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The paper assesses batch system microcrystalline cellulose (MCC) adsorptive ability for copper and iron uptake from aquatic environment. Field emission scanning electron microscope (FESEM), point zero charge and Fourier transform infrared (FTIR) spectroscopy were used to examine the physicochemical and morphological features of MCC. The batch system of the sequestration progression for the elimination of Cu(II) and Fe(II) was used by varying the solution pH, MCC doses, initial copper and iron concentration, and resident time. The maximum removal percentage for Cu(II) and Fe(II) were 99.5% and 96.4%, respectively, at pH 7. The influence of MCC dosage showed the 1.0 g/L of adsorbents results the highest percentage of Cu(II) (99.8%) and Fe(II) (88.63%) correspondingly. Equilibrium data for both metals were well fitted with both Langmuir and Freundlich isotherms, representing monolayer and multilayer adsorption systems. The maximum sorption capacity of MCC was 534.61 mg/g and 845.75 mg/g, respectively, for Cu(II) and Fe(II) ions at room temperature. Pseudo-second-order model best describes the copper and iron kinetic data, signifying the dominance of chemisorption adsorption relation between the negatively charged MCC and adsorbates. After four successive regeneration cycles, the MCC polymer maintained its maximal adsorption capacity, demonstrating effective copper and iron ion separation from aqueous solution. According to the study's findings, poisonous heavy metals can be successfully removed from aquatic environments using eco-friendly microcrystalline cellulose. [ABSTRACT FROM AUTHOR]

Context: Given the diverse pathophysiological mechanisms underlying Alzheimer's disease, it is improbable that a single targeted drug will prove successful as a therapeutic strategy. Therefore, exploring various hypotheses in drug design is imperative. The sequestration of Fe(II) and Zn(II) cations stands out as a crucial mechanism based on the mitigation of reactive oxygen species. Moreover, inhibiting acetylcholinesterase represents a pivotal strategy to enhance acetylcholine levels in the synaptic cleft. This research aims to investigate the analogs of Huperzine A, documented in scientific literature, considering of these two hypotheses. Consequently, the speciation chemistry of these structures with Fe(II) and Zn(II) was scrutinized using quantum chemistry calculations, molecular docking simulations, and theoretical predictions of pharmacokinetics properties. From the pharmacokinetic properties, only two analogs, HupA-A1 and HupA-A2, exhibited a theoretical permeability across the blood-brain barrier; on the other hand, from a thermodynamic standpoint, the enantiomers of HupA-A2 showed negligible chelation values. The enantiomers with the most favorable interaction parameters were S′R′HupA-A1 (ΔGBIND = −40.0 kcal mol−1, fitness score = 35.5) and R′R′HupA-A1 (ΔGBIND = −35.5 kcal mol−1, fitness score = 22.61), being compared with HupA (ΔGBIND = −41.75 kcal mol−1, fitness score = 39.95). From this study, some prime candidates for promising drug were S′R′HupA-A1 and R′R′HupA-A1, primarily owing to their favorable thermodynamic chelating capability and potential anticholinesterase mechanism. Methods: Quantum chemistry calculations were carried out at B3LYP/6-31G(d) level, considering the IEF-PCM(UFF) implicit solvent model for water. The coordination compounds were assessed using the Gibbs free energy variation and hard and soft acid theory. Molecular docking calculations were conducted using the GOLD program, based on the crystal structure of the acetylcholinesterase protein (PDB code = 4EY5), where the ChemScore function was employed with the active site defined as the region within a 15-Å radius around the centroid coordinates (X = −9.557583, Y = −43.910473, Z = 31.466687). Pharmacokinetic properties were predicted using SwissADME, focusing on Lipinski's rule of five. [ABSTRACT FROM AUTHOR]

Methane release from marine sediments strongly influences the local seafloor environment and ecosystems, and may impact Earth's climate system. Recent studies revealed anomalous molybdenum (Mo) enrichment in seep sediments, which was linked to methane release events. Marine seep sediments are a potential sink of Mo for the global ocean, while the mechanisms leading to local Mo enrichment are not fully understood. The sediments from a gas hydrate-bearing area of the South China Sea analyzed herein reveal authigenic Mo (Mo auth) contents ranging from 0 and 31.4 µg/g and δ98Mo auth values ranging from 0.18 ‰ to 3.31 ‰. The range of δ98Mo auth values of seep sediments is therefore similar to values of modern iron-rich sediments with low concentrations of dissolved porewater hydrogen sulfide and sediments deposited under weakly euxinic sediments. Among the obtained South China Sea data, the more positive δ98Mo auth values (>ca. 1.5 ‰) are interpreted to reflect diffusion of seawater Mo into the sediment at moderate seepage rates and Mo isotope fractionation during the formation of thiomolybdates in the sulfidic seep environment. The lower δ98Mo auth values (

• Applied voltage and calcium addition increased biogas yield and CO 2 sequestration. • Wollastonite and CaCl 2 exhibited different CO 2 sequestration performances. • Wollastonite showed a better CO 2 sequestration effect with 2.22% CO 2 in biogas. • The contribution of chemical and biological CO 2 sequestration was clarified. The combination of microbial electrolytic cells and anaerobic digestion (MEC-AD) became an efficient method to improve CO 2 capture for waste sludge treatment. By adding CaCl 2 and wollastonite, the CO 2 sequestration effect with mineral carbonation under 0 V and 0.8 V was studied. The results showed that applied voltage could increase dissolved chemical oxygen demand (SCOD) degradation efficiency and biogas yield effectively. In addition, wollastonite and CaCl 2 exhibited different CO 2 sequestration performances due to different Ca2+ release characteristics. Wollastonite appeared to have a better CO 2 sequestration effect and provided a wide margin of pH change, but CaCl 2 released Ca2+ directly and decreased the pH of the MEC-AD system. The results showed methane yield reached 137.31 and 163.50 mL/g SCOD degraded and CO 2 content of biogas is only 12.40 % and 2.22 % under 0.8 V with CaCl 2 and wollastonite addition, respectively. Finally, the contribution of chemical CO 2 sequestration by mineral carbonation and biological CO 2 sequestration by hydrogenotrophic methanogenesis was clarified with CaCl 2 addition. The chemical and biological CO 2 sequestration percentages were 46.79 % and 53.21 % under 0.8 V, respectively. With the increased applied voltage, the contribution of chemical CO 2 sequestration rose accordingly. The findings in this study are of great significance for further comprehending the mechanism of calcium addition on CO 2 sequestration in the MEC-AD system and providing guidance for the later engineering application. [ABSTRACT FROM AUTHOR]

Steel slag is a kind of bulk alkaline industrial solid waste produced in the steelmaking process. Resource utilization of this solid waste is an urgent problem to be solved in the steel industry to achieve green and low-carbon development. Carbonation of steel slag is one of the key technologies for the utilization of steel slag and the reduction of CO2 emission. It is also an important means to realize the green and low-carbon development of the steel industry. However, the low leaching efficiency of steel slag limits its industrial application. In order to obtain the best leaching conditions, the leaching behavior of de-vanadiumized steel slag in ammonium chloride was studied in this paper. The leaching rate model of calcium ions based on the minimum free energy was established by thermodynamic theory, and the leaching effect of calcium ions in ammonium chloride solution was evaluated, which was mutually confirmed with the single-factor experiment. Then, the response surface method was used to further study the effects of various factors and their interactions on the leaching rate, and a second-order polynomial model of the leaching rate was established. The results showed that the significance of the parameters affecting the leaching rate of calcium ions was steel slag particle size > liquid–solid ratio > leaching temperature > leaching time. After leaching steel slag particles with a size of 0.089 mm for 69.85 minutes at a liquid–solid ratio of 89.74 and a temperature of 80 °C, the calcium ion leaching rate reached a maximum of 49.76 pct. Based on the experimental data of single factor and response surface, the Drozdov equation with self-resistance coefficient and Arrhenius equation were used to establish a kinetic model to explore the restrictive link of leaching rate. The apparent activation energy of the reaction was calculated to be 20.428 kJ/mol, indicating that the leaching process was controlled by the liquid–solid interface chemical reaction and diffusion mixing. The research results of this paper further improve the theoretical basis of steel slag leaching of calcium ions and obtain more scientific leaching parameters, which can provide technical guidance for the industrialization and large-scale efficient production of carbon dioxide fixed by de-vanadiumized steel slag. [ABSTRACT FROM AUTHOR]

