A novel Pb(II)-imprinted IPN for selective preconcentration of lead from water and sediments

A novel adsorbent Pb(II)-imprinted interpenetrating polymer network (IPN) of epoxy resin-triethylenetetramine and lead methacrylate-acrylamide-1,4-butanedioldiacrylate (BDDA) was synthesized by the metal ionic imprinted polymer (MIIP) technique. The IPN was prepared by in situ sequential polymerization, and the coordination interaction of Pb(II) and functional groups of the IPN adsorbent was discussed using FT-IR spectra. The characters of the IPN were investigated by a series of experiments. The experimental results show that trace Pb(II) ions can be quantitatively preconcentrated at pH 4.0 with recoveries >95%. The maximum static adsorption capacity of the ion-imprinted adsorbent was 138.6?mg?g^?1. The imprinted IPN has a higher adsorption capacity and selectivity towards Pb(II). Moreover, the Pb(II)-imprinted IPN shows superior reusability and stability. The precision (R.S.D.) for 11 replicate adsorbent extractions of 20?ng?mL^?1 Pb(II) was 2.9%. The accuracy of the proposed procedure was verified by analysing three standard reference materials. The prepared ion-imprinted IPN adsorbent was applied to three natural samples and also yielded satisfactory results. That is to say, the Pb(II)-imprinted IPN is suitable for environmental Pb(II) ionic selective removal as an SPE adsorbent.     

Ion-imprinted interpenetrating network gels for solid-phase extraction of heavy metal ions

In the present work, ion-imprinted interpenetrating polymer network (IPN) gels were prepared by free radical/cationic hybrid polymerisation of acrylamide (AAm) and 1,4-butanediol vinyl ether (BVE). These gels were respectively used for separation of Cu²⁺, Ni²⁺ and Zn²⁺ ions in natural water samples. Experimental conditions for effective adsorption of metal ions were optimised with respect to different experimental parameters by column procedures in detail. The optimum pH value for the adsorption of Cu²⁺, Ni²⁺ and Zn²⁺ ions on these sorbents was 6.0. Complete elution of the adsorbed metal ions from the sorbent was carried out using 1.0 mol/L of HCl solution. The optimum sample flow rate and eluent flow rate were, respectively, 1.0 and 0.3 mL/min. Common coexisting ions did not interfere with the separation and determination of the target ions. The accuracy of the proposed method was validated by analysis of the standard reference material (GBW 08301, river sediment). The measured contents of metal ions in the reference material were in good agreement with the certified values. The presented method was successfully applied for the determination of Cu²⁺, Ni²⁺ and Zn²⁺ ions in three different water samples (well water, seawater and waste water).     

Copper(II) complexes of entwined 2,9-di(o-substituted phenyl)-1,10-phenanthroline type ligands and intramolecular quenching in copper(I) complexes

Cu¹¹ complexes of 1,10-phenanthroline, disubstituted at the 2 and 9 positions or monosubstituted at the 2 position by phenyl moieties possessingortho substituents, were prepared and investigated by spectroscopic and electrochemical methods. The electronic spectral d-d band position varies from 14 500 to 13 200 cm⁻¹. E.s.r. g_‖ values are between 2.256 to 2.283 and A_‖ between 164 to 117×10⁻⁴ cm⁻¹. Thebis[2,9-di(o-substituted phenyl)-1,10-phenanthroline]Cu¹¹ complexes undergo reversible one-electron electrochemical reduction (Cu¹¹/Cu¹) in the +0.536 to +0.825 V potential range versus s.c.e., whereas thebis[2-mono(o-substituted phenyl)-1,10-phenanthroline]Cu¹¹ complexes undergo reduction in the +0.360 to +0.405 V range; the redox couple is found to be quasireversible. Emission studies on copper(I) complexes show that onlybis[2,9-di(o-tolyl)-1,10-phen]Copper(I) complex exhibits emission properties. Emission behaviour of other structurally similar compounds is explored. TMC 2555     

Functionalized anodic aluminum oxide (AAO) membranes for affinity protein separation

