Mineralization Kinetics Research Articles

Calibration of the dual clumped isotope thermometer for carbonates

The Δ47 (paleo)thermometer has opened a new avenue to determine carbonate formation temperatures independent of the oxygen isotopic composition of the fluid from which the carbonate crystallized. A major limitation of this thermometer is related to kinetic effects if homogeneous isotopic equilibrium is not attained during carbonate precipitation. Dual clumped isotope thermometry – the high-precision analysis of Δ48 along with Δ47 in CO2 evolved from phosphoric acid digestion of carbonates – makes it possible to resolve temperature from the kinetic information recorded in an individual carbonate phase. Therefore, it provides a new opportunity to identify (bio)mineralization pathways and to determine carbonate formation temperatures devoid of a kinetic bias, based solely on isotopic analysis of a single carbonate phase.Identification of the nature and extent of kinetic effects as well as the reconstruction of accurate formation temperatures requires knowledge of the position of equilibrium in Δ47 vs Δ48 space. Here, we present Δ47 and Δ48 data of carbonates that were previously considered as having crystallized closest to equilibrium in a temperature range of 8 to 1100 °C. Across this range, the temperature dependences of Δ47 and Δ48 are best expressed by the following fourth order polynomials of 1/T:Δ47 (CDES 90) (‰) = 1.038 (−5.897 1/T − 3.521 103 1/T2 + 2.391 107 1/T3 − 3.541 109 1/T4) + 0.1856Δ48 (CDES 90) (‰) = 1.028 (6.002 1/T − 1.299 104 1/T2 + 8.996 106 1/T3 − 7.423 108 1/T4) + 0.1245with CDES 90 representing the Carbon Dioxide Equilibrium Scale at a reaction temperature of 90 °C. In its entire temperature range, our Δ47 (CDES 90) - T - relationship agrees within 2 ppm with two previous Δ47 (I-CDES) - T - relationships reported by Jautzy et al. (2020) and Anderson et al. (2021). Accuracy of our proposed Δ47 (CDES 90) − Δ48 (CDES 90) equilibrium relationship is independently confirmed by additional dual clumped isotope data of experimental and geothermal carbonates which precipitated from potentially equilibrated dissolved inorganic carbon pools at a temperature range of 25–100 °C. Furthermore, we reprocessed original dual clumped isotope data of natural carbonates (Bajnai et al., 2020) and compared their composition to the position of equilibrium in Δ47 vs Δ48 space. These results corroborate preliminary evidence that the hydration/hydroxylation reactions became rate-limiting during the calcification of a speleothem-like sample, a warm water coral, a cold water coral and a brachiopod, finally evoking significant departures of carbonate-Δ47 and -Δ48 from dual clumped isotope equilibrium.An anti-clumped Δ48 value of −419 (±16) ppm (95% confidence interval level) is obtained for a technical calcite that was precipitated by the injection of CO2 into a Ca(OH)2-saturated solution. Its negative Δ48 value largely arises from a combinatorial effect, i.e. the carbonate oxygen derives from two sources with different bulk isotopic compositions. Besides the identification of the nature and the extent of (bio)mineralization kinetics and the reconstruction of carbonate formation temperatures unbiased by kinetics, dual clumped isotope analysis, therefore, allows tracing the isotopic heterogeneity of oxygen pools contributing to carbonate formation.

Chemical kinetic modeling of organic pollutant degradation in Fenton and solar photo-Fenton processes

The oxidation of organic pollutants by Fenton's reagent is commonly considered as a single-stage process that conforms to pseudo first-order kinetics. However, pollutant oxidation would exhibit a two-stage pattern when the initial dosage of Fenton's reagent is sufficiently high. This study investigated the fast oxidation kinetics of a model pollutant, malachite green (MG), in Fenton process in real time using continuous on-line spectrophotometric detection. A chemical kinetic model was further developed, which could well predict the effect of initial concentrations of Fe2+, H2O2, and MG on the degradation of MG in Fenton and solar photo-Fenton processes. The model could also be adapted to model the kinetics of MG mineralization. Modeling results reveal that the significant enhancement in the degradation rate of MG in the second stage of Fenton process by sunlight irradiation was contributed mainly by the production of hydroxyl radicals from H2O2 photolysis. The chemical kinetic model also performed well in describing the degradation and mineralization kinetics of carbendazim and thiabendazole in solar photo-Fenton process. The improved understanding on the fast kinetics of pollutant degradation and the chemical kinetic model developed could help optimize the treatment conditions for organic pollutants in Fenton and solar photo-Fenton processes.

