Hydrothermal Products Research Articles

Magnetic properties of bauxites and pre-fused hydrothermal product (zeolite)

Bauxites are deposits rich in aluminium and iron oxides/hydroxides, formed by the weathering of aluminosilicates rocks under warm and humid conditions. Due to their mineralogical composition, bauxites represent the primary source for aluminum and, subordinately, iron production. However, these sediments rich in Si and Al can be also used as raw material for the synthesis of zeolite with magnetic properties thanks to the high availability of Fe. In this work, three bauxite samples collected from Upper Cretaceous deposits of southern Italy were characterized for their magnetic parameters and used for the synthesis of zeolite with LTA topology (zeolite A). The results indicate differences in antiferromagnetic behaviour among the three raw materials. All the synthetic products, instead, display the same antiferromagnetic behaviour thus suggesting that the method used for the zeolite crystallization neutralizes the parameters responsible for raw bauxite magnetic differences.

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability.

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Lime-assisted hydrothermal humification and carbonization of sugar beet pulp: Unveiling the yield, quality, and phytotoxicity of products

Hydrothermal carbonization (HTC) solid and liquid products may inhibit seed germination, necessitating post-treatment. The hydrothermal humification (HTH) method addresses this drawback by transforming inhibitory compounds, such as aromatics, into artificial humic acids (AHAs) and artificial fulvic acids (AFAs). This study introduces a novel approach by investigating the substitution of the commonly used alkaline agent in HTH, KOH, with hydrated lime to develop cost-effective hydrothermal fertilizers from sugar beet pulp, enriching them with AHAs. It assesses the effects of lime on AHA production and soluble organic compounds compared to KOH. The results indicate that lime significantly reduces furans (from 560 to 3.15 mg/kg DM in solid and from 344 to 3.86 mg/L in process liquid) and boosts sugars and organic acids, especially lactic acid (from 4.70 to 65.82 g/kg DM in solid and from 4.05 to 22.89 mg/L in process liquid), increasing hydrochar yield (68.8% with lime vs. 27.4% with KOH). Despite the lower AHA production with lime compared to KOH (3.47% vs. 15.50%), lime-treated hydrothermal products are abundant in calcium and magnesium, boasting a pH of 7. This property presents a safer and more efficient alternative to hydrothermal fertilizers. The characterization of AHAs aligns with standard and natural humic substances, while lime-assisted HTH products, applied at a level of 0.01% w/w, could significantly enhance wheat growth and nutrient uptake compared to the control group. Importantly, these products show no toxicity on Daphnia magna, underscoring their potential for sustainable agriculture.

Catalyzed hydrothermal treatment of oily sludge: A review

Oily sludge is a common by-product of the petroleum exploration industry, which is rich in resources and has strong toxicity. It is categorized as hazardous waste in many nations worldwide. Owing to the distinct physical and chemical characteristics of sub/supercritical water, the application of hydrothermal conversion technology, which uses sub/supercritical water as a medium, has been growing in the utilization of resources and the safe disposal of oily sludge. In this article, the research on the oxygen-free hydrothermal transformation of oil sludge, including hydrothermal carbonization, hydrothermal liquefaction, hydrothermal upgrading, and supercritical water gasification, is reviewed. Due to the significant impact of nitrogenous and sulfurous compounds in sludge on hydrothermal conversion products, the hydrogenation conversion, reaction path, and kinetics for these two compounds were discussed. Finally, a summary and comparison of the studies conducted on carriers and catalysts in hydrothermal processes are provided. This review can offer recommendations for future studies, as well as guidance for the hydrothermal catalytic treatment of oily sludge.

Evaluation of the Basic Property Evaluation of Eco-powder, a Hydrothermal Synthesis Product for Improving Waste Vinyl Recycling Efficiency

Evaluation of the Basic Property Evaluation of Eco-powder, a Hydrothermal Synthesis Product for Improving Waste Vinyl Recycling Efficiency

Hydrothermal transformation of fly ash to tobermorite or katoite: Impact of Ca and Si concentration in the liquid phase without alkali activation