An ideal affinity membrane should own well uniformities. However, most existing microporous membranes used as affinity matrices generally have wide pore size distribution and some thickness variation. In this paper, chitosan (CS)–anodic aluminum oxide (AAO) composite membrane with excellent uniformities, such as narrow pore size and porosity distribution, as well as uniform membrane thickness, was fabricated, for the first time. Cu²⁺-attached affinity membrane was obtained by immobilizing Cu²⁺ on the CS–AAO membrane. The contents of CS and Cu²⁺ of affinity membranes were ∼49.7 and 27.15 mg/g membrane, respectively. The Cu²⁺-attached affinity membranes were used to recover a model protein, hemoglobin, from hemoglobin–phosphate solution (batch manner) and from the hemolysate (dynamic manner). The protein adsorption indicated that the adsorption capacity of hemoglobin was ∼17.5 mg/g membrane, and the adsorption isotherm fitted the Freundlich model well. Elution of protein showed desorption ratio was up to 91.2% using 0.5 M imidazole aqueous solution as the desorption agent. The adsorption capacities of all the tested affinity membranes did not significantly change during the repeated adsorption–desorption operations. The result of dynamic experiment showed Cu²⁺-attached affinity membranes can well purify the hemoglobin from the red cell lysate.     

Removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions by adsorption onto natural bentonite

In this study, the removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions using the adsorption process onto natural bentonite has been investigated as a function of initial metal concentration, pH and temperature. In order to find out the effect of temperature on adsorption, the experiments were conducted at 20, 50, 75 and 90 °C. For all the metal cations studied, the maximum adsorption was observed at 20 °C. The batch method has been employed using initial metal concentrations in solution ranging from 15 to 70 mg L⁻¹ at pH 3.0, 5.0, 7.0 and 9.0. A flame atomic absorption spectrometer was used for measuring the heavy metal concentrations before and after adsorption. The percentage adsorption and distribution coefficients (K _d) were determined for the adsorption system as a function of adsorbate concentration. In the ion exchange evaluation part of the study, it is determined that in every concentration range, adsorption ratios of bentonitic clay-heavy metal cations match to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data, adding to that every cation exchange capacity of metals has been calculated. It is shown that the bentonite is sensitive to pH changes, so that the amounts of heavy metal cations adsorbed increase as pH increase in adsorbent-adsorbate system. It is evident that the adsorption phenomena depend on the surface charge density of adsorbent and hydrated ion diameter depending upon the solution pH. According to the adsorption equilibrium studies, the selectivity order can be given as Zn²⁺>Cu²⁺>Co²⁺. These results show that bentonitic clay hold great potential to remove the relevant heavy metal cations from industrial wastewater. Also, from the results of the thermodynamic analysis, standard free energy ΔG ⁰, standard enthalpy ΔH ⁰ and standard entropy ΔS ⁰ of the adsorption process were calculated.     

The network gel polymer electrolyte based on poly(acrylate-co-imide) and its transport properties in lithium ion batteries

Poly (acrylate-co-imide)-based gel polymer electrolytes are synthesized by in situ free radical polymerization. Infrared spectroscopy confirms the complete polymerization of gel polymer electrolytes. The ionic conductivity of gel polymer electrolytes are measured as a function of different repeating EO units of polyacrylates. An optimal ionic conductivity of the poly (PEGMEMA₁₁₀₀-BMI) gel polymer electrolyte is determined to be 4.8 × 10^–3 S/cm at 25 °C. The lithium transference number is found to be 0.29. The cyclic voltammogram shows that the wide electrochemical stability window of the gel polymer electrolyte varies from −0.5 to 4.20 V (vs. Li/Li⁺). Furthermore, we found the transport properties of novel gel polymer electrolytes are dependent on the EO design and are also related to the rate capability and the cycling ability of lithium polymer batteries. The relationship between polymer electrolyte design, lithium transport properties and battery performance are investigated in this research.     

Synthesis of core–shell magnetic ion-imprinted polymer nanospheres for selective solid-phase extraction of Pb2+ from biological,food, and wastewater samples

Magnetic ion-imprinted polymer nanospheres, which have core–shell structures, have been synthesized as an adsorbent for extraction of Pb²⁺ from real samples prior to its flame atomic absorption spectrometric determination. The prepared adsorbent has been characterized using XRD, VSM, TEM, and FTIR measurements. The optimization results revealed that the adsorbent exhibited high selectivity toward Pb²⁺ over other cations such as Cu²⁺ and Zn²⁺. In addition, the removal efficiency of synthesized adsorbent was considerable (q_m?=?171.42?mg g^?1), its calibration curve was linear (0.5?850.0?ng mL^?1), and detection limit was 0.01?ng mL^?1. These results suggested that the prepared nanoadsorbent is an ideal candidate for solid-phase extraction of Pb²⁺ ions.     

