Papers by Keyword: Desorption

Abstract: Borassus palm or aethiopium palmyra is a palm species tree, widely spread in sub-Saharan Africa but its fruits don’t have any economic value therefore considered as waste. This study investigated the potential of Borassus fruit fibers (BFF), extracted manually from the underutilized fruit, for various applications by examining their hygroscopic properties. Scanning electron microscopy (SEM) revealed the fibers' unique features, including a relatively large diameter and high affinity for water vapor. A Dynamic Vapor Sorption (DVS) analysis with exposure time varying from 1, 2, 4 until 72h and varied Relative Humidity (from 0 to 90%) with 10% increment was carried out to examine the Sorption-desorption behavior. The characteristic hysteresis behavior of natural fibers was observed, with significant moisture uptake, particularly above 70% RH. The sorption and desorption processes were quantified, revealing a linear relationship between mass change and relative humidity. Furthermore, an Ensemble learning approach, specifically a Gradient Boosting Regression (GBR) model, was developed to predict the hygroscopic behavior of BFF. Trained on the experimental sorption-desorption data, the GBR model demonstrated excellent predictive accuracy, achieving a high R² value of 91.7% and low CV, MSE, and RMSE values (6.9 and 2.6, respectively). These findings highlight the significant influence of relative humidity on BFF moisture content and demonstrate the effectiveness of GBR as a powerful tool for accurately predicting the complex hygroscopic behavior of these fibers.

Abstract: The adsorption behavior of Pb²⁺, Cu²⁺, and Cr³⁺ from aqueous solutions onto bacterial cellulose/magnetite (BC/Fe₃O₄) composite in multiple systems was systematically investigated, with particular focus on competitive adsorption and inorganic ion effects. The BC/Fe₃O₄ composite demonstrated significant adsorption capacity for the three heavy metals through mechanisms involving surface complexation and electrostatic interactions. Binary and ternary competitive adsorption studies revealed that the adsorption capacity followed the sequence of Pb²⁺ (0.847 mmol/g) > Cu²⁺ (0.673 mmol/g) > Cr³⁺ (0.556 mmol/g), correlating inversely with their hydration energies. The presence of inorganic ions (Na⁺, K⁺, Mg²⁺, Ca²⁺) showed inhibitory effects on heavy metal adsorption, primarily due to competition for adsorption sites. Conversely, Al³⁺ and Fe³⁺ enhanced adsorption performance through synergistic effects. Notably, Pb²⁺ adsorption remained relatively unaffected by competing ions due to its strong affinity for BC/Fe₃O₄, while Cr³⁺ showed unique behavior in competitive systems. EDTA demonstrated superior desorption efficiency compared to HNO₃, with efficiencies ranging from 61.2% to 68.4%. This study highlights the potential of BC/Fe₃O₄ composite as an effective adsorbent for heavy metal removal from complex water matrices.

Abstract: Water resources are crucial in any region's overall natural resource complex. This research focuses on addressing these pollution issues through water treatment processes. The primary objective of this study was to examine the adsorption of phosphates using both natural and synthetic adsorbents, particularly aluminosilicates. Under static and dynamic conditions, the research assessed the sorption characteristics of natural zeolite, specifically clinoptilolite obtained from the Sokyrnytsia mineral deposits. Results indicated that the adsorption of phosphates is more effective in acidic environments. It was observed that clinoptilolite exhibits a higher adsorption capacity for unsubstituted phosphates, which diminishes when alkali metal ions replace orthophosphoric acid. Additionally, the study highlighted the significant influence of pH levels on the sorption properties of clinoptilolite, especially about P₂O₅. The kinetic coefficients of the adsorption process were determined using experimental data and theoretical frameworks. Furthermore, mathematical modelling was employed to describe the adsorption dynamics of the active components by granular sorbents, effectively capturing the transient nature of diffusive-kinetic processes in complex, multicomponent systems. This research deepens our understanding of phosphate adsorption mechanisms. It provides valuable insights into optimising water treatment strategies using natural adsorbents, which could play a critical role in mitigating the effects of water pollution in the region. Zeolites derived from fly ash produced by the Dobrotvir thermal power plant have been synthesised and modified to enhance their properties. This study focuses on the characteristics of these zeolites, with a particular emphasis on thermogravimetric analysis, to understand their stability and performance under varying conditions. The adsorption capabilities of the natural zeolite were tested against common pollutants found in wastewater from meat-processing plants, specifically targeting ammonium and phosphate contaminants. Experimental data allowed for determining equilibrium adsorption capacities and corresponding isotherms were constructed at a standard temperature of 20°C. The results indicate that zeolite adsorbs phosphates more effectively than ammonia nitrogen. Further analysis revealed that clinoptilolite's adsorption capacity is higher when interacting with single-component systems but decreases when it simultaneously adsorbs two different substances from the solution. This decrease suggests competitive adsorption dynamics when multiple contaminants are present. Given the finite availability of natural zeolite resources, this research highlights the importance of synthesising synthetic zeolites as a sustainable alternative.

Abstract: Cooking oil saturation due to frequent use for frying will result in a higher fatty acid content. Activated carbon made from the banana peel (Musa acuminata) with micro-mesoporous specifications can absorb free fatty acids. Banana peels are pyrolyzed into charcoal then activated alkaline at a temperature of 650°C. Then the activated carbon is washed and mashed to obtain activated carbon powder as an adsorbent by batch. FTIR carried out adsorption analysis on cooking oil to reduce carboxylic acid in used cooking oil. The regeneration process is carried out using surfactants to save on the use of necessary materials so that they need to be recycled. The experimental results based on isothermic equilibrium show that the Freundlich model can describe the adsorption process well at 28°C with a maximum adsorption capacity of 10 mg/g. The lifespan of activated carbon can only be extended once regeneration, reaching an adsorption capacity of 65% of fresh activated carbon's ability.