Particle carbonation kinetics models and activation methods under mild environment: The case of calcium silicate

CO2 mineralization is an economical technology with a low carbon footprint and has been considered an effective means to achieve carbon fixation. The slow diffusion and reaction in the gas-solid system of CO2 mineralization is a common issue affecting the normal carbonation depth. The surface water plays a critical role as an ionic mass transferring medium in the reaction systems. By studying the CO2 mineralization of dispersed calcium silicate (CS) particles, this work systematically revealed the kinetics and mechanisms of carbonation under mild environments (below 80°C). It was interesting to find that carbonation of CS particles followed different kinetic mechanisms depending on the temperature and with the migration of surface water. At 20°C, the CO2 mineralization reaction conformed to the unreacted shrinking-core mechanism with the primary reaction rate-limiting step of product layer diffusion. For higher temperatures (40–80°C), the carbonation process was controlled by the surface water coverage. The leaching behavior of CS indicated that electrical double layer (EDL) formed at the particle interface and limited Ca2+ activity in water film might be the mechanism of surface water coverage controlled kinetics. Accordingly, the enhanced CO2 mineralization of CS, 58.16% CO2 uptake increment, was realized at 80°C through rehydration activation. The evolution of mineral micromorphology with process of leaching and carbonation is characterized by semi-quantitative XRD analysis and mercury intrusion porosimetry analysis. CO2 mineralization kinetics and the proposed activation method under mild environment open the door to efficient CO2 mineralization with low energy consumption.

Thermal Decomposition Kinetics of Rare Earth Minerals in Tailings with Addition of MgO

Due to the advantage in deactivating fluorine and enhancing the decomposition of rare earth (RE) minerals, MgO was applied to the magnetizing roasting of Bayan Obo tailings in this work. The effects of MgO dosages, roasting temperature, and holding time on the decomposition rate of RE minerals were experimentally studied. With a MgO dosage of 10 wt.%, the decomposition rate of RE minerals reached 98.09% at 750 °C. The phase composition of roasted samples was characterized by XRD and SEM-EDS. The incomplete decomposition rate was investigated with the observation of leaching residual by SEM-EDS. The decomposition kinetics of the RE minerals with the addition of MgO was analyzed with the Ginstling-Brundshtein model, where the reaction rate was controlled by chemical reaction.

Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

Maintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

Energy consumption and reaction rate optimization combining turbulence promoter and current modulation for electrochemical mineralization

• Distinct turbulence promoters were assessed for the electrooxidation of phenol. • Plastic mesh and reticulated vitreous carbon performed equally well to degrade phenol. • Combined modulated and constant current modes led to higher mineralization efficiency. • Use of turbulence promoters and modulated current led to a shorter treatment time. • Low energy consumption and treatment cost were also obtained for this new setup. Electrooxidation stands out as a promising technique for treating effluents containing toxic organic compounds. However, the high energy consumption remains an obstacle to its large-scale application. The aim of this work was to optimize the electrooxidation process by combining current modulation, where the applied current was maintained close to the limiting value, with turbulence promoters (TPs) to improve the mass transfer, consequently shortening the mineralization time. Electrooxidation was performed in an electrochemical flow reactor, with phenol selected as a model compound. A plastic mesh turbulence promoter (MTP) and reticulated vitreous carbon (RVC) were evaluated as TPs. The combined approach enabled reduction of the energy consumption from 168 ± 31 kWh kg −1 TOC (galvanostatic mode) to 72 ± 6 kWh kg −1 TOC [modulated current (MC) + MTP]. Additionally, the improvement of the mineralization kinetics reduced the electrolysis time by ~30%. Under galvanostatic conditions, use of the RVC outperformed the mineralization performance observed using the MTP, but similar efficiency was observed applying the MC mode at low flow velocities. The results reinforced the potential of electrooxidation as an option for the treatment of effluents, paving the way to obtain a process with fast degradation kinetics and high mineralization efficiency, leading to low energy consumption.

