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This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (Kc) and overall volumetric mass transfer coefficient (KLa) are 4.28×10−3 s−1 and 11.60×10−3 s−1 respectively at an initial pH of 6, β of 40, C O 3 ( g ) of 60 mg·L−1 and QL of 85 L·h−1 in deionized water, respectively. Meanwhile, the Kc and KLa values of Fenhe water are 0.88×10−3 s−1 and 2.51×10−3 s−1 lower than deionized water, respectively. In addition, the Kc and KLa values in deionized water for the Cat/O3-RPB system are 44.86% and 47.41% higher than that for the Cat/O3-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

Bismuth (Bi) was evaluated recently as an alloy-type anode material for aqueous alkali-metal ion batteries (ARABs) on account of its high theoretical capacity (385 mAh g−1), low redox potential (∼ −0.8 V vs. SCE), dendrite-free and absence of memory effects. However, it remains challenging for clarifying and pinpointing the intrinsic interaction mechanism between Bi and alkali metal ions (Li+, Na+ and K+), which is significant to reveal the potential and limitation of Bi electrode for future applications in ARABs. Herein, we gain the insights into the similarity and divergence of the (de)alloying mechanism of aqueous Bi anode for AM ions (Li+, Na+ and K+) storage by ex-XANES, SXES, HRTEM and DFT. As a result, Bi shows superior specific capacities for Na+ and K+ storage but the lowest capacity for Li+ storage. Large adsorption energy makes Li+ dealloy from Bi matrix irreversibly, causing inferior rate performance and cycling stability. The largest radius of K+ triggers large volume expansion, which is responsible for the poor cycling stability for K+ storage. Bi exhibits superior performance for Na+ storage owning to the appropriate interaction strength between Bi and Na+. Our work can provide a proof-of-concept to universally pinpoint interactions between electrode and charge carriers for a wide range of metal electrodes.

Aim: Selective and sensitive visual detection of Cu2+in aqueous solution at PPB level using easily synthesized compound. Background: The search for a chemosensor that can detect Cu2+ is very long owing to the fact that an optimum level of Cu2+ is required for human health and the recommended amount of Cu2+ in drinking water is set to be 1-2 mgL-1 . Thus, it is very important to detect Cu2+ even at a very low concentration to assess the associated health risks. Objective: We are still seeking for the easiest, cheapest, fastest and greenest sensor that can selectively, sensitively and accurately detect Cu2+ with lowest detection limit. Our objective of this work is to find one such Cu2+ sensor. Methods: We have synthesized a quinoline derivative following very easy synthetic procedures and characterize the compound by standard methods. For sensing study, we used steady state absorption and emission spectroscopy. Results: Our sensor can detect Cu2+ selectively and sensitively in aqueous solution instantaneously even in the presence of excess amount of other salts. The pale-yellow color of the sensor turns red on the addition of Cu2+ . There is no interference from other cations and anions. A 2:1 binding mechanism of the ligand with Cu2+ is proposed using Jobs plot with binding constant in the order of 109 M-2 . We calculated the LOD to be 18 ppb, which is quite low than what is permissible in drinking water. Conclusion: We developed a new quinoline based chemo-sensor following straightforward synthetic procedure from very cheap starting materials that can detect Cu2+ visually and instantaneously in aqueous solution with ppb level sensitivity and zero interference from other ions.

Chromium is a harmful contaminant showing mutagenicity and carcinogenicity. Therefore, detection of chromium requires the development of low-cost and high-sensitivity sensors. Herein, blue-fluorescent carbon quantum dots were synthesized by one-step hydrothermal method from alkali-soluble Poria cocos polysaccharide, which is green source, cheap and easy to obtain, and has no pharmacological activity due to low water solubility. These carbon quantum dots exhibit good fluorescence stability, water solubility, anti-interference and low cytotoxicity, and can be specifically combined with the detection of Cr(VI) to form a non-fluorescent complex that causes fluorescence quenching, so they can be used as a label-free nanosensor. High-sensitivity detection of Cr(VI) is achieved through internal filtering and static quenching effects. The fluorescence quenching degree of CDs fluorescent probe showed a good linear relationship with Cr(VI) concentration in the range of 1–100 μM. The linear equation was F0/F = 0.9942 + 0.01472[Cr(VI)] (R2 = 0.9922), and the detection limit can be as low as 0.25 μM (S/N = 3), which has been successfully applied to Cr(VI) detection in actual water samples herein.

Three-dimensional (3D) plasmonic nano-arrays can provide high surface-enhanced Raman scattering (SERS) sensitivity, good spectral uniformity and excellent reproducibility. However, it is still a challenge to develop a simple and efficient method for fabrication of 3D plasmonic nano-arrays with high SERS performance. Here we report a facile approach to construct ordered arrays of silver (Ag) nanoparticles-assembled spherical micro-cavities using polystyrene (PS) sphere template-assisted electrodeposition and post-growth. The electrodeposited small Ag nanoparticles grow into bigger stable nanoparticles during the post-growth process, which could significantly improve the SERS sensitivity. The Ag nanoparticles-assembled 3D micro-cavity array provides much more hotspots in the excitation laser beam-covered volume than the two-dimensional counterpart. The relative standard deviation (RSD) of 612 cm−1 peak of rhodamine 6G (R6G) was calculated to be 8%, and the RSD of the characteristic peak taken from substrates of different batches was less than 10%. The detectable lower concentration as low as 1 fM was achieved for an aqueous solution of R6G. Such SERS substrate also showed high sensitivity to thiram (fungicide) and paraquat (herbicide) in water with limits of detection of 0.067 nM and 2.5 nM respectively. Furthermore, it also demonstrated that SERS detection of pesticide residues on fruits can be realized, showing a potential application in rapid monitoring food safety.

