Adsorption Regeneration Research Articles

Modeling and simulation of continuous fixed adsorptive distillation with adsorbent regeneration using thermal desorption

Fixed adsorptive distillation (FAD), a hybrid separation method combining distillation and adsorption, was proven to be able to break the azeotropic point and to enhance the product purity of azeotropic solution. FAD consists of two conventional distillation columns, equipped with an inter-bed of adsorbent. To operate a continuous FAD, a pair of adsorbent beds must be utilized in which adsorption operation and adsorbent regeneration are carried out alternately. This work is a parametric study which aims to model and to simulate a continuous FAD with adsorbent regeneration using thermal desorption. The azeotropic solution model used is water-isopropyl alcohol (IPA) with adsorbent of silica. Variable analysis is conducted to derive the equations, to obtain the appropriate design variable/s, and to systematically calculate the state variables. The appropriate design variables are the adsorptive flow (Adf) and the bottom product of Column 2 (B2); while the recycle variable is the distillate of Column 2 (D2). The successful continuous FAD is measured based on the composition of IPA in the feed of Column 2 (xF2) and that in the distillate of Column 2 (xD2); both must be above the azeotropic point. To ensure the successful continuous FAD with a fresh feed of 100 mol/min. (30% mole IPA), relatively pure water and IPA in both bottoms, and equal flow split of adsorptive-bypass flow (Rf = 1), the adsorptive flow and the flow rate of bottom product of Column 2 are operated at (25.00-107.00) mol/min. and (29.77-30.29) mol/min., respectively.

Air drying using Fe3O4-silica gel composite laminates and hollow tubes with magnetic induction heating based adsorbent regeneration

In the context of the chemical industry’s electrification, magnetic induction swing adsorption (MISA) has garnered attention in recent years, as it allows the direct conversion of renewable electrical energy into thermal energy. In this study, MISA was employed as an alternative technology for regenerating gas- and air drying adsorbents. For this purpose, composite adsorbents were synthesized, primarily composed of silica gel (as the adsorbent) and Fe3O4 (as the magnetic susceptor), and structured into either sheets or tubes. The inclusion of Fe3O4 reduced the surface area and mass adsorption capacity, but the hydrophilic character was retained, allowing for sustained water uptake. Additionally, the smaller particle size of silica gel in the composite material, compared to silica gel granules, enhanced the uptake kinetics, leading to faster saturation. Static experiments (without a convective gas flow) indicated that both the electric current and the Fe3O4 content significantly influenced heat generation and, consequently, the regeneration time. With a current of 49.4 A and 20 wt% Fe3O4, the temperature increased by 10 °C after 3600 s, removing 42 % of the adsorbed water. In contrast, at 100.7 A and 40 wt% Fe3O4, the temperature reached 250 °C in just 180 s, resulting in the removal of 92 % of the adsorbed water. The use of an convective flow over the material enhanced the regeneration efficiency to > 97 %. For the first time, a systematic analysis was conducted on the regeneration of integral water-saturated adsorbents using magnetic induction heating.

Biosorption of petroleum compounds from aqueous solutions using walnut shells

Herein, a walnut shell as a biosorbent was applied to remove petroleum compounds from the water medium. The characterization analyses of the walnut shells showed the macro-mesopore structure of the walnut shells, a specific surface area of 26 m2/g, and the presence of various functional groups (-OH, -COOH, -C = O). The CCD design showed that the walnut shell can remove 84.43% of petroleum compounds at pH = 3 (the optimum pH), adsorbent dosage: 2 g/L, and initial concentration of petroleum compounds: 550 mg/L. The study of kinetics and adsorption equilibrium indicated matching the experimental data with the pseudo-second-order kinetic model and Freundlich equilibrium isotherm, respectively. The maximum adsorption ability of walnut shell was 3038.29 mg/g at 45 °C. The ability to regenerate and reuse the walnut shell was investigated in 6 cycles, and the results showed a 21% decrease in adsorption ability after 6 cycles. The obtained data showed that the walnut shells could be a promising adsorbent with high adsorption ability toward petroleum components. Also, the walnut shell is a regenerable adsorbent, low-cost, and environmentally friendly, and can be effective in successive cycles. Therefore, this biosorbent can have a superb influence on wastewater treatment technology and possible applications at an industrial scale.