To address the increasing levels of carbon dioxide (CO2) in the atmosphere, various heterocyclic N/B‐based intramolecular frustrated Lewis pairs (IFLPs) have been experimentally and theoretically investigated. Reports have shown them to be a potential catalyst for CO2 sequestration, however, a comparative rationale of these IFLPs has not been reported. Thus, in the present work, we have proposed an uninvestigated IFLP based on i. e., 2‐boranyl‐1,3,5‐triazine (BT) and compared with previously reported borylated imidazole (Im) and pyrimidine (Prm) for CO2 abduction. The density functional theory (DFT) base calculations have been carried out to probe the reaction mechanism and thorough natural bond orbital analysis has been carried out to get deeper insights into the catalytic behavior of the proposed IFLPs. Further, the effect of substituting the hydrogens at the ring and the B atom of the considered IFLP, by −CH3, −Cl and −OH, on the catalytic behavior has been studied. The results show that the borylated triazines can be a potential catalyst for CO2 sequestration. Also, the catalytic behavior of the presented IFLPs can be modulated by appropriated substitutions. [ABSTRACT FROM AUTHOR]

Rice provides ~20% of human dietary energy and, for many people, a similar share of their protein. Rice cultivation, however, produces significant greenhouse gas (GHG) emissions, comparable to those from the aviation sector. The main GHG from rice production is methane, mostly a result of conventional rice cultivation (CRC) keeping rice fields continuously flooded during the crop cycle. There is extensive evidence that alternate wetting and drying (AWD) of rice fields substantially reduces methane emissions. AWD is one component of the System of Rice Intensification (SRI), an agroecological approach to the management of plants, water, soil, and nutrients. This article reviews field studies measuring GHG emissions associated with the adoption of AWD and SRI. The review confirms that both AWD and SRI offer substantial reductions in methane emissions per hectare compared with CRC. These benefits are, however, partly offset by increases in emissions of nitrous oxide and carbon dioxide. The studies also show that SRI (but not AWD) improves yield and therefore further reduces GHG emissions per kg of rice. The review concludes that while both AWD and SRI substantially reduce emissions per hectare and per kilogram of rice, SRI can simultaneously contribute to food security while addressing the drivers of climate change. Further investigation of carbon emissions and sequestration under different rice cultivation methods is needed to strengthen the evidence base. [ABSTRACT FROM AUTHOR]

The development of natural hydrogen is an emerging topic in the current energy transition trend. The production process involves compositional multiphase flow via subsurface porous media. This makes studying the compositional phase equilibrium behavior essential for reliable reservoir simulation and prediction. Herein, we develop an iterative flash calculation scheme and a deep learning algorithm using a thermodynamics-informed neural network (TINN) to perform accurate, robust, and fast phase equilibrium calculations for realistic fluid mixtures of natural hydrogen. The application of TINN architecture can accelerate the calculations for nearly 20 times. The effect of capillarity on phase equilibrium states is demonstrated. Based on simulation results, suggestions for the natural hydrogen industry chain are provided to control the possible phase transitions under certain environmental conditions that may be observed in the natural hydrogen reservoirs, storage and transportation facilities. The extremely low critical temperature of hydrogen challenges the robustness of flash calculations but facilitates the separation of impurities by liquefying certain undesired species. Moreover, phase transitions under control can be an effective approach for carbon dioxide capture and sequestration with optimized operating conditions over the phase equilibrium analysis. [ABSTRACT FROM AUTHOR]

Adsorption capacity of activated biochar derived from Eichhornia crassipes was investigated for the sequestration of Cr (VI) from aqueous solution. Biochar was prepared and activated with different agents viz., 85% phosphoric acid, 0.5% sulphuric acid, 1 M ferric chloride and 10% polyethylenimine. Adsorption parameters were optimised by using Box–Behnken model of Response Surface Methodology (RSM), where the P value lesser than 0.05 and higher F value explained the significance of the model. Concentration and time showed positive effect while pH, biosorbent dosage and biosorbent size represented negative effect on adsorption. The optimum conditions for adsorption of Cr (VI) by activated biochar obtained from the model were pH: 2, biosorbent dosage was 1%, biosorbent size 1 mm, solute concentration of 985 mg/L and equilibrium time of 35 hours. An increase in concentration of solute molecules increased the adsorption of Cr (VI), whereas percent removal was reduced. Equilibrium relationship between sorbent and sorbate was determined using the isotherms Langmuir, Freundlich and Temkin models. Isotherm study was supported by Langmuir where sorption occurs on monolayer. The rate of adsorption and its mechanisms elucidated through kinetic studies. The higher correlation coefficient of 0.9985 reveals the significance of the studied models. Kinetics study fits well with the pseudo-second-order kinetics whereas isotherm study was best described by Langmuir model with maximum adsorption capacity of 50.0 mg g−1 under biochar activated with phosphoric acid (PA-WBC). Among the activation methods PA-WBC showed maximum chromium adsorption due to the influence of H+ ions present on the surfaces which highly favoured the sorption of anions. Hence, this activated biochar can be effectively utilised for the removal of Cr (VI) from industrial waste water, it was further suggested that water hyacinth has the additional advantage that it reduces or even eliminates the diverse impact of the weed on the environment. [ABSTRACT FROM AUTHOR]

Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism. Global observations from mangroves and saltmarshes unravel hidden carbon pathways. Inorganic carbon outwelling is revealed to dominate carbon budgets, impact coastal pH, and enhance the climate mitigation potential of blue carbon ecosystems. [ABSTRACT FROM AUTHOR]

Toluene and xylene are carcinogenic and toxic compounds, and their presence in excessive amounts in the environment has an adverse impact on water quality, thus affecting public health. In this study, magnetite coated oleic acid, (MNP-OA) nanocomposite was synthesized, characterized and applied as an effective nano-adsorbent for the efficient removal of toluene and xylene from aqueous solutions. Magnetite nanoparticles were coated with oleic acid via the microwave method and characterized using BET surface area, XPS, SEM-EDX and pHpzc analysis. Batch adsorption studies were performed to optimize operating parameters including solution pH, adsorbent dose, contact time, and initial concentration. The impact of hydrophobic coating on the kinetics, equilibrium, and the mechanism of toluene and xylene uptake were determined. Characterization confirmed the surface coating of magnetite with oleic acid which evidenced from the additional oxygenated functional groups such as hydroxyl and carboxylic groups. The morphological analysis showed spherically shaped magnetite nanoparticles. Maximum adsorption capacity of 133.57 mg/g for toluene and 161.01 mg/g for xylene were attained at solution pH of 8, adsorbent dose of 0.1 g and concentration of 100 mg/dm3 at 298 K. The pseudo-second-order and Langmuir models best explained the kinetics and adsorption isotherm, respectively. The thermodynamic parameters, including Gibbs free energy, enthalpy change, and entropy change of adsorption indicated that the adsorption process was endothermic and spontaneous in nature. The MNP-OA nanocomposites can be applied as a reusable, cost-effective, and efficient adsorbent for toluene and xylene remediation and could be considered for other volatile organic compounds in future application. [ABSTRACT FROM AUTHOR]

The present study reports low-cost novel biogenic magnetite Citrus limetta peels carbon (Fe3O4/CLPC) nanocomposites and modified Fe3O4/CLPC@CS nanocomposites cross-linked with glutaraldehyde and subsequently employed in batch mode sequestration of heavy metals ions. Diverse techniques fully characterized them, and the influence of operating variables on adsorption reactions from aqueous solutions was investigated. The Brunauer, Emmett, and Teller (BET) surface areas of synthesized Fe3O4/CLPC and Fe3O4/CLPC@CS NCs were 53.91 and 32.16 m2/g, while the mesoporous diameters were 7.69 and 7.57 nm, respectively. The Langmuir isotherm and Pseudo second order kinetic were well-fitting and capable of explaining the adsorption reaction. The Langmuir-based monolayer adsorption (qmax) for Fe3O4/CLPC@CS NCs was 82.65, 95.24, and 64.10 mg/g, higher than Fe3O4/CLPC NCs, which were 70.92, 84.75, and 59.17 mg/g for Ni (II), Pb (II), and Zn (II), respectively. Each metal's pseudo second order correlation coefficient (R2 ≥ 0.99) reveals that nanocomposites surface binding functional groups controlled the adsorption rate via chemisorption. Further, thermodynamic results confirm that each studied metal ions' adsorption was spontaneous, endothermic, and characterized by an increase in randomness. In addition to magnetic separability, three ad-desorption cycles yielded exceptional adsorption efficacy and > 93% regenerability. The present study also reveals the effective utilization of Fe3O4/CLPC and Fe3O4/CLPC@CS NCs as cost-effective magnetic separable green adsorbents for heavy metals sequestration from electroplating wastewater. [ABSTRACT FROM AUTHOR]

