Aqueous Phosphate Solutions Research Articles

Adsorption Mechanism for Phosphate in Aqueous Solutions of Calcium/Aluminum-rich Sludge Biochar Composite

Excess sludge is rich in organic matter but also contains heavy metals, pathogens, and harmful substances. In this study, hydroaluminite and excess sludge were used as raw materials to reduce the risk of heavy metals leaching from sludge by coagulation and co-pyrolysis, and its phosphate adsorption characteristics were studied. The results showed that the leaching amount of Zn, Cu, Cd, and Ni in sludge biochar decreased with the increase in the hydroaluminite dosage. The sludge biochar composite (1:1HB800), prepared by co-pyrolysis of hydroaluminite and excess sludge with a mass ratio of 1:1 as well as rich in calcium and aluminum, had lowest leaching risk of heavy metals and showed the high adsorption capacity for phosphate. The process could be fitted by the Langmuir adsorption isotherm (R2=0.93), and the maximum phosphate adsorption capacity at 25℃ was 51.38 mg·g-1. The pseudo second-order kinetic model could well describe the adsorption process of 1:1HB800 for high concentration phosphate, and its adsorption rate was controlled by both surface adsorption and particle diffusion. Compared with that in the neutral solution, 1:1HB800 had better phosphate capacity in the acidic and alkaline aqueous solutions, which was related to the leaching amount of calcium/aluminum in 1:1HB800 and the existence form of aluminum under the different pH conditions. FTIR, XRD, SEM, zero potential point, and Ca2+/Al3+ leaching experiments indicated that the main adsorption mechanisms for phosphate by 1:1HB800 were co-precipitation (interaction between Ca2+/Al3+ and phosphate), ligand exchange (hydroxyl), and electrostatic interaction. Therefore, 1:1HB800 can provide a feasible alternative for the removal of phosphate in aqueous solutions and also provide a potential new method for the resource utilization and harmless treatment of excess sludge.

Enhancement of surface properties of cementitious materials by phosphate treatments

This study aims at investigating the ability of aqueous phosphate solutions to improve the surface properties of cement pastes via the formation of low-solubility calcium phosphate (CaP) phases. Diammonium hydrogen phosphate (DAP), dipotassium hydrogen phosphate (DPP) and disodium hydrogen phosphate (DSP) were investigated based on thermodynamic modeling and experiments. For DPP, the influence of concentration and cement age was evaluated. A 1 M DPP + 1 mM CaCl2 solution applied to cement hydrated for 7 days was most promising. The CaP coating formed after 24 h of exposure resulted in significant improvements in the cement pastes' resistance to abrasion, surface indentation and staining. Preliminary durability tests by immersion in water were successfully carried out to ascertain that no efflorescence due to soluble salts appeared and that mechanical improvement was retained. Compared to DAP, DPP has the advantage of not releasing NH3 into the atmosphere, thus preventing unpleasant odor and improving the treatment's environmental sustainability.

Observation of the phase-separation multiphase flow using a polyethylene glycol/phosphate mixed solutions and the aqueous two-phase distribution of red blood cells in the flow system.

Phase-separation multiphase flow at a liquid-liquid interface was successfully formed in an aqueous two-phase system of polyethylene glycol/phosphate mixed solutions when fed into a microchannel (100µm wide and 40µm deep) on a microchip and a fused-silica capillary tube (100µm ID). As one example, tube radial distribution flow (annular flow) was observed when 10.0 wt% polyethylene glycol 6000 and 8.5 wt% dipotassium hydrogen phosphate aqueous solution containing 1.0mM Rhodamine B was fed at 40℃, recorded by bright field microscopy. It exhibited a dipotassium hydrogen phosphate-rich inner phase and polyethylene glycol-rich outer phase. Effects of conditions including composition, flow rate, viscosity, and contact angle on tube radial distribution flow were analyzed. It was found out that although the viscosity of PEG-rich solution was much higher than that of phosphate-rich one, the phase configuration in tube radial distribution flow did not necessarily obey the viscous dissipation law in untreated microchannel and capillary tube, as well as for all the types of PEG/phosphate mixed solution the PEG-rich solution occupied the outer phase near the ODS-treated inner wall of both microchannel and capillary tube against the law. To assess the use of microfluidic flow in applications, we examined the distribution of red blood cells in the inner and outer phases fed into double capillary tubes with different inner diameters. Cell distribution was found to concentrate in the inner (dipotassium hydrogen phosphate-rich) phase compared to the outer (polyethylene glycol-rich) phase at a ratio of 1.8.

