Ion Exchange Adsorption Research Articles

Spectroscopic insight into the pH-dependent interactions between atmospheric heavy metals (Cu and Zn) and water-soluble organic compounds in PM2.5

Taking Cu and Zn as examples, the pH-dependent interactions between atmospheric heavy metals (AHMs) and water-soluble organic compounds (WSOCs) in PM2.5 were analyzed by a combination of UV–vis absorption, Fourier transform infrared (FTIR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). We found metal-H ion exchange, complexation and electrostatic adsorption might occur between AHMs and WSOCs, and were generally enhanced with the increase of pH. Furthermore, these interactions were strengthened with the stepwise addition of [Cu2+] (from 0 to 500 μmol·L−1), but had a relatively slight change with the stepwise addition of [Zn2+] (from 0 to 500 μmol·L−1) generally. This indicated that the above interactions depended on the types and the concentrations of AHMs. Carboxyl, hydroxyl, carbonyl and aromatic structures of WSOCs were the major binding sites with AHMs. Humic acid-like substances were the dominant components of WSOCs binding with AHMs. The ratios of the apparent fluorescence quantum yields of the low and the high conjugation fractions of WSOCs (QExL/H) declined by more than 28% as adding [Cu2+], indicating the formers had more strong complexing capacity with AHMs. AHMs might significantly impact the light absorption capacity and the wavelength dependence of WSOCs. The humification index (HIXem) declined more than 15% as adding [Cu2+] at pH 5.6 and 7.5, indicating AHMs might weaken the oxidation capacity of WSOCs. These results implied the interactions between AHMs and WSOCs might play a profound role in atmospheric environment, human health, and global climate change.

High-surface-area interconnected macroporous nanofibrous cellulose microspheres: a versatile platform for large capacity and high-throughput protein separation

With the rapid development of biopharmaceutical industry, conventional chromatographic media cannot meet the increasing demand for high-quality proteins. Here, high-surface-area interconnected macroporous nanofibrous cellulose microspheres (NCMs) are fabricated by combining emulsion technique and template method. The macroporous nanofibrous structure of NCMs contributes to the fast transfer of liquid and improves processing efficiency, and the high specific surface area endows NCMs with numerous active sites for the immobilization of adsorption ligands. Benefiting from the advantages of microstructure, NCMs are highly suitable as a versatile adsorbent platform for highly effective protein separation. As a proof of concept, we prepare three NCM-based protein adsorbents with different adsorption mechanisms including anion ion-exchange adsorbent, Cu2+-chelating affinity adsorbent, and hydrophobic interaction adsorbent, which all exhibit high adsorption capacity and fast adsorption kinetic, outstanding recyclability and structure stability for targeted protein, much superior to commercial and most of previously reported same type of adsorbents. We expect that the NCM would provide a promising candidate for the design and construction of high-performance protein adsorbent.

Cobalt-loaded resin can effectively remove arsenic in wastewater

Most current arsenic(As(V)) removal technologies are designed for low-As(V) wastewater. Consequently, the efficacy of treating high-As(V) wastewater with these technologies is generally unsatisfactory. Here, the Cobalt(Co)-loaded resin removal of As(V) in wastewater and its mechanism are discussed. Rapid adsorption and a slow equilibrium were achieved during the reaction, and the As(V) removal efficiency exceeded 99% within 0–30 min with an initial As(V) concentration of 100 mg/L. The adsorption capacity of the Co-loaded resin was as high as 116 mg/g. The Co-loaded resin has the best As(V) removal efficiency when the pH = 8. The adsorption kinetics of the Co-loaded resin material revealed the adsorption behavior. FTIR and XPS studies showed that As(V) was removed on the Co-loaded resin material, and As(V) was primarily removal through ion exchange adsorption and chemical co-precipitation. Thus, this Co-loaded resin material provides a simple and effective means to remove As(V) from high-As(V) wastewater.