In this study, nitrogen-doped graphene quantum dots (N-GQDs) exhibiting high water solubility were produced based on the hydrothermal approach. Ethylenediamine (EDA) was used as the nitrogen dopant and microcrystalline cellulose (MCC), extracted from pineapple leaf fiber (PALF) biomass, used as the carbon source. The as-prepared N-GQDs exhibited an average size of 3.7 nm, 8-10 layers and the excitation wavelength-dependent fluorescence. It was noteworthy that controlling the pH value of the EDA solution in the hydrothermal process could change the fluorescence color of the N-GQDs, exhibiting unique green, cyan and blue light. Besides, because of the effective fluorescence quenching effect of N-GQDs by mercury (II) ions (Hg2+), the as-prepared N-GQDs were successfully employed as the efficient nanosized fluorescence sensors to selectively detect Hg2+ in aqueous solutions with the detection limit of 0.25 nM and a linear range of 0∼30 μM. The selectivity experiments indicated that as-prepared N-GQDs were specific for Hg2+ even with interference by high concentrations of other metal ions. Notably, the N-GQDs could be well adopted to determine Hg2+ in river water samples.

Despite the broad range of interest and applications, controls on the electric surface charge and the zeta potential of silica in contact with aqueous solutions saturated with dissolved CO2 at conditions relevant to natural systems, remains unreported. There have been no published zeta potential measurements conducted in such systems at equilibrium, hence the effect of composition, pH, temperature and pressure remains unknown. We describe a novel methodology developed for the streaming potential measurements under these conditions, and report zeta potential values for the first time obtained with Fontainebleau sandstone core sample saturated with carbonated NaCl, Na2SO4, CaCl2 and MgCl2 solutions under equilibrium conditions at pressures up to 10 MPa and temperatures up to 40 °C. The results demonstrate that pH of solutions is the only control on the zeta potential, while temperature, CO2 pressure and salt type affect pH values. We report three empirical relationships that describe the pH dependence of the zeta potential for: i) dead (partial CO2 pressure of 10-3.44 atm) NaCl/Na2SO4, ii) dead CaCl2/MgCl2 solutions, and iii) for all live (fully saturated with dissolved CO2) solutions. The proposed new relationships provide essential insights into interfacial electrochemical properties of silica-water systems at conditions relevant to CO2 geological storage.

A microfluidic platform to extract uranium from HNO3 (nitric acid) medium using tri-isoamyl phosphate (TiAP) dissolved (30% v/v) in ionic liquid ([BMIM]PF6) is reported. PTFE microbore tubes serve as the microchannels. The quality of dispersion inside the translucent tubes was observed using a camera. The images obtained are used to understand the observed experimental trends. Overall volumetric mass transfer coefficient was determined considering the microchannel as a differential contactor with co-currently flowing phases. The effects of contact time, flow velocity, organic to aqueous (O/A) ratio and microchannel diameter on mass transfer performance are studied. Effect of different coiling configurations on mass transfer performance was compared. Under optimum conditions, 95.3% of uranium present in the feed (corresponding stage efficiency being 99.2%) could be extracted within a contact time of about 200 s in a single contact. Corresponding (KLa) was 0.024 s−1. Coiling was found to have a significant effect on values of KLa especially at low residence times.

This work introduced a novel microchannel extractor. The extraction system was to extract lanthanum nitrate aqueous solution with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA). Different feeding methods and inner rotors were explored first. The results showed that parallel feeding and inner rotors engraved with spiral stripes were more favorable for extraction. Next, the effect of various factors on the extraction was explored, including the pH of the aqueous phase, rotational inner rotor speed (R) and the fluid volumetric flow rate (Q). The results showed that these factors are closely related to the extraction. Finally, the experiment was verified by CFD numerical simulation, the simulation result was consistent with the experiment. In this device, active mixing was introduced into the microchannel extraction, which significantly improved the extraction efficiency. Under certain conditions, the extraction efficiency of this device exceeded stirring extraction equilibrium. Moreover, the extraction in this device is faster than conventional stirring extraction. These advantages provide a possibility for highly efficient extraction and use of rare earth elements.

A semi organic nonlinear optical single crystal of L-valine barium chloride was grown from an aqueous solution by the method of slow evaporation technique at room temperature. The grown crystal was characterized by powder X- ray diffraction confirms the presence of chloride. Single crystal X-ray diffraction studies confirm that the grown crystal belongs to the monoclinic system. The functional groups presented in the crystal were confirmed by FT-IR technique. The UV–vis-NIR spectrum indicates that the crystal has very good absorption in the entire visible and NIR region spectrum indicating the stability of the materials for NLO applications. The grown crystal was subjected to EDX to confirm the presence of the elements. The crystal was stable up to 260⁰C and fully decomposed at 907⁰C. Hence the thermal behaviour and the stability of crystal were studied by TGA, DTA and DSC. The second harmonic generation SHG efficiency was studied by Kurtz-Perry powder technique. The minimum inhibitory concentration (MIC) of the crystal for antibacterial activity was studied using micro dilution bioassay as described by ELOFF.

We investigated the structural, dynamic, energetic, and electrostatic properties of electrolytes based on the ion pairs LiCl and Li2SO4. Atomistic molecular dynamics simulations were used to simulate these aqueous electrolytic solutions at two different concentrations 2M (normal) and 21M (superconcentrated, WiSE). The effects of valence asymmetry of the Li2SO4 electrolyte were also discussed for all performed. Our results differ in the physical aspect of pure electrolytes, showing the drastic effect of high concentration, in special for the viscosity, which is dramatically increased in WiSE. This is a consequence of their reduced ionic mobility and has a direct effect on ionic conductivity. Also, our results for the graphene-based supercapacitor, as indicated by some experimental work, do not indicate any better performance of WiSE electrolytes over normal electrolytes. In fact, the differences in the total capacitance, due to the concentration of ions, presented by both electrolytes are negligible. The valence asymmetry can be clearly observed in some properties but for most of them its effects could not be quantified or isolated.

