Comparison of Numerical HMT Codes to Simulate MBV Test of Hemp-Earth Composites

Bio-based and earth materials are growingly used for the building envelopes because of their numerous benefits such as slight environmental impact, great hygrothermal performances, effective regulation of the perceived indoor air quality and human comfort. In such materials, the phenomenon of mass transfer is complex and has a great impact on the performance of building envelope. Therefore, it is important to identify and understand the hygrothermal phenomena to be able to simulate accurately the envelope behavior. Nevertheless, the classical models that depict hygric transport within building materials seem not accurate enough for bio-based materials as they are simplified on several points of view. The correlation that exists between water content and relative humidity is mostly simplified and is modeled by a single curve, the hygric storage capacity is often overstated and the hysteresis is neglected. This paper deals with numerical study of hygric transfer within hemp-earth building material by using WUFI® Pro 6.5, a commercial software, and TMC code developed at the LGCGM (Moissette and Bart, 2009) . This code was validated regarding EN 15026 standard (Moissette and Bart, 2009) and has evolved over the years by integrating the hysteresis phenomena (Aït-Oumeziane et al., 2015). Thus, a significant enhancement of the numerical simulations on desorption phase was shown. This study investigates the simulation of MBV test performed on a hemp-earth material for which only the adsorption curve is known as input. Missing parameters (water vapor permeability and desorption curve) are fitted considering the first cycle of MBV test with TMC code. Then, MBV test is simulated with WUFI® Pro 6.5 and TMC code without and with hysteresis. The results highlight the need to include hysteresis to accurately simulate dynamic hygric phenomena, and show that it is possible to find missing parameters by fitting dynamic solicitations.

Damage risk assessment of building materials with moisture hysteresis

Heat and Moisture Transfer (HMT) simulations are used to evaluate moisture related damage risks in building envelopes. HMT simulations are commonly performed accepting the hypothesis of not considering the moisture hysteresis of materials. The results of HMT simulation of a timber wall with hysteresis are presented, and compared to the results of three simplified models, showing the effects of hysteresis on the simulation results and on the assessment of the risk of decay. Moisture content is the most influenced variable, while temperature and relative humidity are slightly affected. The wood decay risk analysis is performed using the simplified 20% moisture content rule. Similar temperature values and relative humidity values are calculated as simplified models, while the moisture content annual average values have differences up to 2.3%. The wood decay risk obtained with the simplified models could be overestimated if the simulation is performed using the desorption curve, while it could be underestimated with the adsorption curve. The best approximation is obtained with the mean sorption curve, while the desorption curve and the adsorption curve could be used to calculate the upper and lower boundary of the moisture contents respectively.

Influence of the isoelectric point of gelatin on its adsorption on nanosilica surface

The joint efforts of chemists, physicians and technologists conducting researches to create new medical sorbents and combined drugs based on nanosilica, which have not only a detoxifying effect, but also antibacterial, wound healing, hemostatic and other important properties. One of the stages of such a research is developing regulatory documentation. To control the quality of the sorbent, the method of point measurements is most often used, according to it, the amount of adsorption of the marker substance at the single point of the adsorption curve is determined. The suitability of sorbents based on nanosilicа for using is determined by the value of the adsorption capacity concerning to medical gelatin. No other requirements for the process of test adsorption of gelatin by the sorbent are given. although it is known that the adsorption of proteins depends on the pH of the solution. Its maximum value is reached at a pH value corresponding to the isoelectric point (pI) of the protein. Each protein can be characterized by its own isoelectric point. Domestic and foreign standards give only the value of “pH of aqueous solutions” of gelatin and do not contain the indicator “isoelectric point”. The aim of the work is to study the influence of the isoelectric point of gelatin on its adsorption on nanosilica surface at different pH to appreciate the suitability of conditions for determining the adsorption activity of medical sorbents based on nanosilica. The adsorption of three samples of gelatin was examined in the work: A – edible gelatin (pI = 4.3–4.8); B – that from the catalog “Merck” (pI = 4.3–4.8) and C – that from the catalog “Fluka” (pI = 7.5–7.7) on nanosilica surface in the pH range from 3 to 8. It has been shown that for samples A and B the dependence has a maximum at pH ~ 4.5–5; and for sample C, the adsorption increases monotonically with increasing pH. It was noted that at pH ~ 5 the adsorption values for all gelatin samples were approximately equal. The adsorption activity of nanosilica concerning to proteins determined from the isotherms and the method of point measurements is compared. It has been found that the adsorption value of gelatin A onto the nanosilica at Cinitial = 700 mg/100 ml is equal to the Aave value determined by the Langmuir isotherms. This fact verifies the applicability of the method of point measurements for nanosilica/gelatin system to characterize the pharmacological activity of nanosilica based sorbents.

