Adsorption Model Research Articles

An Instructive CO2 Adsorption Model for DAC: Wave Solutions and Optimal Processes

We present and investigate a simple yet instructive model for the adsorption of CO2 from air in porous media as used in direct air capture (DAC) processes. Mathematical analysis and non-dimensionalization reveal that the sorbent is characterized by the sorption timescale and capacity, while the adsorption process is effectively wavelike. The systematic evaluation shows that the overall adsorption rate and the recommended charging duration depend only on the wave parameter that is found as the ratio of capacity and dimensionless air flow velocity. Specifically, smaller wave parameters yield a larger overall charging rate, while larger wave parameters reduce the work required to move air through the sorbent. Thus, optimal process conditions must compromise between a large overall adsorption rate and low work requirements.

Removal of Phosphate from Water by Iron/Calcium Oxide-Modified Biochar: Removal Mechanisms and Adsorption Modeling

Phosphorus (P) pollution is a leading cause of water eutrophication, and metal-modified biochar is an effective adsorbent with the ability to alter the migration capacity of phosphorus. This study uses bamboo as the raw material to prepare metal-modified biochar (ZFCO-BC) loaded with Fe and Ca under N2 conditions at 900 °C, and investigates its adsorption characteristics for phosphate. Batch experimental results show the adsorption capacity of the ZFCO-BC gradually increases (from 4.0 to 69.1 mg/g) as the initial phosphate concentration increases (from 2 to 900 mg/L), mainly through multilayer adsorption. Additionally, as the pH increases from 1 to 7, the adsorption capacity of the ZFCO-BC climbs to reach its maximum value of 48.4 mg/g with an initial phosphate concentration of 150 mg/L. At this pH, phosphate primarily exists as H2PO4− and HPO42−, which both readily react with Fe3+ and Ca2+ in the biochar. Furthermore, the addition of CO32−, HCO3−, NO3−, SO42−, F−, and Cl− each affect the removal rate of phosphate by less than 10%, indicating the ZFCO-BC has a highly efficient and selective phosphate adsorption capacity. A multi-column adsorption experiment designed to achieve long-term and efficient phosphorus removal treated 275.5 pore volumes (PVs) of water over 366 h. The cyclic adsorption–desorption experiment results show that 0.5 M NaOH can effectively leach phosphate from the ZFCO-BC. Observations at the molecular level from P K-edge XANES spectra confirm the removal of low-concentration phosphate is primarily dominated by electrostatic attraction, while the main removal mechanism for high-concentration phosphate is chemical precipitation. This study demonstrates that ZFCO-BC has broad application prospects for phosphate removal from wastewater and as a potential slow-release fertilizer in agriculture.

In Situ Potentiometric Monitoring of Nitrate Removal from Aqueous Solution by Activated Carbon and Ion Exchange Resin

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed.

Removal of Cr(VI) from aqueous phase using dimethylaminopropylamine anchored polystyrene‐co‐divinylbenzene polymer as adsorbent

AbstractThe current investigation delves into the effectiveness of dimethylaminopropylamine tethered onto polystyrene‐co‐divinylbenzene polymer for the proficient elimination of hexavalent chromium from simulated wastewater. The resin was characterized using SEM, FT‐IR spectroscopy, EDX, elemental analysis, thermogravimetry, and solid state 13C NMR spectroscopy. The experimental investigation into sorption dynamics involved varying process parameters, including initial Cr(VI) concentration, amount of adsorbent used, solution pH, temperature, and contact between phases. The binding modes of chromate ions, either bidentate or monodentate, were observed, with their manifestation influenced by the solution's pH. Sorption capacity was found to be pH‐dependent, with removal efficiencies of 98.27%, 96.38%, and 85.52% observed at pH levels of 3, 6, and 9, respectively. PS‐DMAPA resin demonstrated robust regeneration capabilities, throughout five consecutive adsorption–desorption cycles. The Langmuir adsorption model exhibited excellent agreement with the experimental findings (R2 = 0.9994), revealing a maximum adsorption capacity of 70.15 mg g−1 at 298 K. Additionally, the experimental findings closely matched the second‐order kinetic model. The kinetics of sorption and the thermodynamic parameters were also investigated. Performance evaluating of the PS‐DMAPA resin under dynamic conditions included analyzing the Cr(VI) breakthrough curve. The 10% sodium chloride solution was employed to effectively recover the extracted Cr(VI) quantitatively.

