Leaching Fraction Research Articles

High residual sodium carbonate water in the Indian subcontinent: concerns, challenges and remediation

Water scarcity has become one of the major limiting factors in global agriculture, particularly in the arid and semi-arid regions of the world. This necessitates irrigation with marginal-quality waters including those with high levels of residual sodium carbonate (RSC) and an important water quality parameter. Extended use of high RSC water leads to accumulate sodium in the soil which alters physical and chemical properties of soils. The electrical conductivity is a good index of salinity while sodium adsorption ratio (SAR) that of sodicity hazard of irrigation water. It has been found that waters with high RSC values are more hazardous compared to no RSC water of equal SAR. Sustainable agriculture on these soils demands to adopt certain site-specific management strategies prior to use such low-quality waters for the economic production of crops. Strategies like dilution with low salt water and addition of calcium-based amendments, along with organic manures have been traditionally practiced and giving some promising results. It is well documented that for improving plant growth, irrigation to achieve low leaching fraction is necessary for the purpose of reducing the transport of solutes that are responsible for the degradation of water quality and provides an efficient use of limited water supplies. In addition, implementations of government policies and public–private sector collaborations are necessary to find new horizons for the management of high RSC irrigation waters in arid and semi-arid regions of the world. This article provides an overview of soil permeability problems associated with the irrigation using high RSC waters.

Chalcopyrite Leaching in a Dimethyl Sulfoxide Solution Containing Copper Chloride

Chalcopyrite (CuFeS2) is the most refractory copper mineral when treated in conventional sulfate media leaching systems. This is the first study to examine the use of a dimethyl sulfoxide (CH3SOCH3, DMSO) solution containing copper chloride (CuCl2) for the leaching of chalcopyrite. Leaching experiments for a copper concentrate composed mainly of chalcopyrite were conducted at ambient pressure at 313–413 K. The leaching fractions of Cu, Fe, S, Au, and As were investigated. It was found that 90% of the Cu was extracted in 2 h, and 94% was extracted in 4 h at 373 K, which is competitive with other conventional processes. A DMSO solution containing CuCl2 could selectively dissolve the valuable metals Cu and Au from chalcopyrite, but leave minerals with little economic value such as pyrite (FeS2) and As in the residue. Chalcopyrite is oxidized by cupric ion in proportion to the stoichiometric ratio of Cu in the concentrate to the initial cupric ion in the DMSO solution, which is enhanced by the presence of oxygen below 373 K.

The materials flow and membrane filtration performance in treating the organic fraction of municipal solid waste leachate by a high solid type of submerged anaerobic membrane bioreactor

The anaerobic digestion of leachate from organic fraction of municipal solid waste (OFMSW) is a long-standing challenge. A submerged anaerobic membrane bioreactor (AnMBR) embedding three flat sheet membrane was therefore continuously operated for 63 days to investigate the materials flow and membrane performance. The results obtained show that approximately 90% COD was removed and 86% was converted into methane under an OLR of 5.6 kgCOD/m3·d corresponding to a HRT of 10 days. Under the high solid condition (34.5–61.1 g/L total solids in AnMBR) and flux of 5 and 6 LMH, the membranes was operated practically at constant trans-membrane pressure (TMP). When the membrane was operated at a high flux of 7 LMH the TMP rapid increase occurred in 22 h resulting in a non-recoverable permeability. A sustainable flux was thus identified. This study demonstrated the feasibility of AnMBR treating OFMSW leachate under high solid condition with high flux.

