Yoon-Nelson Models Research Articles

The Dynamic Behaviour of a Binary Adsorbent in a Fixed Bed Column for the Removal of Pb2+ Ions from Contaminated Water Bodies

In the search for a technically efficient and abundant adsorbent in water treatment processes, a bio-composite adsorbent derived from agricultural wastes has been identified as a potential candidate. In this study, eggshells and sugarcane bagasse were combined in varied proportions (1:0, 1:3, 1:1, 3:1 and 0:1) and applied as biosorbents in a lab-scale adsorption column. The effect of bed depth (4–12 cm) of the biosorbents was investigated which enabled the prediction of breakthrough curves for the removal of Pb (II) ions. The life span of the column was extended by increasing the bed depth of the column. The binary adsorbent of 1:3 weight ratio of <75 µm particle size showcased the highest removal efficiency of 91% at a bed depth of 12 cm. The mass transfer zone (MTZ) increased with increasing bed depth with a minor portion of the bed left unused, signifying that the process was highly efficient. The Thomas model constant, KTh, decreased with increasing bed depth with the maximum amount of Pb adsorbed being 28.27 mg/g. With the Yoon–Nelson model, KYN decreased with an increase in τ as the bed height increased. In this study, a novel approach was adopted where the proposed methodology enabled the use of a bio-composite adsorbent in heavy metal removal. The findings of this research will aid in the design and optimisation of the pilot-scale operation of environmentally friendly treatment options for metal laden effluent.

Continuous silicic acid removal in a fixed-bed column using a modified resin: Experiment investigation and artificial neural network modeling

In this study, the suitability of a novel modified resin (gallic acid modified resin: GA-type resin) for silicic acid removal was investigated using fixed-bed column adsorption. Laboratory dynamic experiments were conducted at different flow rates, bed heights and influent concentrations. With rising flow rate, the breakthrough time, exhaust time and absorption capacity of the column bed decreased while increasing with column bed height. With the increasing influent concentration from 20 mg/L to 60 mg/L, decrease in both breakthrough time and exhaust time, but an increase in adsorption capacity from 3.73 mg/g to 4.20 mg/g. To simulate the experimental breakthrough curves (BTCs) and predict the column dynamics, basic and empirical models (Bed Depth-Service Time (BDST), Thomas, and Yoon-Nelson models) as well as an artificial intelligence approach (Artificial Neural Network (ANN) model) were applied. All three conventional models were able to reflect well the behavior for silicic acid continuous adsorption with GA-type resin and estimated the characteristic model parameters for removal. ANN model had a higher accuracy (R2 = 0.9997) in predicting BTCs and predicting breakthrough times. Analyzing the parameters obtained from the simulation of the ANN model, the initial concentration was found to have the highest relative importance of 32.94 %, and the specific order of relative importance was as follows: initial concentration > column height > flow rate > total running time. Furthermore, due to its certain regeneration potential, GA-type resin can be recycled, making it a promising material for removing silicic acid from water.

Silver ions and silver nanoparticles removal by coffee derived biochar using a continuous fixed-bed adsorption column

Even low concentration monovalent silver (Ag+) and silver nanoparticles (Ag NPs) are emerging environmental threats, seeking an eco-friendly and cost-effective continuous treatment process to mitigate their pollution. In this study, an attempt has been made to investigate the potential of spent coffee grounds (SCGs) biochar in a fixed-bed column, to remove silver ions and silver nanoparticles from wastewater. A series (adsorption and desorption) of fixed-bed column experiments were performed under different operating conditions to determine the breakthrough curves (BTCs) and understand the effect of initial concentration (50–100 mg/L), the quantity of biochar (0.5–1 g), and the form of silver Ag+ and Ag NPs on biochar removal capacity. Thomas and Yoon-Nelson models were applied to simulate different column parameters, such as breakthrough time, saturation time, the volume of treated effluent, and percentage of removal. These simulated results could assist in the scale-up of the process for an actual industrial operation. Experimental data showed good agreement with both Thomas and Yoon-Nelson models, where the simulated values were closely matched with the experimental values. Biochar was collected after the adsorption and characterised to confirm the morphology, crystal structure, and ionic state of silver. The saturated column was regenerated by 0.05 M HNO3 as eluent and used at least 3 times with 15% capacity loss compared to initial performance, which demonstrated the viability and effectiveness of the biochar adsorption process.

