Adsorption Kinetic Studies Research Articles

Adsorption equilibrium, kinetic, and thermodynamic studies on the removal of paracetamol from wastewater using natural and HDTMA-modified clay

In this study, the adsorption efficiency of low-cost raw and modified clay was investigated. The modified clay was characterized through various technics including X-ray diffraction, XRF spectroscopy, FT-IR spectroscopy, and Electron microscopy SEM to analyze the evolution of raw clay structure and morphology. Paracetamol was chosen as an adsorbate to evaluate the removal performance from the aqueous medium. Factors influencing the uptake of paracetamol, such as pH, equilibrium time, adsorbent dosage, and initial concentration of paracetamol, were examined. The results obtained showed that the raw clay was successfully modified by HDTMA, which increased adsorption capacity thanks to new hydrophobic interaction. The adsorption of paracetamol on the modified clay reached equilibrium at a contact time of 120 min. Isothermal and kinetic models used in this study showed that the adsorption followed the Langmuir-isotherm and pseudo-second-order kinetic models. The maximum experimental adsorption capacity predicted by Langmuir model is about 112.63 mg/g, which is much higher than that obtained for the unmodified sample (62.11 mg/g). These results show that modified natural Moroccan clay can be used as low-cost and eco-friendly adsorbent nanomaterials to remove emerging pharmaceutical contaminants from water.

Scallop shells as biosorbents for water remediation from heavy metals: Contributions and mechanism of shell components in the adsorption of cadmium from aqueous matrix

To ascertain their potential for heavy metal pollution remedy, we studied the adsorption mechanism of cadmium onto scallop shells and the interactions between the heavy metal and the shell matrix. Intact shells were used to investigate the uptake and diffusion of the metal contaminant onto the shell carbonatic layers, as well as to evaluate the distribution of major and trace elements in the matrix. LA-ICPMS measurements demonstrate that Cd is adsorbed on a very thin layer on the inner and outer surfaces of the shell. Structural and thermal analyses showed the presence of 9 wt.-% of a CdCO3 phase indicating that the adsorption is mainly a superficial process which involves different processes, including ion exchange of Ca by Cd. In addition, organic components of the shell could contribute to adsorption as highlighted by different metal uptake observed for shells with different colours. In particular, darker shells appeared to adsorb more contaminant than the white ones. The contribution of the organic shell components on the adsorption of heavy metals was also highlighted by the element bulk content which showed higher concentrations of different metals in the darker specimen. Raman spectroscopy allowed to identify the pigments as carotenoids, confirmed by XRD measurements which highlighted the presence of astaxanthin phases. The results presented here provide new insights into the Cd adsorption mechanism highlighting the important contribution given by the organic components present in the biogenic carbonate matrix. Furthermore, the high efficiency of Cd removal from water by scallop shells, supported by adsorption kinetic and isotherm studies, has been demonstrated.

Adsorption of Cadmium (II) Ions Using Cassava Peel Activated Carbon: Study of Adsorption Kinetics, Isotherms and Thermodynamics

Heavy metals Cd2+ is a dangerous pollutant of water and ecological systems if it is above the quality standard threshold. Cassava peel has a fairly high carbon element content, namely 59,31%, so it can be used as an activated carbon to break down Cd2+ metals ions in water. This research aims to determine kinetic modeling and adsorption isotherms of Cd2+ ions using CPAC activated by H3PO4, determine the optimum pH and temperature conditions for Cd2+ ion adsorption and determine the adsorption capacity of Cd2+ ions using CPAC activated by H3PO4. CPAC is made through a carbonization process at a temperature of 500 °C for 1 hour. Next, it was impregnated with H3PO4 at a concentration of 30 % with a ratio of 1:5 (w/w) for 24 hours and physically activated at a temperature of 600 °C for 1 hour. Based on research, kinetic modeling and adsorption isotherms of Cd2+ ions using CPAC activated by H3PO4 following Pseudo-Second-Order (PSO) kinetic modeling and Freundlich isotherm, the optimum pH and temperature conditions for Cd2+ ion adsorption were obtained at pH 5 and temperature 25 °C. Thermodynamic parameters such as Gibbs energy (∆G°), enthalpy (∆H°), and entropy (∆S°), have been evaluated and indicate physical, spontaneou, and exothermic adsorption processes. The adsorption capacity of Cd2+ ions using CPAC activated by H3PO4 is 5.2219 mg/g.

