Papers by Keyword: Adsorption Kinetics

Abstract: Water pollution by heavy metals constitutes a significant environmental and health risk, necessitating efficient and reusable adsorbents. The current study investigates the application of inexpensive biopolymer chitosan to extract Ni²⁺ and Cd²⁺ ions from aqueous solutions. Material characterization using X-ray diffraction (XRD) showed the amorphous nature (absence of peak at 10°), and Brunauer-Emmett-Teller (BET) analysis exhibited the mesoporous surface area of 302.12 m²/g, suitable for the adsorption of metal ions. The Swan model was parameterized with batch-derived adsorption parameters (i.e., Qₘₐₓ = 220 mg/g for Ni²⁺, 226 mg/g for Cd²⁺) and successfully predicted packed-bed breakthrough curves at optimum pH (7 for Ni²⁺, 6 for Cd²⁺), with transport rates of 3.65 × 10^-11 m²/s (Ni²⁺) and 3.14 × 10^-11 m²⁺/s (Cd²⁺) for a 1.2 m column. The material retained over 95% removal efficiency after five regeneration cycles. These findings show the potential of chitosan for large-scale water treatment with high efficiency, model-driven design, and strong reusability.

Abstract: Graphene oxide has drawn attention globally as it emerged as a promising adsorbent material with enhanced adsorption of environmental pollutants due to its eco-friendly attributes, high surface area, and cost-effectiveness for mass production. This economical solution is a promising and potentially transformative approach to heavy metal removal, contributing to a cleaner and more sustainable future. In this study, unmodified and modified graphene oxide were examined for the removal of copper (II) ions in an aqueous solution. Modified Hummer’s method was utilized to synthesize the graphene oxide. The synthesized graphene oxide was then modified with N- trimethoxysilylpropylethylenediaminetriaceticacid (EDTA-silane), resulting in EDTA-modified graphene oxide (EGO). Batch adsorption tests were done for both adsorbents in order to determine the effects of various factors, such as pH, adsorbent dosage, and contact time. Additionally, in order to describe the adsorption behavior of the adsorption system, it was further fitted to isotherm and kinetic adsorption models. Results of adsorption study showed optimum adsorption for copper (II) ions was achieved at pH = 7, contact time = 45 min, and adsorbent dosage of 5 mg and 4 mg of unmodified graphene oxide (GO) and modified graphene oxide (EGO), respectively. The fundamental mechanism of both adsorbents was best explained by Langmuir isotherm model and the pseudo-second-order model, indicating that the adsorption system followed chemisorption. The adsorption capacity and maximum removal of copper (II) ions was 672.22 mg/g and 78.41% for GO, and 729.11 mg/g and 89.94% for EGO. The latter suggested that graphene oxide treated with EDTA-silane (EGO) has the higher capacity to adsorb copper (II) ions.

Abstract: The investigation of kinetics is crucial for optimizing the adsorption process, particularly in multicomponent systems where several adsorbates compete for active sites on the adsorbent particle. This study presents a novel approach to improve the pseudo-first-order and pseudo-second-order kinetic models by integrating a competition parameter. This parameter quantifies the influence of the adsorbate interaction on the adsorption process. Empirical data of binary adsorption involving doxycycline (DXC) and tetracycline (TTC) were used to validate the improved models. The results indicate that the adjusted pseudo-first-order and pseudo-second-order kinetic models effectively depict the adsorption kinetics when the R² values ​​approach unity. The competition factor, denoted by the parameter α, quantifies the degree to which one adsorbate affects the adsorption capacity of the other. This study indicates that the revised models offer a more thorough understanding of adsorption kinetics in multicomponent systems, thereby facilitating more effective selection of adsorbents and optimization of the process.

Abstract: The process of adsorption treatment of effluents from ammonium ions is considered as an integrated two-stage process consisting of the stage of adsorption of contaminants by natural sorbents in the apparatus with a stirrer and the liquid separation stage and solid phases. Mathematical models of ammonium ions adsorption from effluents by natural dispersed sorbents are proposed, based on the assumption that the process is described by Langmuir and Friendlich isotherms. The values of ion exchange equilibrium constants for different types of natural sorbents have been established by identifying experimental data for theoretical dependences. The obtained constants can be used to calculate the average concentration of ammonium ions in the solution and in the grain of the sorbent in the process of integrated adsorption process. Based on the analysis of the research results, the optimum method of the spent sorbent separation was selected - separation of the suspension of purified ammonium-containing effluents - spent sorbent under the action of gravity. Indicators of optimization of complex process of sewage treatment from ammonium ions are offered.

Abstract: Adsorption isotherms of Ni (II) and Cu (II) ions by alumino-silicates, modified with N, N'-bis (3-triethoxysilylpropyl) thiocarbamide (BTM-3), and HCl, were obtained. The adsorption kinetics of heavy metal ions is studied, using the kinetic pseudo-first and pseudo-second order models. It is shown that, when alumino-silicates are modified, the rate and energy of adsorption increase. It is established that the kinetics of the adsorption of the studied ions is best described by a pseudo-second order model. The maximum value of the adsorption rate constant of 33.7∙10^-5 g/ (mmol min) corresponds to nickel (II) ions for alumino-silicates, modified with HCl. The maximum value of the adsorption rate constant value of 2.91∙10^-5 g/ (mmol min) for alumino-silicates, modified with BTM-3, corresponds to Cu (II) ions.

