Melamine‐based microporous polymer for highly efficient removal of copper(II) from aqueous solution

In this study, we investigated the ability of a melamine‐based microporous polymer network as an adsorbent for removal of copper(II) species from aqueous solutions. A designed Schiff based network (SNW) with high specific surface area was synthesized using melamine and terephthalaldehyde monomers at 180 °C for 3 days followed by a freeze‐drying process. The porous structure of the material was confirmed by SEM analysis and CO₂ adsorption/desorption studies at 77.3 K. The adsorption character of the SNW polymer for various metal salts, namely Pb(II), Fe(II), Hg(II), Zn(II), Ni(II) and Cd(II), was investigated and a specific sorption behaviour against Cu(II) salts was observed. The role of pH and contact time was examined and the highest adsorption capacity for Cu(II) was found as 92% with pH 3.5 at the end of 300 min. As evidenced by XRD and Fourier transform infrared spectral analysis, the sorption mechanism is attributed to the coordination system formed between amino groups in the porous structure and Cu(II) ions. Reusability of the system was also demonstrated by applying four cycles without any significant loss of activity. © 2016 Society of Chemical Industry     

功能型配位聚合物在气体吸附方面的研究

作为潜在的新型功能材料,配位聚合物今年来得到科学家的普遍关注.本文主要对配位聚合物作为气体吸附材料的研究和潜在应用进行了描述和总结,并对其发展前景作出了展望.     

Optimization of kinetic data for two‐stage batch adsorption of Pb(II) ions onto tripolyphosphate‐modified kaolinite clay

BACKGROUND: Most adsorption studies consider only the adsorption of pollutants onto low cost adsorbents without considering how equilibrium and kinetic data can be optimized for the proper design of adsorption systems. This study considers the optimization of kinetic data obtained for the removal of Pb(II) from aqueous solution by a tripolyphosphate modified kaolinite clay adsorbent. RESULTS: Modification of kaolinite clay with pentasodium tripolyphosphate increases its cation adsorption capacity (CEC) and specific surface area (SSA) from 7.81 to 78.9 meq (100 g)^?1 and 10.56 to 13.2 m² g^?1 respectively. X‐ray diffraction patterns for both unmodified and tripolyphosphate‐modified kaolinite clay suggest the modification is effective on the surface of the clay mineral. Kinetic data from the batch adsorption of Pb(II) onto the tripolyphosphate‐modified kaolinite clay adsorbent were optimized to a two‐stage batch adsorption of Pb(II) using the pseudo‐second‐order kinetic model. Mathematical model equations were developed to predict the minimum operating time for the adsorption of Pb(II). Results obtained suggest that increasing temperature and decreasing percentage Pb(II) removal by the adsorbent enhanced operating time of the adsorption process. The use of two‐stage batch adsorption reduces contact time to 6.7 min from 300 min in the single‐stage batch adsorption process for the adsorption of 2.5 m³ of 500 mg L^?1 Pb(II) under the same operating conditions. CONCLUSION: Results show the potential of a tripolyphosphate‐modified kaolinite clay for the adsorption of Pb(II) from aqueous solution and the improved efficiency of a two‐stage batch adsorption process for the adsorption of Pb(II) even at increased temperature. Copyright © 2009 Society of Chemical Industry     

Hydrophobic–hydrophilic polydivinylbenzene/polyacryldiethylenetriamine interpenetrating polymer networks and its adsorption performance toward salicylic acid from aqueous solutions

Hydrophobic–hydrophilic interpenetrating polymer networks (IPNs) composed of polydivinylbenzene (PDVB) and polyacryldiethylenetriamine (PADETA) were prepared and its adsorption performance toward salicylic acid was studied from aqueous solutions. The structure of PDVB/PADETA IPNs was characterized by Fourier transform infrared spectroscopy, N₂ adsorption–desorption isotherms, weak basic exchange capacity, and swelling ratio, respectively. The results indicated that PDVB/PADETA IPNs possessed both hydrophobic and hydrophilic properties and they were much superior to the hydrophobic PDVB and the hydrophilic PADETA in adsorption of salicylic acid from aqueous solutions. The Freundlich model was more appropriate for fitting the equilibrium data than the Langmuir model and the isosteric enthalpy decreased with increment of the equilibrium uptakes. The breakthrough dynamic capacity of salicylic acid on PDVB/PADETA IPNs was 77.27 mg/mL wet resin at an initial concentration of 650.4 mg/L and a flow rate of 7.2 BV/h (bed volume, 1 BV = 10 mL) and the saturated dynamic capacity was calculated to be 93.28 mg/mL wet resin. One hundred and forty milliliter of 0.01 mol/L of sodium hydroxide (w/v) and 40% of ethanol (v/v) could regenerate the resin column completely. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2636–2643, 2014     

