Radiation Synthesis and Characterization of Poly (vinyl alcohol)/acrylamide/TiO2/SiO2 Nanocomposite for Removal of Metal Ion and Dye from Wastewater

PVA-co-AAm/TiO₂/SiO₂ nanocomposites adsorbents synthesized by γ-irradiation copolymerization of polyvinyl alcohol (PVA) and acrylamide (AAm) incorporated TiO₂/SiO₂ nanopowders, aiming to enhance the removal of basic blue 3 dye (BB3) and Cu (II) ions from aqueous solutions. Properties of nanocomposites were analyzed by different techniques. FTIR results showed successful incorporation of nanoparticles and copolymerization of PVA and AAM. SEM/EDS confirm the peaks belonging to C, O, Si, and Ti. TEM investigation illustrated that TiO₂/SiO₂ nanoparticles were well dispersion, uniform, and homogeneous shape of particle size of 60–70 nm. XRD data specified characteristic diffraction peaks of TiO₂ and the calculated crystalline size was 43 nm. Adsorption results confirm that PVA-co-AAm/TiO₂/SiO₂ nanocomposites provide better adsorption capacities of both BB3 and Cu (II) was three-folds rather than PVA-co-AAm-30. The nanocomposite prepared at 30 kGy (PVA-co-AAm/TiO₂/SiO₂-30) showed high swelling, gelation, and highest adsorption capacity and it was selected as the best adsorbent for batch experiments. The optimum adsorption was achieved using 0.4 g PVA-co-AAm/TiO₂/SiO₂-30 adsorbent dosage. The adsorption capacity of BB3 and Cu (II) was 140.9 and 190.3 mg/g with a removal efficiency of 93.5 and 95.2% after 7 h and 6 h, pH 11 and pH 6, and initial concentration of 150 and 200 mg/L, respectively. The adsorption of BB3 or Cu (II) was endothermic and spontaneous, well described by the pseudo-second-order adsorption kinetic and fit Langmuir isotherm. The results revealed that the as-synthesized PVA-co-AAm/TiO₂/SiO₂ nanocomposites could be employed as effective adsorbents for the adsorption of BB3 and Cu (II) ions from wastewater with high adsorption capacity and recovery.

     

Study on the effect of EDTA on the photocatalytic reduction of mercury onto nanocrystalline titania using quartz crystal microbalance and differential pulse voltammetry

In-situ technique quartz crystal microbalance (QCM), differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were employed to investigate the effect of disodium ethylenediamine tetraacetate (EDTA) on photocatalytic reduction of mercury onto nanocrystalline titania (TiO₂). Effects of EDTA on adsorption of Hg(II) and its photocatalytic reduction process at the surface of TiO₂ in different pH solutions had been studied in detail. From the in-situ response to the adsorption of Hg(II) onto TiO₂, the reaction rate and saturation adsorption amount were estimated about 4.71 × 10⁻⁶ g mol⁻¹ min⁻¹ and 46.36 (mg Hg(II)/g TiO₂) via the model of pseudo-second-order kinetics respectively. The photocatalytic reduction of Hg at the surface of TiO₂ was influenced by pH and the mole ratio of Hg(II) to EDTA. When the ratio of Hg(II) to EDTA 1:1, it was most favorable for the photocatalytic reduction of mercury. In addition, the effects of HCOOH and EDTA on the reduction of Hg(II) was comparatively investigated and the mechanism on the photocatlytic reduction of mercury was illustrated. Therefore, it could be concluded that QCM, DPV and CV were effective methods for the investigation of photocatalytic reduction of complex heavy metal ions onto the surface of nanocrystalline TiO₂.     

Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

Mechanism of copper(II) adsorption by polyvinyl polyacrylate

The mechanism of copper adsorption by polyvinyl polyacrylate (PVPA) was examined using ESR and magnetic measurements. The copper adsorption by PVPA obeyed Langmuir adsorption isotherm with the maximum adsorption amounts of 4.17 mmol g^?1 adsorbent, being larger than those of uranium adsorption. Though copper in the solution was completely adsorbed by the resin above pH 4, the ESR intensity was remained low level and only increased above pH 8. The ESR spectrum of Cu(II) ion in PVPA are axial type with tetragonally distorted octahedral symmetry, having parameters of g_⊥ = 2.361, g_? = 2.057, |A_⊥| = 14.0 m cm^?1 (pH 5), and g_⊥ = 2.329, g_? = 2.058, |A_⊥| = 16.2 m cm^?1, |A_?| = 2.7 m cm^?1 (pH 9). The absorption peaks originated from Cu(II)–Cu(II) dimer was also observed (pH 5). The paramagnetic susceptibility of PVPA adsorbed Cu(II) ion at pH 5 explained by the dimer model with |J| = 220 K. These results suggested that most of copper was adsorbed and formed dimer in PVPA, being similar to that in Cu(II)‐acetate monohydrate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5372–5377, 2006     

