Super porous α-, β-, γ-cyclodextrin cryogels with high active agent loading and controllable release profiles

Cyclodextrins (CDs) are truncated cone-like structures that are natural cyclic oligosaccharides. Here, a simple preparation method for super porous poly(α-CD), poly(β-CD), and poly(γ-CD) cryogels crosslinking with divinyl sulfone at 150%, 100% and 125% mole ratios with respect to the α-CD, β-CD, and γ-CD molecules, respectively, under cryogenic conditions, is reported. The interconnected homogeneous pore distribution of CD-based cryogels with pore sizes in the range of 5–100 μm is confirmed by SEM analysis. The CD-based cryogels weighing 10 mg are determined as hemocompatible with <1% hemolysis ratios and >79% blood clotting indexes; whereas the same materials weighing 1 mg are biocompatible with >75% cell viability on L929 fibroblasts. Additionally, active agent adsorption/delivery efficiencies of CD-based cryogels utilizing two active agents, Bisphenol A (BPA, a carcinogenic compound) and Curcumin (CUR, a polyphenolic compound), are individually evaluated. It was revealed that p(γ-CD) cryogels exhibited the highest active agent loading capacity for BPA, 87 ± 13 mg/g, whereas p(α-CD) cryogels showed the highest loading capacity for CUR, 136 ± 4 mg/g. Moreover, the active agent release from p(α-CD), p(β-CD), and p(γ-CD) cryogel networks at pH 7.4 and 37°C were determined as 40.6 ± 2, 35.3 ± 2, and 34 ± 1 mg/g for BPA, and 1.07 ± 0.2, 1.27 ± 0.1, and 1.37 ± 0.1 mg/g for CUR, respectively, within 96 h.     

In situ preparation of polyaniline within neutral,anionic, and cationic superporous cryogel networks as conductive,semi‐interpenetrating polymer network cryogel composite systems

Polyaniline [p(An)], one of the most known conducting polymers, was prepared within superporus nonionic polyacrylamide [p(AAm)], anionic poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid sodium salt) [p(AMPS)], and cationic poly(3‐acrylamidopropyltrimethyl ammonium chloride) [p(APTMACl)] cryogels. After they were synthesized, washed, and dried, the neutral p(AAm), anionic p(AMPS), and cationic p(APTMACl) cryogels were soaked in an ammonium persulfate/aniline solution (1:1.25 ratio) in 1 M hydrochloric acid for the in situ oxidative polymerization of p(An) with the cryogel matrices as templates or reactors. The prepared p(AAm)/p(An), p(AMPS)/p(An), and p(APTMACl)/p(An) semi‐interpenetrating polymer network (semi‐IPN) conductive cryogel composites were characterized with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and conductivity analysis. The SEM images revealed that the superporus cryogel networks were almost completely filled with p(An) conductive polymers (CPs). Among the cryogel–CP semi‐IPNs, we found that p(AAm)/p(An) semi‐IPN conductive cryogel composites provided the highest conductivity values of 1.4 × 10^?2 ± 4 × 10^?4 S/cm; this was a 6.4 × 10⁶ fold increase in the conductivity from the values of 2.2 × 10^?9 ± 1 × 10^?10 for p(AAm) cryogels. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44137.     

Ag+ ions imprinted cryogels for selective removal of silver ions from aqueous solutions

ABSTRACT

The removal of heavy metal ions from aquatic media or any conditions is crucial. Silver ions turn out to be the important example of this problem on earth when these are released to the environment. In the present study, silver ions (Ag⁺) imprinted poly(hydroxyethyl methacrylate) (PHEMA)-based cryogels were prepared using N-methacryloyl-L-cysteine as functional monomer, to be chelated with Ag⁺ ions. The maximum adsorption capacity of Ag⁺-imprinted polymeric cryogel was found to be 49.27 mg/g from aqueous solutions. To investigate the affinity of Ag⁺-imprinted PHEMAC cryogel column, photographic film material from the natural silver ion source was used. The recovery results were 72.8% for the Ag⁺-imprinted PHEMAC cryogel and 0.62% for the non-imprinted PHEMAC cryogels. These values clearly showed the selectivity of the Ag⁺-imprinted PHEMAC cryogel column. The adsorption–desorption cycle was performed more 10 times with use of the same Ag⁺-imprinted PHEMAC cryogel for the determination of reuse. These molecularly imprinted cryogels were used in adsorption process for a long time with no significant loss.     