Predictive Modeling and Adsorption Behavior, Kinetics, and Thermodynamic Studies of <i>Anthocleista grandiflora </i>Leaf Extract for Corrosion Inhibition of Carbon Steel in Seawater

This study investigates the corrosion inhibition performance of Anthocleista grandiflora leaf (AGL) extract on carbon steel in seawater, considering the effects of temperature, immersion time, and inhibitor concentration. Predictive modeling, adsorption behavior, and the kinetics and thermodynamics of the inhibition process were examined. The weight loss technique,characterization techniques combined with response surface methodology (RSM), revealed that the AGL extract follows the Langmuir adsorption model, exhibiting physical adsorption with ΔG values between −16.24 to −15.49kJ/mol, indicating spontaneous and endothermic inhibition. The thermodynamic parameters entropy (−198.87 to −52.58 J/mol), enthalpy (20.42 to 53.42 kJ/mol), and activation energy (13.68 to 56.32 kJ/mol further support this. The corrosion reaction follows first-order kinetics, with the half-life decreasing as the rate constant and extract concentration increase.The SEM images revealed that the AGL extract formed a protective surface layer on the mild steel, effectively preventing pitting. This protective effect became more pronounced as the concentration of the extract increased. RSM optimization identified optimal conditions for maximum inhibition efficiency (98.70%) and corrosion rate (0.058 mm/y) at 800 ppm, 303 K, and 45 days, with a prediction accuracy of 95%, making it suitable for application in the oil and gas industry.

A model of random sequential adsorption on a ladder graph

A model of random sequential adsorption on a ladder graph

Modeling and Optimization of Cadmium and Lead Adsorption onto Natural Pterocarpus santalinoides Fruit

The presence of heavy metals in wastewater has raised concern in developing countries because of their impact on human health and environmental ecology. Therefore, this study aims to remove cadmium and lead ions from wastewater using natural Pterocarpus santalinoides fruit through the adsorption method. The Box-Behnken design (BBD) of the response surface methodology (RSM) method was adopted to optimize the process variables such as contact time (20-100 min), adsorbent dose (0.1-0.5 g), initial metal ion concentration (10-50 mg/l), and temperature (30-70 °C). The ANOVA results clearly indicate that the linear model was not sufficient to best predict the removal performance of cadmium (R2 = 0.4009) and lead (R2 = 6353). The optimum conditions for the maximum Cd (94.81%) and Pb (89.23 %) adsorption onto the adsorbent were achieved at contact time (42.16 min), adsorbent dose (0.25 g), initial metal ion concentration (21.52 mg/l), and temperature (37.00 °C). According to the findings of the present work, Pterocarpus santalinoides shows to be a potential eco-friendly and cheap adsorbent for the removal of Cd and Pb from aqueous solutions. The BBD-RSM actual and predicted values of the Cd and Pb ions response show non-significant correlation, suggesting poor agreement between the two, revealing that the BBD-RSM model applied is not effective for the relationship between the four parameters examined in the Cd and Pb ions removal process.

Cascade Reactions for Enhanced CO2 Capture: Concurrent Optimization of Porosity and N‐Doping

AbstractCarbon capture emerges as a pivotal decarbonization technology for addressing global warming challenges. Porous carbons, despite their cost‐effectiveness and ease of regeneration for CO2 capture, typically exhibit limited capacity owing to insufficient adsorption sites. Here, nitrogen‐doped porous carbons (NPCs) are introduced that overcome the prevalent trade‐offs between specific surface area and N‐doped content in NPCs fabrication through cascade reactions. The optimized NPC, which features hierarchical porosity ranging from ultra‐micropores to macropores, shows a superior CO2 capture capacity of 4.46 mmol g−1, ranking in the top 10% of the reported NPCs. This capacity exceeds that of the NPC fabricated with the conventional method by 58% and surpasses the control porous carbon by 106%. Langmuir adsorption modeling and mathematic correlation analysis revealed that this enhanced capacity is attributed to significantly improved ultra‐micropores volume and nitrogen‐species content. Moreover, this optimized NPC demonstrates exceptional stability, preserving its adsorption performance over 110 adsorption–desorption cycles under simulated flue gas conditions. This research not only highlights the integration of templating and N‐doping within NPCs fabrication but also offers an effective strategy to optimize porosity and nitrogen functionality in carbon materials, advancing beyond conventional methodologies.