Adsorption of Cu(II) from Aqueous Solution by Porous Mn3[Co(CN)6]2 · nH2O Nanospheres

Prussian blue analogue of porous Mn₃[Co(CN)₆]₂ · nH₂O nanospheres with a large surface area were prepared by simple mixing K₃[Co(CN)₆]₂ and manganous nitrate solution at room temperature. The morphology and structure of the prepared products were characterized by XRD, FE-SEM, TEM, and BET. The results indicated that the product was composed of nanospheres with the diameter of ～250 nm, which was of porous structure with the pore diameter in the 2.5–4 nm range. The adsorption behavior of Cu(II) ions from aqueous solution onto porous nanospheres was investigated as a function of parameters, such as the equilibrium time, the pH, the initial concentration, and the temperature. A maximum adsorption capacity of 140.85 mg g^?1 of Cu(II) was achieved. Due to the simple synthetic method and its high adsorption capacity, the porous nanospheres had the potential to be utilized as an effective adsorbent for Cu(II) removal.     

Hydrothermal synthesis of multiwalled TiO2 nanotubes and its photocatalytic activities for Orange II removal

The solvothermal synthesis of multiwalled TiO₂ nanotubes (MWTNTs) with the reaction of titanium dioxide (TiO₂) nanoparticles and sodium hydroxide aqueous solution at moderate temperature is presented. The kinetic and isotherm studies were investigated for Orange II removal mechanism. MWTNTs were prepared in length 70–200 nm, average diameter 4–10 nm, and inter-shell spacing 0.78 nm. Different characterizations were performed to confirm anatase and mesoporous structure of MWTNTs. An improvement in properties as compared to commercial TiO₂ was observed; specific surface area 244.81 m²/g and band gap 3.0 eV. An excellent photocatalytic activity for Orange II removal was exhibited using synthesized MWTNTs.     

Enhanced adsorption of two azo dyes produced by carbon modification of TiO2

The process of removal of two azo dyes (Reactive Red 198 and Direct Green 99) from water was investigated. The adsorption of azo dyes onto surfaces of pristine TiO₂, P25 and carbon-modified TiO₂ (at 120 °C for 24 h) was presented. The Freundlich model of adsorption isotherm was found for pristine TiO₂ and TiO₂-P25. Modification of TiO₂ by carbon lead to the change from the Freundlich model to the Langmuir model of adsorption isotherm. For the TiO₂-C photocatalyst the adsorption capacity was determined, which was almost two times higher for Direct Green 99 than Reactive Red 198 dyes. As a result we observed the increase of photocatalytic activity of carbon-modified TiO₂ photocatalyst.     

Valine-Coated Magnetic Nanoparticles: Synthesis,Characterization, and Application in Removal of Cd(II) Ions from Aqueous Solution

A novel Valine coated magnetic nano-particles (MNPs-Val) has been synthesized for the removal of Cd(II) ions from aqueous solution. The MNPs-Val were developed by electrostatic attraction of valine (C₅H₁₁NO₂) on the bare surface of Fe₃O₄ nanoparticles and characterized by using FT-IR, XRD, SEM, and TEM analysis. The morphology and average particles size 15-27 nm of MNPs-Val were analyzed by SEM and TEM. The coated MNPs were applied for adsorptive removal of Cd(II) ions from aqueous solutions. Factors affecting the adsorption of Cd(II) ions on the MNPs-Val surface such as the pH, temperature, adsorbent dosage, and contact time were investigated which have significant effect on the metal ion removal. The Cd(II) ions adsorption equilibrium on the MNPs-Val could be achieved in 35 min at the optimized pH 5 and follow the pseudo-second order kinetics model. The experimental data for the adsorption of Cd(II) was followed by the Langmuir isotherm and the maximum adsorption capacity was obtained at 0.2 g L^?1 adsorbent dose at 308 K.     

