Scheelite-type rare earth vanadates TVO4 (T = Ho, Y, Dy) electrocatalysts: Investigation and comparison of T site variations towards bifunctional electrochemical sensing application

In the wake of the recent COVID-19 pandemic, antibiotics are now being used in unprecedented quantities across the globe, raising major concerns regarding pharmaceutical pollution and antimicrobial resistance (AMR). In view of the incoming tide of alarming apprehensions regarding their aftermath, it is critical to investigate control strategies that can halt their spread. Rare earth vanadates notable for their fundamental and technological significance are increasingly being used as electrochemical probes for the precise quantification of various pharmaceutical compounds. However, a comprehensive study of the role of the cationic site in tailoring the response mechanism is relatively unexplored. Hence, in this work we present a facile hydrothermal synthesis route of rare earth vanadates TVO4 (T = Ho, Y, Dy) as efficient electrocatalyst for the simultaneous detection of nitrofurazone (NF) and roxarsone (RX). There appears to be a significant correlation between T site substitution, morphological and the electrochemical properties of rare earth metal based vanadates. Following a comparative study of the electrochemical activity, the three rare-earth vanadates were found to respond differently depending on their composition of T sites. The results demonstrate that Dy-based vanadate displays increased electrical conductivity and rapid charge transfer characteristics. Thus, under optimal reaction conditions DyVO4- based electrodes imparts outstanding selectivity towards the detection of NF and RX with an extensive detection window of NF = 0.01–264 µM & RX = 0.01–21 µM and 36–264 µM and low detection limit (0.002, 0.0009 µM for NF and RX, respectively). In real-time samples, the proposed sensor reveals itself to be a reliable electrode material capable of detecting residues such as NF and RX. © 2022 Elsevier B.V.

A Comparative Study on the Export Competitiveness of Rare Earth Products from China, the United States, Russia and India

This paper evaluates and compares the export competitiveness of rare-earth products from China, the US, Russia, and India between 2006 and 2020 using the CMS model and the WRCA index. The results show that (1) the competitiveness of the four countries’ rare-earth products has changed differently. The overall competitiveness of rare-earth products of China, the US, and India has decreased, whereas the competitiveness of Russia’s rare-earth products has increased. (2) The factors inhibiting the development of the competitiveness of rare-earth products in the four countries are different. In China and India they are market factors and product factors, in the US it is the overall market share factor, and in Russia it is the market factor. (3) The competitiveness of rare-earth products varies greatly among the four countries. China has the highest rare-earth export competitiveness, whereas the US has significantly lower export competitiveness of rare-earth products than China. Russia and India do not have comparative advantages. (4) The four countries have different trends in the evolution of the competitiveness of rare-earth products. The export competitiveness of rare-earth products of China and India tends to decline, whereas that of the United States and Russia tends to rise. Based on the above findings, the paper puts forward corresponding policy recommendations.

CeO2-Based Heterogeneous Catalysts in Dry Reforming Methane and Steam Reforming Methane: A Short Review

Transitioning to lower carbon energy and environment sustainability requires a reduction in greenhouse gases such as carbon dioxide (CO2) and methane (CH4) that contribute to global warming. One of the most actively studied rare earth metal catalysts is cerium oxide (CeO2) which produces remarkable improvements in catalysts in dry reforming methane. This paper reviews the management of CO2 emissions and the recent advent and trends in bimetallic catalyst development utilizing CeO2 in dry reforming methane (DRM) and steam reforming methane (SRM) from 2015 to 2021 as a way to reduce greenhouse gas emissions. This paper focus on the identification of key trends in catalyst preparation using CeO2 and the effectiveness of the catalysts formulated.

