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Principles of adsorption and adsorption processes
... Adsorption can be divided into physical adsorption and chemisorption, with physical adsorption having a weak binding force, a relatively small heat of adsorption, and easy desorption. On the other hand, chemisorption is caused by chemical bonding between the adsorbent and the adsorbent, the adsorption is often irreversible, and the heat of adsorption is usually larger [16]. Adsorption differs from the absorption process in that the adsorption efficiency is mainly influenced by the specific surface area, selectivity, and regeneration characteristics. ...
In the face of global warming and the urgent need for CO2 reduction, carbon capture, utilization, and storage, technology plays an important role. Based on the traditional liquid-phase and solid-phase CO2 capture technologies, the liquid-phase ammonia and biochar CO2 capture technologies are reviewed with emphasis. A multiphase carbon capture technology that uses biochar to enhance the mass transfer-crystallization process of the new ammonia CO2 capture technology is proposed. High CO2 capture efficiency, limited ammonia escape, and low system energy consumption can be achieved through the orderly construction of three-dimensional graded pore channels and the directional functionalization of biochar. The intermediate products of CO2 captured by the ammonia process and the special agricultural waste rice husk components were considered. The use of rice husk-based biochar for CO2 capture by synergistic new ammonia method and the process regulation of intermediate products to prepare nano-silica to achieve high-value utilization of interstitial products of carbon capture. This technology may be important to promote the development of CO2 capture technology and CO2 reduction.
... Increase in the surfactant concentration causes its molecules aggregation, followed by the formation of the micelles, which causes it to adsorb in the form of mono or bilayer. To minimize surfactant adsorption on the reservoir rocks, we use surfactants that hold the same charge as the surface (Klein, 1985). The surfactant loss is influenced by numerous factors, including the solution's salinity and pH. ...
Oil recovery in modern fields is challenging due to the reservoir complexity and heterogeneity. The
need is to improve the efficacy of additives used in oil mobilization under higher pressure, temperature,
and salinity conditions. The nanoparticles provide improved and sustainable solutions for improving oil
recovery. Silicon carbide nanoparticle exhibits negligible agglomeration and impart higher thermal stability
to the displacing fluid for oil mobilization at higher salinity. The SIC nanoparticles are being used in
EOR Applications for the first time owing to their adsorption reduction potential and thermal stability
at elevated temperatures. The study estimates this nanoparticle's enhanced oil recovery potential using
electrical conductivity, surface tension reduction, and crude oil mobilization. The concentration of SDS was
varied from zero-4000 ppm and that of SIC from 100 ppm to 300 ppm. The solution's surface tension and
critical micelle concentration (CMC) conductivity were measured at elevated temperatures (30°C, 50°C,
and 70°C) with and without nanoparticles. The adsorption studies were performed for 72 hours with 10
wt% of sand added to the solution. The loss of surfactant onto the sand was calculated by studying the
variation electrical conductivity before and after adsorption. Surface tension reduces from 70.15 to 28.5
mN/m with increasing SDS and nanoparticles concentrations in the solution. The CMC values of the SDS
+SIC solution were lower than that of the independent surfactant system, even at higher temperatures of
70°C. SDS adsorption increased from 0.80 to 6.27 mg/g as the surfactant concentration increased up to 4000
ppm. It was reduced by about 10% and 20% for 100 ppm and 200 ppm of the nanoparticles. However, at
300 ppm, the agglomeration of nanoparticles renders them ineffective in controlling adsorption.
... Table 1 shows the relationship between the isothermal model parameters and K a ; the parameters calculated were the apparent thermodynamic parameters. The changes in adsorption enthalpy (ΔH), Gibbs free energy (ΔG), and adsorption entropy (ΔS) could be calculated according to the van't Hoff equation, Gibbs formula, and Gibbs-Helmholtz equation [34,35] using formulas (5)- (7): ...