Chitosan coated - porous low expansion vermiculite for efficient removal of cesium from radioactive wastewater

Radioactive elements have very important applications in practical life and work. The long-lived 137 Cs has a half-life of 30.2 years, it is easily absorbed by the human body. At present, the treatment methods of 137 Cs are mainly adsorption, ion exchange, co-precipitation and membrane separation technology. Among them, the adsorption method is widely used because of its low cost and easy availability, and with the continuous upgrading and improvement of the removal methods, the removal cost is also rising, so it is important to develop inexpensive and high removal rate adsorbent materials. Based on this, porous adsorbents made of pre‑sodiumed low expansion vermiculite modified by urea porogenesis and polyglutamic acid covalent grafting followed by chitosan coating had been used to remove Cs + . The proposed adsorbent was successfully applied for radioactive Cs removal to be used as the potential candidate in Fukushima nuclear wastewater treatment. It showed that the porous expanded vermiculite modified with low swelling, with urea as porogen and polyglutamic acid added to increase the negative charge vacancies on the expanded vermiculite surface, could greatly improve the chemisorption capacity of Cs + after chitosan coating. The maximum removal rate for radioactive 137 Cs + was 97.91%, and 89.89% of 137 Cs + could be effectively removed in 0.5 h. Even in the presence of competing ions such as K + , the adsorbent material still has a good adsorption effect. The maximum desorption rate of 98.43% was achieved after elution by CaCl 2 . • Pre-treated vermiculite was covalently grafted and chitosan coated to prepare new adsorbents. • Adsorption equilibrium process consistent with Langmuir adsorption isotherm and pseudo-second-order kinetics • Removal of Cs + and 137 Cs + by synergistic action of ion exchange, ligand complexation and electrostatic adsorption • The adsorbent can be reused 5 times after CaCl 2 elution.

Lithium Recovery from Water Resources by Ion Exchange and Sorption Method

Demand to lithium rising swiftly as increasing due to its rapidly increasing dosages diverse applications such as rechargeable batteries, light aircraft alloys, and nuclear fusion. Lithium demand is expected to triple by 2025 driven by battery applications, specifically electric vehicles. To ensure the growing consumption of lithium, it is necessary to increase the production of lithium from different resources. Natural lithium resources mainly associate within granite pegmatite type deposit (spodumene and petalite ores), salt lake brines, seawater, and geothermal water. Among them, the reserves of lithium resources in salt lake brine, seawater, and geothermal water are in 70–80% of the total, which are excellent raw materials for lithium extraction. Compared to the minerals, the extraction of lithium from water resources is promising because this aqueous lithium recovery is more abundant, more environmentally friendly, and cost-effective. There are many ways to recover lithium from water resources. Among existing methods, the adsorption method is more promising on the way of manufacture. Therefore, the important progress on ion-exchange adsorption methods for lithium recovery from water resources searched ways, were summarized in detail, and the new trends in the future were also carried out.

Lithium Recovery from Water Resources by Ion Exchange and Sorption Method

Demand to lithium rising swiftly as increasing due to its rapidly increasing dosages diverse applications such as rechargeable batteries, light aircraft alloys, and nuclear fusion. Lithium demand is expected to triple by 2025 driven by battery applications, specifically electric vehicles. To ensure the growing consumption of lithium, it is necessary to increase the production of lithium from different resources. Natural lithium resources mainly associate within granite pegmatite type deposit (spodumene and petalite ores), salt lake brines, seawater, and geothermal water. Among them, the reserves of lithium resources in salt lake brine, seawater, and geothermal water are in 70–80% of the total, which are excellent raw materials for lithium extraction. Compared to the minerals, the extraction of lithium from water resources is promising because this aqueous lithium recovery is more abundant, more environmentally friendly, and cost-effective. There are many ways to recover lithium from water resources. Among existing methods, the adsorption method is more promising on the way of manufacture. Therefore, the important progress on ion-exchange adsorption methods for lithium recovery from water resources searched ways, were summarized in detail, and the new trends in the future were also carried out.

