Polymeric Ligand Exchanger Research Articles

Adsorptive Properties of Cation Added Hydrous Bismuth Oxide on Nitrate Sorption

Groundwater contamination by non-metallic inorganic contaminants has become a severe problem to the human kind and its healthy survival. Nitrate contamination of drinking water has become a major health threat in many countries of the world including India and this issue needs to be resolved through developing advance technology to scale down the nitrate concentration and to make the water fit for drinking. With the ultimate objective of developing an inorganic and sustainable sorptive media for nitrate abatement from drinking water, hydrous bismuth oxide (HBO) has been synthesized and studied as an adsorbent for aqueous medium in the present work. Hydrous bismuth oxides based adsorbents are found to have nitrate sorptive properties along with their possible application in drinking water treatment. In an attempt of improving the potentials of HBO, incorporation of cations such as copper, iron and two transition metals each of which has vividly been used in the preparation of bi-metallic adsorbents as well as polymeric ligand exchangers. Calcium and Magnesium were included for their wide availability and possible value addition towards the purpose. HBO adsorbent mixed with cations, which has shown highest nitrate sorptive potential was characterized using X-Ray diffraction pattern, Scanning electron microscopy and Fourier Transform Infrared spectroscopy analyses. It was observed that incorporation of these individual cations, the Mg and Ca did not show any improvement whereas the presence of Fe and Cu within the matrix of HBO has shown significant improvement in nitrate sorption potential of HBO and it was inferred that presence of Ca, Mg and Fe appear to be helpful in the formation of polymeric structures. Scherrer crystallite size slightly improved in presence of Mg and Fe.

Simultaneous removal of nitrate/phosphate with bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin.

Given the prevalence of nitrate and phosphate in surface and groundwater, it is important to develop technology for the simultaneous removal of nitrate and phosphate. In this study, we prepared the bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin DOW 3N (D-Fe/Ni and D-Fe/Cu) for removing nitrate and phosphate simultaneously. XPS profiles revealed that Cu has better ability than Ni to increase the stability of Fe nanoparticles and prevent nZVI from oxidation. The results showed that nitrate removal efficiencies by D-Fe/Ni and D-Fe/Cu were 98.7% and 95.5%, respectively and the phosphate removal efficiencies of D-Fe/Cu and D-Fe/Ni were 99.0% and 93.0%, respectively. Besides adsorption and coprecipitation as reported in previous studies, the mechanism of phosphate removal also includes the adsorption of the newly formed polymeric ligand exchanger (PLE). Moreover, in previous studies, the presence of phosphate had significant negative effects on the reduction of nitrate. However, in this study, the removal efficiency of nitrate was less affected with the increasing concentration of phosphate for D-Fe/Cu. This was mainly because D-Fe/Cu had higher adsorption capacity of phosphate due to the newly formed PLE according to the XPS depth profile analysis.

Development of ion exchangers for the removal of health-hazardous perchlorate ions from aqueous systems

In order to investigate diffusion models and adsorption mechanism of polymeric ligand exchangers (PLE) for the removal of perchlorate from tap water Lewatit MonoPlus TP 220-Cu, Lewatit MonoPlus TP 220-CuEDDS, Dowex 4195-Cu and M 4195-CuEDDS were prepared and compared with commercial Lewatit TP 220 and Dowex M 4195. Based on the adsorption experiments, diffusion mechanisms were studied using the intraparticle diffusion, film diffusion, Boyd, Dumwald-Wagner models. The pore diffusion coefficient (Dp), film diffusion coefficient (Df) as well as well-known kinetic models like the pseudo first and the pseudo second order were also applied to fit the experimental data. The adsorption study was carried out at pH equal 7.0 and different contact time. The kinetics of adsorption was based on the pseudo second order model. The adsorption studies show that the adsorption rate controlling step is realized mainly by intraparticle diffusion. The basic surface structural changes before and after the perchlorate sorption on each sorbent were investigated using ATR-FTIR. After sorption the band at 1085 cm−1 appeared which showed efficiency of the sorption process. The adsorbents were also characterized by the nitrogen adsorption/desorption isotherms, thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis. The study proved efficiency of Lewatit MonoPlus TP 220-Cu and Lewatit MonoPlus TP 220-CuEDDS, Dowex 4195-Cu and M 4195-CuEDDS for perchlorate removal from water.

