Adsorption Process Research Articles

Exploring the adsorption of Catechol and Resorcinol onto Croton caudatus activated carbon: An integrated experimental and theoretical approach

The present work aimed to examine the process for adsorption of Catechol (CT) and Resorcinol (RS) onto activated carbon that was obtained from Croton caudatus biomass (CAB). Using a batch method, the maximum removal efficiencies of 99.23 % for CT and 98.68 % for RS was achieved at adsorbent dosage-0.2 g L-1, reaction time-60 min; concentration-100 mgL-1 CT and 80 mgL-1 RS; and pH 6.0 CT and pH 4.0 RS, respectively. A maximum equilibrium adsorption of 56.05 mgg-1 and 61.85 mgg-1 was achieved at pH 6.0 and pH 4.0 for CT and RS. The adsorption behavior of both adsorbates on activated carbon were best described by the Langmuir model (correlation coefficients (R2) = 0.996 for CT and 0.995 for RS) and the pseudo-second order kinetic model. The values of ΔG, ΔS, and ΔH suggest that the adsorption process is spontaneous and endothermic. Additionally, the adsorption process is easily reversible, enabling the reuse of the adsorbate even after fifth cycle. Further, density functional theory (DFT) simulations demonstrated that the CT and RS adsorption onto the AC adsorbent is favorable. Among the oxygen functional groups analysed, the carboxyl group showed the greatest effect on the adsorption process, exhibiting the most negative adsorption energy at -44.869 (CT) and -45.082 kJmol-1 (RS), respectively. Therefore, the activated carbon derived from CAB has significant potential for effectively removing phenolic contaminants from wastewater.

Synthesis and enhanced adsorption for F− by three novel high entropy LDHs using TEA-assisted hydrothermal technology

Nowadays the design, preparation and application of high entropy LDHs (HE-LDHs) has already become research hotspots. In this paper, three types of high entropy ZnCoCrMgZr-LDHs (HE-LDHs-1, 2 and 3) were successfully prepared for the first time using TEA as alkali source by simple hydrothermal synthesis, and characterized by XRD, TG, SEM, X-ray photoelectron spectroscopy, BET and zeta potential. The effect of triethanolamine (TEA) on the formation of high entropy LDHs and their adsorption behaviour for F− were investigated. Research showed that high content of TEA can maintain and provide more hydroxyl groups required for the formation of LDHs, while the introduction of high valence Zr4+ breaks the regular arrangement of LDHs themselves. Three types of high entropy LDHs have excellent adsorption performance for F− with the maximum adsorption capacities of 113.78 mg/g, 142.12 mg/g and 128.24 mg/g, respectively. They also have strong resistance to anionic interference. The adsorption process is the transition from physical adsorption to chemical adsorption in the F− adsorption process from HE-LDHs-1 to 3. The adsorption isotherm models of LDHs-1 exhibit high R2 values which shown that their F− adsorption behaviour is the result of the combined effect of physical and chemical adsorption. The adsorption behaviour of LDHs-2 and 3 is more in line with the quasi second-order kinetic model and Langmuir model, indicating that the F− adsorption process is a single-layer adsorption based on chemical reaction-controlled kinetics. The lower temperatures are more conducive to the process for all three adsorbents adsorption process generates heat. FLDHs can still re-adsorb the dye CR after four cycles of adsorbing fluoride ions. HE-LDHs exhibit high adsorption, selectivity, and good reuse performance for fluoride ions, making them promising for wastewater treatment applications.

Removal of bisphenol A (BPA) from aqueous solution by potassium carbonate modified wetland plant biochars

Bisphenol A (BPA) is a known endocrine disruptor that is acutely toxic to the living organisms. In this study, the wetland plants Phragmites australis and Typha orientalis were subjected to carbonize at 500℃ for different durations (4, 5, and 6h) and varying mass ratios of wetland plants to potassium carbonate (1:2, 1:1, and 2:1). The prepared modified biochars were used to treat BPA in solution to explore the effect of contact time and initial concentration of BPA on adsorption performance. Both adsorption kinetic models and isotherm models were also studied. The results demonstrated a gradual increase in the adsorption capacity of Phragmites australis and Typha orientalis biochars for BPA with prolonged contact time. Furthermore, an enhancement in the adsorption capacity was observed with increasing initial BPA concentration. The modified biochars significantly enhanced BPA removal and adsorption capacities for BPA compared to the unmodified biochars. L55C (Phragmites australis carbonized at 500℃ for 5h with a mass ratio of 2:1) and X54C (Phragmites australis carbonized at 500 ℃ for 4h with a mass ratio of 2:1) exhibited the largest total surface areas, total pore volumes, microporous surface areas and microporous volumes, and achieved maximum adsorption capacities of 8.547 and 8.117mg/g, respectively. The adsorption processes were fitted with pseudo-second-order adsorption kinetic models and Langmuir models. The adsorption processes were monolayer chemical adsorption.