Kinetic and thermodynamic studies on the removal of Cu(II) ions from aqueous solutions by adsorption on modified sand

Studies on the removal of copper by adsorption on modified sand have been investigated. The adsorbent was characterized by XRD, FTIR and SEM. Removal of Cu was carried out in batch mode. The values of thermodynamic parameters namely ΔG⁰, ΔH⁰ and ΔS⁰ at 25 °C were found to be −0.230 kcal⁻¹ mol⁻¹, +4.73 kcal⁻¹ mol⁻¹ and +16.646 cal K⁻¹ mol⁻¹, respectively. The process of removal was governed by pseudo second order rate equation and value of k₂ was found to be 0.122 g mg⁻¹ min⁻¹ at 25 °C. The resultant data can serve as baseline data for designing treatment plants at industrial scale.     

Enhanced adsorption and recovery of Pb(II) from aqueous solution by alkali‐treated persimmon fallen leaves

Persimmon fallen leaves were employed to prepare a renewable and low‐cost biosorbent named as NPFL. Effects of initial pH, contact time, initial Pb(II) concentration, coexisting metal ions, and ionic strength on adsorption of Pb(II) from aqueous solution by NPFL were studied in detail. Enhanced removal capacity of NPFL toward Pb(II) was observed, and the maximum adsorption capacity was evaluated as 256 mg g^?1 by Langmuir modeling calculation. The fast adsorption process and the well‐fitted kinetics data with pseudo‐second‐order model indicated that chemisorption is the main rate‐limiting step for the adsorption process. NPFL had superior adsorption selectivity for Pb(II) from aqueous solution with coexisting metal ions. Characterization of NPFL and adsorption mechanism (electrostatic attraction, ion exchange, and chelation) were performed using XRD, SEM‐EDS, FT‐IR, XPS, and TGA. The results suggested that NPFL could be utilized as a potential candidate for the preconcentration of Pb(II) recovery and its removal in practice. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43656.     

Acrylamide‐plasma treated electrospun polystyrene nanofibrous adsorbents for cadmium and nickel ions removal from aqueous solutions

The aim of this work was to prepare novel electrospun polystyrene (PS) nanofibrous samples functionalization with acrylamide monomer (AAm) as promising nanoadsorbents by the use of nitrogen gas plasma. To investigate the performance evaluation of the samples for adsorbing cadmium (Cd²⁺) and nickel (Ni²⁺) ions, a series of tests in terms of ATR‐FTIR spectroscopy, FE‐SEM, water contact angle (WCA) measurements and atomic adsorption spectroscopy were carried out. The ATR‐FTIR results showed that nitrogen (N₂) plasma was an efficient tool because of the formation of functionalized AAm‐PS nanofibrous samples by providing amide (?NCO) and amine (?NH?) groups onto their surfaces. The WCA measurements demonstrated that the N₂ plasma‐modified samples in the presence of AAm had a lower contact angle of 42.8º than the other samples. Moreover, FE‐SEM micrpgraph images of AAm‐treated PS nanofibrous samples indicated that approperiate amount of the functional groups onto the samples surfaces were deposited. Afterwards, AAS analysis along with Langmuir and Freundlich's isotherm models revealed that a high adsorption of the ions was occurred at pH 5 in the order Cd²⁺ (10 mg g^?1) > Ni²⁺ (4.9 mg g^?1) by using the nanoadsorbents dosage 1 g L^?1 and the metal ions concentration 25 mg L^?1. In addition, the obtained results exhibited the Cd²⁺ and Ni²⁺ ions removal efficiencies (%R) were increased up to 96% and 94%, respectively with raising the nanoadsorbents dosage. Moreover, the equilibrium adsorption of the ions showed the best fitting by the Freundlich's model. Finally, the desorption of the optimized samples for regenerating them owing to the effective removal of the ions has been confirmed by applying the recyclability test. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42944.     