A novel corrosion inhibitor for copper in sulfuric acid media: Complexation of iodide ions with Benincasa Hispida leaf extract

In the context of green and low-carbon development, the rapid development of industry brings the problem of metal corrosion costs increase, metal corrosion protection methods are of great concern. Extracts from Benincasa hispida leaves (BHLE), which were obtained through pressurised liquid extraction, were employed as a inhibitor for copper corrosion in 0.5 M H2SO4. Their composition and anti-corrosion properties were subsequently analyzed and evaluated. The electrochemical analysis results indicated that BHLE functions as a cathodic-type corrosion inhibitor. The anti-corrosion performance intensifies with the increase in concentration but diminishes gradually as the temperature rises, when the concentration of BHLE is 400 mg/L, the corrosion inhibition efficiency can reach 91.82 %, when the concentration of added potassium iodide reaches 16 mg/L the slow-release efficiency of the compounded corrosion inhibitor reaches 96.92 %. The addition of I− strengthens the inhibition efficiency through the adsorption form dominated by competitive adsorption. The adsorption of BHLE onto the surface of copper follows the Langmuir monolayer adsorption model.

Exploring Geometric Properties and Cycle Design in Packed Bed and Monolith Contactors Using Temperature-Vacuum Swing Adsorption Modeling for Direct Air Capture

Exploring Geometric Properties and Cycle Design in Packed Bed and Monolith Contactors Using Temperature-Vacuum Swing Adsorption Modeling for Direct Air Capture

A model characterising the fractal supercritical adsorption behaviour of methane in shale: Incorporating principles, methods, and applications

The pore structure of shale is patently heterogeneous, with a conventional adsorption model being difficult to characterise the complex adsorption behavior of methane in shale. Therefore, a model is being proposed to characterise the fractal supercritical adsorption behavior of methane in shale. The principles and derivation of the model have been described in detail. The results showed that the adsorption characteristic parameters relating to different scale pores were affected by temperature and fractal dimension to different degrees. In addition, the relationship between isosteric heat of adsorption (qst) and adsorption capacity of different samples revealed different trends. The absolute values of ΔS of FC-66 and FC-72 decreased linearly. This might have been because of the fact that the adsorption saturation’s inflection point, which caused a fall in the absolute value of the entropy change (ΔS), was not reached. Compared with traditional adsorption models, the proposed model could reflect menthane’s adsorption in shale more accurately. The research results provide theoretical support for the evaluation of deep shale gas reserves, including the optimisation of exploitation strategies.

A Systematic Approach for Estimating Colloidal Particle Adsorption Model Parameters

The estimation of ion- exchange chromatography model parameters is crucial to enable efficient model-assisted biopharmaceutical downstream process development. Model calibration methods can be hindered by model limitations combined with parameter correlations, leading to time-consuming repeated parameter estimations. While Steric Mass Action isotherm estimation methods exist, there is a need for a systematic approach to estimate model parameters for an emerging Colloidal Particle Adsorption (CPA) model proposed by Briskot et al. This study presents a novel strategy that addresses this challenge, offering significant improvements.Through a parameter sensitivity analysis, we identified key levers for improved CPA parameter estimation, enabling the prediction of elution behavior for low and high load densities in gradient and step elution mode. This analysis also revealed the correlation structure of parameters, allowing the establishment of a minimalized experimental data set for parameter estimation, by using one breakthrough, a high load and three low load density gradient elution experiments. Our workflow leverages a surrogate-assisted global-optimization tool, minimizing computationally expensive function evaluations during parameter fitting. Furthermore, we employed a customized objective function, specifically adapted to the model structure and sensitivity results, to enhance the solver's performance.Our strategy was tested on three model proteins with molecular weights of approximately 50, 150 and 200 kDa using a strong cation exchange Poros 50 HS resin. Our final approach enabled high throughput CPA model calibration for single components. The resulting CPA models were able to describe non-binding protein-pulses, low and high-loaded gradient elution, break through, as well as isocratic elution experiments.