Dual-functional adsorptive membranes for PFAS removal: Mechanism, CFD simulation, and selective enrichment

The remediation of emerging water contaminants, particularly per- and polyfluoroalkyl substances (PFAS), presents challenges due to their refractory nature and the presence of competing substances. Dual-functional adsorptive membranes, with hydrophobic backbone and quaternary ammonium moieties, were thereby designed to selectively intercept organic competitors while enrich PFAS. A 96.8 % removal of perfluorooctanoic acid (PFOA) was achieved and this effective removal (>90 %) maintained across five reuse cycles with a total treatment capacity of 650 L m−2. Rather than the rejection mechanism of nanofiltration process, these adsorptive membranes utilize synergistic electrostatic attraction and hydrophobic interactions, leading to a greater enrichment factor of 18.5 (PFOA over humic acid) and a permeability of 34.6 L m-2h−1 bar−1 (1.9- and 4.5-fold higher than reported NF 270 membranes, respectively). Furthermore, computational fluid dynamics (CFD) modeling revealed that the sponge-like matrix effectively prevents channeling flow and enhance access to adsorption sites. Sensitivity analysis and the high Damkohler number indicated that the adsorption process is mass transfer-controlled, with the key parameters ranked in order of significance: residence time > fluid viscosity > intrinsic adsorption rate. With consistent removal performance with co-existing competitors, efficient regeneration, and reusability, the dual-functional adsorptive membranes offer promising practical efficacy for PFAS remediation.

Removal of phosphate from wastewater using zirconium/iron embedded chitosan/alginate hydrogel beads: An experimental and computational perspective

Adsorptive removal of phosphate plays a crucial role in mitigating eutrophication. Herein, the Zr/Fe embedded chitosan/alginate hydrogel bead (Zr/Fe/CS/Alg) is reported as an effective phosphate adsorbent. This polymer nanocomposite is synthesized by the in-situ reduction of the metals on the polymer matrix. The synthesized adsorbent was characterized by the FTIR, SEM-EDX, TGA, BET, and XPS. The adsorbent showed a maximum phosphate adsorption capacity of 221.72 mg/g at pH 3. The experimental data fit well with the Freundlich isotherm and pseudo-second-order kinetics model, indicating a heterogeneous multilayer surface formation and a chemisorption-dominated adsorption process. Density Functional Theory (DFT) and Monte Carlo (MC) calculations revealed high negative adsorption energy due to the chemisorption of phosphate on the adsorbent. Hence, the major interactions such as electrostatic attraction, hydrogen bonding, and inner-sphere complexation of phosphate adsorption and Zr/Fe/CS/Alg hydrogel beads were investigated from the experimental and computational analysis. The negative values of thermodynamic parameters indicated a spontaneous, exothermic, and less random adsorption process. The synthesized adsorbent exhibited excellent selectivity toward phosphate and maintained 73 % efficiency after six adsorption/desorption cycles. The Zr/Fe/CS/Alg hydrogel beads reduced the phosphate concentration in real wastewater samples from 19.02 mg/L to 0.985 mg/L, suggesting that these nanocomposite hydrogel beads could be a promising adsorbent for real-world applications.

