Phospholipid Bilayer Inspired Sandwich Structural Nanofibrous Membrane for Atmospheric Water Harvesting and Selective Release.

Atmospheric water harvesting (AWH) has been broadly exploited to meet the challenge of water shortage. Despite the significant achievements of AWH, the leakage of hydroscopic salt during the AWH process hinders its practical applications. Herein, inspired by the unique selective permeability of the phospholipid bilayer, a sandwich structural (hydrophobic-hydrophilic-hydrophobic) polyacrylonitrile nanofibrous membrane (San-PAN) was fabricated for AWH. The hydrophilic inner layer loaded with LiCl could capture water from the air. The hydrophobic microchannels in the outer layer could selectively allow the free transmission of gaseous water molecules but confine the hydroscopic salt solution in the hydrophilic layer, achieving continuous and recyclable water sorption/desorption. As demonstrated, the as-prepared AWH devices presented high-efficient adsorption kinetics from 1.66 to 4.08 g g-1 at 30% to 90% relative humidity. Thus, this work strengthens the understanding of the water transmission process along microchannels and provides insight into the practical applications of AWH.

Simulation and parameter determination of the net sorption of phenanthrene by sediment particles.

The distribution of polycyclic aromatic hydrocarbons (PAHs) in the ocean is affected by the sorption-desorption process of sediment particles. This process is determined by the concentration of PAHs in seawater, water temperature, and organic matter content of sediment particles. Quantitative relationships between the net sorption rates (=the difference of sorption and desorption rates) and these factors have not been established yet and used in PAH transport models. In this study, phenanthrene was chosen as the representative of PAHs. Three groups of experimental data were collected to address the dependence of the net sorption processes on the initial concentration, water temperature, and organic carbon content representing organic matter content. One-site and two-compartment mass-transfer models were tested to represent the experimental data using various parameters. The results showed that the two-compartment mass-transfer model performed better than the one-site mass-transfer model. The parameters of the two-compartment mass-transfer model include the sorption rate coefficients kafand kas (L g-1 min-1), and the desorption rate coefficients kdf and kds (min-1). The parameters at different temperatures and organic carbon contents were obtained by numerical simulations. Linear relationships were obtained between the parameters and water temperature, as well as organic carbon content. kaf, kas and kdf decreased linearly, while kds increased linearly with temperature. kaf, kas and kdf increased linearly, while kds decreased linearly with organic carbon content. The r2 values between the simulation results based on the relationships and the experimental results reached 0.96-0.99, which supports the application of the model to simulate sorption-desorption processes at different water temperatures and organic carbon contents in a realistic ocean.

Those That Remain Caught in the "Organic Matter Trap": Sorption/Desorption Study for Levelling the Fate of Selected Neonicotinoids.

With projections suggesting an increase in the global use of neonicotinoids, contemporary farmers can get caught on the "pesticide treadmill", thus creating ecosystem side effects. The aim of this study was to investigate the sorption/desorption behavior of acetamiprid, imidacloprid, and thiacloprid that controls their availability to other fate-determining processes and thus could be useful in leveling the risk these insecticides or their structural analogues pose to the environment, animals, and human health. Sorption/desorption isotherms in four soils with different organic matter (OC) content were modelled by nonlinear equilibrium models: Freundlich's, Langmuir's, and Temkin's. Sorption/desorption parameters obtained by Freundlich's model were correlated to soil physico-chemical characteristics. Even though the OC content had the dominant role in the sorption of the three insecticides, the role of its nature as well as the chemical structure of neonicotinoids cannot be discarded. Insecticides sorbed in the glassy OC phase will be poorly available unlike those in the rubbery regions. Imidacloprid will fill the sorption sites equally in the rubbery and glassy phases irrespective of its concentration. The sorption of thiacloprid at low concentrations and acetamiprid at high concentrations is controlled by hydrophilic aromatic structures, "trapping" the insecticides in the pores of the glassy phase of OC.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+ ) as charge balancing ions (named U-Squ-CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U-Squ-CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non-porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water-filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single-crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non-porous crystalline material.

[Study of the sorptiondesorption of ecdysterone (20 E) as part of adaptogenic compositions with inulin and functional food ingredients based on spinach and quinoa].