Reactive transport numerical modeling of CO<sub>2</sub>+O<sub>2</sub> <italic>in-situ</italic> leaching in sandstone-type uranium ore

The CO2+O2 in situ leaching (ISL) technique represents the third generation of in situ uranium leach mining in China. The key point of CO2+O2 ISL is the interaction between the complex hydrodynamic behavior and geochemical reactions. To deal with hydrodynamic evolution, leaching solutions-rock interaction, and reactive kinetics of uranium minerals during ISL uranium mining, a CO2+O2 ISL reactive transport numerical simulation implemented in TOUGHREACT is proposed herein in Qianjiadian uranium deposit. In this study, we developed a chemical thermodynamic database suitable for sandstone-hosted uranium deposits and a method for modeling the kinetic uranium dissolution under the control of oxygen (O2(aq)) and bicarbonate (HCO3–). We conduct a sensitivity analysis to assess the effect of the uncertainties associated with the modeling parameters on the simulation results. The reactive transport simulation successfully reproduced the behavior of dynamic uranium recovery. The sensitivity analysis showed that the initial volume of uranium (uranium grade) and injecting oxygen concentration were very sensitive to changes in the leaching concentration of uranium. This study provides technical support for accurate simulation and dynamic regulation of the CO2+O2 leaching process at a large mining area.

Environmental aspects of UV-C-based processes for the treatment of oxytetracycline in water.

This study is focused on oxytetracycline (OTC) degradation by direct photolysis (UV-C) and photobased advanced oxidation processes (AOPs) (UV-C/H2O2 and UV-C/S2O82-). OTC degradation pathways were revealed by LC-MS/MS and GC-MS/MS analyses. The evolution/degradation profiles of 12 detected byproducts were correlated with changes in biodegradability and toxicity toward Vibrio fischeri recorded during the treatment. Both photobased AOPs yielded higher OTC degradation and mineralization rates than direct photolysis. The OTC degradation pathway was found to be rather specific regarding the main reactive species (HO• or SO4•-)/mechanism, yielding different patterns in toxicity changes, while biodegradability profiles were less affected. Biodegradability was correlated with the observed degradation and mineralization kinetics. The recorded toxicity changes indicate that byproducts formed by initial OTC degradation are more toxic than the parent pollutant. The prolonged treatment resulted in the formation of byproducts that contributed to a decrease in toxicity and an increase in biodegradability, as particularly emphasized in the case of UV-C/S2O82-.

Temperature effects on carbon mineralization of sinking copepod carcasses

Copepod carcasses are prevalent in marine ecosystems and might represent an important component of the sinking flux of particulate organic carbon in the ocean. The extent to which copepod carcasses contribute to the biological carbon pump is controlled by different environmental factors, including temperature. However, the effect of temperature on the longer-term kinetics of carbon mineralization of copepod carcasses is not well-studied. We conducted laboratory experiments to quantify the carbon mineralization associated with sinking carcasses of the cosmopolitan copepod Acartia tonsa through aerobic microbial respiration at 5 temperatures (20, 16, 12, 8, and 4°C). Microbial respiration rates associated with the carcasses were positively correlated with temperature and characterized by an initial short lag-phase, a rapid increase to a maximum rate, and a subsequent gradual decline in the rate of degradation. On average, 50% of the total carbon of the carcasses was mineralized within 6-12 d at 20°C, versus >60 d at 4°C. During the incubations, most carbon mineralization occurred in the ambient seawater, likely fueled by dissolved organic carbon leaking from the carcasses into the surrounding seawater. Extrapolating measured carbon turnover and sinking rates suggests that at 20°C, the mineralization of sinking copepod carcasses is constrained to the surface ocean. In contrast, at 4°C, sinking copepod carcasses can reach the deep ocean before they have been completely degraded. Hence, in low-temperature regions, copepod carcasses may represent an important agent for carbon export through the biological carbon pump.