(Sodium Alginate/Acrylamide) Semi‐Interpenetrating Polymer Networks and their Usability on Removal of Lead,Cadmium, Nickel Ions

In this study, (sodium alginate (NaAlg)/acrylamide (AAm)) interpenetrating polymer networks (IPN) have been prepared at three different compositions, where the sodium alginate composition varies 1, 2, and 3% (w/v) in 50% (w/v) acrylamide solutions. These solutions have been irradiated with a ⁶⁰Co‐γ source at different doses. The percent conversion was determined gravimetrically and 100% gelation was achieved at the 10.0 kGy dose. The swelling results at pH 7.0 and 9.0 indicated that (NaAlg/AAm)3IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water, with swelling increasing in the order of Ni²⁺>Cd²⁺>Pb²⁺. Diffusion in aqueous solutions of metal ions within (NaAlg/AAm)IPN hydrogels was found to be Fickian character. Diffusion coefficients of (NaAlg/AAm)IPN hydrogels in water and aqueous solutions of metal ions were calculated. The maximum weight loss temperature and half life temperature for NaAlg, PAAm, (NaAlg/AAm)IPN and (NaAlg/AAm)IPN‐metal ion systems were found from thermal analysis studies. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb nickel, cadmium and lead ions from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of metal ion at pH 7.0. Adsorption isotherms were constructed for the (NaAlg/AAm)IPN‐metal ion systems. S type adsorption in the Giles classification system was found.     

Solid-contact Cu(II) ion-selective electrode based on 1,2-di-(<Emphasis Type="Italic">o</Emphasis>-salicylaldiminophenylthio)ethane

The development of Cu(II) solid-contact ion-selective electrodes, based on 1,2-di-(o-salicylaldiminophenylthio)ethane as a neutral carrier, is presented. For the electrodes construction, unmodified carbon ink (type 1 electrode) and polymer membrane-modified carbon ink (type 2 electrode) were used as solid support and transducer layer. Also, carbon ink composite polymer membrane electrode (type 3 electrode) was prepared. The analytical performance of the electrodes was evaluated with potentiometry, while bulk and interfacial electrode features were provided with electrochemical impedance spectroscopy. It is shown that modification of carbon ink with polymer membrane cocktail decreases the bulk contact resistance of the transducer layer and polymer membrane, thus enhancing the analytical performance of the electrode in terms of sensitivity, linear range, and stability of potential. The optimized electrodes of types 2 and 3 exhibit a wide linear range with detection limits of 1.8 × 10⁻⁶ and 1.6 × 10⁻⁶ M, respectively. They are suitable for determination of Cu²⁺ in analytical measurements by direct potentiometry and in potentiometric titrations, within pH between 2.3 and 6.5. The electrodes are selective for Cu²⁺ over a large number of tested transition and heavy metal ions.     

Highly sensitive spectrofluorimetric determination of cysteine by Cu2+-morin complex

p-Toluenesulfonylamide was immobilized on silica gel and on nm-sized silicium dioxide (SiO₂). Their adsorption efficiency toward metal ions was investigated by the batch equilibrium technique. Although silica gel and nm-SiO₂ have the same composition (silicon and oxygen), the difference in their sizes and surface structures results in distinct chemical activity and selectivity. At pH 4, the adsorption capacity of modified silica gel adsorbent was found to be 4.9, 5.0, 33.2, and 12.6 mg g⁻¹ for Cr(III), Cu(II), Pb(II) and Zn(II), respectively. However, the adsorption capacity of nm-SiO₂ adsorbent toward Cr(III) was 26.7 mg g⁻¹ under ultrasonic dispersing. The potential application of p-toluenesulfonylamide-modified silica gel for simultaneous preconcentration of trace chromium, copper, lead and zinc from two standard reference materials and two food samples was performed with satisfactory results. Correspondence: Xijun Chang, Department of Chemistry, Lanzhou University, Lanzhou 730000, P.R. China     

Surface‐initiated atom transfer radical polymerization of a new rhodanine‐based monomer for rapid magnetic removal of Co(II) ions from aqueous solutions