Abstract: The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO₂ absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO₂ mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO₂ absorption, because they allow to remove more than 90 % of CO₂ from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO₂ desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO₂ fluxes (0.12-(STP)/(m²·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO₂ absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.

Abstract: Textile and dyeing wastewater is the major source of environmental water pollution all over the world, which has complex composition so that conventional methods are difficult to remove and degrade. Based on the relevant research, this paper proposes to add further treatment by using macroporous resins on the basic of the conventional treatment and explore the effects of the adsorption and desorption, such as the pH value, initial concentration of , temperature and the flow rate. The performance of six kinds of macroporous resins (DA-2, D280, DA201, D3520, AB-8 and DA-201) for the advanced treatment in the textile and dyeing wastewater has been evaluated. The adsorption and desorption properties of the contaminants, which tested by the six kinds of the macroporous resins in the textile and dyeing, have been compared. According to the results, D3520 resin holds the highest adsorption and desorption capacity. (15.6mg/g for adsorption capacity, 15.1mg/g for desorption capacity). The effects of the pH value, initial concentration of , temperature and the flow rate on removal of by D3520 macroporous resin have been tested. The results showed that the removal of increased with the pH value and initial concentration of COD increasing and the data of its adsorption fitted the Langmuir isotherm best. Besides, 92.49% could be removed after 8h of adsorption at 25 °C. Dynamic adsorption and desorption experiments have been carried out on the packed column of D3520 resins as a reference for engineering applications, the results showed that the D3520 resin could still reach 79.5% removal rate after adsorptions-regeneration for five times.

Abstract: Research on the adsorption of Cd (II) ion in dithizone-immobilized natural bentonite has been carried out. The aims of this research were focused on the preparation of dithizone-immobilized natural bentonite (BA-D) as adsorbent and desorption experiment of Cd(II) ion. The BA-D was prepared by adding dithizone (dissolved in toluene) into the activated natural bentonite. The adsorbents were characterized by FTIR and X-Ray Diffraction (XRD). This research showed that adsorption capacities of BA-A and BA-D were 1.70×10^‒5 and 2.77×10^‒5 mol g^‒1 (46% of increasing). According to desorption experiment, interaction between activated natural bentonite and Cd(II) ionwere performed by electrostatic interaction, formation of hydrogen bond and complex formation.

Abstract: Coarse BOF sludge is a waste originating from steelmaking production. The major phaseof this waste is zinc ferrite. BOF sludge for this study was obtained from the metallurgical industryfrom a process of gas treatment in an oxygen converter. The sorption of cobalt, manganese and nickelions was investigated in the sample of the deposited sludge in a batch of experiments. The sorptionprocess was evaluated using three types of isotherm models. The sludge sample was alkaline andconsisted primarily of X-ray amorphous compounds and crystalline Fe oxides. The adsorptionprocess showed that a high removal efficiency was achieved at a lower initial concentration of metalions. Moreover, the equilibrium of the sorption process was achieved after 72 hours. Subsequently,the desorption of these adsorbed ions was investigated. The results of this study indicate that theapplication of metallurgical waste as a sorbent is highly effective for the treatment of wastewater.

Abstract: With the use of nanotechnology, clay minerals, specifically montmorillonites, have been reengineered to be used in environmental remediation, especially in the treatment of mining wastewater containing hazardous heavy metal ions. The objective of this study is to assess the practicality of using iron-modified montmorillonite (Fe-MMT) nanomembranes in the removal of mercury using the adsorption process. The nanomembranes, which were synthesized via electrospinning, were subjected to mercury cyanide solutions during the batch adsorption set ups to determine the adsorption efficiency. During the subsequent elution tests, three factors– eluent type (CH₃COOH and C₆H₈0₇), eluent concentration (0.01 M and 0.05 M) and contact time (3 and 5 hours) – were tested. SEM images of the mats were acquired to study the structure of the adsorbent. HD XRF analysis was done to identify the ions present in the membrane, as well as the initial Hg concentrations, amount of remaining Hg in the wastewater after batch adsorption and amount of desorbed metal. Results showed that using the Fe-MMT nanomembrane as adsorbent material resulted to 61.74% removal of Hg in the mercury cyanide solutions with initial concentrations of 13.87 to 38.9 mg L^-1. Acetic acid exhibited better desorption results, with the highest efficiency of 31.36% (0.01 M, 5 h) compared to citric acid’s 7.40% (0.05M, 3 h).

Abstract: This study proposed the new method of preparing Mg-based composite by mixed powder Ni and Ti onto the surface of pure Mg ingot. The prepared method caused that hydrogen absorbing phase Mg₂Ni and catalytic phase NiTi generated and distributed regularly. The pure Mg ingot as the center and the powder Ni and Ti as cladding material on the surface were formed and sintered, in which the temperature range of generated alloy phase Mg₂Ni and NiTi was confirmed at first; according to the temperature range, the size of Mg₂Ni and NiTi crystal grains at 650°C and 850°C were analyzed and compared, respectively; The size of Mg₂Ni alloy phase at the surface and center was calculated by comparing the atomic radius of Ni, Ti to confirm that Mg₂Ni distributed on the surface due to the atom Ti replaced the atom Ni in Mg₂Ni to generate the alloy phase NiTi; the capacity of the hydrogen desorption reached 4wt% within 5min. The disadvantages that easy to chalking and difficult to activate in the conventional method were avoided and achieved the application of the multilayer composite material in hydrogen storage field.