Stable Strontium Isotopic Compositions of River Water, Groundwater and Sediments From the Ganges–Brahmaputra–Meghna River System in Bangladesh

The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to the global oceanic Sr inventory. The stable strontium isotope ratios (δ88Sr) provide a new tool to identify chemical weathering reactions in terrestrial water. In this study, we investigated the spatiotemporal variations of δ88Sr in samples of river water, bedload sediment, and groundwater collected from the Ganges–Brahmaputra–Meghna drainage basin in Bangladesh, which is known to strongly influence the 87Sr/86Sr ratio in seawater. The average δ88Sr values of waters of the Ganges, Brahmaputra, and Meghna rivers were 0.269, 0.316, and 0.278‰, respectively. Our data showed little difference between seasons of high and low discharge. The δ88Sr values measured in sequential leaching fractions of sediments varied from –0.258 to 0.516‰ and were highest in the silicate fraction, followed in turn by the carbonate fraction and the exchangeable fraction. Both 87Sr/86Sr and δ88Sr of these waters are primarily controlled by the inputs of Sr in weathering products from the Bengal Plain and Sr from the Himalayan rivers (Ganges and Brahmaputra). Values of δ88Sr and Sr/Ca were higher in the Brahmaputra River than in the Ganges River, a difference we attribute to greater input from silicate weathering. The variations of δ88Sr and 87Sr/86Sr were greater in groundwater than in river waters. Mineral sorting effects and dissolution kinetics can account for the large scatter in 87Sr/86Sr and δ88Sr values. The depth profile of δ88Sr showed wide variation at shallow depths and convergence to a narrow range of about 0.31‰ at depths greater than 70 m, which reflects more complete equilibration of chemical interactions between groundwater and ambient sediments owing to the longer residence time of deeper groundwater. We found that δ88Sr values in the groundwater of Bangladesh were almost identical to those of river water from the lower Meghna River downstream of its confluence with the Ganges–Brahmaputra river system, thus confirming that the δ88Sr composition of the groundwater discharge to the Bay of Bengal is very similar to that of the river discharge.

Mineral and Fermentative Profile of Forage Sorghum Irrigated with Brackish Water

ABSTRACT This study determined the mineral composition of sorghum Ponta Negra and its silage, irrigated with different leaching fractions with brackish water. Two experiments were performed: The first step evaluated the sorghum irrigated by four leaching fractions with brackish water (0, 5, 10 and 15%) and 4 repetitions. In the second experiment, sorghum was harvested at 101 days to make experimental silos which, according to the leaching fractions, four treatments were formed, with 5 repetitions each, totaling 20 silos stored for 90 days. A randomized block design was adopted. Different leaching fractions with brackish water provided a quadratic behavior was observed for Nitrogen (N), Phosphorus (P) and Sulfur (S) on the sorghum plant. A positive linear effect was observed for Potassium (K), Calcium (Ca), Magnesium (Mg) and Sodium (Na) with the increase in leaching fractions with brackish water in the irrigation of sorghum plant. Regarding sorghum silage, the leaching fractions with brackish water promoted a positive linear effect for the N content and quadratic effect for P, K, Ca, Mg and Na. Despite the high content of soluble salts in the water resources available in arid and semi-arid regions, the use of irrigation leaching fraction has been considered a viable alternative for the production of tolerant forage crops.

REE fractionation and quantification of sediment source in the Yellow Sea mud deposits, Εast Αsian marginal sea

Discriminating sediment sources quantitatively of several unique shelf-mud deposits in the Yellow Sea has received considerable attention, because they are active sedimentary depocenters that can elucidate the river sediment dispersal patterns and the depositional systems of the sea. Here, we propose a new sediment source proxy model of rare earth elements (REEs) that reflects innate characteristics of their fractionation distribution patterns and provides a reasonable and practical estimation for quantifying sediment source apportionments in the Yellow Sea. REEs of riverine and shelf-mud sediments were granulometrically and chemically partitioned, and the unique characteristics of their fractionation patterns were recorded and numerically indexed. We found distinct differences in the REE fractionation pattern index of riverine sediments, possibly due to the different source rock compositions. Notably, the acid-leached phase of the clay fraction may be a better material for quantitative evaluation of river contributions in the Yellow Sea. Using the REE-source index model presented here, proportional contributions of Chinese river sediments to the central and southeastern Yellow Sea mud deposits were estimated to be 55–80% and 10–40%, respectively, with higher percentage in the leached fraction. Our results elucidate the disagreement between mud budget and river discharge, particularly in Korean coastal mud deposits, as well as the source interpretation of the Yellow Sea shelf-mud deposits, which have been debated since the 1980s.

