Hybrid Anion Exchange Research Articles

A hybrid anion exchanger with nanoscale zero valent iron for trace hexavalent chromium removal from drinking water

Hexavalent chromium is carcinogenic and can occur in groundwater worldwide. Modifying ion exchange resin with zero valent iron increases treatment efficiency in column experiments.

Validation of a Liquid Chromatography Coupled to Mass Spectrometry Method for Glyphosate and Aminomethylphosphonic Acid in Urine for Human Biomonitoring Using Combined Hybrid Anion-Exchange and Hydrophilic Interaction Liquid Chromatography

Glyphosate-based herbicides are the most widely used pesticides in the world; however, the toxicity of glyphosate (GlyP) toward humans, especially its carcinogenicity, is controversial. The aim of this work was to validate a rapid assay for measuring GlyP and its metabolite aminomethylphosphonic acid (AMPA) in urine for human biomonitoring. The analytes were purified via solid-phase extraction in the presence of isotopically labeled internal standards. An LC-MS/MS assay was developed using a column with a novel hybrid stationary phase combined with anion exchange and hydrophilic interaction liquid chromatography. Detection and quantification were performed using negative electrospray ionization in a hybrid triple quadrupole/linear ion trap mass spectrometer. The retention times for AMPA and GlyP were 1.44 and 7.24 min, respectively. Calibration curves showed a linear dynamic range of up to 40 µg/L, inter- and intra-run precisions <7.5%, and accuracies within 10% of the theoretical concentrations. The limits of quantification were 0.1 µg/L and 0.5 µg/L for GlyP and AMPA, respectively. The matrix effect bias was controlled using internal standards. Successful participation in external quality assurance exercises strengthens the validity of the method. The assay was applied to the measurement of GlyP and AMPA in the urine of 9 urban residents, 26 rural residents, and 12 agricultural workers; while AMPA was mostly not quantifiable, the median GlyP values were 0.1 and 0.34 µg/L in rural residents and workers, respectively. The assay is useful to assess GlyP and AMPA in human urine following different exposure scenarios.

FeOOH and (Fe,Zn)OOH hybrid anion exchange adsorbents for phosphate recovery: A determination of Fe-phases and adsorption–desorption mechanisms

Hybrid anion exchange adsorbents (HAIX) seem promising to prevent eutrophication and recover phosphate (P). HAIX consist of an anion exchange resin (AIX) backbone, promoting anion physisorption (outer-sphere complex), impregnated with iron (hydr)oxide nanoparticles (NPs), for selective P chemisorption (inner-sphere complex). In this work, for the first time, as far as we know, Zn-doped iron (hydr)oxide NPs were embedded in AIX, and the performances compared with conventional HAIX, both commercial and synthesized. Zn-doped HAIX displayed improved P adsorption performances. Mössbauer spectroscopy (MS) revealed the goethite nature of the NPs, against the “amorphous hydrous ferric oxide” claimed in literature. The P adsorption comparisons, made in synthetic solution and real wastewater, underlined the crucial role of the NPs for selective P adsorption, while improving the understanding on the competition between physisorption and chemisorption. In pure P synthetic solutions, especially at high P concentrations, physisorption can “hide” chemisorption. This depends also on the anion form of the AIX, due to their higher affinity for multivalent anions, which affects HAIX adsorption selectivity and P desorption. In fact, a mild alkaline regeneration over three adsorption–desorption cycles revealed a complex interaction between the regenerant OH− and the adsorbed P. OH− molecules are consumed to transform phosphate speciation, causing (stronger) P re-adsorption and preventing desorption. Finally, Mössbauer spectroscopy revealed NPs agglomeration/growth after the three cycles plus final regeneration at pH 14. This study provides further understanding on the P adsorption–desorption mechanism in HAIX, drawing attention on the choice of experimental conditions for reliable performance assessment, and questioning HAIX consistent P removal and efficient P recovery in the long-term.