Ferrites count among the most functionally versatile magnetic materials in use in high technologies. In this study, synthesis, characterization and assessment of potential for use in water remediation of two different types of nanostructured ferrites were performed. Barium hexaferrite (BaFe12O19, BHF) and strontium hexaferrite (SrFe12O19, SHF) nanoparticle preparation using a flash-combustion method was successful. The prepared samples were thoroughly characterized for their microstructure, morphology, elemental composition, functional groups, surface charge density and magnetic, dielectric and optical properties. The hexagonal phase was detected as the primary one in X-ray diffraction patterns, while vibrational spectrophotometry analyses demonstrated the presence of an M-type hexagonal structure. Temperature-dependent ferromagnetic behavior of the nanoparticles was indicated from the χ-T curves, with a slightly higher single transition temperature, Tc, for BHF than for SFH: 675 °C vs. 650 °C. Despite having nanocrystalline structures, both BHF and SHF were identified as hard magnetic materials, with saturation magnetizations of 56.7 and 54.3 emu/g, respectively, and anisotropy fields greater than 9 kOe. Finally, batch adsorption studies were used to remove Pb(II) ions from aqueous solutions at various pHs and contact times using the as-prepared materials as fresh sorbents. The highest adsorption capacity was achieved at pH 7 and after 60 min of the contact time, equivalent to 84% and 80% for BHF and SHF, respectively. Extrinsic microstructural factors, such as particle morphology, surface area and porosity, proved to be more important for promoting the sequestration of Pb(II) than the intrinsic, crystallographic factors. Consequently, BHF performed better as an adsorbent than SHF under all of the tested conditions. The investigated nanostructured hexaferrites also demonstrated an exceptional recycling capacity. [ABSTRACT FROM AUTHOR]

The increasing CO2 concentration in the atmosphere has a severe influence on both the environment and human health, resulting in global warming. According to the high adsorption capacity for CO2 removal, zeolites play an important role for CO2 capture and sequestration. However, its powdery form limits their use in adsorption applications. When binding agents are used, the zeolite porosity is partially occluded that compromises the CO2 adsorption capacity severely. How to prepare binder‐free zeolite beads with a certain structure strength and how to keep the high surface area and porosity are a great challenge. In this work, LTA‐5A beads composites (80 wt.%) are prepared via cationic photopolymerization and then calcination is performed to remove organic part to obtain LTA‐5A beads with different sizes (<1.0 mm, 1.0–2.0 mm, and 2.0–3.0 mm). These beads (0.1 g) are characterized by good mechanical strength without any binder (partial bead fragmentation under 200 g‐load) with a preserved zeolite porosity. This method allows to exploit the zeolite beads reaching a high specific surface area (586 688 m2 g−1) and good CO2 adsorption capacity (4.5‐4.9 mmol g−1). These values are higher than those of commercial LTA‐5A beads (515 m2 g−1 and 3.8 mmol g−1, respectively), which is in agreement with their binder‐free structure. [ABSTRACT FROM AUTHOR]

Nickel (Ni) is a key component of the active site metallocofactors of numerous enzymes required for methanogenesis, including [NiFe]-hydrogenase, carbon monoxide dehydrogenase, and methyl CoM reductase, leading to a high demand for Ni among methanogens. However, methanogens often inhabit euxinic environments that favor the sequestration of nickel as metal-sulfide minerals, such as nickelian pyrite [(Ni, Fe)S2], that have low solubilities and that are not considered bioavailable. Recently, however, several different model methanogens (Methanosarcina barkeri, Methanococcus voltae, Methanococcus maripaludis) were shown to reductively dissolve pyrite (FeS2) and to utilize dissolution products to meet iron and sulfur biosynthetic demands. Here, using M. barkeri Fusaro, and laboratory-synthesized (Ni, Fe)S2 that was physically isolated from cells using dialysis membranes, we show that trace nickel (<20 nM) abiotically solubilized from the mineral can support methanogenesis and limited growth, roughly fivefold less than the minimum concentration known to support methanogenesis. Furthermore, when provided direct contact with (Ni, Fe)S2, M. barkeri promoted the reductive dissolution of (Ni, Fe)S2 and assimilated solubilized nickel, iron, and sulfur as its sole source of these elements. Cells that reductively dissolved (Ni, Fe)S2 bioaccumulated approximately fourfold more nickel than those grown with soluble nickel and sulfide but had similar metabolic coupling efficiencies. While the mechanism for Ni uptake in archaeal methanogens is not known, homologs of the bacterial Nik uptake system were shown to be ubiquitous across methanogen genomes. Collectively, these observations indicate that (Ni, Fe)S2 is bioavailable in anoxic environments and that methanogens can convert this mineral into nickel-, iron-, and sulfur-containing metalloenzymes to support methanogenesis and growth. [ABSTRACT FROM AUTHOR]

Heavy metals present in industrial effluents, when discharged into water channels, not only affect humans but also negatively impact plants and aquatic organisms. Sawdust is available readily in developing countries and can be used by small-scale industries for effluent water treatment containing low concentrations of bivalent zinc ions. This study explores the potential of sawdust-derived biosorbents, after boiling (SDB), chemical modification with formaldehyde (SDF), and sulfuric acid (SDS), for sequestration of Zn(II) from simulated wastewater as well as industrial effluents. The morphological analysis of the three biosorbents indicated a suitable porous structure with a pore size of 232.928 m2/g (SDB), 291.102 m2/g (SDF), and 498.873 m2/g (SDS). The functional analysis of native and metal-laden biosorbents indicated the role of − OH, − C = O, and − NH functional groups in Zn(II) binding. The process parameters were optimized and the spontaneous adsorption of Zn(II) was found to proceed by multilayer formation by following pseudo-second-order kinetics. SDS adsorbent (0.1 g) exhibited a greater potential for removal of Zn(II) from industrial effluents as compared to SDB and SDF at pH = 6.0 with the equilibrium adsorption capacity of 45.87 mg/g. Therefore, SDS could be a promising adsorbent for the treatment of wastewater in small-scale industries. [ABSTRACT FROM AUTHOR]

Mineral replacement reactions mediated by fluids are common in sedimentary basins, where they influence geochemical cycles. Phosphorous (P) pollution of soils, sediments and water bodies is currently a widespread problem. Some apatite accumulations in sediments may have formed through the interaction of P-bearing aqueous solutions with mineral surfaces that result in mineral replacement reactions. Here, we investigate the pseudomorphic replacement of anhydrite single crystals by aggregates of β-tricalcium phosphate and hydroxyapatite upon interaction with a P-bearing solution at temperatures between 120 and 200 °C. SEM imaging is used to study the texture of the aggregates. Rietveld refinement of the X-ray diffraction patterns and Raman spectra analysis of the reacted samples provide information on the kinetics of the replacement. At all temperatures β-tricalcium phosphate forms alongside hydroxyapatite at early stages of the replacement reaction. At T ≥ 180 °C, hydroxyapatite/β-tricalcium phosphate ratio rapidly increases, and hydroxyapatite is the only phase in fully replaced samples. At T < 180 °C hydroxyapatite/β-tricalcium phosphate ratio increases slowly and fully replaced samples still contain significant amounts of β-tricalcium phosphate. The progress of the replacement is facilitated by the formation of porosity. The evolution of the hydroxyapatite/β-tricalcium phosphate ratio and the crystal habit of both phases strongly influence the arrangement of this porosity. The empirical activation energy Ea (kJ/mol) of the replacement reaction is determined by the Avrami and the iso-conversion methods. Both approaches yield an Ea of ~40 kJ/mol. Anhydrite dissolution appears as the rate-limiting process and the overall kinetics of the replacement reaction is controlled by the rate diffusion of dissolved species through the porosity network. The ripening of the metastable β-tricalcium phosphate into hydroxyapatite affects the characteristics of the porosity network and further modulates the kinetics of the replacement. These results may improve the understanding of the mechanisms of P-sequestration by mineral surfaces through coupled dissolution–precipitation reactions and shed light on the origin of apatite accumulations associated to evaporitic sedimentary rocks. [ABSTRACT FROM AUTHOR]