Adsorption of mandelic acid enantiomers on chiral stationary phase with grafted antibiotic eremomycin: The effect of the eluent pH

The adsorption of mandelic acid enantiomers on the Nautilus-E chiral stationary phase with eremomycin as a grafted antibiotic, as affected by value of the water-ethanol eluent under conditions of an overloaded column, was studied. Adsorption equilibrium under experimental conditions, when mandelic acid dissociates both completely and then very weakly, was studied. The adsorption isotherms of S- and R-mandelic acid were plotted by the Glueckauf method and inverse method using bi-Langmuir model, as well as the tri-Langmuir model assuming independent adsorption on three types of adsorption centers, with two of them being high-energy enantioselective (ion-exchange and molecular adsorption) and the third – the low-energy nonselective types of sites. This model takes into account the ionization of mandelic acid in the eluent and a change in the value in the mass transfer zone caused by its ionization. The saturated capacity and binding energy of all the types of adsorption sites depend on of the eluent. Nonselective interactions contribute to the adsorption of mandelic acid mainly. To determine the adsorption isotherms of mandelic acid enantiomers on Nautilus-E CSP in the absence of its dissociation and distortion of the elution profiles, the Glueckauf method and the bi-Langmuir model were identified as an acceptable choice.

Mass transfer process and separation mechanism of four 5′-ribonucleotides on a strong acid cation exchange resin

5′-ribonucleotides including adenosine 5′-monophosphate (AMP), cytidine 5′-monophsphate (CMP), guanosine 5′-monophosphate (GMP) and uridine 5′-monophosphate (UMP) have been widely used in the food and pharmaceutical industries. This work focused on the assessment of mass transfer process and separation mechanism of four 5′-ribonucleotides and counter-ion Na+ on the strong cation exchange resin NH-1. The intraparticle diffusion was determined as the rate-limiting step for the mass transfer of AMP, CMP, GMP, and Na+ on the resin NH-1 through the Boyd model. Meanwhile, a homogeneous surface diffusion model (HSDM) combing ion exchange and physical adsorption was proposed and tested against adsorption kinetic data in the batch adsorption systems. The fixed-bed film-surface diffusion model based on the HSDM was then developed and successfully predicted the concentration profiles of 5′-ribonucleotides and the change of pH at the outlet of the fixed-bed in the dynamic adsorption and separation process. Finally, the separation mechanism of 5′-ribonucleotides was presented combining model prediction and experimental results. The separation of UMP, GMP and CMP were mainly based on their differences in isoelectric points, while that of AMP and CMP were lied with the discrepancy of their physical adsorption binding capacity with the resin NH-1.

Modeling of the fractal-like adsorption systems based on the diffusion limited aggregation model

The modeling of the fractal-like adsorption systems, such as the sludge-, algae-, and nanoparticle aggregation-pollutants systems, is of vital significance to understand the mechanisms involved and to connect the mechanisms with the isotherms. But it has not been studied yet. In this paper, a three-dimensional DLA (diffusion limited aggregation) model was modified and used to investigate the fractal-like adsorption systems which were dominated by the physical, chemical, ion exchange and multi-mechanisms. The connection between the adsorption isotherms and the adsorption mechanisms was established. The results showed that the shape and filling degree of the modified DLA model was improved. The adsorption capacity of the fractal-like adsorption system increases with the increase of the fractional dimension of the DLA model. The chemical adsorption capacity is directly proportional to the adsorption active sites. In the ion exchange system, the structure of the DLA model did not change before and after adsorption. The BET, Sips, and ion exchange isotherms could adequately represent the physical, chemical, and ion exchange adsorption. For the multi-system, the adsorption isotherm was C-shaped with the fractal dimensions of the DLA model of 2.28 and 2.42. When the fractal dimensions increase, the isotherm was S-shaped and linear.