A novel ionic liquid (IL) functionalized with thiodiglycol amic acid containing a soft S donor was synthesized for the effective and efficient extraction of platinum group metals (Ru, Rh, and Pd) from aqueous nitric acid solutions, such as high-level radioactive liquid waste (HLLW). The IL enabled rapid extraction of Pd(II) with an extraction ratio of approximately 100%. The extractions of Ru(III) and Rh(III) by the IL were slower than that of Pd(II), but the rates were accelerated by temperature elevation. The extractions of Ru(III) and Rh(III) at 50 °C reached equilibrium within 4 and 8 h, respectively, with the extraction ratios of over 90% without assisting agents or other methods for the extraction system. Furthermore, the IL could extract more than 90% of Ru(III), Rh(III), and Pd(II) from the simulated HLLW within 2 h at 50 °C.

Due to the toxicity of cadmium (Cd) and the scarcity of telluride (Te), CdTe-based photovoltaic modules have been under discussion during the last few years. In particular, the stability of CdTe in aqueous solutions is under debate. Here we show that the stability of CdTe depends not only on the pH of water-based solutions but also on size and surface treatment of CdTe particles. We compare milled module pieces with CdTe powders of different particle size. The leaching of CdTe is conditioned by the outdiffusion of Cd and Te at the interface between CdTe particles and the aqueous solution. The smaller the particle size, the faster the leaching. Therefore, milled module pieces decompose faster than CdTe powders with relatively large grains. We observe a dependence on time t according to t0.43. The room temperature diffusion coefficients are calculated as DCd ≈ 3 × 10-17 cm2/s for Cd, and DTe ≈ 1.5 × 10−17 cm2/s for Te in pH4. The chemical instability in aqueous solutions follows thermodynamic considerations. The solution behavior of Cd and Te depends on the pH value and the redox potential of the aqueous solutions. Chemical treatments such as those used in solar cell production modify the surface of the CdTe particles and their leaching behavior., Bundesministerium für Wirtschaft und Technologie

In this study, Box-Behnken design (BBD) in response surface methodology (RSM) was employed to optimize As(V) removal from an aqueous solution onto synthesized crosslinked carboxymethylchitosan-epichlorohydrin/Fe3O4 nanaocomposite. The factors like solution pH, adsorbent dose, contact time and temperature were optimized by the method which shows high correlation coefficient (R2 = 0.9406), and a predictive quadratic polynomial model equation. The adequacy of the model and parameters were evaluated by analysis of variance (ANOVA) with their significant factors of Fischer’s F-test (p < 0.05). Seven significant parameters with interaction effects in the experiment with p-value < 0.0001 was observed, having a maximum removal efficiency of As(V) is 95.1%. Optimal conditions of dosage, pH, temperature, initial ion concentration and contact time in the process were found to be 0.7 g, pH 6.5, 308K, 10 mg/L and 60 min respectively. Langmuir isotherm model fitted better than the Freundlich model having a maximum adsorption capacity of 28.99 mg/g, a high regression value of 0.9988, least chi-square value of 0.1781. The process was found to follow monolayer adsorption and pseudo-second-order kinetics. Thermodynamic parameters indicate the process is spontaneous, endothermic and physisorption in nature. Successful regeneration of the adsorbent implies its applicability to the removal of arsenic from real life wastewater.

Climate change and global warming are the visible consequences of the increased amount of carbon dioxide (CO2) in the atmosphere. Among the various sources of anthropogenic CO2 emission, the diesel engine has a significant contribution. The development of a reliable system to efficiently minimize CO2 emissions from diesel engines to the safest level is lacking in the open literature. Therefore, a comprehensive multidisciplinary approach has been applied in this paper to investigate the efficacy of the post-combustion carbon capture (PCC) process for the diesel engine. The experiments have been performed on the exhaust of a direct injection diesel engine at five different brake powers with blends of aqueous ammonia (AQ_NH3), monoethanolamine (MEA), N,N-dimethylethanolamine (DMEA), and 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) ionic liquid (IL) as an absorbent for CO2 capture. The reaction mechanism of these absorbent with CO2 are also studied by the geometrical, energetical, MESP, frontier molecular orbitals, and NBO analysis using the first-principles density functional theory (DFT) calculations. The maximum CO2 absorption efficiency of almost 97% was achieved for the blend consisting of 67% of AQ_NH3 and 33% of MEA. Moreover, AQ_MEA and blend of AQ_NH3, DMEA, and C2mim BF4 ionic liquid showed 96% and 94% CO2 absorption efficiency, respectively.

The work discusses about the synthesis of indium-alizarin red S complex followed by its application toward the sensing of F¯ ion. At first, the interaction between indium and alizarin red S dye was studied at three different pH medium, pH 4, 7 and 9, of which pH 7 gave the best result. The indium-alizarin red S complex so obtained was then utilized for the ratiometric sensing of fluoride ion using absorption spectroscopy with variation of temperature. The lowest limit of detection (0.040 mM) was obtained at 313 K. The mechanism for the sensing of F¯ ion was then investigated using isothermal titration calorimetry. The endothermic nature of the interaction between F¯ ion with indium-alizarin red S complex shows temperature dependence on the sensing experiment. At the end, the utility of the technique toward natural sample was also examined. The present work reports a simple, rapid and efficient detection of fluoride anion in environmental water samples.

Natural gas hydrate is a kind of clean energy with huge reserves, and the saturation (volume percentage of hydrate in pore space of sediments) is the key parameter for determining whether the reservoir is worthy of exploitation. In this work, rapid hydrate dissociation by the combination of heat injection and NaCl inhibitor addition was studied, and an on-site evaluation method for hydrate saturation in sediment samples was proposed by using a core sampler to transfer hydrate samples under pressure. The results showed that the average gas production rate per unit volume was increased significantly to reach 7.22 L/Lr·min-1 by the injection of NaCl aqueous solution with 50.9 °C, which was attributed to the increase of the chemical potential to further accelerate the rate of hydrate dissociation in the presence of NaCl. Furthermore, for the measurement of methane hydrate samples saturation with a volume of 673 cm3 (which contained 1.4 mol hydrates with the saturation of 58%), hydrate saturation could be accurately achieved within 30 min with a relative error lower than 11.7% This work may provide new thoughts for on-site saturation evaluation and rapid dissociation of hydrate samples during natural gas hydrate exploitation.

