Surface charge and permeable gel descriptions of the ionic strength influence on proton binding to seaweed biomass

In recent years, there has been a significant increase in the studies concerning brown seaweed as biosorbents for metal removal owing to their high binding ability and low cost. This work reports the results of a study regarding the cadmium binding equilibria of dead biomass from the seaweed Sargassum muticum; this alga is a pest fouling organism that competes with the local fucalean species and may also interfere with the "sea industry"; therefore, it would constitute an ideal material to be used as biosorbent. Seven different treatments were tested in order to obtain a stable biomass that could be suitable for industrial use under a broad range of operational conditions. The treatments employed were protonation, chemical cross-linking with formaldehyde, KOH, Ca(OH)(2) and CaCl(2) or physical treatments with acetone and methanol. The equilibrium adsorption isotherms of Langmuir, Freundlich, and Langmuir-Freundlich were obtained for the quantitative description of the cadmium uptake. The effect of pH on biosorption equilibrium was studied at values ranging from 1 to 6, demonstrating the importance of this parameter for an accurate evaluation of the biosorption process. Maximum biosorption was found pH higher than 4.5. The maximum biosorption uptake for the raw biomass was 65 mg g(-1), while for formaldehyde cross-linking biomass the uptake increases to 99 mg g(-1) and for protonated biomass to 95 mg g(-1). Potentiometric titrations were carried out to estimate the total number of weak acid groups and to obtain their apparent pK value, 3.85, using the Katchalsky model. Kinetic studies varying cadmium concentration, algal dose, and ionic strength were carried out. Over 95% of the maximum cadmium uptake was achieved within 45 min, so the process can be considered relatively fast. A pseudo-second-order model, for the kinetics of cadmium biosorption, was shown to be able to reproduce experimental data points with accuracy.

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“…Moreover, surface charge models also reproduced with similar accuracy experimental equilibrium data (Rey-Castro et al, 2004b).…”

Section: Acid -Base Propertiessupporting

confidence: 57%

Physicochemical studies of Cadmium(II) biosorption by the invasive alga in Europe, Sargassum muticum

Lodeiro

Cordero

Grille

et al. 2004

Biotech & Bioengineering

121

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“…This effect was previously studied for protons [9,12]. The study for cadmium will be undertaken in future work.…”

Section: Modelsmentioning

confidence: 89%

Biosorption of cadmium by the protonated macroalga Sargassum muticum: Binding analysis with a nonideal, competitive, and thermodynamically consistent adsorption (NICCA) model

Lodeiro

Rey-Castro

Barriada

et al. 2005

Journal of Colloid and Interface Science

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Protonated biomass of the seaweed Sargassum muticum was investigated for its ability to remove cadmium(II) from aqueous solutions. In this work, a nonideal, semiempirical, thermodynamically consistent (NICCA) isotherm was proposed to fit the experimental ion binding data obtained in NaNO3 0.05 mol L(-1). This model describes the competition between protons and metal ions satisfactorily. Moreover, it reflects the complexity of the macromolecular systems that take part in biosorption considering the heterogeneity of the sorbent. It was demonstrated in this work that the NICCA isotherm constitutes a great improvement with respect to a simpler Langmuir competitive equation, which was not able to describe all the experimental data satisfactorily. Potentiometric acid-base titrations in the absence of cadmium were made to estimate the maximum amount of acid functional groups (2.61 mmol g(-1)) and the conditional proton binding parameters, logK (H) (3.8) and m(H) (0.54). The values of the binding parameters for the cadmium ion were chosen to provide the best simultaneous description of the isotherm at pH 4.5, as well as the dependence of cadmium adsorption on pH. Values of logK (Cd) (3.1), n(Cd) (1.8), and p (0.19) in the case of the NICCA isotherm or logK(Cd) (2.94-3.4) for Langmuir competitive models were obtained. Kinetic experiments were performed at two different pH values (3.0 and 4.5), establishing the time dependence that represents the sorption of cadmium with a pseudo-second-order kinetic model. It was observed that 4 h is enough to ensure that the equilibrium uptake was reached.

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“…Moreover, surface charge models reproduce experimental equilibrium data with similar accuracy. [31] Adsorption Isotherms…”

Section: Effect Of Ph On Metal Uptakementioning

confidence: 99%

Biosorption of Cadmium by Fucus spiralis

et al. 2004

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Environmental Context. Conventional processes for the removal of heavy metals from wastewaters generally involves chemical precipitation of metals (changing the pH) followed by a period to allow the metal precipitates to settle and be separated. These processes are inefficient when the metals are at a low concentration and still demand handling and disposal of toxic metal sludges. An alternative method for heavy metal removal is adsorption onto a biological material, biosorption. The biological materials, including agricultural byproducts, bacteria, fungi, yeast, and algae, all which take up heavy metals in substantial quantities, are relatively inexpensive, widely available, and from renewable sources. However, biological materials are complex and the active mechanisms often unclear.Abstract. Cadmium biosorption properties of nonliving, dried brown marine macroalga Fucus spiralis from Galician coast (northwest Spain) have been investigated. The biosorption capacity of the alga strongly depends on solution pH; the uptake is almost negligible at pH ≤ 2 and reaches a plateau at around pH 4.0. Cadmium biosorption kinetics by F. spiralis is relatively fast, with 90% of total adsorption taking place in less than one hour. A pseudo second order mechanism has been proved to be able to predict the kinetic behaviour of the biosorption process. The effect of initial cadmium ion concentration, alga dose, solution pH, and temperature on the biosorption kinetics has been studied. The Langmuir, Freundlich, Langmuir-Freundlich, and Tóth isotherms were used to fit the experimental data and to find out the adsorption parameters. Acid-base properties of the alga have been studied potentiometrically in order to calculate the number of acidic groups and the apparent pK value by using Katchalsky model. The pK obtained is comparable with typical values associated to the ionization of carboxyl groups of alginates, supporting the implication of these groups in the biosorption process.

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Surface charge and permeable gel descriptions of the ionic strength influence on proton binding to seaweed biomass

Cited by 19 publications

References 19 publications

Physicochemical studies of Cadmium(II) biosorption by the invasive alga in Europe, Sargassum muticum

Physicochemical studies of Cadmium(II) biosorption by the invasive alga in Europe, Sargassum muticum

Biosorption of cadmium by the protonated macroalga Sargassum muticum: Binding analysis with a nonideal, competitive, and thermodynamically consistent adsorption (NICCA) model

Biosorption of Cadmium by Fucus spiralis

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