Search

Addressing critical environmental challenges such as greenhouse gas emissions, global warming, and eutrophication demands urgent and innovative solutions. In recent years, microalgae have emerged as a promising avenue for addressing these pressing issues. In this study, the combination of dairy and municipal wastewater is proposed as a culture medium for cultivating microalgae strains capable of sequestering atmospheric CO2. Specifically, the growth of Chlorella vulgaris was investigated using Bold's basal medium, along with varying concentrations of municipal and dairy wastewater, both with and without CO2 supplementation, to assess their CO2 capture potential. Concurrently, the efficiency of chemical oxygen demand (COD), total nitrogen, potassium, and phosphate removal from the wastewater was evaluated. Additionally, the combination of wastewater media with CO2 supplementation yielded the highest CO2 uptake rates, indicating the feasibility of simultaneous CO2 capture during microalgae cultivation. Media composition with 25% municipal wastewater: 75% dairy wastewater supplemented with CO2 demonstrated superior COD elimination with a higher percentage of nutrient removal from wastewater compared to other wastewater proportions. The nutrient removal capacity of aforementioned media also comes in line with high CO2 sequestration rate (13.57 mg L−1 h−1). These findings underscore the potential of utilizing wastewater from diverse sources as a viable culture medium for microalgae cultivation, facilitating concurrent CO2 capture and wastewater treatment. [ABSTRACT FROM AUTHOR]

The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample. [ABSTRACT FROM AUTHOR]

The Asurabandha area on the southern side of the main Sukinda Ultramafic Complex (SUC) in the State of Odisha hosts some irregular and sporadic chromitite bodies which are completely detached from the main SUC. The isolated chromitite bodies are highly altered. Chromitite samples from these isolated bodies have been studied using a polarising petrological microscope, scanning electron microscope (SEM), field emission-scanning electron microscope (FE-SEM), X-ray diffraction (XRD) and wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer and the findings are presented here. In this area, we have identified the associated silicate minerals with chromite to be primarily opal-CT and quartz, contrary to the conventional Fe–Mg silicates such as olivine, pyroxene, or serpentine, although in few instances, the Fe–Mg silicates are identified. The original Fe–Mg silicates have almost completely been replaced by the silica polymorphs. Occurrences of opal-CT and quartz have been identified from their prominent X-ray diffraction peaks at d-spacing of 4.10 Å (with a shoulder peak at 4.32 Å) and 3.34 Å, respectively. The phase compositions are also confirmed by SEM-EDAX analyses. The average composition of opal-CT was found to be (in wt.%) SiO2: 95.41, MgO: 1.75 and FeO: 1.74. The presence of MgO and FeO in the composition of opal-CT, along with relict mesh-like micro-structures, indicate its formation by silicification/opalization from serpentines. A low-temperature hydrothermal alteration process driven by Si- and CO2-rich fluids through fractures and fault zones might have caused the removal of Mg and Fe from primary ultramafic silicate minerals and precipitation of opal-CT. This replacement process involved the initial dissolution of serpentine with preferential leaching of the metallic ions (Mg, Fe) and simultaneous precipitation of amorphous silica to form possibly opal-A in the beginning and then to opal-CT which subsequently transforms to microquartz because of the ordering of structure and removal of water through the dissolution–precipitation mechanism. [ABSTRACT FROM AUTHOR]

To address the carbon dioxide (CO2) and other green-house gas (GHG) emission issues and combat climate change, various world summits have taken place starting with the United Nations Framework Convention on Climate Change (UNFCCC) at Rio in 1992 to the COP26 at Glasgow in 2021. Although the Paris Agreement of 2015, a legally binding international treaty intended to keep global average temperature rise below 2°C (preferably 1.5°C), it appears too tough a target considering the present day scenarios of insincerity by the advanced and rich nations. On the other hand, adaptation of CCS (carbon capture and storage) technologies in industrial scale have not yet been possible because of economic unviability. Although the western countries such as the USA and the EU have invested considerable amount of funds for R&D to make the CCS technologies successful, the developed technologies are only up to the pilot scale. More funding and focused R&D are needed to make the proven CCS technologies economic in industrial scales. The R&D efforts by other countries are still insignificant. India being the fourth largest emitter of GHGs in the world, is a signatory to most of the global treaties and is trying to adopt various CCS technologies. However, no significant progress has been made so far although some initiations have been observed after the recent pledge made by the Hon. Prime Minister of India in COP26 at Glasgow for a 'net zero' carbon by 2070. Industrial utilization of CO2 is negligible in the country except that Tata Steel Ltd. recently installed a demonstration carbon capture plant (5 TPD CO2) at its Jamshedpur works. There are no visible efforts from the power sectors who are one of the major contributors of CO2. Future availability of CCS technologies to Indian industries shall primarily be determined by the investments they make in R&D to develop the technologies on their own or in collaboration with research laboratories. Substituting carbon with green hydrogen and using renewable energy to run the steel plants would be desirable. Implementation of costly CCS technologies in India would need incentives from government as well as involvement and financial commitment from private industries which has been very low over the years. In this article we have taken a fresh stock of the situation with respect to the global targets set, efforts being made, technological interventions and their adaptability, R&D efforts required, funding opportunities, promises made, the gaps in available technologies, and target accomplishments. Indian status has been reviewed with respect to CCS: where does it stand, what are the challenges and what is the way forward for this fast-growing developing country to address the climate change keeping a balance with its fast growth rate. [ABSTRACT FROM AUTHOR]