Preparation of an affinity cryogel column for lysozyme purification

Affinity cryogels were synthesized using tris(hydroxymethyl)aminomethane (Tris) as ligand for specific interactions with the lysozyme (LYZ). The cryogel was produced by cryo-copolymerization at ?12°C. A central composite rotational design 2² was used to optimize the immobilization procedure of the Tris on the cryogel. A maximum adsorption for LYZ (149.5 mg/g) was achieved when 376 mg/mL of Tris and 3.06 mol/L of sodium borohydride were used during the Tris immobilization. Chromatographic separation of LYZ from chicken egg white was done with a purity of 92.13%. Results showed that the affinity cryogel was a potential separation medium for LYZ purification.     

HSA immobilized novel polymeric matrix as an alternative sorbent in hemoperfusion columns for bilirubin removal

HSA immobilized poly(2-hydroxyethylmethacrylate), HSA-P[HEMA], cryogel monolith was examined as an alternative sorbent to be used in hemoperfusion columns for bilirubin removal from serum. The cryogel monolith synthesis was performed by free radical polymerization using MBAA as crosslinker, APS and TEMED as redox pair. Cyanogen bromide (CNBr) was used as a matrix-activating agent for the preparation of immobilized cryogels. Control cryogel monolith, P[HEMA], and HSA-P[HEMA] were characterized by swelling test, SEM images, porosity and surface area measurements, and blood compatibility tests. Activation and immobilization processes were optimized. The removal of bilirubin from plasma samples overloaded with bilirubin was performed using P[HEMA] cryogel monoliths containing different amounts of immobilized HSA in continuous mode. Several factors affecting adsorption capacity of the matrix such as incubation time, HSA concentration, bilirubin concentration in plasma and temperature were analysed. The maximum bilirubin removal from plasma was 25.4 mg/g at 37.5 °C. The desorption agent was 0.1 M NaOH and 1.0 M NaCl containing solution. The reusability was tested for 10 consecutive adsorption–desorption cycles. The adsorption isotherm models and kinetics of process were also studied.     

Pullulan/poly(N-vinylimidazole) cryogel: An efficient adsorbent for methyl orange

Pullulan/poly(N-vinylimidazole) (PNVI) hybrid cryogels were synthesized under free radical polymerization and chemical crosslinking conditions in an alkaline, aqueous solution of pullulan (PUL), N-vinylimidazole (NVI), ammonium persulfate and epicholorohydrin (ECH) at −18°C. PUL and PNVI cryogels alone were also synthesized under similar conditions. Optimum cryogel formation conditions were determined by considering product yields and gel fractions of the samples. The products were characterized by elemental analysis, FTIR-ATR spectrometry, Thermal gravimetric analysis, and scanning electron microscopy (SEM) analyses. It has been found that PUL/PNVI hybrid samples bear improved physicochemical properties compared to ECH crosslinked PUL and PNVI samples alone. They act as hydrogels in aqueous medium reaching equilibrium swelling capacity values of the order of 600%. Dried PUL/PNVI cryogels show higher thermal stability than the dried cryogels of the parent polymers and maintain their physical integrity over a prolonged time period. Macroporous morphology was revealed by SEM analysis. Having 54.2 mg/g maximum equilibrium adsorption capacity in 200 ppm methyl orange solution and maintaining 95% of its adsorption capacity at the end of seven consecutive adsorption/desorption cycles, PUL/PNVI cryogel proved to be an efficient and durable dye adsorbent using methyl orange as the model compound in aqueous solution.     

Removal of organic water pollutant using magnetite nanomaterials embedded with ionic copolymers of 2‐acrylamido‐2‐methylpropane sodium sulfonate cryogels

Magnetite cryogel composites as macroporous crosslinked matrices have received wide attention and attract much interest in the water purification and desalination industry. They can be used to produce effective adsorbents with high adsorption rate, capacity and desorption for water pollutants. In this work, the incorporation of magnetite nanoparticles into cryogels by the in situ method is proposed to increase the dispersion of nanoparticles in the gel composites and to produce effective magnetic materials with high adsorption capacities. Ionic sodium‐2‐acrylamido‐2‐methylpropane sulfonate (Na‐AMPS) monomer was selected to prepare cryogels as the homopolymer or copolymers with 2‐hydroxyethyl methacrylate (HEMA) or N‐vinyl pyrrolidone (VP) by the crosslinking polymerization technique in the frozen state. Magnetite nanoparticles were introduced into the cryogel by the in situ co‐precipitation method after introducing iron cations into the cryogel networks. The surface morphologies, crystal structure, magnetite content, thermal stability and magnetic properties were determined for the cryogels and their magnetite composites. The magnetite cryogel composites show significantly enhanced methylene blue dye removal in short times with higher adsorption efficiencies and good regeneration to form an effective adsorbent for water treatment. © 2017 Society of Chemical Industry     