Efficient fluoxetine removal from water using Tunisian clay as adsorbent and its regeneration through NaOH-activated peroxymonosulfate

Pharmaceuticals in aquatic environments pose significant environmental and public health risks. This pioneering study introduces a novel approach to removing fluoxetine (FLX) through adsorption onto Tunisian purified clay (PC), while exploring an innovative adsorbent regeneration method via Advanced Oxidation Processes (AOPs). The adsorbent material was characterized using various techniques to determine its: morphological structure, physical properties, mineralogical composition and chemical composition. Key adsorption parameters (contact time, pH, and initial concentration) were optimized, the optimization process revealed an impressive maximum adsorption capacity of 390.28 mg/g for FLX by PC. The experimental data best fit with the pseudo-second order and Langmuir models, these findings provide insights into the adsorption mechanism and surface characteristics of the PC. The PC regenerated with PMS activated by NaOH is an interesting innovation in the field of reusable clay materials, maintaining a high performance across four cycles, with efficiency dropping only from 94 % to 64 %. The study’s findings represent a significant advancement in developing sustainable solutions for pharmaceutical removal from aquatic environments. By combining a highly efficient, locally-sourced adsorbent with a novel regeneration method, this research opens new avenues for addressing the growing concern of pharmaceutical contamination in water bodies, offering a promising, eco-friendly approach to water treatment technologies.

Harnessing carbon-based adsorbents for poly- and perfluorinated substance removal: A comprehensive review

Poly- and perfluoroalkyl substances (PFAS) are synthetic, highly fluorinated chemicals commonly used in products like water-resistant materials, personal care items, non-stick cookware, and cleaning agents. Due to the strength of their CF bonds, PFAS are extremely persistent in the environment, creating significant challenges for pollution control. Traditional degradation methods often prove ineffective, making adsorption a promising alternative for PFAS removal from contaminated water. Carbon-based adsorbents, valued for their sustainability and efficiency, are particularly effective for this purpose. This review provides a detailed analysis on PFAS properties and their removal using various carbon-based adsorbents, including activated carbon, biochar, graphene oxide, carbon nanotubes, and magnetic composites. Adsorption capacities of these materials were seen vary significantly, from as low as 10.7 mg/g for Fe3O4-hybrid biochar, to as high as 713.85 mg/g for functionalized graphene-based adsorbent, highlighting the superior adsorption efficiency of modified graphene adsorbents compared to traditional biochar and activated carbons. Most of these adsorbents fit the Langmuir isotherm model and pseudo-second-order kinetic model with high coefficient of determination, indicating efficient monolayer adsorption and strong interaction with PFAS. The review also explores different adsorption mechanisms, the effects of process parameters on adsorption efficiency, strategies for adsorbent regeneration, and concludes with a bibliometric analysis that highlights key research gaps. These insights are intended to guide future advancements in the development of effective, scalable PFAS remediation technologies using carbon-based adsorbents.

Preparation of Ni/ZnCo2O4@ZnO composite metal oxide adsorbent and its adsorption desulfurization and regeneration performance

Metal Co was introduced into ZnO by co-precipitation to form composite metal oxides as the desulfurization agent with different Co contents, with which the desulfurization activity and regeneration performance were investigated. The systematic characterization of the structure and properties of the desulfurization agent using XRD, TEM, N2 adsorption and desorption, XPS and H2-TPR confirmed that the composite metal oxide desulfurization agent had the Ni/ZnCo2O4@ZnO structure. The formation of ZnCo2O4 in the composite metal oxides desulfurization agent facilitated the particle size reduction, dispersion enhancement and specific surface area increase of the desulfurization agent, which also acted as an adsorbent for H2S indicated by the XRD analysis, improving the sulfur adsorption capacity of the desulfurization agent. The desulfurization performance of all the composite metal oxide desulfurization agents was higher than that of Ni/ZnO, in which the desulfurization agent NZCo-3 with a molar ratio of Zn:Co of 1:1 exhibited the optimal desulfurization performance, and the desulfurization rate was 100% at a reaction temperature of 300 °C, a hydrogen pressure of 3 MPa, a mass-air velocity of 2.2 h–1, and a hydrogen-oil ratio of 300, and the excellent desulfurization performance was maintained after 6 cycles. The results of this study provide new ideas for the rational design of Ni/ZnO desulfurization agent to improve its desulfurization and regeneration performance.

