Endothermic Enthalpy Values Research Articles

Talaromyces aculeatus from acidic environment as a new fungal biosorbent for removal of some reactive textile dyes

Biosorption potential of Talaromayces aculeatus AMDC-14 (KF588645) as low-cost biosorbent for different dyes (Reactive Blue 13, Reactive Blue 72, Reactive Yellow 85 and Reactive Orange 13) removal from aqueous medium was studied. Experiments were performed to determine effect of initial solution pH (1-7), biosorbent dose (0.1-2.5 g L -1 ), time (15-1440 min), dye concentration (10-200 ppm) and temperature (25-40 °C) onto Talaromayces aculeatus biosorption . Biosorption equilibrium data were described very well for Reactive Blue 13, Reactive Blue 72, Reactive Yellow 85 and Reactive Orange 13 by Langmuir isotherm model than Freundlich isotherm model with maximum biosorption capacities which are 32.10, 71.30, 20.67 and 31.30 mg g -1 , respectively. Biosorption of investigated dyes fitted to kinetic model of pseudo-second-order for all dyes. Gibbs free energies (ΔG°) of biosorption processes were calculated and the results indicated that all selected dyes biosorption onto Talaromayces aculeatus AMDC-14 were spontaneous in this study. And also biosorption processes had endothermic enthalpy values except Reactive Blue 72.

Batch and continuous (fixed-bed column) biosorption of Cu(II) by Tamarindus indica fruit shell

The feasibility of employing Tamarindus indica (tamarind) fruit shell (TFS) as low-cost biosorbent for removal of Cu(II) from aqueous solutions was investigated. Batch experiments were carried out as function of initial solution pH (2–7), contact time (10–240 min), initial Cu(II) concentration (20–100 mg L−1), biosorbent dose (0.5–5 g) and temperature (293–313 K). Biosorption equilibrium data were well described by the Langmuir isotherm model with maximum biosorption capacity of 80.01 mg g−1 at 313 K. Biosorption of Cu(II) followed pseudo-second-order kinetics. Gibbs free energy (ΔG0) was spontaneous for all interactions, and the biosorption process exhibited endothermic enthalpy values. To ascertain the practical applicability of the biosorbent, fixed-bed column studies were also performed. The breakthrough time increased with increasing bed height and decreased with increasing flow rate. The Thomas model as well as the Bed Depth Service Time (BDST) model was fitted to the dynamic flow experimental data to determine the column kinetic parameters useful for designing large-scale column studies. The Thomas model showed good agreement with the experimental results at all the process parameters studied. It could be concluded that TFS may be used as an inexpensive and effective biosorbent without any treatment or any other modification for the removal of Cu(II) ions from aqueous solutions.

Batch Removal of Crystal Violet from Aqueous Solution by H2SO4 Modified Sugarcane Bagasse: Equilibrium, Kinetic, and Thermodynamic Profile

Batch adsorption studies were carried out using H2SO4 modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibb's free energy change (ΔG0) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.

Removal of safranin from aqueous solutions by NaOH‐treated rice husk: thermodynamics, kinetics and isosteric heat of adsorption

ABSTRACTSafranin is a widely used, cationic, azine synthetic dye, and because of various adverse properties any effluent streams require treatment prior to discharge. The correct disposal of synthetic dye wastewater after proper treatment is difficult because of the dye properties and their resistance to degradation processes. Adsorption is often an effective, economical and useful process for the treatment of dye effluents. The potential use of rice husk, a plentiful waste agricultural product, to remove safranin from aqueous solution by a batch adsorption process was evaluated. Rice husk was transformed into an effective adsorbent material by treating with sodium hydroxide (NaOH). During the treatment process, the effects of stirring rate, temperature, pH, initial dye concentration and sorbent dose were studied. The maximum dye adsorption was obtained at pH 8. The Langmuir isotherm model was a good representation of the equilibrium data, and the maximum monolayer adsorption capacity obtained was 37.97 mg g−1 at 303 K. The mean free energy (E) estimated from the Dubinin–Radushkevich (D–R) model indicated that the main mechanism governing the sorption process was chemical ion‐exchange. The kinetic data were shown to be represented by the pseudo‐second‐order model and the intraparticle diffusion model. The Arrhenius and Eyring equations were used to evaluate the activation parameters. The activation energy was estimated to be 46.57 kJ mol−1. Gibbs' free energy was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. The isosteric heat of adsorption, determined using the Clausius–Clapeyron equation, increased directly in relation to the surface loading showing its strong dependence on surface coverage. Results suggest that NaOH‐treated rice husk is a potential low‐cost adsorbent for safranin removal from aqueous solution. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.

