Adsorption最新文献

Activated carbon (AC) has recently gained increasing attention for removing various contaminants from water. AC obtained by agroindustrial waste is considered one of the essential adsorbent materials, which plays a vital role in processes of adsorption in water purification and wastewater treatment. Given the extensive use of this material, it is essential to understand its entire production chain and environmental impact. In this work, banana peel waste (BPF) was submitted at NaOH activation followed by pyrolysis at 600 °C to produce activated biochar (BFAC), aiming to remove methylene blue (MB) from wastewater. BFAC was characterized by TGA, XRD, SEM, BET, and FTIR techniques. The influence of dye concentration (10, 25, 50, 100, 250, and 500 mg L^− 1) and zero point charge (ZPC) were investigated. Besides, a Life Cycle Assessment (LCA) was carried out to assess the environmental impacts of the developed process. BFAC presented a well-developed pore structure with a predominance of mesopores and macropores, which directly influenced the MB removal capacity. The highest efficiency for dye removal was 62% after 10 min to an initial concentration of 50 mg.L^-1. The adsorption isotherms were well defined by Langmuir, Freundlich, and Temkin isotherm models. The Langmuir model represented the best fit of experimental data for BFAC with a maximum adsorption capacity of 49.5 mg g^− 1. Regarding LCA, a prospective approach at the early stage of development was conducted to orient the transition from laboratory to industrial scale, aiming at providing a competitive CO₂-based technological route. The scenarios proposed suggest that this route is promising either from the life cycle assessment or the circular economy perspective. Thus, BFAC can be considered an adsorbent with great practical application for post-treatment wastewater effluents to remove contaminants.

Graphical Abstract

To anchor chelating groups with nitrogen and sulfur atoms on tannin, a novel adsorbent (tannin-thiosemicarbazide-formaldehyde resin) was prepared through Mannich reaction by using blank wattle tannin, thiosemicarbazide and formaldehyde as raw materials. The adsorption behaviour of Ag⁺ from aqueous solution on the resin was evaluated via batch adsorption experiments. Fourier transform infrared spectroscopy (FT–IR) and elemental analysis were applied to verify the successful immobilization. The surface morphology, thermal stability and pore structure of the resin were also characterized. The results showed that the adsorption isotherm of Ag⁺ for the resin was described well by the Freundlich model. Ag⁺ adsorption equilibrium was achieved within 180 min, and the kinetic data were better fitted by the pseudo-second-order kinetic equation than by the pseudo-first-order and intraparticle diffusion equations. The adsorption capacity first increased and then stabilized with increasing pH (ranging from 1.0 to 7.0), and the resin exhibited high selectivity towards Ag⁺ in relation to Pb²⁺, Cd²⁺, Ni²⁺ and Ca²⁺. After three regeneration and reuse cycles, the adsorption capacity reached 1.68 mmol/g (84.0% of removal efficiency). Based on the experimental results and findings from various characterization techniques, the mechanism of Ag⁺ adsorption onto the resin could be attributed to inner-sphere complexation and chelation between Ag⁺ and multiple electron-rich atoms ( N, O, and S), in which S atoms played the most important role.

This study presents the use of jabuticaba peel to create a biosorbent material for recovering cyanidin-3-glucoside (C3G), a valuable compound in anthocyanin-rich extracts. This approach tackles waste management, promotes a circular economy, and offers a sustainable alternative to traditional methods. The biosorbents were synthesized through a chemical activation using three different solvents: H₃PO₄, HNO₃, and KOH. Sample characterization was conducted through various techniques, providing a thorough and multi-faceted understanding of the material properties. The morphological results showed the development of rich porous structures and increased carbon concentrations after activation, enhancing the adsorption capacity of the synthesized materials derived from jaboticaba peel. The H₃PO₄-activated biosorbent outperformed commercial adsorbents. Granulometric and concentration studies identified optimal conditions, and colorimetric analysis confirmed effective C3G removal. Kinetic studies indicated an adsorption process reaching equilibrium within 9.0 h. The Avrami model suggested a complex adsorption mechanism and intraparticle diffusion, which revealed a two-step process involving external mass transfer and internal diffusion. Adsorption isotherms at different temperatures fit the Langmuir model, indicating favorable adsorption behavior. The thermodynamic analysis confirmed the viability of jabuticaba peel biosorbents for eco-friendly C3G removal due to spontaneous, endothermic adsorption processes. The reuse study demonstrated that the biosorbent maintained its adsorption capacity up to the fifth cycle. Additionally, the adsorption mechanism of C3G on H₃PO₄-activated biosorbent was identified, emphasizing cation-π interaction, pore filling, electrostatic attraction, van der Waals forces, hydrogen bonds, and π-π interactions at pH 2. This revealed a physisorption process with diverse intermolecular forces. This study further supports ecological waste management and the creation of economical biosorbents for anthocyanin recovery, valuable compounds applicable in pharmaceuticals, food, and nutraceutical industries.