In the study of hydrothermal conversion of fly ash to calcium silicate hydrates (C–S–H), the concentration of Ca and Si in the liquid phase plays a vital role in determining the hydrothermal transformation results. This paper selected a fly ash as a research object, which can leach a high Si concentration into the solution in the hydrothermal process even in a slight alkaline solution, based on a new finding when studying the alkali dissolution kinetics of different fly ashes. To explore the effects of Ca and Si concentrations in the liquid phase on the hydrothermal transformation of fly ash to tobermorite or katoite, Na2SiO3 (Na2O·xSiO2·yH2O) and CaSO4 were used to change the concentration of Si and Ca in the liquid in the hydrothermal system. Characterization methods such as XRD, SEM, infrared spectroscopy, and solid-state nuclear magnetic resonance indicated that a little more concentration of Si can promote the transformation from fly ash to tobermorite and persuade the conversion of the Si–O tetrahedron in C–S–H from Q2 to Q3 and Q4. However, too high a liquid Si concentration made the hydrothermal product change to colloidal calcium silicate. On the other hand, a high Ca concentration in the liquid was found to lead to the conversion of the hydrothermal product from tobermorite to katoite. According to the above results, the deep transformation from fly ash to tobermorite under the conditions of a low temperature of 160 °C and no extra alkali addition was achieved by the induction of a small quantity of Na2SiO3.

Regulating the distribution of phosphorus in sewage sludge hydrothermal carbonization products by complexation pretreatment

In this study, we investigated the effects of the concentrations of four pretreatment complexing reagents, namely ascorbic acid (AS), citric acid (CA), N, N-bis (carboxymethyl) glutamic acid (GLDA), and ethylenediaminetetraacetic acid (EDTA), on the phosphorus contents and forms in hydrothermally carbonized sludge products. The results showed that among the four complexing reagents, EDTA had the greatest effect on the phosphorus transfer from the solid phase to the liquid phase during the hydrothermal process of the sludge, followed, respectively, by GLDA, CA, and AS. The phosphorus proportion of the liquid phase was 63.96% under hydrothermal process temperature, reaction time, and EDTA concentration of 160 °C, 60 min, and 0.2 mol/L, respectively. The results showed formations of EDTA complexes with Ca, Fe, and Al in the sludge, releasing phosphorus bound to the metal ions into the liquid phase. The highest total phosphorus concentration in the liquid phase was 2533.31 mg/L following the increase in the hydrothermal process temperature from 100 to 160 °C. However, the Fe and Al-EDTA complexes were thermally decomposed after continuously increasing the hydrothermal process temperature to 240 °C, resulting in a readsorption of phosphorus to the solid phase with Fe, Al, and other metals and, consequently, decreasing the phosphorus content to 880.93 mg/L in the liquid phase. The results of this study provide a scientific basis for regulating phosphorus distribution in the solid and liquid phases of hydrothermally carbonized sludge products and effectively recovering phosphorus in the liquid phase.

Solvent processing for improved separation of hydrothermal liquefaction products

Solvent extraction and separation of HTL products using naphtha range hydrocarbons was studied with the aim of decreasing operational hazards while improving scalability, reliability, and yields.

Hydrothermal signatures and prospecting indicators in sediments along the Carlsberg Ridge

As the most widespread hydrothermal products in the oceans, metalliferous sediments are particularly useful in prospecting for seafloor massive sulfide (SMS) deposits. A comparative study of metalliferous sediments from two types of hydrothermal fields and the background sediments along the Carlsberg Ridge has been performed to reveal their hydrothermal signatures and to determine the prospecting indicators for SMS deposits. Cu–Fe–Zn sulfides, sulfates, Fe-oxides, and Fe-oxyhydroxides are dominant in the near-vent sediments from the basalt-hosted hydrothermal fields. The near-vent sediments from the ultramafic-hosted field are abundant in detrital minerals of ultramafic source in addition to the minerals mentioned above in the basalt-hosted fields. Sulfide minerals with large grains are mainly deposited close to the vent, and as the distance from the vent increases, the grain size and abundance of the minerals rapidly decrease. Geochemically, the near-vent sediments in the basalt-hosted hydrothermal fields are abundant in Fe, Cu, Zn, Ag, Pb, Mo, Co, U, V, and P, whereas the sediments from the ultramafic-hosted system are enriched in Fe, Mn, Cu, Zn, Ag, Pb, Mo, Co, Mg, Ni, Cr, U, V, and P. The enrichment of these elements and element ratios, such as (Fe + Mn)/Al, Fe/Ti, Al/(Al + Fe + Mn), Cu/Fe, Zn/Fe, U/Fe, and V/Fe, can be indicators of the intensity of the hydrothermal inputs and the distance to the SMS deposits. Temporal and spatial variations of hydrothermally derived elements (e.g., Fe, Cu, Zn, and Pb) in sediment cores can serve as effective tools for reconstructing the hydrothermal history, evaluating the mineralization potential, and tracing inactive/buried SMS deposits. Finally, a prospecting model and method for SMS deposits is proposed based on the prospecting indicators revealed by the sediment study, combined with other prospecting indicators generally used during marine exploration. The results can provide guidance for the prospecting of hydrothermal fields and SMS deposits.