Arsenic and Antimony Removal from Water by Zirconium-Coated Water Treatment Plant Sludge

In this study, the reuse potential of drinking water treatment sludge as an adsorbent was investigated for the removal of arsenic and antimony. A sludge-derived adsorbent, zirconium oxide-coated sludge, was produced by using thermal treatment and zirconium oxide coating processes, and characterization of the adsorbent was investigated. The results showed that zirconium oxide-coated sludge was mainly amorphous and had a high surface area (170 m2g-1). Batch adsorption tests were performed to specify the optimum conditions for arsenic removal. The study revealed that the removal of As (T) was best achieved at pH 3. The initial arsenic concentration descended from 50 μgL-1 to the 0.25 μgL-1 at contact time, 180 min, with the adsorbent dose of 1 gL-1. The isotherm data fitted fine to the Freundlich isotherm model, and adsorption capacity was found to be 7.38 mgg-1. The pseudo-second order model fitted well with the experimental data (R2≥ 0.999). Column performance for arsenic and antimony removal in a fixed bed under continuous flow conditions was also studied. The adsorption process behavior was described successfully by Thomas and Yoon–Nelson models, indicating that the models were suitable for a zirconium oxide-coated sludge fix-bed column design.

Sand coated with graphene oxide-PVA matrix for aqueous Pb2+ adsorption: Insights from optimization and modeling of batch and continuous flow studies

In the present study, a composite of graphene oxide-polyvinyl alcohol coated sand (GO-PVA@sand) was prepared and examined for adsorption of aqueous Lead ion (Pb2+) in batch and fixed-bed columns. The characterization of GO-PVA@sand revealed that GO-sheets were randomly immobilized into the PVA-matrix and formed a stable complex surrounding sands particles. And hence, preventing leaching of GO from the GO-PVA@sand and avoiding agglomeration of GO-PVA@sand inside the column that leads to no column chocking. The adsorption of Pb2+ onto GO-PVA@sand was endothermic in nature, attained equilibrium in ≤ 45 min, followed the pseudo-second-order kinetics, and the Langmuir adsorption isotherm with the maximum adsorption capacity of 8.25 mg/g. Moreover, the fixed-bed column study revealed that the adsorption capacity (qeq) decreased from 7.4 to 7.0 mg/g by increasing inlet flow rate from 5 to 15 mL/min because of drop in the contact time between Pb2+ and GO-PVA@sand. In contrast, the qeq increased from 7.2 to 7.6 mg/g, with an increase of bed-height from 2 to 6 cm, due to greater contact time and surface exposure. Besides increasing inlet concentration from 20 to 40 mg/L, the qeq increased from 7.2 to 8.0 mg/g, apparently because of the presence of a higher mass driving force. To understand the potential for process scale-up, breakthrough modeling was performed and found that the Thomas and Yoon-Nelson model best described the adsorption behavior. The post-adsorption characterization of GO-PVA@sand showed Pb2+ adsorbed through ion-exchange, cation-π, electrostatic interaction, and hydrogen bonding. The regeneration and reuse potential of the GO-PVA@sand up-to five adsorption-desorption cycles, signify its relevance in low-cost continuous water treatment.

Oleic Acid-Tailored Geopolymer Microspheres with Tunable Porous Structure for Enhanced Removal from Tetracycline in Saline Water

Tetracycline (TC) in the water body poses a huge threat to the ecological environment. There is a great challenge to develop highly efficient, green, low-cost and reusable adsorbents for TC removal from saline water. Herein, metakaolin-based geopolymer microspheres (MM) modified by oleic acid were proposed for the enhanced adsorption of TC from saline water. Experimental and characterization results showed that the introduction of oleic acid into the MM effectively adjusted the specific surface area, pore volume and zeta potential of the MM, thus accelerating the adsorption rate and enhancing the TC adsorption capacity of the MM. The adsorption process fitted well to the pseudo-second-order kinetic and Langmuir isothermal models. The Langmuir adsorption capacity of TC by the optimal MM, namely MM3 (0.3%, oleic acid), reached 645.7 mg·g−1 at 298 K, which was higher than many reported adsorbents. The adsorption process was endothermic and spontaneous. The MM3 had good adsorption performance of TC from saline water and regeneration performance. Moreover, the breakthrough curves of the MM3 in a column system were correlative with the Thomas and Yoon–Nelson models. The adsorption mechanisms of TC by the MM3 involved Van der Waals forces, electrostatic interactions, hydrogen–bonding interactions, and ion exchange.