The adsorption of Cu(II) ion from aqueous solution upon acrylic acid grafted poly(ethylene terephthalate) fibers

This study is concerned with the investigation of the adsorption properties of acrylic acid grafted poly(ethylene terephthalate) fibers by the use of Cu(II) ions in aqueous solutions. Influence of pH, graft yield, contact time, concentration of the ion, and reaction temperature on the amount of ion adsorbed upon reactive fiber were investigated. The time in which the adsorption reached to the equilibrium value was determined as 1 h. The adsorption isotherm of Cu(II) ion was found to be a Langmuir type and the heat of adsorption was calculated as ?10.1 kJ mol^?1. It was observed that the adsorbed Cu(II) ion upon acrylic acid grafted poly(ethylene terephthalate) fibers could be recovered in acidic media. The fiber could also readsorb Cu(II) ions without losing its activity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1216–1220, 2003     

Evaluating Cu(II) Removal From Aqueous Solutions with Response Surface Methodology by Using Novel Synthesized CaCO3 Nanoparticles Prepared in a Colloidal Gas Aphron System

Removal of heavy metals from water and wastewaters has recently gained a great deal of attention due to their serious environmental problems. In this study, novel synthesized calcium carbonate nanoparticles, prepared in a colloidal gas aphron (CGA) system, were used as adsorbents for the removal of Cu²⁺ ions from aqueous solutions under different conditions. A developed pseudo-second-order (PSO) model well described the adsorption kinetics of the process. Langmuir and Freundlich adsorption isotherms have been examined and the maximum adsorption capacity from the Langmuir isotherm equation was found to be 666.67?mg Cu/g adsorbent. The effects of temperature, Cu²⁺ initial concentration, and CaCO₃ dosage on the removal capacity were also investigated using the three-level Box–Behnken experimental design method. The response surface modeling results demonstrated that under certain experimental conditions (i.e., T?=?26°C, [Cu²⁺]?=?200?mg/L, and [CaCO₃]?=?0.5?g/L), maximum removal capacity value (393.52?mg/g) was achieved.     

Synthesis and application of nanocomposite Fe3O4@SiO2@CTAB–SiO2 as a novel adsorbent for removal of cyclophosphamide from water samples

ABSTRACT

We present a way of synthesizing nanocomposite Fe₃O₄@SiO₂@CTAB–SiO₂ by employing simple sol–gel technique with selective etching for extreme selectivity adsorption of cyclophosphamide (CP). The transmission electron microscopy (TEM); scanning electron microscopy (SEM); X-ray diffraction (XRD); Fourier transform infrared (FT-IR); vibrating sample magnetometer (VSM); pH_PZC; and Brunauer, Emmett and Teller (BET) techniques were used for nanocomposite characterization. These nanoparticles have an S_BET of 157.8 m² g^?1 and a high saturation magnetization of 67.5 emu g^?1. First, the adsorption system was examined as a function of contact time under various initial CP contents, ionic strength, initial solution pH, adsorbent dose and temperature in batch test. The optimum dose, pH and contact time were obtained to be 0.01 g, 7.0 and 30 min, respectively. Ultimately, experimental isotherm and kinetics data of adsorption of CP onto nanocomposite Fe₃O₄@SiO₂@CTAB–SiO₂ were fitted to classical models. Additionally, it was found that the maximum adsorption process capacity of CP on adsorbent was 342.8 mg g^?1.     

TiO2/Na-HZSM-5 nano-composite photocatalyst: Reversible adsorption by acid sites promotes photocatalytic decomposition of methyl orange

TiO₂/Na-HZSM-5 nano-composite photocatalysts were prepared by dispersing TiO₂ onto the external surface of Na⁺-modified nano-ZSM-5 zeolite using a sol–gel process. Samples were characterized by XRF, XPS, HRTEM, XRD, DRUV–vis, NH₃-TPD, FT-IR, and the adsorption and photodegradation of methyl orange (MO) in aqueous solution. Results show the modification of support by Na⁺ does not affect the loading, dispersion and structure of loaded TiO₂, but reduces the acidity of the nano-zeolitic support by preferentially eliminating stronger acid sites. The MO adsorption mainly takes place on the external surface of the supports. The strong and medium strong acid sites of the supports are the adsorption sites. MO molecules adsorbed by strong acid sites are difficult to desorb, whereas the adsorption of MO by medium strong acid sites is reversible. Generally, the MO photodegradation activity of TiO₂/Na-HZSM-5 nano-composites is better than that of bare TiO₂. However, it changes remarkably with the Na⁺ content of the supports, giving the maximum value at 1.1 wt.% Na⁺ when the MO adsorption by the support is almost completely reversible. The enhancement of the photodegradation activity of TiO₂/Na-HZSM-5 nano-composites is attributed to the reversible adsorption of MO by the medium strong acid sites on the nano-zeolitic supports.     