Removal of hexavalent chromium in water by chitosan-modified Enteromorpha prolifera biochar loaded with iron-manganese oxides: Application performances and reaction mechanisms

This study successfully synthesized magnetic iron-manganese biochar (F1M3BC) and iron-manganese chitosan biochar (Chi-F1M3BC) using Enteromorpha prolifera (EP) as the raw material, aiming to efficiently remove hexavalent chromium (Cr(VI)) from water. Compared to F1M3BC, Chi-F1M3BC, after chitosan cross-linking encapsulation, exhibited significant advantages in terms of specific surface area, pH adaptability, and adsorption performance. The specific surface area of Chi-F1M3BC reached 101.47 m³/g, approximately double that of F1M3BC (52.89 m³/g), making it rich in reactive groups for Cr(VI) removal. The addition of chitosan elevated the pHpzc value of Chi-F1M3BC from 5.5 to 9, and the abundant active groups enabled it to efficiently remove Cr(VI) over a wider pH range. Under 30 °C conditions, 0.5 g/L of Chi-F1M3BC could completely remove 30 mg/L of Cr(VI) solution within 1 h. Adsorption isotherm and kinetic studies indicated that Chi-F1M3BC complied with the Langmuir model and pseudo-second-order kinetics. At 30 °C, the adsorption capacity of Chi-F1M3BC reached 104.5 mg/g, approximately twice that of F1M3BC (58.93 mg/g). Moreover, after five consecutive usage cycles, the removal efficiency of Cr(VI) by Chi-F1M3BC only slightly decreased by 3%, demonstrating its superior stable removal performance. Subsequent characterization and experimental investigations elucidated the elimination of Cr(VI) by Chi-F1M3BC, achieved through the synergistic interplay of ion exchange, electrostatic attraction involving surface hydroxyl and amino functional groups, chelation, and the reduction of iron and manganese oxides. In conclusion, the synthesized Chi-F1M3BC has demonstrated its efficiency and stable adaptability in removing Cr(VI), coupled with the additional benefit of utilizing waste Enteromorpha prolifera.

Influence of smectite clays' pores volume on isoniazid adsorption and release

Clays have been extensively utilized in various fields due to their remarkable adsorption properties. In pharmaceutical and medical applications, they serve as potential excipients in pills. Emerging research demonstrated their effectiveness as vehicles for controlling drug release. Little has been elucidated, however, regarding the optimal clay characteristics for such applications. Therefore, this study aimed to investigate the influence of clay pores volume on the adsorption of isoniazid (INH), a key drug in tuberculosis treatments worldwide. To achieve this, seven clays were investigated to examine the impact of pores volume on the adsorption and release of INH. Chemical characterization of the clays was conducted using X-ray fluorescence (XRF) and Infrared vibrational spectroscopy (IR), while their mineralogical composition was determined through X-ray diffraction (XRD) and their pore volume by BET method via N2 adsorption/desorption isotherms. Additionally, the interaction between clay and INH was evaluated using FT-IR, XRD, and Thermogravimetric Analysis (TGA). Kinetic adsorption studies were performed to determine the time to reach the equilibrium saturation of the clay by the drug, which was found to be around three hours for all clays. By comparing the pore volume of the studied clays, it became apparent that the clay with an optimal pore volume of approximately 0.100 cm3/g exhibited superior adsorption/retention compared to those with lower or higher volumes. Furthermore, in vitro INH release curves were obtained mimicking release conditions in the intestine (pH 7.4) for a duration of 5 h. It was clearly shown that the release of INH from the clays depend on the pore volume. Our results provided valuable insights into the optimal clay characteristics which would enhance the adsorption and release of INH.

