Kinetics Studies of Metallic Ions Adsorption by Immobilised Chitosan

Immobilised chitosan on glass plates was used as an adsorbent for metallic ions from aqueous solutions in a batch adsorption system. Experiments were carried out as a function of contact time and initial metallic ions concentration. The adsorption efficiency increased with increasing initial metallic ions concentration (5 – 20 mg L-1) and the observed trend was: Ag2+ > Cu2+ > Ni2+ > Fe3+ > Cd2+ > Zn2+. The experimental data were fitted to pseudo-first, pseudo-second-order, intra-particle, and liquid film diffusion kinetic models. The applicability of the pseudo-second-order kinetic model indicated that the adsorption behaviour was ascribed by chemisorption. Further data analysis by the diffusion kinetic models suggested that the metallic ions adsorption was controlled by more than one step; adsorption at the active sites, intra-particle, and liquid film diffusion.

Investigation of Fast-Charging and Degradation Processes in 3D Silicon–Graphite Anodes

The 3D battery concept applied on silicon–graphite electrodes (Si/C) has revealed a significant improvement of battery performances, including high-rate capability, cycle stability, and cell lifetime. 3D architectures provide free spaces for volume expansion as well as additional lithium diffusion pathways into the electrodes. Therefore, the cell degradation induced by the volume change of silicon as active material can be significantly reduced, and the high-rate capability can be achieved. In order to better understand the impact of 3D electrode architectures on rate capability and degradation process of the thick film silicon–graphite electrodes, we applied laser-induced breakdown spectroscopy (LIBS). A calibration curve was established that enables the quantitative determination of the elemental concentrations in the electrodes. The structured silicon–graphite electrode, which was lithiated by 1C, revealed a homogeneous lithium distribution within the entire electrode. In contrast, a lithium concentration gradient was observed on the unstructured electrode. The lithium concentration was reduced gradually from the top to the button of the electrode, which indicated an inhibited diffusion kinetic at high C-rates. In addition, the LIBS applied on a model electrode with micropillars revealed that the lithium-ions principally diffused along the contour of laser-generated structures into the electrodes at elevated C-rates. The rate capability and electrochemical degradation observed in lithium-ion cells can be correlated to lithium concentration profiles in the electrodes measured by LIBS.

Effect of Gamma Radiation on the Adsorption Capacity and Regeneration / Desorption of Sulphate and Phosphate Ions Using Smart Hydrogel.

Co-polymeric hydrogels containing poly (Acrylamide /Epichlorohydrine) P(AAm/EPI) with different acrylamide and Epichlorohydrine content were fabricated by gamma radiation at different irradiation doses as adsorbent materials for wastewater treatment. The mechanisms of radiation-induced crosslinking of hydrogel in aqueous solution has been evaluated. The gel contents and the swelling/diffusion kinetic parameters were evaluated at different irradiation doses, and the result confirm a non-fichian mechanism. The shape, surface morphology, and porosity of P (AAm/ Epi) hydrogel were characterized by scanning electron microscope (SEM). Adsorption experiments were carried out for the removal of sulphate and phosphate ions from wastewater using P(AAm/EPI) hydrogels as adsorbent materials. The isotherm data were analyzed by Freundlich equation. The equilibrium isotherm results show a better fitting (R2 > 0.9) to the Freundlich model for all anions. The calculated regeneration efficiency (%) values of sulphate and phosphate ions found to be ranged between 63.2 (%) and 46 (%).The relatively higher regeneration efficiency (%) and keeping the hydrogels its shape without any deformation promising to use the same hydrogels further times which decrease the economic cost.

Experimental Studies on the Removal of Aluminium Ions from Synthetic Aqueous Solution by Hydroxyapatites

In this work we have presented the results obtained in the adsorption behavior of hydroxyapatite with different treatment towards aluminium ions from synthetic wastewaters. Experiments were performed in batch technique at different pH values, temperatures, sorbent dosage, contact time and initial aluminium concentration. The thermodynamic studies on the adsorption process of aluminium onto hydroxyapatite indicated that the process is spontaneous and endothermic. The Langmuir, Freundlich, Flory-Huggins, Dubinin-Radushkevich and Temkin equilibrium models were applied to the description of experimental data. The adsorption of aluminium follows the Langmuir adsorption isotherm. The kinetics of adsorption was evaluated using the pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The rate of aluminium adsorption was successfully described by a pseudo-second-order kinetic model. The obtained results indicated that hydroxyapatite treated with Pluronic P123 surfactant has a higher sorption capacity toward aluminium ions (117.65 mg g−1) than hydroxyapatite treated with Pluronic F127 surfactant (109.89 mg g−1) while untreated hydroxyapatite exhibited the lowest one (104.17 mg g−1).