Poly ionic liquid cryogel of polyethyleneimine: Synthesis,characterization, and testing in absorption studies

Here, we report the synthesis of polyethyleneimine (PEI) cryogels for the first time via cryopolymerization technique. The crosslinking of amine groups on the branched PEI chains is accomplished with epoxy groups of glycerol diglycidyl ether (GDE) based on epoxy–amine reactions in excess water at ?18 °C in about 16 h. Superporous PEI cryogels with pore sizes >100 μm were shown to have very fast equilibrium swelling behavior, e.g., 10 s to reach maximum swelling in DI water. Furthermore, the synthesized PEI cryogels were exposed to anion exchange reaction after protonation by HCl treatments to generate PEI ionic liquid cryogels containing hexafluorophosphate, thiocyanate, dicyanamide, and tetrafluoroborate. It was also demonstrated that PEI cryogels modified with [PF₆]^? absorbed 47.8 ± 5.7 mg/g of bovine serum albumin (BSA). Moreover, PEI cryogels were shown to be very useful as simple filtration filling materials for the direct removal of organic dyes such as methyl orange (MO) and eosin Y (EY) from their corresponding aqueous solutions with 98.5 and 98.6% yields, respectively. The separation of methylene blue (MB) from MO and EY mixture by using PEI cryogels as column filler materials was also demonstrated. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43478.     

Microfibrillated cellulose reinforced poly(vinyl imidazole) cryogels for continuous removal of heavy metals

Interconnected macro-porous cryogels with robust mechanical structure and high adsorption capacity are desirable for the wastewater clean-up. However, some functional alkenyl-based monomer such as vinyl imidazole (VIM) could not be individually polymerized to form the cryogel with a robust structure for applications. Herein, a strategy has been developed to fabricate the poly(VIM) cryogel using microfibrillated cellulose (MFC) as reinforcing agent. Structural characterizations indicated that the poly(VIM)/MFC showed interconnected macropores of 12 ± 10 μm and high VIM contents. Underwater compression experiments displayed that the hysteresis loops changed slightly and the energy loss coefficients were less than 23% during loading-unloading 200 cycles, highlighting the excellent shape recovery and fatigue resistance. Batch adsorption indicated that the adsorption capacities of the poly(VIM)/MFC cryogel to Cu(II), Pb(II), Zn(II), Cd(II), Ni(II), and Co(II) were 87.4, 53.9, 48.6, 44.3, 23.8, and 20.1 mg/g, respectively. The pseudo second-order kinetic and Langmuir model can fit the adsorption process well, confirming the single-layer homogeneous chemisorption. Dynamic adsorption displayed that the loaded Cu(II) ions could be rapidly adsorbed and hardly flow through the poly(VIM)/MFC cryogel, indicating the extremely fast adsorption at the flow mode. This study shows a novel strategy to fabricate the robust cryogel for environmental remediation.     

Supermacroporous hybrid polymeric cryogels for efficient removal of metallic contaminants and microbes from water

A supermacroporous cryogel column of chitosan-dimethylaminoethyl methacrylate (DMAEMA)-magnetite has been synthesized. The cationic and magnetic properties of chitosan/DMAEMA and magnetite, respectively, allow the adhesion of metals and microbes to the matrix. The large interconnected pores (20–100 µm) with porosity greater than 85% of the cryogels facilitate fast water movement. At lab scale (approximately 2 mL bed volume), static binding capacity of 100% (load: 4.5 ppm arsenic and 2300 ppm chromium) and dynamic binding capacity of 65% for arsenic (load: 58 ppm) was observed. The binding capacity at pilot scale (approximately 300 mL bed volume) was found to be 11.5 mg arsenic and 14.22 mg chromium. There was 100% binding of microbes (Escherichia coli and Streptococci) both at lab and pilot scale. The results were propitious and indicated the suitability of cryogel filter as a single device for the removal of arsenic, chromium, and microbes in field samples.     