Adsorption equilibrium, kinetics and dynamic process of polyphenols from orange peel extract on mixed‐mode adsorption resin HD‐1

AbstractBACKGROUNDThe extraction and separation of natural polyphenols are attractive. Many researchers used high‐speed counter‐current chromatography to separate and purify polyphenols. However, it requires a long operating time, a large amount of organic solvent consumption, and high operating costs. In this work, the adsorption behaviors of polyphenols from orange peel extract on mixed‐mode resins were studied. The adsorption capacities and selectivities of different resins to the main polyphenols in the extract including gallic acid, p‐coumaric acid and ferulic acid were compared. The adsorption mechanism was analyzed by adsorption equilibrium and kinetics studies as well as molecular docking. The fixed‐bed adsorption was studied experimentally and theoretically.RESULTSHD‐1 resin has excellent adsorption selectivities among the resins. The yield of polyphenols from orange peel by integrated extraction‐adsorption increased by 82.94% compared with that of extraction without adsorption. The adsorption isotherms agreed with the Freundlich model. Dubinin–Radushkevich model results indicated that the adsorption of gallic acid mainly depends on nonelectrostatic interaction. The adsorption of the other two polyphenols involves electrostatic and nonelectrostatic interaction. The adsorption kinetics curves accorded with the pseudo‐second‐order model, and the adsorption rate of gallic acid was the highest among the polyphenols. Adsorption of polyphenols involves both physical and chemical adsorption. The breakthrough curves could be closely simulated by Yoon–Nelson and Thoms models. Significant differences existed in times for 50% breakthrough.CONCLUSIONMixed‐mode chromatography with HD‐1 resin as stationary phase is applicable to the separation of polyphenols. © 2024 Society of Chemical Industry (SCI).

Enhanced Adsorption of Methylene Blue Dye on Functionalized Multi-Walled Carbon Nanotubes.

Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, XPS and DLS measurements a multi-walled carbon nanotube (MWCNT) derivative bearing benzenesulfonate groups (MWCNT-S). The obtained material demonstrated to have good dispersibility in water and better capability to adsorb methylene blue (MB) compared to the pristine MWCNT adsorbent. Adsorption kinetic studies showed a very fast process, with a constant significantly higher with respect not only to that of the unfunctionalized MWCNT adsorbent but also to those of widely used activated carbons. Moreover, the adsorption capacity of MWCNT-S is more than doubled with respect to that of the insoluble pristine MWCNT adsorbent, thanks to the dispersibility of the derivatives, providing a larger available surface, and to the possible electrostatic interactions between the cationic MB and the anionic sulfonate groups. Additionally, the reversibility of ionic interactions disclosed the possibility to release the adsorbed cationic pollutant through competition with salts, not only regenerating the adsorbent, but also recovering the dye. Indeed, by treating the adsorbed material for 1 h with 1 M NaCl, a regeneration capacity of 75% was obtained, demonstrating the validity of this strategy.

Biomimetic Mineralization Synthesis of Flower-Like Cobalt Selenide/Reduced Graphene Oxide for Improved Electrochemical Deionization.

Rationally and precisely tuning the composition and structure of materials is a viable strategy to improve electrochemical deionization (EDI) performances, which yet faces enormous challenges. Herein, an eco-friendly biomimetic mineralization synthetic strategy is developed to synthesize the flower-like cobalt selenide/reduced graphene oxide (Bio-CoSe2/rGO) composites and used as advanced sodium ion adsorption electrodes. Benefiting from the slow and controllable reaction kinetics provided by the biomimetic mineralization process, the flower-like CoSe2 is uniformly constructed in the rGO, which is endowed with robust architecture, substantial adsorption sites and rapid charge/ion transport. The Bio-CoSe2/rGO electrode yields the maximum salt adsorption capacity and salt adsorption rate of 56.3mg g-1 and 5.6mg g-1 min-1 respectively, and 92.5% capacity retention after 60 cycles. These results overmatch the pristine CoSe2 and irregular granular CoSe2/rGO synthesized by a hydrothermal method, proving the structural superiority of the Bio-CoSe2/rGO composites. Furthermore, the in-depth adsorption kinetics study indicates the chemisorption nature of sodium ion adsorption. The structures of the Bio-CoSe2/rGO composites after long term EDI cycles are intensively studied to unveil the mechanism behind such superior EDI performances. This study offers one effective method for constructing advanced EDI electrodes, and enriches the application of the biomimetic mineralization synthetic strategy.