Multiresidue chromatographic method for the determination of antibiotic residues in honey by high-performance liquid chromatography with DAD detection

Clandestinely, consumers may be exposed to antibiotic (ATB) residues in honey, which could pose a health concern. For the first time, the simultaneous determination of Florfenicol (FF), Penicillin G (PG), and Tetracycline is described in this paper. The multiresidual method was developed and optimized using high-performance liquid chromatography (HPLC) coupled to a diode array detector (DAD). These ATBs were separated on a C18 analytical column after a cleanup process followed by solid-phase extraction (SPE). For the first time, the chromatographic conditions were perfected. After the method validation process, the method was used to assess ATB residues in four Lebanese honey samples. ATBs were separated in less than 15 min with an isocratic elution using a mixture of 80 % potassium dihydrogen phosphate aqueous solution, and 20 % acetonitrile. The UV detection was performed at 350 nm for TC, 224 nm for FF, and 230 nm for PG. The proposed method was linear (R2 ≥ 0.996) within the concentration ranges of 0.7-17.5 mg.Kg 1 for the three compounds. Both intra- and inter-day precision, expressed as RSD, were ≤15 %. The method was subsequently successfully applied to analyze examined ATB residues in honey samples collected from Lebanese beekeeping. The method described could be a valuable tool to conduct a comprehensive survey of honey samples produced in Lebanon, especially in the lack of serious national oversight.

Laboratory and Bench Methodology to Test Fire Suppressant Effectiveness in Aviation Method of Extinguishing of Forest Fires

Laboratory and bench tests for evaluation of fire retaining and fire extinguishing properties of agents used for fighting forest fires are described. The methodology gives not only a possibility to understand the effectiveness of the agents themselves but also to determine the characteristics of their discharge from an aircraft, in particular, the length and width of the wetted strip, the irrigation density and the flight altitude. Laboratory experiments confirm high fire retaining efficiency of aqueous solutions of magnesium halides and diammonium phosphate which cause significant delay in ignition time and substantial increase in ignition temperature for wood treated with these solutions. The efficiency of the halides significantly increases in the row MgCl2 < MgBr2 < MgI2. It was also shown by the experiments that the irrigation density by aqueous solutions necessary to extinguish grassroots and crown forest fires decreases when using Firex wetting agent and increases for bischofite and bentonite.

Mechanochemically activated microscale zero-valent iron with carboxymethylcellulose for efficient sequestration of phosphate in aqueous solution

This study modified microscale zero valent iron (mZVI) using hydrophilic sodium carboxymethyl cellulose (CMC) via mechanical ball milling method, which was donated as CMC-mZVI, and compared the phosphate removal performance of mZVI and CMC-mZVI. Characterization results of X-ray powder diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), EDS-mapping images of CMC-mZVI demonstrated that the dominant crystalline structure of mZVI did not alter significantly after the ball-milling process and CMC could be adsorbed on the surface of mZVI. Further phosphate (PO43-) removal experimental results revealed that the PO43- removal percentage of CMC-mZVI within 360 min was 99.99 %, which was much higher than that of mZVI (75.23 %). Subsequently, this study analyzed the concentration of ferrous ions and total iron ions dissolved by mZVI and CMC-mZVI, compared the high resolution X-ray photoelectron spectroscopy (HR-XPS) of mZVI and CMC-mZVI before and after the phosphate removal, and characterized the affinity of CMC-mZVI (or mZVI) to water by testing the static contact angle between CMC-mZVI (or mZVI) and water. The above results suggested that the existence of CMC on the surface of mZVI could promote the hydrophilic property of mZVI, resulting the enhancement of ferrous ions and total iron ions dissolution by 8 and 8.78 times than that of mZVI, and the rapid co-precipitation of phosphate. This study provided an environmentally friendly and effective method to improve the reactivity of commercial mZVI powder, and contributed to the wide application of mZVI technology in the field of environmental remediation.

