrinkage have curtailed its widespread development and utilization. The primary component for preparing the MgO-SiO2-H2O system, MgO, has a substantial impact on the properties, particularly in relation to volume stability. This research examined the effects of MgO chemical activity on the volume stability of the system. The results suggested that reducing MgO chemical activity and increasing the Mg/Si ratio result in varying reductions in the water loss ratio and drying shrinkage, with the lowest drying shrinkage ratio being 0.913 %, representing a 14.1 % reduction compared to the sample with the highest drying shrinkage ratio. MgO chemical activity affected the shrinkage deformation of the system by influencing the generation rate and content of Mg(OH)2-induced volume expansion. Additionally, the increase in the Mg/Si ratio influenced the content of Mg(OH)2, ultimately reducing drying shrinkage. At an Mg/Si ratio of 1.25, the resulting M-S-H gel resembled a T:O structure, and promoted a higher degree of polymerization of the gel. In contrast, when the Mg/Si ratio is 1.00, the M-S-H gel exhibited characteristics more akin to a T:O:T structure, leading to an even higher degree of polymerization.

Fragrance Carrier Based on Zeolite-A Modified Bentonite as a Controlled Release System in Air Freshener Applications

The quality of air fresheners with low cost production can be improved by using a carrier matrix such as synthetic zeolite to increase the long-lasting properties of fragrance product by encapsulation technique. The zeolite A is considerdas a safe core fragrance carrier matrix to be able to release volatile fragrance from their pores when exposed to atmospheric humidity at room temperature. Zeolite A was synthesized from natural kaolin and was formed into tube pellets with bentonite (20 wt.%) as binder to produce zeolite A-bentonite (ZAB) cylindrical pellets composite and used as a fragrance carrier matrix with a rose essential oil (Rose damascena Mill.) as parfume model. The fresh bentonite can also adsorb the rose essential oil with adsorption capacity of 1.745 g/g bentonite (74.5%). Effects of chemical activation on zeolite-A using acid (HCl) of 0.1 M and base (NaOH) of 0.1 M were studied. The ZAB tube pelletes were found to have high adsorption efficiencies of rose essential oil. ZAB4 has the highest efficiency and was used for regeneration test studies that was carried out over 10 cycles using HCl and NaOH, where the adsorption efficiency was 94.5 and 75.4%, respectively. The activated ZAB4 composite using HCl has a long life time until more than 5 weeks and more than 10 regeneration cycles. This fragrance carrier matrix based on ZAB has significant potential for extended carrier fragrance system.

Enhancing biochar production: A technical analysis of the combined influence of chemical activation (KOH and NaOH) and pyrolysis atmospheres (N2/CO2) on yields and properties of rice husk-derived biochar

The production of biochar from biomass has received considerable interest due to its potential in environmental applications; however, optimizing biochar properties remains a major challenge. The objective of the present study was to investigate the synergistic effects of pyrolysis atmospheres (N2 and CO2) and chemical activation (pre- and post-pyrolysis) with NaOH and KOH on the properties of biochar useful for its environmental applications. In this study rice husk and biochar were impregnated with KOH and NaOH before and after pyrolysis, which was carried out at 600 °C under N₂ and CO₂ atmosphere. The pyrolytic yields (biochar, liquid and gas) and detailed characterization of biochar were performed. The results showed that pre-activation with both alkalis under a CO2 atmosphere slightly decreased the biochar yield and carbon contents while increasing oxygen in biochars compared to N2 atmosphere. Alkali pre-activation in the CO2 atmosphere considerably increased the specific surface area and pore volume of biochars compared to the N2 atmosphere, with KOH being more effective than NaOH. The maximum specific surface area (SSA) and pore volume (PV) of biochar obtained were 178.4 m2/g and 0.60 cm3/g for KOH activated biochar under CO2, which were 3.2 times and 30 times higher than the untreated biochar. The post-activation of biochars with both alkalis resulted in moderate improvements in textural properties. Overall, chemical activation under CO2 pyrolysis facilitated a higher level of chemical activation reactions leading to increased formation of oxygen functional groups and contributed to enhanced SSA and PV of the biochar useful for adsorption.