Efficacy of Woodchip Biochar and Brown Coal Waste as Stable Sorbents for Abatement of Bioavailable Cadmium, Lead and Zinc in Soil

Organic sorbents alter physicochemical soil properties and mitigate heavy metal (HM) bioavailability. However, some sorbents are labile and, therefore, introduce the risk of HM release into soil after mineralisation. Before field application, new stable organic sorbents such as woodchip biochar (BIO) and brown coal waste (BCW) need to be tested and compared with standard organic amendments like farmyard manure (FYM). An incubated pot experiment was conducted to investigate the efficacy of FYM, BIO and BCW (added to soil in pots at 5 and 10% w/w) to alter soil physicochemical properties and mitigate bioavailability of Cd, Pb and Zn spiked in treatments at different doses (in mg kg−1); 0 (not spiked), 1 (1 Cd, 70 Pb, 100 Zn) and 2 (3 Cd, 500 Pb, 700 Zn), and incubated for 9 weeks. At the end of the experiment, the EDTA-extractable HM fractions, pH, cation exchange capacity (CEC) and specific surface area (SSA, to check trends) were determined in all treated soils. Results showed that FYM, BCW and BIO generally improved all soil properties (except reduced pH from BCW and apparent SSA reduction from FYM) and accounted for respective maximum abatements of Cd (50.2, 69.9 and 25.5%), Pb (34.2, 64.3 and 17.4%) and Zn (14.9, 17.7 and 11.8%) bioavailability in soil. FYM and BCW were more effective at 10% w/w especially in the low contaminated soil, whereas the highest efficacy for BIO was at 5% w/w and in the high contaminated soil. The efficacies of sorption by the organic sorbents varied for different HMs and were in the orders: BCW > FYM > BIO for Cd, FYM > BCW > BIO for Pb and BIO > BCW > FYM for Zn. Soil pH and CEC were strongly correlated with HM bioavailability in all treatments and implied that immobilisation of HMs occurred via complex formation, ion exchange and pH-dependent specific adsorption. All three sorbents were beneficial as soil amendments, and in terms of HM mitigation, BCW had the highest efficacy, followed by FYM and then BIO. Considering the documented high soil stability of BCW and BIO, these results are promising for further trialling at field scale.

Synthesis, Characterization, and Properties of Sulfonated Chitosan for Protein Adsorption

Chitosan sulfate was prepared and characterized as a new chromatography media for protein separation. The degree of sulfonation of chitosan could be well controlled and impacted under conditions in the synthesis process. The prepared chitosan sulfate shows improved binding capacity with proteins. Sulfonated chitosan shows improved ion-exchange adsorption properties with proteins, which could have good potential in protein purification.

The performance of activated carbon/NiFe2O4 magnetic composite to retain heavy metal ions from aqueous solution

A novel magnetic activated carbon composite (AC/NiF) was synthesized by a precipitation method and applied in retention of Cu(II), and Zn(II) ions from aqueous solutions. The impact of different sorption parameters such as: equilibration time, solution pH value, competing cations and ionic strength on the amount sorbed of Cu(II), and Zn(II) was clarified. Results illustrated that the magnetic composite had retention ability towards both metal ions significantly higher than that of activated carbon (AC). The magnetic composite exhibited an affinity to adsorb Cu(II) higher than Zn(II) ions. The maximum sorption capacities (Qmax) of the applied magnetic composite (AC/NiF) towards Cu(II) and Zn(II) were 105.8 and 75.1 mg·g−1, respectively. Retention of Cu(II) and Zn(II) was proposed to be achieved though an ion exchange and surface adsorption in neutral conditions, while precipitation was believed to be the relevant mechanism in their removal from basic solutions. The kinetic studies showed that sorption process followed the kinetics of pseudo-second-order reactions with rate constant of 3 × 10−3 and 2 × 10−3 min−1 for sorption of Cu(II) and Zn(II) onto AC/NiF composite. Removal of Cu(II) slightly decreased with increasing the ionic strength of aqueous solution, using NaCl as a background electrolyte. In contrast, presence of Mn(II), Mg(II) and Co(II) in reaction solutions highly depressed the sorption of Cu(II) and Zn(II) with a competing efficiency followed the order: Mg(II) > Mn(II) > Co(II).The magnetic composite was rapidly recovered from aqueous solution by an external magnetic field, and effectively regenerated using 0.1 mol·L−1 HCl and 0.1 mol·L−1 FeCl3as eluents. Sorption of Cu(II) and Zn(II) onto the surface of AC/NiF composite occurred via a spontaneous reaction. And thermodynamically favorable process had ΔHo values of 30.9 kJ·mol−1 and 19.7 kJ·mol−1, respectively. The results confirm that the magnetic composite can be viewed as a promising novel composite opens new opportunities for the attainment of required adsorption and operative magnetic separation.