Conservation of Archaeological Bones: Assessment of Innovative Phosphate Consolidants in Comparison with Paraloid B72.

Aqueous solutions of diammonium hydrogen phosphate (DAP) have been recently proposed for consolidation of archeological bones, as an alternative to traditional products. Here, we investigated several routes to improve the performance of the DAP-based treatment, namely increasing the DAP concentration, adding calcium ions and adding ethanol to the DAP solution. Archaeological bones dated to about 1–0.8 million years ago were used for the tests. After preliminary screening by FTIR microscopy and FEG-SEM among different formulations, confirming the formation of new hydroxyapatite phases, the most promising formulation was selected, namely a 3 M DAP solution. The strengthening ability of this formulation was systematically compared to that of the most widely used commercial consolidant, namely Paraloid B72. The performance of the two treatments was evaluated in terms of Knoop and Vickers microhardness, resistance to scratch and resistance to material loss by peeling off. The results of the study show that the DAP treatment was able to improve the bone surface properties and also the resistance to material loss by peeling off, which is more dependent on in-depth consolidation. Paraloid B72 led to the formation of a layer of acrylic resin on the bone surface, which influenced the mechanical tests. Nonetheless, Paraloid B72 was able to penetrate in depth and substantially decrease the material loss by peeling off, even more effectively than DAP. The results of this study indicate that the potential of the DAP treatment for bone consolidation is confirmed.

Tailoring the photoluminescence of capmatinib towards a novel ultrasensitive spectrofluorimetric and HPLC-DAD monitoring in human serum; investigation of the greenness characteristics

This work reports for the first spectrofluorimetric investigation of the INC280, Capmatinib (CAPM). The photophysical characteristics of CAPM especially fluorescence was extensively studied. CAPM has a native green fluorescence at λem = 500 nm with λex = 250 nm, that could be influenced and optimized under various experimental conditions of solvents, pH, temperature and inclusion matrices. Generally, protic polar alcoholic solvents are the best solvents in sensitizing CAPM emission. Furthermore, addition of disodium hydrogen phosphate aqueous solution of pH 6 at 25 °C reveals the highest fluorescence intensity of CAPM. Sodium dodecyl sulfate (SDS) when added to CAPM in optimized concentration results in 81.4 % enhancement in the CAPM fluorescence signal which impacted an improved sensitivity in the fluorimetric assaying of CAPM. HPLC-DAD method was also applied for determination of cited drug. Native spectrofluorimetry and HPLC-DAD of CAPM exhibits wide linear dynamic range from 0.015 to 2.0 µg/ mL and 0.02–100 µg/ mL within limits of detection of 0.0038 and 0.0039 µg/ mL, respectively. Moreover, the two methods are of high accuracy and precision that reveal estimates of 93.16–100.91 % and 96.67–100.42 % for recovery % while the corresponding estimates of RSD% ranges from 0.926 to 2.668 % and 0.505–1.571 %. The two methods were validated with successful applicability in the assaying of spiked CAPM in human serum samples. Greenness characteristics for both spectroflourimetric and HPLC-DAD methods were assessed using AGREE and GAPI approaches.