Abstract: Heavy metal adsorption (HMA) is one of the remediation techniques used to remove heavy metals from water/wastewater. Composite membranes with functionalized additives for selective adsorption are being investigated. In this study, Carbon Quantum Dots – Polyacrylonitrile/Polycaprolactone nanocomposite membranes are synthesized by electrospinning which is intended for HMA of Cu²⁺. The nanofiber mats were characterized using SEM, FTIR, and Contact Angle. Batch adsorption process were performed and to utilize the AAS for kinetic adsorption behavior analysis. SEM micrographs revealed the addition of CQD in PAN and PAN/PCL membrane matrix shifted the fiber size distribution from 50 – 100 nm to 150 – 250 nm indicates the decrease in effective surface area. FTIR analysis exhibited vibrational peaks and binding of distinct functional groups such as amine, nitrile, carboxylic, hydroxyl, and carbonyl for CQD, PAN and PCL, respectively. CQD in aqueous form further increases the hydrophilicity of PAN/PCL membrane matrix which is essential for HMA of Cu²⁺ ions. The increase of nanofiber mat’s adsorption capacity with respect to contact time obtained a maximum at 63.45 mg/g with a maximum efficiency of adsorption at 90.74%. Kinetic adsorption studies show that the pseudo – first order kinetic model best fits the data for CQD – PAN/PCL nanofiber mat in Cu²⁺ ions obtaining a correlation value of R² = 0.9418 and a rate constant k = 0.0172 min¹ indicating the adsorption behavior follows the physical adsorption process involving Van der Waals forces and hydrogen bonding between the adsorbent and adsorbate.

Abstract: This work was focused on the removal of sulfur compounds via adsorption process from heavy naphtha using alkali agents-activated carbon nanotubes (ACNTs). Commercial CNTs were activated using three alkali agents (KOH, NaOH, and CaCl₂) to amend their surfaces for application in the petroleum industry. The characterization of the physicochemical properties of as-received CNTs and CNTs/alkali agents was performed using a scanning electron microscope (SEM), N₂ adsorption/desorption isotherm, and Fourier transform infrared spectroscopy (FTIR). The effects of three operating conditions including adsorbent dosage (1-3 g), agitation speed (330-1500 rpm), and contact time (30-70 min) on the removal efficiency of sulfur compounds at constant pressure and temperature were investigated. Studying of the removal efficiency at different operating conditions was adopted to effectively evaluate the surface modifications of adsorbents on the present process. The specific surface areas of the CNTs were found to be increased upon treatment with alkali agents especially KOH and NaOH. SEM images demonstrated the formation of many defects on the CNTs surface due to the strong etching effect of both alkali agents KOH and NaOH. FTIR spectra showed different relative intensities around band 3440 cm^-1 for CNTs/KOH and CNTs/NaOH which was potentially attributed to the presence of hydroxyl functional groups. The sulfur removal experiments from heavy naphtha (initially had a sulfur concentration of 350 ppm) showed that the largest sulfur removal efficiency and adsorption capacity were 69.6% and 6.6 mg/g adsorbent respectively and obtained with CNTs/KOH which presented a superior adsorption efficiency over others. The highest sulfur removal efficiency was gained at adsorbent dosage=3 g, agitation speed=1500 rpm, and contact time=70 min. The study of adsorption kinetics demonstrated that the adsorption of organosulfur compounds from heavy naphtha obeyed the pseudo-second order kinetics

Abstract: The oligodynamic property is a lethal effect which some atoms exert over bacteria, fungi and other microorganisms. The oligodynamic property can be promoted by glass microparticles doped by zinc ionic specimens utilizing the ionic exchange processes. This study is aimed at modelling the behavior of adsorption mechanisms of the zinc ions on glass microparticles absorbent, with potential use as antimicrobial material. Aqueous solutions of zinc nitrate were used as the ionic supplying of zinc ions. The amount of zinc adsorbed on the glass was determined by spectroscopy of atomic absorption and with a mass balance analysis for each adsorption conditions. The experimental data were modeled by three Eq.s employed in adsorption kinetics studies: pseudo first order, pseudo second order and Elovich Eq.. The pseudo second order data model presented the better adjust condition. A sample of zinc glass microparticles, prepared at the finest conditions established by the kinetic model of pseudo second order, was submitted to microbiological analysis: agar diffusion test with Pseudomonas aeruginosa and Staphylococcus aureus and with Candida albicans. The glass doped with ionic zinc inhibited the growth of microorganisms in every conducted analysis.

Abstract: This research aimed to study the preparation of activated carbon from sugarcane bagasse waste. The sugarcane bagasse adsorbent was prepared by calcination at 600°C for 2 hours with the use of sulfuric acid (H₂SO₄) as a chemical activation. The adsorption surface possessed high specific surface area (838 m²/g) with mesoporous diameter. Factors explaining adsorption including adsorption isotherm, adsorption kinetic and adsorption mechanism were constructed from methylene blue adsorption experiments. It was found that the equilibrium data was best represented by Freundlich isotherm, showing multilayer coverage of dye molecules at the outer surface of adsorbent with a cooperative adsorption (physisorption and chemisorption). The kinetic of methylene blue adsorption was found to follow pseudo-second-order rate kinetic model, with a good correlation coefficient. This indicated that the overall rate of the dye adsorption process was controlled by the chemisorption process.

Abstract: Ground oyster shells were calcined and used as an adsorbent to remove As (III) from contaminated water. Adsorption experiment was performed by batch tests. The effect of pH on the adsorption performance was investigated. The result showed that at the initial concentration of 100 mg/L, over the pH range of 5-11, the highest efficiency was obtained at pH 11. The experimental data better correlated with pseudo-second order model. The maximum adsorption capacity (q_m) of approximately 195.5 mg/g was obtained at pH 11.