The present study reports synthesis and characterization of a new acrylamide‐based monomer containing rhodanine moiety, N‐3‐amino‐thiazolidine‐4‐one‐acrylamide (ATA). Poly(ATA)‐grafted magnetite nanoparticles (poly(ATA)‐g‐MNPs) were prepared using surface‐initiated atom transfer radical polymerization of the monomer on Fe₃O₄ nanoparticles. The grafted nanoparticles were characterized by Fourier transform infrared analysis, scanning electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The amount of the grafted polymer was 209 mg g⁻¹, as calculated from thermogravimetric analysis experiment. The capability of poly(ATA)‐g‐MNPs to remove Co(II) cations was shown under optimal conditions of contact time, pH, adsorbent dosage, and initial Co(II) concentration. About 86% of the Co(II) cations were removed over 7 minutes. The adsorption kinetics obeyed the pseudo–second‐order kinetic equation, and the Langmuir isotherm model best described the adsorption isotherm with a maximum adsorption capacity of 3.62 mg g⁻¹. The thermodynamic investigation showed spontaneous nature of the adsorption process (ΔG = −2.90 kJ mol⁻¹ at 25°C ± 1°C). In addition, the poly(ATA)‐g‐MNPs were regenerated by simply washing with an aqueous 0.1M HCl solution. The study of the reusability of the prepared magnetic sorbent revealed that the sorbent can be reused without a significant decrease in the extraction efficiency and be recovered by 95.4% after 7 cycles. These findings suggest that the grafted nanoparticles are stable and reusable adsorbent and can be potentially applied to water treatment in efficient removal of Co(II) cations.     

Selective Solid‐phase Extraction of Cu2+ by a Novel Cu(II)‐imprinted Silica Gel

A new Cu(II)‐imprinted salen functionalized silica gel adsorbent was synthesized by surface imprinting technique and was employed as a selective solid phase extraction material for Cu²⁺ removal from aqueous solutions. The samples were characterized by FT‐IR, ¹HNMR, ¹³CNMR, CHNS and DTG techniques. The BET surface area of the silica gel was also determined. The adsorbent was then used for removal of Cu²⁺ from aqueous solutions under different experimental conditions. It was concluded that the synthesized imprinted silica gel had higher selectivity and capacity compared to the non‐imprinted silica gel and the maximal adsorption capacity of 67.3 and 56.5 mg.g^?1 was obtained respectively for ion‐imprinted and non‐imprinted adsorbents. The relative selectivity factor (β) of 50.32 and 31.94 was obtained respectively for Cu²⁺/Ni²⁺ and Cu²⁺/Zn²⁺ pairs. The dynamic adsorption capacity of the imprinted adsorbent was close to the static adsorption capacity due to the fast kinetic of adsorption. Furthermore, the ion‐imprinted adsorbent was recovered and repeatedly used and satisfactory adsorption capacity with acceptable precision was obtained. Each experiment was repeated at least for three times and the mean and the standard deviation for each measurement were calculated. The applicability of the method was examined for Zayandehrood water as real sample. Acceptabe standard deviation was obtained.     

Synthesis of Zn(II) ion-imprinted solid-phase extraction material and its analytical application

Zn(II) ion-imprinted polymer materials used for solid-phase extraction (SPE) column were prepared by the copolymerization of 8-acryloyloxyquinoline (8-AOQ) monomer and a crosslinker ethylene glycol dimethacrylate (EGDMA) in the presence of 2,2′-azobisisobutyronitrile (AIBN) as an initiator. After removing Zn(II) ion from the polymer, molecularly imprinted polymers (MIPs) capable of selectively rebinding Zn(II) ion were obtained. The maximum adsorption capacity of Zn(II) on MIPs beads was about 3.9 mg g⁻¹. The effect of pH and flow rate for quantitative enrichment was also investigated. The Zn(II)-imprinted microbeads have a greater affinity for Zn(II) with respect to Cu(II), Co(II) and Ni(II) ions. A detection limit of 0.65 μg L⁻¹(3σ) and a relative standard deviation (R.S.D., n = 7) of 2.9% were obtained. The MIPs-SPE preconcentration procedure showed a linear calibration curve within concentration range from 0.65 to 130 μg L⁻¹. Zn(II) ion-imprinted beads enabled the selective extraction of zinc ions from a complex matrix, and after 20 times of adsorption and desorption cycle, the recovery of adsorption capacity of Zn(II) on MIPs beads was only decreased 3.2%. The results suggested that these MIPs can be used several times without considerable loss of adsorption capacity.     