Buckwheat hull-derived biochar immobilized in alginate beads for the adsorptive removal of cobalt from aqueous solutions

Buckwheat hull-derived biochar (BHBC) beads were synthesized by immobilizing biochar powder with alginate. Due to their cation-exchange ability, abundant functional groups, microporous structure, and large surface area, BHBC beads were successfully applied for the removal of cobalt from aqueous solution. The adsorption behavior followed pseudo-second-order kinetics and the Langmuir isotherm model showed a better fit to adsorption data than the Freundlich or Temkin isotherm models. The maximum adsorption capacity of BHBC beads was 24.0 mg/g at pH 5, 35 °C, and an initial cobalt concentration of 1.0 g/L, which was higher than those of previously reported natural resource-based adsorbents. In a fixed-bed column study, the effects of operating parameters such as flow rate, bed height, and bed diameter were investigated. Both the Thomas and Yoon–Nelson models were applied to the experimental data to predict the breakthrough curves using nonlinear regression. Overall, BHBC beads can be used as an efficient adsorbent for removal of radioactive cobalt from aqueous solution.

Removal of p-Nitrophenol from simulated sewage using steel slag: Capability and mechanism

The steel slag was investigated for the removal of p-nitrophenol (4-NP) from simulated sewage by batch adsorption and fixed-bed column absorption experiments. The results showed that the maximum adsorption capacity was 109.66 mg/g at 298 K, pH of 7, initial concentration 100 mg/L, and dose 0.8 g/L. The adsorption process fitted the Langmuir isothermal adsorption model and followed pseudo-second-order kinetic models, the activation energy of adsorption (Ea) was 10.78 kJ/mol, which indicated that the adsorption was single-molecule layer physical adsorption. The regeneration efficiency was still maintained at 84.20% after five adsorption-desorption cycles. The column adsorption experiments showed that the adsorption capacity of the Thomas model reached 13.69 mg/g and the semi-penetrating time of the Yoon-Nelson model was 205 min at 298 K. Fe3O4 was identified as the main adsorption site by adsorption energy calculation, XRD and XPS analysis. The FT-IR, Zeta potential, and ionic strength analysis indicated that the adsorption mechanism was hydrogen bonding interaction and electrostatic interaction. This work proved that steel slag could be utilized as a potential adsorbent for phenol-containing wastewater treatment.

Aminopolycarboxylic Acids-Functionalized Chitosan-Based Composite Cryogels as Valuable Heavy Metal Ions Sorbents: Fixed-Bed Column Studies and Theoretical Analysis.

Over the years, a large number of sorption experiments using the aminopolycarboxylic acid (APCA)-functionalized adsorbents were carried out in batch conditions, but prospective research should also be directed towards column studies to check their industrial/commercial feasibility. In this context, sorption studies of five-component heavy metal ion (HMI) solutions containing Zn2+, Pb2+, Cd2+, Ni2+, and Co2+ in equimolar concentrations were assessed in fixed-bed columns using some APCA-functionalized chitosan-clinoptilolite (CS-CPL) cryogel sorbents in comparison to unmodified composite materials. The overall sorption tendency of the APCA-functionalized composite sorbents followed the sequence Co2+ < Zn2+ < Cd2+ ≤ Pb2+ < Ni2+, meaning that Co2+ ions had the lowest affinity for the sorbent’s functional groups, whereas the Ni2+ ions were strongly and preferentially adsorbed. To get more insights into the application of the composite microbeads into continuous flow set-up, the kinetic data were described by Thomas and Yoon–Nelson models. A maximum theoretical HMI sorption capacity of 145.55 mg/g and a 50% breakthrough time of 121.5 min were estimated for the column containing CSEDTA-CPL cryogel sorbents; both values were much higher than those obtained for the column filled with pristine CS-CPL sorbents. In addition, desorption of HMIs from the composite microbeads in dynamic conditions was successfully achieved using 0.1 M HCl aqueous solution. Moreover, a theoretical analysis of APCA structures attached to composite adsorbents and their spatial structures within the complex combinations with transition metals was systematically performed. Starting from the most stable conformer of EDTA, coordinative combinations with HMIs can be obtained with an energy consumption of only 1 kcal/mole, which is enough to shift the spatial structure into a favorable conformation for HMI chelation.