Ether-Functionalized Sulfonium Ionic Liquid and Its Binary Mixtures with Acetonitrile as Electrolyte for Electrochemical Double Layer Capacitors: A Molecular Dynamics Study.

Ether-functionalized sulfonium ionic liquids have been investigated as promising electrolytes in electrochemical storage energy devices due to their wide electrochemical window, high ionic conductivity, and low viscosity. In spite of that, the viscosity of neat ionic liquids is still high for supercapacitor applications. Here, we have used atomistic molecular dynamics simulations to describe transport properties, structure, and supercapacitor performance of (2-methoxyethyl)ethylmethylsulfonium bis(trifluoromethanesulfonyl)imide [S12G1][NTf2] and its mixtures with acetonitrile (ACN). The viscosity and ionic conductivity of the neat ionic liquid are in quite good agreement with the experimental results in a wide range of temperatures. The addition of ACN decreases viscosity and, consequently, increases ionic conductivity and diffusion coefficients. Typical alternating layers of ions close to the electrodes surfaces are observed in supercapacitors built with [S12G1][NTf2] when a high voltage is applied, ΔΨ = 3.0 V. Sharp layers of the solvent adsorbed on the surface of electrodes are observed in the mixtures containing ACN. The charge accumulated on the electrodes is barely affected by the amount of ACN, which implies the similar performance in terms of capacitance. However, the charging times follow the viscosities of the electrolytes; that is, the electrolytes with high content of ACN have higher power performance. At low voltage, the rearrangements of ions close to electrodes responsible for the charge accumulation are very low in neat [S12G1][NTf2]. The sharp layer of ACN makes this rearrangement easier, but it acts as a barrier to ion exchange at higher voltages, which increases the charging time. Charging of the supercapacitors is dependent on ion exchange and counterion adsorption at ΔΨ = 3.0 V.

Improved immobilization of lipase from Thermomyces lanuginosus on a new chitosan-based heterofunctional support: Mixed ion exchange plus hydrophobic interactions

In this study, a new mixed heterofunctional support (Chit–GA–Gly) has been prepared by sequential activation of chitosan hydrogel (Chit) with glutaraldehyde (GA) and further functionalization with glycine (Gly). The immobilization of the lipase from Thermomyces lanuginosus (TLL) on this support was compared with that on GA-activated Chit hydrogel (Chit–GA). The supports have been characterized by FT–IR, zeta potential and TG analyses. A similar maximum lipase loading of 53–55 mg per gram of support has been obtained for both supports. Both biocatalysts retained ≈40% of their initial activity after 48 h of incubation at 50 °C in heptane, toluene or iso-octane. The immobilization of TLL on Chit–GA proceeded via preferential covalent attachment (95%) and a combined ion exchange (cationic and anionic) and hydrophobic adsorption was observed using Chit–GA–Gly. TLL immobilized on Chit–GA–Gly was ≈4-times more active than when immobilized on Chit–GA in both olive oil emulsion hydrolysis and alkyl palmitate synthesis via esterification. Isoamyl palmitate synthesis in iso-octane at 50 °C using this new biocatalyst gave a maximum acid conversion of 85% after 90 min of reaction. After nine consecutive esterification batches, the biocatalyst retained around 40% of its initial activity.