Regeneration of spent bleaching earth and its adsorption of copper (II) ions from aqueous solutions

This study was designed to provide a comprehensive investigation into heat and acid reactivation of spent bleaching earth (SBE) and adsorption of Cu(II) ions from aqueous solutions. Heat treatment was the master variable in SBE regeneration. Dilute acid treatment did not constitute an effective SBE reactivation protocol for this purpose. Solvent extraction of residual oil using excess methylethyl ketone followed by heating at 370 °C was, therefore, the most effective reactivation procedure. Highly adsorptive materials with > 98% removal of Cu(II) ions from solution were obtained. Thus, > 80% Cu adsorption was reversible at SBE silicate sites because of their higher proportion in the adsorbent.     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Kinetics of zirconium ions adsorption on activated charcoal from aqueous solutions

The batch kinetics of adsorption of the zirconium ions from aqueous solutions on activated charcoal has been investigated over a wide range of concentration of zirconium ions (1.0–5.0 g/l) and temperatures (10–50°C). The adsorption process of zirconium ions proceeds via two stages; the first stage is rather fast, followed by a much slower one. The Bangham equation was used to study the kinetics of the zirconium ions' adsorption on activated charcoal. It is observed that the diffusion of zirconium ions into the pores of the activated charcoal controls the kinetics of the adsorption process. Moreover, zirconium ion adsorption obeys the Freundlich and Langmuir isotherms in the concentration range studied. The adsorption equilibrium constant (k_c) values for zirconium ions adsorption on activated charcoal have also been calculated at different temperatures. Various thermodynamic quantities, ΔG, ΔH, and ΔS were computed from k_c values. The results showed that the adsorption of zirconium ions on activated charcoal is an endothermic process.     

Polymer‐grafted banana (Musa paradisiaca) stalk as an adsorbent for the removal of lead(II) and cadmium(II) ions from aqueous solutions: kinetic and equilibrium studies

This study examined the effectiveness of a new adsorbent prepared from banana (Musa paradisiaca) stalk, one of the abundantly available lignocellulosic agrowastes, in removing Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent (PGBS‐COOH) having a carboxylate functional group at its chain end was synthesized by graft copolymerization of acrylamide on to banana stalk, followed by functionalization. Batch adsorption experiments were carried out as a function of solution pH, ionic strength, contact time, metal concentration, adsorbent dose and temperature. A pH range of 5.5–8.0 was found to be effective for the maximum removal for both Pb(II) and Cd(II). Metal uptake was found to decrease with increase in ionic strength due to the expansion of the diffuse double layer and, more importantly, the formation of some chloro complexes (since NaCl was used in the adjustment of ionic strength), which do not appear to be adsorbed to the same extent as cations [M²⁺ and M(OH)⁺]. The kinetic studies showed that an equilibrium time of 3 h was needed for the adsorption of Pb(II) and Cd(II) on PGBS‐COOH and adsorption processes followed a pseudo‐second‐order equation. The Langmuir isotherm model fitted the experimental equilibrium data well. The maximum sorption capacity for Pb(II) and Cd(II) ions was 185.34 and 65.88 mg g^?1, respectively, at 30 °C. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were derived to predict the nature of adsorption. The isosteric heat of adsorption was found to be independent of surface coverage. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC‐50, for comparison. Synthetic wastewater samples were treated with the adsorbent to demonstrate its efficiency in removing Pb(II) and Cd(II) ions from industrial wastewaters. Acid regeneration was tried for several cycles with a view to recovering the sorbed metal ions and also restoring the sorbent to its original state. Copyright © 2005 Society of Chemical Industry     

Polarographic determination of the competitive adsorption of U(VI), Pb(II), and Cd(II) ions on poly(N‐vinyl‐2‐pyrrolidone‐g‐citric acid) hydrogels

