Synthesis,characterization, and application of amberlite XAD‐2‐ salicylic acid‐ iminodiacetic acid for lead removal from human plasma and environmental samples

A new chelating resin is prepared by coup‐ling Amberlite XAD‐2 with salicylic acid (SAL) through an azo spacer. Then the polymer support was coupled with iminodiacetic acid (IDA). The resulting sorbent has been characterized by FT‐IR, elemental analysis, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 67 mg g⁻¹. The chelating sorbent can be reused for 20 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 95% was obtained for the metal ion with 0.5M nitric acid as eluting agent. The profile of lead uptake on this sorbent reflects good accessibility of the chelating sites in the Amberlite XAD‐2‐SAL/IDA. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb (II) on modified resin were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equili‐brium adsorption data the Langmuir, Freundlich, and Temkin constants were determined 0.428, 20.99, and 7 × 10⁻¹² at pH 5 and 20°C. The method was successfully applied for determination of lead ions in human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide] brushes grafted onto siliceous support for preconcentration and determination of cobalt (II) in human plasma and environmental samples

A chelating matrix prepared by surface grafting of polymer containing a functional monomer, poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-methylacrylamide] (poly(AGE/IDA-co-DMAA) onto a modified silica. The silica surface was modified by silylation with 3-mercaptopropyltrimethoxysilane followed by graft polymerization. Monomer of allyl glycidyl ether-iminodiacetic acid was synthesized by reaction of allyl glycidyl ether with iminodiacetic acid. The chelating sorbent can be reused for 15 cycles of sorption-desorption without any significant change in sorption capacity. The profile of cobalt uptake on the sorbent reflects good accessibility of chelating sites in poly(AGE/IDA-co-DMAA)-grafted silica gel. The equilibrium adsorption data of Co(II) on modified sorbent were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson models. The method was applied for cobalt ions determination in human plasma and sea water sample with satisfactory results.     

Modification and characterization of poly (ethylene terephthalate)‐grafted‐acrylic acid/acryl amide fiber for removal of lead from human plasma and environmental samples

A new fibrous adsorbent was prepared by grafting acrylic acid/acryl amide (AA/AAm) comonomers onto poly (ethylene terephthalate) (PET) fibers. The resulting sorbent has been characterized by Fourier transform infrared (FT‐IR), elemental analysis, thermogravimetric analysis (TGA), FT‐Raman, and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 8. The sorption capacity of functionalized resin is 44.1 mg g^?1. The chelating sorbent can be reused for 20 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 100.2% was obtained for the metal ion with 0.5M nitric acid as eluting agent. Effect of grafting yield, shaking time, shape of sorbent, and pH of the medium on adsorption of the metal ion were investigated. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb (II) on modified fiber were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.236, 10.544, and 9.497 at pH 8 and 20°C, respectively. The method was applied for lead ions determination from human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Modification and characterization of amberlite XAD-2 with calcein blue for preconcentration and determination of copper(II) from environmental samples by atomic absorption spectroscopy

A chelating resin is produced by coupling a dye calcein blue to Amberlite XAD-2 through an azo spacer. The resulting resin has been characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studied for the preconcentration and determination of trace Cu(II) from solution samples. The optimum pH for adsorption of copper ions was 6. The sorption capacity of functionalized resin is 27 mg·g⁻¹. The chelating resin can be reused for 10 cycles without any significant changes in sorption capacity. A recovery of 100% was obtained for Cu(II) when eluted with 0.5 M nitric acid. Scatchard analysis revealed that homogeneous binding sites were formed in the resin. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined 0.036, 2.196 and 0.348 at pH 6 and 20 °C, respectively. The method was applied for Cu(II) assay in environmental samples.     