The main principle in the enrichment of food with minor bioactive compounds is the prediction and evaluation of possible chemical interactions of the components included in the matrix of the food. These interactions have a impact on the bioavailability of minor bioactive compounds. In our work, we studied the processes of sorption and desorption (release), the main processes affecting the bioavailability of the minor bioactive compound ecdysterone (20 E) in the composition of functional food ingredients obtained from spinach leaves (FFI-1) and quinoa grains (FFI-2) on hydrocolloid matrix - inulin. The objective of the research was to study the completeness of sorption-desorption processes of 20 E in adaptogenic compositions with inulin and functional food ingredients based on spinach and quinoa under the influence of hydrolytic enzymes of the gastrointestinal tract (GIT) in vitro. Material and methods. To obtain experimental compositions, containing FFI-1 and FFI-2 and the polysaccharide (inulin), a mechanical mixing method was used. To study the sorption properties, model solutions of the compositions were prepared. Using an in vitro enzymatic model, the ability of 20 E to be released from the matrix of the compositions was studied. The content of 20 E was determined by HPLC-MS/MS. Results. 6 compositions with different ratios of polysaccharide/FFI were obtained. At the first stage of the study, the maximum sorption of 20E in the model solution was observed for 4 compositions with the ratio of inulin : FFI = 2.50 or 3.75 g : 189.19 mg FFI-1 or 68.40 mg FFI-2. At the second stage of the study, when assessing the desorption of 20 E on the enzymatic GIT model, it was found that 20 E almost completely released only from 2 compositions, in other cases about 25% of 20 E remained in a bound state. Conclusion. The formulation of two compositions with the ratio of inulin (2.50 g) : FFI-1 (189.19 mg)/FFI-2 (68.40 mg) were obtained, which have the most optimal sorption / release parameters of 20 E under the influence of human gastrointestinal enzymes. These compositions can be considered promising for inclusion in the formulation of fortified foods.

Adsorption-desorption and transport behavior of pydiflumetofen in eight different types of soil.

Pydiflumetofen, a fungicide of the class of succinate dehydrogenase inhibitors, can disrupt energy metabolism by inhibiting the synthesis of succinate dehydrogenase, thus effectively inhibiting pathogenic fungal growth and related yield losses.We studied the adsorption and desorption behaviors and interaction mechanisms of pydiflumetofen in eight different arable soils by the infrared spectroscopy and batch equilibrium method. Pydiflumetofen adsorption and desorption property of soils conformed with the Freundlich isotherm model and the values for the adsorption capacity KF-ads were in the range of 14.592-102.610. The adsorption constants (KF-ads) exhibited a significantly positive and linear correlation (p < 0.1) with soil organic matter and organic carbon content. Both high and low temperatures weakened the pydiflumetofen sorption capacity of the soil. In addition, the initial pH of the solution, its ionic strength, and the addition of exogenous biochar, humic acid, and different types of surfactants at different concentrations also affected the sorption property of the soil. Pydiflumetofen is weakly mobile and leachable in most soils, and, poses some threat to surface soil and water organisms, but does not contaminate groundwater.

Performance of wild plants-derived biochar in the remediation of water contaminated with lead: sorption optimization, kinetics, equilibrium, thermodynamics and reusability studies.

This study aims to investigate the sorptive performance of Pb(II) from water of a novel biochar (WPC) produced by fast pyrolysis under anoxic conditions of wild plants (WP). The maximum Pb(II) sorption capacity of WPC is 50.25 mg/g under determined optimum conditions, which are solution pH 5.0, WPC dose 50 mg, contact time 180 min and solution temperature 50 °C. The sorption kinetics and isotherm data were observed to fit well with the Ho-McKay and Langmuir models, respectively. The thermodynamic parameters (ΔGo, ΔHo and ΔSo) calculated for the WPC-Pb(II) sorption system showed that the process was spontaneous and endothermic. The Pb(II) desorption and regeneration studies of WPC with different desorbent agents was also performed. The findings in this study showed that WP can be used as an abundant precursor in the production of very low cost and eco-friendly biochar, and also that its biochar can be used as an environmentally-friendly sorbent in wastewater treatment. Novelty statementWith increasing population and developing industry in the world, agriculture and industrial wastes are increasing. These wastes create environmental and water pollution and adversely affect the health of living things. Efforts to eliminate these negativities have a negative impact on the world economy. For this purpose, various improvement methods are applied. However, the adsorption method is widely used due to its ease of application, efficiency and economic. In order to make this method more economical, many researchers have carried out researches on the preparation of low-cost adsorbents, especially from vegetable wastes.The novelty of this study is the first reporting to use wild plants as a sustainable precursor to produce a low-cost biochar using the traditional pyrolysis method and to examine its adsorption performance for Pb(II) ion removal from water. I believe that if this study is published, it will create a paradigm in environmental improvement studies on wild plants evaluation.