Synthesis of lysozyme imprinted column with macroporous structure and enhanced selectivity: Utilization of cryogelation technique and electrostatic functional monomers

Applicability of molecularly imprinted polymers (MIP) in conventional protein separation processes demands monolithic construction of columns with macroporous structure in addition to the high specificity and adsorption capacity. In this study, therefore, lysozyme (Lyz) imprinted monolithic cryogel columns were synthesized using electrostatic functional monomers (EFMs) to provide strong interactions between template and polymer, leading to specific recognition and capture of Lyz. SEM images and FTIR spectroscopy analysis confirmed the macroporous structure and presence of EFMs in the samples. Adsorption isotherms, heterogeneity, and breakthrough curves as well as selectivity of the molecularly imprinted cryogels (EFMs‐MIC) and non‐imprinted cryogels (EFMs‐NIC) were investigated. Results showed effective imprinting with a maximum adsorption capacity of 211 mg/g and a high imprinting factor (IF) of 4.2 at low Lyz concentrations. A high relative selectivity coefficient of 7.24 was obtained for Lyz over cytochrome c, a competing protein, indicating that the imprinted sites could well distinguish Lyz. Reusability of MICs was also examined, where insignificant changes were observed in the cryogel adsorption/desorption characteristics after four cycles. Therefore, it is suggested to use EFMs and cryogelation in the synthesis of imprinted monolithic cryogels column for application in conventional protein separation processes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42880.     

十六烷基三甲基溴化铵改性X分子筛对铬酸盐的吸附平衡及动力学

用十六烷基三甲基溴化铵(HTAB)对X分子筛改性,考察改性分子筛对水中铬酸盐的吸附平衡及吸附动力学。采用XRD和FT-IR对样品进行表征,结果表明改性后HTAB-X分子筛在保持原有结构和形貌同时,接枝了一定量的长链季铵盐阳离子功能基团。吸附实验表明,0.7 g改性分子筛在25℃、pH=6条件下,去除率为94.14%,比X分子筛提高了近36%。HTAB-X分子筛对铬酸盐的吸附遵循Langmuir模型,最大吸附容量为16.33 mg/g。热力学和动力学分析表明,该吸附过程为自发的放热过程,适合在常温下进行;吸附过程遵循准二级动力学模型,平衡吸附容量qe,cal达到2.71 mg/g,速率常数k2为0.362 g/(mg·min)。     

Molecularly imprinted smart cryogels for selective nickel recognition in aqueous solutions

Smart polymers with fast response to slight changes show high practicability in separation and removal applications, such as water and wastewater treatment. Molecular imprinted polymers (MIPs) are designed to possess specific binding sites enabling the recognition of the target analytes. In this article, the newly synthesized smart adsorbents were used for the selective removal of nickel [Ni(II)] ions from aqueous solutions, which have dual (pH and temperature) memory for the recognition of Ni(II) ions due to the self-assembled recognition sites in MIP structure. The Ni(II)-MIP smart cryogels were prepared by cryopolymerization of N-isopropylacrylamide (NIPAm) and N-methacryloyl-l -histidine (MAH) monomers to incorporate their smart features for removal of Ni(II) ions in a selective and temperature-modulated way. The maximum binding capacity of Ni(II) ions onto MIP smart cryogel was determined at pH 6 as 414 μg g⁻¹ at 20°C and only 104.5 μg g⁻¹ at 40°C, respectively. The adsorption reached an equilibrium within 30 min, while 85% of the bound amount of Ni(II) ions was achieved in only 15 min. This unique MIP cryogel as a smart and selective adsorbent was able to remove Ni(II) ions immediately by a significant temperature and pH change as an alternative application for water and wastewater treatment.     

Reactive green HE‐4BD functionalized supermacroporous poly(hydroxyethyl methacrylate) cryogel for heavy metal removal