Porous nitrogen-doped carbons derived from poultry feathers for electrochemical capacitors

The synthesis of a nitrogen doped carbon material (NDCM) from the ball-milling and chemical activation of high temperature carbonised waste chicken feathers is reported. Synthesised NDCMs with nitrogen content ranging from 2.2 to 6.6 wt% were analysed via a range of physio and electrochemical characterisation methods. The effects of carbonisation temperature, mechanical milling and chemical activation were evaluated on specific capacitance and charge retention. Electrochemical testing demonstrated that the optimised NDCM (carbonised at 700 °C followed by ball milling and chemical activation) possessed a specific capacitance of 195 F g−1 at 1 A g−1 current density. At the higher current density of 40 A g−1 89 % of the capacitance is retained. Moreover, this material showed a cycle life of 1000 galvanostatic charge/discharge cycles with a 1 % loss in capacitance at a current density of 5 A g−1.

INFLUENCE OF MECHANICAL ACTIVATION ON THE PROPERTIES OF CEMENT-WATER COMPOSITIONS WITH THE ADDITION OF GROUND LIMESTONE

The paper considers the issue related to determining the effect of mechanical activation of a mineral binder on the properties of both hardening and hardened cement-water compositions. The mechanical activation of cement in combination with the consumption of ground limestone, the amount of which was adjusted in the range from 0 to 40 % of the cement mass, is relevant for this study. The effect of mechanical chemical activation of Portland cement only and Portland cement with the addition of 20 and 40 % ground limestone on changing the water-solid ratio of equiviscous compositions was studied. It was shown that mechanical and chemical activation of a cement-water composition has a positive effect on reducing the W/S ratio of equiviscous compositions from 0.42 (no activation) to 0.38 (activation period 180 sec). The obtained experimental results indicate the presence of an induction period of heating of the cement paste both on Portland cement not subject to mechanical activation (this period is approximately 6 hours from the moment of interaction of cement with water) and on Portland cement subject to mechanical activation. In this case, the induction period was no more than 2 hours. Joint mechanical activation of an aqueous mixture of Portland cement and ground limestone ensures acceleration of the hydration processes of the binder, which is confirmed by the intensification of the exothermic heating of the filled cement-mixing compositions. The positive role of mechanical activation is also reflected in the acceleration of the thickening rate of the compositions, which was recorded by the kinetics of the decrease in the diameter of their spread over time. The positive role of mechanical activation in reducing the effective viscosity of cement-containing compositions is confirmed, which ensures a decrease in their water-solid ratio by an average of ‒ 8 ... 10 %. A positive effect of mechanochemical activation of Portland cement with the addition of ground limestone on the strength of cement stone at the age of 3 days has been revealed. Experimental studies indicate that only due to mechanical activation the strength of samples made of cement stone with the addition of ground limestone can be increased by almost 25...30 %.

Chemical Activation Boosted Interface Interaction between Poly(tetrafluoroethylene-co-hexafluoropropylene) Film and Silver Coating.

To enhance the interfacial adhesion between poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film and functional coatings, such as silver (Ag) coating, among others, the surface activation of FEP film has to be performed. Among various activation strategies, chemical activation, such as using naphthalene sodium system, is one of the most efficient methods. However, the effect of chemical activation on the interface interaction between the activated FEP and functional coating is rarely investigated. Herein, the FEP film was activated by naphthalene sodium solution under different conditions, and then the Ag layer was coated onto its surface by vacuum Ag deposition. Based on experimental results and density function theory (DFT) calculation, it is indicated that oxygen-containing functional groups (such as C=O and C-OH groups), introduced onto the surface of FEP by the chemical activation, play a key role in boosting the interface interaction, which is due to the strong interaction between the oxygen-containing functional groups and Ag atoms. In addition, the concentration of naphthalene sodium solution, activation time, and winding speed of Ag- deposition can have a significant impact on the microstructures of Ag coating and the interfacial adhesion between the activated FEP and Ag coating. Under the conditions of high concentration (0.9 M), medium activation time (15 min), and high winding speed (0.8 m min-1), there is the best interface adhesion.