Green Synthesis Derived Novel Fe2O3/ZnO Nanocomposite for Efficient Photocatalytic Degradation of Methyl Orange Dye

Introduction: An eco-friendly method was reported for the synthesis of ferric oxide nanoparticles (Fe2O3), zinc oxide nanoparticles (ZnO) and Fe2O3/ZnO nanocomposite using Mangifera indica plant leaf extract as a natural reducing agent. Methods: The synthesized nanomaterials were successfully characterized by X-ray diffraction, UVvisible spectrophotometer, Photoluminescence spectroscopy and Transmission electron microscopy. The obtained XRD spectrums revealed the crystalline nature of synthesized materials and the average diameters of Fe2O3 nanoparticles, ZnO nanoparticles and Fe2O3/ZnO nanocomposite came out to be 11.33 nm, 14.31 nm and 9.80 nm, respectively. The UV-visible absorbance spectra and photoluminescence spectrums confirmed that the Fe2O3/ZnO nanocomposite was visible light active and had excitation peaks in the visible range. Results: The TEM analysis confirmed the composite and semiconductor nature of the synthesized Fe2O3/ZnO nanocomposite. Furthermore, the photocatalytic activity of Fe2O3/ZnO nanocomposite reaches about 91.07% degradation of methyl orange dye within a time period of 150 min at an optimized catalyst dose. Adsorption isotherm and kinetic study were also applied to validate the study. Conclusion:: It was found that there was monolayer adsorption of methyl orange dye molecules on the surface of the synthesized catalyst under optimized experimental conditions and also, the adsorption process follows the pseudo-second-order kinetic model.

Adsorption isotherm and kinetic study of Bengkulu Kaolinite in removing ferrous cation by continuous operation

Iron is a chemical element that is found in groundwater that can be suspended in the form of ferrous cations. Iron presence that exceeds the threshold can cause detrimental effects such as piping corrosion, bad smells, and health problems. According to observations, groundwater in Sukarame, Bandar Lampung, has smells and colors that indicate iron metal contamination. Hence, it is necessary to research reducing the iron content. The method used in this research is the adsorption method using kaolin adsorbent that has been activated by physical activation at 700°C. The adsorption was conducted continuously with various reactor heights of 20 cm, 15 cm, and 10 cm. The results showed that the most significant reduction in efficiency was found in the adsorption using reactors with a height of 20 cm by 92%. The adsorption phenomenon using a reactor height of 20 cm followed the Langmuir isotherm model (R2 = 0.9255) with an adsorption capacity of 17.03 mg/g. The kinetic data correlated well with the pseudo-second-order equation (R2 = 0.9313). It can be concluded that kaolin adsorbent can reduce iron levels, in which the adsorption using reactors with a height of 20 cm is the most effective.

Development of a molecularly imprinted polymer on silanized graphene oxide for the detection of 17-estradiol in wastewater.

This research article demonstrates the synthesis, characterization, and electrochemical evaluation of a molecularly imprinted polymer (MIP) on the surface of silanized graphene oxide (silanized GO), which is nanostructured and used to quantify 17-estradiol (E2) in wastewater. As characterization methods, X-ray diffraction (XRD), Raman spectroscopy, dynamic scattering light (DSL), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) were utilized to examine the synthesized GO, silanized GO, MIP-GO composite, and non-imprinted polymer (NIP)-GO (NIP-GO) composite. FTIR results confirmed the successful synthesis of GO composites. Raman study confirmed the synthesis of monolayer silanized GO, MIP-GO composite, and NIP-GO composite. Surface morphology revealed that after polymerization, the surface of silanized GO sheet-like morphology is covered with nanoparticles. Adsorption kinetics studies revealed that adsorption follows the pseudo-second-order kinetics. Further, we studied the performance of a MIP-GO-based sensor by optimizing the effects of pH, scan rate, and incubation period. The linear calibration was achieved between the oxidation peak current and E2 concentration from 0.1 to 0.81 ppm, with a detection limit of 0.037 ppm. The selectivity of the MIP-GO composite was also checked by using other estrogens, and it was found that E2 is 3.3, 0.5, and 1.4 times more selective than equilin, estriol, and estrone, respectively. The composite was successfully applied to the wastewater samples for the detection of E2, and a good percentage of recoveries were achieved. It suggests that the reported composite can be applied to real samples. PRACTITIONER POINTS: An innovative electrochemical sensor was developed for selective detection of 17-estradiol through molecularly imprinted polymer fabricated on the surface of silanized GO (MIP-GO composite). The developed method was comprehensively validated and found to be linear in the range of 0.1 to 0.8ppm of 17-estradiol, with 0.037 ppm of limit of detection and 0.1ppm of limit of quantification, respectively. The developed MIP-GO-composite-based electrochemical sensor was found 3.3, 0.5, and 1.4 times more selective for 17-estradiol than equiline, estriol, and estrone, respectively. The applicability of a developed sensor was also checked on wastewater samples, and a good percent recovery was obtained.