Preparation and characterization of oat hulls-filled-sodium alginate biocomposite microbeads for the effective adsorption of toxic methylene blue dye

In this work, the performance of oat hull-filled sodium alginate (SA-O) biocomposite microbeads in the adsorptive removal of methylene blue (MB) dye was examined. First, oat hulls were pulverized and biocomposite gels containing different weight ratios of oat hulls (10 %, 20 %, and 30 %, concerning the SA amount) were prepared by dispersing them in SA solution by ultrasonic homogenization method. Finally, gels were cross-linked by dropping into a 2 % CaCl2 solution. The study revealed that the optimal adsorbent dosage was 0.025 g/50 mL, pH was roughly 6–8, and the contact time was 120 min. According to isotherm models, the non-linear Sips and Langmuir model was more appropriate compare to other isotherms from error analysis, with a maximum adsorption capacity of 687.65 mg/g and 757.57 mg/g at 298 K, respectively. Furthermore, the non-linear kinetic data and error analyzes demonstrated that the process followed the pseudo-second-order kinetic. The adsorption process was exothermic (∆H°=−17.71 kJ/mol) and spontaneous (∆G°=−26.23 kJ/mol) at 298 K, based on thermodynamic characteristics. Furthermore, reusability investigations demonstrated that the adsorbent retained its performance with no major changes in characteristics. This work reveals that highly efficient, low-cost, sustainable, and eco-friendly SA-O composites with properties might be useful adsorbents for cationic dye adsorption.

Innovative strategies for ammonia nitrogen removal in rare earth tailings: An advanced element recycling process using leaching, chemical precipitation and adsorption

Residual ammonium salt in closed rare earth mining sites leads to elevated levels of ammonia nitrogen in the surrounding environment. To mitigate ammonia nitrogen pollution at its source, a cost-effective and environmentally friendly recycling process was proposed. This process involves leaching residual ammonia nitrogen using a magnesium sulfate solution, followed by chemical precipitation for ammonia nitrogen removal. Additionally, nitrogen can be recovered as ammonia gas through the thermal decomposition of precipitates, allowing for further ammonia nitrogen adsorption from the leachate. The residual ammonium salts leaching rate reached 96.38 % with a 0.1 mol/L magnesium sulfate solution at a flow rate of 0.6 mL/min. The chemical precipitation method achieved a maximum nitrogen removal rate of 86.87 %, with an activation energy of 2.6 kJ/mol, indicating a relatively rapid process. At 190 °C, the ammonia nitrogen release rate of precipitates was 82.5 % after 2 h of thermal decomposition. The adsorption process was consistent with pseudo-second-order kinetics models using thermal decomposition products. Overall, the comprehensive removal rate of residual ammonium salts from the closed rare earth mining site was approximately 83.3 % in recycling process, optimizing the utilization of phosphorus, magnesium, and nitrogen and achieving efficient and environmentally friendly nitrogen removal.

Oxidative pyrolysis for enhanced-CO2 adsorption capacity in biosolid-derived biochar

The study conducts the adsorption kinetic analysis of biosolid-derived biochar produced from pyrolysis and oxidative pyrolysis. The adsorption kinetic analysis is performed at three different temperatures. The characteristics of the adsorption and diffusion mechanisms are evaluated by applying adsorption kinetic models and diffusion mechanism models. The pseudo-first-order model (PFO) and the pseudo-second-order model (PSO) reveal that the CO2 adsorption process of the biosolid can be categorised as physisorption with activation energy below 40 kJ/mol. The CO2 adsorption capacities of the biochar produced at 700°C, 800°C, and 900°C are 6.3, 7.9, and 6.4 mg/g at 45°C, respectively. In contrast, the biochar produced from oxidative pyrolysis shows a CO2 adsorption capacity of 7.5 mg/g at 45°C. Film and intraparticle diffusions are primary rate-limiting factors of the adsorption process. The biochar samples maintain 84-85% of their adsorption capacities after five cyclic tests. The present study demonstrates the CO2 adsorption capacity of biosolid-derived biochar produced from different conditions of pyrolysis, providing an energy-efficient and sustainable solution to CO2 adsorption with solid adsorbents.

Integrated adsorption and electrochemical sensing of Th(IV) ions using graphene oxide and chitosan decorated magnetite-based adsorbent.

