Water Adsorption Isotherms of Amaranth (Amaranthus caudatus) Flour

Water sorption isotherms are unique for individual food materials and can be used directly to predict shelf life and determine proper storage conditions. In this context, the aim of this study was to determine the moisture adsorption isotherms of amaranth flour at 15℃, 25℃ and 35℃ in a range of water activity from 0.1 to 0.9. Experimental data were modeled using five equations commonly applied in the foods field. The goodness of the fit for each isotherm model was evaluated through the coefficient of determination, the variance due to error and the confidence interval of the estimated parameters. All models can predict the adsorption isotherms of amaranth flour, but the GAB equation gives a better understanding of the observed sorption behavior. Estimated adsorption monolayer water contents ranged from 6.4 g to 7.2 g of water per 100 g of dry material. It was observed by a weak dependence of water activity with temperature. For ensuring microbiological stability, water content in amaranth flour should not be higher than 13 g of water per 100 g of dry material.

Water adsorption performance of UiO-66 modified by MgCl_(2) for heat transformation applications

UiO-66 is a potential material for adsorption heat transformation(AHT)with high specific surface area,and excellent thermal and chemical stability.However,the low water adsorption capacity of UiO-66 in the low relative pressure range(0<P/P_(0)<0.3)limits its application in AHT.We prepare the UiO-66 modified by MgCl_(2)through using the solvothermal method and impregnation method,and study their water vapor adsorption performances and heat storage capacities.Attributed to the extremely high saturated water uptake and excellent hydrophilicity of MgCl_(2),the water adsorption performance of UiO-66 is improved,although the introduction of MgCl_(2)reduces its specific surface area and pore volume.The water adsorption capacity at P/P_(0)=0.3 and the saturated water adsorption capacity of the UiO-66(with MgCl_(2)content of 0.57 wt%)modified by the solvothermal method are 0.27 g/g and 0.57 g/g at 298 K,respectively,which are 68.8%and 32.6%higher than the counterparts of pure UiO-66,respectively.Comparing with pure UiO-66,the water adsorption capacity of the UiO-66(with MgCl_(2)content of 1.02 wt%)modified by the impregnation method is increased by 56.3%and 14.0%at the same pressure,respectively.During 20 water adsorption/desorption cycles,the above two materials show high heat storage densities(~1293 J/g and 1378 J/g).Therein,the UiO-66 modified by the solvothermal method exhibits the excellent cyclic stability.These results suggest that the introduction of an appropriate amount of MgCl_(2)makes UiO-66more suitable for AHT applications.

Modeling Water Adsorption and Retention of Building Materials From Pore Size Distribution

Water adsorption and capillarity are key phenomena involved during heat and moisture transfer in porous building materials.They account for interaction between solid matrix,liquid water and moist air.They are considered through Water Vapor Adsorption Isotherm(WVAI)and Retention Curve(RC)functions which are constitutive laws characterizing water activity within a porous medium.The objective of this paper is to present a water vapor adsorption and retention models built from multimodal Pore Size Distribution Function(PSDF)and to see how its parameters modify moisture storage for hygroscopic and near saturation ranges.The microstructure of the porous medium is represented statistically by a bundle of tortuous parallel pores through its PSDF.Firstly,the influence of contact angle and temperature on storage properties were investigated.Secondly,a parametric study was performed to see the influence of the PSDF shape on storage properties.Three cases were studied considering the number of modalities,the weight of each modality and the dispersion around mean radius.Finally,as a validation,the proposed model for WVAI were compared to existing model from literature showing a good agreement.This study showed that the proposed models are capable to reproduce various shapes of storage functions.It also highlighted the link between microstructure and adsorption-retention phenomena.