Fabrication of metal oxides-based adsorbents for SO2 capture with equimolar adsorption

A series of novel porous metal oxides (MO, M = Mg, Ca, Ba, Mn and Zn) adsorbents were synthesized through simple thermal treatment of the corresponding metal sulfite for the remotion of sulfur dioxide (SO2). The obtained MO adsorbents were characterized by various techniques including scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), X-ray diffraction (XRD) and nitrogen adsorption studies. The results show that the SO2 adsorption capacity of manganese oxide (MnO) is much higher than that of other MO. And due to its highly dispersed and large specific surface area, especially its well-developed pore structure, equimolar adsorption of SO2 can be achieved for the first time among similar SO2 adsorbents. In addition, different sources of MnO were explored and it was found that the MnO obtained from the decomposition of MnSO3 had the highest SO2 adsorption capacity. Adsorption kinetic studies show that the reaction between MnO and SO2 conforms to the pseudo-second-order kinetic equation. Furthermore, it was found through seven-cycle experiments that the adsorption amount tended to stabilize in each of the following cycles, except for the first high temperature, which led to changes in the adsorbent and a decrease in cycling performance. This strategy has three advantages: one-step preparation at low temperatures, equimolar adsorption of SO2 as well as good reusability and selectivity.

Research on the Impact of Modification Method on 13X Zeolite Molecular Sieve Adsorption Performance for SO2

AbstractThe article takes 13X molecular sieve as the object, studies the effects of three modification methods, including calcination temperature, NaOH solution concentration, and CuO and MnO2 loading, on the adsorption performance of SO2 on 13X molecular sieve, and preliminarily explores the adsorption kinetics characteristics of 13X‐xwt % MnO2. The results show that the modification method of loading 13X‐6wt %MnO2 is better, the penetration adsorption time is about 130 minutes, and the maximum penetrable adsorption capacity is 57.8 mg⋅g‐1 .The adsorption kinetics study of 13X‐6wt % MnO2 shows that the R2 of the quasi‐second‐order model is close to 0.99, indicating that the adsorption process follows the quasi‐second‐order kinetic equation. The particle diffusion kinetic model fitting shows that the adsorption process is divided into two stages, the first stage is rapid adsorption, which is mainly controlled by surface adsorption and intraparticle diffusion rate, while the second stage is mainly microporous or chemisorption, with a smaller adsorption amount.

Efficient removal of dibutyl phthalate from transformer oils by iron/activated carbon adsorbent

Capturing dibutyl phthalate (DBP) impurities from transformer oils and purifying them is crucial for maintaining long-term sustainable transformer operation. Furthermore, this process significantly reduces the generation of waste from aged transformer oils, thereby contributing to environmental protection and sustainable development. In this study, various metal ion-modified wood activated carbons (ACs) were prepared using the wet impregnation method. The adsorption isotherms and adsorption kinetics studies reveal that Fe/AC exhibits a significant enhancement of more than 40% in DBP adsorption capacity compared to the original AC. Consequently, Fe/AC is the material with the highest adsorption capacity for DBP in transformer oils up to now. Furthermore, the desorption activation energy of DBP on Fe/AC was 46.623 kJ/mol, 1.73 times higher than original AC. Ultimately, the adsorption mechanism was explained using the Hard-Soft-Acid-Base (HSAB) principle, which demonstrated a stronger interaction between hard base DBP and Fe/AC due to the hard acidic nature of Fe3+ and therefore a higher capture capacity of DBP by Fe/AC. The simplified preparation method and enhanced adsorption capacity of the modified Fe/AC make it an efficient and cost-effective approach to ensure reliable and sustained transformer operation, while also minimizing the generation of waste transformer oils.