WITHDRAWN: FeOOH and (Fe,Zn)OOH hybrid anion exchange adsorbents for phosphate recovery: A determination of fe-phases and adsorption–desorption mechanisms

WITHDRAWN: FeOOH and (Fe,Zn)OOH hybrid anion exchange adsorbents for phosphate recovery: A determination of fe-phases and adsorption–desorption mechanisms

Hybrid polymer inclusion membrane as anion exchange membrane for recovering Pd2+ ions in electrogenerative process

A novel non-plasticized nano-porous hybrid inorganic-organic polymer inclusion membrane (PIM) was synthesized, characterized, and evaluated as an anion exchange membrane for application in electrogenerative processes to recover Pd2+ ions. Ionic liquids 1-ethyl-3-me­thyl­imidazolium chloride (EMIM-Cl) and 1-butyl-3-methylimidazolium chloride (BMIM-Cl) were used as the carrier molecules in the polymeric network of PIM to enhance anion exchange process. This hybrid anion exchange membrane also consists of a polymeric matrix of non-plasticized cellulose triacetate modified by incorporating an inorganic material (silane) prepared by the sol-gel route. Different parameters affecting the ion transport performance efficiency, i.e., the composition of the membrane, type of ionic liquid (carrier molecule) and ion–exchange capacity, were investigated and optimized. In the electrogenerative process, the results revealed that the prepared PIM yields better recovery results for recovering Pd2+ ions from its chloride solution compared to the commercial anion exchange membrane Neosepta® AM-01, with a full recovery of 100 mg/L Pd2+ ions in 30 min. This preliminary study shows that the prepared low-cost hybrid anion exchange membrane PIM can act as an inexpensive material suitable for the rapid and efficient recovery of Pd2+ ions from an aqueous solution.

Insight into the molecular interaction of trace As (III) and As(V) onto the hybrid anion exchanger impregnated with Fe/Mn nanoparticles (HA502P-Fe/Mn)

In this study, a hybrid anion exchanger impregnated with Fe/Mn nanoparticles (HA502P-Fe/Mn) was synthesized via two-step mixed metal oxide precipitation using 50:50 % DI: ethanol as solvent. Trace As(III) and As(V) removal efficiency was comprehensively validated in both equilibrium adsorption isotherms and kinetics. The maximum adsorption capacities of HA502P-Fe/Mn toward As(III) and As(V) were 21,590 and 18,930 µg/g, respectively. The kinetics of As(III) removal were best predicted (R2 = 0.986) using a pseudo-second order model (k2 = 0.001 g/µg As(III)·min). Adsorption mechanisms were further characterized using X-ray absorption spectroscopy (XANES and EXAFS), including a comparison with the density functional theory (DFT) data. The XANES results showed complex redox transformation of the adsorbed As(V) on HA502P-Fe/Mn. The EXAFS spectra indicate predominant inner-sphere complex formation of bidentate mononuclear edge-sharing (2E) complexes for Mn-As (bond distance 2.94 Å), and bidentate binuclear corner-sharing (2C) complexes for Fe-As (bond distance 3.34 Å) on HA502P-Fe/Mn surfaces. Based on the DFT simulation, the obtained 3D structures were optimized, and the bond lengths between Fe-As and Mn-As were comparable with the EXAFS. For practical purposes, the fixed-bed column experiments were fully investigated for both As(III) and As(V) removal using NSF standard 53 test water (As(III) 300 ppb, pH 6.5), including the regeneration. The HA502P-Fe/Mn demonstrated 2X treatable bed volumes (4,300 vs 2,000 BVs) more than the commercially available As selective adsorbent. The experiments demonstrated that HA502P-Fe/Mn is a promising novel adsorbent for As(III) removal owing to its relatively high As adsorption capacity and regenerating ability.

A Hydrophilic Strong Anion-Exchange Hybrid Monolith for Capillary Liquid Chromatography

A hydrophilic strong anion-exchange monolithic hybrid column was prepared by in-capillary coating 5-µm bare silica particles with the copolymers of methacryloxyethyltrimethyl ammonium chloride and pentaerythritol triacrylate in the presence of a porogen consisting of water, methanol, and cyclohexanol. The composition of the porogen and the concentration of the monomers were investigated and selected. The resulting column was characterized. The column had an uniform pore structure and could withstand a back pressure up to 3500 psi. Its permeability was comparable to that of packed columns and the swelling-shrinking behaviour negligible. Its hydrophobicity could be suppressed at acetonitrile concentrations above 40% (v/v) and the minimum theoretical plate height was about 10 µm for BrÑ. The column-to-column relative standard deviations (RSDs) were 2.2% and 3.5% (n = 9) and the batch-to-batch RSDs were 2.4% and 5.5% (n = 3) for k and H values, respectively. The column exhibited a remarkable performanceforthe separation of inorganic anions, organic weak acids, phenols, and nucleotides.