Studies on sorption isotherm models of ion exchange modified acrylic fibers

AbstractThe sorption behavior, favorability, shape and thermodynamic parameters of Cu(II), Ni(II), Pb(II), and Fe(III) ions sorption onto the ion exchage acrylic fiber were studied by applying Langmuir, Freundlich, Dubinin‐Radushkevich and Redlich–Peterson models. Analytical studies from sorption isotherms proved that sorption process follows mono layer adsorption mechanism. Gibbs free energy was spontaneous for all interactions. The adsorption processes all exhibited endothermic enthalpy values and were accompanied by increasing in entropy. The activation energies for the sorption of metal ions on aminated acrylic fiber were at the same order of magnitude as the activation energy of ion exchange. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Crystallization Control of Thermal Stability and Morphology of Hen Egg White Lysozyme Crystals by Ionic Liquids

Ionic liquids (ILs) exhibit a variety of properties that make them attractive additives for biomaterials. 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim]BF(4)), 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl), 1-butyl-3-methylimidazolium bromide ([C(4)mim]Br), and 1,3-dimethylimidazolium iodine([bmim]I), as additives during lysozyme crystallization, were tested for their effects on the thermal stability and morphology of lysozyme crystals obtained. [C(4)mim]Cl was chosen to evaluate the effect of IL addition concentration on the thermal stability of lysozyme. It is shown that the characteristic peak temperature and endothermic enthalpy values (DeltaH) for denaturation increase with increasing addition concentration. As for the degradation, peak temperatures decrease, whereas endothermic enthalpy values markedly increase with the rise of [C(4)mim]Cl addition concentration. In the case of adding [C(4)mim]BF(4), [C(4)mim]Br, and [bmim]I, similar thermal behaviors of lysozyme crystals were observed. The effect of ILs on thermal behaviors of lysozyme can be attributed to enhancing crystal contacts, changing conformational stability, or interaction among molecules, as evidenced by difference in crystal growth morphology. This study is especially helpful in controlling the thermal stability of lysozyme crystals and in gaining initial insight into potential crystallization conditions for prescreening ILs that stabilize the protein and other macromolecule crystals.

Thermodynamic studies of the interaction at the solid/liquid interface between metal ions and cellulose modified with ethylenediamine

The chelate molecule, ethylenediamine, has been incorporated onto the surface of cellulose by sequential reaction of cellulose fibres with phosphorous oxychloride followed by the chelating agent. The modified material (CelNN) retained its fibrous nature and was shown to be efficient at adsorbing divalent metal cations from water by complexation. Adsorption isotherms were determined for suspensions of CelNN in metal ion solutions of different concentrations, and the data were adjusted to fit the modified Langmuir equation. The maximum numbers of moles of Cu 2+, Ni 2+ and Zn 2+ adsorbed per gram of modified cellulose were 1.64 × 10 −3, 5.25 × 10 −4 and 1.06 × 10 −3, respectively. The thermodynamic effects related to the adsorption of metal ion onto the cellulose surface were determined by calorimetric titration. Gibbs free energy was spontaneous for all interactions. The adsorption processes all exhibited endothermic enthalpy values and were accompanied by increases in entropy.