Ammonium-Bearing Fluorapophyllite-(K) in the Magnesian Skarns from Aleului Valley, Pietroasa, Romania

An ammonium-bearing fluorapophyllite-(K) occurs as a late hydrothermal product in the outer endoskarn zone from Aleului Valley (N 46°37′04″, E 22°35′22″), located at the contact of the granodiorite laccolith from Pietroasa, of Upper Cretaceous age, with Anisian dolostones. Associated minerals are wollastonite, K feldspar, diopside, fluorapatite, talc, and pectolite. The chemical structural formula is [K0.985Na0.012(NH4)0.076]Σ=1.073(Ca4.009Mn0.001Fe2+0.003Mg0.002Ba0.001)Σ=4.016(Si7.953Al0.047) O20.029[F0.899(OH)0.101]·8.059H2O. The structure was successfully refined as tetragonal, space group P4/mnc, with cell parameters of a = 8.9685(1) Å and c = 15.7885(5) Å. The indices of refraction are ω = 1.534(1) and ε = 1.536(1). The calculated density is Dx = 2.381 g/cm3, in good agreement with the measured density, Dm = 2.379(4) g/cm3. The thermal analysis shows that the mineral completely dehydrates at up to 450 °C (endothermic effects at 330, 371, and 448 °C) and loses ammonium at 634 °C. In the infrared spectra, the multiplicity of the bands assumed to be silicate modes (1ν1 + 3ν3 + 2ν2 + 3ν4) agrees with the reduction in the symmetry of the SiO44− ion from Td to Cδ. Fluorapophyllite-(K) from Aleului Valley is of late hydrothermal origin and crystallized from F-rich fluids originating from the granodiorite intrusion, which mobilized K, Ca, and Si from the pre-existing feldspar.

Evidence of a distal axis inactive high-temperature hydrothermal field on the ultraslow spreading Southwest Indian Ridge: Insights from mineralogy and geochemistry studies

The development of hydrothermal activities on mid-ocean ridges is primarily influenced by magmatic and tectonic activities close to the ridge axis. On slow and ultraslow spreading ridges featured by limited magma supply, prolonged hydrothermal activity can also occur in non-transform offsets (NTO), where sustained ultramafic-related hydrothermal circulation happens due to prolonged hydrothermal processes associated with the expose of ultramafic rocks. In contrast, basalt-hosted hydrothermal fields are barely developed in NTOs, especially in off-axis area, due to insufficient magma supply. In this study, we reported the occurrence of a distal axis (∼9.5 km) basalt-hosted hydrothermal field (50.63°E) on the NTO of segment 27 of the ultraslow spreading Southwest Indian ridge. The hydrothermal products are characterized by layered crusts mainly composed of oxides, such as limonite and goethite, rich in Fe and depleted in Si. These crusts contain high contents of trace elements derived from seawater, such as P, As, Mo, U, and Sb and show REE pattens with negative Eu and mostly positive Ce anomalies. However, the high Cu content (1.82 ± 0.89 wt%, N = 27), low absorption ratio of Cu (18.39 ± 12.71%, N = 9), and residual chalcopyrite altered by goethite suggest prior high-temperature hydrothermal activity. Lead isotopic composition with basaltic rocks signatures that distinct from those of low-temperature crusts of seawater origin also support this conclusion. The Fe-rich crusts appears to be the result of high-temperature sulfides altered by late-stage low-temperature diffuse flow. This field is currently the furthest known distal axis basalt-hosted hydrothermal field located in NTOs of ultraslow spreading ridges. The hydrothermal circulation is likely due to a combination of off-axis normal fault and gabbro diking. Our results emphasize the occurrence of distal axis basalt-hosted high-temperature hydrothermal activities on NTOs of ultraslow spreading ridges, and may lead to an increased estimation of hydrothermal heat and chemical influx to the ocean.