With the widespread use of gold as a precious metal, the recovery of gold has become an urgent problem to be solved. Therefore, the design and preparation of a sorbent with better adsorbability and higher selectivity for Au(III) is of great significance for recovering gold resources and protecting the environment. In order to obtain an efficient and stable gold ion sorbent, N1,N1′-(1,4-phenylene)bis(N1-(4-aminophenyl)benzene-1,4-diamine) and 2,4,6-tricarboxylisophene were cross-linked by a solvent thermal reaction to synthesize a double-functional covalent organic polymer (N-TPCOP). The N-TPCOP has a very high gold uptake capacity of 3400.38 mg g−1, because it reduces Au(III) to elemental gold by sequestration and redox reactions between functional atoms (N and O) and Au(III). In summary, we have verified the adsorption potential of a novel covalent organic polymer for Au(III), which provides a strong reference for the recycling of precious metal gold in secondary resources and the protection of environmental resources. [ABSTRACT FROM AUTHOR]

In this work, laterite (LA) and rice husk ash (RHA)-based alkali-activated materials (AAMs) with varying %RHA contents (0, 5, 10, 15, and 20%) were prepared for the removal of malachite green (MG) dye from water. The precursors and AAMs were characterized by standard methods (XRF, XRD, TG/DTA SEM, and FTIR). The SEM micrographs and iodine index values showed that the incorporation of RHA improves the microporosity of laterite-based geopolymers. The incorporation of RHA did not result in any new mineral phases after alkalinization. Geopolymerization increased both the adsorption rate and capacity of the geopolymers relative to LA by approximately 5 times. The maximum adsorption capacity was 112.7 mg/g, corresponding to the GP95−5 (5% RHA) geopolymer. The adsorption capacity was therefore not solely controlled by the RHA fraction. The adsorption kinetics data was best predicted by the pseudo-second-order (PSO) model. The adsorption mechanism entails electrostatic interactions and ion exchange. These results show the suitability of laterite-rice husk ash (LA-RHA)-based alkali-activated materials as adsorbents for the efficient sequestration of malachite green in aqueous solution. [ABSTRACT FROM AUTHOR]

An innovative mineral carbonation method was developed to synthesize iron(II) carbonate (FeCO3) by cation complexation using 2,2′-bipyridine as ligand. First, complexes of iron(II) and different ligands were theoretically analyzed and discounted in terms of their temperature and pH-dependent stabilities, iron-ligand interactions, possible by-products and difficulty of analysis, choosing 2,2′-bipyridine as the most suitable ligand. Then, the Job plot was used to verify the complex formula. The stability of [Fe(bipy)3]2+ at pH 1–12 was further monitored for 7 days using UV-Vis and IR spectroscopy. Good stability was observed between pH 3 and 8, decreasing within pH 9–12 where the carbonation reaction occurs. Finally, the reaction between Na2CO3 and [Fe(bipy)3]2+ was performed at 21, 60, and 80 °C and pH 9–12. The total inorganic carbon measured after 2 h shows that the best carbonate conversion (50%) occurred at 80 °C and pH 11, being the most suitable conditions for carbon sequestration. SEM-EDS and XRD were used to examine the effect of synthesis parameters on the morphology and composition of FeCO3. The FeCO3 particle size increased from 10 μm at 21 °C to 26 and 170 μm at 60 and 80 °C respectively with no pH dependence. In addition, EDS analysis supported the carbonate identity, whose amorphous nature was confirmed by XRD. These results would help prevent the iron hydroxide precipitation problem during mineral carbonation using iron-rich silicates. These results are promising for its application as a carbon sequestration method with a CO2 uptake of around 50% obtaining Fe-rich carbonate. [ABSTRACT FROM AUTHOR]

The increasing usage of an important heavy metal chromium for industrial purposes, such as metallurgy, electroplating, leather tanning, and other fields, has contributed to an augmented level of hexavalent chromium (Cr(VI)) in watercourses negatively impacting the ecosystems and significantly making Cr(VI) pollution a serious environmental issue. In this regard, iron nanoparticles exhibited great reactivity in remediation of Cr(VI)-polluted waters and soils, but, the persistence and dispersion of the raw iron should be improved. Herein, this article utilized an environment-friendly celite as a modifying reagent and described the preparation of a novel composites namaly celite decorated iron nanoparticles (C-Fe0) and evaluation of C-Fe0 for the sequestration performance of Cr(VI) from aqueous solution. The results indicated that initial Cr(VI) concentration, adsorbent dosage, and especially solution pH are all critical factors to control C-Fe0 performance in Cr(VI) sequestration. We demonstrated that C-Fe0 could achieve a high Cr(VI) sequestration efficiency with an optimized adsorbent dosage. Fitness of the pseudo-second-order kinetics model with data indicated that adsorption was the rate-controlling step and chemical interaction controlled Cr(VI) sequestration on C-Fe0. The adsorption isotherm of Cr(VI) could be the best depicted by Langmuir model with a monolayer adsorption. The underlying sequestration path of Cr(VI) by C-Fe0 was then put forward, and the combined effect of adsorption and reduction implied the potentials of C-Fe0 in Cr(VI) removal. [ABSTRACT FROM AUTHOR]

Oceanic Anoxic Events (OAEs) are conspicuous intervals in the geologic record that are associated with the deposition of organic carbon (OC)‐rich marine sediment, linked to extreme biogeochemical perturbations, and characterized by widespread ocean deoxygenation. Mechanistic links between the marine biological carbon pump (BCP), redox conditions, and organic carbon burial during OAEs, however, remain poorly constrained. In this work we reconstructed the BCP in the western Tethys Ocean across OAE1a (~120 Mya) using sediment geochemistry and OC mass accumulation rates (OCAcc). We find that OCAcc were between 0.006 and 3.3 gC m−2 yr−1, with a mean value of 0.79 ± 0.78 SD gC m−2 yr−1—these rates are low and comparable to oligotrophic regions in the modern oceans. This challenges longstanding assumptions that oceanic anoxic events are intervals of strongly elevated organic carbon burial. Numerical modelling of the BCP, furthermore, reveals that such low OC fluxes are only possible with either or both low to moderate OC export fluxes from ocean surface waters, with rates similar to oligotrophic (nutrient‐poor, <30 gC m−2 yr−1) and mesotrophic (moderate‐nutrients, ~50–100 gC m−2 yr−1) regions in the modern ocean, and stronger than modern vertical OC attenuation. The low OC fluxes thus reflect a relatively weak BCP. Low to moderate productivity is further supported by palaeoecological and geochemical evidence and was likely maintained through nutrient limitation that developed in response to the burial and sequestration of phosphorus in association with iron minerals under ferruginous (anoxic iron‐rich) ocean conditions. Without persistently high productivity, ocean deoxygenation during OAE1a was more likely driven by other physicochemical and biological factors including ocean warming, changes in marine primary producer community composition, and fundamental shifts in the efficiency of the BCP with associated effects and feedbacks. [ABSTRACT FROM AUTHOR]

The article reports on a new hybrid sorbent containing polyamine-Cu(II) complex, Polyam-N-Cu2+, which shows high CO2 capture capacity at ultradilute concentrations of CO2 in the atmosphere. The sorbent is mechanically strong, chemically stable, and amenable to efficient regeneration by salt solutions at an ambient temperature, including seawater, making it an ideal candidate for use in direct air capture (DAC) systems for removing CO2 from the atmosphere.