Rapid Capture Perfluorooctanoic Acid and Perfluorooctane Sulfonate at Environmentally Relevant Concentrations via the ‘mesh trap’ of Triazine-Based Polymer Network: Mechanism and Photocatalytic regeneration

Per- and polyfluoroalkyl substances (PFAS) pose a serious threat to groundwater (GW) environment worldwide due to their difficulty in removal and high toxicity. In this study, the ‘mesh trap’ of triazine-based polymerization network (SNW-1) demonstrated rapid capture performance for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) at environmentally relevant concentrations (1μg/L). The SNW-1 can remove more than 90% of PFOA and PFOS within 300s and still maintain superior performance under four common GW anions and different [pH]0 (3 - 10). The removal degree of PFOA and PFOS is almost undetectable without SNW-1 dosage. Theoretical calculations were used to simulate the adsorption process and interfacial reaction mechanism in SNW-1/PFOA (Eads = -1.6717eV) and SNW-1/PFOS (Eads = -1.2695eV) systems. The adsorption of SNW-1/PFOA is stronger than SNW-1/PFOS. The typical van der Waals weak interactions between SNW-1 and PFOA were confirmed, which is slightly stronger than SNW-1/PFOS. In addition, SNW-1 regeneration in this paper was achieved in a photocatalytic activated peroxydisulfate (PDS) system which was different with previous reports. The desorption rates of PFOA and PFOS adsorbed on the surface of SNW-1 and the defluorination rate in the photocatalytic regeneration system were also tested. The photocatalytic regeneration mechanism between SNW-1 and PDS was electron transfer. And the electron transfer can be divided into three stages: strong adsorption of SNW-1/PDS (Eads = -2.1618eV), electron transfer from SNW-1 to PDS and PDS cleavage. This study has a broad application prospect in the field of in-situ rapid resistance control of GW in PFAS contaminated sites and provides a theoretical support for environmentally friendly adsorbent regeneration technology.

Lithium recovery in a batch adsorption study: Synthesis, characterization, optimization, regeneration, kinetics, and isotherm studies

Lithium (Li)recovery is significant due to an increasing need for Li in diverse applications, particularly in the energy storage domain. In this study, a synthesized adsorbent was developed and utilized to efficiently recover Li. Therefore, this research aims to assess the effectiveness of using the synthesized adsorbent LiHMO to recover Li from the aqueous solution. The surface area and characteristics of the synthesized adsorbent were subjected to analysis utilizing different methods and techniques, including scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier-transform infrared spectroscopy (FTIR). The findings indicated that the synthesized adsorbent demonstrated exceptional adsorption capabilities for Li recovery. Characterization analysis revealed a well-defined porous structure and functional groups on the adsorbent's surface, facilitating adsorption. The surface area of the adsorbent was determined to be 25.54 m²/g, providing a substantial active surface for adsorption processes. The Box-Behnken response surface method (RSM) was utilized to optimize the recovery process for key factors such as pH, adsorbent dose, time, and concentration. The critical operating parameters identified included a pH of 4, initial concentration of 900 mg/L, contact time of 460 min, and adsorbent dosage of 1300 mg/L. The obtained data were analyzed using a quadratic model, yielding an R² value of 0.9538, indicating that the adsorbent is effective in Li adsorption. The optimal conditions for maximizing Li recovery were found to be 95 % and 89 % for maximum and minimum recovery, respectively. The amount of adsorbate adsorbed (qe) was determined to be 6.2 mg g-1. Various kinetic models and isotherms were utilized to conform to these parameters. The Freundlich isotherm and the intraparticle diffusion model showed strong fits, as evidenced by their R² results of 0.9876 and 0.9862, respectively. The kinetic study suggested that the intraparticle-diffusion model best explained the adsorption process, indicating chemisorption as the rate-limiting step. The equilibrium data fitted well with the Freundlich isotherm, suggesting multilayer adsorption with heterogeneous surface energies. Furthermore, the study assessed the adsorbent's regeneration potential, finding that the first cycle of regeneration achieved 91.9 % efficiency, while the fifth cycle maintained a high efficiency of 89.7 %, indicating good reusability of the adsorbent. The study's findings showcase the efficiency of the synthesized adsorbent LiHMO in Li recovery from aqueous solutions, offering valuable information about the best conditions for the adsorption process. As a result of its superior sorption capacity and high recovery of adsorbed Li, the LiHMO adsorbent was selected as the optimal choice for Li recovery from aqueous solutions.