Mineralization Kinetics of Air Bubbles with Coarse Sphalerite Particles in Brackish Solutions of Sulfhydryl Collectors

Mineralization Kinetics of Air Bubbles with Coarse Sphalerite Particles in Brackish Solutions of Sulfhydryl Collectors

Unraveling Kinetic Effects during Photoelectrochemical Mineralization of Phenols. Rutile:Anatase TiO2 Nanotube Photoanodes under Thin-Layer Conditions

The kinetics of the photoelectrochemical mineralization of p-nitrophenol (PNP) and p-methoxyphenol (PMP) on rutile:anatase TiO2 nanotube electrodes (% rutile: 0, 16, and 20) has been studied. Oxida...

The kinetics curve of nitrogen mineralization from perennial leaves litter decomposed by earthworm (Phretima californica)

The kinetics of N release during the process of decomposition of organic matter is influenced by organic matter quality, temperature, humidity, and decomposer. Acacia, coffee, salacca, and bamboo leaf litter are native plants and be the pioneer plants on the slopes of Mount Merapi after the eruption in 2010. However, there is a lack of information on the N mineralization process from the leaves litter of acacia, coffee, salacca, and bamboo. The study aimed to determine the kinetics of N release from the litter leaves of acacia (<em>Acacia decurrens</em>), coffee, salacca, and bamboo, which were tested with three approaches, namely zero order, first order, and second order. The experiment was carried out using 10 <em>Phretima californica </em>earthworms that were incubated with 35g of annual plant leaves at 25°C. The levels of NH<sub>4</sub><sup>+</sup> and NO<sub>3</sub><sup>-</sup> were measured at 0, 7, 15, 30, 45, 75, and 105 days after incubation by using the indophenol blue and derivative spectrophotometric method, respectively. Throughout the decomposition 105 days, the release of NO<sub>3</sub><sup>-</sup> was higher than that of NH<sub>4</sub><sup>+</sup> due to the nature of NH<sub>4</sub><sup>+</sup> that was more easily immobilized than NO<sub>3</sub><sup>-</sup>. The highest NO<sub>3</sub><sup>- </sup>release in acacia litter (1.56 mg kg<sup>-1</sup>) occurred 30 days after incubation, while in coffee, salacca, and bamboo occurred 105 days after incubation, reaching 1.92 mg kg<sup>-1</sup>, 2.47 mg kg<sup>-1</sup>, and 1.88 mg kg<sup>-1</sup>, respectively. High N compound on the leaves litter unaffected to increasing total biomass earthworms in the end of incubation however promotes N mineralization rapidly. The kinetics of the second-order equation showed higher compatibility than the other equations to the N release with coefficient determination was higher. The kinetics of mineralization can be a strategy to use the leaves litter of perennial plants as sources of N nutrient input into soil.

Biomimetic Mineralization of Hierarchical Nanofiber Shish-Kebabs in a Concentrated Apatite-Forming Solution