Study On Mechanical Properties Of Cemented Paste Backfill Using Fly-Ash-Based Cementitious Materials

In Mongolia, the Ulan lead-zinc mine is now struggling with high backfill operating costs and poor Cemented Paste Backfill (CPB) mechanical performance after curing. To solve this problem, BGRIMM Technology Group has investigated an activator that could mix with fly ash from Choibalsan Power Plant in Mongolia as a supplementary cementitious material for backfill. In this study, the mechanical performance of CPB samples prepared with various fly ash content and activator types were studied to provide a basis for the industrial application of fly ash-based supplementary cementitious materials. The research results indicate that partially replacing cement with fly ash reduces the uniaxial compressive strength (UCS) of CPB samples. Compared with the CPB sample prepared with pure cement, when the fly ash substitution rate is 10%, 20%, and 30%, the UCS reduced by 15.66%, 18.69%, and 32.83%, respectively. With the use of chemical activators, the UCS of CPB samples could be significantly improved. Among them, CPB samples prepared by the activator sodium sulfate+ sodium chloride+ TEA have achieved the highest UCS. Overall, this study shows that the synergistic effect of fly ash and chemical activators could effectively enhance the mechanical performance of CPB, which is beneficial for mine backfill cost reduction and could provide a basis for the further industrial application of fly ash-based cementitious materials in mine backfill.

Simultaneous effect of thermal and chemical activation on novel argan pulp-derived activated carbon for high-performance supercapacitors

In this paper, we offer new porous activated carbons (PACs) made from waste Argan pulp for use in solid-state supercapacitors. The synthesis is a two-step process of carbonization and KOH activation, with temperatures ranging from 700 to 850 °C and ratios ranging from 1:3 to 1:4. The carbon material obtained exhibits a significant surface area ranging from 2757 to 3235 m2 g−1. The evaluation of electrochemical characteristics in a two-electrode system using a 1 M H2SO4 electrolyte reveals exceptional capacitance and specific energy when subjected to a current density of 125 mAg-1. The AP-800-3 has outstanding performance, with a specific capacitance of 460 F g−1 and a specific energy of 15.98 Wh kg−1. Significantly, this particular PAC has exceptional durability in cycling, as it maintains its full specific capacitance even after undergoing 2500 charge and discharge cycles at a rate of 1 A.g−1. When testing with 6 M KOH and 1 M Na2SO4 electrolytes, the capacitance is found to be lower compared to 1 M H2SO4 (239 F g−1 and 258 F g−1, respectively). The superior performance in 1 M H2SO4 emphasizes the interplay between electrolyte composition, porosity, and appropriate microstructure of the PACs. This study proposes eco-friendly method for selecting supercapacitor electrode materials.

Advances in Carbon Xerogels: Structural Optimization for Enhanced EDLC Performance.

This review explores the recent progress on carbon xerogels (CXs) and highlights their development and use as efficient electrodes in organic electric double-layer capacitors (EDLCs). In addition, this work examines how the adjustment of synthesis parameters, such as pH, polymerization duration, and the reactant-to-catalyst ratio, crucially affects the structure and electrochemical properties of xerogels. The adaptability of xerogels in terms of modification of their porosity and structure plays a vital role in the improvement of EDLC applications as it directly influences the interaction between electrolyte ions and the electrode surface, which is a key factor in determining EDLC performance. The review further discusses the substantial effects of chemical activation with KOH on the improvement of the porous structure and specific surface area, which leads to notable electrochemical enhancements. This structural control facilitates improvement in ion transport and storage, which are essential for efficient EDLC charge-discharge (C-D) cycles. Compared with commercial activated carbons for EDLC electrodes, CXs attract interest for their superior surface area, lower electrical resistance, and stable performance across diverse C-D rates, which underscore their promising potential in EDLC applications. This in-depth review not only summarizes the advancements in CX research but also highlights their potential to expand and improve EDLC applications and demonstrate the critical role of their tunable porosity and structure in the evolution of next-generation energy storage systems.