Adsorptive Removal of Bisphenol A by Polyethylene Meshes Grafted with an Amino Group-Containing Monomer, 2-(Dimethylamino)ethyl Methacrylate

The adsorptive removal of Bisphenol A (BPA) with the PE meshes photografted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was performed by varying the grafted amount, pH value, BPA concentration, and temperature, and the adsorption performance was correlated by the equilibrium, kinetic, and isotherm models. In addition, the regeneration of DMAEMA-grafted PE (PE-g-PDMAEMA) meshes was discussed from the repetitive adsorption/desorption process. The adsorption capacity had the maximum value at the grafted amount of 2.6 mmol/g and at the initial pH value of 8.0. The increase in the protonation of dimethylamino groups on grafted PDMAEMA chains and the dissociation of phenol groups of BPA present in the outer solution during the adsorption process results in the increase in BPA adsorption. The adsorption process followed the pseudo second-order equation. The BPA adsorption was enhanced by increasing the BPA concentration and the equilibrium data fit to Langmuir equation. The adsorption capacity stayed almost constant with the increase in the temperature, whereas the k2 value increased against the temperature. These results comprehensively emphasized that BPA adsorption occurred through the chemical interaction or ionic bonding of a BPA anion to a terminal protonated dimethylamino group. Desorption of BPA increased by increasing the NaOH concentration and BPA was entirely desorbed at more than 20 mM. The cycle of adsorption at pH 8.0 and desorption in a NaOH solution at 100 mM was repeated five times without loss or structural damage. These results indicate PE-g-PDMAEMA meshes can be used as a regenerative adsorbent for BPA removal from aqueous medium.

Integrated substrate and adsorbent layer additive manufacturing for asymmetrically operating minichannel adsorbent bed

Adsorption heat pumps (AHP) have conventionally used packed bed design, making their operation sluggish leading to difficulty in using heat for the adsorbent regeneration. While thin adsorbent coatings improve the performance of AHPs when implemented in microscale geometries like minichannels, integrating the adsorbent coating procedure into the scaled-up adsorbent bed manufacturing has been impractical because of the finite time required for the coating process. Meanwhile, separately coated plates manifest sealing issues. This research details an innovative avenue to fabricate a unified adsorbent bed integrated with thin adsorbent coatings. Here, a compact adsorbent bed was fabricated through the integration of additive manufacturing using a fused deposition modeling (FDM) 3D printer for the substrate and resin curing for the MIL-101 (Cr) adsorbent layer. The multi-layered bed was designed to exchange heat between heat transfer fluid (HTF) and the passages through which the refrigerant vapor flows. The vapor channels were coated with a MIL-101 (Cr) adsorbent. The research incorporated both experiments and computational models to evaluate the operation of this adsorbent bed through the measurement of pressure during the adsorption and desorption stages for this component. Various HTF temperatures (80 °C − 90 °C) and flow rates (0.125 kg min−1 – 0.25 kg min -1) were tested. The findings revealed the much-desired asymmetrical operation with long adsorption (75–80 % of the cycle time) and short desorption stages (20 %-25 % of the cycle time), opening the possibility of employing a single bed in adsorption cooling systems to produce a near continuous cooling effect leading to more compact AHPs. The computational model developed for this test setup using MATLAB strongly aligned with experimental findings, with an error margin of 4–12 %.