Recently, hierarchical polymer nanostructures called nanofiber shish-kebabs (NFSKs) have shown great potential in directing the distribution of minerals for biomineralization. In this work, we report controlled biomimetic mineralization in block copolymer-containing NFSKs. NFSKs were formed by crystallizing polycaprolactone-block-poly(acrylic acid) (PCL-b-PAA) kebabs on PCL fiber backbones. The block copolymer kebabs were periodically distributed on PCL nanofibers with a spacing of ∼100–300 nm. Free ions could infiltrate into anionic PAA nanodomains and initiate the NFSK-templated biomimetic mineralization process. A concentrated calcium phosphate solution was used in the present study, which led to significantly accelerated mineralization kinetics compared with the previously studied simulated body fluid systems. Electron microscopy, Fourier-transform infrared spectroscopy, and wide-angle X-ray diffraction were used to characterize the structure and morphology of the mineralized NFSKs. A three-stage mineralization process was identified, and carbonated nonstoichiometric hydroxyapatite was observed after stage 2 with the mineral location templated within kebabs. This accelerated mineralization process yielded a periodic mineral distribution of a biomimetic calcium phosphate phase along the fibers, and the decrease in mineral formation time allows for more efficient biomineralization study and composite formation.

Effect of Temperature on Acetate Mineralization Kinetics and Microbial Community Composition in a Hydrocarbon-Affected Microbial Community During a Shift From Oxic to Sulfidogenic Conditions.

Aquifer thermal energy storage (ATES) allows for the seasonal storage and extraction of heat in the subsurface thus reducing reliance on fossil fuels and supporting decarbonization of the heating and cooling sector. However, the impacts of higher temperatures toward biodiversity and ecosystem services in the subsurface environment remain unclear. Here, we conducted a laboratory microcosm study comprising a hydrocarbon-degrading microbial community from a sulfidic hydrocarbon-contaminated aquifer spiked with 13C-labeled acetate and incubated at temperatures between 12 and 80°C to evaluate (i) the extent and rates of acetate mineralization and (ii) the resultant temperature-induced shifts in the microbial community structure. We observed biphasic mineralization curves at 12, 25, 38, and 45°C, arising from immediate and fast aerobic mineralization due to an initial oxygen exposure, followed by slower mineralization at sulfidogenic conditions. At 60°C and several replicates at 45°C, acetate was only aerobically mineralized. At 80°C, no mineralization was observed within 178 days. Rates of acetate mineralization coupled to sulfate reduction at 25 and 38°C were six times faster than at 12°C. Distinct microbial communities developed in oxic and strictly anoxic phases of mineralization as well as at different temperatures. Members of the Alphaproteobacteria were dominant in the oxic mineralization phase at 12–38°C, succeeded by a more diverse community in the anoxic phase composed of Deltaproteobacteria, Clostridia, Spirochaetia, Gammaproteobacteria and Anaerolinea, with varying abundances dependent on the temperature. In the oxic phases at 45 and 60°C, phylotypes affiliated to spore-forming Bacilli developed. In conclusion, temperatures up to 38°C allowed aerobic and anaerobic acetate mineralization albeit at varying rates, while mineralization occurred mainly aerobically between 45 and 60°C; thermophilic sulfate reducers being active at temperatures > 45°C were not detected. Hence, temperature may affect dissolved organic carbon mineralization rates in ATES while the variability in the microbial community composition during the transition from micro-oxic to sulfidogenic conditions highlights the crucial role of electron acceptor availability when combining ATES with bioremediation.

Kinetics of Soil Carbon Mineralization Under Continuous Site-Specific Nutrient Management in Ultisols Under Cassava

ABSTRACT The present study focused on the effect of 10 years of continuous fertilizer trials on soil organic carbon (SOC) mineralization in cassava grown ultisols. The study determines the carbon (C) mineralization potential, dynamics, and kinetics of C mineralization by fitting five decay models, significance of various long-term fertilizer applications on C mineralization and the relationship between soil physico-chemical properties with carbon mineralization parameters derived from the best model. To determine the potential of the soil to mineralize organic C a short-term aerobic incubation procedure – alkali trap method – was used. The best model fitting first-order E (R2 = 0.994) was used to describe the dynamics and kinetics of C mineralization. Relationships between soil physico-chemical properties and C mineralization parameters of first-order E model were studied by using correlation analysis. The site-specific nutrient management (SSNM) treatment showed the highest carbon dioxide-carbon (CO2-C) evolution value (2049.61 mg of CO2-C kg−1 soil) while NPK omission treatment showed the lowest (1703.37 mg of CO2-C kg−1 soil). The initial potential rate of carbon mineralization (C0k) was highest for SSNM treatment (159.78 mg kg−1) and lowest for K omission treatment (123.25 mg kg−1) indicating that the organic matter quality has increased in continuous SSNM treatment for 10 years compared to all other treatments. Significant positive correlations were shown between cumulative C evolved (Cm) and SOC. Significant negative correlations were observed between size of the mineralization flush (C1) and silt as well as between potentially mineralizable carbon (C0K) and clay.