Comparative CO2 Adsorption Analysis in Pure and Amine-Modified Composite Membranes

In this study, the CO₂ adsorption analysis in cellulose acetate–TiO₂- and cellulose acetate–3-aminopropyl-trimethoxysilane TiO₂-blended membranes was performed. The membranes were also characterized using scanning electron microscopy and Fourier transform infrared analysis techniques. The adsorption results indicated that 120 and 90°C were considered as optimized temperatures for regeneration of cellulose acetate–TiO₂ and cellulose acetate–3-aminopropyl-trimethoxysilane-modified TiO₂ membranes. The testing results revealed that adsorption capacity reached maximum at 3.0 bars. Validation of experimental results was performed by pseudo-first-order, second-order and intraparticle diffusion models. The correlation factor R² represented that the second-order model was fitted well with the experimental data. The intraparticle diffusion model represented that adsorption is not a single-step process.     

Investigation of α‐iron oxide‐coated polymeric nanocomposites capacity for efficient heavy metal removal from aqueous solution

In the present study, PS@α‐Fe₂O₃ nanocomposites were prepared by chemical microemulsion polymerization approach and the ability of magnetic beads to remove Cu(II) ions from aqueous solutions in a batch media was investigated. Various physico‐chemical parameters such as pH, initial metal ion concentration, temperature, and equilibrium contact time were also studied. Adsorption mechanism of Cu²⁺ ions onto magnetic polymeric adsorbents has been investigated using Langmuir, Freundlich, Sips and Redlich–Petersen isotherms. The results demonstrated that the PS@α‐Fe₂O₃ nanocomposite is an effective adsorbent for Cu²⁺ ions removal. The Sips adsorption isotherm model (R² > 0.99) was more in consistence with the adsorption isotherm data of Cu(II) ions compared to other models and the maximum adsorbed amount of copper was 34.25 mg/g. The adsorption kinetics well fitted to a pseudo second‐order kinetic model. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated from the temperature dependent sorption isotherms, and the results suggested that copper adsorption was a spontaneous and exothermic process. POLYM. ENG. SCI., 55:2735–2742, 2015. © 2015 Society of Plastics Engineers     

Removal of Ni(II), Cd(II), and Pb(II) from a ternary aqueous solution by amino functionalized mesoporous and nano mesoporous silica

In the present study, the application for the removal of Ni(II), Cd(II) and Pb(II) ions from aqueous solution by using mesoporous silica materials, namely, MCM-41, nanoparticle of MCM-41, NH₂-MCM-41 (amino functionalized MCM-41) and nano NH₂-MCM-41 was investigated. Suitable adsorbents preparation techniques were developed in the laboratory. The effects of the solution pH, metal ion concentrations, adsorbent dosages, and contact time were studied. It was found that NH₂-MCM-41 showed the highest uptake for metal ions in aqueous solution. The results indicated that the adsorption of Ni(II), Cd(II) and Pb(II) ions on the surface of the adsorbent was increased with increasing solution pH. The experimental data were analyzed using the Langmuir and Freundlich equations. Correlation coefficients were determined by analyzing each isotherm. It was found that the Langmuir equation showed better correlation with the experimental data than the Freundlich. According to the parameters of the Langmuir isotherm, the maximum adsorption capacity of NH₂-MCM-41 for Ni(II), Cd(II) and Pb(II) was found to be 12.36, 18.25 and 57.74 mg/g, respectively. The kinetic data of adsorption reactions and the evaluation of adsorption equilibrium parameters were described by pseudo-first-order and pseudo-second-order equations. The synthesized solid sorbents were characterized by Fourier transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen sorption measurements.     

Synthesis,Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ～ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO₃ at a flow rate of 0.2 mL min^?1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO₃-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO₃ or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.     

