Green and Effective Preparation of α-Hydroxyphosphonates by Ecocatalysis.

A green and effective approach for the synthesis of structurally diversed α-hydroxyphosphonates via hydrophosphonylation of aldehydes under solventless conditions and promoted by biosourced catalysts, called ecocatalysts "Eco-MgZnOx" is presented. Ecocatalysts were prepared from Zn-hyperaccumulating plant species Arabidopsis halleri, with simple and benign thermal treatment of leaves rich in Zn, and without any further chemical treatment. The elemental composition and structure of Eco-MgZnOx were characterized by MP-AES, XRPD, HRTEM, and STEM-EDX techniques. These analyses revealed a natural richness in two unusual and valuable mixed zinc-magnesium and iron-magnesium oxides. The ecocatalysts were employed in this study to demonstrate their potential use in hydrophosphonylation of aldehydes, leading to various α-hydroxyphosphonate derivatives, which are critical building blocks in the modern chemical industry. Computational chemistry was performed to help discriminate the role of some of the constituents of the mixed oxide ecocatalysts. High conversions, broad substrate scope, mild reaction conditions, and easy purification of the final products together with simplicity of the preparation of the ecocatalysts are the major advantages of the presented protocol. Additionally, Eco-MgZnOx-P could be recovered and reused for up to five times.

New biomaterials for Ni biosorption turned into catalysts for Suzuki-Miyaura cross coupling of aryl iodides in green conditions.

In parallel with increasing Ni production and utilisation, Ni pollution in the soil-water continuum has become an alarming and global problem. Solutions for removing Ni from industrial effluents have been widely investigated and biosorption has emerged as an efficient, cost-effective, scalable and sustainable alternative for water treatment. However, the biosorption capacity is limited by the chemical composition of the biomaterial and the Ni-enriched biomaterials are rarely valorised. In this work, the biosorption capacity of three abundant biomaterials with different chemical properties - water hyacinth, coffee grounds and pinecones - was studied before and after functionalization, and reached a maximum biosorption capacity of 51 mg g-1 of Ni(ii). A bioinspired functionalization approach was investigated introducing carboxylate moieties and was conducted in green conditions. The Ni-enriched biomaterials were valorised by transformation into catalysts, which were characterised by MP-AES and XRPD. Their characterisation revealed a structure similar to nickel formate, and hence the Eco-Ni(HCOO)2 catalysts were tested in Suzuki-Miyaura reactions. Several aryl iodides were successfully cross-coupled to phenylboronic acids using Eco-Ni(HCOO)2 without any ligand, a mild and green base in a mixture of green solvents.

Thermochemical Route for Extraction and Recycling of Critical, Strategic and High-Value Elements from By-Products and End-of-Life Materials, Part II: Processing in Presence of Halogenated Atmosphere.

During the treatment of copper anode slime (CAS) under an air atmosphere, several aspects of the interactions of its main components (CuAgSe, Cu2-xSeyS1-y, Ag3AuSe2) with oxygen were described in Part I. As a comparative and complementary study, this work deals with the thermal behavior of CAS under air in the presence of polyvinyl chloride (PVC) between 195 and 770 °C. The preliminary thermal treatment of an e-waste sample containing brominated substances was also performed. The reaction products were systematically analyzed by scanning electron microscopy through energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to investigate the thermal behaviors of the studied samples in a halogenated medium. At low temperatures, the copper, silver and selenium compounds of the CAS reacted with the HCl, issued from PVC degradation, leading to the formation of their respective chlorides. Bromides of valuable metals (Cu, Pb, Sn…) were synthesized during the e-waste treatment at 500 °C and they were distributed between the solid residue and gaseous phase. The data obtained give an insight into the reactivity of several metals towards halogenated substances, which may be valuable information for conducting the extraction and recycling of targeted elements from industrial by-products and end-of-life materials by a thermochemical route.

A zero-waste process for the management of MSWI fly ashes: production of ordinary Portland cement.

Municipal solid waste incineration (MSWI) fly ashes are hazardous waste since they contain organic pollutants, heavy metals and an important amount of various soluble salts. However their chemical composition is interesting for their valorization in cement production. The objective of this paper is to assess the possibility of MSWI fly ashes reuse as cement raw meal, after pre-treatment, at a laboratory scale. The environmental impact has also been studied (analyses of the metals, of dioxins and furans and leaching tests on clinker produced). Experimental results show that the replacement of MSWI fly ash could be taken up to 30% in the raw mixes, according to the chemical composition of the MSWI fly ashes. This substitution is also to be refined according to the content of hazardous elements contents. This study also shows that the pre-treatment must be well carried out in order to limit the alkaline contents which may affect the quality of the cementitious phases.

Thermochemical Route for Extraction and Recycling of Critical, Strategic and High Value Elements from By-Products and End-of-Life Materials, Part I: Treatment of a Copper By-Product in Air Atmosphere.