Water‐soluble copolymers of 1‐vinyl‐2‐pyrrolidone and acrylamide derivatives: synthesis,characterization, and metal binding capability studied by liquid‐phase polymer‐based retention technique

Radical copolymerizations of 1‐vinyl‐2‐pyrrolidone with acrylamide and N,N′‐dimethylacrylamide at different feed ratios were investigated. The copolymers were characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR spectroscopy. The copolymer composition was determined from the ¹H NMR spectra and found to be statistical. The metal complexation of poly(acrylamide‐co‐1‐vinyl‐2‐pyrrolidone) and poly(N,N′‐dimethylacrylamide‐co‐1‐vinyl‐2‐pyrrolidone) for the metal ions Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Pb(II), Fe(III), and Cr(III) were investigated in an aqueous phase. The liquid‐phase polymer‐based retention method is based on the retention of inorganic ions by soluble polymers in a membrane filtration cell and subsequent separation of low‐molecular compounds from the polymer complex formed. The metal ion interaction with the hydrophilic polymers was determined as a function of the pH and the filtration factor. Poly(N,N‐dimethylacrylamide‐co‐1‐vinyl‐2‐pyrrolidone) showed a higher affinity for the metal ions than poly(acrylamide‐co‐1‐vinyl‐2‐pyrrolidone). According to the interaction pattern obtained, Cr(III) and Cu(II) formed the most stable complexes at pH 7. Pb(II) and Zn(II) were not retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 741–750, 1999     

Synthesis, characterization and application of allyl phenol modified amberlite XAD-4 resin for preconcentration and determination of copper in water samples

A new chelating resin was prepared by coupling Amberlite XAD-4 with phenol through an azo spacer, then modified by allyl bromide and characterized (by elemental analysis and IR) and studied for preconcentration of Cu(II) using flame atomic absorption spectrometry (FAAS) for metal monitoring. The optimum pH value for sorption of the above mentioned metal ion was 4.5. The resin was subjected to chemical evaluation through batch binding and column chromatography of Cu(II). The chelating resin can be reused for 15 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 98% was obtained for the metal ion with 0.5 M HNO₃ as eluting agent. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined to be 0.061, 0.193 and 0.045 at pH 4.5 and 25 °C. The method was applied for the copper determination from industrial waste water sample.     

Artificial neural network (ANN) approach for modeling Zn(II) adsorption in batch process

Artificial neural networks (ANN) were applied to predict adsorption efficiency of peanut shells for the removal of Zn(II) ions from aqueous solutions. Effects of initial pH, Zn(II) concentrations, temperature, contact duration and adsorbent dosage were determined in batch experiments. The sorption capacities of the sorbents were predicted with the aid of equilibrium and kinetic models. The Zn(II) ions adsorption onto peanut shell was better defined by the pseudo-second-order kinetic model, for both initial pH, and temperature. The highest R² value in isotherm studies was obtained from Freundlich isotherm for the inlet concentration and from Temkin isotherm for the sorbent amount. The high R² values prove that modeling the adsorption process with ANN is a satisfactory approach. The experimental results and the predicted results by the model with the ANN were found to be highly compatible with each other.     

Monodisperse‐porous N‐methyl‐D‐glucamine functionalized poly(vinylbenzyl chloride‐co‐divinylbenzene) beads as boron selective sorbent

To generate a new sorbent with high boron adsorption capacity, we synthesized monodisperse‐porous poly(vinylbenzyl chloride‐co‐divinylbenzene), poly(VBC‐co‐DVB), beads 8.5 μm in size by a new “modified seeded polymerization” technique. By using their chloromethyl functionality, the beads were derivatized by a simple, direct reaction with a boron‐selective ligand, N‐methyl‐D ‐glucamine (NMDG). The selection of poly(VBC‐co‐DVB) beads as a starting material allowed to obtain high boron sensitive‐ligand density on the beads depending on their high chloromethyl content. In the batch adsorption runs performed using NMDG‐attached poly(VBC‐co‐DVB) beads as sorbent, boron removal was efficiently performed in a wide pH range between 4 and 11. Quantitative boron removal was observed with the sorbent concentration of 4 g/L. In the same runs, plateau value of equilibrium adsorption isotherm was obtained as 14 mg boron/g beads. Relatively higher boron adsorption was explained by high ligand density and high specific surface area of the sorbent. Boron adsorption isotherms were analyzed using Langmuir and Freundlich models. In the kinetic runs performed for boron removal, the equilibrium was attained within 10 min at a value of 98%. The fast kinetic behavior was explained by the smaller particle size and enhanced porosity of the new sorbent. Infinite solution volume model and unreacted core model were used to evaluate boron adsorption onto the NMDG‐attached poly(VBC‐co‐DVB) beads. The results indicated that the adsorption process is controlled by the particle‐diffusion step. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Strontium(II) ion uptake on poly(N‐vinyl imidazole)‐based hydrogels

