Papers by Keyword: Sorption Isotherm

Abstract: In the first stage. an integral saturation test of lignocellulosic materials was carried out on samples of wood under the control of a previously established theoretical basis. At the end of this test. parameters such as the porosity at saturation with water. the basal density. the total volume shrinkage. the linear shrinkages. the density at the saturation of the samples are deduced. The second stage of this work is based on the exploitation of the hot tape method to achieve the thermophysical properties of wood samples over a range of humidity levels from 0% to 60%. The last stage of this research consisted in developing in the laboratory a device for controlling the saturation rate of steam in order to determine the adsorption/desorption isotherms. the mass diffusivity and the water capacity of these same wood species at various temperature. The counting of the results resulting from these tests has pointed out. among other things. that gmelia arborea is a more hygroscopic. lighter and more thermally insulating wood than afzelia wood. It is also noted that the two species of wood have average shrinkage. anisotropy and nervousness suggesting good stability in service. It is also noticed that equilibrium moisture sorption by these species increases with increasing relative humidity at constant temperature. but decreases slightly as temperature increases at constant humidity. In short . this work reinforces the database on tropical woods by providing in particular more local measurements. allowing the reliable dimensioning of wooden structures.

Abstract: Humic substances are the main component of soil organic matter and they actively interact with substances in soils, including pollutants. Humic acid-clay mineral composite materials can be considered as prospective and low-cost sorbents for contaminant removal. The aim of this study is to develop clay mineral and humic acid composite materials and to characterise their possible applications. For this research, montmorillonite, kaolinite and bentonite were saturated with three types of humic substances: technical humic acid from lignite, humic substances extracted from raised bog peat (Latvia) and technical K humate from lignite. Obtained sorbents were characterized using FTIR. The sorption was characterised according to the chosen clay mineral and humic acid type and concentration. Comparing the influence of clay minerals and humic substances on humic matter sorption, it has been found that the sorbed amount of humic substances depend on chosen humic substances and/or clay mineral. Obtained sorbents were used for sorption of chlorpromazine. Results indicate that the most perspective sorbents for chlorpromazine removal are bentonite and bentonite modified with humic acid. However, montmorillonite-humic composites also can be used for removal of chlorpromazine from water.

Abstract: Construction and demolition waste (C&D) was employed as a raw material to synthesize sorbent by fusion-hydrothermal process in order to effectively use this type of waste material. The specific surface area and the cation exchange capacity (CEC) values of the sorbent were 308.2 m² g^-1 and 625.6 mmol/100 g^-1, respectively. It was found that the sorbent was quite effective for ammonium ion due to the high CEC value. The sorbent possessed high PFOS sorption capacities after load with cationic surfactant (Cetyltrimethyl Ammonium Bromide, CTAB), the sorption capacities of CTAB-modified sorbents enhanced with the increase of CTAB loading amount. This study provides an effective way for the C&D waste utilization.

Abstract: In order to develop high-performance carbon, the orthogonal test was used to optimize the conditions of modification. Meanwhile,the carbon as a carrier was modified with sodium carbonate solution under the optimal conditions.The amount of total surface acidic functional groups and BET surface were determined. And the adsorption behavior for phenol was inspected.The results show that under the conditions of Na₂CO₃ concentration of 1.5mol/l, soaking time of 2h, activated time of 3h and activated temperature of 500°C, the best removal rate could be obtained, the adsorption of phenol was155.83mg/g and improved 69.33% than the unmodified carbon’s. The BET surface of modified activated was 971.78m²/g and improved 4.44% than the unmodified carbon’s, the amount of total surface acidic functional groups reduced but the alkaline enhanced. Both Freundlich and Langmuir model of sorption isotherms could reflect the adsorption behavior of modified activated carbon for phenol, while the Freundlich model was more properly.

Abstract: Soy protein isolate/carboxymethyl chitosan/oleic acid (SPI/CMCH/O) blend films were prepared by solution casting. The effect of various oleic acid content (0, 2.5, 5.0, 10.0, 20.0 pph of SPI and CMCH) on water sorption isotherm of SPI/CMCH base film was investigated. The sorption isotherm of SPI/CMCH/O blend films was evaluated at serveral relative humidity (0, 16, 35, 55 and 76% RH), at 25±1°C. The isotherms showed equilibrium moisture content (%EMC) of SPI/CMCH/O blend films decreased when oleic acid content increased. Understanding of sorption isotherms is an importance for prediction of moisture sorption properties of films via moisture sorption empirical models. Guggenheim-Anderson-de Boer (GAB), BrunauerEmmettTeller (BET) and Oswin sorption models were tested to fit the experimental data. The root mean squares (RMS) of GAB, BET and Oswin were in the range of 68.60-87.02, 22.86-79.38 and 694.78-3797.23, respectively. BET model was found to be the better-fitted model for SPI/CMCH/O blend films at 25±1°C.

Abstract: A series of biodegradable superabsorbent polymers (SAP) based on starch grafted with acrylic acid (AA) and crosslinked with N,N’-methylenebisacrylamide (MBIS) were obtained. The parameters that define SAPs properties, such as starch type, amount of initiator, acrylic acid and crosslinker concentrations, and degree of neutralization were varied according to an experimental design. The swelling rate, the degree of swelling, the water sorption isotherms and the texture profile of the new materials were determined. A new method was used to measure the swelling rate. The water sorption results were correlated using various isothermal models as the BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Andersson-DeBoer) models. Hydrogels obtained from regular cornstarch presented better absorption capacities than those from waxy cornstarch. Maximum swelling was observed for 70% neutralization of carboxylic acid groups. More rigid SAPs presented lower swelling rates, but not necessarily lower swelling degrees.