Study on Desorption Experiment and Desorption Model of Deep Shale Gas Containing Water

In this work, the methane desorption isothermal curves at different water contents on deep sampled from Western Chongqing of China were measured at pressures up to 65 MPa and at 130°C by the volumetric method. In the first instance, the desorption increases with the decrease of pressure, the adsorbed gas desorbs slightly with decreasing pressures from 65 to 30 MPa. When the pressure drops to 30–20 MPa, the desorption rate increases rapidly with the decrease of pressure and the desorption curve begins to separate from the adsorption curve, resulting in desorption hysteresis. At last, when the pressure is lower than 20 MPa, the desorption increases almost linearly with the further decrease of pressure, but eventually there will be some adsorbed gas which cannot be desorbed to form residual adsorbed gas. After that, the isotherm desorption data of CH4 was fitted using the improved desorption model. The fitting results showed that the improved desorption model can be used to describe the desorption process of deep shale gas containing water and has a strong applicability. In addition, the critical desorption pressure increases with increasing water content. When the water content is lower than 1%, the effect of the water content on the desorption of deep shale gas increases rapidly with increasing water content, as well as when the water content is greater than 1%, the impact changes slowly.

A New Co-Crystal of Synthetic Drug Rosiglitazone with Natural Medicine Berberine: Preparation, Crystal Structures, and Dissolution

A co-crystal of rosiglitazone (Rsg) with berberine (Bbr), Rsg-Bbr, was prepared by the solvent evaporation method and characterized. The results showed that the electrostatic attraction existed between the nitrogen anion of rosiglitazone and the quaternary ammonium cation of berberine, and C-H···O hydrogen bonds were formed between Rsg and Bbr. In the crystal structure, rosiglitazone molecules stack into a supramolecular layer through π-π interactions while π-π interactions between berberine cations also result in a similar layer. The co-crystal presented a low moisture adsorption curve in the range of 0−95% relative humidity values at 25 °C. The improved dissolution rate of rosiglitazone in pH = 6.8 buffer solution could be achieved after forming co-crystal.

Layered Rare-Earth Hydroxide Unilameller Nanosheets: Synthesis, Characterization, and Adsorption

Unilameller nanosheets with a lateral dimension of one nanometer have been isolated from a colloidal solution of europium-containing layered rare-earth hydroxide (LRH) material by the flocculation method. The nanosheets were achieved by changing pH of the colloidal solution from 6.7 to 11.5. The resultant flocculated nanosheets show high efficiency in sorption of fluoride anions from aqueous media (40 mmol/g), providing a potentially useful sorbent material for water purification technology. The sorbent material is demonstrated to be reusable for at least ten times without a significant loss of adsorption efficiency. And the results fit the Langmuir adsorption curve, indicating the chemisorption nature of the nanosheets. Most importantly, the isolated nanosheets are expected to widen the applicability and flexibility in material synthesis using two-dimensional nanomaterials.

Sulfate sorption measured by a buffering index over a range of properties of soils from south Western Australia

Sulfate sorption by the soil affects the rate of sulfate leaching, which impacts on the availability of soil sulfate for plant uptake. In Australia, plant-available sulfur is measured using 0.25 M KCl heated for 3 h at 40°C to extract soil sulfur (SKCl40). This paper describes a technique referred to as a sulfate buffering index (SBI), which provides a measurement of sulfate sorption. SBI when combined with the estimates of the q and b parameters of the Freundlich equation, can be used to define a sorption curve. The equation is S = acb – q; where S is the amount of sulfate adsorbed (mg S kg–1), c is the equilibrium concentration of sulfate measured in solution (mg S L–1) and a, b and q are coefficients that describe the soil sulfate sorption curve. Coefficients S and c were measured using six sulfate solution concentrations ranging from 0 to 250 mg S kg–1. The adsorption curve was fitted using the modified Freundlich equation including setting of b = 0.41 and q = SKCl40 using recently collected soil samples. The modified Freundlich a coefficient or SBI was calculated as SBI = (S + SKCl40)/c0.41; where S and c were determined using 50 mg S kg–1 of added sulfate. The SBI ranged within 1–40. The SKCl40 was related to SBI below a depth of 10 cm (r2 = 0.71) but not for the 0–10 cm soil layer where S sorption was minimal.

Volumetric Measurements of Methane-Coal Adsorption and Desorption Isotherms—Effects of Equations of State and Implication for Initial Gas Reserves

This study presents the effects of equations of state (EOSs) on methane adsorption capacity, sorption hysteresis and initial gas reserves of a medium volatile bituminous coal. The sorption experiments were performed, at temperatures of 25 °C and 40 °C and up to 7MPa pressure, using a high-pressure volumetric analyzer (HPVA-II). The measured isotherms were parameterized with the modified (three-parameter) Langmuir model. Gas compressibility factors were calculated using six popular equations of state and the results were compared with those obtained using gas compressibility factors from NIST-Refprop® (which implies McCarty and Arp’s EOS for Z-factor of helium and Setzmann and Wagner’s EOS for that of methane). Significant variations were observed in the resulting isotherms and associated model parameters with EOS. Negligible hysteresis was observed with NIST-refprop at both experimental temperatures, with the desorption isotherm being slightly lower than the adsorption isotherm at 25 °C. Compared to NIST-refprop, it was observed that equations of state that gave lower values of Z-factor for methane resulted in “positive hysteresis”, (one in which the desorption isotherm is above the corresponding adsorption curve) and the more negatively deviated the Z-factors are, the bigger the observed hysteresis loop. Conversely, equations of state that gave positively deviated Z-factors of methane relatively produced “negative hysteresis” loops where the desorption isotherms are lower than the corresponding adsorption isotherms. Adsorbed gas accounted for over 90% of the calculated original gas in place (OGIP) and the larger the Langmuir volume, the larger the proportion of OGIP that was adsorbed.