Bilastine: stability-indicating a method using environmentally friendly by reversed-phase high-performance liquid chromatography (RP-HPLC)

This study describes the development and validation of a new environmentally friendly analytical method for the determination of bilastine in coated tablets and the evaluation of its capacity to be stability-indicating as well. The ecofriendly analytical method was validated by specificity, linearity, accuracy, precision and robustness by reversed-phase high-performance liquid chromatography (RP-HPLC) according to International Conference on Harmonization guidelines (ICH) and Association of Official Analytical Chemists (AOAC). Isocratic LC separation was achieved on a RP18 column using a mobile phase of sodium dihydrogen phosphate aqueous buffer solution adjusted to pH (6.0 ± 0.1) with o-phosphoric acid (85% v/v) and triethylamine (0,3% v/v) and ethanol (EtOH) in the following proportions (60:40 v/v), at a flow rate of 1.0 mL·min-1 at temperature-controlled at 30 °C. The analytical method showed selectivity, good recovery and precision (intra- and inter-day), robustness, and linear over a range from 5.0 to 50 μg·mL-1.

(Digital Presentation) Enhanced Electrochemical Phosphate Recovery from Wastewater: Implications of Pulsating Anode Potential

Electrochemical recovery of phosphorus (P) as struvite (or magnesium ammonium phosphate hexahydrate, MgNH4PO4.6H2O) fertilizer using a sacrificial pure magnesium (Mg) anode is considered a sustainable strategy to deal with the limited availability of rock phosphate. However, the formation of an electrically passive film of magnesium hydroxide (Mg(OH)2) and/or struvite on the surface of Mg upon immediate immersion in aqueous phosphate solution limits the release of divalent Mg ions and decreases struvite precipitation. The present work highlights struvite recovery by an electrochemical method upon application of a dynamic voltage with a sinusoidal waveform. Our results demonstrate that a dynamic potential, when compared to a constant potential, can enhance the rupture of the passivating film, and facilitate the release of Mg2+ from the metal thereby overcoming the problems related to electrical passivation.Aqueous solutions of ammonium dihydrogen phosphate (NH4H2PO4, 10 mM) at neutral pH were used as test solutions. Mg2+ release was notably increased by ~48% relative to constant voltage applications, which subsequently led to ~20% higher phosphate recovery. Characterization studies including X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the presence of struvite in the recovered precipitate. Surface characterization of electrodes using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) also confirms a higher extent of passivating film breakdown in the presence of dynamic voltage.

Development of a standardized in vitro model to reproduce hydrophilic acrylic intraocular lens calcification

Opacification through calcification of hydrophilic acrylic intraocular lenses (IOL) is a severe complication after cataract surgery. Causing symptoms that range from glare through to severe vision loss, the only effective therapy is explantation of the opacified IOL so far. Although IOL calcification is a well-described phenomenon, its pathogenesis is not fully understood yet. The purpose of the current study was to develop a laboratory model to replicate IOL calcification. Calcification could be reproduced using a horizontal electrophoresis and aqueous solutions of calcium chloride and disodium hydrogen phosphate. The analysis of the in vitro calcified IOLs was performed using light microscopy, Alizarin Red and Von Kossa staining, scanning electron microscopy, energy dispersive x-ray spectroscopy and electron crystallography using transmission electron microscopy and electron diffraction. The presented laboratory model could be used to identify hydrophilic IOLs that are at risk to develop calcification and to assess the influence of associated risk factors. In addition, it can serve as a research tool to further understand this pathology.

Study of the interactions of monosaccharides D(+)-glucose and D(−)-fructose in aqueous diammonium hydrogen phosphate over the temperature range T=(288.15–318.15) K

The interactions of monosaccharides D(+)-glucose and D(−)-fructose in aqueous solutions of diammonium hydrogen phosphate (DAP) as a function of temperature have been investigated. The values of densities and speeds of sound have been measured for the system of monosaccharides and salt in aqueous solution. Densities and speed of sound for D(+)-glucose and D(−)-fructose in (0.5, 1.0, 1.5 and 2.0) mol⋅kg−1 aqueous solutions of diammonium hydrogen phosphate (DAP) are measured at T = (288.15, 298.15, 308.15 and 318.15) K and experimental pressure p = 0.1 MPa. The apparent molar volume,Vφ the partial molar volume, VφO and standard partial molar volumes of transfer, Δ VφO for D(+)-glucose and D(−)-fructose in aqueous solutions of diammonium hydrogen phosphate (DAP) have been calculated from density data. Apparent molar isentropic compression,Kϕ,s partial molar isentropic compression, Kϕ,so and partial molar isentropic compression of transfer, ΔKϕ,so have been calculated from speed of sound measurements. The expansibility parameter (∂Vϕ0 /∂T)p and its derivative (∂2 Vϕ0 /∂2 T)p along with pair (VAB, KAB) and triplet (VABB, KABB) interaction coefficients have also been calculated. The results have been interpreted in terms of solute − solute and solute–solvent interactions prevailing in these ternary systems.