Development of our modern society requests a number of critical and strategic elements (platinum group metals, In, Ga, Ge…) and high value added elements (Au, Ag, Se, Te, Ni…) which are often concentrated in by-products during the extraction of base metals (Cu, Pb, Zn…). Further, recycling of end-of-life materials employed in high technology, renewable energy and transport by conventional extractive processes also leads to the concentration of such chemical elements and their compounds in metallurgical by-products and/or co-products. One of these materials, copper anode slime (CAS), derived from a copper electrolytic refining factory, was used for this study. The sample was subjected to isothermal treatment from 225 to 770 °C under air atmosphere and the reaction products were systematically analyzed by scanning electron microscopy through energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to investigate the thermal behavior of the treated sample. The main components of the anode slime (CuAgSe, Cu2-xSeyS1-y, Ag3AuSe2) react with oxygen, producing mostly copper and selenium oxides as well as Ag-Au alloys as final products at temperatures higher than 500 °C. Selenium dioxide (SeO2) is volatilized and recovered in pure state by cooling the gaseous phase, whilst copper(II) oxide, silver, gold and tellurium remain in the treatment residue.

Biosourced Polymetallic Catalysis: A Surprising and Efficient Means to Promote the Knoevenagel Condensation.

Zn hyperaccumulator (Arabidobsis halleri) and Zn accumulator Salix "Tordis" (Salix schwerinii × Salix viminalis) have shown their interest in the phytoextraction of polluted brownfields. Herein, we explore a novel methodology based on the chemical valorization of Zn-rich biomass produced by these metallophyte plants. The approach is based on the use of polymetallic salts derived from plants as bio-based catalysts in organic chemistry. The formed ecocatalysts were characterized via ICP-MS, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) in order to precise the chemical composition, structure, and behavior of the formed materials. The Doebner-Knoevenagel reaction was chosen as model reaction to study their synthetic potential. Significant differences to usual catalysts such as zinc (II) chloride are observed. They can principally be related to a mixture of unusual mineral species. DFT calculations were carried out on these salts in the context of the Gutmann theory. They allow the rationalization of experimental results. Finally, these new bio-based polymetallic catalysts illustrated the interest of this concept for green and sustainable catalysis.

Hydrodemetallation and Hydrodesulfurization Spent Catalysts Elemental Analysis: Comparison of Wavelength Dispersive X-ray Fluorescence and Atomic Emission Spectrometries.

Petroleum industries continuously consume catalysts on very large scales. The recycling of spent catalysts is thus of major economic and environmental importance and its first step consists of the characterization of the valuable metal content. Wavelength dispersive X-ray fluorescence (WDXRF) analysis is compared with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the analysis of five samples of spent hydrodesulphurization (HDS) and hydrodemetallization (HDM) catalysts. The elements are considered for their economic interest (Co, Ni, Mo, and V) or for the problems that can arise when they are present in the sample in significant quantities (Al, As, P, Fe). First, the systematic comparison of the analysis of known synthetic samples was performed. The originality here is that the samples were first beaded with lithium tetraborate (Li2B4O7) for WDXRF analysis and then dissolved in hot HCl 6M for ICP-AES measurements. With this processing, we were able to clearly identify the origin of analytical problems when they arose. Second, the semi-quantitative protocol of WDXRF is compared with the quantitative procedure. Finally, the analysis of the spent catalysts is presented and the information gained by the systematic comparison of ICP-AES and WDXRF is shared. The interest of the simultaneous determination by the two techniques when such complicated heterogeneous matrices are involved is clearly demonstrated.

End-of-life nickel-cadmium accumulators: characterization of electrode materials and industrial Black Mass.

The aim of this paper is the characterization of spent NiCd batteries and the characterization of an industrial Black Mass obtained after crushing spent NiCd batteries and physical separation in a treatment plant. The characterization was first performed with five cylindrical NiCd batteries which were manually dismantled. Their characterization includes mass balance of the components, active powders elemental analysis and phase identification by X-ray powder diffraction. Chemical speciation of the two metals was also investigated. For cadmium, speciation was previously developed on solid synthetic samples. In a spent battery, the active powders correspond to about 43% of the battery weight. The other components are the separator and polymeric pieces (5%), the support plates (25%) and the carbon steel external case (27%). The sequential procedure shows that the nickel in the positive powders from the dismantled Ni-Cd batteries is distributed between Ni0 (39.7%), Ni(OH)2 (58.5%) and NiOOH (1.8%). Cadmium in the negative powder is about 99.9% as the Cd(OH)2 form with 0.1% of metal cadmium. In the industrial Black Mass, the distribution of cadmium is the same, whereas the distribution of nickel is Ni0 (46.9%), Ni(OH)2 (43.2%) and NiOOH (9.9%). This material contains also 1.8% cobalt and approx. 1% iron.