Bioderived Pickering Emulsion Based on Chitosan/Trialkyl Phosphine Oxides Applied to Selective Recovery of Rare Earth Elements

A novel biobased pickering emulsion (PE) material was prepared by the encapsulation of Cyanex 923 (Cy923) into chitosan (CS) to selectively recover rare earth elements (REEs) from the aqueous phase. The preparation of PE was optimized through sequentially applying a 23 full factorial design, followed by a 33 Box-Behnken design varying the Cy923 content, CS concentration, and pH of CS. The material was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), optical microscopy, rheological, compositional, and stability measurements. The resultant material was evaluated in the removal of yttrium by pH influence, nitrate concentration, kinetics, equilibrium isotherms, reusability, and a comparison with liquid-liquid (L-L) extraction and tested in a real scenario to extract Y from a fluorescent lamp powder waste. In addition, the selectivity of PE for REE was investigated with Y/Ca, Gd/Ca, and La/Ni systems. PE extracts REE at 1 ≤ pH ≤ 5 at nitrate concentrations up to 2 mol/L. The kinetics and equilibrium studies showed reaction times <5 min and a maximum sorption capacity of 89.98 mg/g. Compared with L-L extraction, PE consumed 48% less Cy923 without using organic diluents. PE showed a remarkable selectivity for REE in the systems evaluated, showing separation factors of 22.62, 9.35, and 504.64 for the blends Y/Ca, Gd/Ca/Mg, and La/Ni, respectively. PE showed excellent selectivity extracting Y from a real aqueous liquor from the fluorescent lamp powder. PE demonstrates to be an effective and sustainable alternative for REE recovering due to its excellent efficiency in harsh conditions, favorable green chemistry metrics, and use of a biopolymer material in its composition avoiding the use of organic solvents used in L-L extraction.

Sustainability Assessment of Green Ammonia Production To Promote Industrial Decarbonization in Spain

This article investigates the economic and environmental implications of implementing green ammonia production plants in Spain. To this end, one business-as-usual scenario for gray ammonia production was compared with three green ammonia scenarios powered with different renewable energy sources (i.e., solar photovoltaic (PV), wind, and a combination of solar PV and wind). The results illustrated that green ammonia scenarios reduced the environmental impacts in global warming, stratospheric ozone depletion, and fossil resource scarcity when compared with conventional gray ammonia scenario. Conversely, green ammonia implementation increased the environmental impacts in the categories of land use, mineral resource scarcity, freshwater eutrophication, and terrestrial acidification. The techno-economic analysis revealed that the conventional gray ammonia scenario featured lower costs than green ammonia scenarios when considering a moderate natural gas cost. However, green ammonia implementation became the most economically favorable option when the natural gas cost and carbon prices increased. Finally, the results showed that developing efficient ammonia-fueled systems is important to make green ammonia a relevant energy vector when considering the entire supply chain (production/transportation). Overall, the results of this research demonstrate that green ammonia could play an important role in future decarbonization scenarios.

Neodymium Recovery from the Aqueous Phase Using a Residual Material from Saccharified Banana-Rachis/Polyethylene-Glycol

Neodymium (Nd) is a key rare earth element (REE) needed for the future of incoming technologies including road transport and power generation. Hereby, a sustainable adsorbent material for recovering Nd from the aqueous phase using a residue from the saccharification process is presented. Banana rachis (BR) was treated with cellulases and polyethylene glycol (PEG) to produce fermentable sugars prior to applying the final residue (BR–PEG) as an adsorbent material. BR–PEG was characterized by scanning electron microscopy (SEM), compositional analysis, pH of zero charge (pHpzc), Fourier transform infrared analysis (FTIR) and thermogravimetric analysis (TGA). A surface response experimental design was used for obtaining the optimized adsorption conditions in terms of the pH of the aqueous phase and the particle size. With the optimal conditions, equilibrium isotherms, kinetics and adsorption–desorption cycles were performed. The optimal pH and particle size were 4.5 and 209.19 μm, respectively. BR–PEG presented equilibrium kinetics after 20 min and maximum adsorption capacities of 44.11 mg/g. In terms of reusage, BR–PEG can be efficiently reused for five adsorption–desorption cycles. BR–PEG was demonstrated to be a low-cost bioresourced alternative for recovering Nd by adsorption.