Platinum group minerals (PGMs) belonging to laurite (RuS2) - erlichmanite (OsS2) solid solution series and Os-Ir-Ru alloys generally occur as minute inclusions (<10 μm) in both stratiform and podiform chromitite deposits. In a recent study of chromitite samples from Bangur chromite deposit in the Boula-Nuasahi ultramafic complex, Odisha, India, we found a relatively coarsegrained (~30 μm) laurite crystal in addition to other PGMs. This laurite occurs as an included crystal within a ferritchromite grain and has a chemical composition (wt%): Ru ~ 43-45, Os ~ 12-15, S ~ 35, Ir ~ 2-3 and As ~ 0.2, as measured by electron probe micro-analyzer. Due to the high osmium content, it is named as Oslaurite. The mode of occurrence, texture, structure and chemical composition of laurite support a magmatic origin for this mineral that might have crystallized at a temperature slightly lower than 1200°C. The unusual and complex oscillatory zoning (i.e. Os-rich and Os-poor bands) observed within the laurite could have developed below 1200°C (but above 1000°C) in a late magmatic stage due to local fluctuations in the surrounding thermodynamic conditions, primarily the sulphur fugacity. [ABSTRACT FROM AUTHOR]

The Tidding‐Mayodia ophiolites (TMO) exposed along the Lohit and Dibang river valleys in eastern Himalaya that have been considered as the extension of the Indus‐Tsangpo Suture Zone ophiolites are revisited to review their petrogenetic‐tectonic origin. The ophiolites consist of depleted harzburgite and dunite with lesser amounts of mafic rocks (gabbro intrusives, mafic dykes) and carbonates. The serpentinized peridotites consist of antigorite, lizardite, olivine, Cr‐spinel, and bastite with minor sulfide minerals. From SEM‐EDS studies, sulfide minerals were observed to be associated mainly with magnetites. The main sulfide mineral is pentlandite with minor millerite that exists as inclusions inside the pentlandite grains. Elemental mapping of these sulfides shows that they are mainly Ni‐(Co‐)‐bearing sulfides. The olivines are highly forsteritic (Fo = 95–96) while the Cr‐spinels show distinct Cr‐magnetite rims with a chromite core (Cr# = ~93). The serpentinized peridotites have whole‐rock compositions of SiO2 <47 wt% and high MgO (>36.37 wt%) and low Al2O3 (<1.21 wt%), CaO (<0.82 wt%), indicating the depleted nature of the parent rocks. Highly fractionated LREEs as compared to HREEs [(La/Yb)N = 2.62–13.22], and REE and Cr spinel chemistry modelling suggests that the studied peridotites have formed from ~22% partial melting of a depleted spinel lherzolite source which later underwent interactions with a high‐temperature silicate melt that caused enrichment in LREE and Cr of spinels. The parental melt compositions of Cr spinel yield their formation during arc tectonism (Al2O3melt = 6.28–7.65 wt%, FeO/MgO = 1.00–1.33). Furthermore, Mn and Zn concentrations in spinels, the occurrence of Cr magnetite rim in Cr‐spinels, presence of secondary olivine with higher Fo (~98), and occurrence of low‐temperature re‐equilibrated sulfide minerals, indicate that the rocks were subject to low‐temperature metamorphism. Based on this evidence, combined with data from previous studies, a tectonic model has been proposed for the genesis of the studied ophiolites. This model shows that the ophiolites have formed from the entrapment of depleted N‐MORB mantle in the mantle wedge of an intra‐oceanic subduction zone. During the nascent forearc regime, this mantle wedge underwent interactions with high‐temperature melts, which caused changes in their chemistry. Moreover, the rocks underwent interactions with low‐temperature fluids in the mature forearc, which caused the formation of sulfides and metamorphozed these rocks. [ABSTRACT FROM AUTHOR]

Tetrataenite is an equiatomic and highly ordered, non-cubic Fe-Ni alloy mineral that forms in meteorites from the distortion of fcc taenite due to extremely slow cooling. The mineral has drawn much attention of the scientific community because of its superb magnetic properties, which may make the phase an alternative to the REE-based permanent magnets. Barring only a few passing mentions, the mineral has never been described from any terrestrial rock. Here we report the characteristics of terrestrial tetrataenite from an ophiolite-hosted Ni-bearing magnetite body from the Indo-Myanmar ranges, northeast India. Although the mineral assemblage surrounding it is very similar to that found in the meteorites, the postulated cooling regimes cannot be similar. The mineral is formed as a consequence of hydrothermal alteration of ferromagnesian minerals of the olivine and pyroxene groups. Iron and nickel were released from the silicates and precipitated in the form of Fe-Ni alloy at low temperature in extremely reducing conditions with a lack of sulfur. Our findings suggest a low-temperature hydrothermal origin of tetrataenite warrants a re-examination of the Fe-Ni phase diagram at low temperatures and puts a question mark on the age-old concept of tetrataenite formation as due solely to extremely slow cooling of fcc taenite in meteorites. It also opens up a new vista for adoption of a hydrothermal route to synthesize this rare material. [ABSTRACT FROM AUTHOR]

Abstract: Occurrence of baddeleyite (ZrO2) which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin (CIOB). The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals (<3 μm) within ferromanganese concretionary growth bands. The mode of occurrence, textural features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite. For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in the form of baddeleyite within manganese nodules under oxic to sub-oxic conditions. [Copyright &y& Elsevier]