RETRACTED ARTICLE: Adsorption kinetics and thermodynamics of Ni (II) by Pisha sandstone

The red Pisha sandstone was taken as absorbents to investigate the effects of the solution pH, the adsorption time and temperature adsorption onto Ni (II) absorption by the Pisha sandstone, and used dynamics and thermodynamic absorption models, coupled with microcalorimetry and infrared spectroscopic (FTIR) analysis, and scanning electron microscope-energy dispersive spectrometer (SEM-EDS); it aimed to determine the mechanism of thermodynamics and kinetics for Pisha sandstone absorbing Ni (II). The results indicated that the adsorption was performed at 293 K, pH 7, and the equilibrium was reached at 30 min, and the adsorption capacity of Ni (II) was 23.688 mg/g; the adsorption process of Ni (II) onto Pisha sandstone could be described with the Lagrangian pseudo-second-order kinetic model, the Freundlich model, and Dubinin-Radushkevich (D-R) model which all could well simulate the isothermal properties, indicating that the adsorption process was mainly monolayer with heterogeneous surface. According to the microthermal process and thermodynamic analysis, the thermodynamic parameters of Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were less than zero, showing that the adsorption of Ni (II) onto Pisha sandstone was exothermic, spontaneous, and entropy increasing. The absorptive models, FTIR analysis, and SEM-EDS demonstrated that the Pisha sandstones absorbing Ni (II) were mainly ion exchange and chemical adsorption meanwhile chemical precipitation little partly worked in the processes.

Synthesis of a starch-based sulfonic ion exchange resin and adsorption of dyestuffs to the resin

A starch-based ion exchange resin (SIR) was synthesized by copolymerizing raw starch with sodium methallyl sulfonate and styrene. The structural and surface properties of the SIR were characterized by 13C nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, gel permeation chromatography, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis, and laser particle size analysis. The SIR was physicochemically and thermally stable and resistant to acids, bases, and enzymes. In static adsorption tests, the SIR had decolorization ratios (DRs) for mixed dyestuffs in wastewater of up to 84.04%, which was higher than the DR for a synthetic ion exchange resin (001 × 7, DR 77.14%). In dynamic adsorption tests, the SIR bed had a DR of 99.85% and a wastewater handling capacity 25 times the column volume. After three adsorption–regeneration cycles, the DR of the resin bed had decreased by <7.5%. The properties of the SIR, particularly the adaptability of the SIR to continuous column adsorption, make the SIR suitable for removing dyestuffs from industrial wastewater and a potential substitute for traditional sorbents such as activated carbon and synthetic resins.

Optimization of l-arginine purification from Corynebacterium crenatum fermentation broth.

l-Arginine has many special physiological and biochemical functions, with wide applications in the food and pharmaceutical industry. Few studies on the purification of l-arginine from fermentation broth have been conducted; however, none of them were systematic enough for industrial scale-up. Therefore, it is necessary to develop a highly efficient and systematic process for the purification of l-arginine from fermentation broth. In this study, we screened out a cation exchange resin, D155, having high exchange capacity, high selectivity, and easy elution capacity, and analyzed its adsorption isotherm, thermodynamics, and kinetics using different models. Further, the process parameters of fixed-bed ion exchange adsorption and elution were optimized, and the penetration curve during the operation was modeled. Based on the fixed-bed ion-exchange parameters, a 30-column continuous ion-exchange system was designed, and the flow velocity in each zone was optimized. Finally, to obtain a high purity of l-arginine, the purification tests were conducted using anion exchange resin 711, and an l-arginine yield of 99.1% and purity of 98.5% was obtained. This effective and economical method also provides a promising strategy for separation of other amino acids from the fermentation broth, which is of great significance to the l-arginine fermentation industry.