Mining Waste as a Potential Additional Source of HREE and U for the European Green Deal: A Case Study of Bangka Island (Indonesia)

The European Commission has adopted the European Green Deal strategy, which aims to achieve climate neutrality in the EU by 2050. To achieve this goal, it is necessary to shift the economy toward the use of green and renewable energy. Critical raw materials (CRMs), Li, Co, REE, Te, Sc and others, are used in renewable energy sources (RES) production. The EU lacks its own CRM deposits, and additionally, the access to already identified deposits is limited, which is making the EU countries search for alternative CRM sources. One such source of CRMs may be mining waste generated on the Indonesian island of Bangka as a result of processing cassiterite-bearing sands. Studies of the mineral composition of the waste using the XRD method reveal rich contents of xenotime (0.79–17.55 wt%), monazite (1.55–21.23 wt%), zircon (1.87–64.35 wt%) and other minerals, carriers of valuable metals, such as Sn, Ti, Nb, Ta. The point mineral chemistry analyses were performed using EPMA. Xenotime is the main carrier of heavy rare earth elements (HREE), especially the “most critical” HREEs: Gd2O3 (1.42–7.16 wt%), Dy2O3 (2.28–11.21 wt%), Er2O3 (2.44–7.85 wt%), and Yb2O3 (1.71–7.10 wt%). Xenotime is characterized by a complex internal structure resulting from metasomatic processes occurring during their formation. In SEM-BSE imaging, they show zonation of internal structure, which is the effect of an HREE, Y, Si and U substitution in the crystal structure. On the other hand, thorite ThSiO4 and uranothorite (Th,U)SiO4 inclusions are present in xenotimes. The ICP-MS/ES studies of tailings reveal very high contents of HREE + Y (up to 7.58 wt%), U (up to 0.11), Th (up to 0.75 wt%) and Sc (132 ppm). A CRM source diversification is part of the strategy to ensure the security of raw materials for countries of the European Union and the green transformation of the continent. Bilateral EU–Indonesia cooperation in the geological exploration and development of primary and secondary sources may contribute to an increase in the supply of HREEs to the global market.

Preface

[...]a model of palaeo-flow dynamics, sediment dispersal pattern, depositional setting, cyclicity pattern and basin tectonics is put forward. [...]they suggest that the younger 40Ar/39Ar, Rb–Sr and U–Pb ages in the Kaladgi and Bhima basins could reflect the timing of post-depositional alteration events. [...]of the presence of terrigenous material within the stromatolites, whole-rock geochemical analyses for trace elements and rare earth elements cannot be used for interpretation of seawater chemistry and the redox conditions of the time.

Data on rare earth elements in different particle size fractions of topsoil for two small erosional landforms in central European Russia.

The pathways and behavior of rare earth elements (REEs) in the soil environment have been receiving greater significance due to their wide use in technological applications, agriculture, and medicine over the last two decades and insufficient information on their health effect and participation in soil and geochemical processes. In this paper, we report original data on rare earth elements in various particle size fractions separated from the topsoil horizons of two small erosional landforms located in an uncontaminated area of the central part of European Russia (the Middle Protva basin, the Kaluga region). Soil samples were collected from the top 10 cm along several soil transects. Soils were sampled at the landforms sides, bottoms, detrital fans and catchment areas considered as sources of solid matter. The sampling scheme used makes it possible to assess the REEs distribution from catchments to bottoms of the erosional landforms, as well as along their thalwegs. The collected bulk samples (n = 22) were physically fractionated and the concentrations of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu were determined in five particle size fractions (1000-250, 250-50, 50-10, 10-1 and <1 µm, n = 100) by ICP-MS using Elan-6100 spectrometer (Perkin Elmer Inc., USA). The data obtained also include the concentrations of Fe and Mn (ICP-AES), as well as the information on the total content of organic carbon (TOC), pH and particle size distribution of the bulk samples. The obtained dataset can be used for various purposes: it is suitable as a baseline for the assessment of pollution levels, exploring natural and anthropogenic anomalies, for revealing the association of REEs with specific particle size fractions and detecting the effect of parent material and lateral translocations of soil material and soil particles on the REEs levels.