Efficient adsorption, removal and recovery of phosphate and nitrate from water by a novel lanthanum(iii)-Dowex M4195 polymeric ligand exchanger

A novel polymeric ligand exchanger (PLE) can selectively remove phosphate and nitrate from water down to <0.1 ppm.

Arsenic adsorption using Fe(III)-loaded porous amidoximated acrylonitrile/itaconic copolymers

A highly selective polymeric ligand exchanger was developed for the removal of trace As(V) from aqueous solution. This adsorbent was prepared by loading Fe(III) onto porous amidoximated polyacrynitrile (AN)/itaconic acid (IA) copolymers (Fe(III)-AO AN/IA). Negligible ferric ion dissolution was observed from Fe(III)-AO AN/IA in solution of acidic pHs up to 2. As(V) adsorption by Fe(III)-AO AN/IA is a pH-dependent process with maximum capacity of 1.32 mg/g at pH 2–3. The adsorption process was found to be governed by pseudo-second-order kinetics, and could be described by the Freundlich model. Fe(III)-AO AN/IA had higher adsorption selectivity for As(V) than other anions in a simulated groundwater body such as Cl−, SO42−, PO43−, SiO32−. Fixed-bed adsorption indicated that As(V) in simulated groundwater could be effectively captured from 400 μg/L to <10 μg/L within 190 bed volumes (BV). The As(V) adsorbed on Fe(III)-AO AN/IA could be efficiently eluted with 10 BV of 5% NaCl solution (at pH = 9.0).

Preparation and characterization of polymeric ligand exchanger based on chitosan hydrogel for selective removal of phosphate

Polymeric ligand exchangers (PLEs) are typically prepared using commercial chelating resins which are often costly and less “green”. In this work, we prepared a new PLE by immobilizing Cu(II) on a low-cost, natural biopolymer chitosan. It was confirmed that the Cu2+ ions were bonded to chitosan by complexing with the nitrogen and hydroxyl groups in the chitosan polymer chain, leading to a reduction in the size of the hydrogel and intensified density of the biopolymer. The chelating interaction between nitrogen and Cu2+ acts as a crosslinker that improves the physical and chemical stability of the PLE. The pH sorption tests confirmed a pKa of ∼7.0 for the biopolymer. The PLE reverses the affinity sequence of standard anionic resins, and displayed much greater affinity toward strong ligands such as phosphate than sulfate due to concurrent electrostatic and Lewis acid-base interactions between immobilized Cu2+ ions and phosphate regardless of solution pH. The maximum phosphate uptake was estimated to be 70mgg−1 and 35mgg−1 in single and binary-component systems, respectively. Fixed-bed column tests revealed that the PLE may be used for selective removal of phosphate of strong ligand characteristics over sulfate.

Removal of As(V) from aqueous solutions using Cu(II)-loaded 4-vinyl pyridine grafted polymeric ligand exchanger

Removal of As(V) from aqueous solutions using Cu(II)-loaded 4-vinyl pyridine grafted polymeric ligand exchanger

Preparation and characterization of Fe(III)-loaded iminodiacetic acid modified GMA grafted nonwoven fabric adsorbent for anion adsorption

