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Rare earth elements (REEs) are strategic materials widely used in different applications from Information and Communication Technologies (ICT) to catalysis, which are expected to grow more in the future. In order to reduce the impact of market price and reduce the environmental effect from soil extraction, recovery/purification strategies should be exploited. This paper presents a combined acid-leaching/oxalate precipitation process to recover lanthanum from spent FCC catalyst using nitric acid. Preferred to hydrochloric and sulphuric acid (preliminary assessed), HNO3 showed a good capability to completely leach lanthanum. The combination with an oxalate precipitation step allowed demonstrating that a highly pure (&gt, 98% w/w) lanthanum solid can be recovered, with a neglectable amount of poisoning metals (Ni, V) contained into the spent catalyst. This could open a reliable industrial perspective to recover and purify REE in the view of a sustainable recycling strategy.

Plastic has become an essential part of our modern lifestyle and its global diffusion has led to a significant increase in the production of related waste, with obvious repercussions on the environment and on the entire sustainability chain. Recycling this kind of materials in the field of civil and industrial engineering is considered an ecological and economical solution due to the advantages it can offer. This paper represents the results of experimental investigations of mechanical strength, hygro-thermal and durability properties of two kinds of products: urban tiles (90 % PVC powder and 10 % polyurethane resin) and cement-based mortars reinforced with PVC compound coming out of electric cable protective sheath. The manufactured mortars were obtained by the volumetric substitution of the sand with five different percentages of plastic waste, from 10 % to 50 %. Plastic aggregates reduce density, causing a decrease in flexural and compressive strength of mortars. Nevertheless, the presence of plastic aggregate leads to a significant improvement of thermal insulation and shows a greater resistance to capillary water absorption compared to the reference one. The mechanical tests after two different cycles of accelerated solar aging of urban tiles demonstrated the feasibility of its use for external flooring (green parking). These results foster future studies about the development of increasingly eco-sustainable building materials.

Phenol is a major component in the scrubber wastewater used for syngas purification in biomass-based gasification plants. Adsorption is a common strategy for wastewater purification, and carbon materials, such as activated carbons and biochar, may be used for its remediation. In this work, we compare the adsorption behavior towards phenol of two biochar samples, produced by pyrolysis and gasification of lignocellulose biomass, with two commercial activated carbons. Obtained data were also used to assess the effect of textural properties (i.e., surface area) on phenol removal. Continuous tests in lab-scale columns were also carried out and the obtained data were processed with literature models in order to obtain design parameters for scale-up. Results clearly indicate the superiority of activated carbons due to the higher pore volume, although biomass-derived char may be more suitable from an economic and environmental point of view. The phenol adsorption capacity increases from about 65 m/g for gasification biochar to about 270 mg/g for the commercial activated carbon. Correspondingly, service time of commercial activated carbons was found to be about six times higher than that of gasification biochar. Finally, results indicate that phenol may be used as a model for characterizing the adsorption capacity of the investigated carbon materials, but in the case of real waste water the carbon usage rate should be considered at least 1.5 times higher than that calculated for phenol.

Building construction technology using clay soil in various forms, already known since ancient times, presents a great potential to regulate indoor humidity, to reduce the indirect impact of construction sector on the environment and on energy consumption. Extensive studies have also been done on the effects of natural fibers on the mechanical and physical behaviour of composite materials in terms of strength, energy efficiency and impact resistance. This work is focused on some natural fiber composites made from different mixtures containing clay soil with different percentages of jute, straw and basalt fibers, in order to determine the ideal mixture between clay and fibers providing the optimum values of thermal inertia, mechanical performance and shrinkage able to improve the energy efficiency of buildings. The mechanical, physical and thermal properties of some specimens have been investigated. The obtained results show an improved mechanical strength and a better thermal conductivity of the clay composite material. © 2018, Mathematical Modelling of Engineering Problems.

Yttrium is a strategical material for its several usages in a wide range of industrial production. For this reason, improving the recovery of Yttrium has become a crucial focus for international research. In this scientific activity, the utilization of two extractants, 2-ethylhexyl-mono 2-ethylhexyl ester phosphonic acid (P-507) and sec-octylphenoxy acetic acid (CA-12), working in a synergistic extracting system, has been tested. A series of trials have been carried out to optimize the experimental conditions in order to separate yttrium from a mix of heavy rare earths in chloride media. Tests with different relative concentrations of extractants and a phase modifier (TPB, trybutyl phosphate), with different presaponification rate, have been performed to evaluate the behavior of the synergistic system. Results are very promising to recover and separate yttrium with a high purity. © 2017, The Minerals, Metals & Materials Society.

The solvent extraction technique is the only industrial way used to separate and purificate yttrium from other rare earths. In order to improve this process several extractants have been tested during last years. In this work, the behavior of sec-octylphenoxy acetic acid (CA-12) in Yttrium recovery from high concentrated heavy rare earth mixture was investigated. Sodium hydroxide solution was used in order to presaponify organic phase composed by CA-12 and Tributyl phosphate (TBP) diluted in kerosene. In the investigated condition, TBP confirmed its role of phase modifier not significantly altering the extraction behavior of CA-12. The CA-12-TBP system showed a high affinity in extraction for lighter rare earths such as Sm, Eu, and Gd, leaving yttrium in aqueous phase. Using a feed concentration (∑ [RE]) of 1M, organic mixture is capable to extract around the 70% of metals in a single extraction test showing this extraction sequence Y < Lu < Yb < Tm < Er < Ho < Dy < Tb < Gd < Eu < Sm. Moreover for [CA-12] = 1.79 M and [RE] = 2M the instability of extraction system occurs. © 2017, The Minerals, Metals & Materials Society.

A comparison among (2-ethylhexyl)-mono (2-ethylhexyl) ester Phosphonic acid (P507), Secondary-octyl phenoxy acetic acid (CA-12) and Bis(2, 4, 4-trimethylpentyl) phosphinic acid (Cyanex272), in heavy rare earths separation via hydrometallurgical processes has been investigated. The separation coefficients, β, were obtained and the extraction selectivity has been evaluated using a mixture of heavy rare earths from Samarium to Ytterbium. The experimental results indicated that P507 and Cyanex 272 display a greater affinity for heavier rare earths while CA12 proved to be more effective for the lighter rare earth metals.

The rare earth elements are essential for a diverse and expanding array of high-technology applications, which constitute an important part of the industrial economy of the 21st century. As a matter of fact, rare earth has been listed in the category of strategic elements in many countries becoming a core business for international research. Experimental tests have been carried out on a bench scale battery of mixer settler composed of 24 stages, each one with a volume of 150 ml. These trials have been performed at room temperature checked by a micro-climatic control system. The battery was setted in two sections: extraction and scrubbing section. Rare earths concentrations were obtained by ICP-OES analysis made on aqueous phase and on the stripped from organic phase. We obtained a complete separation of light rare earth (La, Ce, Pr, Nd) in two sub-groups: La/Ce and Pr/Nd.