Carboxymethyl Cellulose Hydrogel Based Formulations of Zinc Hydroxide Nitrate-Sodium Dodecylsulphate-Bispyribac Nanocomposite: Advancements in Controlled Release Formulation of Herbicide

The usefulness of carboxymethyl cellulose (CMC) as a matrix material in enhancing the controlled release formulations of bispyribac (BP) herbicide from the interlayer gallery of zinc hydroxide nitratesodium dodecylsulphate–bispyribac (ZHN–SDS–BP) nanocomposite was investigated. The CMC coated nanocomposite, ZHN–SDS–BP–CMC was characterised using several instruments for the determination of its physicochemical properties. The release rates of the BP were measured using a UV spectrophotometer, and the aqueous solutions containing PO3−4 , SO2−4 and Cl− were selected as release media in the release studies so as to mimic the real conditions of environmental soil. Significant release time delays, triggered by the gelation forming ability and hygroscopic nature of CMC, were observed in all release media, and the release processes were found to behave in a concentration-dependent manner in all release media. Fitting the release data into several kinetic models demonstrated that release in aqueous solutions of Na3PO4 and Na2SO4 was governed by pseudo second order processes, whereas the release in an aqueous NaCl solution was governed by the parabolic diffusion kinetic model. The potential of CMC in prolonging the release of BP from ZHN–SDS–BP–CMC can potentially help in reducing the pollution resulting from the overuse of pesticides.

Constructing hierarchically porous MnO/C composite to induce diffusion kinetics for high-performance lithium-ion batteries

Hybridization with transition metal oxide is broadly realized as an attractive way to smash the capacity limitation of carbon-base materials upon lithium storage. However, the influence of metal ions on the fast reaction kinetics of the electrode is still a confusing topic. Herein, a common molten salt method is displayed to fabricate hierarchically porous MnO/carbon composites. The addition of LiCl and KCl induces the fluid reaction substance by forming molten salt at a high-temperatures to beneficially achieve the activation and breaking of the carbon particles. The abundant porous and homogeneou carbon skeletons validly raise the ion/electron diffusion and transferability to prevent MnO particles from agglomerating, thereby inducing the diffusion kinetic. Moreover, the hierarchical porous MnO/carbon composite offers a highly invertible capacity of 851 mAh g-1 at 0.1 A g-1 and outstanding cyclic performance. This work has opened up a path for metal oxidation/carbon composite materials in electrochemical energy storage.

Application of Titanium Dioxide for Zirconium Ions Adsorption and Separation from a Multicomponent Mixture

This work studies the adsorption of zirconium ions by mesoporous titanium dioxide and by sodium-modified mesoporous titanium dioxide. Experimental maximal adsorption values of zirconium ions by H-TiO2 and Na-TiO2 were found to be 64 mg/g and 109,5 mg/g respectively. This process depends on the interaction time, equilibrium concentration of zirconium ions and acidity of the solution. Adsorption kinetics fit well into the diffusion kinetic model and indicate a several stages of zirconium ions adsorption. Equilibrium adsorption of zirconium ions is well described by the Langmuir's adsorption theory for both adsorbents. The results obtained by inductively coupled plasma mass spectrometry showed that the investigated adsorbent selectively adsorb zirconium ions from the mixture with strontium and yttrium ions in the range of solution pH = 0-1. The percentage of maximum extraction of zirconium ions is 86,61% for H-TiO2 and 94,11% for Na-TiO2. This fact is extremely valuable for nuclear forensics or for the determination of 90Sr in low activity background samples.

Microstructure Development of an Electroplating Coated Nickel-Base SC Superalloy in Oxidation Processes—Simulation Results

In this paper; a diffusion kinetic model was applied to simulate the microstructure development in a MCrAlY-superalloy system at high temperatures. Both simulation and experimental results showed that γ+γ’ microstructure was obtained in the coatings due to Al depletion after oxidation. With the help of the modelling; the mechanism of the formation of the diffusion zones in the single crystal (SC) superalloy can be also analyzed. The results revealed that the inward diffusion of Al from coating affected the depth of secondary reaction zone (SRZ) with the precipitation of TCP phases while the depth of inter-diffusion zone (IDZ) was decided by the inward diffusion of Cr.