Increases in community and industrial activities have led to disturbances of the environmental balance and the contamination of water systems through the introduction of organic and inorganic pollutants. Among the various inorganic pollutants, Pb (II) is one of the heavy metals possessing non-biodegradable and the most toxic characteristics towards human health and the environment. The present study is focussed on the synthesis of efficient and eco-friendly adsorbent material that can remove Pb (II) from wastewater. A green functional nanocomposite material based on the immobilization of α-Fe2O3 nanoparticles with xanthan gum (XG) biopolymer has been synthesized in this study to be applied as an adsorbent (XGFO) for sequestration of Pb (II). Spectroscopic techniques such as scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet visible (UV-Vis) and X-ray photoelectron spectroscopy (XPS) were adopted for characterizing the solid powder material. The synthesized material was found to be rich in key functional groups such as –COOH and –OH playing important roles in binding the adsorbate particles through ligand-to-metal charge transfer (LMCT). Based on the preliminary results, adsorption experiments were conducted, and the data obtained were applied to four different adsorption isotherm models, viz the Langmuir, Temkin, Freundlich and D–R models. Based on the high values of R2 and low values of χ2, the Langmuir isotherm model was found to be the best model for simulation of data for Pb (II) adsorption by XGFO. The value of maximum monolayer adsorption capacity (Qm) was found to be 117.45 mg g−1 at 303 K, 126.23 mg g−1 at 313 K, 145.12 mg g−1 at 323 K and 191.27 mg g−1 at 323 K. The kinetics of the adsorption process of Pb (II) by XGFO was best defined by the pseudo-second-order model. The thermodynamic aspect of the reaction suggested that the reaction is endothermic and spontaneous. The outcomes proved that XGFO can be utilized as an efficient adsorbent material for the treatment of contaminated wastewater. [ABSTRACT FROM AUTHOR]

Most bacteria require iron to grow, yet soluble forms of iron are largely not available to microbes due to a combination of low solubility of ferric ion in the environment and sequestration in proteins and enzymes in living organisms. Microbes therefore compete for iron in various ways, including by production of siderophores, which are ligands with a high affinity for ferric ion and which facilitate transport of Fe(III) into and within bacteria. This review summarizes our work on the classes of siderophores isolated from open ocean isolates, including suites of amphiphilic siderophores that vary in the nature of the fatty acid appendages, photoreactive Fe(III)-siderophore complexes as a result of coordination to α- hydroxy carboxylic acid groups, and a new series of tris catechol siderophores. [ABSTRACT FROM AUTHOR]

Chromium (Cr) is a non-biodegradable heavy metal that persists long in aquatic and terrestrial ecosystems and enters the food chain. It is cytotoxic even at low concentrations and reduces the yield of plants. Plants also have cellular mechanisms to manage the accumulation of metal ions inside the cell to diminish the possible injury from non-essential metal ions. This paper reviews current information on plant response to Cr, a key environmental pollutant. The harmful effects together with absorption, transfer, and aggregation of Cr are discussed. The roles of the cell wall, plasma membrane, and plant microbes as the primary hindrances for Cr ingression into the cell, along with sequestration and compartmentalization process, have also been discussed. Cr-generated oxidative injury is also regarded as the main deliberated effect of Cr toxicity. It interferes with NADPH oxidases (plasma membrane) and the electron transport chains, which develop electron leakage. Some genes related to Cr stress in plants get expressed, and suppression produces protective effects by activating the signal transduction pathways. The expression of genes like BnaCnng69940D and BnaC08g49360D is increased, which is involved in protein kinase activity, signal transduction, and oxidoreductase activity. The increased mRNA levels of Cr stress response proteins, including HSP90-1 and MT-1, have been reported in the Brassica napus plant. The stressed environment around the plants may stimulate the biosynthesis of phytochelatins and metal-binding proteins, which have a protective role in plant's growth and development. [ABSTRACT FROM AUTHOR]

Background: Organic materials carbon is mainly sequestrated in humin. However, the carbon (C) stability of humin with organic materials amendments in different types of soils is mainly affected by organic materials or soil types as well as the enzymatic reaction is important for understanding the C sequestration mechanism of soil. Results: In this study, straw and straw-derived biochar were incorporated into three different types of soils. Using 13C nuclear magnetic resonance (NMR) spectroscopy, the structural composition of humin (Hu) was analyzed, along with the urease and β-glucosidase activities. The results showed that biochar amendment enhanced aryl C to 49.63%–76.55% while straw amendments increased O-alkyl C of Hu to 33.99%–51.70%. Two-way ANOVA analysis revealed significant differences in the impact of soil types and treatments on enzyme activities and functional groups of humin. A significant positive correlation was found between β-glucosidase activity and O-alkyl C, phenolic C, and methoxyl C of humin. In addition, urease activity showed a significant positive correlation with alkyl C of humin. Compared to tobacco straw, tobacco straw-biochar amendment increased β-glucosidase activity for 22.01 mg kg−1 d−1, 26.01 mg kg−1 d−1 and 14.01 mg kg−1 d−1 in three types of soils, respectively. Conclusions: These results showed that β-glucosidase contributed to the transformation of humin functional groups and was influenced by organic materials and soil types, especially the organic materials types. The findings imply that straw or straw-derived biochar application stimulates urease and β-glucosidase activities, which improves the alternation of functional groups of humin in different types of soil. [ABSTRACT FROM AUTHOR]

The present work reports development of a magnetic hydrogel adsorbent material based on the polysaccharide, gum acacia. This graft copolymer nanocomposite hydrogel of gum acacia and poly(3-chloro-2-hydroxypropylmethacrylate) has been made using microwave assisted technique. Magnetite nanoparticles have been generated by in-situ method and trapped in the network structure. The parent hydrogel and the hybrid nanocomposite were evaluated as adsorbents for sequestration of cationic dyes and metal ions from aqueous solution. The FTIR, XRD, SEM, TGA, VSM and BET studies have been performed to characterize the samples with respect to their physical and chemical structure, surface nature, thermal stability and magnetic property. The nanocomposite displayed super-paramagnetic nature owing to the presence of magnetite nanoparticles which also influenced the adsorption characteristics favourably as evident from the comparative studies performed with the non-magnetic parent gel. The nanocomposite exhibited larger surface area of 2.524 m2g−1 compared to the parent hydrogel with surface area of 0.481 m2g−1. The adsorption capability of the parent hydrogel towards methylene blue, rhodamine 6G, Cu(II) and Hg(II) are 224.4, 283.5, 282.4 and 275.3 mgg−1, respectively, were enhanced to 265.2, 344.4, 307.5 and 292.8 mgg−1, respectively, in the case of nanocomposite. The adsorption isotherm and kinetic studies indicated fit of Freundlich isotherm model and pseudo-second-order kinetic model, respectively. The adsorption has been shown to be a multistep process involving boundary layer diffusion and intra-particle diffusion playing major roles. The thermodynamic analysis manifested the adsorption as an exothermic and spontaneous process. The adsorption–desorption process studied in three cycles indicated excellent reusability characteristics of the nanocomposite making it a promising adsorbent material for wastewater treatment. [ABSTRACT FROM AUTHOR]

The demand for economic heavy metals has recently sparked a lot of interest in various areas of research and industry. The novelty of this work is the synthesis of grafted guar gum hydrogel and using as adsorbent for the recovery of Cd(II) and Cu(II) ions from acidic solutions. Chemical and physical characterizations of the prepared hydrogel were performed via FT-IR, TGA, BET, and SEM–EDX analyses. The optimum experimental settings using batch technique were investigated. The maximum static adsorption capacities of the grafted hydrogel adsorbent were 99 mg/g for Cd(II) ions and 90.3 mg/g for Cu(II) ions. Freundlich, Langmuir, and Temkin models accurately described the sorption isotherm data. Various thermodynamic parameters were determined. The results showed that a pseudo-second order was predominant in the sorption kinetics of both Cd(II) and Cu(II) ions. Both metal ions could successfully be desorbed using 5 M HCl and 1 M EDTA, while the latter exhibited higher desorption efficiency. The regeneration experiments indicated that prepared hydrogel could maintain adsorption capacities after 5 cycles of adsorption regeneration with negligible decreasing efficiency (less than 1%). As a result, it is regarded as a promising adsorbent in variety of industrial applications. [ABSTRACT FROM AUTHOR]