An Fe(III)-loaded chelating fabric with iminodiacetic acid (IDA) functional groups was prepared by radiation induced graft polymerization of an epoxy group containing monomer, glycidyl methacrylate, onto a nonwoven fabric made of polypropylene coated by polyethylene (PE/PP) and subsequent Fe(III) loading. Grafting conditions were optimized, and GMA grafted polymer was modified with iminodiacetic acid in isopropyl alcohol/water at 80°C. In order to prepare the polymeric ligand exchanger (PLE) for the removal of phosphate, IDA fabrics were loaded with Fe(III) ions. Fe(III) loading capacity of IDA fabric was determined to be 2.83mmol Fe(III)/g of polymer. For removal of phosphate anion, adsorption experiments were performed in batch mode at different pH (2–9) and phosphate concentrations. It was found that phosphate adsorption by the Fe(III)-loaded IDA fabric is maximum at pH 2.00. The effect of initial concentration of phosphate on the adsorption behaviour of Fe(III)-loaded IDA nonwoven fabric was determined at low phosphate concentrations (0.5–25ppm) and at high phosphate concentrations (50–1000ppm).

Feasibility study of novel sorbent for chromium sequestration and enhanced immobilization

ABSTRACT The present solid phase sorption studied for the treatment of water containing mainly chromium by “In-house” synthesized specific amphoteric chelator have been evaluated w.r.t. basic parameters like concentration, time, and elution etc. High uptake values of the metal ions proves its selectivity, whereas negligible elution or high immobilization factor (0.97) confirm further decontamination of run-off water during natural calamities. This polymeric ligand exchanger displayed minimum and maximum level sorption of 41.2% and 99.6% at the feed concentration of 50 and 500 ppm respectively.

Preparation, characterization and application of a copper (II)-bound polymeric ligand exchanger for selective removal of arsenate from water

A copper (II)-bound polymeric ligand exchanger named WH-425-Cu was prepared by loading Cu 2+ onto poly (4-vinylpyridine) resin. The performance of WH-425-Cu as the ligand exchanger to remove arsenate [As (V)] from aqueous solution was also investigated by using static equilibrium and dynamic adsorption experiments. Results of static experiments indicated that WH-425-Cu had higher adsorption selectivity for As (V) than other ubiquitous anions in nature water body such as SO 4 2−, Cl −, SiO 3 2−, and PO 4 3−. The optimal pH for adsorption of As (V) on WH-425-Cu was in the range of 6.0–8.0. The As (V) adsorbed on WH-425-Cu could be easily eluted with 7BV of 6% NaCl solution (at pH = 9.0) with elution efficiency above 99%. The prepared WH-425-Cu could be used as a highly selective and reusable ligand exchanger for selective removal of As (V) from water.

Removal of phosphate by using copper‐loaded poly(N‐vinylimidazole) hydrogels as polymeric ligand exchanger

AbstractPolymeric ligand exchangers (PLE) are generally composed of a crosslinked hosting resin that can firmly hold a transition metal ion which can act as terminal functional groups. In this study, poly(N‐vinylimidazole) (PVIm) hydrogels were synthesized by free radical polymerization/crosslinking of N‐vinylimidazole in aqueous solution. Swelling behavior of PVIm hydrogels was investigated and the gel with minimum amount of crosslinking agent, hence showing maximum swelling was selected as the optimum gel system for further studies. To prepare the corresponding PLE for the removal of phosphate, PVIm hydrogels were loaded with Cu(II) ions. Copper loading capacity of PLE was determined to be 5 mmol of Cu(II)/g of dry gel. For removal of phosphate, adsorption experiments were performed in batch mode at different pH (3–9) and phosphate concentrations. It was found that phosphate adsorption capacity did not change significantly within this pH range. The effect of initial concentration of phosphate on the adsorption behavior of PLE was determined for 10 different phosphate concentrations (0.1–1000 mg/L) at pH 7. NaCl solution was used for regeneration of phosphate adsorbed Cu(II) loaded PVIm hydrogels with 100% regeneration efficiency. The new PLE showed high affinity for phosphate; the highest uptake was found to be 218 mg/g dry PLE from 1000 mg/L phosphate solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and characterization of a new class of polymeric ligand exchangers for selective removal of arsenate from drinking water