Poly(N‐vinyl‐2‐pyrrolidone‐g‐citric acid) [P(VP‐g‐CA)] hydrogels were prepared for the removal of U(VI), Pb(II), and Cd(II) from aqueous solutions containing different amounts of these ions (2.5–10 mg/L). Different pHs (1–13), temperatures (20–40°C), and ionic strengths (0.5M) were also tried for the adsorption behavior of these ions. The competitive adsorption values of U(VI), Pb(II), and Cd(II) ions on pure poly(N‐vinyl‐2‐pyrrolidone) were low [0.71–2.03 mg of U(VI)/g of dry gel, 0.15–1.58 mg of Pb(II)/g of dry gel, and 0.10–0.68 mg of Cd(II)/g of dry gel]. The incorporation of citric acid significantly increased the adsorption of these ions [0.67–2.12 mg of U(VI)/g of dry gel, 0.44–1.88 mg of Pb(II)/g of dry gel, and 0.04–0.92 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐1; 0.71–2.36 mg of U(VI)/g of dry gel, 0.60–2.16 mg of Pb(II)/g of dry gel, and 0.14–0.80 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐2; and 0.79–2.47 mg of U(VI)/g of dry gel, 0.70–2.30 mg of Pb(II)/g of dry gel, and 0.20–0.86 mg of Cd(II)/g of dry gel for P(VP‐g‐CA)‐3]. The observed affinity order of adsorption was U(VI) > Pb(II) > Cd(II) for competitive conditions. The optimal pH range for the removal of these ions was 5–9. Competitive adsorption studies showed that other stimuli, such as the temperature and ionic strength of the solution, also influenced the U(VI), Pb(II), and Cd(II) adsorption capacity of P(VP‐g‐CA) hydrogels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2019–2024, 2003     

Removal of copper ions from aqueous solutions by adsorption onto wheat straw cellulose‐based polymeric composites

The wheat straw cellulose‐based hydrogels were synthesized by graft copolymerization followed by semi‐interpenetrating network technology. The prepared hydrogels were characterized through various methods including Fourier transform infrared spectra, scanning electron microscope, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. Batch adsorption experiments were carried out to investigate the adsorption performances of hydrogels toward Cu(II) ions. The results suggested that the introduction of semi‐interpenetrating network polymers, sodium alginate and poly(vinyl alcohol), could greatly enhance the adsorption property of hydrogels. And the wheat straw cellulose‐g‐poly(potassium acrylate)/sodium alginate hydrogel showed a highest Cu(II) ions adsorption capacity of 130 mg/g. The equilibrium isotherm and adsorption kinetics were also studied. Besides, the mass transfer coefficients and the thermodynamics of Cu(II) ions adsorption were also probed. Finally, the X‐ray photoelectron spectroscopy analysis further demonstrated that the Cu(II) ions adsorption was mainly via complexation reaction of ? NH₂ and O‐containing groups in hydrogels. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46680.     

Investigation of zinc(II) adsorption on Cladophora crispata in a two‐staged reactor

In this study, the adsorption of zinc(II) ions on Cladophora crispata, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration in order to determine the optimum adsorption conditions. Optimum initial pH values for zinc(II) ions were found to be 5.0 at optimum temperature, 25 °C. The initial adsorption rates increased with increasing initial zinc(II) ion concentration up to 100 mgdm⁻³. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. Then, the adsorption of zinc(II) ions to C crispata was investigated in a two‐staged mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given quantity of dried algae (X_o)/volume of solution containing heavy metal ion (V_o) ratio were calculated by using Freundlich and Langmuir isotherm constants. It was observed that the experimental biosorption equilibrium data for zinc(II) ions are in good agreement with those calculated using both Freundlich and Langmuir models. The adsorbed zinc(II) ion concentration increased with increasing X_o/V_o ratios while the adsorbed metal quantities per unit mass of dried algae decreased. © 2000 Society of Chemical Industry     

Preparation and characterization of chitosan/Cu(II) affinity membrane for urea adsorption

We used silica particles as a porogen to prepare macroporous chitosan membranes and subsequently prepared macroporous chitosan/Cu(II) affinity membranes for urea adsorption. The morphology, porosity, Cu(II) adsorption capacity, and swelling ratio of the macroporous membrane were measured. SEM photographs show the pores in the membrane dispersed uniformly, a feature that didn't change much after the adsorption of Cu(II). The porosity of the membrane had a maximum value when the silica/chitosan ratio was about 12. The Cu(II) adsorption capacity in the membrane leveled off when the initial concentration of CuSO₄ solution exceeded 5 × 10^?2 mol/L. The macroporous chitosan/Cu(II) affinity membrane was successfully used for urea adsorption. The maximum urea adsorption capacity was 78.8 mg/g membrane, which indicates that the membrane has a great potential for hemodialysis for urea removal. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1108–1112, 2003     

Intraparticle diffusion of cadmium and zinc ions during adsorption from aqueous solution on activated carbon