The potential of a biosorbent derived from Arundo donax stem, a readily available agricultural product, was examined to remove Cr(VI) from water. Various techniques such as XRD, FTIR, SEM, and EDX were used for the characterization of the prepared adsorbent. The optimal pH for Cr(VI) biosorption was found to be 2.0. The experimental data best suits the Langmuir isotherm model and pseudosecond-order kinetics. The maximum biosorption capacity (qmax) of the investigated biosorbent for Cr(VI) was evaluated to be 76.92 mg/g by the Langmuir model. From the results of the Cr(VI) biosorption using charred Arundo donax stem powder (CADSP), it can be a novel, cost-efficient, and effective material for removing Cr(VI) from water and wastewater. [ABSTRACT FROM AUTHOR]

In the present study, alginate@silver nanoparticles (Alg@AgNPs) bionanocomposite has been fabricated successfully and further explored for the removal of crystal violet (CV) dye from the aqueous solution. The surface morphology of the (Alg@AgNPs) bionanocomposite was characterized by various modern analytical techniques such as SEM-EDX, TEM, FTIR and XRD. The maximum adsorption was observed at optimum condition of (pH 7, adsorbent dose 0.01 g, equilibrium time 240 min and initial concentration 20 mg L−1). The maximum monolayer adsorption capacity was found to be 186.93 mg g−1 at 30 °C. The experimental data were further validated by various isotherm models and on the basis of highest correlation coefficient (R2, 0.99), Langmuir model was found to be best fitted model. Pseudo-second order kinetic model obeyed best for the experimental data with a highest correlation coefficient (R2, 0.99) at all studied temperature. In thermodynamic studies, the positive value of enthalpy change (∆ H 0 ) and entropy change (∆ S 0 ) confirmed the process to be endothermic and spontaneous in nature. Desorption studies shows that 83 % of the adsorbed CV can be desorbed in first cycle and can be regenerated up to 4th cycle effectively with 0.1 M HCl. Therefore, (Alg@AgNPs) bionanocomposite could be harnessed as a potential adsorbent for the removal of hazardous CV dye from the waste water. • Alginate@silver nanoparticles (Alg@AgNPs) bionanocomposite has been fabricated successfully. • The maximum monolayer adsorption capacity was found to be 186.93 mg g−1 at 30 °C. • Langmuir model was found to be best-fitted model. • Desorption data showed that above 83 % of CV by using 0.1 M HCl could be desorbed in a first cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • s-ZVI-coupled Myriophyllum aquaticum- derived biochar favors C storage more than I.H. • Biochar nature or feedstock may control C trap and N removal gains from Fe-C coupling. • Biochars trigger C dynamics depending on trade-offs between priming and increased MBC. • Enhanced iron gate contributes to synergistic C sequestration and C sink augmentation. • β -glucosidase activity and Fe-OC increases jointly drive C cumulation in Fe-C ditches. Carbon dioxide (CO 2) is a more powerful greenhouse gas due to its enhanced instantaneous radiative forcing. Since agricultural ecological ditches (eco-ditches) controlling agricultural non-point source pollution are potential CO 2 hotspots, carbon capture technologies must be deployed immediately to sequester carbon and combat climate change. Zero-waste biochar, a negative-carbon technology, remains contentious regarding C sequestration. Iron (Fe) enhances long-term organic carbon (OC) preservation, but the cascading effects of Fe-biochar interactions on the promotion of C accumulation are unclear in eco-ditches. In this paper, we fill these research gaps and employ sponge iron (s-ZVI) and biochar coupling (Fe-C) to enhance the iron gate C protection in eco-ditches. The results reveal that Myriophyllum aquaticum(M.A.) -derived biochar prepared by low-temperature pyrolysis (Biochar_M.A.) enjoys the highest FI, the lowest SUVA254 and SUVA280 and moderate dissolution stability. The coupling of s-ZVI and environmentally compatible Biochar_M.A. achieve a triple benefit situation of C sequestration, C sink, and pollutant removal. Overall carbon gain is jointly determined by abiotic controls and biotic controls. The carbon burial effects of biochar-amended eco-ditches are mainly controlled by the trade-offs between Fe-bound OC mineralization via the biochar-induced prime effect and preservation of OC derived from microbial biomass. The unique Fe-C boosts the rusty sink and yields a negative priming as a result of the dominance of Fe-OC. The upregulated β -glucosidase activity and new-formed Fe-OC indirectly and directly contribute to overall C gain in Fe-C-filled eco-ditches, respectively. These findings provide novel insights into the coupled biotic-abiotic contribution mechanisms underlying the iron gate and reverse enzyme latch phenomenon and advance more robust and prospective theoretical knowledge of C dynamics that are not restricted to eco-ditches, soil, constructed wetlands C storage. [ABSTRACT FROM AUTHOR]

The utilization of fibrous prunus dulcis seed shell powder (UPDSSP) and the phosphate-modified derivative (P-MPDSS) for the abstraction of Pb2+ was tested. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray (EDX), and the physicochemical characterizations revealed desirable characteristics of the adsorbents for efficient Pb(II) uptake. The FTIR of UPDSSP and P-MPDSS showed several functionality groups on the adsorbents. SEM morphology revealed high porosity surface structure of both adsorbents, while BET measurements showed an increase in surface area from 5.84 m2/g to 11.32 m2/g after phosphate modification. The modified adsorbent showed higher Pb(II) uptake than UPDSSP at variations of temperature, time, pH, metal concentration, and material dosage. pH 5.0 was optimum for Pb(II) adsorption and equilibrium was reached at 90 min on UPDSSP and P-MPDSS. The Freundlich isotherm presented the best fit (R2 > 0.991) than the Langmuir and Dubinin-Raduskkevich models. The pseudo-second-order gave the best fit (R2 > 0.971) than the pseudo-first-order and intraparticle diffusion kinetic equations. Thermodynamics showed endothermic, spontaneous, and physical adsorption of Pb(II) ions onto the adsorbents. The adsorbents showed good potentials for regeneration and reuse. The results revealed UPDSSP and P-MPDSS as viable materials for the decontamination of Pb polluted water. [ABSTRACT FROM AUTHOR]

The reduction and sequestration of toxic Cr(VI) via a one-step process in an aqueous solution is critical to eliminate its environmental risk. In this study, amine functionalized cellulose-based aerogel beads (CGP) was developed for simultaneous and efficient adsorption- reduction- sequestration of Cr(VI). CGP showed a maximum Cr(VI) adsorption capacity of 386.40 mg/g at 25 °C due to its strong electrostatic attraction towards Cr(VI). The simultaneous Cr(VI) adsorption- reduction- sequestration performance of CGP over a wide Cr(VI) concentration range was examined. The mechanism was investigated in-depth via the analysis of adsorption kinetics, XPS spectra, and FTIR spectra. Moreover, the Cr immobilization stability of CGP after adsorption was evaluated in simulated neutral, acidic, and alkaline conditions. The effect of pH, temperature, ionic strength and the presence of interfering ions on CGP adsorption performance were investigated by batch adsorption experiments. Fixed-bed column adsorption study was performed to explore the application potential of CGP beads in a wastewater treatment process. [Display omitted] [ABSTRACT FROM AUTHOR]

For the hardship imposed on patients, Silas Weir Mitchell's Rest Cure remains notorious. This essay reconstructs Mitchell's philosophy of care, primarily scrutinizing his understanding of sympathy as a vector for the person-to-person transmission of mental illness. The praxis of sequestration central to Rest Cure methodology functioned as a quarantine measure, designed to prevent bystanders from interacting sympathetically with ailing patients and acquiring analogous disorders. Engagements with the antisympathetic components of Mitchell's treatment had a formative impact on Charlotte Perkins Gilman, a former patient, and Sigmund Freud, a Rest Cure practitioner. Gilman would later fashion sympathy into an emancipatory force for utopia. Freud would become disillusioned with the Rest Cure by the time of Studies on Hysteria , even as the volume's case histories conform to a paradigm of contagious neuroses. Freud remained cautious of sympathy's pathological properties, and his concerns survive in psychoanalytic prohibitions against emotive interface between doctor and patient. [ABSTRACT FROM AUTHOR]