In this article, we report on the extraction of Sr(II) ions from aqueous solution with a series of poly(N‐vinyl imidazole)‐based hydrogels. The hydrogels were synthesized by the crosslinking of N‐vinyl imidazole with four different crosslinkers with γ rays as initiators. The well‐characterized hydrogels were used as Sr(II) sorbents. Sr(II) uptake was determined with a colorimetric method with Rose Bengal anionic dye. Scanning electron microscopy–energy‐dispersive spectroscopy analysis of the Sr(II)‐loaded polymers was recorded to ascertain the uptake of Sr(II) ions. The experimental adsorption values were analyzed with the Freundlich and Temkin equations, and the kinetics of adsorption were investigated with a pseudo‐second‐order sorption kinetic model. The results show that the equilibrium data fit well in the Freundlich isotherm and followed a pseudo‐second‐order kinetic model. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nickel and copper removal from aqueous solution by an immature coal (leonardite): effect of pH,contact time and water hardness

The removal of Ni(II) and Cu(II) from aqueous solutions by a low cost sorbent (leonardite) was studied. The metal uptake was pH‐dependent and the maximum sorption for two metals was obtained at around pH 5–6. Batch kinetic studies showed that equilibrium time was reached after 2 h of contact time. Equilibrium isotherms were obtained for the adsorption data of the two metals in single and binary systems. Equilibrium data were fitted to Langmuir and Freundlich models and the maximum adsorption capacities were found to be 0.33 mmol of copper and 0.26 mmol of nickel per gram of leonardite. In binary solutions containing the two metals an important reduction of nickel uptake was observed while the sorption of copper was less affected. The presence of Ca²⁺ affected the removal of both copper and nickel ions, although the adsorption of nickel was reduced more than that of copper. Copyright © 2005 Society of Chemical Industry     

Sorption studies for Cd(II) sequestration from aqueous solution on chemically modified Albizia lebbeck

In the present work, a new sorbent was successfully prepared by chemically modifying pods of Albizia lebbeck (AL) by Fenton’s reagent, followed by sodium silicate. Sorption studies were carried out by batch process. The optimum pH was found to be 6. Equilibrium isotherm data were analysed by non-linear curve fitting analysis, to fit Langmuir, Freundlich and Temkin isotherm models. Based on the Langmuir isotherm model, maximum monolayer sorption capacity (qm) was found to be 21.22 mg.g^?1 at 50°C. Breakthrough and exhaustive capacities were found to be 10 and 50 mg.g^?1, respectively. Desorption study showed 95% recovery of Cd(II) ions.     

Pectin‐[(3‐acrylamidopropyl) trimethylammonium chloride‐co‐acrylic acid] hydrogel prepared by gamma radiation and selectively silver (Ag) metal adsorption

Pectin‐[(3‐acrylamidopropyl) trimethylammonium chloride‐co‐acrylic acid] hydrogel has been prepared from the aqueous blend solution of pectin, (3‐acrylamidopropyl) trimethylammonium chloride (APTAC), and acrylic acid (AAc) by applying gamma radiation of different doses (1–25 kGy) from ⁶⁰Co gamma source. The hydrogels were characterized by equilibrium swelling, Fourier transform infrared, differential scanning calorimetry, and scanning electron microscopy. The hydrogels were used in multielement adsorption and it was found that pectin‐(APTAC‐co‐AAc) gel is highly selective toward silver (I) ion among 27 metal ions. The data obtained from equilibrium adsorption studies were fitted in Langmuir and Freundlich adsorption isotherm models and model parameters evaluated. The maximum adsorption capacity of pectin‐(APTAC‐co‐AAc) gel was found to be 67.6413 mg/g of dry gel at sample volume of 25 mL. The kinetic data were tested using pseudo‐first order and pseudo‐second order kinetic models and different adsorption diffusion models such as film diffusion and intra‐particle diffusivity model. Thiourea solution was used for desorption of adsorbed metal ions from the hydrogel. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45906.     