The impedance, capacitance and conductance of aqueous sucrose polar solution are measured by employing impedance spectroscopy method and the current passing through the system for different DC voltages are measured implementing I-V method. The variation of electrical parameters with sucrose content in such solution exhibits a quasi-oscillatory nature, which is attributed to the random orientation of water and sucrose dipoles in the solution and their mutual interactions at the molecular level, including water-water, water-sucrose and sucrose-sucrose dipole interactions. To justify the quasi-oscillatory nature from analytical point of view, a theoretical model is developed on the basis of multi-body dipolar interactions of randomly distributed molecular dipoles. The experimental data agrees well with those obtained from the analytical model. The measurement of electrical parameters is performed within a frequency window of 100 Hz to 4 MHz for volume fractions of sucrose with respect to water, ranging from - pF - 266 pF, and 3 µS - 55 µS respectively for the sucrose volume fraction range considered. Current voltage measurements for the same concentration range are performed for a voltage swing between ±5 V and the obtained values vary from +20 µA to -25 µA. The study represents a deterministic approach to analyze the effective nature of a sucrose solution in terms of dielectric polarization of the system which finds application in sucrose quality assessments.

Ultraviolet (UV)–visible (Vis) spectroscopy is widely used in all modern laboratories as a routine method of analysis. The monitoring of chemical reactions in an aqueous solution involving a gas pr...

In the presence of inorganic salts, secondary organic aerosol (SOA) undergoes liquid-liquid phase separation (LLPS), liquid-solid phase separation, or a homogeneous phase in ambient air. In this study, a regression model was derived to predict aerosol phase separation relative humidity (SRH) for various organic and inorganic mixes. The model implemented organic physicochemical parameters (i.e., oxygen to carbon ratio, molecular weight, and hydrogen-bonding ability) and the parameters related to inorganic compositions (i.e., ammonium, sulfate, nitrate, and water). The aerosol phase data were observed using an optical microscope and also collected from the literature. The crystallization of aerosols at the effloresce RH (ERH) was semiempirically predicted with a neural network model. Overall, the greater SRH appeared for the organic compounds with the lower oxygen to carbon ratios or the greater molecular weight and the higher aerosol acidity or the larger fraction of inorganic nitrate led to the lower SRH. The resulting model has been demonstrated for three different chamber-generated SOA (originated from β-pinene, toluene, and 1,3,5-trimethylbenzene), which were internally mixed with the inorganic aqueous system of ammonium-sulfate-water. For all three SOA systems, both observations and model predictions showed LLPS at RH

Prediction of adsorption capacity, one of the most important properties of any adsorbent-adsorbate system, is crucial for adsorption studies. In this investigation, two approaches such as multilayer perceptron (MLP) and random forest (RF) were used to predict the adsorption capacity of hexadecyltrimethyl ammonium modified bentonite to remove chlorobenzene (CB) from aqueous solution. The adsorption study was conducted in batch mode at different adsorption parameters. The results show that the adsorption processes were best described by Freundlich isotherm model, while the adsorption mechanism followed the pseudo-second order kinetics. It was observed that the structure of MLP model that give the best prediction consisted of three layers: input layer with four neurons, output layer with one neuron, and four neurons at hidden layer. The three important parameters for RF model were ntree = 500, mtry = 1, and node size = 1. According to the results obtained, the MLP model provided slightly higher levels of accuracy with a consistently high coefficient of determination (R2 = 0.996) and low root mean square error (RMSE = 0.00101) compared to RF model. (R2 = 0.969, RMSE = 0.03008). Therefore, the initial concentration of CB with 35.29%, appeared to be the most influential parameter in the adsorption of CB on the modified bentonite.

Characterizing the molecular composition of cloud water could provide unique insights into aqueous chemistry. Field measurements were conducted at Mt. Tianjing in southern China in May, 2018. There are thousands of formulas (C5–30H4–55O1–15N0–2S0–2) identified in cloud water by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). CHON formulas (formulas containing C, H, O, and N elements; the same is true for CHO and CHOS) represent the dominant component (43.6 %–65.3 % of relative abundance), followed by CHO (13.8 %–52.1%). S-containing formulas constitute ∼5 %–20 % of all assigned formulas. Cloud water has a relative-abundance-weighted average O/C of 0.45–0.56, and the double bond equivalent of 5.10–5.70. Most of the formulas (>85 %) are assigned as aliphatic and olefinic species. No statistical difference in the oxidation state is observed between cloud water and interstitial PM2.5. CHON with aromatic structures are abundant in cloud water, suggesting their enhanced in-cloud formation. Other organics in cloud water are mainly from biomass burning and oxidation of biogenic volatile organic compounds. The cloud water contains more abundant CHON and CHOS at night, which are primarily contributed by −N2O5 function and organosulfates, demonstrating the enhanced formation in dark aqueous or multi-phase reactions. While more abundant CHO is observed during the daytime, likely due to the photochemical oxidation and photolysis of N- or S-containing formulas. The results provide an improved understanding of the in-cloud aqueous-phase reactions.