Construction of polysulfone anion exchange hybrid membranes by incorporating carbon quantum dots and facilitated transport mechanisms

Low ion conductivity and poor alkali resistance are still the two major obstacles for the applications of anion exchange membranes (AEMs). In this work, the combined strategies of Carbon quantum dots (CQDs) hybrid and cross-linking modification via side-chains designing were employed to prepare organic–inorganic hybrid AEMs. Then, the cross-linked quaternized polysulfone (CQPSf-CQDs) hybrid AEMs by incorporating carbon quantum dots were successfully fabricated. After hybrid and cross-linking, the mechanical properties of CQPSf-CQDs hybrid AEMs were higher than that of the pristine one, reaching 49.4 MPa for the best one. Meanwhile, the existence of CQDs can expand the hydrophilic area in the membrane, which is beneficial to the transport of OH-. The incorporated CQDs interact weakly with cationic groups in the side chains through hydrogen bonds. The simulation results further demonstrated that the introduction of CQDs was beneficial to the construction of hydrophilic and hydrophobic domains, thereby increasing OH- conductivity. In addition, the prepared hybrid membranes own excellent dimensional stabilities and ion transport performances. These preliminary results give us a lot of hopes for further experiments and optimizations for the hybrid AEMs.

Inorganic‐Organic Hybrid Anion Conducting Membranes Based on Ammonium‐Functionalized Polyethylene Pyrrole‐Polyethylene Ketone Copolymer

Back Cover: In article number 2100409 by Voto Di Novo and co-workers, the incorporation of tantalum oxide into trimethylammonium-functionalized polyethylene pyrrole-co-polyethylene ketone is carried out for the preparation of inorganic–organic hybrid anion exchange membranes, which are promising candidates for application in electrochemical energy conversion devices.

Preparation and characterization of organic-inorganic hybrid anion exchange membrane based on crown ether functionalized mesoporous SBA-NH2

In this paper, self-made diformyl-dibenzo-18-crown-6 ether (DDB 18 C 6 ) is in-situ grafted into the pores of mesoporous molecular sieve (SBA-NH 2 ), and then the aforementioned modified molecular sieve (SBA-C) is introduced into the polyvinyl alcohol solution, and then the glutaraldehyde as the crosslinking agent to synthesized the anion exchange membrane under for fuel cell application. During the experiment, a series of anion exchange membranes (P-(SBA x% -C), x is the mass fraction of SBA-NH 2 ) is developed and the pore channels and chemical structures of the aforementioned membrane is verified by FT-IR, SAXD, N 2 adsorption-desorption, 1 H NMR and XPS. Moreover, the performance of the membrane synthesized in this paper is also investigated and the results revealed that the unique membrane internal structure can improve the OH − transportation efficiency. Furthermore, the ionic conductivity of P-(SBA 10% -C) membrane is the highest (0.107S·cm −1 ) and the power density is the highest (354.8 mW cm −2 ) at 80 °C. By immersing P-(SBA 10% -C) membrane in 6 mol L −1 KOH solution for 168 h, the conductivity at 80 °C only decreased by 2%, proving that P-(SBA 10% -C) has a higher conductivity, good single cell performance and alkali stability. • A new kind of mesoporous molecular sieve with ordered pores grafted with crown ether was prepared. • A new type of anion exchange membrane with ordered mesoporous channels grafted with crown ether was prepared. • Using crown ether to complex K + to improve the conductivity of anion exchange membranes. • Prepared membrane showed excellent OH − conductivity and alkaline stability.