Adams-Bohart, Yoon-Nelson, and Thomas modeling of the fix-bed continuous column adsorption of amoxicillin onto silver nanoparticle-maize leaf composite

This study focused on the use of a fix-bed column in the removal of amoxicillin from an aqueous solution by the application of silver nano-based adsorbents. The silver nanoparticle and nanocomposite were produced by a green synthetic approach. Column adsorption was performed at a flow rate of 5.88 mL/min, bed height of (5.0–7.0 cm), and amoxicillin concentration of 20–40 mg/L. Adsorption data were fitted to Thomas, Adams-Bohart, and Yoon-Nelson models. The color change from light yellow to dark brown showed that silver ions have been reduced to silver atoms. Energy dispersive spectroscopy (EDS) analysis showed the characteristic silver peak of the nano-adsorbents at 3.0 keV containing 57.29% silver in the synthesized silver nanoparticle. Analysis of silver nanoparticles-maize leaf composite revealed its pore distribution to be uneven with an average pore size of 7.44 nm. The data were best fitted to the Thomas model more than Adams-Bohart and Yoon-Nelson’s models. Thomas’s model showed that an increase in concentration and flow rate led to an increase in qo (maximum adsorption capacity) and kTH (Thomas rate constant), However, the increase in bed height led to a decrease in both qo and kTH. The correlation coefficients were in the range 0.6528–0.9797. The results revealed that the silver nanoparticles-maize leaf combo is suitable for the continuous adsorption of amoxicillin in aqueous media with the best performance at a lower concentration, higher bed height, and flow rate.

Selective and efficient separation of biomass hydrolysate levulinic acid and formic acid from aqueous solution

The recovery of levulinic acid (LA) and formic acid (FA) from aqueous solutions and actual biomass hydrolysates by using the stepwise adsorption method was investigated for the first time. The carbon molecular sieve was used as the adsorbent for FA and microporous activated carbon was used as the adsorbent for LA according to the steric hindrance effect of the pore channels and the difference in molecular diameter of FA and LA. The adsorption data of LA and FA onto their respective adsorbents were measured and numerically analyzed by adopting batch adsorption experiment and fixed-bed column methods. In the study of static adsorption equilibrium experiment, the Langmuir equation fitted the data of LA adsorption on activated carbon, while the Freundlich equation fitted well the adsorption data of FA adsorption on carbon molecular sieve. In the kinetic study, the LA adsorption on activated carbon and FA adsorption on carbon molecular sieve confirmed the PSO model. Moreover, the effect of various conditions on fixed-bed column adsorption progress was investigated, which indicated that the adsorption property improved with feed flow rate, column length, temperature decreasing and initial concentration increasing. The Yoon-Nelson model was adopted to predict and analyze the whole process of adsorption breakthrough and consistent well with the experimental data. The separation of LA and FA was realized by continuous fractional adsorption.

INVESTIGATION OF MECHANISAM OF METAL ION ADSORPTION FROM AQUEOUS SOLUTIONS USING PROSOPIS JULYFLORA ROOTS: BATCH AND FIXED BED COLUMN STUDIES

&lt;p&gt;Adsorption of heavy metal ions (Cr, Pb &amp;amp; Zn) using prosopis julyflora roots has been investigated by batch adsorption and fixed bed column process. The various properties of adsorbent were analysed and the FT-IR spectra &amp;amp; SEM studies of prosopis julyflora powder, before and after adsorption of metal ions also examined. From the batch adsorption study, maximum amount of metal ion adsorption was found to be 87.12% for Cr (VI), 92.28% for Pb (II) and 95.62% for Zn (II) metal ions. The Freundlich isotherm model fitted well than the Langmuir adsorption isotherm with high regression values. From the column study, optimum bed height of 5 cm, flow rate of 5 mL/min and metal ion concentration of 100 mg/L was obtained by breakthrough analysis. The fixed bed column study followed Thomas &amp;amp; Yoon-Nelson model plots with good correlations and maximum desorption rate was achieved by adding 0.3M of concentrated H2SO4.&lt;/p&gt;&#x0D;