Rare earth elements recovery from secondary wastes by solid-state chlorination and selective organic leaching

Processing of end-of-life products (EoL) containing rare earth elements (REE) has gained increasing importance in recent years with the aim of avoiding supply risks. In addition, circular economy renders complete recirculation of technology metals mandatory. Fluorescent lamp wastes are an important source for REE recovery since they contain significant amounts, up to 55 wt%, of Y and Eu in red phosphors. For these purposes, solid-state chlorination (SSC) is an economically attractive alternative to wet acid leaching treatment, which profits from a considerable reduction of chemicals consumption and process costs. Chlorination takes place with dry HCl_(g) produced from thermal decomposition of NH₄Cl_(s), not only converting the REE content of the Hg-free phosphor waste into water soluble REE metal chlorides, but also avoiding the implications of aqueous complex chemistry of REE. To establish an industrial process viable on a commercial scale, the SSC process has been optimized by (i) using a design of experiment (DOE) varying temperature, residence time, and g_NH4Cl/g_solid ratio and (ii) improved leaching of the chlorinated metals with an organic mixture selective for REE. As a result, 95.7% of the Y and 92.2% of the Eu were selectively recovered at 295.9 °C, 67 min and a ratio of 1.27 g_NH4Cl/g_solid, followed by quantitative selective leaching of the REE. Owed to its low chemicals consumption and operation costs, the current process allows for valorizing lamp waste even when raw material prices are low.

A potential lignocellulosic biomass based on banana waste for critical rare earths recovery from aqueous solutions

Rare earth elements (REE) present multiple applications in technological devices but also drawbacks (scarcity and water contaminant). The current study aims to valorise the banana wastes - banana rachis (BR), banana pseudo-stem (BPS) and banana peel (BP) as sustainable adsorbent materials for the recovery of REE (Nd³⁺, Eu³⁺, Y³⁺, Dy³⁺ and Tb³⁺). The adsorbent materials were characterized using analytical techniques such as: Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential and scanning electron microscopy with energy dispersive X-ray probe. The adsorption performance and mechanisms were studied by pH dependence, equilibrium isotherms, kinetics, thermodynamics, ion-exchange and desorption evaluation. The results show good adsorption capacities for the three materials, highlighting BR that presents ∼100 mg/g for most of the REE. The adsorption process (100 mg REE/L) reaches the 60% uptake in 8 min and the equilibrium within 50 min. On the other hand, the thermodynamic study indicates that the adsorption is spontaneous and exothermic (ΔH° < 40 kJ/mol). The adsorption mechanism is based on the presence of carboxylic groups that induce electrostatic interactions and facilitate the surface nucleation of REE microcrystals coupled to an ion exchange process as well as the presence of other oxygen containing groups that establish weak intermolecular forces. The recovery of REE from the adsorbent (∼97%) is achieved using EDTA as desorbing solution. This research indicates that banana waste and particularly BR is a new and promising renewable bioresource to recover REE with high adsorption capacity and moderated processing cost.

Recovery of Neodymium (III) from Aqueous Phase by Chitosan-Manganese-Ferrite Magnetic Beads

Neodymium is a key rare-earth element applied to modern devices. The purpose of this study is the development of a hybrid biomaterial based on chitosan (CS) and manganese ferrite (MF) for the recovery of Nd(III) ions from the aqueous phase. The preparation of the beads was performed in two stages; first, MF particles were obtained by the assessment of three temperatures during the co-precipitation synthesis, and the best nano-MF crystallites were incorporated into CS to obtain the hybrid composite material (CS-MF). The materials were characterized by FTIR, XRD, magnetization measurements, and SEM-EDX. The adsorption experiments included pH study, equilibrium study, kinetics study, and sorption–desorption reusability tests. The results showed that for MF synthesis, 60 °C is an appropriate temperature to obtain MF crystals of ~30 nm with suitable magnetic properties. The final magnetic CS-MF beads perform maximum adsorption at pH 4 with a maximum adsorption capacity of 44.29 mg/g. Moreover, the material can be used for up to four adsorption–desorption cycles. The incorporation of MF improves the sorption capacity of the neat chitosan. Additionally, the magnetic properties enable its easy separation from aqueous solutions for further use. The material obtained represents an enhanced magnetic hybrid adsorbent that can be applied to recover Nd(III) from aqueous solutions.

Extraction of AuCl4- from HCl solutions by the chloride salt of the secondary amine Amberlite LA2 and estimation of the interaction coefficient between AuCl4- and H+

The equilibrium distribution of AuCl4- between hydrochloric acid and the chloride salt of the secondary amine Amberlite LA2 in xylene was investigated. The extraction reaction is exothermic (ΔH° = −20.8 kJ/mol). The stoi-chiometry of the complex formed in the organic phase can be represented by R'R″NHH+AuCl4- and the extraction equilibrium constant depends on the ionic strength. From this dependency it was found that log K° = 3.9 and the interaction coefficient between AuCl4- and H+ is 0.24.