Synthesis and characterization of a surface imprinting silica gel polymer functionalized with phosphonic acid groups for selective adsorption of Fe(III) from aqueous solution

A Fe(III) ion‐imprinted silica gel polymer functionalized with phosphonic acid groups (IIP‐PA/SiO₂) was prepared with surface imprinting technique by using Fe(III) ion as template ion, grafted silica gel as support, and vinylphosphonic acid as functional monomer. The polymer was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, and thermogravimetric analysis. The synthesized imprinted silica gel polymer was used as a sorbent for Fe(III) adsorption. The adsorption properties, such as the effect of solution pH, adsorption kinetic, adsorption isotherm, adsorption selectivity as well as the regeneration of sorbent were studied. The results showd that the prepared sorbent (IIP‐PA/SiO₂) had a short adsorption equilibrium time (12 min) and high adsorption capacity (29.92 mg g^?1) for Fe(III) at the optimal pH of 2.0. The selectivity coefficients of the sorbent for Fe(III) in presence of Cr(III), M_n (II), and Zn(II) were 51.76, 27.86, and 207. 76, respectively. Moreover, the adsorption capacity of the prepared sorbent did not decrease significantly after six repeated use. Thus, the prepared ion‐imprinted silica gel polymer was a promising candidate sorbent for the selective adsorption of Fe(III) from aqueous solutions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45165.     

Novel hexamethylene diamine‐functionalized macroporous copolymer for chromium removal from aqueous solutions

Macroporous copolymers of poly[(glycidyl methacrylate)‐co ‐(ethylene glycol dimethacrylate)] (PGME ) with various crosslinker (ethylene glycol dimethacrylate) concentrations and porosity parameters and additionally functionalized with hexamethylene diamine (PGME‐HD ) were tested as potential Cr(VI ) oxyanion sorbents from aqueous solutions. Kinetics of Cr(VI ) sorption was investigated in the temperature range 298–343 K and the results were fitted to chemical reaction and particle diffusion models. The Cr(VI ) sorption obeys the pseudo‐second‐order model with definite influence of pore diffusion. A temperature rise promotes chromium removal, with a maximum experimental uptake capacity of 4.21 mmol g^?1 at 343 K for the sample with the highest amino group concentration. Equilibrium data were analysed with Langmuir, Freundlich and Temkin adsorption isotherm models. Thermodynamic parameters, i.e. Gibbs free energy (ΔG ⁰), enthalpy (ΔH ⁰) and entropy change (ΔS ⁰) and activation energy of sorption (E _a), were calculated. The Cr(VI) adsorption onto PGME‐HD was found to be spontaneous and endothermic, with increased randomness in the system. Desorption experiments show that chromium anion sorption was reversible and the PGME‐HD sample GMA 60 HD was easily regenerated with 0.1 mol L^?1 NaOH up to 90% recovery in the fourth sorption/desorption cycle. In the fifth cycle, a substantial sorption loss of 37% was observed. © 2016 Society of Chemical Industry     

Removal of Copper (II) Ions from Aqueous Solutions using Na‐mordenite

Abstract

The potential to remove copper (II) ions from aqueous solutions using Na‐mordenite, a common zeolite mineral, was thoroughly investigated. The effects of relevant parameters solution pH, adsorbent dose, ionic strength, and temperature on copper (II) adsorption capacity were examined. The sorption data followed the Langmuir, Freundlich, and Dubinin‐Radushkevich (D‐R) isotherms. The maximum sorption capacity was found to be 10.69 mg/g at pH 6, initial concentration of 40 mg/dm³, and temperature of 40°C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion were calculated. The activation energy (E_a) was found to be 11.25 kJ/mol in the present study, indicating a chemical sorption process involving weak interactions between sorbent and sorbate. The interaction between copper (II) ions and Na‐mordenite is mainly attributable to ion exchange. The sorption capacity increased with the increase of solution pH and the decrease of ionic strength and adsorbent dose. The Na‐mordenite can be used to separate copper (II) ions from aqueous solutions.     