Adsorption of nickel onto Bacillus cereus M116: A mechanistic approach

Adsorption characteristics of nickel on Bacillus cereus M¹₁₆ biomass have been studied under varied environmental conditions to explore the potentiality of the biomass for controlling water pollution due to nickel. The optimized parameters for adsorption process are as follows: pH: 7.0, temperature: 40°C, biomass dosage: 2 g L^–1. The process is best fitted to Redlich–Peterson isotherm model and follows pseudo-second order rate model. The combination of zeta potential measurement, SEM – EDXA, XRD, XPS, FTIR, TGA, and DSC studies allow a more comprehensive characterization of biomass to understand the mechanisms involved in nickel (II) adsorption in aqueous system.     

Integration of Photocatalysis and Microfiltration in Removing Effluent Organic Matter from Treated Sewage Effluent

An integration of photocatalysis with low-pressure submerged membrane has attracted growing interest for its synergic advantages in water and wastewater treatment. In this study, the adsorption and photocatalytic oxidation of organic compounds by UV light responsive titanium dioxide (TiO₂) were investigated. First, the adsorption behavior of the TiO₂ was examined by the adsorption isotherm and kinetics experiments. The photocatalytic reactivity of the catalysts was then compared at different operating conditions. The results indicate that the Freundlich model described well the adsorption capacity of both materials. The photocatalytic kinetics showed that the highest removal of effluent organic matter (EfOM) was achieved at an optimum concentration of 1.0 g/L of TiO₂. In addition, it was found that the pre-photosensitization with titanium dioxide/ultra-voilet radiation (TiO₂/UV) could effectively reduce membrane fouling and enhance the permeate flux of the submerged membrane reactor when it was used as a post-treatment. An increase of 10% in organic removal efficiency was achieved by the posttreatment of membrane filtration. The sustainable flux of the membrane reactor increased from 25 up to 40 L/m²·h when the pretreatment of photocatalysis was used.     

Synthesis,characterization, and application of yeast-based magnetic bionanocomposite for the removal of Cu(II) from water

Abstract

Due to the amount of yeast residues generated by the industries and their high capacity as biosorbent, this work proposes the use of yeast biomass in natura (YB) or modified with ferromagnetic nanoparticles (Fe₃O₄) (YB-MNP) for Cu(II) removal from water. Synthesized YB-MNP, YB, and magnetite alone (MNP) were characterized by FTIR, XRD, and SEM. It was observed the efficient impregnation of magnetite on the surface of the biomass. Copper sorption was evaluated in batch tests using 100?mg/L of Cu(II) solution at pH 5.5, and the supernatant was analyzed by FAAS for Cu determination. Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models were applied to fit the experimental data. A favorable sorption process was observed for all the materials, mainly for the D–R model adjusted to the bionanocomposite data (YB-MNP), with r² = 0.9950 and a low error (χ² = 0.0427) associated to the model. Theoretical and experimentally Cu(II) sorption capacities were fairly similar, 8.6?±?0.1 and 8.3?±?0.2?mg/g, respectively.     

Synthesis of Octa(maleimidophenyl) silsesquioxane–SiO2/TiO2 Hybrid Nanocomposites: Adsorption Behavior for the Removal of an Organic Methylene Blue Dye and Antimicrobial Activity against Pathogens

In this study, a sol–gel process was used to prepare hybrid nanocomposite consisting of octa(maleimidophenyl) silsesquioxane-silica/titania (maleimide–POSS (polyhedral oligomeric silsesquioxanes)–SiO₂/TiO₂) to use in methylene blue (MB) adsorption and as an antibacterial agent. The structure, surface, and morphological characteristics were confirmed through Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The optical and thermal stabilities were studied by conducting UV–visible and thermogravimetric analysis–differential scanning electron calorimetry analysis. The experimental results showed a maximum dye adsorption capacity of 92% achieved using 0.5?g of hybrid nanocomposite after 2.5?h at pH 9. We also investigated the effect that the adsorbent dosage, pH, and contact time had on the removal efficiency of the MB dye in aqueous solution. The recycling experiment showed a good adsorption capacity of the MB dye, even after five repeated cycles. Furthermore, the hybrid nanocomposite was tested against pathogenic bacteria, such as Bacillus cereus, Lactobacillus, Escherichia coli, and Pseudomonas aeruginosa. The nanocomposite was observed to be highly sensitive to E. coli, B. cereus, and P. aeruginosa, as confirmed by the size of the zone inhibition.