Assessment the leaching characteristics and long-term leaching behavior of some radionuclides from synthesized zeolite cement matrix

The development of cementitious materials remains a vital goal to produce valuable products with good mechanical, physical and chemical properties suitable for the safe disposal of concentrated radionuclides resulted from the treatment of contaminated solutions. In this paper, zeolite cement with good properties was laboratory synthesized from industrial by-products fly ash and characterized using various characterization techniques. The leaching characteristics of strontium and cobalt radionuclides from the synthesized zeolite cement were scrutinized conforming with the standard leaching methodology of International Atomic Energy Authority (IAEA). A mechanical strength assessment was executed to characterize the extent of immobilization process of the solidified matrices. The cumulative leaching fraction (ɤ) of the two studied radionuclides was found to be less than 5% in all examined conditions, which implies the applicability of the IAEA-recommended methodology for estimating the diffusion coefficient. The experimental leaching data were regressed nonlinearly to various mathematical kinetic models to assess the controlling leaching mechanism and to determine the leaching parameters. The regression results indicated that strontium (85Sr) and cobalt (60Co) leaching resulted from two succeeding mechanisms: as first order kinetic reaction, and then diffusion. The calculated values of leachability indices signify that the performance of each of the studied matrices is within an acceptable range. A simplified mathematical model, rooted in the first order reaction and diffusion mechanisms, was simulated to predict the radionuclides leaching rates from zeolite cement matrices. By comparing the synthesized zeolite cement with other cementitious materials, it can be concluded that the synthesized material can be classified as an efficient material suitable to immobilize 85Sr and 60Co from radioactive wastes. The acquired findings demonstrated that the studied immobilized waste matrices have acceptable mechanical effectiveness.

Performance of Two Seashore Paspalum (Paspalum vaginatum Sw.) Varieties Growing in Shallow Green Roof Substrate Depths and Irrigated with Seawater

The continuing decline in global drinking water reserves necessitates finding alternative water sources for turfgrass irrigation, especially in southern semi-arid Mediterranean countries. The aim of the present study was to evaluate the potential of using seawater for irrigating two varieties of seashore paspalum (Paspalum vaginatum Sw.), “Marina” and “Platinum ΤΕ”, growing in shallow green roof substrates, and to determine their recuperative capacity after the termination of the salt stress period. The greenhouse study comprised of 48 lysimeters equipped with extensive green roof layering. Treatments included: (i) two substrate depths (7.5 cm or 15 cm) and (ii) three seawater irrigation regimes (7 mm, 15 mm, or 45 mm every two days). Measurements included the determination of green turf cover (GTC) as well as the leaching fraction (LF) and leachate electrical conductivity (ECL) draining from the lysimeters. It was found that during the 46-d salt stress period, none of the seawater irrigation regimes managed to maintain acceptable GTC levels for both seashore paspalum varieties. Increasing the green roof substrate depth from 7.5 cm to 15 cm resulted in GTC improvement. During the recovery period, the use of potable water as irrigation source improved GTC levels. After 40 d the recovery was complete since GTC exceeded 90% in all treatments for both varieties. Regression curves correlating GTC response to ECL can be used to estimate the leaching requirements of turfgrasses grown in shallow green roof systems when irrigated with saline water.

Highly efficient sorption and immobilization of gaseous arsenic from flue gas on MnO2/attapulgite composite with low secondary leaching risks