Six new chelating resins were prepared by functionalizing three commercially available XAD resins of various matrix properties, including XAD1180, XAD16 and XAD7HP. Two types of pyridinyl functional groups were loaded on these sorbents, one with two nitrogen donor atoms (2N) per functional group and the other with three N-donor (3N) atoms per functional group. Consequently, six polymeric ligand exchangers (PLE’s) were prepared by immobilizing Cu(II) ions onto these chelating resins, where Cu(II) serves as the surface central metal. The highest Cu(II) loading was determined to be 44 mg/g. Unlike standard strong base anion (SBA) exchangers, the PLE’s displayed greater affinity toward arsenate than for sulfate. The binary arsenate–sulfate separation factor ( α As/S) ranged from 5.1 to 10. Bench-scale column breakthrough tests confirmed the greater selectivity for arsenate over other common anions (sulfate, bicarbonate and chloride). The breakthrough of arsenate occurred last at ∼920 BV for XAD1180-3N–Cu. From batch kinetic tests, the PLE’s intraparticle diffusivity ( D) was determined to be more than one order of magnitude greater than standard SBA resins. The PLE’s can be effectively regenerated using 8% NaCl at pH 10. The arsenate capacity can be completely recovered using the brine. Despite the high surface area, the PLE’s sorption capacity was limited by the hyper-crosslinkage and the degree of methylation/amination of the template XAD resins.

Removal of phosphate using copper-loaded polymeric ligand exchanger prepared by radiation grafting of polypropylene/polyethylene (PP/PE) nonwoven fabric

A novel polymeric ligand exchanger (PLE) was prepared for the removal of phosphate ions from water. 2,2′-dipyridylamine (DPA), a bidentate ligand forming compound with high coordination capacity with a variety of metal ions was bound to glycidyl methacrylate (GMA) grafted polypropylene/polyethylene (PP/PE) nonwoven fabric synthesized by radiation-induced grafting technique. DPA attachment on epoxy ring of GMA units was tested in different solvents, i.e. methanol, ethanol, dioxane and dimethylsulfoxide (DMSO). The highest amount of modification was achieved in dioxane. In order to prepare the corresponding PLE for the removal of phosphate, DPA-immobilized fabric was loaded with Cu(II) ions. Phosphate adsorption experiments were performed in batch mode at different pH (5–9) and phosphate concentrations. The fabric was found to be effective for the removal of phosphate ions. At every stage of preparation and use, the nonwoven fabric was characterized by thermal (i.e. DSC and TGA) and spectroscopic (FTIR) methods. Competitive adsorption experiments were also carried out using two solutions with different concentration levels at pH 7 to see the effect of competing ions. Phosphate adsorption was found to be effective and selective from solutions having trace amounts of competitive anions. It is expected that the novel PLE synthesized can be used for the removal of phosphate ions in low concentrations over a large range of pH.

Selective Removal of Toxic Metals like Copper and Arsenic from Drinking Water Using Phenol‐Formaldehyde Type Chelating Resins