Kinetics of C Mineralization of Biochars in Three Excessive Compost-Fertilized Soils: Effects of Feedstocks and Soil Properties

The aim of this work was to compare the carbon (C) mineralization kinetics of three biochars (Formosan ash (Fraxinus formosana Hayata), ash biochar; Makino bamboo (Phyllostachys makino Hayata), bamboo biochar; and lead tree (Leucaena leucocephala (Lam.) de. Wit), lead tree biochar) applied with two addition rates (2 and 5 wt %) in three excessive compost-fertilized (5 wt %) soils (one Oxisols and two Inceptisols), and to ascertain the increasing or decreasing effect of biochar and soil type in the presence of excessive compost. The study results of 400 days incubation indicated that, in general, the potential of the three biochars for C sequestration is similar in the three studied soils. The presence of excessive compost stimulated the co-mineralization of the more labile components of biochar over the short term (first two months). The potential of biochar addition for neutralizing soil pH and regulating the release of Al from soil for preserving soil organic carbon (SOC) might be the important mechanisms in biochar-compost interactions, especially in the presence of excessive compost. Overall, 5% application rate of three high temperature-pyrolysis biochars showed the less detriments to studied soils. In these incubations of biochar, excessive compost, and soil, it is a decreasing effect overall, that is, the enhanced storage of both biochar-C and SOC, which is expected as a long-term carbon sequestration in soil. The recorded direction and magnitude of effect, both are strongly influenced by biochar and soil type. When co-applied with excessive compost, the negative (reducing CO2 release) effect with increasing biochar application rates was eliminated.

Mineral density differences between femoral cortical bone and trabecular bone are not explained by turnover rate alone

Bone mineral density distributions (BMDDs) are a measurable property of bone tissues that depends strongly on bone remodelling and mineralisation processes. These processes can vary significantly in health and disease and across skeletal sites, so there is high interest in analysing these processes from experimental BMDDs. Here, we propose a rigorous hypothesis-testing approach based on a mathematical model of mineral heterogeneity in bone due to remodelling and mineralisation, to help explain differences observed between the BMDD of human femoral cortical bone and the BMDD of human trabecular bone. Recent BMDD measurements show that femoral cortical bone possesses a higher bone mineral density, but a similar mineral heterogeneity around the mean compared to trabecular bone. By combining this data with the mathematical model, we are able to test whether this difference in BMDD can be explained by (i) differences in turnover rate; (ii) differences in osteoclast resorption behaviour; and (iii) differences in mineralisation kinetics between the two bone types. We find that accounting only for differences in turnover rate is inconsistent with the fact that both BMDDs have a similar spread around the mean, and that accounting for differences in osteoclast resorption behaviour leads to biologically inconsistent bone remodelling patterns. We conclude that the kinetics of mineral accumulation in bone matrix must therefore be different in femoral cortical bone and trabecular bone. Although both cortical and trabecular bone are made up of lamellar bone, the different mineralisation kinetics in the two types of bone point towards more profound structural differences than usually assumed.

