Rare earths (RE), chemically uniform group of elements due to similar physicochemical behavior, are termed as lanthanides. Natural occurrence depends on the geological circumstances and has been of long interest for geologist as tools for further scientific research into the region of ores, rocks, and oceanic water. The review paper mainly focuses to provide scientific literature about rare earth elements (REEs) with potential environmental and health effects in understanding the research. This is the initial review of RE speciation and bioavailability with current initiative toward development needs and research perceptive. In this paper, we have also discussed mineralogy, extraction, geochemistry, analytical methods of rare earth elements. In this study, REEs with their transformation and vertical distribution in different environments such as fresh and seawater, sediments, soil, weathering, transport, and solubility have been reported with most recent literature along key methods of findings. Speciation and bioavailability have been discussed in detail with special emphasis on soil, plant, and aquatic ecosystems and their impacts on the environment. This review shows that REE gained more importance in last few years due to their detrimental effects on living organisms, so their speciation, bioavailability, and composition are much more important to evaluate their health risks and are discussed thoroughly as well.

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Rare earth elements (REEs) from ex-mining area in Lahat, Perak, Malaysia were investigated in different plant species belonging to Cyperaceae, Gleicheniaceae and Melastomataceae families and soil using inductively coupled plasma mass spectrometry (ICP-MS). The plant samples were divided into root, stem, leaves and flowers to determine the variations in the distribution of REEs, their uptake capacity, and bioavailability. The aims of the work were to evaluate REEs uptake levels and bioavailability in plants. The work observed highest amount of cerium (Ce) 425.5 mg kg -1 in the soil samples. Light rare earth elements (LREEs) were found in greater concentration in plants and soil samples than heavy rare earth elements (HREEs). Our findings suggest Dicranopteris dichotoma, Dicranopteris linearis (Burn) (B) and Cyperus rotundus L. as hyper accumulative for REEs. This study accounts all the REEs indicating LREEs (Sc, Y, La, Ce, Pr, Nd, Eu, and Gd) in abundance with their uptake capacity, accumulation and transfer to other plant parts. Transfer factor (TF), bioconcentration factor (BCF) and bioaccumulation factors (BAF) were also calculated to estimate the toxicity of REEs in the ex-mining area. BCF and BAF values found highest for yttrium and ytterbium.

No abstract

A study was carried out to determine the level of rare earth elements (REEs) in water and sediment samples from ex-mining lakes and River in Kinta Valley, Perak, Malaysia. Surface water and sediments from an ex-mining lake and Kinta River water samples were analyzed for REEs by inductively coupled plasma mass spectrometry. The total concentration of REEs in the ex-mining lake water samples and sediments were found to be 3685 mg/l and 14159 mg/kg, respectively, while the total concentration of REEs in Kinta River water sample was found to be 1224 mg/l. REEs in mining lake water were found to be within 2.42 mg/l (Tb) to 46.50 mg/l (Ce), while for the Kinta River, it was 1.33 mg/l (Ho) to 29.95 mg/l (Ce). Sediment samples were also found with REEs from 9.81 mg/kg (Ho) to 765.84 mg/kg (Ce). Ce showed the highest average concentrations for mining lake (3.88 to 49.08 mg/l) and Kinta River (4.44 to 33.15 mg/l) water samples, while the concentration of La was the highest (11.59 to 771.61 mg/kg) in the mining lake sediment. Lu was shown to have the highest enrichment of REEs in ex-mining lake sediments (107.3). Multivariate statistical analyses such as factor analysis and principal component analysis indicated that REEs were associated and controlled by mixed origin, with similar contributions from anthropogenic and geogenic sources. The speciation study of REEs in ex-tin mining sediments using a modified five-stage sequential extraction procedure indicated that yttrium (Y), gadolinium (Gd), and lanthanum (La) were obtained at higher percentages from the adsorbed/exchanged/carbonate fraction. The average potential mobility of the REEs was arranged in a descending order: Yb > Gd > Y = Dy > Pr > Er > Tm > Eu > Nd > Tb > Sc > Lu > Ce > La, implying that under favorable conditions, these REEs could be released and subsequently pollute the environment.