A long-term stable aqueous colloidal dispersed ATO solution was obtained through the addition of aqueous ammonia. ATO nanoparticles could be dispersed evenly, forming stable ATO water-dispersed sol solution, and no agglomeration or sedimentation occurred at least 9 months. X-ray diffraction, transmission electron microscopy and energy-dispersive spectroscopy were employed to characterize the obtained ATO. Dynamic light scattering and UV–Vis–NIR spectrophotometer were used to record the particle sizes and transmission spectra of as-prepared ATO inks, respectively. The highest transmittance at low ATO concentration is 89.6% at 760 nm. In the near-infrared region, the transmittance has an obvious decrease, which is 51.5% at 1300 nm. The transmittance of as-prepared ATO solution in visible and near-infrared wavelengths (300–1300 nm) decreased significantly with the increase in the ATO concentration, especially in the near-infrared wavelengths, which proved that the as-prepared ATO had a shielding performance in the near-infrared region.

Designing analytical approaches for enzymatic activity monitoring with high sensitivity and selectivity is of critical value for the diagnosis of diseases and biomedical studies. In this study, we have created a facile one-step synthetic route to prepare orange-red color and yellow fluorescent silicon-containing nanoparticles (Si CNPs) by mixing 3(2-aminoethylamino) propyl (dimethoxymethylsilane) and hydroquinone (HQ) in an aqueous solution. Inspired by the HQ-regulated facile synthetic step and the generation of HQ from α-glucosidase (α-Glu)-catalyzed hydrolysis of 4-hydroxyphenyl-α-d-glucopyranosyl (4-HPαDG), we have designed a straightforward colorimetric and fluorometric α-Glu activity assay using a commercially available 4-HPαDG as the α-Glu substrate. Fluorescent and colorimetric assays for α-Glu activity measurement have been thereby established and exhibited detection limits as low as 0.0032 and 0.0046 U/mL, respectively. Under single excitation at 370 nm, the prepared Si CNPs emitted yellow fluorescence at 520 nm and exhibited an absorbance peak at 390 nm. In addition, the proposed approach reveals various advantages including easy operation, time-saving, and good anti-interference ability. Hence, it could improve the progress of fluorometric and colorimetric enzymatic activity assays with high sensitivity and simplicity. Moreover, the proposed approach was applied for α-Glu inhibitor screening, and its feasibility in real samples was measured by detecting the α-Glu activity in human serum samples.

open access article A terephthalic acid-modified chitosan−magnetic nanocomposite (Cs−Tp@Fe3O4) was synthesized and characterized. The synthesized Cs−Tp@Fe3O4wasused in a batch process for the adsorptive removal of the acid blue 25 (AB-25) dye inaqueous solutions. The kinetic data were subjected to the pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion models, while the equilibrium datawere evaluated with the Langmuir, Freundlich, Temkin, and Dubinin−Radushkevichisotherm models. The effects of the initial dye concentration, contact time, andadsorbent dosage, as well as their interactions, on the removal efficiency wereinvestigated using the design of experiments based on a central composite design, andthe resultant data were modeled with the response surface methodology (RSM),artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), andmultiple linear regression (MLR) approaches. The adsorption process followedpseudo-first-order with good agreement between the experimentalQe(exp)andcalculatedQe(cal.)amounts of dye adsorbed, as well as the values of correlation coefficient,R2(0.999) and percentage of sumsquare error, % SSE (0.640). All the investigated adsorption isothermsfitted all models well in the order of Dubinin−Radushkevich> Langmuir > Freundlich > Temkin withR2> 0.9 with the monolayer maximum adsorption capacity of 440.24 mg/g obtained fromthe Langmuir isotherm. The RSM model predicted the maximum removal efficiency at an optimum initial dye concentration of19.11 mg/L, a contact time of 95.3 min, and an adsorbent dosage of 0.18 g. Statistically, the models werefitted in the order of RSM> ANN > ANFIS > MLR. These results indicated that the prepared Cs−Tp@Fe3O4is an efficient adsorbent for the AB-25 dyeremoval with excellent stability for water treatment applications. (8) (PDF) Chitosan–Terephthalic Acid–Magnetic Composite Beads for Effective Removal of the Acid Blue Dye from Aqueous Solutions: Kinetics, Isotherm, and Statistical Modeling. Available from: https://www.researchgate.net/publication/355954648_Chitosan-Terephthalic_Acid-Magnetic_Composite_Beads_for_Effective_Removal_of_the_Acid_Blue_Dye_from_Aqueous_Solutions_Kinetics_Isotherm_and_Statistical_Modeling [accessed Nov 25 2021].

We investigated the chemical behavior of lanthanides (Ln) by multistage extraction. Using 10 aqueous phases with Ln and 3 organic phases, we drew the breakthrough curves for light and middle Ln. Our study reveals that the limit of metal extraction depends on their D values and the metal concentration employed in experiments. From the multistage extractions of 15 stage aqueous phases and 15 stage organic phases, three curves (extraction curves, back-extraction curves, and separation curves) were obtained. Setting appropriate conditions, adequate separation of light Ln from middle ones can be achieved. As an example, under the condition of the separation curve experiment (aqueous phase: 0.5 M HNO3, organic phase: 0.1 M TDDGA (N,N,N',N'-tetradecyl-diglycolamide) in n-dodecane), the recovery of more than 99% of Sm in the organic phase with less than 1% of Nd can be obtained, even in the case of two metals adjacent to each other in the Ln series.

Mineral trapping through the precipitation of carbonate minerals is a potential approach to reduce CO2 accumulation in the atmosphere. The temperature dependence of amorphous magnesium carbonate (AMC), a precursor of crystalline magnesium carbonate hydrates, was investigated using synchrotron X-ray scattering experiments with atomic pair distribution function (PDF) and X-ray absorption fine structure analysis. PDF analysis revealed that there were no substantial structural differences among the AMC samples synthesized at 20, 60, and 80 °C. In addition, the medium-range order of all three AMC samples was very similar to that of hydromagnesite. Stirring in aqueous solution at room temperature caused the AMC sample to hydrate immediately and form a three-dimensional hydrogen-bonding network. Consequently, it crystallized with the long-range structural order of nesquehonite. The Mg K-edge X-ray absorption near-edge structure spectrum of AMC prepared at 20 °C was very similar to that of nesquehonite, implying that the electronic structure and coordination geometry of Mg atoms in AMC synthesized at 20 °C are highly similar to those in nesquehonite. Therefore, the short-range order (coordination environment) around the Mg atoms was slightly modified with temperature, but the medium-range order of AMC remained unchanged between 20 and 80 °C.