Graphical abstract

The methane adsorption test on coal was conducted under three initial pressures of 0.50 MPa, 0.75 MPa, and 1.00 MPa using the coal bed adsorption simulation test system. The focus of this study is to analyze the evolutionary characteristics of CH4 pressure and coal seam temperature under three different initial pressures. The distribution law of methane gas pressure and coal seam temperature on the inner plane of a coal seam, as well as the coupling relationship between them, are studied by interpolating and plotting the collected data using MATLAB software. The results indicate that methane pressure decreases over time, while the coal seam temperature increases. There is no linear correlation between the decrease in pressure and the increase in temperature. When coal is adsorbed, the pressure and temperature in the central region are lower, while the temperature in the region with high pressure is higher. The distribution of pressure and temperature is synchronized. The higher the initial pressure, the higher the temperature of the coal seam, and the more methane is adsorbed by the coal. However, the strength of the coal's adsorption capacity cannot be simply measured by the magnitude of the pressure drop. The research content can be used as the basis for further investigation of the methane occurrence rule in coal seams and the evaluation of methane adsorption capacity of coal.

Solutions of uranium salts can be used as targets for the production of medical radionuclides to exclude the most troublesome stages of solid target processing and make the targets reusable. An industrial introduction of this technology for the production of ⁹⁹Mo requires further development of the technological process of molybdenum extraction using a stable selective sorbent, such as titanium dioxide. Solutions of uranium sulfate in sulfuric acid have proven themselves well at the stage of irradiation, but the adsorption behavior of molybdenum in this media has not been studied sufficiently. A negative effect of the background concentration of the sulfate ion on the efficiency of extraction is shown in this paper, and a kinetic analysis is carried out using Morris-Weber model of intraparticle diffusion. Experiments show that the sorption kinetics can be both positively and negatively affected by an increase in pH from 1.3 to 2.0 when using sorbents of similar composition. The proposed explanation considers the nature of functional groups existing on the surface of the sorbent to be a determining parameter. The negative Y-intercept of the kinetic plot is considered to be a result of relatively slow activation of adsorption centers by protonation. Based on these assumptions, the possibility of existence of active centers with high activation rate, strongly affected by pH, and active centers with low activation rate, less affected by pH, on titanium dioxide surface was postulated.

This study investigates the effects of different combinations of potassium hydroxide (KOH)–nitrogen (N₂₎/carbon monoxide (CO)/air activation on the low-temperature ammonia (NH₃) removal NO performance of coconut shell-activated carbon. KOH–N₂-combined activation resulted in expanded pores of activated carbon, while high temperatures caused structural collapse. While increasing the activation temperature induced larger average pore sizes, introducing nitrogen-containing functional groups on the surface positively affected the NO conversion rate. Furthermore, while KOH–CO₂-combined activation yielded activated carbon with denser and more ordered pore structures upon increasing activation temperature, a relatively large specific surface area and total pore volume were also observed. Introducing functional groups such as C = C on the surface yielded a higher overall NO conversion rate. Although KOH–air activation resulted in developed porous structures, some pore sizes were blocked, thereby yielding a smaller specific surface area. Nevertheless, introducing nitrogen-containing functional groups contributed to an overall increase in the NO conversion rate. Orthogonal experimental analysis revealed that activation time significantly impacted the physical activation process of KOH-activated carbon, followed by activation temperature, with activation gas minimally affecting the activated carbon structure and NO conversion rate. Notably, the optimal activation conditions included 1-h activated carbon activation in 3 mol/L of KOH, followed by 1-h CO₂ activation at 150℃.

In this study, a cesium ion imprinted polymer (Cs(I)-IIP) was prepared by free radical thermal polymerization using 18-crown-6-ether (18C6) as ligand, methacrylic acid (MAA) as functional monomer, and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent, which can be used for adsorption and separation of cesium ions from low-concentration solutions. The adsorption kinetic and isotherm results showed that the adsorption of Cs⁺ fitted to the pseudo-second-order kinetic model and Langmuir model, indicating that the adsorption of Cs⁺ on Cs(I)-IIP was the monolayer chemical adsorption. The maximum adsorption capacity was 84.21 mg·g^− 1. The selective adsorption properties are performed in Cs⁺, Li⁺, Na⁺, and K⁺ multicomponent systems. The results showed that the Cs(I)-IIP has a high selectivity in the presence of coexisting Li⁺, Na⁺, and K⁺, and the selectivity coefficients (K’) of Cs(I)-IIP for Cs⁺/Li⁺, Cs⁺/Na⁺, Cs⁺/K⁺ are 2.1, 1.56, and 1.33, respectively. The high adsorption capacity and selectivity are attributed to the introduction of imprinting technology to form specific Cs⁺ recognition adsorption sites, and the 18C6 cavity was easier to recognize Cs⁺ in the competitive adsorption process. Finally, the Cs(I)-IIP can be regenerated and reused for 10 times with the adsorption capacity only decreased by 8.1%, indicating that the polymer has good reuse performance.