Fast and effective adsorption of Ce3+ by phosphate-functionalized ZIF-67-derived layered double hydroxides

In this experiment, phosphate (sodium hexametaphosphate) was used as an intercalation modifier and ZIF-67 as a precursor mixed with Al(NO3)3·9H2O Nanolayered double hydroxides P-Co-Al-LDH with hexametaphosphate group intercalation were prepared in a hydrothermal environment and characterized by SEM, FT-IR, XRD, TGA, SEM and XPS. The adsorption performance of P-Co-Al-LDH and control Co-Al-LDH on Ce3+ under different adsorption conditions was firstly investigated by optimization experiments. It was determined that the best adsorption effect of P-Co-Al-LDH was achieved at pH=6, and the fast equilibrium adsorption state was achieved within 30 min, with the adsorption amount reaching 220.98 mg/g and the adsorption efficiency reaching 72.66%. In addition, kinetic, isothermal adsorption and thermodynamic modeling explored the adsorption mechanism of Ce3 + by nanodiamond P-Co-Al-LDH mainly the complexation of functional groups in sodium hexametaphosphate with metal ions greatly improved the adsorption performance. Several regeneration experiments were carried out to evaluate the stability and reusability of the adsorbent. After three cycles of adsorption, the adsorption efficiency was still maintained at 83.26%.

Efficient recovery of Pd(II) from nuclear wastewater using a functionalized covalent organic frameworks with uniform spherical structure: Size control, performance and mechanism insight

The efficient recovery of palladium from the spent nuclear fuel was of great significance to the sustainable development of nuclear energy. Herein, the uniform spherical COFs were constructed by a facile approach at room temperature, which were further surface functionalized by a thiol-ene “click” reaction to recover Pd(II). Microscopic and spectroscopic studies manifested that the formation mechanism and size of spherical COFs were greatly affected by the amount of catalyst and solvent type. The TAPB-BPTA-DTT and TAPB-BPTA-S-β-CD exhibited high Pd(II) recovery efficiency due to the introduction of sulfhydryl groups, and the maximum adsorption capacities were 489.3 and 234.3 mg/g, respectively. Meanwhile, the water environmental condition played an important role in the separation process, and the classical adsorption models demonstrated that monolayer chemisorption was the dominant removal mechanism. Mechanism analysis showed that the excellent adsorption performance was mainly attributed to the electrostatic interaction, physical absorption and chelation of N, O, and S groups with Pd(II). Thus, it is expected that this work could provide more insight into COFs materials, thereby promoting palladium removal advancements in the spent nuclear fuel.

Adsorption behavior and mechanism of lead by starch/tobermorite composite hydrogel.

Tobermorite (TOB) is a synthetic inorganic mineral material with a montmorillonite-like layered structure that removes heavy metals from water, and its incorporation into starch-based hydrogels can optimize the stability and adsorption properties of the hydrogels; it can also significantly reduce the storage pressure of fly ash (FA) and reduce environmental pollution. This study utilized starch/tobemolite/acrylic acid (LR/TOB/AA) as the raw material, successfully synthesizing a starch-tobemolite composite hydrogel (LR-TOB/AA) using aqueous solution polymerization. The hydrogel exhibits excellent water absorption and retention capabilities, as well as a significant adsorption effect on Pb(II). The influence of adsorption duration, starting concentration, temperature, and hydrogel incorporation on Pb(II) adsorption was examined by intermittent adsorption experiments. The maximal adsorption capacity of Pb(II) was 900.25 mg/g, surpassing the majority of reported hydrogel adsorbents, as determined by Langmuir isothermal adsorption model fitting. Following five adsorption-desorption cycles, the hydrogel's adsorption of Pb(II) persisted above 90 %.

