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 solutionsPeer ReviewedPostprint (published version

Evaluación de la obtención de carbón activado a partir lodos de depuradoras de aguas residuales de la comunidad de Valencia: revisión bibliográfica

As the population grows, sewage sludge production will continue to increase due to necessary increase in the number of wastewater treatment plants. This work analyzes studies from recent years on the use of sewage sludge to obtain activated carbon (AC). The results indicate that in 2013 there was a greater scientific production (13,86 %) compared to other years and the country that stands out in the research is China (52,48 %). They also show that 77,23 % of the studies used sewage sludge as the only raw material, and 22,77 % used sewage sludge plus another precursor to improve the adsorption performance of the activated carbons. Removal efficiencies ≥ 50 % were indicated in dyes, organic compounds, chemical compounds and heavy metals (63,6 %, 68,2 %, 71,4 %, 60,6 % respectively), in turn, drugs had a higher percentage (66,7 %) in removal efficiencies < 50 %. In conclusion, there is much interest in recovering sewage sludge, which allows for obtaining a value-added product. The results show high contaminant removal performance, which makes this alternative economically viable.El crecimiento poblacional es un indicador de que la producción de lodos de depuradoras va a seguir incrementándose en los próximos años como consecuencia del incremento del número de plantas de tratamiento de aguas residuales. Este trabajo analiza los estudios que se han realizado en los últimos años sobre la utilización de lodos de depuradora para la obtención de carbón activado (CA). Los resultados indicaron que en el 2013 hubo una mayor producción científica (13,86 %) con respecto a los otros años y el país que destaca en investigaciones es China (52,48 %). Se encontró que el 77,23 % de estudios usó como única materia prima lodo de depuradora y el 22,77 % empleó lodos de depuradora más otro precursor para mejorar el rendimiento de adsorción de los carbones activados obtenidos. Se indicaron eficiencias de remoción ≥ 50 % en colorantes, compuestos orgánicos, compuestos químicos y metales pesados (63,6 %, 68,2 %, 71,4 % y 60,6 % respectivamente); a su vez, los fármacos tuvieron un mayor porcentaje (66,7 %) en eficiencia de remoción < 50 %. En conclusión, hay mucho interés en la valorización de los lodos de depuradora, de los que se puede obtener un producto de valor agregado. Los resultados demuestran altos rendimientos de remoción de contaminantes, lo que hace que esta alternativa sea económicamente viable

Valorization of cocoa's mucilage waste to ethanol and subsequent direct catalytic conversion into ethylene

BACKGROUND: The identification of new resources for producing biofuels and chemical-based products is crucial for processes sustainability. This study presents a valorization route to produce ethanol and ethylene using cocoa’s mucilage juice (MJ) residue from cocoa’s farms of variety “Arriba” (AC). The processing parameters to maximize the ethanol production and subsequent selectively conversion into ethylene were determined. The ethanol production has been carried out by investigating the effect of three parameters such as the temperature of fermentation, the initial fermentation pH, and the addition of (NH4)2SO4 as an N source in presence of free Saccharomyces cerevisiae NCYC 366. Consecutively, the selectivity of ethanol-ethylene conversion using a zeolite-based ZSM-5 catalyst was evaluated at different temperatures and ethanol concentrations. RESULTS: During the ethanol production, the best sugar conversion was reached at 30 ºC, adjusting the initial pH to 5 and without nitrogen source, resulting in 86.83% of sugars conversion, the maximum ethanol concentration of 68.65 g·L-1, and maximum ethanol production rate of 2.03 g·L-1 ·h-1 after 168 hours of fermentation. On the other hand, ethylene was produced using ZSM-5 based zeolite catalyst with > 99.9 % of efficiency in the temperature range between 240 ºC to 300 ºC. In addition, selectively ethylene formation was found at 240 ºC and 30 g·L-1 of ethanol. CONCLUSIONS: The approach hereby presented shows the valorization of MJ waste of AC variety to produce ethanol and ethylene with minimum processing inputs costs, demonstrating a successful route to convert a farm residue into a bio-based product with enhanced marketability.Peer ReviewedPostprint (published version

Recycling of rare earths from fluorescent lamp waste by the integration of solid-state chlorination, leaching and solvent extraction processes

Rare earths (RE) are currently considered some of the most critical elements, being crucial in future sustainable applications. Their high demand, price fluctuations, supply risk and geopolitical factors increase the interest in recovering RE from secondary sources such as pre-consumer scrap, industrial residues and end-of-life products. RE recovery from fluorescent lamp wastes and their subsequent selective separation was successful along a three-step process: (i) solid-state chlorination (SSC), (ii) leaching at pH 3 and (iii) solvent extraction. SSC is the key-step to separate RE from residual material. Optimal SSC parameters were set by using an experimental statistical design which allows for evaluating the cross effects between temperature, residence time and NH4Cl:waste ratio. The digestion step was optimized as well reaching a liquid:solid ratio (L:S) of 40 which accounted for a reduction of 20% in the use of water. Yttrium and Europium have been recovered separately from the pregnant solution by a four-stage cross-flow solvent extraction process combining Cyanex 923 and Cyanex 572 reaching initial purities = 94%. This approach is an integrated process for RE recycling from fluorescent lamp wastes, which contributes to reducing chemicals consumption at better process economy.Peer ReviewedPostprint (author's final draft

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 (¿H° < 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.Peer ReviewedPostprint (author's final draft