Hydrothermal liquefaction of representative to Israel food waste model

In this study, we examined the hydrothermal liquefaction (HTL) pathway to reduce food waste environmental impacts by converting it into bio-crude and biochar. The yield and properties of these products depend on the composition of the feedstock and process parameters. We developed a model of household food waste based on Israel national waste survey. To investigate the effects of catalysts type, we examined the influence of dolime, dolomite, phosphate and potassium carbonate on products yields and composition. Additionally, we analyzed the role of the process parameters, including solid load, residence time, catalyst concentration, and temperature, on the yield and the properties of the hydrothermal liquefaction reaction products, such as bio-crude, biochar, and aqueous phase solubles. The experimental results show absolute bio-crude yield ranging from 6.61w% to 29.36w% and biochar yield ranging from 12.29w% to 40.73w% from the initial waste. Furthermore, 13.78w% to 33.98w% of the feed material was found in the aqueous phases and 6.15w% to 8.94w% was measured in the gas phase. The addition of catalysts positively influenced the bio-crude yield. A process temperature of 280 °C improved the energy recovery and increased product yield, resulting in a reduction in the oxygen content of the bio-crude. All bio-crudes showed undetectable sulfur levels and exhibited HHVs ranging from 30.24 MJ/kg to 37.94 MJ/kg, while biochar had HHVs of 31.29 MJ/kg to 31.84 MJ/kg. On the Israel national level, the bio-crude derived from food waste demonstrates the potential to meet up to 31.4 % of Israel's marine fuel demand assuming bio-crude yield of 29 %, as achieved in this study.

Characterization of the Angat Ophiolite: New insights from bulk major and trace element geochemistry and petrographic analysis

The Angat Ophiolitic Complex, located north-northeast of Manila, Luzon is perhaps one of Luzon’s most fundamental suspect terranes. The definite age of the ophiolite is not well-established, with various authors having different claims. Encarnacion et al. (1993) conducted a U-Pb age dating for the Angat wherein the Angat Ophiolite was found to have an Early Middle Eocene age (48 Ma), close to the ZOC age - leading to the assumption that the two ophiolites are related and underlie most of Central Luzon. Hence, this paper aims to collect samples from the Eocene and Cretaceous Angat Ophiolite for petrographic and geochemical analyses, identify the relationship between the separated basalt units from the basalts in the main ophiolite body, and compare the geochemistry of the Eocene and Cretaceous units of the Angat Ophiolite with the other well-known ophiolites from the literature. Field investigations were conducted in five important localities wherein 15 samples were obtained. The results highlighted that the major mineral phases in the samples collected are plagioclase and augite, with some samples having hornblende and olivine. All samples appear to have undergone low-grade greenschist facies metamorphism, which may be attributed to hydrothermal alteration. Chloritization of pyroxene minerals is also evident, along with the hydrothermal alteration products of plagioclase and pyroxenes. The relationship between the EAO, MOC, and separated basalt patch in Marilaque Highway is identified. The Coto Block of the Zambales Ophiolite and the Angat Ophiolite may be related and formed over a mantle initially enriched by a subduction component.

Green synthesis of rectangular hollow tubular carbon nitride via in-situ self-assembly strategy to enhance the degradation of tetracycline hydrochloride under visible light irradiation

It has been an urgent requirement for materials with remarkable performance in the photocatalytic degradation of organic contaminants by photocatalytic technology. Limited surface area and speedy recombination rate of photogenerated charge carriers seriously restrain the application of g-C3N4. Morphology control is a powerful approach to enhance the photocatalytic efficiency of g-C3N4. Herein, we reported a method to attain graphitic carbon nitride with rectangular hollow tubular morphology and asperous surface (TUM–CN–2) which is prepared from urea-melamine hydrothermal products and trithiocyanuric acid by self-assembling without using organic solvents or template agents. The specific surface area, photocatalytic activity, and photo-generated carriers migration and separation rate of the obtained photocatalyst TUM–CN–2 are vastly improved. Contrasted with pure g-C3N4, the degradation rate of tetracycline hydrochloride (TCH) and Rhodamine B (RhB) was enhanced about 3.04 and 13.96 times in visible light irradiation, respectively. Moreover, the interference parameters, active free radicals, potential degradation mechanism, and degradation paths of TCH were researched systematically. This work provides a green way to acquire the modified g-C3N4 with splendid catalytic activity through the self-assembly method.