Nuclear waste management is a crucial aspect as the most significant threat to the ecosystem is caused by radioactive waste in which thorium contamination remains a prominent issue. This work represents an integrated approach for the elimination of thorium through the adsorption technique and subsequent electrochemical sensing using Magnetite@Graphene Oxide@Chitosan (M@GO@Cs). Moreover, the sorption of Th(IV) ions is optimized through batch studies, which are consistent with the results derived from ANOVA using the Box-Behnken Design model, and the ideal parameters resulted in 95.79% removal efficiency of Th(IV) ions using 6 mg of adsorbent in 10 mL of 50 mg/L Th(IV) ions solution at a pH of 5 within 20 min. Maximum adsorption capacity (833.33 mg/g) is obtained from Langmuir adsorption isotherm and process was aligned with the pseudo-second-order kinetic model. M@GO@Cs exhibited high recyclability sustaining high performance across nine consecutive adsorption-desorption cycles while maintaining excellent removal efficiency upto 85%. Furthermore, the electrochemical characterization of the synthesized M@GO@Cs nanoadsorbent was studied using the Cyclic Voltammetry, and Electron Impedance Spectroscopy techniques and quantification of Th(IV) ions was done utilizing the Differential Pulse Voltammetry method with the Limit of Detection (LOD) of 0.2 mg/L within a linear range of 10-100 mg/L.

Construction and characterization of sodium alginate/polyvinyl alcohol double-network hydrogel beads with surfactant-tailored adsorption capabilities for efficient tetracycline hydrochloride removal

The extensive use of tetracycline (TC) for disease control and the residuals in wastewater has resulted in the spread and accumulation of antibiotic resistance genes, posing a severe threat to the human health and environmental safety. To solve this problem, a series of double-network hydrogel beads based on sodium alginate and polyvinyl alcohol were constructed with the introduction of various surfactants to modulate the morphology. The results showed that the introduction of surfactants can modulate the surface morphology and internal structure, which can also regulate the adsorption ability of the hydrogel beads. The SDS-B beads with SDS as surfactant exhibited highest adsorption efficiency for removal of TC with a maximum adsorption capacity up to 121.6 mg/g, which possessed a resistance to various cations and humic acid. The adsorption mechanism revealed that the superior adsorption performance of the hydrogel beads was primarily attributed to hydrogen bonding, electrostatic attraction, and π-π EDA interactions. Adsorption kinetics demonstrated that the pseudo-second-order model fitted the adsorption process well and adsorption isotherm showed the adsorption of TC occurred through both chemical and physical interactions. Moreover, the adsorption efficiency remained approximately 87.5 % after three adsorption-desorption cycles, which may have potential application and practical value in TC adsorption.

Investigation of serpentine entrainment reduction in pentlandite flotation using eco-friendly sodium alginate in suspension dispersion systems

Magnesium silicates pose severe environmental issues in hydrometallurgical processes. Copper-nickel sulfide ores are the primary source for nickel production, but their increasingly complex properties make separation difficult, causing slimy magnesium silicate minerals to be entrained into the concentrate with the foam, leading to magnesium contamination. Studies have found that sodium alginate (SA), as an environmentally friendly polymer reagent, can effectively inhibit serpentine. This work investigates the effect of SA on the flotation behavior of pentlandite and serpentine in a sodium hexametaphosphate (SHMP) system. Sedimentation tests show that only a low dosage of SA can effectively settle serpentine, while excessive SA disperses serpentine. Flotation tests indicate that SA can further increase the difference in recovery rates between pentlandite and serpentine based on SHMP. Results from artificial mixed ore tests demonstrate that the recovery rate of serpentine decreases from 51.22% to 37.37% with the addition of SA, with minimal impact on the recovery rate of pentlandite. To explain the impact of the SA adsorption process on the mineral states, the following tests and analyses were conducted: TOC and QCM-D results indicate that SA mainly adsorbs onto serpentine, forming rigid adsorption at low dosages and flexible adsorption at high dosages. Zeta potential tests reveal changes in the surface potential of the minerals, explaining the transition from electrostatic attraction to electrostatic repulsion between pentlandite and serpentine. FTIR and XPS results show that SA chemically reacts with the Mg and Si sites on the serpentine surface through its -COO- groups. In summary, in the SHMP system, the use of gel adsorption and the chemical interaction of SA to coagulate and depress serpentine reduces its entrainment into the concentrate, achieving efficient separation of pentlandite and serpentine. However, high dosages of SA do not yield satisfactory results.