Removal of perfluoroalkyl acids and precursors with silylated clay: Efficient adsorption and enhanced reuse

Organically modified clays (organoclays) have been considered effective adsorbents for the treatment of per- and polyfluoroalkyl substances (PFAS). However, the stability of organoclays prepared through the conventional cation exchange approach has been a major concern for their practical application. In this study, we reported the development of a new organically functionalized clay by grafting pillared clay substrate with an organosilane through covalent bonding. The performance of the silylated clay (QAG-ZrMT) was systematically compared with an organoclay prepared from ion exchange (HDTMA-ZrMT) for the adsorption of two legacy perfluoroalkyl acids: perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and two precursor compounds 5:3 fluorotelomer carboxylic acid (5:3FTCA) and 6:2 fluorotelomer sulfonic acid (6:2FTS). Compared to HDTMA-ZrMT, QAG-ZrMT showed substantially improved performance for adsorption of less hydrophobic PFAS (e.g., 5:3FTCA), which could be related to the stronger electrostatic interactions between PFAS and QAG-ZrMT than HDTMA-ZrMT. More importantly, QAG-ZrMT could be conveniently regenerated and reused for multiple cycles with robust performance. In contrast, HDTMA-ZrMT almost completely lost its capacity for PFAS removal after regeneration, due to the loss of organic functional groups during solvent regeneration. Results can shed light on the design of efficient and regenerable organoclay adsorbents for remediation of PFAS-contaminated water matrices.

Assessing Adsorption and Desorption Performance in the Recovery of Volatile Organic Compounds

In this study, the activated carbon fiber filter design and VOC adsorption and desorption performance were evaluated based on the development of a filter regeneration device to treat VOCs in high efficiency and low cost. Activated carbon fiber (ACF) has the advantage of fast adsorption speed and high adsorption capacity because micropores are formed on the surface and a large specific surface area. However, the specific gravity is about 25 times lower than that of activated carbon (AC), so the amount of adsorbent that can fill the same volume is small. In order to solve this problem, the regeneration device is implemented by repeating adsorption and regeneration for a short time, and a cylindrical adsorption filter made of activated carbon fiber is designed according to the operating conditions of the regeneration device. At this time, the pollutant gas and regenerated air are uniformly distributed over the entire adsorbent, and the flow characteristics according to the supply of the pollutant gas and the regeneration gas are analyzed. When the size of the lower part of the cylindrical adsorption filter is smaller than the size of the upper part under the condition that the pollutant gas flows downward, a uniform distribution of the pollutant gas is possible. In addition, as the space velocity decreases, the adsorption capacity decreases, and the differential pressure increases rapidly. Through the regeneration experiment, it was confirmed that the desorption concentration of MEK was higher and the desorption concentration was higher. In addition, the regenerated air is uniformly dispersed throughout the adsorption filter, toluene, o-xylene, and methyl ethyl ketone, which are representative substances of volatile organic compounds (VOCs), are injected with 400 ppm, and then regenerated air is supplied at 150 °C to analyze adsorption characteristics and regeneration concentrations. As a result of the experiment, the adsorption capacity ratio to 1 g of regeneration air according to the type of VOCs was 0.48, 0.36, and 0.25 g in the order of o-xylene, toluene, and methyl ethyl ketone. In addition, as the space velocity decreases, the adsorption capacity decreases, and the differential pressure increases rapidly. Through the regeneration experiment, it was confirmed that the desorption concentration of MEK was higher and the desorption concentration of o-xylene was discharged at a relatively low concentration. Moreover, even if the adsorption concentration changes, there was no difference in the regeneration concentration change. Therefore, the filter was designed based on the spatial speed of the regeneration device of 51,000 -h or less, and the adsorption capacity ratio to 1 g of the regeneration air amount was 0.1 g, thereby enhancing the filter's recycling performance and VOCs emission effect.

Movable VOC Removal System

In this study, we develop a mobile VOCs gas removal system that can remove volatile organic compound (VOCs) emissions from petrochemical facilities, metal painting factories, and surroundings of life, and can efficiently cope with situations occurring in the field. Regular repairs to petrochemical plants and semiconductor plants are carried out for a month every four to five years, and work such as replacing old pipes and repairing aging facilities, cleaning, removing residual gas, checking pipe connections and valves, and improving processes are carried out while the plant is shut down. During regular maintenance, a large-scale accident occurs in which gas remaining in the facility leaks or explodes due to rising pressure, and even after internal gas discharge and purge work is performed, it is scattered by the characteristics of raw materials remaining inside the pipe and reactor and discharged into the atmosphere. Therefore, there is always a possibility of causing safety accidents, and such accidents have a great socioeconomic impact as they are directly connected to the safety of workers as well as the safety of local residents. This system is designed to be adaptable according to the size of a number of outlets, and it is proposed to minimize the impact of VOCs harmful gases on the surroundings by developing it as a mobile type. The efficiency of collecting scattered VOCs gas is more than 90%, and the integrated operating system is demonstrated for 50 CMM class movable VOCs adsorption device, 5 CMM class treatment gas recirculation type non-flame waste heat recovery adsorbent regeneration treatment device, and two or more business sites.