Background Supported liquid membrane (SLM) is a very promising method for the recovery and separation of valuable or toxic species from aqueous streams; however, stability is always a critical issue in practice. It is highly desired to develop a non-destructive technique to real-time monitor or detect the stability of an SLM process. Methods The stability of an SLM processes was real-time analyzed by electrical impedance spectroscopy (EIS). The separation of equimolar Zn(II) and Cu(II) from sulfate solution through an SLM containing di(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene was selected as the model system owing to the established knowledge of extraction chemistry. Experiments were performed with two types of membrane supports (polycarbonate and poly(vinylidene) fluoride), different D2EHPA concentrations in the organic phase (0.001–0.1 mol/L), pH values of the feed (3.0–5.0) and strip (1.0–3.0) phases, and stirring speeds (0–200 rpm). Correlations between the membrane impedances analyzed according to a proposed equivalent circuit diagram and the separation factors of Zn2+ over Cu2+ measured by SLMs were done to verify the progress of the loss of membrane liquid. Significant findings Under the conditions studied, the variations of membrane impedances and separation factors with time using both types of membrane support followed similar trends in most cases. A stability factor of a SLM process based on membrane impedance data was defined, which enables us to predict its relative stability. The present results also demonstrated that all parameters including membrane type, carrier concentration, aqueous pH values, and stirring speed influenced the transport and separation of Zn2+ over Cu2+ and SLM stability.

Refractive indices () and densities (r) of water (W) + n-butylamine (NBA), + sec-butylamine (SBA) and + tert-butylamine (TBA) systems had been measured in the whole range of composition at 303.15 K, from which deviation in refractive index (DnD ) molar refraction (Rm) and excess molar refraction () had been evaluated. All of the derived properties were fitted to appropriate polynomials. DnD were fitted to the Redlich-Kister polynomial equation. Values of DnD were all positive and were all negative which were attributed to cross hydrogen bonding, specific interactions as well as interstitial accommodation effect. A comparative study of Lorentz-Lorenz (L-L), Weiner (W), Heller (H), Gladstone-Dale (G-D), Arago-Biot (A-B), Eykman (Eyk), Newton (Nw), Eyring-John (E-J) and Oster (Os) relations for determining the refractive index of a liquid had been carried out to test their validity for the three binaries over the entire mole fraction range of butylamines at 303.15 K.

The physicochemical properties of aqueous ternary ionic liquid (IL) and nanoparticle systems are affected by the various intermolecular interactions such as van der Waals, electrostatic and structural. Recently these systems have been considered both to increase the stability of nanofluids and to change the surface activity of the surface active ILs. A systematic experimental study was conducted on aqueous solutions containing a surface active ionic liquid, 1-octyl-3-methylimidazolium bromide ([C8mim][Br]), in pure water and in CuO-water nanofluids to a better understanding of the aggregation behavior occurring in these systems. The electrical conductivity (κ) data were obtained for [C8mim][Br] + water and [C8mim][Br] + CuO–water nanofluid (with 0.00066 wt%, 0.005 wt% and 0.01 wt% of CuO NPs) systems at 288.15, 293.15, 298.15 and 303.15 K. For these systems, surface tension (γ) measurements were taken at 298.15 K. The accurate analysis of the obtained data showed that the critical micelle concentration (cmc) for [C8mim][Br] in aqueous solution is increased with addition of CuO NPs to pure water, as well as with increasing concentration of CuO NPs in water-based fluid. The values of Gibbs energy, ΔG°mic, enthalpy, ΔH°mic, and entropy, ΔS°mic, of micellization were determined from the specific electrical conductivity data. The values of ΔG°mic were negative and magnitude of ΔG°mic (kJ⋅mol−1) followed the order: 288.15 K (− 21.95) 0) and with a temperature raise, this process becomes enthalpically driven process (ΔH°mic

The densities and viscosities of electrolytes are essential to understand many physicochemical processes that are taking place in the solution. In the present research, the densities and viscosities of lithium halides, LiX (X = Cl, Br, I ) and KCl in (0, 20, 40, 50, 60, 80 and 100) mass % of methanol + water at 313.15K were calculated employing experimental densities (ρ), the apparent molar volumes( ϕv) and limiting apparent molar volumes (0v) of the electrolytes. The (0v) of electrolyte offer insights into solute-solution interactions. In terms of the Jones-Dole equation for strong electrolyte solution, the experimental data of viscosity were explored. Viscosity coefficients A and B have been interpreted and discussed. The B-coefficient values in these systems increase with increase of methanol in the solvents mixtures. This implied that when the dielectric constant of the solvent decreases, so do the solvent-solvent interactions in these systems.

For the first time, highly porous hypercrosslinked polystyrene layer was synthesized within a gas chromatography capillary column and successfully deposited onto the capillary walls generating porous layer open-tubular capillary column. Elaborated three steps synthetic procedure provides tightly bonded porous polymeric layer and ensues complete elimination of particle shedding and the needs for particle traps. Due to highly developed surface area, porous layer open-tubular column provides strong solute retention that is useful for the separation of various volatile solvents and light gas compounds including ethane, ethylene, ethyne. Aqueous injections will not harm the column.