The aim of this study was to investigate the heavy metal adsorption performance of supermacroporous poly(hydroxyethyl methacrylate) [PHEMA] cryogel. The PHEMA cryogel was produced by cryo‐polymerization. The PHEMA cryogel was characterized by scanning electron microscopy (SEM). The PHEMA cryogel containing 385 μmol Reactive Green HE‐4BD/g were used in the adsorption studies. Adsorption capacity of the PHEMA cryogel for the metal ions, i.e., Cu²⁺, Cd²⁺, and Pb²⁺ were investigated in aqueous media containing different amounts of the ions (5–600 mg/L) and at different pH values (3.2–6.9). The maximum adsorption capacities of the PHEMA cryogel were 11.6 mg/g (56 μmol/g) for Pb²⁺, 24.5 mg/g (385 μmol/g) for Cu²⁺ and 29.1 mg/g (256 μmol/g) for Cd²⁺. The competitive adsorption capacities were 10.9 mg/g (52 μmol/g) for Pb²⁺, 22.1 mg/g for Cd²⁺ (196 μmol/g) and 23.2 mg/g (365 μmol/g) for Cu²⁺. The PHEMA/Reactive Green HE‐4BD cryogel exhibited the following metal ion affinity sequence on molar basis: Cu²⁺ > Cd²⁺ > Pb²⁺. The PHEMA/Reactive Green HE‐4BD cryogel can be easily regenerated by 50 mM EDTA with higher effectiveness. These features make the PHEMA/Reactive Green HE‐4BD cryogel a potential adsorbent for heavy metal removal. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Complexation of macroporous amphoteric cryogels based on N,N‐dimethylaminoethyl methacrylate and methacrylic acid with dyes,surfactant, and protein

Macroporous amphoteric cryogels based on N,N‐dimethylaminoethylmethacrylate and methacrylic acid p(DMAEM‐co‐MAA) crosslinked by N,N′‐methylenebisacrylamide (MBAA) were synthesized by radical copolymerization of monomer mixtures in cryoconditions. The structure and morphology of cryogels were evaluated by FTIR and SEM. Cryogels exhibited interconnected porous structure with pore size ranging from 40 to 80 µm, which depended on their crosslinking degree. The value of the isoelectric point (IEP) of equimolar amphoteric cryogel determined from the water flux was equal to 4.4, while the IEP of cryogel with the excess of DMAEM units was equal to 7.1. The mechanical strength of equimolar amphoteric cryogels increases with increasing amount of crosslinking agent. The complexation ability of amphoteric cryogels with respect to surfactant, dyes, and protein was demonstrated. The adsorption isotherms with respect to anionic surfactant—sodium dodecylbenzene sulfonate (SDBS) and protein—lysozyme correspond to Langmuir equation, while adsorption isotherms of anionic and cationic dyes—methylene blue (MB) and methyl orange (MO) are well described by Freundlich equation. It was found that the binding ability of p(DMAEM‐co‐MAA) with respect to various low‐ and high‐molecular weight compounds changes in the following order: SDBS > lysozyme ? MO > MB. The preferential adsorption of MB from the mixture of protein and MB was shown. The quantitative release of protein, surfactant and dye molecules from the matrix of cryogels takes place at the IEP of cryogel. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43784.     

Histidine Containing Macroporous Affinity Cryogels for Immunoglobulin G Purification

A supermacroporous cryogel was prepared to obtain an efficient and cost effective purification of IgG from human plasma. N-methacryloyl-(L)-histidine methyl ester (MAH) was chosen as the pseudospecific ligand and/or comonomer. Poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methylester) [PHEMAH] cryogel was produced by free radical polymerization initiated by N,N,N′,N′-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. PHEMAH cryogel had a specific surface area of 38.6 m²/g. PHEMAH cryogel was characterized by swelling studies, scanning electron microscopy and elemental analysis. PHEMAH cryogel containing 113.7 µmol MAH/g was used in the purification of IgG from human plasma. Compared with the poly(hydroxyethyl methacrylate) (PHEMA) cryogel (0.4 mg/g), the IgG adsorption capacity of the PHEMAH cryogel (24.7 mg/g) was improved significantly due to the MAH incorporation into the polymeric matrix. The maximum amount of IgG adsorption from aqueous solution in phosphate buffer was observed at pH 7.4. The IgG adsorption amount from human plasma was 97.3 mg/g with a purity of 94.6%. It was observed that IgG could be repeatedly adsorbed and eluted with PHEMAH cryogel without significant loss in the adsorption capacity.     