Preparation of magnetic adsorbent-photocatalyst composites for dye removal by synergistic effect of adsorption and photocatalysis

Biochar-based magnetic photocatalyst (ZnFe-BC) is successfully prepared by one-pot method using microwave heating for rhodamine B (RB) and malachite green (MG) removal from wastewater. The characterization results show that ZnFe-BC has the properties of adsorption, photocatalytic degradation and magnetism, contributing to RB and MG removal. The adsorption capabilities of RB and MG are 334.89 mg/g and 576.73 mg/g calculated by Langmuir model, respectively. The adsorption data are fitted to the Thomas and Yoon-Nelson model to predict the breakthrough curves of RB and MG in the fixed-bed adsorption. The photodegradation removals of RB and MG are 99.05% and 98.08%, respectively. A good photodegradation performance of ZnFe-BC is attributed to the high adsorption capability of ZnFe-BC, and synergy between biochar and ZnO on ZnFe-BC. The photocatalytic degradation mechanism is investigated by the density functional theory calculation. ZnFe-BC can be quickly recycled from RB or MG solution under extra magnetic field after use. ZnFe-BC still has good removal in binary RB and MG mixture solution. The present work demonstrates a successful example of waste poplar saw dust converting into the sustainable biochar-based magnetic photocatalyst for RB and MG removal from wastewater

Selective adsorption of Ba2+ using chemically modified alginate beads with enhanced Ba2+ affinity and its application to 131Cs production

The 131Cs radioisotope with a short half-life time and high average radiation energy can treat the cancer effectively in prostate brachytherapy. The typical 131Cs production processes have a separation step of the cesium from 131Ba to obtain a high specific radioactivity. Herein, we suggested a novel 131Cs separation method based on the Ba2+ adsorption of alginate beads. It is necessary to reduce the affinity of alginate beads to cesium ions for a high production yield. The carboxyl group of the alginate beads was replaced by a sulfonate group to reduce the cesium affinity while reinforcing their affinity to barium ions. The modified beads exhibited superior Ba2+ adsorption performances to native beads. In the fixed-bed column tests, the saturation time and adsorption capacity could be estimated with the Yoon-Nelson model in various injection flow rates and initial concentrations. In terms of the Cs elution, the modified alginate showed better performance (i.e., an elution over 88%) than the native alginate (i.e., an elution below 10%), indicating that the functional group modification was effective in reducing the affinity to cesium ions. Therefore, the separation of cesium from the barium using the modified alginate is expected to be an additional option to produce 131Cs.

Modeling of linear alkyl benzene sulphonic acid removal from aqueous solution with fixed bed adsorption column: Thomas and Yoon–Nelson methods

AbstractBACKGROUNDIn Turkey, which is one of the world's top walnut producers, the volume of waste shell has increased in recent years as a result of escalating consumption. Globally, including in Turkey, cleaning products are the leading pollutants entering the aquatic environment. This study aimed to address both issues, by investigating the removal of Linear Alkyl Benzene Sulphonic Acid synthetic solution through a fixed‐bed adsorption column system embedded with the composite of a polyaniline‐supported activated walnut shell.RESULTSLinear Alkyl Benzene Sulfonic Acid removal efficiency was evaluated in terms of detergent and chemical oxygen demand (COD) parameters. Column performance increased with low flow rate, increased bed height and high inlet concentration. Optimum conditions were determined as 7.5 cm bed height, 10 mL min−1 flow rate, and 30 mg L−1 inlet solution concentration. Thomas and Yoon–Nelson models were applied to experimental data to estimate the column adsorption behavior. The Yoon–Nelson model (R2 &gt; 0.9) seemed fit to explain the adsorption column behavior. To understand the reuse capacity of the adsorbent a regeneration study was carried out, showing that the maximum adsorption capacity of the adsorbent (qtotal) decreased from 216 mg g−1 before regeneration to 6.4 mg g−1 after the third regeneration cycle.CONCLUSIONThis adsorbent has a high potential for detergent and COD adsorption from anionic aqueous solutions, and would be a good alternative for a pretreatment step. © 2022 Society of Chemical Industry (SCI).