Mineral phase evolution and heavy metals migration during the hydrothermal treatment of municipal solid waste incineration fly ash

The solidification of heavy metals in the municipal solid waste incineration fly ash was realized by the hydrothermal treatment with mineral additives added. The experimental results showed that the addition of SiO2 at 200 °C with the NaOH concentration was 0.5 mol/L attributed to the formation of fibrous tobermorite and effectively reduced the heavy metals toxicity of hydrothermal products, especially Pb and Cu. When SiO2 and Al2O3 were both introduced, the generated katoite and sodalite showed a better curing effect on Zn at lower NaOH concentrations. Further, the dynamic correlation between the tobermorite formation and heavy metals solidification was explored. It was found that the heavy metals in fly ash were first dissolved into the alkaline liquid phase and then transferred into the solid phase as the treatment proceed. The solidification of Pb which finished before 8 h was mainly due to the encapsulation of the tobermorite precursor before crystallization, while that of Cu which lasted over 48 h mainly relied on the adsorption and cation exchange effect caused by the formed tobermorite. Therefore, selecting the appropriate mineral addition scheme and hydrothermal time according to the fly ash components and heavy metals categories can effectively improve the curing cost performance.

Methods for enhancing the properties of products from food waste via hydrothermal carbonation (HTC): Gradient-enzymatic-pretreatment-nitrogen-migration-strategy

Gradient enzymatic pretreatment is an effective method for improving the quality of hydrothermal carbonation products from food waste. Food waste mainly contains polysaccharides, proteins, fats, and indigestible fibers. In this study, food waste model compounds formulated according to the survey were subjected to enzyme-assisted hydrothermal carbonation. Results showed that the high heating value of the hydrochar reached 31.62 MJ/kg at 240 °C for 25 min when the meat content of the raw material was high. Increases in reaction temperature and residence time remarkably changed the species of compounds in the aqueous phase. The increase in the amount of the key nitrogen-containing components doping in the aqueous phase after enzyme-assisted hydrothermal carbonation was the major factor that enhanced its luminescence intensity. The concentration of total nitrogen in the aqueous phase reached 1403.31 mg/L at 220 °C for 25 min. The gradient enzymatic pretreatment method combined with hydrothermal carbonation process facilitates the nitrogen migration of food waste in the aqueous phase, thus ensuring sustainable production and enhancing the product properties of food waste for high-valued applications.

Geothermal carbonate reservoirs and their sustainability: what can natural hydrothermal systems tell us?

Minerals that make up carbonate rocks (i.e. calcite) have very high chemical reactivity, allowing for various types of porosity-altering deformation processes such as dissolution and recrystallization (e.g. dolomitization, silicification), that produce secondary porosity. Even though water enriched with CO2 may quickly equilibrate by dissolving calcite, carbonate is also very dynamic, and cemented veins may still act as planes of weakness compared to the host rock allowing fluids to open up and then seal these fractures again. Therefore, natural carbonate rocks often show not only the numerous deformation stages overprinting one another, but also the same veins opening up again and again forming crack-seal structures.Natural fossil hydrothermal systems were investigated within outcrops at Nowa Wioska, Czatkowice, Pomorzan, Trzebionka, Orzel Bialy mines, Dziura cave and Hucianski Klin crest in the south of Poland to evaluate the influence of hydrothermal activities on the rock pore evolution. We present in more detail the Triassic carbonate sequence near Nowa Wioska village in the Silesian-Kraków region, where hydrothermal water had been flowing through an open fault zone, forming various hydrothermal products: secondary intercrystalline pores, vugs, breccias, metal ore and mineral precipitates. The impact of these products on the permeability of the geothermal system was analyzed in comparison with the adjacent host rock unaffected by tectonic and hydrothermal processes. We observed that at least three successive episodes of fracturing occurred during the Tertiary demonstrating that fluids were introduced episodically in the Triassic rocks. Fracture- and vug-filling calcite, saddle dolomite, pyrite, sphalerite, galena, quartz and clays were preferentially observed on the downthrown side of the fault that underwent a more intense tectonic deformation that had a decisive influence on the migration of mineralizing hydrothermal solutions. Even though mineral and metal-ore precipitates, sediments and solution / collapse breccias fill most of these karsts and fractures, the porosity and permeability of the hydrothermally altered rocks remain quite high compared to the host rock. Moreover, secondary dissolution forming vugs increase this porosity and permeability even further. The studied examples suggest that once geothermal system has been active, it stays as a preferential zone for the following deformation events, making it sustainable for tens of thousands or even millions of years.