Intensification of industrial activity, environment stress contributes to the significant rise of heavy metal pollution in water resources. Pollution due to malignant heavy metals such as lead, chromium, arsenic etc., has been tremendously focused on communal health. Lead pollution-potable water finds great threat by different sources like plating units, lead pipes etc., Newspaper is a cellulosic materials, containing cellulose, hemicellulose and other inorganic fillers. The present study evaluates the potentiality of modified newspaper pulp for sequestration of Pb(II) ions. Characterizations of loaded and unloaded pulp were evaluated by FTIR, SEM and EDAX assay. Batch experimental studies were accomplished to assess the equilibration between the sorbate-sorbent through various operating factors viz., pH, dosage, time course, initial concentration, influence of ions, co-ions and effect of temperature. The residual concentrations of the Pb2+ ions from aqueous solutions are examined by UV-Visible Spectrophotometer. The equilibrium data was appropriately fitted with Langmuir adsorption isotherm model. [ABSTRACT FROM AUTHOR]

Capillary trapping is considered as one of the safest geologic CO2 storage mechanisms due to its hydrodynamic stability. However, the thermodynamic stability of capillary trapping was questioned by our recent work (Xu in Geophys Res Lett 46(23):13804–13813, 2019). Gravity induces the top bubbles to grow at expense of bottom bubbles through the diffusion of dissolved gas components, that finally may form a gas cap and posing a risk of leakage, even in absence of convection. Here, we improve the gravity-induced ripening model introduced earlier and conduct theoretical and numerical analysis. Four regimes of bubble ripening are identified according to the modified Bond number and initial gas saturation, resulting in different scaling between the equilibrium time and the length scale. Vertical heterogeneity is also shown to have a great impact on the ripening process. When the permeability gradient is downward, the capillary pressure gradient competes with the gravitational gradient and results in a complex gas redistribution behavior. Capillarity dominates in a short time, while gravitational potential determines the global saturation profile in long term. This work provides a new physical perspective in evaluating CO2 sequestration security and has a potential application in other porous systems that gas generated and evolve under strong external fields. [ABSTRACT FROM AUTHOR]

As important parts of microbe–mineral associations, microalgae–montmorillonite composites are common in nature environment, which have been overlooked for a long time. In this study, the binding of Cd(II) in the montmorillonite, microalgae and their 1:5, 1:10 mass ratio composites interface were investigated. The results showed that maximum adsorption capacity of 1:5 and 1:10 mass ratio binary composites were 65.25 mg g−1 and 55.49 mg g−1, respectively, which both higher the theoretically calculated capacity from single montmorillonite and microalgae at pH 5.5. Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that phosphoryl and carboxyl functional groups on the algal cellular surface played major roles in both microalgae–montmorillonite composite formation and Cd(II) adsorption. Extended X-ray absorption fine structure (EXAFS) further probed that higher sorption on composites were attributed to Cd(II) bridging between microalgae and montmorillonite, in which monodentate phosphoryl-Cd and carboxyl-Cd complexes on microalgae side, leading Cd(II) to a more stabilized state. In addition, the montmorillonite promoted dispersion of microalgae, releasing more carboxyl and phosphoryl functional groups as Cd(II) binding sites on the microalgae surface. These findings highlight the function of microalgae in the microalgae–clay mineral associations for Cd(II) fixation and provide further insight into the sequestration and migration of toxic metals in natural environments. [ABSTRACT FROM AUTHOR]

Nanomaterials have gained much attention in the field of environmental remediation, largely due to their high surface area-to-volume ratio and other unique physical, chemical, and biological characteristics that emerge due to its size effects. Metallic nanoparticles are traditionally manufactured using wet chemical processes; however, the chemicals utilized are generally hazardous and combustible. The biosynthesis of nanoparticles using a variety of plant resources is considered a green technology because it does not use toxic chemicals. This work focuses on the green synthesis of biogenetic silver nanoparticles and their use in the sequestration of colorants from aqueous solution. The extract of aquatic macrophyte Salvinia molesta (water hyacinth) has been employed to prepare silver nanoparticles by chemical reduction reaction. In the UV-visible spectrum of the synthesized silver nanoparticles, the absorbance peak was detected in the 420–430 nm range. The synthesized silver nanoparticles were used to sequester methylene blue (MB) dye in aqueous solution. About 121.04 mg/g was found as the highest adsorption capacity of methylene blue dye on the silver nanoparticles according to the Langmuir isotherm. It was observed that the experimental results and the pseudo-second order kinetics are in good agreement. As a result, the biosynthesized silver nanoparticle might be a potential adsorbent material in the field of environmental rehabilitation and cleanup. [ABSTRACT FROM AUTHOR]

Innovative methods for effectively sequestering significant amounts of carbon dioxide (CO 2) are required to address the ongoing problem of greenhouse gas emissions, which have increased in tandem with industrial development. Optimisation of the performance of the photobioreactor remains a challenge, despite the potential of using photobioreactors and cyanobacteria for bio sequestration. A potential solution lies in the development of a hybrid photobioreactor design. Thus, this study aims to develop a hybrid design of the photobioreactor equipped with tailor-made real-time monitoring system known as FCB2022 for cultivating Spirulina platensis. The performance is evaluated by monitoring real-time data such as pH, dissolved oxygen (DO), and temperature, alongside assessing the growth kinetic of cyanobacterium, CO 2 sequestration, oxygen release rate and mass carbon balance. These assessments are conducted under varying photon flux densities (PFD) of 100µmol/ (m2.s), 200µmol/ (m2.s), and 300µmol/ (m2.s). The result demonstrates that FCB2022 exhibited high hydrodynamic performance with parameters like mixing time, circulation time, Reynold number, and empty bed residence time showing favourable values. The optimal ranges for temperature, pH, and dissolved oxygen are determined to be between 23.56 and 29.11 ⁰C, 9.03–9.58, and 6.57–6.89 mgO 2 /L, respectively. Under the conditions of 15% CO 2 and PFD of 300µmol/ (m2.s), the specific growth rates reach 0.36±0.004 /day and maximum biomass concentration attains 1.52±0.03 kg/m3. Notably, the PFD of 300µmol/ (m2.s) yields the highest conversion of carbon into biomass, ranging from 1.09×10−02 kg to 1.26×10−02 kg, representing the yield of 31–83% in each CO 2 injection treatment. [Display omitted] • S. platensis is cultivated in hybrid photobioreactor with real-time monitoring. • Hybrid photobioreactor enables sequential occurrence of light and dark reactions. • Biomass production is increased by high photon flux density. • Enriched carbon dioxide air stream feed enhanced biomass productivity. [ABSTRACT FROM AUTHOR]

This correction notice is for an article titled "Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes" published in Nature Communications. The correction addresses an error in the original version of the Supplementary Information, where the citation for certain sites was incorrect. The correction provides the accurate citation and updates the HTML version of the Supplementary Information accordingly. The article was authored by a group of researchers and includes their names at the end of the correction notice. [Extracted from the article]

CO2 in the atmosphere is a major contributor to global warming but at the same time it has the potential to be a carbon source for advanced biomanufacturing. To utilize CO2, carbonic anhydrase has been identified as a key enzyme. Furthermore, attempts have been made to accelerate the sequestration via pressure. This study aims to combine both approaches to achieve high sequestration rates. The carbonic anhydrase of the alkaliphilic cyanobacterium Coleofasciculus chthonoplastes (cahB1) and bovine carbonic anhydrase (BCA) are introduced into a high‐pressure reactor to catalyze the hydration of CO2 at up to 20 bar. The reactor is filled with a CaCl2 solution. Due to the presence of Ca2+, the hydrated CO2 precipitates as CaCO3. The impact of the carbonic anhydrase is clearly visible at all pressures tested. At ambient pressure a CO2 sequestration rate of 243.68 kgCaCO3/m3 h for cahB1 was achieved compared to 150.41 kgCaCO3/m3 h without enzymes. At 20 bar the rates were 2682.88 and 2267.88 kgCaCO3/m3 h, respectively. The study shows the benefit of a combined CO2 sequestration process. To examinate the influence of the enzymes on the product formation, the precipitated CaCO3 was analyzed regarding the crystalline phase and morphology. An interchange of the crystalline phase from vaterite to calcite was observed and discussed. [ABSTRACT FROM AUTHOR]