Systematic experiment on adsorption, separation and regeneration of X zeolites for LNG production with different regeneration strategies: vacuum, purging, heating and hybrid combinations

This work experimentally investigated the adsorption, separation and regeneration properties of two X zeolites for natural gas deep decarbonization in liquified natural gas (LNG) production. The regeneration properties of JLOX500 and 13X were compared with relation to regeneration efficiency, energy consumption, desorption and adsorption rate of CO2, and other factors in different pathways: vacuum, purging, heating, and hybrid combinations. The results demonstrated that fresh JLOX500 with more cations and less binders had significantly greater CO2 adsorption capacities and larger separation factor (CO2/CH4) than those of fresh 13X, because of its larger micro-porosity and higher CO2 isosteric heat. Due to higher partial pressure, the adversely significant effect of CH4 competing adsorption against CO2 on adsorbent regeneration is confirmed. The flow rate increases of purge gas had no effects on regeneration efficiency for 13X when the CO2 concentration of desorbed gas reached to zero. Because of a greater cumulative pore volume, JLOX500 after sufficient regeneration has a larger CO2 adsorption capacity and a higher desorption rate of CO2 than 13X, which also makes it more efficient with regards to purge gas and energy consumption utilization. With 150 mL/min of purge gas, the energy consumptions for 13X and JLOX500 regenerated at 150 °C were 4.20 and 2.89 MJ/kg-CO2, respectively. The CH4 recovery relied on the regeneration efficiency of adsorbents, duration of adsorption, and the amount of purge gas used. Both X zeolites regenerated by purging (150 mL/min) or vacuuming at 1 kPa at 150°C could purify the feed to the CO2 content less than 50 ppm, but JLOX500 is more efficient with regards to the overall performance.

Coconut shells based MrGO@CMC adsorbent for the chromium (VI) ion removal from contaminated water through batch adsorption method

The chromium (III) ion is necessary for biological function and the chromium (VI) ion (Cr (VI)) induces toxicity to humans and animals. From the sources of industries, the contaminated Cr (VI) is an important issue to remove from the solution. Here, we synthesized magnetic reduced graphene oxide @ carboxymethyl cellulose (MrGO@CMC) adsorbent for the removal of Cr (VI) from aqueous solution. The fabricated adsorbent was characterized through XRD, FT-IR, SEM, EDX, BET, VSM, and TGA. Adsorption studies were conducted various parameters and the optimized contact time, dosage and concentration was fixed such 60 min and 10 mg L−1 respectively. By the MrGO@CMC adsorbent almost 93% efficiency Cr (VI) was removed from the aqueous solution at 40 min, 25 mg, 10 mg L−1, and neutral pH. The zero point charge (pHzpc) of the adsorbent was observed at pH-6.3. The MrGO@CMC adsorbent followed Langmuir isotherm model at achieving a maximum adsorption capacity of 625.8 mg g−1 and it indicates chemisorption dominated monolayer adsorption and the system follows pseudo-second-order kinetics model indicating a bimolecular system. Thermodynamic analysis revealed that the adsorption process was endothermic and spontaneous reaction. The adsorbent regeneration and reusability studies demonstrated that MrGO@CMC retained over 70.90% efficiency in removing Cr (VI) ions even after five recovery cycles compare with other graphene oxide-based adsorbent, the current adsorbent have potential removal efficiency, since the proposed adsorbent shows excellent adsorbent for Cr (VI) ions from industrial wastewater.

