Biomass in Batch Systems: Physicochemical Evaluation of Kinetics and Adsorption Models

Galdieria sulphuraria ACUF427 Freeze-Dried Biomass as Novel Biosorbent for Rare Earth Elements

Rare earth elements (REEs) are essential components of modern technologies and are often challenging to acquire from natural resources. The demand for REEs is so high that there is a clear need to develop efficient and environmentally-friendly recycling methods. In the present study, freeze-dried cells of the extremophile Galdieria sulphuraria were employed to recover yttrium, cerium, europium, and terbium from quaternary-metal aqueous solutions. The biosorption capacity of G. sulphuraria freeze-dried algal biomass was tested at different pHs, contact times, and biosorbent dosages. All rare earths were biosorbed in a more efficient way by the lowest dose of biosorbent, at pH 4.5, within 30 min; the highest removal rate of cerium was recorded at acidic pH (2.5) and after a longer contact time, i.e., 360 min. This study confirms the potential of freeze-dried cells of G. sulphuraria as innovative ecological biosorbents in technological applications for sustainable recycling of metals from e-waste and wastewater.

Dysprosium Absorption of Aluminum Tolerant- and Absorbing-Yeast

Background: Biosorption plays important roles in the recovery of rare earth metals. The absorption of dysprosium (Dy) was tested in yeast. Interestingly, brewing yeast, Saccharomyces cerevisiae, showed Dy absorption, and two strains, Alt-OF2 and Alt-OF5—previously isolated as highly aluminum-tolerant and -absorbing yeast strains—were screened and shown to be superior in terms of their Dy absorption when compared to S. cerevisiae. Here, we analyzed the Dy absorption in these yeast strains. Methods: Dy absorption in yeast strains was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES). Dy concentration and localization in yeast cells and the effect of treated pH on the Dy absorption were assayed. Results: The Dy absorption of Alt-OF2 and Alt-OF5 was more than two times that of S. cerevisiae. The absorption of Dy took place inside of the cells, and a small amount was found in the cell wall fraction. Conclusion: These results suggest that yeast offers a promising solution to the biosorption of rare earth metals and that it is possible to use the highly absorbent strains to breed a yeast strain that can recover even higher concentrations of Dy.

Towards rare earth element recovery from wastewaters: biosorption using phototrophic organisms

Abstract

Whilst the biosorption of metal ions by phototrophic (micro)organisms has been demonstrated in earlier and more recent research, the isolation of rare earth elements (REEs) from highly dilute aqueous solutions with this type of biomass remains largely unexplored. Therefore, the selective binding abilities of two microalgae (Calothrix brevissima, Chlorella kessleri) and one moss (Physcomitrella patens) were examined using Neodym and Europium as examples. The biomass of P. patens showed the highest sorption capacities for both REEs (Nd³⁺: 0.74 ± 0.05 mmol*g⁻¹; Eu³⁺: 0.48 ± 0.05 mmol*g⁻¹). A comparison with the sorption of precious metals (Au³⁺, Pt⁴⁺) and typical metal ions contained in wastewaters (Pb²⁺, Fe²⁺, Cu²⁺, Ni²⁺), which might compete for binding sites, revealed that the sorption capacities for Au³⁺ (1.59 ± 0.07 mmol*g⁻¹) and Pb²⁺ (0.83 ± 0.02 mmol*g⁻¹) are even higher. Although different patterns of maximum sorption capacities for the tested metal ions were observed for the microalgae, they too showed the highest affinities for Au³⁺, Pb²⁺, and Nd³⁺. Nd-sorption experiments in the pH range from 1 to 6 and the recorded adsorption isotherms for this element showed that the biomass of P. patens has favourable properties as biosorbent compared to the microalgae investigated here. Whilst the cultivation mode did not influence the sorption capacities for the target elements of the two algal species, it had a great impact on the properties of the moss. Thus, further studies are necessary to develop effective biosorption processes for the recovery of REEs from alternative and so far unexploited sources.

Key points

• The highest binding capacity for selected REEs was registered for P. patens.

• The highest biosorption was found for Au and the biomass of the examined moss.

• Biosorption capacities of P. patens seem to depend on the cultivation mode.

Biosorption as green technology for the recovery and separation of rare earth elements

Rare earth elements (REE) have great demand for sustainable energy and the high-end technology sector. The high similarity of REE owing to the nature of their electronic configurations increases the difficulty and costs of the development of chemical processes for their separation and recovery. In this way, the development of green technologies is highly relevant for replacing conventional unit operations of extractive metallurgy, viz. precipitation, liquid-liquid and solid-liquid extraction, and ion-exchange. Biosorption is a physicochemical and metabolically-independent biological process based on a variety of mechanisms including absorption, adsorption, ion-exchange, surface complexation and precipitation that represents a biotechnological cost-effective innovative way for the recovery of REE from aqueous solutions. This mini-review provides an overview and current scenario of biosorption technologies existing to recover REE, seeking to address the possibilities of using a green technology approach for wastewater treatment, as well as for the recovery of these high valued elements in the REE production chain.

Biosorption of dysprosium (III) using raw and surface-modified bark powder of Mangifera indica: isotherm, kinetic and thermodynamic studies

In this paper, we have used HDTMA-Br- and NaOH-treated bark powder of Mangifera indica as bio-sorbents for the removal of dysprosium (III) from its aqueous solution. The adsorption process was investigated at different experimental parameters such as contact time, temperature, pH, adsorbent dose, and initial metal concentration. The amount of chemically modified bark powder required was almost two times lesser than raw bark to get a higher percentage removal of the metal ion. The kinetics results revealed the adsorption process follows the nonlinear form a pseudo-second-order model. The negative values of Gibbs free energy change (∆G°) indicated the spontaneity of the adsorption process. The enthalpy change (∆H°) and entropy change (∆S°) of adsorption were 60.97 kJ/mol and 0.48 J/mol K, respectively signified it as an endothermic process. The maximum adsorption capacity was found to be 55.04 mg/g for sorption of Dy (III) on NaOH-treated bark powder and was better fitted to Langmuier model. It was confirmed to follow physisorption process and the activation energy of the system was found to be 41.07 kJ/mol. The possibility of adsorbent and adsorbate interactions were indicated by the FTIR and SEM/EDX analysis.

The kinetics of uptake and recovery of lanthanum using freshwater algae as biosorbents: comparative analysis

In this study, the adsorption and desorption kinetics of lanthanum (La) on micro algal cells was investigated. The internal transcribed spacer (ITS) and 18S ribosomal RNA gene (rRNA) were used for molecular identification of the species. The algal species were found to have 95-98% identities to Desmodesmus multivariabilis, Scenedesmus acuminutus, Chloroidium saccharophilum and Stichococcus bacillaris. The species were cultured and tested independently. D. multivariabilis was found to be the most efficient at adsorbing lanthanum with a maximum sorption capacity (qmax) of 100 mg/g and a high affinity (b) of 4.55 L/g. Desorption of La was also highest in D. multivariabilis with recovery up to 99.63% at initial concentration as high as 100 mg/L. Desorption data fitted best to the modified pseudo second-order with a better correlation coefficient (R(2)) of ⩽0.98 than first order model. The results showed feasibility of lanthanum recovery using algal sorbents, a cost effective method.