Magnetic bentonite with organic modification highly efficient for adsorption of Ce(III) and Y(III)

A simple organic magnetic adsorbent (PAA-MBent) was synthesized using 2-hydroxyphosphonylacetic acid and applied to the adsorption of Ce(III) and Y(III). It was confirmed that the phosphoryl groups could effectively regulate the homogeneous loading of magnetic particles on the bentonite during the synthesis process, and the hydroxyl and phosphoryl groups can be sufficiently used on the surface of bentonite to increase the abundance of adsorption sites, which have favorable coordination with Ce(III) and Y(III). The experimental results showed that the maximal adsorption capacity was increased to 99.11 mg/g and 65.65 mg/g for Ce(III) and Y(III), respectively, which was 2.52 and 2.91 times higher than magnetic bentonite. The adsorption behavior conformed to the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model, and the adsorption of Ce(III) by PAA-MBent performed better than that of Y(III). The adsorption efficiency was affected by ionic strength and site inhibition of coexisting cations, and its adsorption selectivity was mainly disturbed by the competition of Al ions. The results after adsorption identified the key adsorption mechanisms as ion exchange, electrostatic attraction, functional group complexation, and hole filling. After five cycles, the adsorbent still exhibited good adsorption and magnetic recovery performance. These results reveal that PAA-MBent is promised to be a novel, inexpensive and effective adsorbent for the removal of Ce(III) and Y(III) from contaminated water.

Revisiting the persulfate activation performance of seaweed derivied biochars: The composition and origin of pollutant degradation activity

A steady increase in seaweed production necessitates effective strategies to manage its post-production waste and its assosicated CO2 emission. Biochar formation stand out as a promising option, offering significant advantage for persulfate-activated water remediation processes. Herein, we investigated and compared the performance of two seaweed-derived biochars, focusing on their physical characteristics, heteroatoms, and chemical composition in activating persulfate (PS). Although, both seaweeds (Capsosiphon fulvescens (CF) and Undaria pinnatifida (SW)) that studied are edible, they exhibit unique catalytic behavior in the degradation of simazine (SMZ). The differences in simazine degradation activity observed in these biochars were primarily attributed to the description of metal active sites rather than the complex composition and specific surface area of the biochars. The identification of these active sites was achieved through various physical characterization tools (XRD, XPS, BET) and by examining the adsorption models and degradation patterns of simazine under different conditions. Our results demonstrate that the biochar derived from CF (100% removal) seaweed having metal active centres is more catalytic than SW (58.4% removal) derived biochar. ROS quantification and electrochemical studies suggest that simazine degradation occurs through different mechanisms in these biochars. Therefore, the CF-derived biochar catalytic system was optimized for simazine oxidation, with studies focusing on its degradation pathway, intermediate toxicity, and catalytic stability. This comprehensive study outlines the significance of selection of seaweed biomass for optimal activity in the persulfate-based oxidative system.

Biochar derived from straw residue prepared via combined pre-treatment designed for efficient removal of tetracycline hydrochloride and sulfadiazine sodium salt

In this study, straw residue (SR) was prepared from corn straw by a combined pre-treatment method that involved both microbial treatment (Myrothecium verrucaria, Aspergillus niger, and Trichoderma reesei) and treatment with ρ-toluenesulfonic acid. After pre-treatment, the cellulose content of the residues reached 79.3 %, 72.1 %, 83.5 %, and 85.2 %, respectively. The results indicated that Aspergillus niger and Trichoderma reesei effectively destroyed the corn stover structure, improving the efficiency of the subsequent treatment. Following carbonation and activation processes, the SRs were converted into a series of biochars (ACCC, ACMC, ACTC, and ACNC) with large specific surface areas (2343, 2219, 2693, 2672 m2 g−1). The prepared biochars demonstrated excellent performance in adsorption tests performed using tetracycline hydrochloride (TC) and sulfadiazine sodium salt (SDZ) as adsorption models. The maximum adsorption capacities recorded for TC (908, 1117, 1216, and 1189 mg/g) and SDZ (930, 965, 1033, and 1083 mg/g) were higher than most of the other adsorbents. Furthermore, the potential adsorption mechanisms included pore filling, π-π interactions, hydrogen bonding, and electrostatic attraction. Even after 5 test cycles, the biochar retained over 75 % of its adsorption performance, highlighting its strong potential for applications in removing antibiotics from water.