The concentration of different toxic metals has increased beyond environmentally and ecologically permissible levels due to the increase in industrial activity. More than 100 million people of Bangladesh and West Bengal in India are affected by drinking ground water contaminated with arsenic and some parts of India is also affected by poisoning effect of copper, cadmium and fluoride. Different methods have been evolved to reduce the arsenic concentration in drinking water to a maximum permissible level of 10 μg/L where as various methods are also available to separate copper from drinking water. Of the proven methods available today, removal of arsenic by polymeric ion exchangers has been most effective. While chelating ion exchange resins having specific chelating groups attached to a polymer have found extensive use in sorption and pre concentration of Cu2+ ions. Both the methods are coupled here to separate and preconcentrate toxic metal cation Cu2+ and metal anion arsenate(AsO4–) at the same time. We have prepared a series of low‐cost polymeric resins, which are very efficient in removing copper ion from drinking water and after coordinating with copper ion they act as polymeric ligand exchanger, which are efficiently removing arsenate from drinking water. For this purpose Schiff bases were prepared by condensing o‐phenylenediamine with o‐, m‐, and p‐hydroxybenzaldehydes. Condensing these phenolic Schiff bases with formaldehyde afforded the chelating resins in high yields. These resins are loaded with Cu2+, Ni2+ 2+, and Fe3+ ions. The resins and the polychelates are highly insoluble in water. In powdered form the metal ion‐loaded resins are found to very efficiently remove arsenate ion from water at neutral pH. Resins loaded with optimum amount of Cu2+ ion is more effective in removing arsenate ions compared to those with Fe3+ ion, apparently because Cu2+ is a stronger Lewis acid than Fe3+. Various parameters influencing the removal of the arsenate ion from drinking water to a concentration level below 20 μg/L are studied.

A Comparison of Metal-Loaded DOW3N Ion Exchangers for Removal of Perchlorate from Water

In this work, an alternative class of perchlorate selective ion exchangers (known as polymeric ligand exchangers, PLEs) were prepared by loading six transition metals (Cu(II), Co(II), Zn(II), Ni(II), Fe(II), and Fe(III)) onto a commercially available chelating resin Dowex M4195 (DOW3N). The resultant PLEs (DOW3N-Me, where Me = one of the metals) were tested with respect to their perchlorate selectivity, capacity, kinetics, and regeneration efficiency through a series of batch and column experiments. Within this group of PLEs, DOW3N-Cu(II) showed the highest perchlorate capacity; all four PLEs had similar perchlorate sorption kinetics; and DOW3N-Fe(III) demonstrated better regeneration potential.

Sorption and Desorption of Perchlorate with Various Classes of Ion Exchangers: A Comparative Study

This study compares representative standard strong-base anion (SBA) and weak-base anion (WBA) exchangers, a bifunctional resin (A-530E), a class of polymeric ligand exchangers (PLEs), and an ion-exchange fiber (IXF) with respect to perchlorate sorption capacity, kinetics, and regenerability. While A-530E offered the greatest perchlorate capacity and selectivity, practically acceptable capacity was also observed for styrenic SBA and WBA resins, a PLE, and IXF. In contrast, polyacrylic resins offered much lower perchlorate capacity. The greater capacity of styrenic resins is attributed to enhanced ion-pairing and Lewis acid−base interaction due to the hydrophobic nature of polystyrene matrices and lower hydration energy of perchlorate. Conversely, regeneration of polyacrylic resins was much more efficient, and A-530E was least regenerable. IXF offered comparable perchlorate capacity to that of styrenic resins yet unparalleled kinetics (with a sorption equilibrium time of <1.5 h), and much greater regeneration efficiency, and WBA resins were much more regenerable than SBA resins.

Selective sorption and preconcentration of tartaric acid using a copper(II)-bound polymeric ligand exchanger

Abstract The current study reports a potential process to selectively separate and preconcentrate tartaric acid from its simulated industrial effluent. It was achieved by sorption onto a tailored polymeric ligand exchanger. The polymeric ligand exchanger is essentially a copper(II)-bound specialty chelating polymer (denoted D-Cu). Effect of solution pH and competing sulfate on tartaric acid sorption onto D-Cu was also included in the study. Compared to a weakly basic anion exchanger D-301, D-Cu exhibits more favorable sorption of tartaric acid from aqueous media coexisting with Na 2 SO 4 at a high level. The exhausted D-Cu was amenable to an entire regeneration by the diluted NaCl solution. Results of column sorption tests further demonstrated the feasibility of D-Cu for selective separation and preconcentration of tartaric acid from the simulated wastewater for its further recovery.