Portable SA/CMC entrapped bimetallic magnetic fly ash zeolite spheres for heavy metals contaminated industrial effluents treatment via batch and column studies

Heavy metals are perceived as a significant environmental concern because of their toxic effect, bioaccumulation, and persistence. In this work, a novel sodium alginate (SA) and carboxymethylcellulose (CMC) entrapped with fly ash derived zeolite stabilized nano zero-valent iron and nickel (ZFN) (SA/CMC-ZFN), followed by crosslinking with CaCl2, is synthesized and applied for remediation of Cu(II) and Cr(VI) from industrial effluent. The characterization of the adsorbent and its surface mechanism for removing metals were investigated using advanced instrumental techniques, including XRD, FT-IR, SEM–EDX, BET, and XPS. The outcomes from the batch experiments indicated that monolayer adsorption on homogeneous surfaces (Langmuir isotherm model) was the rate-limiting step in both heavy metals sorption processes. The maximum adsorption capacity of as-prepared SA/CMC-ZFN was 63.29 and 10.15 mg/g for Cu(II) and Cr(VI), respectively. Owing to the fact that the wastewater released from industries are large and continuous, a continuous column is installed for simultaneous removal of heavy metal ions from real industrial wastewater. The outcomes revealed the potential of SA/CMC-ZFN as an efficient adsorbent. The experimental breakthrough curves fitted well with the theoretical values of Thomas and Yoon-Nelson models. Overall, the results indicated that SA/CMC-ZFN is a viable, efficient, and cost-effective water treatment both interms of batch and column processes.

Remarkable adsorption for hazardous organic and inorganic contaminants by multifunctional amorphous core–shell structures of metal–organic framework-alginate composites

• CA-MIL-53-AC were synthesized via a one-pot method for removing DDT, As(V), and F. • Composite beads showed superior textural properties and abundant reactive functional groups. • CA-MIL-53-AC had higher adsorptive capacity than the other beads for DDT, As(V), and F. • Plausible mechanisms were identified to provide insights in the contaminants removal. Novel metal–organic framework-alginate composite beads (CA-MIL-53-AC) were synthesized using sodium alginate (gelling agent) and calcium chloride (complexing agent) via a one-pot and dropping method to selectively remove the dichlorodiphenyltrichloroethane (DDT), arsenate (As(V)), and fluoride in an aqueous solution. To evaluate the characteristics of the synthesized composite beads, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared, X-ray photoelectron spectroscopy, thermal gravimetric analysis, zeta potential, and porosimetry techniques were used in this study. The adsorption kinetics showed that DDT, As(V), and fluoride removal could be described by the pseudo-first-order model. Also, the adsorption isotherms indicated that DDT and As(V)/fluoride removal followed the Langmuir and Freundlich models, respectively. Compared with granular AC and pristine CA, CA-AC, and CA-MIL-53, the CA-MIL-53-AC showed superior adsorption performance for all target contaminants (5.29, 4.89, and 3.18 mg/g for DDT, As(V), and fluoride, respectively). The adsorptive behavior for DDT was spontaneous, exothermic, and highly favorable based on thermodynamics calculations. Furthermore, the regenerated composite beads showed high removal capacity for DDT after the third recycle. The continuous DDT adsorption in the fixed-bed column at different flow rates were well fitted using Thomas, Adams–Bohart, and Yoon–Nelson models. The plausible mechanisms for the DDT, As(V), and fluoride removal by CA-MIL-53-AC were identified as hydrophobic and π–π interactions, ion exchange, surface complexation, and hydrogen bonding. These findings provide significant insight to remove DDT, As(V), and fluoride from water for practical applications.