Sorption of chromium oxy‐anions onto cationized ligno‐cellulosic material

Quaternary ammonium groups were grafted onto ligno‐cellulosic material (cotton, wood sawdust, and maize‐cob flour) to obtain a support able to adsorb oxy‐anions containing chromium atoms (chromate and dichromate). For both anions in aqueous solutions, adsorption proceeded very quickly and reached a limit value dependent on the rate of ammonium grafting; at saturation, the Cr/N⁺ ratio was always close to 1/1 for chromate anions, but two ammonium sites were needed to link a dichromate anion in a stable structure, resulting in the same 1/1 Cr/N⁺ ratio. Tentatives for modeling the adsorption process were performed with the Langmuir, Freundlich, and Jossen equations. A nearly total desorption occurred only when these saturated supports were treated with solutions of high ionic strength (4M potassium chloride). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1660–1665, 2003     

Poly(acrylamide‐allyl glycidyl ether) cryogel as a novel stationary phase in dye‐affinity chromatography

Poly(acrylamide‐allyl glycidyl ether) [poly(AAm‐AGE)] cryogel was prepared by bulk polymerization which proceeds in an aqueous solution of monomers frozen inside a glass column (cryo‐polymerization). After thawing, the monolithic cryogel contains a continuous polymeric matrix having interconnected pores of 10–100 μm size. Cibacron Blue F3GA was immobilized by covalent binding onto poly(AAm‐AGE) cryogel via epoxy groups. Poly(AAm‐AGE) cryogel was characterized by swelling studies, FTIR, scanning electron microscopy, and elemental analysis. The equilibrium swelling degree of the poly(AAm‐AGE) monolithic cryogel was 6.84 g H₂O/g cryogel. Poly(AAm‐AGE) cryogel containing 68.9 μmol Cibacron Blue F3GA/g was used in the adsorption/desorption of human serum albumin (HSA) from aqueous solutions and human plasma. The nonspecific adsorption of HSA was very low (0.2 mg/g). The maximum amount of HSA adsorption from aqueous solution in acetate buffer was 27 mg/g at pH 5.0. Higher HSA adsorption value was obtained from human plasma (up to 74.2 mg/g). Desorption of HSA with a purity of 92% from Cibacron Blue F3GA attached poly(AAm‐AGE) cryogel was achieved using 0.1M Tris/HCl buffer containing 0.5M NaCl. It was observed that HSA could be repeatedly adsorbed and desorbed with poly(AAm‐AGE) cryogel without significant loss in the adsorption capacity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation,characterization, and utilization of cationized hemp as anion exchanger for removing permanganates and dichromate anions

Using a software experimental design strategy and through 25 experiments, steam exploded hemp bast fibers (HBF) as well as their shives were cationized by the exhaustion method using 3‐chloro‐2‐hydroxypropyl trimethyl ammonium chloride solution. The results obtained revealed that at pH 13, raising the temperature of a bath containing 100 g/L cationizing agent aqueous solution at liquor to substrate ratio 1/15 to 80°C for 90 min produces the cationized forms of HBFs as well as their shives with percent nitrogen content 0.2240 and 0.4893 respectively. The statistical analysis for the results indicated that the percent nitrogen content is significantly influenced by factors of time, pH, and primarily the cationizing agent concentration. The cationized forms of HBFs as well as their shives, having amino contents 76 and 104 mequiv/100 g respectively, were characterized by studying their potentiometric titration and were analyzed by thermogravimetric analysis. Both of these cationized substrates were utilized as anion exchangers for adsorption of permanganate and dichromate anions from their acidic aqueous solutions. Adsorption dynamics of the removal of such anions were first‐order reactions whereas the adsorption isotherms showed that the adsorption of those anions on all the aforementioned anion exchangers was favorable. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Perchlorate Uptake from Aqueous Solutions by Calcined Mg-Al Layered Double Hydroxides

The calcined layered double hydroxides (CLDHs) with 3:1 Mg/Al molar ratio were observed to acquire a high removal efficiency of perchlorate. And they were applied into perchlorate adsorption process with the initial 100 mg/L perchlorate solution in order to analyze removal efficiencies of perchlorate on various influential factors. The results represented that 1.5 g/L CLDHs could achieve ideal adsorption efficiencies of perchlorate at the pH range of 7–9 and at the temperature of 25°C. The removal efficiencies of perchlorate increased up to a maximum efficiency with the increasing dose of CLDHs. Acidic or highly alkaline environment adversely affected perchlorate adsorption. The adsorption process was found to be endothermic due to the higher adsorption capacity in CLDHs with the increasing temperature. The removal of perchlorate was best represented by the pseudo second-order kinetics model and Langmuir isotherm model. Co-existing anions tests showed that the anions of higher valence had a more significant effect than the monovalent anions during the adsorption process. Finally, the adsorption process was further validated by the X-ray patterns and Fourier-transform Infrared spectra of CLDHs. Results demonstrated potential utility of CLDHs that could be developed into a viable technology for perchlorate removal from water.