Some sorbents have been developed for arsenic (As) compounds capture from flue gas . However, most of the conventional sorbents have cost constraints and can cause secondary pollution due to the leaching of arsenic after use. To solve this problem, a new and highly efficient adsorbent for gaseous arsenic was successfully developed in this paper with excellent immobilization performance and low-cost. A series of Mn-supported attapulgite (ATP) composites were fabricated, characterized, and investigated for arsenic capture. The modification of ATP with Mn not only considerably enhanced the adsorption efficiency but also stabilized the adsorbed As in the spent sorbents. SO 2 in flue gas promoted the adsorption performance through As-sulfate binding, whereas NO was beneficial for the oxidation of As(III) to As(V) on the surface of Mn-modified ATP. The incorporation of Mn with ATP generated abundant hydroxylate (OH − ) from hydration and accelerated the formation of As-sulfate compounds, which was beneficial for physical encapsulation . The results of the toxicity characteristic leaching procedure and sequential extraction test revealed that adsorbed As could be considerably immobilized by the sorbent with low leaching ability. Mn modification changed more As into inert fractions and consequently inhibited release from spent sorbents, which considerably reduced the risks of secondary pollution. The developed composite can be potentially used as a new efficient sorbent for gaseous arsenic capture in flue gas. • Manganese modification effectively enhanced the capacity of ATP for gaseous arsenic removal in flue gas. • Trivalent arsenic was oxidized into pentavalent arsenic during the process. • Manganese oxides facilitated the transformation of adsorbed-arsenic on Mn-ATP from leachable fraction to inert fraction.

UV/H2O2-assisted forward osmosis system for extended filtration, alleviated fouling, and low-strength landfill leachate concentrate

The forward osmosis (FO) membrane process is a good option for treating complex wastewater, such as landfill leachate, owing to its high rejection. However, organic membrane fouling and the generation of high-strength concentrate hamper efficient and environmentally friendly operation. To overcome these limitations, an integrated FO system combined with UV/H2O2 oxidation is proposed in this paper. Changes in the heterogeneous organic composition of the leachate were tracked along the treatment processes via size exclusion chromatography and excitation emission matrix combined with parallel factor analysis, which allowed us to pinpoint the organic fractions responsible for FO membrane fouling and evaluate their removal efficiency. Three fluorescent components, including tryptophan-like (C1), fulvic-like (C2), and humic-like (C3) components, were identified in the landfill leachate. A separate UV/H2O2 oxidation system led to selective removal of the organic leachate fractions, causing membrane fouling by ~80% along with the overall removal of bulk leachate by ~45%. Compared to traditional FO, the integrated system resulted in improved filtered volume (by 40%), decreased overall membrane resistance (by 30%), complete flux recovery after physical cleaning, and 50% reduction of organic carbon in the membrane concentrate. Moreover, the concentrate from the integrated FO system was characterized by a much lower abundance of large molecules, which is beneficial for the reclamation of concentrate due to its high biodegradability. This study demonstrated the effectiveness of UV/H2O2 oxidation as an integrated option for an FO system used for extended filtration, membrane fouling mitigation, and the production of low-strength landfill leachate concentrate.

Leaching Fraction-based Microirrigation Schedule Reduced Water Use but Not N and P Loss during Production of a Container-grown Shrub

Irrigation that decreases the leaching fraction (LF; leachate/water applied) has been shown to reduce fertilizer N and P leaching during the production of sprinkler-irrigated, container-grown plants; however, little research involving outdoor production of microirrigated plants in large containers has been conducted. Two microirrigation schedules based on routine leaching fraction testing were compared to determine their effects on water use and leaching losses of N and P during the production of Dwarf Burford holly in 36-cm-diameter (trade #7) containers. Applied irrigation water and leachate were collected continuously and sampled weekly during the 12-month experiment. An irrigation schedule adjusted once every 1 to 3 weeks to a target LF of 20% resulted in the application of 36% less water (383 vs. 597 L/plant) and 43% less leachate (255 vs. 445 L/plant) than a schedule adjusted to a target LF of 40%; plant growth was unaffected (P > 0.05). Irrigation schedules had no effect (P > 0.05) on cumulative N and P leaching losses, which were attributed in large part to rain. Average leaching losses of N and P were 15.2 and 2.2 g per container (210 and 30 kg·ha−1·year−1), respectively. Both N and P leaching losses represented 35% of the 43.5 g N and 6.3 g P applied per container in two controlled-release fertilizer applications. The results support the best management practice of scheduling irrigation based on routine LF testing to reduce irrigation water use but not reduce N and P leaching.