Kinetic and mechanistic study of CO2 adsorption on activated hydrochars

Four activated hydrochars (AHCs) were obtained by hydrothermal carbonization of pine sawdust followed by physical and chemical activation in mild conditions. The effects of the activating agents on the porous structure of AHCs were analysed using nitrogen adsorption isotherms. Their CO2 adsorption capacity was assessed by means of carbon dioxide isotherms at 25 and 50 ºC and thermogravimetry, and compared with a commercial activated carbon (AC). SBET values greater than 2000 m2/g were obtained. A narrow micropore volume of 0.392 cm3/g was obtained for the hydrochar activated with KHCO3. The highest CO2 uptake of 3.3 mmol/g (145.2 mg/g) was obtained at room temperature (25 ºC) for the hydrochar activated with KHCO3. Three kinetic models (pseudo-first, pseudo-second and fractional order Avrami’s models) were used to examine the rate parameters of CO2 uptake, with Avrami’s model giving the most accurate prediction of CO2 adsorption. The intraparticle diffusion model and Boyd’s film-diffusion model were applied to identify the CO2 adsorption mechanism.

Properties and Evaluation of Functionalized Mixed Membrane Adsorbents for the Adsorption of Vanillic Acid from Palm Oil Waste

Identifying factors that can improve the ability of mixed matrix membrane (MMM) adsorbents to isolate phenolic chemicals from palm oil waste is a major challenge. This study prepared a mixed matrix membrane with improved efficiency using a quaternary doping solution and a hydroxyapatite (HAp) filler and denoted as modified mixed matrix membrane (MMMHAp). Prior to use, HAp powder obtained from eggshells calcined at different temperatures was evaluated as an absorbent for the desired phenolic compounds. All the prepared HAp and MMMHAp powders were evaluated for their properties by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffraction (XRD). For this study, vanillic acid was selected as a phenolic chemical because it is widely used in the pharmaceutical, biomedical and food industries. The optimal adsorption and vanillic acid isolation from crude palm oil samples by MMMHAp occurred using an acetate buffer solution with a pH of 8. The data from the equilibrium adsorption study were also in agreement with the Freundlich isotherm, as the R2 value was 0.9900 suggesting heterogeneous adsorption of vanillic acid on the surface of MMMHAp. The kinetic adsorption study clearly shows a pseudo-second-order fit (R2=0.9992), suggesting that chemisorption occurs between the adsorbed substance and the adsorbent. The modified membrane (MMMHAp) has characteristics of its finger-like structures is more elongated and connected to the porous layer, indicating that the incorporation of hydroxyapatite nanoparticles into the membrane enhances the adsorption of vanillic acid from real sample and has the highest adsorption capacity of 170.8 mg/g. These results show that this improved MMMHAp can be developed and used for waste utilization to obtain useful materials.

Pseudo-Second-Order Kinetic Equation for Describing the Effect of Sorbent and Sorbate Concentrations.

The sorbent concentration (Cs) effect and sorbate initial concentration (C0) effect are common phenomena observed in the study of adsorption kinetics at solid-liquid interfaces. That is, adsorption rate constants simulated with classical kinetic equations, such as the pseudo-second-order (PSO) model, for a given system vary with Cs and C0. The classical kinetic equations cannot predict or describe the "Cs-effect" and "C0-effect" (called "C-effects" here). In the current work, the dynamic partition coefficient of sorbate between solid and liquid phases (Kt) was used to describe the adsorption kinetic processes. Based on the surface component activity (SCA) model, which assumes the activity coefficients of the surface components (fs) are not equal to unity but rather a function of Cs and the adsorption capacity (or C0) and referring to the classical PSO model, a new kinetic equation was established, called the "SCA-PSO kinetic model", and its two parameters, the intrinsic equilibrium partition coefficient (Ke0) and the intrinsic rate constant (k20), are independent of Cs and C0. In addition, the new model relates Kt and the rate constant (k2) to Cs and C0 via fs, and can thus describe the C-effects. The fs can be estimated from the change of equilibrium partition coefficient (Ke) with Cs and C0. The new model predicts that with the increase of Cs and C0, Ke decreases while k2 increases. Its rationality was confirmed by the literature-reported adsorption kinetic data of heavy metals on inorganic and biomass sorbents with the C-effects.