Predicting the Performance of Lithium Adsorption and Recovery from Unconventional Water Sources with Machine Learning

Selective lithium (Li) recovery from unconventional water sources (UWS) (e.g., shale gas waters, geothermal brines, and rejected seawater desalination brines) using inorganic lithium-ion sieve (LIS) materials can address Li supply shortages and distribution issues. However, the development of high-performance LIS materials and the optimization of recovery-related operating parameters are hampered by the variety of production methods, intricate procedures, and experimental expenses. Machine learning (ML) techniques offer potential solutions for enhancing LIS material development. We collected literature data on Li adsorption, categorizing 16 parameters into adsorbent parameters, operating parameters, and solution components. Three tree-based algorithms—Random Forest (RF), Gradient Boosting Decision Trees (GBDT), and Extreme Gradient Boosting (XGBoost)—were used to evaluate the impact of these parameters on lithium adsorption. The grouped random splitting method limited data leakage and mitigated overfitting. XGBoost demonstrated the best performance, with an R² of 0.98 and a root-mean-squared error (RMSE) of 1.72. The SHAP values highlighted that operating parameters were the most influential, followed by adsorbent parameters and coexisting ion concentrations. Therefore, focusing on optimizing operating parameters or making targeted improvements on LIS based on operating conditions will enhance LIS performances in UWS. These insights are crucial for optimizing Li adsorption processes and designing effective inorganic LIS materials.

Evaluation of large-scale poultry manure-derived biochar for efficient cadmium removal in zinc smelter wastewater

Cadmium (Cd), a carcinogen, is released from industrial activities like metal refineries and battery runoff, with significant contamination reported near zinc smelters in Korea. This study addresses the issue using an efficient, economical adsorption process with waste-derived biochar-based adsorbents known for high Cd removal. Poultry manure (PM), typically used as fertilizer, can lead to environmental pollution if mismanaged; therefore, it was pyrolyzed to produce biochar. The resulting poultry manure biochar (PMBC) was produced on a large scale (15 ton/day), demonstrating feasibility for large-scale implementation. The effectiveness of PMBC as an adsorbent for Cd was evaluated using wastewater discharged from a zinc smelter. The Cd adsorption capacity of PMBC (60.39 mg/g) was lower than that (302.0 mg/g) of hen manure biochar produced at a laboratory scale in our previous study but was comparable to other biochars reported in the literature. Response surface methodology analysis indicated that reaction time, dose, and agitation significantly influenced Cd removal by PMBC, whereas pH had a negligible impact. Notable contributions to Cd adsorption include the release of K+ from PMBC and the presence of O-containing functional groups. Under continuous flow conditions with real wastewater, Cd was not detected in the effluent for the initial 8 h, and PMBC sustained a removal efficiency of 40.77% until saturation was reached. The results from wastewater treatment and large-scale biochar production offer valuable insights into the potential of biochar as a medium for addressing environmental issues in real-world applications.

Study on the Phosphate Compound Adsorption onto MgO-KOH/Biochar Adsorbent as Binding Agent in Diffusive Gradient in Thin Film (DGT) Technique for Bioavailable Phosphate Detection

Phosphate compounds, particularly bioavailable forms like PO₄³⁻, are critical contributors to eutrophication. In this study, MgO-KOH/biochar was used as a binding agent in the Diffusive Gradient in Thin Films (DGT) technique to enhance phosphate detection. The adsorbent was synthesized from biochar derived from palm oil waste, activated with KOH to increase surface area, and combined with MgO for enhanced adsorption efficiency. The adsorption process followed a pseudo-second-order kinetic model, indicating that chemical interactions dominated the adsorption mechanism. Under different pH levels and phosphate concentrations, the material showed a good selectivity for orthophosphate, achieving an adsorption capacity of approximately 100 mg/g. Characterization via FTIR, XRD, and SAA confirmed the successful synthesis of MgO-KOH/biochar and its structural properties, which contributed to its performance. Additionally, the MgO-KOH/biochar DGT device demonstrated better efficiency in adsorbing PO₄³⁻ compared to conventional ferrihydrite-based DGT systems, positioning it as a highly effective tool for monitoring bioavailable phosphates in aquatic environments. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Investigation of the iridium adsorption process with functionalized magnetic nanoparticles using triisobutylphosphine sulfide extractors

In this research work, the adsorption process of iridium using magnetic nanoparticles functionalized with Cyanex 471X has been investigated. In this regard, parameters affecting the adsorption process such as pH, initial concentration of iridium ions, contact time and adsorbent dosage were assessed. According to the results, pH 6, adsorbent dosage 1.2 g/L, initial concentration of iridium of 10 mg/L, and contact time of 10 min were selected as optimal conditions for iridium adsorption by this synthesized magnetic nanosorbent. The kinetics of the adsorption process was studied, and it was found that the adsorption reaction follows the pseudo-second-order kinetic model with the correlation coefficient of 0.9960. Also, experimental studies indicated that the Langmuir adsorption isotherm model best matches the experimental data (R2 = 0.9961). The maximum adsorption capacity of the nanosorbent for iridium adsorption was estimated to be 35.34 mg/g by the Langmuir isotherm. With the thermodynamic analysis of the adsorption process, it was found that this process is endothermic and spontaneous. In addition, in the investigation of iridium adsorption and desorption, HCl/HNO3 solution with a concentration of 1.5 M was selected as suitable eluent.

