Biosorption of Neodymium (Nd) from Aqueous Solutions Using Spirulina platensis sp. Strains

Evaluation of Holmium(III), Erbium(III), and Gadolinium(III) Accumulation by Cyanobacteria Arthrospira platensis Using Neutron Activation Analysis and Elements' Effects on Biomass Quantity and Biochemical Composition

Rare-earth elements are released into the aquatic environment as a result of their extensive use in industry and agriculture, and they can be harmful for living organisms. The effects of holmium(III), erbium(III), and gadolinium(III) when added to a growth medium in concentrations ranging from 10 to 30 mg/L on the accumulation ability and biochemical composition of Arthrospira platensis were studied. According to the results of a neutron activation analysis, the uptake of elements by cyanobacteria occurred in a dose-dependent manner. The addition of gadolinium(III) to the growth medium did not significantly affect the amount of biomass, whereas erbium(III) and holmium(III) reduced it up to 22% compared to the control. The effects of rare-earth elements on the content of proteins, carbohydrates, phycobiliproteins, lipids, β carotene, and chlorophyll a were evaluated. The studied elements had different effects on the primary biomolecule content, suggesting that holmium(III) and erbium(III) were more toxic than Gd(III) for Arthrospira platensis.

Fabrication of magnesium oxide-calcium alginate hydrogel for scaffolding yttrium and neodymium from aqueous solutions

In this research, the possibility of using sustainable nano-MgO/Ca-alginate beads for efficient sorption of some rare earth metal ions such as neodymium(III) and yttrium(III) from an aqueous acidic solution was explored. The nano-MgO/Ca-alginate beads adsorbent was characterized before and after sorption of Nd(III) and Y(III) using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) techniques. Batch sorption parameters were investigated, such as contact time, initial metal ion concentration, and adsorbent dose (V/m). The calculated experimental results showed that the suitable selected sorption conditions were carried out using 100 mg/L of Nd(III) and Y(III) with nano MgO/Ca-alginate beads (contact time = 90 min, pH = 2, V/m = 0.05 L/g). The maximum sorption capacity of 0.1 g of nano MgO/Ca-alginate was found to be 7.85 mg/g and 5.60 mg/g for Nd(III) and Y(III), respectively. The desorption of Nd(III) and Y(III) from the loaded nano MgO/Ca-alginate was achieved with 1.0 M sulfamic acid and found to be 51.0% and 44.2%, respectively. The calculated thermodynamic parameters for the nano MgO/Ca-alginate/Nd/Y system show that the positive charge of ΔHo confirmed the endothermic nature of the sorption process, ΔSo (positive) indicates an increase in reaction system disordering, and ΔGo (negative) indicates a spontaneous process. These kinetic results indicate that the sorption process of Nd(III) and Y(III) on nano MgO/Ca-alginate beads is performed by the chemisorption process.

The Remediation of Dysprosium-Containing Effluents Using Cyanobacteria Spirulina platensis and Yeast Saccharomyces cerevisiae

Dysprosium is one of the most critical rare earth elements for industry and technology. A comparative study was carried out to assess the biosorption capacity of cyanobacteria Spirulina platensis and yeast Saccharomyces cerevisiae toward dysprosium ions. The effect of experimental parameters such as pH, dysprosium concentration, time of contact, and temperature on the biosorption capacity was evaluated. Biomass before and after dysprosium biosorption was analyzed using neutron activation analysis and Fourier-transform infrared spectroscopy. For both biosorbents, the process was quick and pH-dependent. The maximum removal of dysprosium using Spirulina platensis (50%) and Saccharomyces cerevisiae (68%) was attained at pH 3.0 during a one-hour experiment. The adsorption data for both biosorbents fitted well with the Langmuir isotherm model, whereas the kinetics of the process followed the pseudo-second-order and Elovich models. The maximum biosorption capacity of Spirulina platensis was 3.24 mg/g, and that of Saccharomyces cerevisiae was 5.84 mg/g. The thermodynamic parameters showed that dysprosium biosorption was a spontaneous process, exothermic for Saccharomyces cerevisiae and endothermic for Spirulina platensis. Biological sorbents can be considered an eco-friendly alternative to traditional technologies applied for dysprosium ion recovery from wastewater.

Wood waste-based functionalized natural hydrochar for the effective removal of Ce(III) ions from aqueous solution

In this study, a sustainable and easily prepared hydrochar from wood waste was studied to adsorb and recover the rare earth element cerium (Ce(III)) from an aqueous solution. The results revealed that the hydrochar contains several surface functional groups (e.g., C-O, C = O, OH, COOH), which largely influenced its adsorption capacity. The effect of pH strongly influenced the Ce(III) removal, achieving its maximum removal efficiency at pH 6.0 and very low adsorption capacity under an acidic solution. The hydrochar proved to be highly efficient in Ce(III) adsorption reaching a maximum adsorption capacity of 327.9 mg g^-1 at 298 K. The kinetic and equilibrium process were better fitted by the general order and Liu isotherm model, respectively. Possible mechanisms of Ce(III) adsorption on the hydrochar structure could be explained by electrostatic interactions and chelation between surface functional groups and the Ce(III). Furthermore, the hydrochar exhibited an excellent regeneration capacity upon using 1 mol L^-1 of sulfuric acid (H₂SO₄) as eluent, and it was reused for three cycles without losing its adsorption performance. This research proposes a sustainable approach for developing an efficient adsorbent with excellent physicochemical and adsorption properties for Ce(III) removal.