Enhanced phosphorus mobility in a calcareous soil with organic amendments additions: Insights from a long term study with equal phosphorus input.

The agricultural practice of replacing chemical fertilizers with organic amendments (manure and/or straw) may have consequences for phosphorus (P) loss to the environment. Such a knowledge gap was examined using a ten-year field trial in calcareous soil containing four treatments with the equal annual P input but varied organic amendment combinations as follows: mineral fertilizer only as control (MF), mineral fertilizer coupled with manure (MM), mineral fertilizer coupled with manure and straw (MMS) and mineral fertilizer coupled with straw (MS). The soil P distribution, P fractions and speciation, Fe(III) reduction and P sorption kinetics were investigated using the chemical extraction, K edge X-ray absorption near-edge structure and Langmuir equations. The electronic shuttle capacity of soils and speciation of soil dissolved organic matter (DOM) were also evaluated using electrochemical methods, three-dimensional excitation-emission matrix fluorescence spectroscopy and Fourier transform infrared spectra methods. Results showed that soil Olsen-P and total P increased at depths of 20-40 cm in MM, MMS and MS treatments, suggesting that manure and/or straw addition significantly mobilized P in the soil profile. Manure and/or straw addition also decreased soil maximum P sorption capacity (Smax) and increased the desorption rate at depths of 0-20 cm in soil across treatments. At a depth of 0-20 cm in soil of the MS treatment, the enhanced Fe(Ⅲ) reduction coupled with a decrease of Fe-bound P supports that Fe reduction dominates the mobilization of P. The transformation of Ca bound-P to Al/Fe bound-P in a depth of 0-20 cm in soil of the MM treatment may be due to the high proportion of humic-like substances in the DOM at a depth of 0-20 cm in soil of the MM treatment, which may have caused a slight/microsite acidification. These results can help to develop optimized fertilization practices to effectively mitigate P loss from calcareous soils with manure and/or straw addition.

The Kinetics of Sorption-Desorption Phenomena: Local and Non-Local Kinetic Equations.

The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.

Investigation of differential levels of phosphorus fixation in dolomite and calcium carbonate amended red soil.

BACKGROUND: The pH adjustment of acidic red soils with lime materials is beneficial for the reduction of phosphorus (P) fixation. However, the reasons for varying levels of P activation after adding different lime materials have not been fully investigated. Therefore, this study examined changes in soil labile P and P forms after phosphate application to calcium carbonate (CaCO3 ) and dolomite amended red soil during a 120-day incubation period. Also change of P sorption properties in the amended soil samples from day 120 were examined through a sorption-desorption experiment. RESULTS: The increase of soil H2 O-P and NaHCO3 -P in the CaCO3 and dolomite amended soil treatments was mainly ascribed to the decline of the NaOH-P. However, when compared with the control treatment after 120 days, soil Olsen-P significantly increased by 34% and 66% in the CaCO3 and dolomite treatments. The Hedley P fractionation results demonstrated that the CaCO3 application caused a notable increase of HCl-P (stable Ca-P), which was 88.4% higher than that in the dolomite treatment. However, the formation of stable P was strongly suppressed in the dolomite treatment due to the presence of magnesium (Mg), which was identified by the negative relationship between M3-Mg and HCl-P. In line with these findings, P sorption-desorption work showed weaker P binding energy in the dolomite treatment relative to the CaCO3 treatment. CONCLUSION: In terms of increasing P availability in red soil, this study suggests that dolomite should be used to substitute CaCO3 in order to reduce the soil P fixation. © 2021 Society of Chemical Industry.

Glyphosate use in urban landscape soils: Fate, distribution, and potential human and environmental health risks.