Effects of fine fractions of soil organic, semi-organic, and inorganic amendments on the mitigation of heavy metal(loid)s leaching and bioavailability in a post-mining area

This study investigated the effects of soil amendments including biomasses (rice husk, RRH and maple leaf, RML), biochar (rice husk biochar, RHB and maple leaf biochar, MLB), and industrial by-products (red mud, RM and steel slag, SS), at two application rates (0, 1, and 2% w/w) on leaching and bioavailability of heavy metal(loid)s (HMs) (As, Cd, Cu, Pb, and Zn) in the presence of an Asteraceae (i.e., lettuce). Physicochemical properties of the soil (i.e., pH, EC, CEC, and HMs leaching) and plants were examined before and after amending. The addition of amendments significantly (p < 0.05) increased soil EC (from 100 to 180 μScm−1) and CEC (from 7.6 to 15 meq100 g−1). Soil pH from 6.7 ± 0.05 increased about 2 units with increasing in the application rate of MLB, RM, and SS, while it decreased about 0.8 units in RML amended soil. Soil amendments reduced the easily leachable fractions (exchangeable and carbonate) of HMs in the order of MLB > SS > RM > RHB. The average concentration of Cd, Cu, Pb, and Zn in plant roots and shoots decreased >30 wt% in biochars and industrial by-products amended soils, while biomasses mitigated As uptake in lettuce. Results demonstrated that adding maple-derived biochar combined with revegetation effectively immobilized HMs in a post-mining area beside an induce in plant growth parameters.

Influence of freeze-thaw cycles and high temperature exposure on immobilization performance of geopolymer-zeolite A composites for strontium radionuclide

This work aims to explore the influence of freeze-thaw cycles and high temperature exposure on immobilization performance of geopolymer-zeolite A composites (GZAC) for strontium radionuclide. After 45 freeze-thaw cycles, no visible change in the phase composition, microscopic morphology and cumulative leaching fractions (CLF) of the Sr2+ ions could be observed. Although the zeolite phases in GZAC were completely destroyed at 800 °C, the CLF of Sr2+ ions from the GZAC still meet Chinese National Standard (GB14569.1-2011). At 1000 °C, the CLF of Sr2+ ions decrease distinctly, attributing to the further viscous sintering and obvious reduction in open porosity. Therefore, we could conclude that GZAC presents remarkable thermal stability for radioactive strontium immobilization.

The fate of heavy metals and salts during the wet treatment of municipal solid waste incineration bottom ash

Bottom ash contains unfavorable contaminants that could leach into the circulating water used for wet treatment, and its improper disposal of bottom ash could cause ecological pollution. This study was to discuss the partition of heavy metals and salts of bottom ash into circulating water and ash stockpile runoff in wet treatment plants in southern China. The leachability of bottom ash before and after the wet treatment was also investigated. The checked heavy metals Pb, Cu, and Ni and dissolved salts Cl− and SO42− show lower available fractions in leachate from the treated bottom ash than that in raw bottom ash. Circulating water is contaminated by target heavy metals, which the contents of Cu and Pb is higher than its limit for urban wastewater discharge. The circulating water owned the highest concentration of Cl− and SO42−, above10000 mg/L, and 1100 mg/L, which is far higher than the limits. The detected heavy metals, Cl− and SO42− in runoff also exceed the limits for urban wastewater discharge. Locations for bottom ash processing and storage sites should be selected to control and prevent any leaching and runoff impacts. Any runoff and circulation water should be discharged to the lined landfill’s leachate collection system or suitable industrial wastewater treatment facilities.

Leaching of dissolved organic carbon from mineral soils plays a significant role in the terrestrial carbon balance.