Microemulsion Templating Synthesis of Hierarchical Porous Ag‐Doped SiO2‐TiO2 Composites for Efficient Degradation of Noxious Methylene Blue Dye: Effect of Calcination Environment

AbstractWe report herein a dual function mesoporous structure of titanium oxide based porous carbon with large surface‐to‐volume ratios for efficient degradation of noxious methylene blue dye (MB) from an aqueous environment. The mesoporous photocatalysts is fabricated via direct template synthesis of highly ordered silica‐titania monolith doped with Ag0/Ag2O starting from a quaternary microemulsion liquid crystalline phase. The produced monoliths are subjected in‐situ to doping by growing silver, in the cubic cavities, and on the silica/titania structure's domain. This study investigated the efficiency of novel composite materials, consisting of silver‐doped silica‐titania (SiO2/TiO2), which is synthesized using the microemulsion templating approach. The photocatalytic performance of the synthesized composite in the photodegradation of MB has been studied. The procedure of photodegradation was employed to achieve decolorization of the cationic MB dye using visible light. The catalyst effectively achieved the decolorization of the dyed solution through the processes of adsorption and photodegradation. The composite consisting of SiO2, TiO2, and Ag2O at a ratio of 1 : 1:0.5, which underwent calcination in an air environment (AgOST), exhibited a removal efficiency of 99 % compared to its calcined state under argon (AgSTC).

Effects of pyrolysis temperatures on the structural properties of straw biochar and its adsorption of tris-(1-chloro-2-propyl) phosphate

To investigate the effect of pyrolysis temperature on the adsorption behavior of the emerging organic pollutant tris-(1-chloro-2-propyl) phosphate (TCIPP) on biochar, corn stover was used as raw materials to prepare biochars at different pyrolysis temperatures (250, 350, 500, 700 °C) through limited oxygen carbonization. Elemental analysis, Boehm titration, FTIR, XPS, and other analytical methods were used to reveal the effect of pyrolysis temperature on the physicochemical properties of biochar and its mechanism of TCIPP adsorption. The results showed that the pyrolysis temperature had a significant impact on the physicochemical properties of biochar. As the pyrolysis temperature increases, the specific surface area of biochar rises from 3.083 m2/g to 435.573 m2/g, the pH value increases from 6.60 to 10.66, the mass percentage of C increases from 63.10 to 80.58%, and the mass percentage of O decreases from 26.42 to 9.20%. Additionally, the hydrophobicity and aromaticity of biochar also increase with rising pyrolysis temperature, while its polarity decreases. Boehm titration, FTIR, and XPS analysis showed that the total amount of functional groups on the surface of biochar decreased relatively with increasing temperature. Functional groups such as -OH, C = C/C = O, and C-O-C participated in the adsorption of TCIPP on biochar, and ester groups were produced after adsorption. The adsorption process of TCIPP on biochar fits best with the pseudo-second-order equation, indicating that the adsorption process is mainly chemical adsorption, and the main rate-controlling stage is intraparticle diffusion. The isothermal adsorption results were more in line with the Temkin model, indicating that the adsorption process of TCIPP on biochar was mainly surface adsorption. As the pyrolysis temperature increases, the maximum adsorption capacity of biochar increases from 0.8837 mg/g to 2.2574 mg/g. The adsorption process of TCIPP on biochar mainly included pore filling, hydrogen bonding, P-π interaction, hydrophobic interaction, and electrostatic attraction. Among them, pore filling, P-π interaction, and hydrophobic interaction were significantly enhanced with increasing temperature, while hydrogen bonding was relatively weakened. This study will provide a theoretical basis and technical support for the removal of TCIPP from water using biochar adsorption.