Beneficial phosphate recovery from reverse osmosis (RO) concentrate of an integrated membrane system using polymeric ligand exchanger (PLE)

Phosphorus (P) discharge to surface water is a major environmental problem. Wastewater treatment is targeted towards removal of this nutrient to prevent degradation of surface water. Integrated membrane systems (IMS) are increasingly being considered for wastewater reclamation, and provide excellent removal of P compounds. However, reverse osmosis (RO), which forms an integral part of these IMSs, concentrates most dissolved substances including P-species such as phosphates in the RO waste stream. In this study, removal of phosphate from this stream using polymeric ligand exchange (PLE) resins was investigated. Further, the possibility of phosphate recovery through struvite (MgNH 4PO 4·6H 2O) precipitation was tested. Struvite has been promoted as a slow release fertilizer in recent years. This study demonstrates that PLEs can be successfully used to remove phosphate from RO-concentrate, and to recover more than 85% of the adsorbed phosphorus from the exhausted media and precipitated as a beneficial product (struvite). The approach, presented in this study, suggests advantages of providing economic benefit from a waste product (RO) while avoiding phosphorus discharge to the environment.

Removal of Perchlorate from Contaminated Water Using a Regenerable Polymeric Ligand Exchanger

A polymeric ligand exchanger (PLE), DOW 3 N‐Cu, has been investigated for perchlorate (ClO4 −) removal from contaminated water. Batch kinetic tests revealed that the perchlorate sorption equilibrium for DOW 3 N‐Cu can be reached within 20 hours and perchlorate removal by DOW 3 N‐Cu follows standard ion exchange stoichiometry. Fixed‐bed column runs showed that 12,388 bed volumes of perchlorate‐free water can be obtained when DOW 3 N‐Cu was used to treat a simulated contaminated water with an influent perchlorate concentration of 200 µg/L. It was found that the regeneration of spent DOW 3 N‐Cu is pH dependent. It was shown that addition of ethanol and a surfactant Tween 80 to a 4% NaCl/2% NaOH regenerant solution increased the regeneration efficiency of spent DOW 3 N‐Cu by 11 and 5 percent, respectively. Nearly 90% of perchlorate capacity of saturated DOW 3 N‐Cu was recovered using 35 bed volumes of a regenerant containing 4% (w/w) NaCl, 2% NaOH, 5% Tween 80, and 5% ethanol.

Selective removal of arsenate from drinking water using a polymeric ligand exchanger

The new maximum contaminant level (MCL) of 10 μg/L for arsenic in the US drinking water will take effect on January 22, 2006. The compliance cost is estimated to be ∼$ 600 million per year using current treatment technologies. This research aims to develop an innovative ion exchange process that may help water utilities comply with the new MCL in a more cost-effective manner. A polymeric ligand exchanger (PLE) was prepared by loading Cu 2+ to a commercially available chelating ion exchange resin. Results from batch and column experiments indicated that the PLE offered unusually high selectivity for arsenate over other ubiquitous anions such as sulfate, bicarbonate and chloride. The average binary arsenate/sulfate separation factor for the PLE was determined to be 12, which were over two orders of magnitude greater than that (0.1–0.2) for commercial strong-base anion (SBA) exchangers. Because of the enhanced arsenate selectivity, the PLE was able to treat ∼10 times more bed volumes (BVs) of water than commonly used SBA resins. The PLE can operate optimally in the neutral pH range (6.0–8.0). The exhausted PLE can be regenerated highly efficiently. More than 95% arsenate capacity can be recovered using ∼22 BVs of 4% (w/w) NaCl at pH 9.1, and the regenerated PLE can be reused without any capacity drop. Upon treatment using FeCl 3, the spent brine was recovered and reused for regeneration, which may cut down the regenerant need and reduces the volume of process waste residuals. The PLE can be used as a highly selective and reusable sorbent for removal of arsenate from drinking water.