Evaluation of butyric acid as a potential supportive treatment in anterior uveitis

Background: The aim of the study was to evaluate the anti-inflammatory effect of topically administered aqueous sodium butyrate solution in an endotoxin-induced uveitis rat model and compare the results with corticosteroid treatment. Material and methods: Forty female Lewis rats were randomly divided into five groups. Uveitis was induced by a single lipopolysaccharide (LPS) injection into each footpad of each LPS+ rat. Group I (naive) received saline injected into the footpad of each rat at a dose of 0.1 mL/each footpad; Group II (LPS+) received saline solution topically. Group III (LPS+ Dex) — an aqueous dexamethasone sodium phosphate solution topically; Group IV (LPS+ But 0.5 mM) — 0.5 mM aqueous sodium butyrate solution topically, Group V (LPS+ But 1 mM) — 1.0 mM aqueous sodium butyrate solution topically. Clinical scoring of inflammation in rat eyes was evaluated before LPS injection and after 24 hours. The iris involvement, posterior synechiae presence, and insight into the eye fundus were clinicallyassessed. A histopathological examination was also performed. The rats were euthanatized 24 hours after LPS injection, and aqueous humor (AqH) was collected from the eyes by anterior chamber puncture. Levels of inflammatory cytokines and chemokines in the AqH were determined with commercially available Luminex assays. Results: Development of iris hyperemia associated with miosis and poor visibility of fundus details occurred 24 hours after LPS injection. Compared to the LPS+ group, the clinical scores were strongly suppressed in rats treated with Dexamethasone and moderately diminished in LPS+ But 0.5 mM. These clinical features were not observed in the controls (Group 1 — naive). Data from inflammatory cytokines evaluation indicates no significant differences between the LPS+ group (Group 2) and the LPS+ But groups (Groups 4 and 5). Histopathological examinations suggest that hyperemia, corneal stratification, and lesions were less common in the group of animals treated with BA in a lower concentration. Conclusion: Topical administration of sodium butyrate as a therapeutic agent might alleviate the severity of intraocular inflammation in eyes with uveitis. The effect of sodium butyrate was slight but clinically significant in 0.5 mM dose, so other doses of topically administered sodium butyrate should be considered and evaluated in further research.

The Electrochemical Detection of 4-chloro-2-methylphenoxyacetic Acid (MCPA) Using a Simple Activated Glassy Carbon Electrode

4-Chloro-2-methylphenoxyacetic acid (MCPA) is one of the pesticides most widely used to control broadleaf weeds in arable and horticultural crops and it leaches readily into groundwater bodies causing pollution. In this study, a sensor was fabricated by the simple activation of a glassy carbon electrode (GCE) in an aqueous phosphate solution by cycling the GCE between –2.0 and 2.4 V vs SCE. The activated GCE exhibited very good detection of MCPA, with a linear concentration range extending from 1 to 850 μM (cyclic voltammetry) and a limit of detection (LOD) of 0.008 μM, which was obtained using differential pulse voltammetry. A more thermodynamically favoured oxidation of MCPA was observed at the activated GCE, with an approximate shift of 110 mV in the peak potential to lower potentials. Very good reproducibility and stability were achieved, with the sensor giving similar peak currents over a 30-day immersion period. Good selectivity was achieved in the presence of nitrates, nitrites, sulfates and structurally related compounds such as nitro-phenols. The promising performance of the activated GCE in the sensing of MCPA was attributed to the generation of oxygenated functional groups and an increased surface area arising from the local dissolution of the GCE during activation.