Molecular Docking and ADMET Profiling of Pimenta Dioica Bioactives: Targeting Carboxylesterase 1

ABSTRACT The study explored the chemical composition, antioxidant activity, and potential antihyperlipidemic effects of Allspice (Pimenta dioica) leaf essential oil. The oil yield from hydro-distillation was 1.61 ± 0.35% (v/w), with major compounds identified by GC-MS analysis as eugenol (72.06 ± 3.93%), β-pinene (9.29 ± 3.33%), chavicol (6.95 ± 0.6%), limonene (3.05 ± 0.71%), and 3-octenol (1.55 ± 1.07%). The oil’s antioxidant activity (426 ± 3.5 mg TE g−1) was attributed to polyphenols. It also reduced porcine pancreatic lipase activity, suggesting potential in managing dietary lipids. Molecular docking showed strong binding to CES1, with eugenol, limonene, β-pinene, and octenol outperforming the control (probucol). ADME-Tox predictions indicated favorable pharmacological profiles with controlled lipophilicity and toxicity.

From scraps to purification: innovative use of food waste-derived hydrochar in eradicating pharmaceutical pollutants.

Chemical products (CPs) such as carbamazepine and naproxen, present in aquatic environments, pose significant risks to both aquatic life and human health. This study investigated the use of hydrothermally carbonized food waste-derived hydrochar (AC-HTC) at three distinct temperatures (200, 250, and 300°C) as an adsorbent to remove these CPs from water. Our research focused on the impact of hydrothermal carbonization temperature on hydrochar properties and the effects of chemical activation with phosphoric acid on adsorption capacity. Hydrothermal carbonization increased the hydrochar's surface area from 1.47 to 7.52 m2/g, which was further enhanced to 32.81 m2/g after activation with phosphoric acid. Batch adsorption experiments revealed that hydrochar produced at 250°C (AC-HTC-250) demonstrated high adsorption capacities of 49.10mg/g for carbamazepine and 14.35mg/g for naproxen, outperforming several conventional adsorbents. Optimal adsorption occurred at pH 4, aligning well with the Langmuir and pseudo-first-order models. The hydrochar showed potential for regeneration and multiple uses, suggesting its applicability in sustainable wastewater treatment. Future research will explore scalability and effectiveness against a broader range of pollutants.

Banana Peel Adsorbent to Reduce the Concentration of Lead and Cadmium Metal Pollution in Landfill Leachate

Banana peels can be a valuable adsorbent for reducing heavy metals in water. This study investigated the effect of chemical activators on Nipah banana peel (Musa acuminata balbisiana) on their ability to reduce Pb and Cd metals in landfill leachate. Before the adsorption test, the banana peels were treated with a different chemical activator, including detergent, NaOH, KOH, and H3PO4. The results showed that H3PO4 adsorbs relatively high amounts of metals (Pb-75.800%, Cd-18.491%) in landfill leachate among these activators. FTIR analysis showed that banana peels treated with H3PO4 produced sharper carbonyl or carboxyl group peaks. These groups are very influential in the metal adsorption process. SEM-EDS analysis of the H3PO4-treated banana peels showed an increase in carbon and oxygen elements in the banana peels and changes in the pore surface that enhanced the adsorption process on Pb and Cd metals. From this study, banana peels activated with H3PO4 showed great potential to be developed into adsorbents to reduce heavy metal concentration.