Atomically Precise Titanium–Oxo Nanotube with Selective Water Adsorption and Semiconductive Behaviors

We report the first example of carbon nanotube(CNT)-like assembly of the titanium(Ti)framework,Ti oxo inorganic cluster(Ti6O6)hexagonal rings into a titanium oxide(Ti–O)nanotube,prepared by ionothermal synthesis.As determined by single-crystal X-ray diffraction analysis,the Ti–O nanotube arrays,stabilized by sulfate ligands,assumed proper parallel alignment with each other and were separated by supramolecular interactions with surrounding EMIm(1-Ethyl-3-methylimidazolium)counter cations.Our stability studies indicated that the Ti–O nanotube obtained is indeed stable in air and various solvents.Also,it could maintain its structure upon heating to∼300°C.Moreover,inside the pores of the Ti–O nanotubes,a rare water molecules nanoconfinement behavior was observed at room temperature.Further,our current developed Ti–O nanotube arrays exhibited selective water adsorption over methanol and ethanol,showing potential applications for miscible solvents separations.Finally,these Ti–O nanotubes demonstrated typical semiconductive characteristics,with the electrical conductivity increasing four orders of magnitude,ranging from 3.15×10^(−10)–1.03×10^(−6)S/cm,as the temperature increased from 35 to 135°C.This work represents a milestone in constructing inorganic Ti–O nanotube arrays with atomically precise structural information for applications as visible-lightinduced photocatalysts,semiconductors,sensors,and optoelectronics.

Effect of Mg^(2+) content in ion-exchanged Shengli lignite on its equilibrium adsorption water content and its mechanism

Mg ion-exchanged samples were prepared with acid-washed Shengli lignite.The chemical composition of the ash of the raw sample was determined by X-ray fluorescence.The equilibrium adsorption water contents of samples were determined in a range of relative humidity.The ion-exchange process was characterized by FT-IR,ash content,and p H value.A possible mechanism is proposed for equilibrium adsorption water of ion-exchanged samples at different humidities.The extent of ion-exchange reaction between Mg2+and lignite is controlled by the concentration of Mg2+in Mg SO4solution.The effect of Mg2+on equilibrium adsorption water content varies with relative humidity and content of Mg2+.The factor that controls equilibrium adsorption water content at low relative humidity is water interactions with sorption sites,which are Mg2+–carboxyl group complex.At middle relative humidity capillary force between Mg2+–water clusters Mg+(H2O)nand capillary is more important.At high relative humidity,free water–free water interactions are more significant.

A simplified adsorption model for water vapor adsorption on activated carbon

A simplified model was developed to describe the water vapor adsorption on activated carbon. The development of the simplified model was started from the original model proposed by DO and his co-workers. Two different kinds of carbon materials were prepared for water vapor adsorption, and the adsorption experiments were conducted at different temperatures(20-50 °C) and relative humidities(5%-99%) to test the model. It is shown that the amount of adsorbed water vapor in micropore decreases with the temperature increasing, and the water molecules form larger water clusters around the functional group as the temperature is up to a higher value. The simplified model describes reasonably well for all the experimental data. According to the fitted values, the parameters of simplified model were represented by the temperature and then the model was used to calculate the water vapor adsorption amount at 25 °C and 35 °C. The results show that the model can get relatively accurate values to calculate the water vapor adsorption on activated carbon.

The Influence of Free Water Content on Dielectric Properties of Alkali Active Slag Cement Paste

The dielectric performance of alkali activated slag （AAS） cement paste was investigated in the frequency range of 1 to 1000 MHz. The experimental results showed the unstable dielectric properties of harden paste were mostly influenced by the fraction of free water in paste or absorbed water from ambient, but not including hydration water and microstructure. The free water was completely eliminated by heat treatment at 105 ℃ about 4 hours, and then its dielectric loss was depressed; but with the exposure time in air increasing, the free water adsorption in ambient air made the dielectric property of harden cement paste to be bad. The temperature and relative humidity of environment was the key factors of free water adsorption; hence, if the influence of free water on dielectric constant was measured or eliminated, the cement-based materials may be applied in humidity sensitive materials or dielectric materials domains.