Enhanced adsorption and regeneration performances for methyl mercaptan capture by a metal–organic framework incorporated in a mesoporous silica

Cu-modified adsorbent is widely used in removing S-containing odor pollutant, such as methyl-mercaptan (CH3SH). Increasing the dispersion of adsorptive sites and improving the regeneration cycle efficiency are two important problems. In this work, a copper metal–organic framework (MOF) was synthesized by in-situ growing the Cu-MOF on SBA-15. Micro-morphology characterizations revealed that the Cu-MOFs grew inside the SBA-15 mesopore channels and showed a good dispersion. When the hybrid (Cu-MOF in SBA-15) and the Cu-MOFs were compared for the CH3SH removal, the hybrid removed 1.70-mol CH3SH per mol of Cu in the adsorbent. This adsorbent capacity was far bigger than Cu-MOFs (0.70 mol·mol−1) and resulted from a better Cu-MOFs dispersion in SBA-15. Additionally, an easy and energy-saving hydrothermal method was put forward for the regeneration of the used adsorbent at 80 °C. The capacity of the regenerated material was higher than 70 % for at least 6 cycles. In addition, the regeneration temperature was far lower than that (> 350 °C) generally utilized in previous reports investigating cycled adsorption of CH3SH. The enhanced regeneration performances were attributed to the confinement effect of the SBA-15, which restrained the ligand around the Cu coordination centers. This work confirms the effective removal of odor-gas using a cost-effective regenerable adsorbent.

Enhanced Hydrophobicity and Oleophilicity of Modified Activated Carbons Derived from Agro-Wastes Biomass for the Removal of Crude Oil from Aqueous Medium

Crude oil spillage has tremendous environmental impacts and poses severe pollution problems worldwide due to the continuous activities and operations in the oil and gas sector. This has resulted in the urgent need for clean-up techniques such as the use of natural adsorbents which is considered a relatively low-cost, readily-available, efficient, eco-friendly, and easy-to-deploy mode of addressing oil spillage due to its high oil sorption capacity/efficiency, high oil selectivity, oleophilic, enduring, reusability and biodegradable properties. Empty palm fruit bunch and coconut coir were used as precursors to produce activated carbons for oil spill remediation. The influence of varying parameters was investigated using a batch experimental procedure resulting in the crude oil adsorption capacity increasing with a corresponding increase in contact time, initial oil concentration, temperature, agitation speed, and particle size but decreasing in adsorbent dosage. The combination of surface morphological modification and hydrophobicity enhancement resulted in significantly improved adsorption capacity for crude oil removal (2710.0 mg/g and 4859.5 mg/g for EPFBAC<SUB>LA</SUB> and CCAC<SUB>L.A</SUB> respectively), as evidenced by both FTIR and SEM analyses. The experimental isotherm data were analysed using various isotherm models and the best-fitted isotherm model was the Freundlich model with a correlation coefficient (R<sup>2 </sup>= 0.991 and R<sup>2 </sup>= 0.999) for EPFB<SUB>L.A</SUB> and CCAC<SUB>L.A</SUB> respectively. The kinetic behaviour of the adsorption process was best described by pseudo-second order with R<sup>2</sup> values of 0.970 and 0.999 for EPFBAC<SUB>LA</SUB> and CCAC<SUB>L.A</SUB> respectively while Boyd model revealed that the adsorption was controlled by an internal transport mechanism and film diffusion was the rate-limiting step. The crude oil adsorption was chemisorption and endothermic owing to the positive enthalpy values (ΔH<sup>o</sup> = 183.890 KJ/mol for EPFBAC<SUB>L.A </SUB>and ΔH<sup>o</sup> = 69.656 KJ/mol for CCAC<SUB>L.A</SUB>), the positive value of entropy suggested that the adsorption process was accompanied by an increase in the degree of randomness or disorder at the interface between the adsorbent and the adsorbate. A temperature rise led to a decline in Gibbs energy (ΔG<sup>o</sup>), suggesting that adsorption became more feasible and spontaneous at higher temperatures and the significant activation energies indicated the existence of a substantial energy barrier that must be overcome to initiate the reaction. The results showed the significant capability of the prepared adsorbents to be used as a low-cost, re-generable and eco-friendly adsorbent in oil spill clean-up and is recommended to exploit its usage on a large scale.