In the present research, graphene oxide (GO) nanosheets were synthesized by sugar beet bagasse as an agricultural waste. Then, the synthesized nanosheets were modified with magnetic nanoparticles to produce a hybrid of nanomaterials that can be used for magnetic solid-phase extraction (MSPE) of diazinon as a model of organophosphorus pesticides (OPPs) in environmental and food samples. The produced adsorbent was characterized by FT-IR spectroscopy, XRD analysis, SEM, and TEM. These results exhibited Fe3O4 nanoparticles with an average size of 17.22 nm were uniformly distributed on the surface of the GO nanosheets. Next, the effective experimental factors controlling the extraction recoveries such as desorption conditions, sorbent dosage, pH of analyte solution, extraction time, and concentration of analyte were assessed and optimized via response surface methodology (RSM) based on central composite design (CCD). Generally, the optimum adsorption condition was suggested by software (sorbent dosage = 0.35 g/L, pH = 5.04, extraction time = 8 min, and diazinon concentration of 12 µg/L), though in order to achieve the highest recovery, the target condition was investigated. Finally, the concentration of extracted analyte was quantified via a gas chromatography-nitrogen phosphorous detector (GC-NPD). The magnetically separable nanoadsorbent showed appropriate sustainability and reusability even after four cycles of sorption- desorption. The detection limit of method was 2.41 μg/L. Also, this procedure was successfully used for identification of diazinon in water, milk, and honey samples with the obtained results showing acceptable recovery values.

Polyacrylamide (PAA)-kaolinite (K) composite adsorbent was synthesized using K and PAA hydrogel, in-situ polymerization method as synthesis method. Adsorbent performance of the PAA-K composite for UO22+ ions was optimized: 400 mg L−1 at pH 4.5 at 25 °C. Synthesized PAA-K composite was featured by FT-IR, SEM–EDX, and XRD techniques. The maximum UO22+ ions adsorption capacity of the PAA-K composite was found to be 0.0656 mol kg−1. Thermodynamic parameters demonstrated that the behaviour of the adsorption was an endothermic and spontaneous. Finally, adsorption process suggested that the PAA-K composite had a significant adsorption capacity for the UO22+ ions.

Difference circular dichroism (CD) spectroscopy was used here to characterize changes in structure of flexible peptides upon altering their environments. Environmental changes were introduced by binding to a large target structure, temperature shift (or concentration increase) or so-called membrane-mimicking solvents. The first case involved binding of a largely disordered peptide to its target structure associated with chromatin remodeling, leading to a transition into a highly helical structure. The second example was a short 8HD (His-Asp) repeat peptide that can bind metal ions. Both Zn and Ni at μM concentrations resulted in different type of changes in secondary structure, suggesting that these metal ions provide different environments for the peptide to assume unique secondary structures. The third case is related to a few short neuroprotective peptides that were largely disordered in aqueous solution. Increased temperature resulted in induction of significant, though small, β-sheet structures. Last example was the induction of non-helical structures for short neuroprotective peptides by membrane-mimicking solvents, including trifluoroethanol, dodecylphosphocholine and sodium dodecylsulfate. While these agents are known to induce α-helix, none of the neuropeptides underwent transition to a typical helical structure. However, trifluoroethanol did induce α-helix for the first peptide involved in chromatin remodeling described above in the first example.

For quasi-elastic neutron scattering (QENS) studies, sample cells made of pure or alloyed aluminium are frequently employed. Although the Al surface is protected by a passivating film, this film is not robust. Therefore, when the sample is an aqueous solution, chemical interactions between the Al surface and sample, promoted by corrosive entities such as chloride ions and certain conditions of pH, can compromise the integrity of the cell and interfere with the experiment. In this study, the corrosion susceptibilities of Al and its alloys were investigated by subjecting them to various treatments; the results were compared with those of other candidate materials with low chemical reactivity. This work showed that alloys with higher Al content and boehmite-coated surfaces are resistant to corrosion. In particular, for Al, the resistance is due to a reduction in the contact area achieved by reducing the surface roughness. QENS measurements of empty sample cells made of these materials revealed two results: (1) the profile of the cell fabricated with a copper-free Al alloy showed a minor dependence on the scattering vector magnitude Q and (2) reducing the real surface area of Al effectively suppresses its scattering intensity, while boehmite coating strengthens the scattering. Cells fabricated with Mo, Nb and single-crystal sapphire can be used as alternatives to Al because of their low scattering intensity and reduced dependence on Q.

The present study deals with the adsorption mechanisms of methylene blue (MB) and formaldehyde (FA) in aqueous solution using cerium-doped activated carbon (Ce/AC). Firstly, the cerium-doped carbon...

Polyethylene terephthalate (PET) pre-prepared nano/micro fibers were treated by sodium hydroxide (NaOH) aqueous solution and then AgNPs were loaded on them through the soaking process. In total, eight samples were created. Then they were characterized by field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), X-ray energy diffraction (EDS) spectroscopy and Fourier transform infrared (FTIR). Disk diffusion and colony counting tests were also performed. Samples containing AgNPs had growth inhibition zones with diameters between 19 and 26 mm while control samples had no inhibition zone. PET microfibers containing AgNPs had a larger inhibition zone on Staphylococcus aureus compared to other samples. The innovation of this research is the placement of AgNPs on the hydrophilic PET micro/nano fibers.

The density, speed of sound and viscosity data of drug pentoxifylline in aqueous solutions of glucose (monosaccharide) and lactose (disaccharide) were determined. The various properties of the solutions were characterized and their structural features determined by varying the concentrations of solute and solvent at atmospheric pressure and at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15) K. Infinite dilution limiting apparent molar volume ( $$V_{\phi }^{0}$$ ) and limiting apparent molar isentropic compression ( $$K_{\phi ,S}^{0}$$ ) parameters and their variation tendencies were considered in terms of the interactions between solute and solvent. The transfer parameters ( $$\Delta_{{{\text{tr}}}} V_{\phi }^{0}$$ and $$\Delta_{{{\text{tr}}}} K_{\phi ,S}^{0}$$ ) were positive and increased with increase in the concentrations of glucose/lactose in aqueous medium. Limiting apparent molar expansivity ( $$E_{\phi }^{0}$$ ), Hepler’s constant $$\left( {{{\partial^{2} V_{\phi }^{0} } \mathord{\left/ {\vphantom {{\partial^{2} V_{\phi }^{0} } {\partial T^{2} }}} \right. \kern-\nulldelimiterspace} {\partial T^{2} }}} \right)$$ and hydration number (nH) were also evaluated. The viscosity data have also been evaluated using the Jones–Dole equation. The results, analyzed using spectroscopic data, are discussed and rationalized in terms of various interactions.