Antibiotic removal by activated biochar: performance, isotherm, and kinetic studies

Biomass waste (Chinese traditional medicine residues) is one of the most promising sources of biochar. Here, the present study illustrated the activated biochar (BCA) was prepared using the herb residue (Astragalus membranaceus) via sodium carbonate (Na2CO3) activation for the removal of Cefradine (CF) in wastewater. The adsorbents were characterized by scanning electron microscopy, N2 adsorption-desorption analysis, Fourier transform infrared spectrum, X-ray diffraction, X-ray photoelectron spectroscopy and zeta potential analysis. The effects of initial pH value, BCA dosage, initial CF concentration and coexisting ion for CF removal were investigated. BCA showed much higher absorption capacity for CF (qm =64.76 mg/g) than the pristine biochar (BC). The uptake capacity of BCA and BC for CF was found to be pH-dependent. The analysis of the kinetic and isotherm studies indicated that strong chemical-sorption interactions occurred on the surface of BCA. The removal mechanisms of CF onto BCA would include π-π EDA interaction, hydrogen bonding, ion exchange and electrostatic adsorption. In addition, the fixed bed experiments demonstrated that BCA could be a promising and highly effective adsorbent to treat large volume of CF-contaminated wastewater.

Hybrid nitrate selective resin (NSR-NanoZr) for simultaneous selective removal of nitrate and phosphate (or fluoride) from impaired water sources

Reverse osmosis (RO) has been increasingly applied in municipal wastewater reuse facilities. Nitrate (N) and phosphate (P) -laden reject streams from RO demand near-complete NP removal before inland brine disposal to avoid serious eutrophication effects. In addition, elevated nitrate and fluoride levels in groundwater is a threat to public drinking water safety. Selective removal of both nitrate and phosphate, or fluoride through a single adsorbent is promising because of its small footprints, minimum sludge production, and potential NP recovery. This study presents a new ion exchange adsorbent, NSR-NanoZr, for simultaneous selective removal of both nitrate and phosphate, or fluoride. NSR-NanoZr is fabricated by doping zirconium oxide nanoparticles (ZrO2-Nano) into a nitrate selective resin (NSR), which tributyl quaternary ammonium functional groups contribute to the nitrate selectivity and Lewis acid-base interactions between ZrO2-Nano and ligands result in the high affinity towards phosphate and fluoride. Lab-scale studies showed that NSR-NanoZr exhibited a completely reversal selectivity and removed both NP selectively from municipal secondary wastewater for multiple cycles. Synergistic application of a weak-acid cation exchanger (WAC) enhanced the phosphate capacity of NSR-NanoZr due to the amphoteric sorption behavior of the ZrO2-Nano. Field-scale studies demonstrated the potential of NSR-NanoZr in removing fluoride together with nitrate.

The interactions and adsorption mechanisms of ternary heavy metals on boron nitride

In this work, the interactions and adsorption mechanisms of Cu2+, Cd2+, and Ni2+ on boron nitride (BN) were tested by the simultaneous removal of metal ions from synthetic wastewater. BN was characterized using XRD, SEM, and FTIR spectroscopy. The adsorption differences between BN and the metal ions were explored through comparative studies in a single and ternary system. In the ternary system, adsorption occurs rapidly in the first 2 min for the metal ions, and the affinity order follows Cu2+>Cd2+>Ni2+. However, adsorption behavior changes due to the interaction between metal ions in the ternary system. Cu2+ showed an antagonistic effect on the adsorption of Cd2+ and Ni2+, while Cd2+ and Ni2+ produced a synergistic effect on Cu2+. In addition, the effect of metal ion concentration on the interaction between ions was studied based on a surface response experiment. An increase in Ni2+ or Cd2+ concentrations plays a synergistic effect on the adsorption of Cu2+, while an antagonistic adsorption for Ni2+ occurred with increasing Cu2+ or Cd2+ concentrations. We also discussed the various adsorption mechanisms as complexation, ion exchange, and electrostatic adsorption based on XPS analysis.