Inorganic‐Organic Hybrid Anion Conducting Membranes Based on Ammonium‐Functionalized Polyethylene Pyrrole‐Polyethylene Ketone Copolymer

AbstractNew inorganic‐organic hybrid anion exchange membranes are produced after incorporation of tantalum oxide into trimethylammonium‐functionalized polyethylene pyrrole‐co‐polyethylene ketone (functionalized polyketone, FPK), obtained by the chemical modification of a polyketone polymer. The influence of tantalum oxide fillers on the properties of the synthesized membranes is investigated. The interaction between inorganic fillers and the polymer chains is studied using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR‐FTIR). The thermal analysis of the FPK membranes reveals they are thermally stable at up to 250°C. However, the incorporation of the inorganic fillers reduces the thermal stability. Modulated Differential Scanning Calorimetry (MDSC) results indicate that the inclusion of inorganic fillers leads to an increase in crystallinity. This study reports that the properties of the bulk polymer can be tuned by controlling the degree of functionalization and content of inorganic fillers, as confirmed by Near Ambient Pressure X‐Ray Photoelectron Spectroscopy (NAP‐XPS) studies. Finally, Broadband Electrical Spectroscopy (BES) studies demonstrate that the hybrid membranes are characterized by several polarization phenomena contributing to the overall ion conductivity of the material, which at RT is of 1.46 and 1.61 mS cm−1 for the FPK cast membrane and the hybrid membrane with 5.0 wt.% of Ta2O5 filler, respectively.

New Insight into the Molecular Interaction of Trace as (Iii) and As(V) Onto the Hybrid Anion Exchanger Impregnated with Fe/Mn Nanoparticles (Ha502p-Fe/Mn)

New Insight into the Molecular Interaction of Trace as (Iii) and As(V) Onto the Hybrid Anion Exchanger Impregnated with Fe/Mn Nanoparticles (Ha502p-Fe/Mn)

Modifying the resin type of hybrid anion exchange nanotechnology (HAIX-Nano) to improve its regeneration and phosphate recovery efficiency

In order to avoid eutrophication of freshwater systems, regulations all around the world have become increasingly stringent toward the maximum phosphate concentration allowed in wastewater discharges. Traditional phosphate removal methods such as chemical precipitation and enhanced biological phosphorus removal struggle to lower phosphate levels to the new requirements. Hybrid anion exchange nanotechnology (HAIX-Nano) is composed of a selective adsorption material able to remove phosphate down to levels close to zero. Moreover, HAIX-Nano is not affected by intermittent flow and does not produce sludge making it an interesting alternative. The regeneration process of HAIX-Nano typically requires a chemical solution with a high concentration of sodium hydroxide (NaOH) and sodium chloride (NaCl) (2–5% w/w of each). To lower the environmental impact and the operational cost of the technology, this study aims to enhance the HAIX-Nano regeneration efficiency. Therefore, the backbone of HAIX-Nano, which is normally a strong base anionic (SBA) resin, was changed for a weak base anionic (WBA) resin. The resulting material (WBA-2) exhibited a higher adsorption capacity than the traditional version of HAIX-Nano (SBA-1) under the tested conditions, while also showing a much higher regeneration efficiency. For a desorption solution of only 0.4% NaOH and no NaCl, WBA-2 showed an average regeneration efficiency of 78 ± 1% compared to SBA-1 with 24 ± 1%.

Highly hydroxide-conducting hybrid anion exchange membrane with functional COF-enhanced ion nanochannels

Anion exchange membranes with potentially high conductivity and stability are urgently demanded in alkaline anion exchange membrane fuel cells (AEMFCs). However, the design and preparation of novel hydroxide-conducting material remain grand challenges. Herein, we demonstrate a significantly enhanced hydroxide conduction hybrid membrane with multi-ion nanochannels assembled by embedding two-dimensional covalent organic framework (COF) sheets into one-dimensional comb-shaped poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) chains. Hydrophilic imidazole-based ionic liquids (im-IL) in-situ polymerize within the ordered pores of COF PI-2, forming long-range continuous ion channels. Then the poly ionic liquid-loaded covalent organic frameworks (im@PI-2) as a novel filler is embedded into imPPO to construct hybrid membranes with multi-ion nanochannels. A remarkable hydroxide conductivity of 147 mS/cm (80 °C and 100% RH) and a maximum power density of 140 mW/cm2 are readily achieved for the hybrid membrane with 5 wt% im@PI-2 content. Particularly, the chemical stability, thermal stability, mechanical properties, and swelling resistance of the hybrid membrane are dramatically promoted by the introduction of im@PI-2. Meanwhile, the transfer of hydroxide in hybrid AEM is investigated by molecular dynamics simulations, which clarify the significant role of PI-2 one-dimensional channels in elevating hydroxide transport.