INDIRECT VOLTAMMETRIC DETERMINATION OF TRACE SULFATE IN NATURAL WATERS WITH THE ADSORPTIVE COMPLEX WAVE OF LEAD(Ⅱ)-TETRAKIS (4-TRIMETHYLAMMONIUM PHENYL) PORPHYRIN

The indirect voltammetric determination of trace sulfate (2.0×10^(-6)～4.0×10^(-5) mol/L ) with the adsorptive complex wave of lead(Ⅱ)-tetrakis (4-trimethylammonium phenyl) porphyrin (PbTTMAPP) is reported.This method has been used for the analysis of natural waters with satisfactory results.

Computer study of the spectral characteristics of the disperse water methane system

The interaction of water clusters that adsorbed methane molecules with infrared radiation is studied by molecular dynamics. The presence of methane molecules in the disperse water system leads to an increase in absorption and emission of infrared radiation and a strong depletion of the Raman spectrum. In this case, the reflection coefficient of a monochromatic plane electromagnetic wave increases and its frequency spectrum significantly changes. The comparison of experimental data for similar characteristics of water, methane, or their mixtures is presented.

Efficient construction of calcium fluoride nanoaggregates for enhanced water vapor adsorption

Calcium fluoride(CaF_(2))is an ideal adsorbent for the dehydration of gaseous hydrogen fluoride(HF)containing water vapor.In this work,a novel CaF_(2)absorbent,spherical CaF_(2)nanoaggregates(NAs)with a closely packed structure,was proposed and efficiently fabricated by spray drying technology.As the building blocks of CaF_(2)NAs,the CaF_(2)nanoparticles(NPs)were prepared by the addition of excess calcium ions(Ca^(2+))or fluorine ions(F−)in the synthesis.The results indicated that the CaF_(2)NPs synthesized by excess Ca^(2+)and the corresponding NAs exhibited much better water vapor adsorption properties than their counterparts by excess F−,owing to higher zeta potentials.More importantly,whether excess Ca^(2+)or F^(−),CaF_(2)NAs had further enhanced water vapor adsorption capacity compared to primary CaF_(2)NPs,possibly owing to their unique nano-micro secondary structures and higher surface areas.This work has great potential in the development of high-performance absorbents for separating moisture from corrosive gas HF.

Density functional theory study on natural hydrophobicity of sulfide surfaces

Adsorption of water on sulfide surfaces and natural floatability of sulfide minerals were studied using density functional theory （DFT） method. All computational models were built in a vacuum environment to eliminate the effects of oxygen and other factors. H2O molecule prefers to stay with pyrite and sphalerite surfaces rather than water, whereas for galena, chalcocite, stibnite, and molybdenite, H2O molecule prefers to stay with water rather than the mineral surfaces. On the other hand, pyrite surface favors N2 more than water, while sphalerite surface cannot adsorb N2. These results show that galena, stibnite, chalcocite, and molybdenite are hydrophobic, while sphalerite is hydrophilic. Although pyrite has certain hydrophilicity, it tends to be aerophilic because the reaction of pyrite with H2O is weaker than pyrite with N2. Thus, pyrite, galena, chalcocite, stibnite and molybdenite all have natural floatability.

In situ DRIFTS study of hygroscopic behavior of mineral aerosol

In situ diffusion reflectance infrared Fourier transform spectroscopy was used to study the water adsorption on mineral oxides （SiO2, a-Al2O3, MgO, Fe2O3, TiO2）. The results showed that all the water adsorption isotherms were well fitted with the Brunauer-Emmett-Teller （BET）-Ⅲ type equation, with the calculated monolayers occurring at 24%-30% relative humidity. It showed that about 1-5 layers of water adsorbed on oxides surfaces in ambient relative humidity （20%-90%）. The measured deliquescence relative humidity of NaCl was （74 ± 1）%, which demonstrated that DRIFTS is a useful method for the study the hygroscopic behavior of mineral dust. In addition, the limits of DRIPTS were also discussed.