Retention,Thermodynamics and Adsorption Profile of Th(IV) Ions onto 1‐(2‐Pyridylazo)‐2‐Naphthol (PAN) Loaded Polyurethane Foam from Acetate Media and its Separation from Rare Earths

Abstract

The sorption behavior of 2.7×10^?5 M solution of Th(IV) ions on 1‐(2‐pyridylazo)‐2‐naphthol (PAN) loaded polyurethane foam (PUF) has been investigated. The quantitative sorption was occurred from pH 6 to 9 from acetate buffer solutions. The sorption conditions were optimized with respect to pH, shaking time, and weight of sorbent. The sorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms very successfully at low metal ions concentration. The Freundlich isotherm constant (1/n) is estimated to be 0.22±0.01, and reflects the surface heterogeneity of the sorbent. The Langmuir isotherm gives the maximum monolayer coverage is to be 8.61×10^?6 mol g^?1. The sorption free energy of the D‐R isotherm was 17.85±0.33 kJ mol^?1, suggesting chemisorption involving chemical bonding was responsible for the adsorption process. The numerical values of thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) indicate that sorption is endothermic, entropy driven, and spontaneous in nature. The adsorption free energy (ΔG_ads) and effective free energy (ΔG_eff) are also evaluated and discussed. The effect of different anions on the sorption of Th(IV) ions onto PAN loaded PUF was studied. The possible sorption mechanism on the basis of experimental finding was discussed. A new separation procedure of Th(IV) from synthetic rare earth mixture using batch, column chromatography, and squeezing techniques were reported.     

Grafting of poly[styrene‐co‐N‐(4‐vinylbenzyl)‐N,N‐diethylamine] polymer film onto the surface of silica microspheres and their application as an effective sorbent for lead ions

Amino containing polymer of poly[styrene‐co‐N‐(4‐vinylbenzyl)‐N,N‐diethylamine] (PS‐co‐PVEA) was successfully grafted onto the surface of silica microspheres via the seed dispersion polymerization of styrene and N‐(4‐vinylbenzyl)‐N,N‐diethylamine in the presence of divinylbenzene employing the 3‐(methacryloxy)propyltrimethoxysilane activated silica microspheres as the seed. The polymerization led to thin chelating polymer films (30 nm) coated silica microspheres (silica@polymer) as determined by transmission electron microscopy. The synthesized silica@polymer composites were used as sorbents for lead ions (Pb²⁺). The adsorption properties, such as the pH effect, the adsorption kinetic, adsorption isotherm as well as the reuse of the silica@polymer sorbent were evaluated. The results demonstrated that the optimized adsorption condition was under neutral and the silica@polymer sorbent was efficient since it showed higher adsorption amounts (8.0 mg/g) and shorter adsorption equilibrium time (8 h) than that of the PS‐co‐PVEA microspheres and the pristine silica microspheres. Moreover, the silica@polymer sorbent was reusable even after four cycles of adsorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39973.     

