Universidade da Coruña. UDCDspace
(405 recursos)
UDCDspace é o repositorio dixital da Universidade da Coruña, un sistema que proporciona de xeito estable e seguro a preservación de documentos dixitais produto da actividade científica e institucional da UDC, e facilita a súa accesibilidade en Internet.
Mostrando recursos 1 - 10 de 10
1.
Kinetic and equilibrium study of the reaction of nitroprusside and hydroxide ions: influence of ionic strength using Pitzer Model - Rubín Carrero, Eugenia; Rodríguez Barro, Pilar; Brandariz Lendoiro, Isabel; Sastre de Vicente, Manuel Esteban
A kinetic and equilibrium study of the addition reaction of hydroxide ions to nitroprusside has
been carried out in this paper. Rate and equilibrium constants at different salt concentrations
(up to 4 mol/kg) were obtained and the influence of ionic strength was studied by means of
Pitzer equations. This model is of special interest because it is able to explain the
experimental behaviour at high ionic strength, when Debye-Huckel limiting law is no longer
valid.
2.
Physicochemical studies of cadmium (II) biosorption by the invasive alga in Europe Sargassum muticum - Lodeiro Fernández, Pablo; Cordero Pérez, Bruno; Grille Cancela, Zulaika; Herrero Rodríguez, Roberto; Sastre de Vicente, Manuel Esteban
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...
3.
Gibbs-Donnan and specific ion interaction theory descriptions of the effect of ionic strength on proton dissociation of alginic acid - Rey Castro, Carlos; Herrero Rodríguez, Roberto; Sastre de Vicente, Manuel Esteban
The apparent proton dissociation constants of a commercial alginic acid have been obtained in KNO3 and NaCl at concentrations ranging between 0.01 and 2 mol·L-1. An analysis of the dependence on the ionic strength at a constant value of the dissociation degree was done by means of empirical functions derived from the Gibbs-Donnan formalism for polyelectrolytes and a specific ion interaction theory (SIT). Both functions were able to fit the experimental data, although SIT yielded rather high errors in the fitted parameters due to a problem of multicollinearity, in contrast to the function derived from the Gibbs-Donnan approach.
4.
Biosorption of cadmium by the protonated Macroalga Sargasssum muticum: binding analysis with a non-ideal, competitive and thermodynamically consistent adsorption (NICCA) model. - Lodeiro Fernández, Pablo; Rey Castro, Carlos; Barriada Pereira, José Luis; Sastre de Vicente, Manuel Esteban; Herrero Rodríguez, Roberto
Protonated biomass of the seaweed Sargassum muticum was investigated for its ability to remove cadmium(II) from aqueous solutions. In this work, a non-ideal, semi-empirical, thermodynamically consistent (NICCA) isotherm was proposed to fit the experimental ion binding data obtained in NaNO3 0.05 mol·L-1. This model describes satisfactorily the competition between protons and metal ions. 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 NICCA isotherm constitutes a great improvement with respect to a simpler Langmuir competitive equation, which was not able to describe...
5.
Biosorption of cadmium by biomass of brown marine macroalgae - Lodeiro Fernández, Pablo; Cordero Pérez, Bruno; Barriada Pereira, José Luis; Herrero Rodríguez, Roberto; Sastre de Vicente, Manuel Esteban
Five different brown seaweeds, Bifurcaria bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria ochroleuca and Pelvetia caniculata were studied for their ability to remove cadmium from aqueous solution. Kinetic of cadmium adsorption by all the algae was relatively fast, 90% of total adsorption occurring in less than one hour. These experiments could be accuracy described by a pseudo-second order rate equation, obtaining for the rate constant sorption, k, values between 1.66·10-3 and 9.92·10-3 g/mg·min. The equilibrium adsorption isotherms of Langmuir, Langmuir-Freundlich, Tóth and Freundlich were obtained for the quantitative description of the cadmium uptake. The maximum metal biosorption capacity (qmax) and the...
6.
Removal of inorganic mercury from aqueous solutions by biomass of the marine macroalga Cystoseira Baccata - Herrero Rodríguez, Roberto; Lodeiro Fernández, Pablo; Rey Castro, Carlos; Vilariño Barreiro, María Teresa; Sastre de Vicente, Manuel Esteban
The ability of Cystoseira baccata algal biomass to remove Hg(II) from aqueous solutions is investigated. The mercury biosorption process is studied through batch experiments at 25ºC with regard to the influence of contact time, initial mercury concentration, solution pH, salinity and presence of several divalent cations. The acid-base properties of the alga are also studied, since they are related to the affinity for heavy metals. The studies of the pH effect on the metal uptake evidence a sharp increasing sorption up to a pH value around 7.0, which can be ascribed to changes both in the inorganic Hg(II) speciation and...
9.
Biosorption of phenolic compounds by the brown alga Sargassum muticum - Rubín Carrero, Eugenia; Rodríguez Barro, Pilar; Herrero Rodríguez, Roberto; Sastre de Vicente, Manuel Esteban
Phenol, 2-chlorophenol (2-CP), and 4-chlorophenol (4-CP) biosorption on Sargassum muticum, an invasive macroalga in Europe, has been investigated. The efficiency of this biosorbent was studied measuring the equilibrium uptake using the batch technique. A chemical pre-treatment with CaCl2 has been employed in this study in order to improve the stability as well as the sorption capacity of the algal biomass. The influence of pH on the equilibrium binding and the effect of the algal dose were evaluated. The experimental data at pH=1 have been analysed using Langmuir and Freundlich isotherms. It was found that the maximum sorption capacity of chlorophenols,...
10.
Removal of methylene blue from aqueous solutions using as biosorbent sargassum muticum: an invasive macroalga in Europe - Rubín Carrero, Eugenia; Rodríguez Barro, Pilar; Herrero Rodríguez, Roberto; Cremades Ugarte, Javier; Bárbara Criado, Ignacio; Sastre de Vicente, Manuel Esteban
Methylene blue adsorption on Sargassum muticum, an invasive macroalga in Europe, has been
investigated using visible absorption spectroscopy. Different pre-treatments, protonation and chemical
cross-linking with CaCl2 or H2CO, have been tested in order to improve the stability as well as the
adsorption capacity of the algal biomass. The equilibrium binding has been described in terms of
Langmuir or Freundlich isotherms depending on the algal pre-treatment; from the maximum
adsorption capacity values, an estimation of the algal specific surface area was made. Moreover, it
has been found that adsorption kinetics can be described according to the first order Lagergren model,
from which the rate constant and the adsorption...
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