Regeneration and modelling of a phosphorous removal and recovery hybrid ion exchange resin after long term operation with municipal wastewater

Adsorption represents one of the most promising process for phosphorous (P) removal and recovery from municipal wastewater, but questions about its long-term stability remain. The goals of this work were (i) to assess changes in morphology and adsorption performances of hybrid anion exchanger (HAIX) LayneRT after 2.5 years of operation in a 10 m3 d−1 demonstration plant fed with secondary-treated municipal wastewater, (ii) to optimize the LayneRT regeneration procedure, and (iii) to evaluate the suitability of the ion exchange model to describe P adsorption on LayneRT. LayneRT is composed of hydrated ferric nanoparticles dispersed in a strong base anion exchange resin. Batch and continuous flow adsorption/desorption tests were conducted with the resin used for 2.5 years, regenerated with two alternative solutions: NaOH, reactivating mainly the iron nanoparticles active sites, and NaOH + NaCl, also regenerating the active sites of the ion exchange media. The physicochemical characterization by Scanning Electron Microscope indicated that regeneration by NaOH significantly reduced the deterioration of the resin surface, even after 59 adsorption/desorption cycles. Lab-scale continuous flow tests showed that the resin regenerated with either solution featured P adsorption performances very close to that of the virgin resin. The isotherm tests showed that P adsorption by LayneRT was effectively simulated with the ion exchange model. This study confirms that LayneRT is a durable, resistant and promising media for P recovery from wastewater.

Demonstration of ion exchange technology for phosphorus removal and recovery from municipal wastewater

• HAIX removed 90% of the PO 4 -P for 430 BV at 5 min EBCT. • HAIX removed 26% of the COD but it resulted in progressive fouling of the resin. • A regeneration with NaCl 5% is needed to maintain high adsorption capacity. • NaOH 2% can be used as regenerant solution for eight consecutive times. • Around 95% of the P was recovered from saturated NaOH as hydroxyapatite. Orthophosphate (PO 4 -P) removal and recovery from municipal wastewater were investigated in a 10 m 3 /day hybrid anion exchanger (HAIX) demonstration plant. To date, HAIX resins have been investigated for PO 4 -P removal at laboratory scale with promising results but there is a need to investigate the application of the technology at larger scale, over extended operation whilst establishing an efficient regenerant management solution. The HAIX removed an average of 6 mg PO 4 -P /L to > 0.3 mg PO 4 -P/L, within 430 bed volumes, with a capacity of 4.1 mg PO 4 -P/g resin. To manage the regenerant (NaOH 2%) efficiently, this was reused up to 8 times, reaching 785 mg PO 4 -P/L, but the adsorption capacity was compromised, and it decreased to 1.5 mg PO 4 -P/g resin. By adding calcium hydroxide to the saturated NaOH, 95% of the PO 4 -P was recovered as hydroxyapatite, and at the same time the regeneration effectiveness was re-established, as < 0.3 mg PO 4 -P/L was reached again in the effluent. The treated NaOH was reused as regenerant solution, ensuring high effluent quality of < 0.2 mg PO 4 -P/L. This study confirmed the capability of HAIX technology to remove and recover PO 4 -P from wastewater offering a solution which ensures both a high effluent quality and a circular economy approach.

Hybrid anion exchange membranes with adjustable ion transport channels designed by compounding SEBS and homo‐polystyrene

AbstractHybrid anion exchange membranes (AEMs) were prepared via chemically functionalizing and crosslinking poly(styrene‐b‐[ethylene‐co‐butylene]‐b‐styrene) (SEBS) copolymers and low molecular weight homo‐polystyrene (hPS). Via sequential chloromethylation, crosslinking, quaternization, and alkalization, a series of hPS/SEBS AEMs were obtained with varying content of hPS. Systematic structural, morphological, mechanical, absorption, and transport measurements reveal that these properties depend on the total PS content in the membranes. Particularly, increasing total PS content causes (a) PS domains in the AEMs transition the cylindrical morphology to lamella‐like morphology with comparable correlation length; (b) Young's modulus, water uptake, swelling ratio, ionic exchange capacity and ionic conductivity of the AEMs, and Tg of PS phase increase. In addition, the alkaline stability of the hPS/SEBS AEMs is also improved by addition of hPS. These findings suggest that the proposed method can develop high performance SEBS AEMs that are suitable for fuel cell applications.