Comprehensive investigation on robust photocatalytic hydrogen production over C_(3)N_(5)

Carbon nitride has drawn numerous eyes in the past decade,whereas the photocatalytic performance is significantly limited by its wide band-gap(~2.7 e V for C_(3)N_(4))simultaneously.Recently,C_(3)N_(5)with narrower band-gap has been reported,however,a systematically investigation on its photoactivity for H_(2)production has not been reported.The present work demonstrates the synthesis of C_(3)N_(5)by thermal treatment of 3-amino-1,2,4-triazole,and the photocatalytic performance for H_(2)production of C_(3)N_(5)is investigated comprehensively.Photocatalytic H_(2)production rate of C_(3)N_(5)is~2.2 times higher than that of C_(3)N_(4) with 1.0 wt%Pt as co-catalyst,and series of experiments are carried out to explore the behind elements accounting for the high photoactivity.Combining the results of DRS,PL and photocurrent,it is found that C_(3)N_(5)possesses wider visible light absorption region,lower band-gap and quicker photogenerated e^(-)/h^(+)separation efficiency.Moreover,characterizations including in-situ DRIFTS are adopted to monitor the adsorption property of H_(2)O on C_(3)N_(5),which plays a significant role in surface water reduction reaction,and higher amount of adsorbed H_(2)O molecules on C_(3)N_(5)is confirmed.The present work exhibits new insights into the high photocatalytic performance of N-rich carbon nitride catalysts.

Degradation of indomethacin in river water under stress and non-stress laboratory conditions:degradation products,long-term evolution and adsorption to sediment

The pharmaceutical compound indomethacin is not totally removed in wastewater treatment plants,whose effluents flow into aquatic environments;concentrations in the 0.1-100 ng/L range are commonly found in surface waters,and its fate is unknown.Here,biological,photochemical and thermal degradation assays were conducted under stress and non-stress conditions to estimate its degradation rate in river water and establish its degradation products over time.The results revealed that direct sunlight irradiation promoted the complete degradation of indomethacin（2 μg/L） in less than 6 hr,but indomethacin was detected over a period of 4 months when water was kept under the natural day-night cycle and the exposure to sunlight was partially limited,as occurs inside a body of water.The biological degradation in water was negligible,while the hydrolysis at pH 7.8 was slow.Residues were monitored by ultra-pressure liquid chromatography/quadrupole time-of-flight/mass spectrometry after solid-phase extraction,and six degradation products were found;their structures were proposed based on the molecular formulae and fragmentation observed in high-resolution tandem mass spectra.4-Chlorobenzoic and 2-acetamido-5-methoxybenzoic acids were the long-term transformation products,persisting for at least 30 weeks in water kept under non-stress conditions.Furthermore,the degradation in the presence of sediment was also monitored over time,with some differences being noted.The adsorption coefficients of indomethacin and degradation products on river sediment were calculated;long-term degradation products did not have significant adsorption to sediment.

The role of water in methane adsorption and diffusion within nanoporous silica investigated by hyperpolarized 129Xe and 1H PFG NMR spectroscopy

Understanding the properties and behavior of water molecules in restricted geometries, such as the nanopores of rocks, is of interest for shale gas exploitation. We present herein ex situ and in situ nuclear magnetic resonance （NMR） studies on the effects of water on the adsorption and diffusion of methane in nanopores. Silica materials with one-dimensional pores of ZSM-22, MCM-41, and SBA-15, with pore sizes ranging from 0.5 to 6 nm, were chosen as models. Hyperpolarized （HP） 129Xe NMR results show that water adsorption does not affect the pore sizes of ZSM-22 and MCM-41 but reduces that of SBA-15. The presence of water suppresses methane adsorption; this suppression effect is stronger in smaller pores. The self-diffusion coefficients of methane within ZSM-22 and MCM-41 are not significantly influenced by the presence of water, as measured by ~H pulsed field gradient （PFG） NMR. However, within SBA-15, which has a pore size of 6 nm, the diffusion coefficient of methane increases as the amount of water adsorption increases, peaks, and then decreases to a constant value with further water adsorption. These experiments reveal the effects of the pore size and the presence of water on methane adsorption and diffusion in constrained spaces, which could have important implications for flow simulations of methane in shales.