It is important that a pollution remediation system be able to cater for a variety of pollutant species present in the water to be treated. The aim of this study was to utilise a series of commercial zeolites (H-MOR, H-β, and H-ZSM5) for the concomitant adsorption and photodegradation of Cu2+ and tetracycline (TC) molecules. The adsorbent cum photocatalyst was characterised by SEM and FTIR. FTIR confirmed the key functional groups (Si-O-Si and Al-O-Si) in the series of zeolites, and H-β zeolite was demonstrated to be the most effective adsorbent cum photocatalyst for both adsorption and photodegradation of Cu2+ and TC molecules. These results were further corroborated from the pseudo-first-order rate constant values. Among the investigated zeolites, H-ZSM5 displayed the least adsorption and photodegradation performance for Cu2+ and TC molecules. The photolysis reaction confirms the significant role of zeolites in the photodegradation test, as low performance was recorded in the absence of the zeolites. [ABSTRACT FROM AUTHOR]

The shale fracture permeability is critical in determining gas production and deep CO2 sequestration performance. Moreover, how shale fracture permeability evolves after interactions with supercritical carbon dioxide (Sc-CO2) should be understood to constrain the shale reservoir permeability and evaluate the long-term sealing ability of shale formations. In this research, we conducted soaking experiments with shale fractures and Sc-CO2 at various times and then measured the shale fracture permeability and hydraulic aperture evolution under different stress states. Additionally, we quantify the chemical compositions, pore characteristics, fracture surface roughness alternation through X-ray diffraction, nuclear magnetic resonance, scanning electron microscope, and optical profilometry techniques. Our results indicate that soaking with Sc-CO2 will dramatically increase the shale fracture permeability and aperture due to the calcite and dolomite dissolution. This free-face dissolution process will remove the mineral particles in the fracture surface, resulting in larger pores, peaks, and valleys in the fracture surfaces. This process may last for seven days, and after that, chemical reactions may terminate, and the rock-Sc-CO2 system turns stable. Our results explain how Sc-CO2 alters the shale fracture permeability through the chemical dissolution of specific minerals from a microscale analysis. [ABSTRACT FROM AUTHOR]

Sequestration of plant secondary metabolites by herbivores can vary across both host plant phenology and herbivore ontogeny, but few studies have explored how they concurrently change in the field. We explored variation in iridoid glycoside concentration and composition in white turtlehead, Chelone glabra, as well as sequestration of iridoid glycosides by its specialist herbivore, the Baltimore checkerspot, Euphydryas phaeton, across the development of both herbivore and host plant. In 2012 we sampled plants to describe seasonal variation in the concentrations of two iridoid glycosides, aucubin and catalpol. In 2017, we sampled both host plants and caterpillars over an entire growing season and explored the relationship between plant chemistry and herbivore sequestration. We also compared iridoid glycoside concentrations of plants with and without herbivory to gain insight into whether levels of secondary compounds were impacted by herbivory. We found that total plant iridoid glycosides varied across the season and that total sequestered iridoid glycosides in caterpillars closely mirrored concentration patterns in plants. However, the magnitude of sequestration by caterpillars ranged from 2 to 20 times the concentrations in host plants, with different proportions of aucubin and catalpol. In addition, plants with herbivory had lower iridoid glycoside concentrations than plants without herbivory, although this difference changed over time. These results suggest that while variation in host plant secondary metabolites may be a dominant factor driving sequestration, other ecological factors may mitigate the relationship between host plant chemistry and herbivore sequestration. [ABSTRACT FROM AUTHOR]

Multicopper oxidases (MCOs) represent a diverse family of enzymes that catalyze the oxidation of either an organic or a metal substrate with concomitant reduction of dioxygen to water. These enzymes contain variable numbers of cupredoxin domains, two, three or six per subunit, and rely on four copper ions, a single type I copper and three additional copper ions organized in a trinuclear cluster (TNC), with one type II and two type III copper ions, to catalyze the reaction. Here, two crystal structures and the enzymatic characterization of Marinithermus hydrothermalis MCO, a two‐domain enzyme, are reported. This enzyme decolorizes Congo Red dye at 70°C in the presence of high halide concentrations and may therefore be useful in the detoxification of industrial waste that contains dyes. In two distinct crystal structures, MhMCO forms the trimers seen in other two‐domain MCOs, but differs from these enzymes in that four trimers interact to create a dodecamer. This dodecamer of MhMCO forms a closed ball‐like structure and has implications for the sequestration of bound divalent metal ions as well as substrate accessibility. In each subunit of the dodecameric structures, a Trp residue, Trp351, located between the type I and TNC sites exists in two distinct conformations, consistent with a potential role in facilitating electron transfer in the enzyme. [ABSTRACT FROM AUTHOR]

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by μ-ED-XRF mapping on selected samples. [ABSTRACT FROM AUTHOR]

[Display omitted] Accessibility to quality and clean water has in recent times been compromised due to the presence of pollutants, thus posing as a threat to the survival of living organisms. The adsorption technique in this regard has been observed to be useful in the remediation process with the material used as the adsorbent playing an integral role. In this study, a novel biocomposite (PN-Fe 3 O 4 -IDA-Al) based on peanut husk (a low-cost material) was developed by functionalization with aluminum (Al), iminodiacetic acid (IDA) and Fe 3 O 4. The efficiency of PN-Fe 3 O 4 -IDA-Al as an adsorbent for the remediation of wastewater was evaluated using Congo red (CR) and phosphates (PO 4 3−) as model pollutants. The results from the characterization studies confirmed PN-Fe 3 O 4 -IDA-Al to have superparamagnetic properties which ensures its easy retrieval. Adsorption studies indicated that PN-Fe 3 O 4 -IDA-Al had a maximum monolayer capacity of 79.0 ± 2.0 and 16.8 ± 2.5 mg g−1 for CR and PO 4 3− (according to P), respectively, which was significantly dependent on factors such as reaction time, solution pH, temperature and the presence of some common anions. The Freundlich model was observed to better describe both adsorption processes with chemisorption being the principal underlying mechanism. Results from using real water samples confirmed PN-Fe 3 O 4 -IDA-Al to be highly efficient for practical remediation processes. These results coupled with the synthesis of PN-Fe 3 O 4 -IDA-Al under benign conditions using low-cost materials help to expound the knowledge on the use of low cost materials as the basis for the development of highly efficient adsorbents for wastewater remediation. [ABSTRACT FROM AUTHOR]

Marine sedimentation rate and bottom-water O2 concentration control organic carbon remineralization and sequestration across continental margins, but whether and how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena) across shelf and slope sediments is still unclear. Here we reveal distinct microbiome structures and functions, amidst comparable pore fluid chemistries, along 300 cm sediment horizons underlying the seasonal (shallow coastal; water depth: 31 m) and perennial (deep sea; water depths: 530 and 580 m) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western Indian margin. The sedimentary geomicrobiology was elucidated by analyzing metagenomes, metatranscriptomes, enrichment cultures, and depositional rates measured via radiocarbon and lead excess dating; the findings were then evaluated in light of the other geochemical data available for the cores. Along the perennial-OMZ sediment cores, microbial communities were dominated by Gammaproteobacteria and Alphaproteobacteria , but in the seasonal-OMZ core communities were dominated by Euryarchaeota and Firmicutes. As a perennial-OMZ signature, a cryptic methane production–consumption cycle was found to operate near the sediment surface, within the sulfate reduction zone; overall diversity, as well as the relative abundances of anaerobes requiring simple fatty acids (methanogens, anaerobic methane oxidizers, sulfate reducers, and acetogens), peaked in the topmost sediment layer and then declined via synchronized fluctuations until the sulfate–methane transition zone was reached. The microbiome profile was completely reversed in the seasonal-OMZ sediment horizon. In the perennial-OMZ sediments, deposited organic carbon was higher in concentration and rich in marine components that degrade readily to simple fatty acids; simultaneously, lower sedimentation rate afforded higher O2 exposure time for organic matter degradation despite perennial hypoxia in the bottom water. The resultant abundance of reduced carbon substrates eventually sustained multiple inter-competing microbial processes in the upper sediment layers. The entire geomicrobial scenario was opposite in the sediments of the seasonal OMZ. These findings create a microbiological baseline for understanding carbon–sulfur cycling in distinct depositional settings and water column oxygenation regimes across the continental margins. [ABSTRACT FROM AUTHOR]