Antimony Removal from Water by a Chitosan-Iron(III)[ChiFer(III)] Biocomposite

The presence of antimony(III) in water represents a worldwide concern, mainly due to its high toxicity and carcinogenicity potential. It can be separated from water by the use of sustainable biopolymers such as chitosan or its derivatives. The present study applied chitosan modified with iron(III) beads to Sb(III) removal from aqueous solutions. The resulting material performed with a high adsorption capacity of 98.68 mg/g. Material characterization consisted of Raman spectroscopy (RS), X-ray diffraction (XRD), scanning electron microscope observations (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc). The adsorption study included pH study, effect of initial concentration, kinetics, ion effect, and reusability assessment. The RS, XRD, and FTIR results indicated that the main functional groups in the composite were related to hydroxyl and amino groups, and iron oxyhydroxide species of α-FeO(OH). The pHpzc was found to be 7.41. The best adsorption efficiency was set at pH 6. The equilibrium isotherms were better fitted with a non-linear Langmuir model, and the kinetics data were fitted with a pseudo-second order rate equation. The incorporation of iron into the chitosan matrix improved the Sb(III) uptake by 47.9%, compared with neat chitosan (CS). The material did not exhibit an impact in its performance in the presence of other ions, and it could be reused for up to three adsorption⁻desorption cycles.

Rare earths separation from fluorescent lamp wastes using ionic liquids as extractant agents

Processing of end-of-life products has become essential in the rare earth elements (REEs) recovery field because the demand for these metals has increased over the last years due to their intensive use in advanced technologies. Fluorescent lamp wastes are considered one of the most interesting end-of-life products for investigation due to their high REEs content, mainly yttrium and europium. As a result, red phosphors (Y₂O₃:Eu³⁺ - YOX) have been chosen for evaluating their REEs' recovery potential. The REEs from a YOX reach liquor, coming from a soft leaching process have been precipitated adding oxalic acid and calcined to get the REEs in oxide form. Cyanex 572, D2EHPA and the ionic liquids, Primene 81R·Cyanex 572 IL and Primene 81R·D2EHPA IL, have been chosen to investigate the efficiency of REEs separation in chloride media. Yttrium, europium and cerium have been individually recovered by a four stages cross-flow solvent extraction process using the Primene 81R·D2EHPA IL and the Primene 81R·Cyanex 572 IL as extractants. Ce(III), Eu(III) and Y(III) have been obtained at high purities ≥ 99.9%. 4 mol/L HCl has been used to recover the yttrium and the europium from the organic phases.

Neodymium recovery from NdFeB magnet wastes using Primene 81R·Cyanex 572 IL by solvent extraction

The necessity of Rare Earth Elements (REEs) recycling is crucial to minimizing their supply risk and provide an alternative to greener technologies. Hence, the REEs recovery from NdFeB magnet wastes using cationic extractants by solvent extraction technique has been investigated in this research. Due to the difficulty in maintaining the aqueous pH in the industrial counter-current devices when extractants like Cyanex 272 or Cyanex 572 are used, the Primene 81R·Cyanex 572 ionic liquid has been synthesised to overcome this. 99.99% Nd(III) recovery with a purity of 99.7% from an aqueous mixture of Nd/Tb/Dy in chloride medium, the three representative REEs present in the NdFeB magnets wastes, has been achieved after two stages counter-current extraction process using 0.30 M of Primene 81R·Cyanex 572 ionic liquid (1:4 A:O ratio) diluted in Solvesso 100, without any aqueous pH conditioning.

Sorption of Hg(II) and Pb(II) Ions on Chitosan-Iron(III) from Aqueous Solutions: Single and Binary Systems

The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point of zero charge (pHpzc) analysis were carried out. The experimental set covered pH study, single and competitive equilibrium, kinetics, chloride and sulfate effects as well as sorption⁻desorption cycles. In single systems, the Langmuir nonlinear model fitted the experimental data better than the Freundlich and Sips equations. The sorbent material has more affinity to Hg(II) rather than Pb(II) ions, the maximum sorption capacities were 1.8 mmol·g-1 and 0.56 mmol·g-1 for Hg(II) and Pb(II), respectively. The binary systems data were adjusted with competitive Langmuir isotherm model. The presence of sulfate ions in the multicomponent system [Hg(II)-Pb(II)] had a lesser impact on the sorption efficiency than did chloride ions, however, the presence of chloride ions improves the selectivity towards Hg(II) ions. The bio-based material showed good recovery performance of metal ions along three sorption⁻desorption cycles.