This novel study investigated the fate and distribution in soils, and potential exposure risk of glyphosate, an extensively used herbicide in urban landscapes. The rate-determining step of glyphosate sorption in urban soils involved chemisorption processes through exchange or sharing of electrons that followed the pseudo-second-order kinetics model. As evidenced by the Freundlich isotherm model, glyphosate gets partitioned into heterogeneous surfaces of soil organic matter (OM) and clay minerals, and then diffused into soil micropores. The principal component analysis revealed that soil OM (R2 = 0.873), oxides of Al (R2 = 0.361) and Fe (R2 = 0.126), and contents of clay (R2 = 0.061) and silt (R2 = 0.432) were positively correlated with the distribution coefficient (Kd) of glyphosate, while alkaline pH (R2 = -0.389) and sand content (R2 = -0.343) negatively correlated with the Kd values. Well-decomposed soil OM, consisting of C-H and CO functional groups, enhanced glyphosate sorption, whereas partially decomposed/undecomposed OM facilitated desorption process. Desorption of glyphosate was favoured in seven of nine selected soils due to adverse hysteresis effects (HI = 0.74-1.0). The higher values of leachability index (0.31-1.0) and groundwater ubiquity score (1.60-3.44) calculated for the urban soils indicated the great leaching potential of glyphosate from soil surface to waterbodies. Use of glyphosate on impermeable surfaces might directly contaminate water sources and affect potability of water, non-target biota, and food safety. The calculated values of cancer risk (10-8‒10-12) and hazard quotient (1.47 × 10-6‒4.12 × 10-6) suggested that the human exposure to glyphosate-contaminated soils through dermal, ingestion and inhalation pathways might cause negligible or no carcinogenic and non-carcinogenic risks to humans. Therefore, glyphosate should be applied judiciously at recommended concentrations in the urban landscapes, mainly on impervious surfaces, to minimize its health impacts in humans and environment.

A novel arsenic immobilization strategy via a two-step process: Arsenic concentration from dilute solution using schwertmannite and immobilization in Ca-Fe-AsO4 compounds.

Acid mine drainage (AMD) with toxic arsenic (As) is commonly generated from the tailings storage facilities (TSFs) of sulfide mines due to the presence of As-bearing sulfide minerals (e.g., arsenopyrite, realgar, orpiment, etc.). To suppress As contamination to the nearby environments, As immobilization by Ca-Fe-AsO4 compounds is considered one of the most promising techniques; however, this technique is only applicable when As concentration is high enough (>1 g/L). To immobilize As from wastewater with low As concentration (~10 mg/L), this study investigated a two-step process consisting of concentration of dilute As solution by sorption/desorption using schwertmannite (Fe8O8(OH)8-2x(SO4)x; where (1 ≤ x ≤ 1.75)) and formation of Ca-Fe-AsO4 compounds. Arsenic sorption tests indicated that As(V) was well adsorbed onto schwertmannite at pH 3 (Qmax = 116.3 mg/g), but its sorption was limited at pH 13 (Qmax = 16.1 mg/g). A dilute As solution (~11.2 mg/L As) could be concentrated by sorption with large volume of dilute As solution at pH 3 followed by desorption with small volume of eluent of which pH was 13. The formation of Ca-Fe-AsO4 compounds from As concentrate solution (2 g/L As(V)) was strongly affected by temperature and pH. At low temperature (25-50 °C), amorphous ferric arsenate was formed, while at high temperature (95 °C), yukonite (Ca2Fe3-5(AsO4)3(OH)4-10·xH2O; where x = 2-11) and johnbaumite (Ca5(AsO4)3OH) were formed at pH 8 and 12, respectively. Among the synthesized products, johnbaumite showed strongest As retention ability even under acidic (pH < 2) and alkaline (pH > 9) conditions.

Sorption behavior of dimethyl phthalate in biochar-soil composites: Implications for the transport of phthalate esters in long-term biochar amended soils.

