Dysprosium adsorption on expanded vermiculite: Kinetics, selectivity and desorption

Ligand-selective turn-off sensing, harvesting and post-adsorptive use of Dy(III) and Yb(III) by intrinsically fluorescent flower-shaped Gum Acacia-grafted hydrogels

Rare earth metals (REMs), such as Dysprosium (Dy) and Ytterbium (Yb), have experienced unprecedented demand in recent times due to their applications in high-end technologies. REMs are found only in select geographic locations placing tremendous economic constraints on their use. In this work, we have developed Gum Acacia-grafted hydrogels (GmAc-FluoroTerPs) that are capable of selective detection and capture of Dy and Yb. The intrinsically blue fluorescent polymer hydrogel GmAc-FluoroTerP has been optimized for Dy(III) and Yb(III) specific quenching, enabling limit of detection of the REMs at 0.13 nM and 60.8 pM, respectively. A comprehensive structural characterization of the fluorescent hydrogel has been performed via NMR, FTIR, XPS, EPR, TGA, XRD, TEM, SEM, EDX, TCSPC, and DLS. In addition to an in situ generated fluorophore, GmAc-FluoroTerP displays a distinctive aggregation induced emission enhancement in mixed solvents. The complexation of Dy(III)/Yb(III) with GmAc-FluoroTerP hydrogel has been characterized by XPS, TCSPC, and logic gate analyses, and the adsorptive capacity for Dy(III) and Yb(III) are found to be best reported till date as 125.57 mg g-1 and 102.27 mg g-1, respectively. Desorption at acidic pH allows recovery of the REMs. We also report semiconducting behaviour of the native fluorescent hydrogel, that is enhanced upon adsorptive capture of Dy(III) and Yb(III), with calculated band gaps at 1.37, 0.77, and 0.49 eV, respectively. The convergent sensing, capture, and reuse of Dy(III) and Yb(III) presented in this work promises a hitherto unreported template for application on other REMs.

Opportunity for a greener recovery of dysprosium(III) from secondary sources by a novel Mannich reaction-modified phosphorylated chitosan hydrogel

The depleting supply of natural sources of rare earth elements (REE) is a concern to many nations as demand for advanced technology is becoming vital for national security. In this communication, the recovery of dysprosium(III) from aqueous systems was exemplified by a modified phosphorylated chitosan (PCs/MB) prepared by the C-Mannich reaction of phosphorylated chitosan, glutaraldehyde, and 4-hydroxycoumarin in ethanolic solution. Batch adsorption studies achieved a maximum adsorption capacity (qmax) of 34 mg/g at 25 °C and pH = 5.4 for 2 h. Fourier Transform-Infrared Spectroscopy, elemental mapping, and quantitative analyses revealed ion-exchange mechanism with C6-phosphate and a synergistic complexation with the amino group between two hexose units of the chitosan chain confirming the correlation provided by the pseudo-second order kinetics (R2 = 0.9996), extrapolated mean free energy of adsorption (Eads) of 12.9 kJ/mol from the corrected Dubinin-Radushkevich isotherm, and the extrapolated enthalpy of adsorption (ΔH0ads) of -42.4 kJ/mol from the linearized Van't Hoff plot. Competitive adsorption with iron(II), cerium(III), and neodymium(III) demonstrated preferential removal of dysprosium(III) and complete exclusion of iron(II), which illustrates potential application in the separation of REE from electronic wastes.

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.

Cerium biosorption onto alginate/vermiculite-based particles functionalized with ionic imprinting: Kinetics, equilibrium, thermodynamic, and reuse studies

Cerium is an essential element for several applications in industry, therefore, recovering it from secondary sources is a promising strategy from an economic and environmental perspective. For this purpose, biosorption is a low-cost and effective alternative. The present work evaluated the recovery of Ce³⁺ from aqueous solutions using alginate/vermiculite-based particles (ALEV) functionalized by ionic imprinting. From the kinetic assays, it was verified that the uptake of Ce³⁺ followed the pseudo-second-order model and was mainly controlled by external diffusion. The Langmuir model better described the equilibrium data, and a maximum biosorption capacity of 0.671 mmol/g at 45 °C was attained. The evaluation of the thermodynamic quantities revealed that the process occurs spontaneously and endothermically. The particles reuse and Ce³⁺ recovery were achieved using 0.1 mol/L HCl or 1.0 mol/L CaCl₂ solutions for up to four cycles of biosorption/desorption. The biosorbent was characterized before and posted Ce³⁺ biosorption to investigate the morphology, textural properties, crystallinity, thermal resistance, composition, and functional groups of the biosorbent.

The Expanded Vermiculite Was Quickly Prepared by the Catalytic Action of Manganese Dioxide on Hydrogen Peroxide and Its Adsorption Properties to Cd

The structure and activity of vermiculite can be maintained by expanding vermiculite (Vrm) with hydrogen peroxide. However, it is time-consuming. In past studies, little attention has been paid to the catalytic properties of manganese dioxide on hydrogen peroxide to improve the swelling efficiency of vermiculite. In this experiment, this catalytic effect was utilized to swell Vrm in a short time. The samples were then used to adsorb Cd from the solution. Through a series of characterization tests. The results showed that the exothermic rate was 1960.42-2089.164 J/min and the total exothermic heat was 39,208.4-41,783.28 J when expanding 10 gVrm, which could have a good expansion effect. The expansion was completed in about 40 min. Compared with Vrm, the adsorption of Cd is enhanced by about 30%. It is consistent with the proposed secondary kinetic adsorption model. This study provides a new perspective and theoretical guidance for improving the efficiency of Vrm stripping by hydrogen peroxide. A kind of expanded Vrm with better Cd adsorption efficiency was also prepared.

Aeration Biofilter Filler Screening and Experimental Research on Nitrogen and Phosphorus Purification in Rural Black Water

In rural toilets, black water still remains polluted by nitrogen and phosphorus after being pre-treated by septic tanks. This study uses aerated biofilters to purify black water, screen the biofilter filler, and determine its effect on nitrogen and phosphorus purification in rural black water. This study introduced the concept of the “shape factor” into the Langmuir and Freundlich equations and optimized the isotherm adsorption model to better fit the actual dynamics of nitrogen and purification in black water. Combined with the first-order kinetic equation, the double constant equation, and the Elovich equation, the adsorption performance of seven kinds of biofilter fillers (i.e., zeolite, volcanic rock, sepiolite, ceramsite, anthracite, vermiculite, and peat) was studied. Then, the biofilter was constructed using a combination of fillers with better adsorption properties, and its ability to purify rural black water was studied. Results showed that vermiculite and zeolite had little effect on nitrogen and a high saturated adsorption of 654.50 and 300.89 mg·kg−1, respectively; peat and ceramsite had little effect on phosphorus and a high saturated adsorption of 282.41 mg·kg−1 and 233.89 mg·kg−1, respectively. The adsorption rate of nitrogen from fast to slow was vermiculite > peat > zeolite > volcanic rock > sepiolite > ceramsite > anthracite. The adsorption rate of phosphorus from fast to slow was peat > ceramsite > zeolite > sepiolite > vermiculite > volcanic rock > anthracite. Four combined biological filter fillers aided the removal of nitrogen and phosphorus from rural high-concentration black water. The combination of zeolite and ceramsite filler had a good nitrogen and phosphorus removal effect in high-concentration black water. After the system was stable, the nitrogen removal rate attained 71–73%, and the phosphorus removal rate attained 73–76% under the influent condition of total nitrogen and phosphorus concentrations of 150–162 and 10–14 mg·L−1, respectively. This study provides technical support and reference for the purification and treatment of rural black water.