Modeling the Mineralization Kinetics of Visible Led Graphene Oxide/Titania Photocatalytic Ozonation of an Urban Wastewater Containing Pharmaceutical Compounds

In a water ozonation process, dissolved organics undergo two reactions at least: direct ozone attack and oxidation with hydroxyl radicals generated from the ozone decomposition. In the particular case of urban wastewater contaminated with pharmaceuticals, competition between these two reactions can be studied through application of gas–liquid reaction kinetics. However, there is a lack in literature about kinetic modeling of ozone processes in water specially in photocatalytic ozonation. In this work, lumped reactions of ozone and hydroxyl radicals with total organic carbon have been proposed. Urban wastewater containing a mixture of eight pharmaceutical compounds has been used to establish the kinetic model that simulates the mineralization process. The kinetic model is based on a mechanism of free radical and molecular reactions and the knowledge of mass transfer, chemical reaction rate constants, and radiation transfer data. According to the model, both single ozonation and photocatalytic ozonation present two distinct reaction periods characterized by the absence and presence of dissolved ozone. In the first period (less than 10 min), pharmaceuticals mainly disappear by direct ozone reactions and TOC variation due to these compounds has been modeled according to gas–liquid reaction kinetics through a lumped ozone-pharmaceutical TOC fast second order reaction. The corresponding rate constant of this reaction was found to change with time from 3 × 105 to 200 M−1 s−1 with Hatta values higher than 0.3. In the second period (nearly 5 h), competition between direct and hydroxyl radical reactions takes place and a kinetic model based on a direct and free radical reaction mechanism is proposed. Main influencing parameters to be known were: Direct ozone reaction rate constant, catalyst quantum yield, and hydroxyl radical scavengers. The first two take values of 0.5 M−1 s−1 and 5 × 10−4 mol·photon−1, respectively, while a fraction of TOC between 10% and 90% that changes with time was found to possess hydroxyl radical scavenger nature.

Valorizing biomass to engineered biochar and its impact on soil, plant, water, and microbial dynamics: a review

Till date there is not much concrete data available linking valorization of biomass-derived engineered biochar for soil, plant, water system, and microbial dynamics under changing climatic conditions. This review article deals with the abovementioned burning topic by collection of world literature. It summarizes the conversion of biomass into biochar, their characterization, and pyrolysis influence on composition. Besides it discusses about biomass through biochar which can help to establish a relationship with soil, plant, and water to manage soil fertility–related issues and microbe interactions. Biochar addition exerts measurable changes in carbon footprint, physicochemical and biological soil properties, nutrient sorption-retention, water retention, crop production, and nutrient leaching. Mechanistic evidences of biochars’ potential on soil biology, systemic resistance, carbon mineralization kinetics and N2-fixation, and mycorrhizal colonization were mentioned in this review article. The recalcitrance, pore space, surface morphology, and pH of biochar on soil, plant, water system, and microbes are found to be controlled by biomass type, pyrolysis temperature, biotic interactions, etc. Biochar with fertilizer integration offers an improved soil management strategy, and therefore, biomass valorization through its application in soil, plant, water, and microbial dynamics comes out as a “win-win strategy” for adequate climate change mitigation and environmental eco-friendly technology.

Electrochemical degradation of herbicide diuron on flow-through electrochemical reactor and CFD hydrodynamics simulation

An energy-efficient continuous flow-through electrochemical reactor (FT-ER) equipped with PbO2 filter anodes is designed and employed for electrochemical elimination towards herbicide diuron in the aquatic environment. Boosting performances, including substantially higher electrochemical mineralization kinetics and lower energy consumption, could be realized on the FT-ER compared with the traditional flow-by model. The effect of current density and flow rate on the degradation efficiency is also investigated. The glorious degradation kinetics could be ascribed to the large electrochemical surface area, strong generation power of reactive oxidants, and enhanced mass transfer process derived from the filter structure. Furthermore, we establish the computational fluid dynamics simulation to elucidate the dynamic flow behavior of the electrolyte, including fluid velocity and turbulent intensity distribution. The profound influence of FT-ER for the herbicide diuron removal stems from the homogenization of electrolyte flux and turbulence promoter of the filter structure. Finally, the continuous flow-through configuration exhibits excellent elimination performances, uniform fluid dynamics together with good stability. The filter anodes present a promising option for electrochemical treatment towards diverse organic pollutants in the aquatic environment and would be benefit to the evolution of cost-efficient electrochemical treatment techniques and reactors.