Preparation of CYCU‐3/MCM‐41 Composites and Adsorption Properties for n‐Hexane

AbstractAdsorption method is one of the effective technologies for treating VOCs. Compared with activated carbon, silicon‐based materials have well‐ordered pore structure, good thermal stability and non‐flammability. In this paper, CYCU‐3/MCM‐41 composites were prepared by hydrothermal method through mixing MCM‐41 powder in situ. The nitrogen adsorption isotherms, saturation adsorption and cyclic adsorption/desorption curves of n‐hexane on CYCU‐3/MCM‐41 composites were experimentally measured. The results displayed that the CYCU‐3/MCM‐41 (3) exhibited the largest BET specific surface area (1631 m2/g). And its n‐hexane adsorption capacity was 776 mg/g, which was 19.4 % higher than that of MCM‐41, 1.42 times that of activated carbon, and 2.64 times that of molecular sieve. The kinetic fitting results showed that the pseudo‐first order kinetic model can more precisely embody the n‐hexane adsorption process on CYCU‐3/MCM‐41 composites, and the W‐M intraparticle diffusion model confirmed that intraparticle diffusion was not the only control step for the adsorption rate of n‐hexane on CYCU‐3/MCM‐41 composites. In addition, the regenerative rate of CYCU‐3/MCM‐41 (3) was over 98.9 % after ten adsorption and desorption cycles of n‐hexane, showing good desorption performance and excellent structural stability, and proving its broad application prospect in the field of VOCs treatment.

Adsorption Thermodynamics for Process Simulation.

Adsorption has rapidly evolved in recent decades and is an established separation technology extensively practiced in gas separation industries and others. However, rigorous thermodynamic modeling of multicomponent adsorption equilibrium remains elusive, and industrial practitioners rely heavily on expensive and time-consuming trial-and-error pilot studies to develop adsorption units. This article highlights the need for rigorous adsorption thermodynamic models and the limitations and deficiencies of existing models such as the extended Langmuir isotherm, dual-process Langmuir isotherm, and adsorbed solution theory. It further presents a series of recent advances in the generalization of the classical Langmuir isotherm of single-component adsorption by deriving an activity coefficient model to account for the adsorbed phase adsorbate-adsorbent interactions, substituting adsorbed phase adsorbate and vacant site concentrations with activities, and extending to multicomponent competitive adsorption equilibrium, both monolayer and multilayer. Requiring a minimum set of physically meaningful model parameters, the generalized Langmuir isotherm for monolayer adsorption and the generalized Brunauer-Emmett-Teller isotherm for multilayer adsorption address various thermodynamic modeling challenges including adsorbent surface heterogeneity, isosteric enthalpies of adsorption, BET surface areas, adsorbed phase nonideality, adsorption azeotrope formation, and multilayer adsorption. Also discussed is the importance of quality adsorption data that cover sufficient temperature, pressure, and composition ranges for reliable determination of the model parameters to support adsorption process simulation, design, and optimization.

Endoxylanase Immobilized Nanoporous Silica for the Production of Xylooligosaccharides: Equilibrium Kinetics, Thermodynamic Studies, and Enzyme Characteristics

AbstractNanoporous structured silica materials, namely f‐SiO2, SBA‐15, IITM‐41, and MCM‐41 were employed as the matrices for immobilizing endoxylanase by adsorption method. The equilibrium kinetics, activation energy, and thermodynamic parameters associated with endoxylanase adsorption were investigated. Our findings revealed a two‐phase adsorption mechanism: an initial phase featuring rapid adsorption rates, succeeded by a slower phase wherein adsorption gradually progressed until equilibrium was attained. Analysis of the adsorption kinetic data indicated a better fit with the pseudo‐second‐order model, suggesting chemisorption and highlighting its temperature dependency. The calculated activation energy (Ea) values fell within the range of physisorption, indicating the involvement of both types of adsorption processes. Thermodynamic assessments confirmed that the adsorption reactions were spontaneous, feasible, and endothermic. Notably, the immobilization process did not change the optimum pH of the enzyme, while the optimum temperature shifted slightly. Furthermore, immobilized enzymes show a higher reaction rate (Vmax) than the soluble XynC. All immobilized xylanases produced xylobiose (X2) to xylohexose (X6) by hydrolyzing the xylan substrate. Recycling studies showed that up to 80 % of the yield was retained after seven cycles of reuse. Our study demonstrates the potential of nanostructured silica as an effective immobilization matrix for enzymes of industrial significance.