scispace - formally typeset
Topic

Standard molar entropy

About: Standard molar entropy is a(n) research topic. Over the lifetime, 1586 publication(s) have been published within this topic receiving 29886 citation(s).
Papers
More filters

Journal ArticleDOI
Abstract: Oil palm fibre, an abundant agricultural by-product in Malaysia, was used to prepare activated carbon by physiochemical activation method. Adsorption isotherm of methylene blue onto the prepared activated carbon was determined by batch tests. The effects of various parameters such as contact time, initial methylene blue concentration and temperature were investigated, at solution pH of 6.5. The adsorption capacity was found to increase with increase in the three parameters studied. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. The equilibrium data were best represented by the Langmuir isotherm, with maximum monolayer adsorption capacity of 277.78 mg/g at 30 °C. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Various thermodynamic parameters such as standard enthalpy (Δ H °), standard entropy (Δ S °) and standard free energy (Δ G °) were evaluated. Oil palm fibre-based activated carbon was shown to be a promising material for adsorption of methylene blue from aqueous solutions.

654 citations


Journal ArticleDOI
01 Feb 2005-Water Research
TL;DR: Desorption studies reveal that Pb2+ can be easily removed from carbon Nanotubes by altering the pH values of the solution using both HCl and HNO3, indicating that carbon nanotubes are a promising absorbent for wastewater treatment.
Abstract: Adsorption thermodynamics of Pb2+ on carbon nanotubes has been studied at various temperatures of 280, 298 and 321 K and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0), have been obtained. A pseudo-second-order rate model has been employed to describe the kinetic adsorption processes. Desorption studies reveal that Pb2+ can be easily removed from carbon nanotubes by altering the pH values of the solution using both HCl and HNO3, indicating that carbon nanotubes are a promising absorbent for wastewater treatment.

609 citations


Journal ArticleDOI
Yunjin Yao1, Feifei Xu1, Ming Chen1, Zhongxiao Xu1, Zhiwen Zhu1 
TL;DR: Results suggested that the methylene blue adsorption on CNTs was a spontaneous and endothermic process.
Abstract: The effect of temperature on the equilibrium adsorption of methylene blue dye from aqueous solution using carbon nanotubes was investigated. The equilibrium adsorption data were analyzed using two widely applied isotherms: Langmuir and Freundlich. The results revealed that Langmuir isotherm fit the experimental results well. Kinetic analyses were conducted using pseudo-first and second-order models and the intraparticle diffusion model. The regression results showed that the adsorption kinetics were more accurately represented by pseudo-second-order model. The activation energy of system (Ea) was calculated as 18.54 kJ/mol. Standard free energy changes ( Δ G 0 ), standard enthalpy change ( Δ H 0 ), and standard entropy change ( Δ S 0 ) were calculated using adsorption equilibrium constants obtained from the Langmuir isotherm at different temperatures. All Δ G 0 values were negative; the Δ H 0 values and Δ S 0 values of CNTs were 7.29 kJ/mol and 64.6 J/mol K, respectively. Results suggested that the methylene blue adsorption on CNTs was a spontaneous and endothermic process.

602 citations


Journal ArticleDOI
TL;DR: Adsorption mechanism studies revealed that the process was complex and followed both surface adsorption and particle diffusion and the rate-controlling parameter and effective diffusion coefficient were determined using the Reichenberg plot.
Abstract: Adsorption of Cu(II) from aqueous solution onto H(3)PO(4)-activated carbon using rubber wood sawdust (RSAC) was investigated in a batch system. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as initial concentration, contact time, pH, and temperature. The optimal pH value for Cu(II) adsorption onto RSAC was found to be 6.0. Thermodynamic parameters such as standard Gibbs free energy (DeltaG(0)), standard enthalpy (DeltaH(0)), and standard entropy (DeltaS(0)) were evaluated by applying the Van't Hoff equation. The thermodynamics of Cu(II) adsorption onto RSAC indicates its spontaneous and exothermic nature. Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Langmuir isotherm fits the experimental data significantly better than the other isotherms. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The initial sorption rate, pseudo-first-order, pseudo-second-order, and intraparticle diffusion rate constants for different initial concentrations were evaluated and discussed. Adsorption mechanism studies revealed that the process was complex and followed both surface adsorption and particle diffusion. The rate-controlling parameter and effective diffusion coefficient were determined using the Reichenberg plot. It was found that the adsorption occurs through film diffusion at low concentrations and at higher concentration the particle diffusion becomes the rate-determining step.

502 citations


Journal ArticleDOI
Abstract: The adsorption of methyl orange onto multiwalled carbon nanotubes (MWCNTs) from aqueous solutions was studied, in which the influence of contact time, dosage, temperature, pH, and methyl orange concentration in the solution were investigated. The equilibrium adsorption data were analyzed using three common adsorption models: Langmuir, Freundlich and Temkin. The results revealed that Langmuir isotherm fit the experimental results well. Kinetic analyses were conducted using pseudo-first and second-order models and the intra-particle diffusion model. The regression results showed that the adsorption kinetics was more accurately represented by pseudo-second-order model. Values of activation parameters such as Standard free energy changes (ΔG0), standard enthalpy change (ΔH0), and standard entropy change (ΔS0) were calculated using adsorption equilibrium constants obtained from the Langmuir isotherm at different temperatures. All ΔG0 values were negative; the (ΔH0) values and (ΔS0) values of MWCNTs were 19.39 kJ/mol and 0.1015 kJ/mol K, respectively, indicating that the adsorption was feasible, spontaneous and endothermic process in nature.

354 citations


Network Information
Related Topics (5)
Enthalpy

21.3K papers, 467.3K citations

89% related
Molality

2.3K papers, 60.6K citations

88% related
Activity coefficient

6K papers, 132.9K citations

87% related
Equilibrium constant

11.9K papers, 297.1K citations

86% related
Standard enthalpy of formation

5.6K papers, 115.7K citations

86% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
202141
202055
201949
201857
201753

Top Attributes

Show by:

Topic's top 5 most impactful authors

Manuel A.V. Ribeiro da Silva

28 papers, 488 citations

K. T. Jacob

13 papers, 220 citations

Natalia N. Smirnova

12 papers, 72 citations

Juliana Boerio-Goates

10 papers, 348 citations

Gennady J. Kabo

10 papers, 153 citations