Biosorption of Cu(II) onto agricultural materials from tropical regions

BACKGROUND: In Ghana, the discharge of untreated gold mine wastewater contaminates the aquatic systems with heavy metals such as copper (Cu), threatening ecosystem and human health. The undesirable effects of these pollutants can be avoided by treatment of the mining wastewater prior to discharge. In this work, the sorption properties of agricultural materials, namely coconut shell, coconut husk, sawdust and Moringa oleifera seeds for Cu(II) were investigated. RESULTS: The Freundlich isotherm model described the Cu(II) removal by coconut husk (R² = 0.999) and sawdust (R² = 0.993) very well and the Cu(II) removal by Moringa oleifera seeds (R² = 0.960) well. The model only reasonably described the Cu(II) removal by coconut shell (R² = 0.932). A maximum Cu(II) uptake of 53.9 mg g^?1 was achieved using the coconut shell. The sorption of Cu(II) onto coconut shell followed pseudo‐second‐order kinetics (R² = 0.997). FTIR spectroscopy indicated the presence of functional groups in the biosorbents, some of which were involved in the sorption process. SEM‐EDX analysis confirmed an exchange of Mg(II) and K(I) for Cu(II) on Moringa oleifera seeds and K(I) for Cu(II) on coconut shell. CONCLUSION: This study shows that coconut shell can be an important low‐cost biosorbent for Cu(II) removal. The results indicate that ion exchange, precipitation and electrostatic forces were involved in the Cu(II) removal by the biosorbents investigated. Copyright © 2011 Society of Chemical Industry     

Behaviour and mechanism of enhanced phosphate sorption on loess modified with metals: equilibrium study

BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters. In developing countries, algae blooming in lakes have threatened the quality of drinking water due to the lack of proper management of phosphate‐containing wastewaters from mining sites and industry. MAJOR RESULTS: The sorption behaviour of phosphate on loess modified by metals (Zn(II), Cu(II) and Pb(II)) was investigated in this paper. Zn(II) and Cu(II) sorption on the loess was attributed to the constituent silicate minerals while the sorption of Pb(II) was assigned to natural carbonate in the loess. The sorption affinity of phosphate towards the modified sorbent was as follows: Pb(II) (221.3–832.2 L g⁻¹) > Cu(II) (20.26 L g⁻¹) > Zn(II) (0.77–1.90 L g⁻¹) > loess (0.11 L g⁻¹) with regard to the partition coefficient. The sorption isotherms were well fitted by an extended Henry's law with multi‐linearity. Several factors including metal loading, pH, sorbent dosage and temperature were investigated and all were found to correlate positively with phosphate sorption. The enthalpy and entropy changes during phosphate sorption on Pb(II) loaded loess were predicted as 14.32 kJ mol⁻¹ and 128.45 J mol⁻¹ K⁻¹, respectively. The sorption mechanism for phosphate on Pb(II) doped loess was investigated by FT‐IR spectra from which the sorption was attributed to chemical bonding with lead carbonate and physisorption with surface adsorbed phosphate as well as diffusion through micropores into the sorbent. CONCLUSIONS: Pb(II) loaded loess shows the best performance for phosphate removal from aqueous solution. The optimum conditions for sorption were pH = 9.5, lead modified loess sorbent dosage = 10 g L⁻¹, temperature = 35 °C and Pb(II) loading 295 mg g⁻¹. Copyright © 2008 Society of Chemical Industry     

Light‐triggered reversible solubility of α‐cyclodextrin and azobenzene moiety complexes in PDMAA‐co‐PAPA via molecular recognition

Photoresponsive polymer with azobenzene pendant group (PDMAA‐co‐PAPA) was synthesized by radical polymerization of N,N‐dimethylacrylamide (DMAA) and N‐4‐phenylazophenyl acrylamide (PAPA), and the characterization of the inclusion complexes of the PDMAA‐co‐PAPA with α‐cyclodextrin (α‐CD) were performed by FTIR, GPC, ¹H NMR, 2D NOESY, and UV–vis spectroscopy. It was found that the solubility of PDMAA‐co‐PAPA and α‐CD inclusion complexes in aqueous solution showed tunable property, which could be triggered by alternating UV–vis light irradiation at a certain temperature due to the effect of molecular recognition of α‐CD with azobenzene moiety in the polymer. After UV irradiation, the lower critical solution temperature (LCST) of the polymer aqueous solution increased slightly without α‐CD while the LCST decreased sharply at presence of α‐CD. Furthermore, UV spectroscopy showed that the photoisomerization of the polymer solution went on rapidly and reversibly, and 2D NOESY data suggested that the inclusion complexation of α‐CD with trans azobenzene moiety and the decomplexation with cis azobenzene resulted in reversible solubility behavior when objected to UV and Vis light irradiation alternately. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008