The liquid foodstuffs such as edible oil products remain a problem of excessive aflatoxin B1 (AFB1) content. This paper focused on the preparation of magnetic mesoporous silica (MMS) from rice husk ash for the removal of AFB1 in oil system. The MMS preparation process, adsorption conditions, structural characteristics, and adsorption mechanism were investigated. The optimum conditions for MMS preparation were pH 11.0 and 80°C for 24 h. The characterization results showed that magnetic particles were successfully embedded in the MMS and had high responsiveness to a magnetic field, which was advantageous for recyclability. The MMS had ordered uniform channels with a specific surface area of 730.98 m²/g and pore diameter of 2.43 nm. The optimum adsorption conditions were 2 h at 20°C. For AFB1 with an initial concentration of 0.2 μg/mL, the MMS adsorption capacity was 171.98 μg/g and the adsorption rate was 94.59%. The MMS adsorption isotherm fitted the Langmuir model well under the assumption of monolayer AFB1 adsorption with uniformly distributed adsorption sites on the MMS surface. The maximum amount of AFB1 adsorbed according to the Langmuir isotherm was 1118.69 μg/g. A quasi-second-order kinetic model gave a better fit to the process of AFB1 adsorption on MMS. The values of ΔH (−19.17 kJ/mol) and ΔG (−34.09, −34.61, and −35.15 kJ/mol at 283, 293, and 303 K, respectively) were negative, indicating that AFB1 adsorption on MMS was a spontaneous exothermic process. The results indicated that MMS was a promising material for AFB1 removal in oil system, and this study will serve as a guide for practical MMS applications.
Heavy metal contamination has been a significant issue globally often interconnected with broader environmental and social factors. Biosorption, emerged as a potential solution to sequester heavy metal ions using range of ceramics and polymers lean towards natural polymers for sustainability. Among these natural polymers, keratin-based adsorbents have attained attention due to its structural features. Though numerous review articles have reported the use of keratin for adsorption of toxic pollutants and methods to develop materials with desirable physical, chemical, thermal and mechanical properties, the present review particularly discuss the structural–functional relation to explore the modification and tenability to improve its adsorption efficiency for heavy metals. Their interactions with functional groups present on keratin molecule and further, different extrinsic aspects such as extraction methods’ impact on removal efficiency of keratin and underlying mechanisms elucidated through various adsorption model employed by researchers is also discussed. This review also reports studies on improving the inherent heavy metal adsorption capacity of keratin by compositing with other polymers. Additionally, the functionalization of keratin molecule has been explored for not only improving the adsorption capacity but also the morphological characteristics of the materials developed. Overall, the article highlights the advancements in keratin-based materials as effective adsorbents for heavy metal removal from wastewater and the need for further research to optimize their properties and performance.
Water pollution has jeopardized human health, and a safe supply of drinking water has been recognized as a worldwide issue. The increase in the accumulation of heavy metals in water from different sources has led to the search for efficient and environmentally friendly treatment methods and materials for their removal. Natural zeolites are promising materials for removing heavy metals from different sources contaminating the water. It is important to know the structure, chemistry, and performance of the removal of heavy metals from water, of the natural zeolites to design water treatment processes. This review focuses on critical analyses of the application of distinct natural zeolites for the adsorption of heavy metals from water, specifically, arsenic (As(III), As(V)), cadmium (Cd(II)), chromium (Cr(III), Cr(VI)), lead (Pb(II)), mercury(Hg(II)) and nickel (Ni(II)). The reported results of heavy-metal removal by natural zeolites are summarized, and the chemical modification of natural zeolites by acid/base/salt reagent, surfactants, and metallic reagents has been analyzed, compared, and described. Furthermore, the adsorption/desorption capacity, systems, operating parameters, isotherms, and kinetics for natural zeolites were described and compared. According to the analysis, clinoptilolite is the most applied natural zeolite to remove heavy metals. It is effective in removing As, Cd, Cr, Pb, Hg, and Ni. Additionally, an interesting fact is a variation between the natural zeolites from different geological origins regarding the sorption properties and capacities for heavy metals suggests that natural zeolites from different regions of the world are unique.
