Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads (original) (raw)
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Sorption of chrysoidine by row cork and cork entrapped in calcium alginate beads
Arabian Journal of Chemistry, 2014
Azo-dyes, molecules characterised by the presence of the azo-group (-N‚N-), are widely used in textile, leather, rubber, plastic, and food industries. Water-soluble azo-dyes are greatly resistant to biodegradation, and are characterised by a high thermal and photo stability due to their complex structures. The release of these molecules into the environment is of crucial concern due to their toxic, mutagenic and carcinogenic characteristics. Biosorption has been demonstrated an effective method to remove pollutants from wastewaters thus solving ecological tasks, being a low cost process and the sorbent biodegradable. The main requirements of an efficient sorbent are thermal, chemical and mechanical stability, and rapid sorption.
Arabian Journal of Chemistry, 2014
A kinetic and thermodynamic study on the sorption ability of calcium alginate gel beads towards Pd(II) ion was made in aqueous solution at different pH and chloride concentrations. The experimental conditions adopted in the sorption experiments were established on the basis of a speciation study on the Pd 2+ -AA system in which all the side reactions, such as the hydrolysis of Pd(II), the protonation of alginate and the interactions of the ligand and the metal ion with ions of ionic medium were taken into account. In the pH range 2-5 and at chloride concentration in the range 0 6 C Cl À /mmol L À1 6 10 the gel beads showed good sorption ability towards Pd(II) ion as confirmed by kinetic and thermodynamic data calculated by a pseudo second order equation and using Langmuir and Freundlich models. The comparison between q e values related to the kinetics of Pd(II) sorption and Ca(II) release in solution by gel beads indicated that the ion exchange is one of the main sorption mechanisms of the sorbent material. Similarities were found between the trends of sequestering (% PdAA species, pL 0.5 ) and the sorption (q e , q max ) parameters as function of pH and chloride concentration. It confirms a close relation between the behaviour of alginate as sequestering agent for Pd(II) ion in aqueous solution and of calcium alginate gel beads as sorbent material for the removal of the metal ion. ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Chromium sorption on grape stalks encapsulated in calcium alginate beads
Environmental Chemistry Letters, 2006
A novel sorbent based on 2% grape stalk wastes encapsulated in calcium alginate beads was investigated for the removal of Cr(VI) and Cr(III) from aqueous solutions. The sorbent proved to be efficient for chromium removal in both hexavalent and trivalent forms from aqueous solution at pH 3.0. In binary mixtures, the presence in solution of one of the forms enhances the sorption of the other which results in an increase of the amount of total chromium removed. This study suggests that the proposed sorbent can be used for the removal of chromium from wastewaters through a cost-effective and environmentally friendly process.
A model to describe Cr(VI) kinetics biosorption
Journal of Hazardous Materials, 2010
Grape stalk Effect of pH Effect of temperature Box plots a b s t r a c t In this work, the effect of pH control on kinetics of Cr(VI) sorption onto grape stalks has been studied. A set of experiments were performed at a constant pH 3 ± 0.1 which was assured by means of a Programmable Logic Controller (PLC). In a second set of experiments the initial pH was adjusted to pH 3 and then pH was allowed to freely evolve during the sorption process. Both sets of experiments were carried out at different temperatures within the range 5-50 • C. Constant temperature was assured by water recirculation from a thermostatic bath. Results demonstrated that pH has high influence on kinetics only at the lowest temperatures studied. A model based on a complex reaction sequence which takes into account Cr(VI) sorption, reduction of Cr(VI) to Cr(III), sorption of the formed Cr(III) which includes the pH variation during the sorption process has been proposed to model Cr(VI) kinetics sorption onto grape stalk waste. Furthermore, the robustness of the model has been tested.
Chemical Speciation and Bioavailability, 2004
The removal of hexavalent chromium from aqueous solution using grape stalks wastes encapsulated in calcium alginate (GS-CA) beads was investigated. Cr(VI) sorption kinetics were evaluated as a function of chromium initial concentration and grape stalks (GS) content in the calcium alginate (CA) beads. The process follows pseudo second-order kinetics. Transport properties of hexavalent chromium on GS-CA beads was characterised by calculating chromium diffusion coefficient using the Linear Absorption Model (LAM). Langmuir isotherms, at pH 3.0 were used to describe sorption equilibrium data as a function of GS percentage in the CA beads. Maximum uptake obtained was 86.42 mmol of Cr(VI) per L of wet sorbent volume. Results indicated that both kinetic and equilibrium models describe adequately the adsorption process.
ISSN 2320-5407 International Journal of Advanced Research (2015), Volume 3, Issue 12, 586 – 597
2016
S.Suresha Application of Syzygium cumini seeds and BorassusFlabellifer Seeds Peels as biosorbents for removal of Acid Red YG dye from aqueous solution and textile industry wastewater were investigated. Batch experiments were carried out to determine the effect of pH, particle size, biosorbent dose, contact time and initial dye concentration and even characterization like FTIR and SEM along with desorption studies were also carried out. Maximum dye biosorption was achieved at pH 2.0 for Syzyguim cumini seeds (92.60 %) whereas biosorption for Borossus flabellifer seeds peels (86.04 %) was achieved at pH 3.0, particle size 212μm for both, biosorbent dose of 0.8 g/L for Syzygium cumini seeds and 1g/L for Borassus flabellifer seeds peels, contact time remained the same as 60 min and initial concentration of 50mg/L. The pseudo-second order and equilibrium biosorption data fitted well to Langmuir than Freundlich isotherm models for both the biosorbents. The biosorption results in this stud...
International Research Journal of Pure and Applied Chemistry
This study examines the removal of Cr6+ from aqueous solutions using unmodified and oxalic acid modified African yam bean (AYB) pod and groundnut (G’NUT) shell as adsorbents. The effects of time, pH, temperature, and metal ion concentration were investigated. The amount of metal ions adsorbed increased as the initial concentration increased; groundnut shell gave a better adsorption capacity. Maximum uptake was recorded at pH of 6.0 whereas uptake level decreased at pH greater than 6.0. Kinetic studies showed that the physisorption reaction rates could be described better by a pseudo-second order model with R2 values close to 1. Various thermodynamic parameters such as ∆Go, ∆So, and ∆Ho were calculated. The values obtained for ∆Go were all negative for both adsorbents; indicating that the sorption processes investigated was spontaneous. Findings showed that an increase in temperature results in a lower metal loading per unit weight of the adsorbents, suggesting exothermic nature of t...