Determination of adsorption capacity, regeneration ability, and aggregation tendency toward inorganic and organic pollutants of metal-doped carbon–silica composites in multicomponent systems

Abstract The main aim of the study was to develop a method for determining the adsorption capacity, regeneration ability, and aggregation tendency of metal-doped carbon–silica composites (iron-doped, C/Fe/SiO2, and manganese-doped, C/Mn/SiO2) against heavy metals and selected organic substances. The properties of these composites were compared with those of metal-free silica–carbon composite (C/SiO2). Inductively coupled plasma–optical emission spectrometry (ICP–OES) and high-pressure liquid chromatography were used to determine the adsorbed amounts and the desorption degree of organic/inorganic pollutants. Potentiometric titrations and electrophoretic mobility measurements were conducted to understand the mechanisms that were driving adsorption and particle aggregation. The size of the aggregates formed in the systems as well as the stability of the examined suspension were estimated by using ultraviolet-visible spectrophotometry. The performed experiments showed that the selected combination of methods is appropriate to determine the potential of metal-doped carbon–silica composites as adsorbents as well as the ease of their removal with adsorbed contaminants from aqueous solutions by sedimentation.

Adsorption dynamics of chloride removal with activated vetiver root powder: dynamic modeling perspectives and ANN predictions

ABSTRACT This study evaluates activated vetiver root powder as chloride ion adsorbent for saline water treatment. Experimental results demonstrate that activated vetiver root effectively removes chloride ions from saline solutions. Higher bed heights and lower flow rates improve efficiency by providing more adsorption sites and a longer contact time. However, higher concentrations lead to rapid bed exhaustion, highlighting the need for parameter optimization. Dynamic adsorption modeling using Thomas, Yoon–Nelson, and Clark models assesses the impact of bed height, flow rates, and initial concentration on chloride removal efficiency. Breakthrough equations closely fitted experimental data in the following order: Thomas model (R2 = 0.999) > Clark (R2 = 0.996) > Yoon–Nelson (R2 = 0.994). Scanning electron microscopy (SEM) analysis identifies pores and pockets as main surface components. Insights into adsorption mechanisms were gained through infrared and X-ray spectroscopies. A novel predictive algorithm for chloride removal in a continuous mode was developed using neural networks. Artificial neural network (ANN) prediction ability was assessed using MSE and R2 values. Future commercial applications of activated vetiver powder can be investigated using real salinity-induced wastewater. Additionally, assessing the adsorbent's regeneration and reusability is vital for confirming its cost-effectiveness and sustainability in longstanding use. This study offers perceptions for developing efficient water treatment strategies by understanding adsorption dynamics and surface characteristics for optimizing chloride removal processes.

Enhanced removal of tetracycline by vitamin C-modified cow manure biochar in water

Vitamin C (VC), due to its chemical properties, can provide more oxygen-containing functional groups such as hydroxyl groups for biochar (BC), which promotes the adsorption of tetracycline on biochar. Therefore, in this study, cow dung biochar (CDBC) was modified with VC and VC-modified CDBC (CDBC-VC) was synthesized. The modified biochar was characterized and related factors, adsorption kinetics, isotherms and adsorption mechanisms were investigated. Adsorption kinetics indicate a fast rate of adsorption. The adsorption isotherms showed that the maximum adsorption capacity was 31.72 mg/g (CDBC) and 50.90 mg/g (CDBC-VC), respectively, and the adsorption process was inhomogeneous with multiple molecular layers and the adsorbent has a higher affinity. Mechanistic studies showed that hydrogen bonding interactions, π-π electron donor-acceptor interactions, hydrophobic interactions, and electrostatic interactions were the key to the adsorption process. The analysis of adsorbent regeneration showed that CDBC-VC had good adsorption performance. CDBC and CDBC-VC showed the best performance in simulated industrial wastewater with removal rates of 78.81% and 93.69%. The adsorption mechanism was comprehensively analyzed using six machine learning models. The extreme gradient boosting model gave the best fit. Analysis of the weights of the input variables for predicting adsorption efficiency showed that the ratio of initial TC concentration to BC dosage (29.8%), specific surface area (23%), isoelectric point (8.8%), and ash content (7.7%) had a significant effect on the predicted results.