Effect of chemical activators after intracytoplasmic sperm injection (ICSI) on embryo development in alpacas

Low motility and low sperm concentration are characteristics of alpaca semen. Thus, the intracytoplasmic sperm injection (ICSI) technique represents an alternative to improve the reproductive capacity of the male. However, the effect of post-ICSI activation in alpaca is not yet known. The aim of the present study was to compare the effect of chemical activators on alpaca embryo development after ICSI. Alpaca ovaries were collected from a local slaughterhouse and transported to the laboratory. Category I, II and III oocytes were matured for 30 h at 38.5 °C. After ICSI, injected oocytes were randomly divided and activated as follows: i) 5 μM ionomycin for 5 min, ii) 7% ethanol for 4 min, iii) 5 μM ionomycin for 5 min, window period 3 h plus 7% ethanol for 4 min, iv) 5 μM ionomycin for 5 min, window period 3 h, a second ionomycin treatment for 5 min, followed by 1.9 mM 6-DMAP for 3 h, v) 10 mM SrCl2 for 3 h. Culture was carried out for 5 days in SOFaa at 38.5 °C. The cleavage rate was the lowest in the SrCl2 group, morula development was the lowest in the SrCl2 and without activation groups, and blastocyst stage was not different between groups (P<0.05). The rates with SrCl2 were lower in total embryos produced, whereas in transferable embryos they were lower with 2Io/6-DMAP and with SrCl2 (P<0.05). In conclusion, alpaca oocyte activation is more efficient with ionomycin and ethanol to produce transferable embryos.

The mineral phase evolution characteristics and hydration activity enhancement mechanism of steel slag under NaOH alkaline excitation

During the slow cooling process of steel slag, crystals of the inert ore phase (C2F) and active ore phase (C2S, C3S) grow dependently, and the irregular interlacement and coating between ore phases strongly affect the hydration activity of the active ore phase in steel slag. Therefore, in this article, a typical alkaline activator, NaOH, was selected, the solvent type and concentration were optimized, and the etching behavior and mechanism of action of the NaOH alkaline activator on the surface of steel slag particles were clarified by analyzing the mineral phase composition, microstructure, particle size distribution, and pore structure evolution characteristics under alkaline excitation. In addition, the water hydration products, microstructure, exothermic hydration and thermogravimetric data before and after the excitation of steel slag were characterized, revealing the mechanism of enhancing the hydration activity of steel slag under alkaline NaOH stimulation. The results showed that both NaOH aqueous solution and ethanol solution could effectively increase the mass fraction of active mineral phases in steel slag; among them, the 0.08 mol/L NaOH ethanol solution had the best chemical activation effect on the steel slag. Compared with that of the raw steel slag, the total mass fraction of the active mineral phases (C2S and C3S) increased from 37.3 wt% to 45.6 wt%, and the mass fraction of the inert mineral phase C2F decreased from 38.3 wt% to 19.1 wt%. The consumption of active mineral phases in steel slag is reduced by the water in the activator. The alkaline activator erodes the dense inert mineral phase C2F on the surface of the steel slag particles, resulting in etching pits that expose the active silicate mineral phase and provide additional hydration sites. The cumulative heat release from the steel slag after alkaline excitation was 116.27 J/g at 72 h, which was 66.88 J/g higher than that of the raw steel slag. These conditions significantly improved the early hydration performance of the steel slag and promoted the formation of amorphous cementitious products (CH, C-S-H and AFt) in the steel slag system, which subsequently filled the capillary pores of the steel slag and formed a denser microstructure.

Novel porphyrin derivative containing cations as new photodynamic antimicrobial agent with high efficiency.

Bacterial infections from chronic wounds affect about 175 million people each year and are a significant clinical problem. Through the integration of photodynamic therapy (PDT) and chemotherapy, a new photosensitizer consisting of ammonium salt N,N-bis-(2-hydroxyethyl)-N-(6-(4-(10,15,20-trimesitylporphyrin-5-yl) phenoxy) hexane)-N-methanaminium bromide, TMP(+) was successfully synthesized with a total reaction yield of 10%. The novel photosensitizer consists of two parts, a porphyrin photosensitizer part and a quaternary ammonium salt part, to achieve the synergistic effect of photodynamic and chemical antibacterial activity. With the increase of TMP(+) concentration, the diameter of the PCT fiber membranes (POL/COL/TMP(+); POL, polycaprolactone; COL, collagen) gradually increased, which was caused by the charge of the quaternary ammonium salt. At the same time, the antibacterial properties were gradually improved. We finally selected the PCT 0.5% group for the antibacterial experiment, with excellent performance in fiber uniformity, hydrophobicity and biosafety. The antibacterial experiment showed that the modified porphyrin TMP(+) had a better antibacterial effect than others. In vivo chronic wound healing experiments proved that the antibacterial and anti-inflammatory effect of the PCTL group was the best, further confirmed by H&E histological analysis, immunofluorescence and immunohistochemistry mechanism experiments. This research lays the foundation for the manufacture of novel molecules that combine chemical and photodynamic strategies.