The leaching of dissolved organic carbon (DOC) from soils to the river network is an overlooked component of the terrestrial soil C budget. Measurements of DOC concentrations in soil, runoff and drainage are scarce and their spatial distribution highly skewed towards industrialized countries. The contribution of terrestrial DOC leaching to the global‐scale C balance of terrestrial ecosystems thus remains poorly constrained. Here, using a process based, integrative, modelling approach to upscale from existing observations, we estimate a global terrestrial DOC leaching flux of 0.28 ± 0.07 Gt C year−1 which is conservative, as it only includes the contribution of mineral soils. Our results suggest that globally about 15% of the terrestrial Net Ecosystem Productivity (NEP, calculated as the difference between Net Primary Production and soil respiration) is exported to aquatic systems as leached DOC. In the tropical rainforest, the leached fraction of terrestrial NEP even reaches 22%. Furthermore, we simulated spatial‐temporal trends in DOC leaching from soil to the river networks from 1860 to 2010. We estimated a global increase in terrestrial DOC inputs to river network of 35 Tg C year−1 (14%) from 1860 to 2010. Despite their low global contribution to the DOC leaching flux, boreal regions have the highest relative increase (28%) while tropics have the lowest relative increase (9%) over the historical period (1860s compared to 2000s). The results from our observationally constrained model approach demonstrate that DOC leaching is a significant flux in the terrestrial C budget at regional and global scales.

Low leaching characteristics and encapsulation mechanism of Cs+ and Sr2+ from SAC matrix with radioactive IER

Radioactive ion exchange resin is a problematic waste requiring proper immobilization to ensure that the resin's radioactive ions are stable for storage and ultimate disposal in water environments, such as seawater or groundwater. Sulphoaluminate cement hardened paste, with the dense structure, great retention capacity for ions, and resistance to SO42− and Cl−, is a potential cementation material to encapsulate 137Cs+ and 90Sr2+ in radioactive ion exchange resin. The leaching rates of Cs+ and Sr2+ from the sulfoaluminate cement matrix solidifying radioactive ion exchange resin and their immobilization characteristics of the predominant hydration products (ettringite; aluminum hydroxide gel) of sulfoaluminate cement were investigated in depth. The experimental results showed that the sulphoaluminate cement radwaste matrix had a better retention capacity for Cs+ and Sr2+ than the OPC radwaste matrix. The 42 days cumulative leaching fractions of Cs+ and Sr2+ were 6.21 × 10−2 and 5.77 × 10−3 cm, respectively, which could be described by the FRDM or DDIM model for Cs+, and the DDIM model for Sr2+. The retention of Cs+ and Sr2+ originated from the chemical absorption by ettringite, aluminum hydroxide gel, and the physical barrier. The ettringite and aluminum hydroxide gel's retention rates for Cs+ are above 70% and 40%, respectively, while those of Sr2+ are above 88% and 10%, respectively. In detail, Cs+ and Sr2+ could be absorbed by both ettringite and aluminum hydroxide gel. Unlike Cs+, Sr2+ could enter the ettringite's crystal lattice by replacing Ca2+ and entering the negative channel.

Air-drying of soil samples – A crucial step in the determination of leachable concentrations of per- and polyfluoroalkyl substances

Batch leaching tests at a liquid to solid ratio of 2 L/kg are a valuable tool for the assessment of low PFAS levels in soils. Data from different monitoring programs comprising samples without known local source of PFAS contamination showed that soil-sample drying at ambient temperature or at 40 °C prior to the leaching process leads to higher PFAS leachate levels compared to non-dried samples. The effect was greater for perfluoroalkyl carboxylic acids (PFCAs) than for perfluoroalkyl sulfonic acids (PFSAs). In a controlled field study comparing field-fresh (frozen to −18 °C and thawed) samples with air-dried (room temperature) samples median levels after drying increased to 140%–470% for C4 to C10 PFCAs and to 130%–200% for C4, C6, and C8 PFSAs, respectively. Thus, using field-fresh samples for batch leaching tests might underestimate the leachable fraction of PFAA in the field, where drying and leaching periods alternate.