The characteristics and content of organo-mineral complex were confirmed to be changed in agriculture soils under the biochar application with long-term, but the resulting environmental effects in the retention and lasting of agrochemicals and xenobiotic pollutants is far from clear. In this study, biochar-soil composites were prepared by one-step dry ball-milling method, and a sorption case study was proceed to investigate the biochar incorporated affection in soils on the transport of dimethyl phthalate (DMP). More surface oxygen-containing functional groups on ball-milled biochar enhanced its complexation with soil minerals. Sorption isotherms of DMP onto the biochar-soil composites were well described by the Freundlich model, both heterogeneous surface and multilayer interactions occurred simultaneously. The kinetics of sorption could be simulated with the pseudo-second-order model (R2 > 0.98), while the average sorption energy (Ea) calculated from Dubinin-Radushkevich isotherms were found in the range of 3.83-5.60 kJ mol-1, which revealed that the sorption processes coexist of chemisorption and physisorption, and π-π electron donor-acceptor interaction, pore-filling and hydrophobic interactions could be identified as the main sorption mechanisms. Desorption of absorbed DMP appeared obvious nonlinear characteristics and lag effect, the calculated hysteresis index (HI) increased with the application of biochar into soil. Considering the phenomenon of biochar aging and soil complexation, it is important to verify how the transport and natural attenuation of contaminant will be influenced by biochar addition, especially the long-term effect in soil ecosystem.

Remediation of chromium and mercury polluted calcareous soils using nanoparticles: Sorption -desorption kinetics, speciation and fractionation.

Stabilization is an emerging technology for the cost-effective remediation of heavy metals polluted soils. To evaluate the potential of water treatment residual nanoparticles (nWTR) in reducing Hg and Cr mobility in contaminated calcareous soil, sorption-desorption kinetics; speciation and fractionation experiments were performed. Application of nWTR strongly enhanced Cr and Hg sorbed in the calcareous soil, whereas the released amount of both metals through 6 successive desorption steps dramatically decreased. The power function model best described the desorption kinetic data of Cr and Hg from nWTR amended and non-amended calcareous soil. Fractionation experiment data demonstrated that nWTR amendment significantly increased metals concentration in the residual fraction (RS) and simultaneously decreased the more accessible forms of Hg and Cr. Addition of nWTR at a rate of 0.3% to the contaminated calcareous soil significantly increased Hg and Cr in the RS fraction from 69.27% and52.62% to 93.89% and 90.05% respectively. Additionally, the formation of stable Hg and Cr species such as Hg(OH)2 amor, CrSO4. xH2O and Cr(OH)2) were increased as a result of nWTR application. These findings jointly indicate the enhancement of Hg and Cr immobilization in the nWTR amended calcareous soil. FTIR spectroscopy analysis indicated the contribution of OH group and Al-O-Si of nWTR in Hg and Cr sorption process and suggests chemo-sorption reaction between both metals and the nWTR surface functional groups. Overall, the final results confirm the strong capability of nWTR application in reducing Hg and Cr risks in highly contaminated sites of the calcareous soil.

Spontaneous Cr(VI) and Cd(II) biosorption potential of native pinnae tissue of Pteris vittata L., a tropical invasive pteridophyte.

Heavy metal pollution is a prevalent and critical environmental concern. Its rampancy is attributed to indiscriminate anthropogenic activities. Several technologies including biosorption have been continuously researched upon to overcome the limitations of the conventional method of treatments in removal of heavy metals. Biosorption technology involves the application of a biomass in its nonliving form. Pteris vittata L., a pteridophyte, considered as an invasive weed was investigated in the present study as a potential decontaminant of toxic metals, Cr(VI) and Cd(II). The adsorption capacity of the biosorbent for Cr(VI) and Cd(II) under equilibrium conditions was investigated. The morphology, elemental composition, functional groups, and thermal stability of the biosorbent before and after metal loading were evaluated. At 303 K and an equilibrium time of 120 min, the maximum loading of Cr(VI) on the biosorbent was estimated to be 166.7 mg/g at pH 2 and Cd(II) to be 31.3 mg/g at pH 6. Isotherm models, kinetic studies, and thermodynamic studies indicated the mechanisms, chemisorption, ion exchange and intraparticle diffusion, controlling the Cr(VI) and Cd(II) uptake, respectively. The interactive effect of multi-metal ions in binary component systems was synergistic for Cd(II) uptake. The results validate the toxic metal removal potency of the biosorbent.

The Thermodynamics of Trichocyte Keratins.

This chapter is an attempt at an excursion into the world of keratins with the help of thermodynamics.After briefly introducing some of the thermodynamic concepts involved in deciphering the behaviour of keratins, we will use them to look into the process of aggregation of keratin molecules into intermediate filaments, and keratin fibres, and then for analysing how keratin materials react to mechanical, thermal and moisture stresses, respectively.In most of the cases entropy appears to be the major driving force of the response occurring in keratins under environmental assault. This fact points to the important role played for keratins by temperature, which, aside from influencing the kinetics of the processes (accelerating or decelerating the rates of the rates), helps increase or decrease the entropic contribution to the Gibbs free energy and, thus, allows thermodynamically the occurrence of the observed behaviour of keratins.