Transport and competitive interfacial adsorption of PFOA and PFOS in unsaturated porous media: Experiments and modeling

Among emerging contaminants, per- and polyfluoroalkyl substances (PFAS) have captured public attention based upon their environmental ubiquity and potential risks to human health. Due to their typical surface release conditions and amphiphilic properties, PFAS tend to sorb to soil and accumulate at the air-water interface within the vadose zone. These processes can result in substantial plume attenuation. Although there is a growing body of literature on vadose zone transport, few studies have explored PFAS mixture transport, particularly under conditions where nonlinear sorption processes are important. The present study aims to advance our understanding of PFAS transport in variably saturated porous media through integration of experiments and mathematical modeling. Experiments include batch studies to quantify sorption to the solid phase, interfacial tension (IFT) measurements to estimate adsorption at the air-water interface (AWI), and column studies with F-70 Ottawa sand at 100 % and ca. 50 % water saturation to explore transport mechanisms. Employed PFAS solutions encompass individual solutes and binary mixtures of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentration levels spanning four orders of magnitude to assess competitive and nonlinear sorption at the AWI. Observations demonstrate that concentration levels and competitive effects substantially influence PFAS transport in unsaturated systems. In the presence of PFOS, PFOA experienced less retention than would be anticipated based on single-solute behavior, and effluent breakthrough curves exhibited chromatographic peaking. The presented mathematical model for simultaneous flow and transport of PFAS was able to capture experimental observations with a consistent set of parameters and minimal curve fitting. These results demonstrate the robustness of the model formulation that included rate-limited interfacial mass transfer, an extended Langmuir-Szyszkowski model for adsorption at the AWI, and a scaled Leverett thermodynamic model to predict the AWI specific area. Overall, the results of this work underscore the importance of the AWI in PFAS transport and highlight the relevance of competition effects in adsorption formulations.

Poly (acrylic acid-co-2-hydroxyethyl methacrylate)-grafted gum ghatti hydrogel for capturing heavy metal ions

In this work, a facile route is explored for the synthesis of a novel polymer composite-based hydrogel (PC-hydrogel). The ratio of 2-(Hydroxyethyl) methacrylate (HEMA) and acrylic acid (AA) is optimized first based on Fourier transform infra-red spectroscopy, swelling ratio (SR%) and surface negative charge (PZC). Results indicate that PC-hydrogel composed of copolymer of HEMA: AA in 1:4 ratio is optimized, for grafting on Gum ghatti (Gg) during free-radical graft copolymerization process. Among all other possible combination of HEMA: AA, 1:4 ratio grafted Gg is termed as PC-hydrogel [Poly (AA-co-HEMA)-g-Gg]. PC-hydrogel exhibited negative surface charge over a wide range of pH owing to increase in AA. The swelling (g/g) and water retention ratio (%) of the prepared hydrogel have been found to be 342.6, 385 & 412.6 g/g and 74.83, 65.30 & 57.86 % in grey, tap and distilled water respectively. Furthermore, PC-hydrogel is applied for capturing Cu2+ and Co2+ ions in aqueous phases. Experimental results showed that adsorption process was pH-dependent, and the maximum capturing of Cu2+ and Co2+ was observed at neutral pH 7. Among different adsorption isotherms models like Langmuir, Freundlich, and Temkin models, experimental data fitted closely with the Langmuir adsorption model showing a maximum adsorption capacity of 381.67 and 328.94 mg/g for Cu2+ and Co2+ respectively. The capturing of metal ion followed pseudo-second-order rate model [rate constant k = 1.7 x 10−4 for Cu2+ and 1.5 x 10−4 for Co2+ g/(mg.min)]. The PC-hydrogel property retained its uptake capacity of metal ions up to the three successive adsorption−desorption cycles, and exhibited higher selectivity towards Cu2+ and Co2+ and other (NaCl, MgCl2, CaCl2) coexisting ions.