An online method involving transient electrokinetic dosing and ITP with neutralization reaction boundary (NRB) and/or carrier ampholyte-free isoelectric focusing (CAF IEF) was developed for the preconcentration, preseparation, and analytical determination of glyphosate in aqueous samples containing low concentrations of the analyte of interest. Various parameters were investigated in the framework of an optimization study with the aim of achieving the maximum concentration limit of detection (cLOD) decrease in minimum time. The proposed method used CAF IEF and/or ITP with NRB. The sample was dosed to the column on the stationary reaction boundary (CAF IEF) and/or moving reaction boundary (ITP with NRB), whereat a sharp pH step exists. Here, charge reversal was due to the ampholytes, and/or acid accumulation occurred because of charge loss. Similarly, the accumulated sample was mobilized with TE and analyzed using classical ITP in the second analytical column. Glyphosate (GLY), the analyte of interest, was chosen as a model substance for ITP with NRB and preconcentration as well as focusing preconcentration and CAF IEF using the asymmetric purpose-built NRB. On one side of the asymmetric boundary was the zone of acidic pH; while the opposite side comprised a neutral/basic non-conductive zone of the ampholyte-in this case, GLY. Such an arrangement enables the use of a lower pH on the acidic side, which allows the focusing of strongly acidic ampholytes and the accumulation of weak acids. The electrolyte composition and the dosing time were optimized, and a 14-fold accumulation was achieved in 25 min compared to that by classical ITP and a 180-fold accumulation was achieved through CAF IEF and preconcentration with a glyphosate sample. Both methods are simple and can be conducted using all commercial ITP systems.

Numerous research papers on biosorption have been published in the past four decades. This paper reviews and compares heavy metal uptake capacities of various biological and non-biological materials. Adsorption mechanisms and processes of heavy metal ions (HMIs) onto biomasses are summarised and discussed, respectively. In general, all types of adsorbents exhibit certain uptake capacities for HMIs, but the capacity values for different types of biomasses and non-biological materials vary significantly. For HMIs, the reported values for bacterial biomasses typically range from 0.06 mmol·g−1 to 2.84 mmol·g−1; for fungi and yeasts, 0.03 mmol·g−1 to 2.44 mmol·g−1; for fresh water algae, 0.02 mmol·g−1 to 3.15 mmol·g−1; for marine algae, 0.23 mmol·g−1 to 3.77 mmol·g−1; for other biological materials/derivatives, 0.01 mmol·g−1 to 1.78 mmol·g−1 and for non-biological materials, 0.003 mmol·g−1 to 2.40 mmol·g−1. Thereinto, a few macroalgal species exhibit much higher adsorption capacities for HMIs relative to other types of adsorbents. Statistical analysis of heavy metal uptake capacities of various biological and non-biological materials indicates that marine algae are most suitable for the development of industrial biosorbents for the remediation of diluted HMIs-bearing effluents. Biosorption mechanisms of HMIs by biomasses include physical adsorption, ion exchange, electrostatic interaction, surface complexation and inorganic microprecipitation. the physicochemical properties of biosorbents and HMIs as well as external adsorption conditions significantly influence the adsorption process of HMIs onto biomasses. It could be concluded from numerous previous studies that pseudo-first-order and pseudo-second-order models are the most commonly utilised to characterise adsorption process. Up to date biosorption of HMIs remains largely in the laboratory stage. Combining microscopic mechanisms with macroscopic models may be one of the future research directions for removal of HMIs by biomasses.

Nowadays the functional ice cream production keeps developing. Due to that the traditional composition of the ice cream is amended. In case of substitution of the low molecular weight nutrients (sucrose, lactose and mineral salts of dry skimmed milk residue) with technologically functional nutrients, it changes the cryoscopic temperature, which influences the parameters of production process, in particular the temperature of the ice cream getting from the freezer. In this regard, the problem of calculating the cryoscopic temperature of ice cream mixtures has become acute, since it is not possible to find this parameter experimentally at all food enterprises. While calculating the cryoscopic temperatures on the basis of existing reference data, in some cases the authors encountered a significant (more than 0.5 °C) deviation of the calculation results from the experimental data. In order to establish the cause of these deviations, the authors analyzed aqueous solutions of sucrose, fructose, trehalose, erythritol, maltodextrin, polydextrose, sorbitol, glucose-fructose syrup, dry glucose syrup, inulin in concentrations that provide for the cryoscopic temperatures of solutions within the range from 0 °C to minus 6 °C. The cryoscopic temperature of the solutions was measured by an osmometer-cryoscope, and the conventional molecular weight of the substances was calculated on the basis of Raoult ratio, taking into account the high molecular weight substances and admixed impurities. It was shown that the values of the conventional molecular weight for trehalose and sorbitol solutions differ by more than 15% from the values of chemically pure substances due to presence of low molecular weight monomers in their composition. The presented experimental data on the conventional molecular weight values can be used for calculation of cryoscopic temperature of various types of mixtures used for ice cream production. As an example of application of obtained clarified values of conventional molecular weights, this article provides a method for calculation of cryoscopic temperature of low sucrose and sucrose-free ice cream mixtures, as well as a comparison of the calculation results with experimentally obtained data.

In this work, the Pd@WO3 nanocomposites were prepared successfully and fabricated by a effortless, simple hydrothermal method. These nanocomposites were confirmed and characterised by different tec...