Cd(II) biosorption using Lessonia kelps
Graphical abstract
Modeling of uptake kinetics using the model of resistance to intraparticle diffusion (Crank’s equation).
Research highlights
► Lessonia kelps are efficient sorbents for copper and nickel. ► Characterization of biosorbent by FT-IR spectroscopy and SEM–EDAX. ► Langmuir equation for modeling sorption isotherm. ► Crank equation for fitting uptake kinetics. ► Greater impact of sorbent dosage and metal concentration against particle size and temperature.
Introduction
In several countries a waste material can only be discharged to landfill when the user has demonstrated that the material cannot be recycled under acceptable economic and technical constraints. This politics impulses the development of alternative hydrometallurgical processes for recycling metals from spent materials (batteries, spent catalysts, etc.). The regulations for the discharge of metal ions from industrial wastewaters are also progressively becoming more stringent. Conventional processes such as precipitation [1], [2], solvent extraction [3], ion exchange, chelating or impregnated resins [4], [5], membranes processes [6] are facing technical and/or economical limitations, especially for dilute effluents: (a) difficulty to reach required concentration levels, (b) production of huge amounts of contaminated sludge, (c) loss of hazardous substances (liquid/liquid extraction), (d) analysis of life cycle (the thermal degradation of synthetic resin may produce hazardous derivatives) or (e) cost. There is a need for developing/using alternative materials for the treatment of low-concentration effluents. Biosorption is considered a potential alternative based on the use of cheap and renewable resources. It consists in using materials of biological origin for the binding of contaminants (metal ions, organic compounds) through mechanisms similar to those involved in the sorption of solutes on ion exchange/chelating resins.
A number of biosorbents have been tested for the last decades. These materials are issued from biomass [7], [8], [9], agriculture wastes [10], [11], [12], [13], industrial sub-products [14], or from marine resources [15], [16], [17], [18], [19], [20]. Bacteria, fungi and algae are among the most common biosorbents carried out for the recovery of metal ions from dilute effluents [21], [22], [23]. While fungal biomass is binding metal cations through accumulation on the aminopolysaccharides that constitute the cell wall of these microorganisms (i.e.; chitin/chitosan biopolymers), algae are accumulating metal ions through interactions with carboxylic groups (i.e.; alginate/alginic acid) or sulfated polysaccharides (i.e.; fucoidan, carrageenan) depending on the type of seaweed.
Lessonia is classified as a brown alga constitutive of the kelp. It can be used as an industrial source for the production of alginate. Lessonia nigrescens and Lessonia trabeculata have similar structure and they can be both used for biopolymer extraction, although L. nigrescens is more frequently cited [24], [25], [26]. This biomass also contains fucoidan (a biopolymer that bears sulfonic groups) [27]. Alginate is a linear unbranched heteropolymer constituted of β-(1 → 4)-linked d-mannuronic acid (M) and α-(1 → 4)-linked l-guluronic acid (G) residues (Scheme 1). Lessonia biomass has a strong affinity for metal binding through interactions of carboxylic groups with metal ions [28], [29], [30].
The affinity of Lessonia biomass for metal ions is important not only for the purpose of metal recovery but also for the evaluation of the biomass for the extraction/production of alginate/alginic acid. The recovery of kelp material from areas subjected to possible mining or metallurgical contamination may be hazardous and requires pre-treatment of the biomass (metal desorption) prior to biopolymer extraction [31]. So, the information accumulated on the biosorption of metal ions on this type of biomass will be useful for securing the alginate resource and its extraction process.
This study focuses on the sorption of Cd(II) on L. trabeculata (L.t.) and L. nigrescens (L.n.). The biomass was first characterized using FT-IR spectrometry analysis and SEM–EDAX (scanning electron microscopy coupled with energy disperse analysis of X-ray). The influence of pH was investigated to select optimum pH for sorption studies. The sorption isotherms were compared at different temperatures for both L.n. and L.t. before investigating the uptake kinetics. The impacts of particle size, sorbent dosage, metal concentration and temperature on kinetic profiles were determined with the objective of discussing controlling mechanisms (reaction rate, resistance to film diffusion and resistance to intraparticle diffusion).
Section snippets
Materials
The biomass was collected on the Peruvian coast (in the Tacna area for L. trabeculata, and in the Bahia de Paracas, Pisco, for L. nigrescens Bory). Samples were collected in the stipe fraction of kelp biomass. They have been identified by the Phytology Section of the Botanical Department at the Biological Sciences Faculty of the Universidad Nacional Mayor de San Marcos (Peru). After being washed with demineralized water, the biomass was cut and dried (in an oven at 50 °C for 24 h). Dried biomass
Characterization of biomass and metal-biomass interactions
The biosorbents were characterized by SEM–EDAX analysis. Figure AM1 (SEM photograph, Additional Material Section) shows that the particles of raw L. nigrescens are not perfectly homogeneous. The analysis of X-ray pattern on the two types of areas (gray and white areas) shows significant differences in the composition of the material. The intensity of the signals for alkaline (Na) and alkaline-earth (Ca, Mg) metals is significantly greater on dark areas than those observed on clear areas. This
Conclusion
Lessonia biomass is an efficient biosorbent for Cd(II). At pH close to 6 the maximum sorption capacity reaches up to 110 mg Cd g−1 for L. nigrescens and up to 160 mg Cd g−1 for L. trabeculata. These values are among the highest values obtained with algal biosorbents. A pre-treatment (using calcium chloride) is required for stabilizing the biomass (preventing the leaching of alginate-based materials). Sorption capacity increases with pH and stabilizes at pH close to 5–6. The pre-treatment also
Acknowledgments
Authors thanks European Union for financial support under the ALFA program (Contract AML/190901/06/18414/II-0548-FC-FA), and the Program PREPA-PREFALC (for supporting the collaboration between Ecole des Mines d’Alès and the Universidad Peruana Cayetano Heredia). Authors also thank Jean-Marie Taulemesse for SEM–EDAX analyses.
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