Phosphate Removal from Wastewater by Magnetic Amorphous Lanthanum Silicate Alginate Hydrogel Beads

It is of both fundamental and practical importance to develop effective adsorbents for removing phosphate from aqueous solutions continuously. In this study, magnetic amorphous lanthanum silicate alginate hydrogel beads (MALS-B) were prepared and used for phosphate removal. Mesoporous silica materials with highly ordered and hexagonal channel structures were synthesized from natural mineral rectorite (REC) at room temperature. On this basis, amorphous lanthanum silicate (ALS) was synthesized by theone-pot method using a silicon source from REC and a commercial lanthanum source. Further, MALS-B were synthesized from sodium alginate (SA) with ALS and Fe3O4 as the incorporated adsorbable and magnetic nanoparticles via a simple cross-linking method in CaCl2 solution. The synthesized hydrogel beads were characterized by various techniques. ALS and Fe3O4 existed relatively independently in MALS-B, where ALS provided adsorption sites and Fe3O4 provided magnetism. They played a synergistic role in phosphate removal. The saturation magnetization value of MALS-B was 17.38 emu/g, enabling theirfacile separation from aqueous solutions after phosphate adsorption. MALS-B exhibited a preferable adsorption capacity of 40.14 mg P/g for phosphorus compared to other hydrogel beads based on adsorption experiments. More significantly, MALS-B exhibited excellent selectivity for phosphate in aqueous solutions with various interfering ions and possessed a high affinity to phosphate in a wide pH range. MALS-B showed the treatment volume of 480 BV when effluent phosphate concentration was below 0.5 mg/L in fixed-bed column adsorption. The adsorption mechanism was also revealed. Our work demonstrates that MALS-B can serve as a promising adsorbent for continuous phosphate adsorption.

Removal of Phosphates in Aqueous Solution by Adsorption on Calcium Oxide

The aim of this work is the removal of phosphates from an aqueous solution by adsorption on a new, inexpensive adsorbent, calcium oxide. We have also shown interest in the choice of removal method, which is adsorption. The kinetic study of the removal of phosphate ions by adsorption on calcium oxide allowed us to calculate the value of adsorption capacity as a function of the parameters affecting adsorption: Amount of adsorbent, initial concentration of phosphate ion solution, pH of the mixture and temperature. The study of adsorption isotherms showed that the Freundlich model is the most appropriate for the phenomenon of phosphate ion adsorption. Modeling of the kinetic data by the pseudo-first order and pseudo-second order equations shows that the adsorption process is best described by the second order equation. Thermodynamic parameters such as enthalpy ΔH°, entropy ΔS° and free enthalpy ΔG° were also evaluated to determine the nature of adsorption. The results show that the adsorption process is a spontaneous and endothermic physisorption.

The Optimal Concentration of KH2PO4 Enhances Nutrient Uptake and Flower Production in Rose Plants via Enhanced Root Growth

Monopotassium phosphate is a widely used phosphorus and potassium fertiliser for ornamental plants, but it is not known what concentration will result in optimal flower production, root growth and nutrient uptake of rose plants. We compared potted rose plants fertilised with six different concentrations (0.0 as a water-only control, 1.0, 2.0, 3.0, 4.0 and 5.0 g·L−1) of an aqueous monopotassium phosphate solution as a combination of foliar and soil applications over two consecutive flowering cycles. Rose growth, flower production and nutrient accumulation responded differently to fertilisation with different concentrations of monopotassium phosphate. During the first flowering cycle, shoot and root dry weight, leaf chlorophyll content, flower diameter, total root length and surface area, and total fine root length significantly increased in response to increased monopotassium phosphate concentrations from 0.0 to 3.0 g·L−1 but decreased in response to fertilisation with 4.0 or 5.0 g·L−1 monopotassium phosphate. Similar trends were observed in shoot dry weight, leaf chlorophyll content, flower diameter and number, phosphorus and potassium accumulation during the second flowering cycle. According to quadratic equations derived from both flowering cycles, the optimal concentration of monopotassium phosphate, based on flower diameter and dry weight, as well as total phosphorus and potassium accumulation, was 2.6–3.0 g·L−1. Furthermore, total root length was significantly correlated with flower diameter, flower dry weight, and total phosphorus and potassium accumulation (p &lt; 0.05). These results indicated that fertilisation with optimal concentrations of monopotassium phosphate can increase rose growth, flower productivity and nutrient uptake through enhanced root growth.