The role of intraparticle diffusion path length during electro-assisted regeneration of ion exchange resins: Implications for selective adsorbent design and reverse osmosis pretreatment

Inorganic membrane scaling is a major cause of process failure for reverse osmosis (RO). Pretreatment using selective ion exchangers can reduce membrane scaling by removing scale-forming ions such as calcium (Ca2+) and phosphate (P). Ca- and P-selective ion exchangers also enable calcium phosphate recovery via precipitation from spent regenerants enriched with both ions. However, conventional regeneration approaches require substantial chemical and energy inputs. In this study, we designed a RO pretreatment process using electro-assisted regeneration of a column train containing a hybrid anion exchanger (HAIX) and a weak acid cation exchanger (WAC) to selectively remove > 90% Ca2+ and P from synthetic secondary effluent. HAIX and WAC were regenerated using pH 11 catholyte and pH 3 anolyte produced via electrochemical water splitting. HAIX contains ferric oxide nanoparticles (FeOnp) in a parent strong base anion exchanger (SBA). By comparing P regeneration efficiency of HAIX and SBA, we identified that FeOnp dopants reduced intraparticle diffusivity by 85% from SBA to HAIX. However, HAIX exhibited faster column regeneration kinetics than SBA, potentially due to the shortened intraparticle diffusion path length caused by the surface-distributed P in saturated HAIX, which overcompensated for low intraparticle diffusivity. Regenerability enhancement caused by the reduced intraparticle diffusion path length was also confirmed by comparing WAC with shallow-shell WAC (SSWAC), which has surface-distributed carboxylate functional groups. We anticipate that this study will inform selective adsorbent design by identifying strategies to improve regenerability, facilitate process intensification by replacing chemical inputs with electricity, and enhance resource recovery from wastewater.

Highly hydroxide-conductive anion exchange membrane with PIL@MOF-assisted ion nanochannels

A highly hydroxide-conducting anion exchange membrane with well-organized multi ion channels were fabricated via incorporating poly ionic liquids modified MIL101 (PIL@MIL101) into imidazolated poly (2,6-dimethyl-1,4-phenylene oxide) (ImPPO). 1-Vinyl-3-ethylimidzolium bromine was first immobilized in MIL101 cages via supercritical fluid impregnation method. Afterwards, the rigid-assisted ion nanochannels were constructed by in-situ polymerization of ionic liquids within the long-range ordered pores of MIL101. Meanwhile, PPO was functionalized by 1-ethyl-2-methyimidzolium to prepare comb-shaped ImPPO with enhanced microphase separation structure. Then the PIL@MIL101 was combined with ImPPO to fabricate hybrid anion exchange membrane with well-organized multiple ion channels. The OH− conductivity of the hybrid membrane significantly reached 138mS/cm at 80°C (176% higher than that of pristine membrane). Furthermore, the stability and mechanical properties of the hybrid membranes were remarkably enhanced. The excellent performances render the hybrid membrane a good candidate for the application in anion exchange membrane fuel cells.

Passive Detection of Phosphorus in Agricultural Tile Waters Using Reactive Hybrid Anion Exchange Resins

Tile drainage waters carry considerable loads of phosphorus (P) from agricultural fields to rivers and streams in the Midwestern U.S. An innovative and economical approach to monitor dissolved reactive P (DRP) flux in tile waters is needed to understand the extent of P loss in field-scale. In this study, a passive sampling technique was developed using iron oxide-coated polyacrylic/polystyrene anion exchange resins (hybrid resins) a P sink. Laboratory batch adsorption isotherm and kinetic experiments indicated that the hybrid resins had high P adsorption capacity (7.69–19.84 mg/g) and high kinetic performance. The passive sampling method with field-calibrated hybrid polyacrylic resin and hybrid polystyrene resins (sampling rate: 0.1351 and 0.0763 L/h, respectively) predicted the average DRP concentrations of 0.006–0.020 mg/L, which did not differ significantly (p &gt; 0.05) from the auto-sampling data. A rapid increase in DRP concentration during storm events and subsequent flooding events was also predicted well. In conclusion, a passive detection method using iron oxide coated hybrid resins can be recommended for monitoring seasonally fluctuating DRP flux in agricultural waters as long as the hybrid resins are well-calibrated under specific field conditions (e.g., flow rate and concentration range).