Green Synthesis Nanopartikel Karbon Aktif dari Limbah Tempurung Kelapa

Activated carbon from coconut shell waste is a porous solid that has a large surface area with high absorption capacity, making it an alternative for reducing levels of heavy metal ions in the air. Active carbon is made by carbonization and chemical activation, then SEM testing is carried out to see the morphology of the activated carbon and analyzed using ImageJ software. This research aims to determine the effect of chemical activation and no activation on the number of pores formed in activated carbon. From the results of research that has been carried out, there are more pores formed after carbon is activated compared to carbon without activation. This is because the carbon surface without activation is still covered by impurities. In addition, unactivated carbon and activated carbon from coconut shells have pore sizes that fall into the mesoporous category.

Exploring the synergistic effects of chemical activation and N-doping in carbon nanospheres for advanced Li–CO2Mars batteries

Lithium-CO2 batteries can be used to mitigate CO2 emissions by recycling CO2 for energy storage and potential utilization as a standalone energy storage device on Mars as it contains 95 % CO2 (Li–CO2Mars batteries). The incomplete decomposition of the discharge product, Li2CO3, reduces the battery's cycle life, limiting its practicability. Herein, we develop a hierarchical porous, high surface area (1845 m2 g−1) activated N-doped candle soot (ANCS) carbon catalyst by modifying the candle soot carbon through the combination of the techniques of activation and hereroatom N-doping for enhanced CO2 reduction and evolution reactions. The ANCS-based Li–CO2Mars batteries exhibit a high discharge capacity of 11,490 mAh g−1 and a stable cycle life of over 130 cycles with a low overpotential of 1.4 V at the high current density of 200 mA g−1. Furthermore, density functional theory (DFT) studies reveal that the ANCS catalyst's higher affinity for CO2 adsorption and Li2CO3 production leads to the excellent performance of the Li–CO2Mars batteries. The developed method offers way of repurposing the pollutant carbons as metal-free carbon catalysts for the future progress of the Li–CO2Mars batteries for use as a future sustainable energy source for both Earth and Mars.

Adsorption of bisphenol a from aqueous solutions by activated tyre pyrolysis char – Effect of physical and chemical activation

Adsorption of bisphenol a from aqueous solutions by activated tyre pyrolysis char – Effect of physical and chemical activation

Assessing the effects of a mixture of hydrophobic contaminants on the algae Rhodomonas salina using the chemical activity concept

The production and release of chemicals from human activities are on the rise. Understanding how the aquatic environment is affected by the presence of an unknown number of chemicals is lacking. We employed the chemical activity concept to assess the combined effects of hydrophobic organic contaminants on the phytoplankton species Rodomonas salina. Chemical activity is additive, and refers to the relative saturation of a chemical in the studied matrix. The growth of R. salina was affected by chemical activity, following a chemical activity-response curve, resulting in an Ea50 value of 0.078, which falls within the baseline toxicity range observed in earlier studies. The chlorophyll a content exhibited both increases and decreases with rising chemical activity, with the increase possibly linked to an antioxidant mechanism. Yet, growth inhibition provided more sensitive and robust responses compared to photosynthesis-related endpoints; all measured endpoints correlated with increased chemical activity. Growth inhibition is an ecologically relevant endpoint and integrates thermodynamic principles such as membrane disruption. Our study utilized passive dosing, enabling us to control exposure and determine activities in both the medium and the algae. The concept of chemical activity and our results can be extended to other neutral chemical groups as effects of chemical activity remain independent of the mixture composition.