Thermophysical properties of amino acids L-serine and L-leucine in aqueous diammonium hydrogen phosphate solutions: Volumetric and acoustic studies

Densities and speeds of sound measurements have been done for the amino acids (AAs) L-serine and L-leucine in aqueous diammonium hydrogen phosphate (DAP) solution at different temperatures with a specific interval of temperature. Thermophysical parameters including apparent molar volume (Vϕ), partial molar volume (Vϕ0), apparent molar isentropic compression (Kϕ,s), partial molar isentropic compression (Kϕ,s0) and transfer volumes like partial molar volumes of transfer (ΔVϕ0) and partial molar isentropic compression of transfer (ΔKϕ,so) were determined using the measured experimental data. The co-sphere overlap model was used to interpret the sort of interactions dominating in the system. The obtained transfer quantities are positive which indicates the dominance of ion-hydrophilic and hydrophilic–hydrophilic interactions existing among the amino acids and diammonium hydrogen phosphate salt solution in aqueous medium. Pair and triple interaction coefficients calculated for the system of amino acids and phosphate salt in aqueous medium. Overall results have been elaborated in terms of the solute-solvent or solute-solute interactions prevailing in the system.

Hydrothermal carbonization of distillers grains with clay minerals for enhanced adsorption of phosphate and methylene blue

A novel one-pot synthesis method was developed to prepare modified hydrochar by co-hydrothermal carbonization of waste distillers grains using low-cost clay minerals (attapulgite or vermiculite). The loading of the clay minerals onto hydrochar surfaces altered the structure and surface composition of the hydrochar such that the clay-modified hydrochars showed better ability to adsorb methylene blue and phosphate in aqueous solution than the pristine hydrochar. The maximum methylene blue and phosphate adsorption capacities of the modified hydrochar reached 340.3 and 96.9 mg g−1, respectively, comparable or higher than that of many commercial sorbents. Multiple mechanisms, including electrostatic attraction, ion exchange, complexation, and physical adsorption, controlled the adsorption process. These results highlight excellent potential for distillers grains-derived hydrochar-clay composites as an environmental sorbent, capable of removing a variety of contaminants from aqueous solutions.

Molecular relaxation dynamics and self-association of dexamethasone sodium phosphate solutions.

Detailed concentration-dependent measurements of sound absorption and velocity have been performed in dexamethasone sodium phosphate (DSP) aqueous solutions in the MHz frequency range. A single well-resolved relaxation process dominates the experimental acoustic spectra following a Debye-type distribution function. The analysis of the temperature-dependent ultrasonic relaxation data also revealed analogous effect with concentration on the relaxation spectra. All acoustic parameters were estimated by means of a fitting procedure. The behavior of the relaxation frequency and amplitude with concentration allowed us to assign the observed process to self-association mechanism. Combining the ultrasonic and electric conductivity data, the self-association scheme has been established. The thermodynamic constants and the rate of the aggregation due to hydrophobic interactions have been estimated in view of the Eyring’s theory. The concentration dependence of relaxation amplitude and characteristic frequency revealed that the presence of additional relaxation processes in the spectra related to additional mechanisms, such as conformational changes and proton-transfer reaction is excluded and the self-association process considered here was found to dominate in this frequency range. The results have been discussed in view of the fair ability of DSP for hydrophobic interactions and aggregate formation in aqueous environment.Graphic abstract