Hagenia abyssinica-Biomediated Synthesis of a Magnetic Fe3O4/NiO Nanoadsorbent for Adsorption of Lead from Wastewater.

Magnetic nanocomposite adsorbents are cost-effective, environmentally friendly, easy to use, and highly efficient at removing metals from large volumes of wastewater in a short time by using an external magnetic field. In this study, an Fe3O4/NiO composite nanoadsorbent was prepared by varying the mass percent ratios of NiO (50, 40, 30, 20%), which are denoted Fe3O4/50%NiO, Fe3O4/40%NiO, Fe3O4/30%NiO, and Fe3O4/20%NiO, respectively, using Hagenia abyssinica plant extract as the template/capping agent and a simple mechanical grinding technique. The nanocomposites were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, nitrogen adsorption, and ζ-potential measurements. The adsorption performance of the nanoadsorbent was assessed for the removal of lead (Pb2+) ions from aqueous solutions. Among the composite adsorbents, Fe3O4/50%NiO demonstrated the best Pb(II) removal efficiency (96.65%) from aqueous solutions within 80 min at pH 8, at a 100 mg/L lead concentration and 0.09 g of adsorbent dose. However, with the same parameter, only 62.8% of Pb(II) was removed using Fe3O4 nanoparticles (NPs). The adsorptive performance indicated that the optimum amount of porous material (NiO) in the preparation of the Fe3O4/NiO composite nanoadsorbent, with the aid of H. abyssinica plant extract, enhances the removal of toxic heavy metals from aqueous solutions. Multiple isotherm and kinetic models were used to analyze the equilibrium data. Adsorption isotherm and kinetic studies were found to follow the Freundlich isotherm and pseudo-second-order kinetics, respectively.

Single and Competitive Adsorption of Naphthalene, Phenanthrene, and Pyrene on Polystyrene Nanofibers.

In this investigation, polystyrene (PS) nanofibers were prepared by electrospinning for the adsorption of naphthalene (Nap), phenanthrene (Phe), and pyrene (Pyr) from an aqueous solution. Surface morphology and physicochemical characteristics of PS nanofibers were analyzed using Fourier transform infrared spectroscopy (FT-IR) and point-of-zero-charge calorimetry (pHpzc). The effects of pH, ion concentration, and temperature on the adsorption were also investigated. The adsorption mechanism of target pollutants on PS nanofibers was investigated by a batch adsorption method. The adsorption kinetic studies showed that the adsorption of the three polycyclic aromatic hydrocarbons (PAHs) on PS nanofibers conformed to the pseudo-second-order kinetic model in both single and ternary systems. Meanwhile, in a single system, the three PAHs adsorbed on nanofibers were controlled by both intraparticle diffusion and liquid film diffusion, whereas the adsorption of Nap in a ternary system was controlled mainly by intraparticle diffusion, and the adsorption of Phe and Pyr was controlled mainly by liquid film diffusion. The isotherm data indicated that the Freundlich model performed better than the Langmuir model for the adsorptions of Nap, Phe, and Pyr on PS nanofibers in both the single system and the ternary system. Due to competitive adsorption, the adsorption capacities of Nap and Pyr on PS nanofibers decreased from 105.816 and 19.098 mg g-1 in the single system to 23.626 and 12.126 mg g-1 in the ternary system, but the adsorption of Phe was not affected. π-π interactions and pore filling may be jointly involved in the adsorption of PAHs on PS nanofibers.

Kinetic studies of adsorption on biochar from aqueous solutions

Kinetic studies of adsorption on biochar from aqueous solutions