The uncontrolled release of waste diclofenac with low biodegradability is considered to be a potential threat for the environment and creatures. To find effective solution for this issue, this study reports the adsorption performance of diclofenac sodium salt (DCF) by using activated carbon (EHAC) obtained from einkorn (Triticum monococcum L.) husk in aqueous solution under various circumstances. It was found that DCF adsorption on EHAC was highly solution pH dependent, and DCF adsorption by EHAC decreased with increasing adsorption temperature. Equilibrium data showed that fitted isotherm model with the experiment results of DCF adsorption on EHAC followed the order of Langmuir > Temkin > Freundlich > Dubinin-Radushkevich. Adsorption capacity of EHAC for DCF adsorption in aqueous solution was calculated to be 147.06 mg/g at 25 °C. The adsorption kinetic of DCF adsorption on EHAC was determined to obey the pseudo-second-order kinetic model. By utilizing FTIR and pH data obtained from DCF adsorption on EHAC, DCF adsorption mechanisms with some interactions such as π-π stacking, electrostatic interactions, and hydrogen bonding were suggested at diverse pH values. Additionally, intraparticle diffusion model was applied to kinetic results to further recognize the kinetic mechanism of DCF adsorption on EHAC. Furthermore, thermodynamic parameters for DCF adsorption on EHAC were calculated and evaluated, in which DCF adsorption process by EHAC was determined to be exothermic, spontaneous, and feasible.

Analysis of physicochemical properties and water treatment is vital for the environment and societal living standards. In this study, polyaniline (PANI)/enset fiber (EF), reduced graphene oxide/EF, and PANI/rGO/EF composites as adsorbent materials were prepared via facile in-situ chemical oxidative polymerization techniques. The as-synthesized materials were characterized using XRD, FTIR, UV-VIS, TGA, and SEM spectroscopy. Physical characterization revealed the deposition of PANI and rGO on the surface of EF, confirmed by the cloudy and wrinkled fibrous morphology observed in the SEM images. After physical characterization, the adsorption performance of the proposed materials was tested using the batch method. The results showed a maximum adsorption capacity (q_max) of Cu²⁺ and Pb²⁺ ions by PANI/rGO-coated EF was 10.11 mg/g and 13.4 mg/g, respectively, which is higher than that of pristine EF, PANI/EF, and rGO/EF. When all parameters were optimized, the adsorptive removal efficiency of PANI/rGO/EF composite material towards Pb²⁺ and Cu²⁺ ions was 99% and 97.77%, respectively. The Freundlich isotherm data for Cu²⁺ and Pb²⁺ showed a good fit with the experimental data (R² = 0.99 and 0.98), and Langmuir isotherm data for Cu²⁺ and Pb²⁺ (RL = 0.18 and 0.19), respectively. The pseudo-second-order kinetic isotherm was a better fit for physisorption, with R² = 0.99 for Cu2 + and R² = 1 for Pb²⁺. Therefore, the synthesized novel material PANI/rGO/EF shows remarkable adsorption performance compared to EF, PANI/EF, and rGO/EF, due to the doping-induced abundant active sites of the composite material, making it a promising candidate for wastewater treatment techniques.

Increasing demand for fossil fuels in worldwide leads to environmental issues. Fossil fuel containing nitrogen compounds is deactivating the industrial catalysts. There are several techniques for nitrogen removal such as hydrodenitrogenation, oxidative denitrogenation, and adsorptive denitrogenation, due to the restriction of the common method; Researchers have suggested metal–organic frameworks (MOFs) and MOF nanocomposite materials for adsorptive denitrogenation (ADN) and oxidative denitrogenation (ODN) of fuels in recent years. This review paper aims to investigate the adsorptive and oxidative denitrogenation of liquid fuels with MOFs-based catalysts. All catalysts including pristine MOFs, defected MOFs, active component-loaded MOFs, and MOF-derived carbonaceous materials are studied. The detailed mechanisms of different MOFs are investigated to further improvements and modifications to synthesis well catalysts for nitrogen compound removal from liquid fuels.