A Method for Semi-quantitative Analysis of C-S-H Gel in a Blended Cement Paste

An amended method for accurate measuring the quantity of calcium silicate hydrate(C-S-H) in pure cement paste and blended cement paste by water adsorption was made, which based on R.A.Olson’s method. Two improvements to this method, such as using C-S-H gel by hydro-thermal synthesis as standard sample and the stoichiometry of C-S-H gel is partitioned based on hydration time and the amount of mineral admixture. The result of C-S-H gel content in pure cement paste and blended cement paste is higher than by R.A.Olson’s method.

Insights into the role of oxygen-containing functional groups on carbon surface in water–electricity generation

A deep understanding of the electricity generation mechanism from the interaction between water molecules and carbon material surfaces is attractive for next-generation water-based energy conversion and storage systems.Herein,an asymmetric generator was assembled based on functionalized carbon nanotubes films to investigate the relative contribution from various oxygen functional groups on carbon surface to the water-electrical performance.Experiments and calculations demonstrate that the electricity mainly originates from the water molecule adsorption by carboxyl groups and dissociation of functional groups on carbon surface,which leads to the formation of electrical double layers at interfaces.This device allows the electricity generation with a variety of water sources,such as deionized water,tap water,as well as seawater.In particular,the generator based on carboxyl carbon nanotubes can induce a voltage of over 200 mV spontaneously in natural seawater with the power density of about 0.11 mW·g^(−1).High voltages can be achieved easily through the series-connection strategy to power electronic products such as a liquid crystal display.This work reveals the dominant role of carboxyl groups in carbon-based water–electricity conversion and is expected to offer inspiration for the preparation of carbon materials with high electrical performance.

Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal

Powdered activated carbon（PAC） adsorption of two fishy odorants, trans,trans-2,4-heptadienal（HDE） and trans,trans-2,4-decadienal（DDE）, was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters（ΔG^0, ΔH^0, and ΔS^0） indicated an exothermic and spontaneous adsorption process. PAC dosage, p H, and natural organic matter（NOM） presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of p H had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at p H 9. The presence of NOM, especially the fraction with molecular weight less than1 k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did.

Possibilities of using silicate rock powder:An overview

This study evaluates the on use of crushed rocks(remineralizers)to increase soil fertility levels and which contributed to increase agricultural productivity,recovery of degraded areas,decontamination of water,and carbon sequestration.The use of these geological materials is part of the assumptions of rock technology and,indirectly,facilitates the achievement of sustainable development goals related to soil management,climate change,and the preservation of water resources.Research over the past 50 years on silicate rocks focused on soil fertility management and agricultural productivity.More recently,the combined use with microorganisms and organic correctives have shown positive results to mitigate soil degradation;to expand carbon sequestration and storage;and to contribute to the adsorption of contaminants from water and soil.In this article we show results obtained in several countries and we show that this technology can contribute to the sustainability of agriculture,as well as to reverse global warming.Although mineral nutrients are released more slowly from these types of inputs,they remain in the soil for a longer time,stimulating the soil biota.In addition,they are a technology to soluble synthetic fertilizers replace,since the few nutrients derived from such inputs not consumed by plants are lost by leaching,contaminating groundwater and water resources.In addition,conventional methods rely heavily on chemical pesticides which cause damage to soil’s microfauna(responsible for the decomposition of organic matter and nutrient cycling)and the loss of organic carbon(in the form of dioxide),which is quickly dispersed in the atmosphere.Silicate rock powders are applied in natura,have long-lasting residual effects and reduce greenhouse gas emissions.

Phosphate adsorption performance of a novel filter substrate made from drinking water treatment residuals

Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At p H 7.0, the maximum adsorption capacity of 1.03 mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31 mg/g at 35°C.Under both acidic conditions（part of the adsorption sites was consumed） and basic conditions（negative charges formed on the surface of NFS, which led to a static repulsion of PO43-and HPO42-）, the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25 mol/L Na OH. The activation energy was calculated to be above 8.0 k J/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process.