Mathematical modeling of cadmium(II) solvent extraction from neutral and acidic chloride media using Cyanex 923 extractant as a metal carrier

This paper describes experimental work and the mathematical modeling of solvent extraction of cadmium(II) from neutral and acidic aqueous chloride media with a Cyanex 923 extractant in Exxol D-100. Solvent extraction experiments were carried out to analyze the influence of variations in the composition of the aqueous and organic phases on the efficiency of cadmium(II) extraction. In neutral and acidic chloride conditions, the extraction of cadmium(II) by the organophosphorous extractant Cyanex 923 (L) is based on the solvation mechanism of neutral H(n)CdCl((2+n)) species and the formation of H(n)CdCl((2+n))L(q) complexes in the organic phase, where n=0, 1, 2 and q=1, 2. The mathematical model of cadmium(II) extraction was derived from the mass balances and chemical equilibria involved in the separation system. The model was computed with the Matlab software. The equilibrium parameters for metal extraction, i.e. the stability constants of the aqueous Cd-Cl complexes, the formation constants of the acidic Cd-Cl species and the metal equilibrium extraction constants, were proposed. The optimized constants were appropriate, as there was good agreement when the model was fitted to the experimental data for each of the experiments.

Bismuth recovery from acidic solutions using Cyphos IL-101 immobilized in a composite biopolymer matrix

Impregnated resins prepared by the immobilization of an ionic liquid (IL, Cyphos IL-101, tetradecyl(trihexyl)phosphonium chloride) into a composite biopolymer matrix (made of gelatin and alginate) have been tested for recovery of Bi(III) from acidic solutions. The concentration of HCl slightly influenced Bi(III) sorption capacity. Bismuth(III) sorption capacity increased with IL content in the resin but non-linearly. Maximum sorption capacity reached 110-130mgBig(-1) in 1M HCl solutions. The mechanism involved in Bi recovery was probably an ion exchange mechanism, though it was not possible to establish the stoichiometric exchange ratio between BiCl(4)(-) and IL. Sorption kinetics were investigated through the evaluation of a series of parameters: metal concentration, sorbent dosage, type and size of sorbent particles and agitation speed. In order to reinforce the stability of the resin particles, the IL-encapsulated gels were dried; this may cause a reduction in the porosity of the resin particle and then diffusion limitations. The intraparticle diffusion coefficients were evaluated using the Crank's equation. Additionally, the pseudo-first-order and pseudo-second-order equations were systematically tested on sorption kinetics. Metal can be desorbed from loaded resins using either citric acid or KI/HCl solutions. The sorbent could be recycled for at least three sorption/desorption cycles.

Use of Liquid–Liquid Extraction with Neutral Organophosphorous Derivatives in the Estimation of (AuCl4-,H+) Interaction Coefficients

The liquid–liquid extraction of Au(III) from HCl solutions by a series of solvation extractants had been studied. The reagents are neutral organophosphorous derivatives such as phosphine oxides (Cyanex 921 and Cyanex 923) and phospholene derivatives (DMPL, EHMPL and NMPL). The distribution of gold between the aqueous and organic phases has been investigated under different variables. Experimental data were treated numerically in order to define the corresponding extracted species. Both experimental and numerical data were used to estimate the interaction coefficient between AuCl4- and H+ by using the specific interaction theory (SIT). Moreover, experimental data on the liquid–liquid extraction of HCl by these phosphorous derivatives were given.

Recovery of zinc(II) from HCl spent pickling solutions by solvent extraction

Recovery of zinc(II) from HCl spent pickling solutions by solvent extraction using CYANEX921, CYANEX923, CYANEX302, tributyl phosphate, and ALAMINE336 extractants was studied. Tributyl phosphate was selected as suitable extractant. It permitted both effective zinc(II) extraction and the stripping from loaded organic phase with water. The presence of iron(II) did not affect zinc extraction, and only negligible oxidation of iron(II) was observed during extraction experiments. CYANEX reagents and ALAMINE336 extracted zinc(II) strongly, but the stripping with water was ineffective. Moreover, a significant oxidation of iron(II) to iron(III) occurred during extraction. Each of three reagents (CYANEX923, ALAMINE336 and TBP) extracted iron(III) very well. Thus, if iron(III) was present in the spent pickling solution, prior to the extraction it had to be reduced to iron(II). The oxidation was low for tributyl phosphate and high for CYANEX923 and ALAMINE336. CYANEX302 was inactive both for zinc(II) and iron(III) and could not be used for extraction of zinc(II) from spent pickling hydrochloric acid solutions.