Membrane distillation for algal supernatant reuse from hydrothermal carbonization aqueous product

ABSTRACT With growing demand for more sustainable dairy manure management methods, a system involving hydrothermal carbonization (HTC), membrane distillation (MD), and algae cultivation for resource recovery from dairy manure was partially investigated in this study. Two algal species, Arthrospira maxima and Chlamydomonas reinhardtii, were cultivated on the hydrothermal aqueous product (HAP) of dairy manure, but the former requires a carbonate buffer for successful cultivation. The spent HAP after algae cultivation was treated using MD where the operational efficacy and distillate quality were assessed. Comparing the MD performance of the buffered HAP to the unbuffered HAP revealed the addition of the buffer decreased water flux and distillate quality, but cultivation with A. maxima reversed these effects and produced distillates with reduced COD, TN, and NH3 concentrations. C. reinhardtii cultivation resulted in increased distillate COD and NH3 concentrations compared to the unbuffered HAP. Fluorescence was used to broadly characterize the organic components of the feed and distillate streams. Regrowth experiments with A. maxima revealed the spent buffer can successfully be recycled, but fresh nutrients are required.

Characterization of Metapelite and Metasiltstone as Uranium-REE hosted rocks in Rirang Area, West Kalimantan

The Rirang River, Kalan, West Kalimantan has U and REE resources in the form of mineralization found at the intercalation of metapelite and metasiltstone. However, there are only a few studies about the characterization of U and REE-bearing host rocks in Indonesia. Determining the geological influence of the metasedimentary rock on the mineralization of U and REE is crucial. Thus, the characterization of metapelite and metasiltstone has been substantiated in this study to reveal the potency of the host rock in hosting the U and REE. Petrographic, micro-XRF, and AMICS methods were used to conduct mineralogical analysis. These two rocks share a mineral composition that includes clay minerals, hydrothermal alteration products, and several minerals that indicate metamorphism processes. The foliation structure with a spotted shale texture further indicates the metamorphism process in metapelite and metasiltstone. REE and trace elements associated with U are constituents of clay minerals such as wonesite, staurolite, montmorillonite, chlorite, illite, and kaolinite. The geochemical properties of metapelite and metasiltstone suggest that REE mineralization and trace elements associated with U come from hydrothermal alteration processes.

Valorization of fly ash as zeolite by hydrothermal process for dyes adsorption

Valorization of fly ash as zeolite is one of sustainable ways to reduce environmental burden. In this paper, zeolite was prepared from fly ash by hydrothermal process and applied as dyes adsorbent. In hydrothermal process, fly ash was reacted with 5 N NaOH solution using solid/liquid ratio of 1/30 for 15 hours at temperature of 85°C. Characterization of hydrothermal products consisted of X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, and scanning electron microscope (SEM) analysis. The results indicated the formation of Na-X zeolite with higher surface area compared to raw fly ash. The obtained zeolite was applied as Eriochrome Black-T (EBT) dye adsorbent. Adsorption was conducted in batch process with variations in time and dye initial concentration. The adsorption efficiency would increase with increasing time, but after 90 minutes the adsorption efficiency would be relatively constant. The higher the dye initial concentration, the lower the adsorption efficiency. Furthermore, the study of adsorption kinetics model and adsorption isotherm model that had been carried out showed that adsorption process of EBT dye by zeolite from fly ash tended to follow pseudo-second order kinetics model and Freundlich isotherm model.