A dual grafted fluorinated hydrocarbon amine weak anion exchange resin polymer for adsorption of perfluorooctanoic acid from water

Perfluorooctanoic acid (PFOA) is a persistent and recalcitrant organic contaminant of exceptional environmental concern, and its removal from water has increasingly attracted global attention due to its wide distribution and strong bioaccumulation. Adsorption is considered an effective technique for PFOA removal and more efficient PFOA sorbents are still of interest. This study developed a dual grafted fluorinated hydrocarbon amine weak anion exchange (WAX) polymeric resin (Sepra-WAX-KelF-PEI) for PFOA removal from water. This polymer was synthesized by a two-step amine grafting reaction procedure involving first the reaction of the Sepra-WAX hydrocarbon polymer with poly(vinylidinefluoride-chlorotrifluoroethylene) (Kel-F 800) and then a second reaction with polyethyleneimine (PEI). Characterization of the synthesized polymers was performed using scanning electron microscopy and elemental analysis (F and Cl) by energy dispersive X-ray spectroscopy. The PFOA adsorption performance evaluations were conducted by packed column flow analyses with on-line detection. The results show the breakthrough of the Sepra-WAX-KelF-PEI synthesized with optimum stoichiometry was two times better than the starting anion exchange polymer Sepra-WAX, and six times better than powdered activated carbon, when using the same column size. The adsorption mechanisms of this novel adsorbent including hydrophobic interaction and electrostatic interaction were also clarified in this study. The adsorption kinetic parameters of the two optimum synthesized sorbents were determined using the Thomas model, the Yoon-Nelson model, and batch isotherm studies, and compared with those found with activated carbon and the starting WAX resin. Good agreement of the batch isotherm and column studies with respect to adsorption capacities trends between all three polymers (Sepra-WAX, Sepra-WAX-KelF, and Sepra-WAX-KelF-PEI) were noted.

Nitrate adsorption onto surface-modified red mud in batch and fixed-bed column systems: equilibrium, kinetic, and thermodynamic studies.

This research aimed to develop a novel composite as a low-cost adsorbent for the removal of nitrate ion from aqueous solutions. The characterization of this composite (composition of red mud with dimethyldioctadecylammonium bromide (DDAB)) was performed by XRF, XRD, FTIR, and BET analyses. The most influential variables on nitrate adsorption, including contact time, solution acidity, adsorbent amount, and temperature were studied. The maximum amount of nitrate adsorbed onto the prepared adsorbent was obtained at pH 5.5 and contact time 30min. The heterogeneous adsorption occurred during the uptake of nitrate. The results of kinetic study revealed that intra-particle diffusion was the major limitation for nitrate adsorption rate. The values of thermodynamic parameters illustrate the non-spontaneous, associative, and exothermic adsorption process. Increasing the temperature enhances the tendency of the process to non-spontaneously. Research on fixed-bed column has been done under different initial nitrate concentrations. The adsorption capacity of nitrate was increased with an increase in the initial concentration of nitrate. The results of column data were successfully explained using the Thomas and Yoon-Nelson models.

Plastic waste as a valuable resource: strategy to remove heavy metals from wastewater in bench scale application.

Single-use plastic waste is gradually considered a potential material for circular economy. Ion exchange resin obtained from polystyrene waste by sulfonating with H2SO4 was used for heavy metal removal from electroplating wastewater. Batch mode experiments of Cu2+, Zn2+, and Cd2+ were carried out to determine effect of pH, initial concentration, equilibrium time, and the isotherm and kinetic parameters; the stability of the resin in continuous operation was then evaluated. Finally, the longevity of the resin after being exhausted was explored. The results indicated that at pH 6, a pseudo-second-order kinetic model was applicable to describe adsorption of studied heavy metals by sulfonated polystyrene with adsorption capacities of 7.48mg Cu2+/g, 7.23mg Zn2+/g, and 6.50mg Cd2+/g, respectively. Moreover, the ion exchange process between sulfonated polystyrene resin and Cu2+, Zn2+, Cd2+ ions followed the Langmuir isotherm adsorption model with R2 higher than 96%. The continuous fixed-bed column in conditions of a sulfonated polystyrene mass of 500g, and a flow rate of 2.2L/h was investigated for an influent solution with known initial concentration of 20mg/L. Thomas and Yoon-Nelson models were tested with regression analysis. When being exhausted, the sulfonated polystyrene was regenerated by NaCl in 10min with ratio 5mL of NaCl 2M per 1g saturated resins. After 4 times regeneration, the heavy metal removal efficiency of sulfonated polystyrene was reduced to 50%. These aforementioned results can figure out that by sulfonating polystyrene waste to synthesize ion exchanging materials, this method is technically efficient and environmentally friendly to achieve sustainability.