The adsorption isotherms of cadmium(II) and zinc(II) onto activated carbons were obtained in a batch adsorber. The concentration decay data were obtained in a rotating basket adsorber and were interpreted by a mathematical model, which takes into account the adsorption rate, external mass transport and intraparticle diffusion. The results showed that the overall rate of adsorption of Cd(II) and Zn(II) was mainly controlled by the intraparticle diffusion which was solely due to pore volume diffusion. The contribution of the external mass transport resistance was negligible. The effective pore volume diffusivities of Cd(II) and Zn(II) were predicted reasonably well using the ionic diffusivity of the metal and the void fraction and tortuosity of activated carbon. Copyright © 2005 Society of Chemical Industry     

Fe(II) adsorption onto natural polymers derived from low‐grade lignites

In comparison with conventional chemical treatment methods for Fe(II) ions, adsorption and ion exchange are considered more easily applicable and economical, depending on the material used. Polymeric materials are the examples used in these commonly applied removal processes. In this study, the adsorption of Fe(II) ions from aqueous solutions onto two different natural polymers, insoluble humic acids (IHAs) extracted from low‐grade lignites from Beysehir and Ermenek (in the central Anatolia region, Konya, Turkey), was investigated. The IHAs were synthesized through a series of acid–base reactions, and the obtained precipitates were chemically stable and had about 40% humic matter together with functional carboxyl and hydroxyl groups. The effects of the time and initial metal concentration on the effectiveness of the IHAs for Fe(II) adsorption were determined through batch experiments; the adsorption isotherms and capacities were calculated. The IHAs were effective, with capacities of 59 mg/g for the Beysehir IHA and 57 mg/g for the Ermenek IHA, for Fe removal under neutral pH conditions. The adsorption followed mainly a Freundlich isotherm for both IHAs, and the calculated adsorption rates were 0.86 for the Beysehir IHA and 0.81 for the Ermenek IHA. This indicated that the effectiveness of the Beysehir IHA was slightly higher than that of the Ermenek IHA. The results confirmed the real possibility of the practical application of IHAs for the separation of Fe(II) in aqueous systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Cr (VI) adsorption from aqueous solutions on grafted chitosan

Chitosan was grafted on the surface of a cotton gauze (20, 50, and 100 mg chitosan g⁻¹ cotton) to improve its stability in aqueous solutions. The adsorption of hexavalent chromium ions from water on the grafted chitosan was evaluated to determine, by means of linear and nonlinear models, the kinetic and isotherm adsorption of the process. The kinetics of pseudo second-order, pseudo first-order, and adsorption isotherms type II were obtained, that is, a monolayer adsorption on nonporous adsorbents with physical adsorption was present. The most probable energy of adsorption corresponded to a physisorption with hydrogen bond interactions between chromium ions and ammonium groups. Moreover, three different cross-sectional areas of hexavalent chromium ions were calculated and used to estimate the specific surface area employed by active sites to adsorb metal ions in terms of chitosan or cotton mass. Finally, the percentage of the area occupied by chromium ions on the surface was estimated by dividing the resulting specific surface area in terms of cotton mass by the specific surface area of cotton reported in literature. As a result, it was determined that the occupied area is between 6% (for 20 mg chitosan g⁻¹ cotton)-24% (for 100 mg chitosan g⁻¹ cotton) from the total area of cotton.     

Heterogeneous synthesis of chelating resin organophosphonic acid‐functionalized silica gel and its adsorption property of heavy metal ions from fuel ethanol solutions

In this study, chelating resin silica gel chemically modified by poly(triethylenetetramine bis(methylenephosphonic acid)) (denoted as SG‐Cl‐T‐P) was successfully developed by heterogeneous synthesis method and used for adsorptive removal of heavy metal ions from fuel ethanol solutions, and the relevant modified organic group was calculated by DFT method at the B3LYP/6‐31 + G(d) level. SG‐Cl‐T‐P was characterized by Fourier transform infrared spectrometer, scanning electron microscope, energy dispersive X‐ray analysis system, porous analysis, etc. SG‐Cl‐T‐P has been used to investigate the adsorption of Hg(II),Cu(II), Mn(II), Co(II), Zn(II), Ni(II), Fe(III), and Cd(II) metal ions from ethanol solutions. The research results revealed that it has the better adsorption capacity for Hg(II) and Cd(II). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012