Characterization of bioavailable Sr isotopic composition of Jeju Island, Korea

Stable isotope signatures of geologic, atmospheric, and hydrologic sources are transferred to the ecosystem through the food chain. The present study used Sr isotope data of soil and plant samples collected from Jeju Island to explore the roles of these sources in the local bioavailable Sr pool. X-ray diffraction and Sr isotope data revealed that the soil materials came from diverse sources such as weathered volcanic bedrock, marine carbonate sediments, and allochthonous aeolian dust. Dilute (1 M) ammonium nitrate- and acetic acid-leachates of the soil samples yielded 87Sr/86Sr ratios between 0.7047 and 0.7092, which were slightly but discernably higher than ratios for Jeju volcanic rocks reported in the literature (0.7045 ± 0.0004). This indicates that relatively more radiogenic Sr, probably in carbonate and aeolian dust, was preferentially released to the leachates. Geopedological control over the bioavailable Sr pool was demonstrated by the positive 87Sr/86Sr correlation between leachable soil fractions and the corresponding plant samples. The enhanced 87Sr/86Sr ratios of plants (0.7062–0.7092, average = 0.7077 ± 0.0012) reflect the influence of seawater. These Sr isotope data provide a scientific basis for addressing archaeological and historical questions related to Jeju Island.

Mineralogy and BCR sequential leaching of ion-adsorption type REE: A novelty study at Johor, Malaysia

Since year 2010, advance research in resource investigation, mineralogy and geochemistry, environmental impact as well as processing technique of ion-adsorption type rare earth elements (REE) deposit particularly in mining industry has been conducted worldwide. Ion-adsorption type REEs are formed by weathering process of igneous rocks (typically granites) that contain certain REE-bearing minerals. Effect of the rapidly weathering, REE minerals are decomposed, and ionized REEs are absorbed on clay minerals such as kaolinite and halloysite. A research study has been made in discovery the ion-adsorption type REE prospecting in Johor, Southern Peninsular Malaysia with three vertical weathering profiles (up to 11 m) sampled on Besar island, Tengah island and Hujung island. Parent granite is A-type consist of quartz, K-feldspar, plagioclase, biotite and 0.6–1.4 wt% accessory minerals (zircon, apatite, monazite-(Ce) and chlorite). The main REE-bearing minerals are monazite-(Ce), apatite, zircon, titanite, allanite-(Ce) and bastnaesite-(Ce). Total REE concentrations in raw saprolite (potential REE horizon in weathering profiles) is ranging between 1167 and 2339 ppm. The laboratory leach ability of the REE in different parts of the A-type granite weathering profiles was determined by carrying out a three step BCR sequential extraction procedures. The evidence from the three-step BCR-701 (certified freshwater sediment standard) sequential extraction procedure for ion-adsorption was consistent with a near instant process (≤1 h) with 70–80% recovery rate. This is due to the re-precipitation of REE3+ ions in solution and due to hydrolysis of ions on the clay surface. The ion-adsorption (leached) fraction was enriched in light rare earth elements (LREE) compared with the raw sample compositions of the saprolites and saprocks (Ce/Ce* ratio range largely from 0.17 to 0.82). The LREE accounted for 80–90% of the total REE content in the investigated saprolite and saprock; allowed in agreement with the trend that was observed in Thailand and South China ores.

Kinetics and Mechanism of Leaching Potassium from Biotite in H2SO4 Solution

AbstractBiotite is a potential potassium mineral resource and the dissolution of biotite in H2SO4 solution is a green chemistry approach for recovering potassium. To estimate the efficiency of leaching process and to understand the behavior of leaching reactors, the kinetics and mechanism of leaching potassium from biotite in H2SO4 solution were studied in this work. The leaching experiments show that leached fractions of K2O increase with the increasing of temperatures and H2SO4 concentrations, and yet with the decreasing of biotite particle sizes. According to the shrinking core model, the leached fractions of K2O were fitted better by diffusion through product layer. A kinetics expression of diffusion‐controlled model on three parameters was acquired and it is appropriate to predict the leached fractions of K2O from biotite in H2SO4 solution. The dissolution of biotite in H2SO4 solution was interpreted by electrochemical mechanism coupling with characterization of the acid‐leached residues. This research results can aid in the design of leaching process for recovering potassium sustainably from biotite.