A stoichiometric imprinted chelating resin for selective recognition of copper(II) ions in aqueous media

This work reports the preparation of a new copper(II) ion-imprinted polymer (IIP) material, using 5,6;14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane-5,14-diene (DBDA15C4) and 2-vinylpyridine (VP) as a non-vinylated chelating agent and a functional vinyl monomer, respectively. The Cu²⁺ ion can form stable complexes with DBDA15C4 and VP. The stoichiometries of Cu²⁺-DBDA15C4 and ternary Cu²⁺-DBDA15C4-VP complexes were elucidated using conductometric and spectrophotometric methods, and found to be Cu²⁺(DBDA15C4), Cu²⁺(DBDA15C4)₂ and Cu²⁺(DBDA15C4)(VP)₂. The results obtained from solution studies were also supported by ab initio theoretical calculations. The resulting ternary complex Cu²⁺(DBDA15C4)(VP)₂ was copolymerized with ethyleneglycoldimethacrylate, as a cross-linking monomer, via bulk polymerization method. The imprinted copper ion was removed from the polymeric matrix by 0.1 M HNO₃. The Cu²⁺-imprinted polymer particles were characterized by IR spectroscopy and elemental analysis. Optimum pH range for rebinding of Cu²⁺ on the IIP and equilibrium binding time were 7.0-7.5 and 45 min, respectively. Sorbent capacity and enrichment factor for Cu²⁺ were obtained as 75.3 ± 1.9 μmol g⁻¹ and 100, respectively. In selectivity study, it was found that imprinting results in increased affinity of the material toward Cu²⁺ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for five times without a significant decrease in polymer binding affinities.     

A Novel Thermosensitive Gel Adsorbent for Phosphate Ions

Summary: A novel thermosensitive gel adsorbent for phosphate ions was developed and its adsorption/desorption properties were investigated. The gel adsorbent was made by the copolymerization of N-isopropylacrylamide (NIPA) and N-[3-(dimethylamino)propyl]acrylamide (DMAPAA). The adsorbent has a volume phase transition temperature (VPTT), below which it becomes hydrophilic. The tertiary amino groups of DMAPAA were ionized and showed a cationic state when the gel swelled. Phosphate ions were adsorbed onto the ionized tertiary amino groups in the gel network below the VPTT and were desorbed above the VPTT because of the suppression of the ionization of the tertiary amino groups of gel and the shrinkage of the gel.     

Preparation of pH-sensitive hydrogel microspheres of poly(acrylamide-<Emphasis Type="BoldItalic">co</Emphasis>-methacrylic acid) with sharp pH–volume transition

Monodisperse hydrogel microsphere of polyacrylamide (AAm)-methacrylic acid (MAc) cross-linked by N,N′-methylene-bis(acrylamide) (MB) with sharp pH–volume transition was prepared in ethanol. The dynamic light scattering (DLS) was employed to evaluate the pH sensitivity of these microspheres. The effects of main factors: composition of copolymer, cross-linked degree, and initial total concentration or solid content of comonomers were investigated. Osmotic pressure and deformation of cross-linked polymer network were considered as the two dominant factors influencing the characteristics of pH–volume transition. High content of MAc and cross-linked degree increased the osmotic pressure, thereby moving the onset of pH–volume transition to higher pH. Association/dissociation of poly-MAc segments in the domains contributed to the free energy of hydrogel–solvent mixing. As soon as pH was high enough to overcome the osmotic pressure, the dissociated poly-MAc segments simultaneously decreased the osmotic pressure and free energy of hydrogel–solvent mixing, thereby allowing the sharp and large volume transition. As a result, microspheres were prepared with pH–volume transition of almost 12 times to their original volume within a narrow range of pH variation, ca. 0.5. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of quasi‐interpenetrating network of polyacrylamide and poly(N,N‐dimethylacrylamide) on separation of dsDNA fragments and basic protein using CE

Quasi‐interpenetrating network (quasi‐IPN) of linear polyacrylamide (LPA) with low molecular mass and poly(N,N‐dimethylacrylamide) (PDMA), which is shown to uniquely combine the superior sieving ability of LPA with the coating ability of PDMA, has been synthesized for application in dsDNA and basic protein separation by CE. The performance of quasi‐IPN on dsDNA separation was determined by polymer concentration, electric field strength, LPA molecular masses and different acrylamide (AM) to N,N‐dimethylacrylamide (DMA) ratio. The results showed that all fragments in Φ×174/HaeIII digest were achieved with a 30 cm effective capillary length at –6 kV at an appropriate polymer solution concentration in bare silica capillaries. Furthermore, EOF measurement results showed that quasi‐IPN exhibited good capillary coating ability, via adsorption from aqueous solution, efficiently suppressing EOF. The effect of the buffer pH values on the separation of basic proteins was investigated in detail. The separation efficiencies and analysis reproducibility demonstrated the good potentiality of quasi‐IPN matrix for suppressing the adsorption of basic proteins onto the silica capillary wall. In addition, when quasi‐IPN was used both as sieving matrix and dynamic coating in bare silica capillaries, higher peak separation efficiencies, and better migration time reproducibility were obtained.     