Sorption-desorption test for functional assessment of skin treated with a lipid system that mimics epidermal lamellar bodies.

BACKGROUND: Many skin diseases are associated with either increases or decreases in lamellar body secretion, or dysfunctional lamellar bodies. Consequently, diseased skin is characterized by reduced barrier function and altered lipid composition and organization. Human skin is commonly evaluated in vivo with non-invasive biophysical techniques. The dynamic functions of the skin are evaluated with repeat measurements such as the sorption-desorption test (SDT). OBJECTIVES: The aim of this study was to evaluate in vivo skin hydration-dehydration kinetics after treatment with a lipid system that mimics the morphology, structure and composition of lamellar bodies in both healthy and irritated human skin. METHODS: A patch with an aqueous solution of 2% sodium lauryl sulfate (SLS) was used to irritate the skin of the volunteers. The SDT was performed with the CM 820 corneometer. RESULTS: After treatment with this system, both healthy and SLS-irritated skin increased their ability to retain water and to release water slowly during the desorption phase. CONCLUSIONS: Treatment with this system seems to reinforce the barrier function in both healthy and SLS-irritated human skin. Therefore, the present study provides evidence that this system could be of interest for developing future treatments for protecting and repairing the skin.

New Insights into Solid Form Stability and Hydrate Formation: o-Phenanthroline HCl and Neocuproine HCl.

The moisture- and temperature dependent stabilities and interrelation pathways of the practically relevant solid forms of o-phenanthroline HCl (1) and neocuproine HCl (2) were investigated using thermal analytical techniques (HSM, DSC and TGA) and gravimetric moisture sorption/desorption studies. The experimental stability data were correlated with the structural changes observed upon dehydration and the pairwise interaction and lattice energies calculated. For 1 the monohydrate was identified as the only stable form under conditions of RH typically found during production and storage, but at RH values >80% deliquescence occurs. The second compound, 2, forms an anhydrate and two different hydrates, mono- (2-Hy1) and trihydrate (2-Hy3). The 2-Hy1 structure was solved from SCXRD data and the anhydrate structure derived from a combination of PXRD and CSP. Depending on the environmental conditions (moisture) either 2-Hy1 or 2-Hy3 is the most sable solid form of 2 at RT. The monohydrates 1-Hy1 and 2-Hy1 show a high enthalpic stabilization (≥20 kJ mol-1) relative to the anhydrates. The anhydrates are unstable at ambient conditions and readily transform to the monohydrates even in the presence of traces of moisture. This study demonstrates how the right combination of experiment and theory can unravel the properties and interconversion pathways of solid forms.

Structural Properties, Order-Disorder Phenomena, and Phase Stability of Orotic Acid Crystal Forms.

Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1), and dimethyl sulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape, and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135 °C and loses only a small part of the water when stored over desiccants (25 °C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader, indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a nonlayer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions, different levels of order-disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration.

Effects of two different organic amendments addition to soil on sorption-desorption, leaching, bioavailability of penconazole and the growth of wheat (Triticum aestivum L.).

This study investigated the effects of sugarcane bagasse compost (SBC) and chicken manure compost (CMC) on the sorption-desorption, leaching and bioavailability of the fungicide penconazole in soil in a laboratory setting. The autoclave-treated SBC or CMC was applied at 2.5% and 5.0% (w/w). Results of batch equilibrium experiments exhibited that the sorption capacity of soils for penconazole was significantly promoted by the addition of SBC or CMC, whereas desorption of penconazole was drastically reduced; the influence was enhanced as the amount of organic amendments increased. Results of column leaching experiment indicated that the addition of SBC or CMC significantly limited the vertical movement of penconazole through the soil columns, considerably decreasing the content of penconazole in the soil leachate. Furthermore, results of bioavailability experiments demonstrated that the addition of organic amendments (SBC or CMC) remarkably influenced the uptake and translocation of penconazole, decreased penconazole accumulation in the plant tissues and increased the plant elongation and biomass. These data revealed important changes in pesticide behavior under SBC or CMC application, which should be useful for developing strategies to protect groundwater and crops from contamination from the residual pesticides in soil.