Phytoremediation of arsenic-contaminated water was successfully conducted by means of the perennial fern Pteris vittate, which is an arsenic-hyperaccumulator plant able to grow in hydroponic cultures. In order to avoid the costs linked to the disposal of As-contaminated biomass, in this work, Pteris vittata waste roots were tested as a low-cost bio-adsorbent for the removal of methylene blue (MB) from water in a fixed-bed adsorption configuration. As a matter of fact, methylene blue can negatively impact the growth and health of algae and plants by blocking light from reaching them in water, which can alter their normal biological processes. Previous works have already shown the potentiality of such material toward the uptake of methylene blue; however, all the studies conducted were just focused on batch-mode experiments. In this work, column runs were carried out at 20 °C, evaluating the bed void fraction for each test and hence estimating the apparent density of the material (300 g/L). The breakthrough curves collected were fitted by means of a mathematical model based on the linear driving force (LDF) approximation to obtain information on the mass transfer mechanism occurring in the system. A relation for the product between the LDF mass transfer coefficient and the solid specific surface (kLDFas) with respect to the Reynolds (Re) dimensionless number was obtained (kLDFas=0.45Re). The range of validity of such expression was Re<0.025. Its applicability was deeply discussed: in such conditions, the technology is ready to be tested at larger scales.
In this study, the residual pods of the forest species Erythrina speciosa were carbonized with ZnCl 2 to obtain porous activated carbon and investigated for the adsorptive removal of the drug paracetamol (PCM) from water. The PCM adsorption onto activated carbon is favored at acidic solution pH. The isothermal studies confirmed that increasing the temperature from 298 to 328 K decreased the adsorption capacity from 65 mg g −1 to 50.4 mg g −1 (C 0 = 175 mg L −1). The Freundlich model showed a better fit of the equilibrium isotherms. Thermodynamic studies confirmed the exothermic nature (ΔH 0 = −39.1066 kJ mol −1). Kinetic data indicates that the external mass transfer occurs in the first minutes followed by the surface diffusion, considering that the linear driving force model described the experimental data. The application of the material in the treatment of a simulated effluent with natural conditions was promising, presenting a removal of 76.45%. Therefore, it can be concluded that the application of residual pods of the forest species Erythrina speciosa carbonized with ZnCl 2 is highly efficient in the removal of the drug paracetamol and also in mixtures containing other pharmaceutical substances.
This paper describes the corrosion inhibiting action of four new imidazolium-derived ionic liquids (ILs). Elements analysis, Infrared, TGA, ¹H-¹³C NMR, XRD and HSQC-NMR were used to confirm the molecular formula of ILs. The corrosion suppressive effectiveness was calculated using loss of mass and electrochemical experiments and ranged from 53 to 96%. Their adsorption on a steel substrate was precisely characterized using the Langmuir isotherm. Gibbs free energies vary from - 35.24 kJ mol⁻¹ to - 41.82 kJ mol⁻¹, indicating that ILs are adsorbing via physi-chemisorption scenario. SEM/EDX and FTIR were used to validate the process of adsorption of ionic liquids.
For the purpose of controlling the release of radioiodine to the environment in nuclear power plants, adsorption characteristics of elemental iodine and methyl iodide on the base carbon and 2%, 5% TEDA impregnated carbons were studied. The amounts of adsorption of elemental iodine and methyl iodide on the carbons were compared with Langmuir, Freundlich, Sips and Dubinin-Astakhov(DA) isotherm equations. Adsorption data were well correlated by the DA equation based on the potential theory. Adsorption energy distributions were obtained from the parameters of the DA equation derived from the condensation approach method. For the adsorption of methyl iodide and elemental iodine-carbon system, the DA equation can be well expressed by the degree of heterogeneity of the micropore system because the surface is nonuniform when its potential energy is unequal. The adsorption energy distribution wes investigated to find a surface heterogeneity on the carbon. The surface heterogeneity for iodine-carbon system is highly affected by the adsorbate-adsorbent interaction as well as the pore structure. The surface heterogeneity increases as a content of TEDA impregnated increases. The adsorption nature of methyl iodide on carbon turned out to be more heterogeneous than that of elemental iodine.
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