Adsorption kinetics of fluoride on iron(III)-zirconium(IV) hybrid oxide

Fluoride occurs in some drinking water sources at levels that are hazardous to health. Tests were conducted to assess the ability of a mineral-based adsorbent to take-up fluoride ion. Consequently, in search of novel adsorbent media, crystalline and hydrous iron(III)-zirconium(IV) hybrid oxide (IZHO) was synthesized, and tested to determine its capacity and kinetics for fluoride adsorption. The Fourier Transform Infrared (FTIR) spectrum of IZHO indicated the presence of Fe–O–Zr linkage which showed hybrid nature of the synthetic oxide. The optimum pH range for fluoride adsorption was ranged between 4.0 and 7.0. The analyses of the isotherm equilibrium data using the Langmuir and the Redlich–Peterson model equations by linear and non-linear methods showed that the data fitted better with latter model than the former. Thermodynamic analysis showed spontaneous nature of fluoride adsorption, and that took place with the increase of entropy. The kinetic data obtained for fluoride adsorption on IZHO at pH 6.8 (±0.1) and room temperature (303±2 K) described both the pseudo-first order and the reversible first-order equations equally well (r ²= ∼0.98–0.99), and better than pseudo second order equation (r ²= ∼0.96–0.98) for higher concentrations (12.5 and 25.0 mg/dm³) of fluoride. The kinetics of fluoride adsorption on the mixed oxide took place with boundary layer diffusion. External mass transport with intra-particle diffusion phenomena governed the rate limiting process, which has been confirmed from the Boyd poor non-linear kinetic plots.     

Chitosan-g-poly(acrylic acid) hydrogel with crosslinked polymeric networks for Ni recovery

In this study, chitosan-g-poly(acrylic acid) (CTS-g-PAA) hydrogel with crosslinked polymeric networks was prepared from an aqueous dispersion polymerization and then used as the adsorbent to recover a valuable metal, Ni²⁺. The adsorption capacity of CTS-g-PAA for Ni²⁺ was evaluated and the adsorption kinetics was investigated using Voigt-based model and pseudo-second-order model. In addition, the effects of pH values and coexisting heavy metal ions such as Cu²⁺ and Pb²⁺ on the adsorption capacity were studied. The results indicate that the as-prepared adsorbent has faster adsorption rate and higher adsorption capacity for Ni²⁺ recovery, with the maximum adsorption capacity of 161.80 mg g⁻¹. In a wide pH range of 3–7, the adsorption capacity keeps almost the same, and even under competitive conditions, the adsorption capacity of CTS-g-PAA for Ni²⁺ is observed to be as high as 54.47 mg g⁻¹. Finally, the adsorption performance of CTS-g-PAA for Ni²⁺ in real water sample and the reusability of the as-prepared adsorbent were evaluated, and also the controlled adsorption mechanism was proposed.     

Synthesis of multidentate functional monomer for ion imprinting

In this work, N,N,N‐tri(2‐carboxyethyl)‐3‐(2‐aminoethylamino)propyl‐trimethoxysilane was prepared as a multidentate functional monomer. The 3D model of the monomer coordinating with Cu²⁺ indicated that the monomer is able to provide five ligating atoms like ethylenediaminetetraacetic acid‐Cu²⁺ to complex with Cu²⁺. When Cu²⁺ was used as a template ion, the synthesis conditions of Cu²⁺‐imprinted polymers were optimized upon orthogonal design. It is interesting to find that Cu²⁺‐imprinted polymer offers a selectivity coefficient of 192.2 when the molar ratio of Cu²⁺ to monomer was exactly 1:1. That means there is no excess ligating atom in the ion‐imprinted polymer and therefore, the nonspecific adsorption could be avoided. Benefiting from the excellent selectivity of Cu²⁺‐imprinted polymer, even if the concentration of Zn²⁺ was 25 times that of Cu²⁺, Cu²⁺‐imprinted polymer still affords a high selectivity coefficient. Finally, the optimal synthesis conditions for Cu²⁺‐imprinted polymer, except the pH, were adopted to prepare Ni²⁺‐imprinted polymer, and Ni²⁺‐imprinted polymer also offered satisfying selectivity to Ni²⁺. That implies this multidentate monomer is adaptable in ion imprinting and, the optimal synthesis conditions of Cu²⁺‐imprinted polymer except pH are likely suitable for the imprinting of other ions besides Cu²⁺.