Removal of Copper and Lead from Aqueous Solution by Adsorption onto Cross-Linked Chitosan/Montmorillonite Nanocomposites in the Presence of Hydroxyl–Aluminum Oligomeric Cations: Equilibrium,Kinetic, and Thermodynamic Studies

Adsorption removal of Cu (II) and Pb (II) on cross-linked chitosan/Al₁₃-pillared montmorillonite (CCPM) was examined in solutions. The chitosan dosage was drastically reduced in the new nanocomposite, which is made from the treated clay (Al₁₃-pillared montmorillonite). Several important parameters that influenced the adsorption of Cu (II) and Pb (II) ions, such as cross-linked chitosan-to-clay ratio, pH, temperature, initial concentration, dosage, and contact time effect, were systematically investigated. Result showed that in the nanocomposite with cross-linked chitosan-to-clay ratio of 0.45:1, the maximum removal efficiencies of Cu (II) [pH 6.5, dosage 10 g/L, initial Cu (II) concentration 100 mg/L, contact time 2 h, 298 K] and Pb (II) [pH 6.0, dosage 5 g/L, initial Pb (II) concentration 100 mg/L, contact time 2 h, 298 K] were 96.0% and 99.5%, respectively. Kinetic and isotherm studies have indicated that the adsorption process of Cu (II) or Pb (II) nanocomposites was better fitted by the pseudo-second-order equation and the Freundlich equation, with chemical adsorptions as the rate-limiting step. The metal–ion affinity to the functional groups of CCPM followed the order Pb (II) > Cu (II). The thermodynamic parameters ΔH and ΔS values showed that the sorption process of Cu (II) or Pb (II) was spontaneous (ΔG < 0), was endothermic (ΔH < 0), and had decreased entropy (ΔS < 0). HNO₃ (0.1 M) could be a good desorbent in the recovery of metal ions after adsorption and regeneration of the adsorbent.     

Adsorption of Cr(VI) on Cross‐Linked Chitosan Beads

Abstract

A possibility of Cr(VI) removal by the adsorption method is discussed in the paper. An adsorbent were hydrogel chitosan beads are produced by the phase inversion method (by changing pH). The possibility of removing Cr(VI) ions by both pure chitosan hydrogel and its chelate compounds (chitosan cross‐linked with Cu(II) and Ag(I) ions) was investigated. The adsorption proceeded from the solutions of potassium dichromate and ammonium dichromate (NH₄)₂Cr₂O₇ and K₂Cr₂O₇. The process rates and adsorption isotherms were determined and described by relevant equations. The process rate was described by the pseudo‐ and second‐order equations, and adsorption equilibria by the Langmuir equations. A slight advantageous change in adsorption properties of chitosan beads was revealed after cross‐linking (for chromium concentration up to 10 g/dm³). A maximum adsorption was 1.1 g_Cr/g chitosan. Results of the studies show that chitosan hydrogel proves useful in the removal of Cr(VI) ions, additionally, cross‐linking with Cu(II) and Ag(I) ions has an advantageous effect in the case of low‐concentrated solutions.     

Adsorption of 2,4-dichlorophenol from Aqueous Solution by a New Low-Cost Adsorbent – Activated Bamboo Charcoal

Adsorption experiments were conducted to study the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solution by a new low-cost adsorbent-activated bamboo charcoal. The results showed that acidic pH was favorable for the adsorption and removal of 2,4-DCP. Higher initial 2,4-DCP concentrations led to higher adsorption capacity. Most of the adsorption of 2,4-DCP occurred within the first 5 min, and about 90% of 2,4-DCP were removed from solution. After 5 min, the adsorption capacity increased slowly with contact time and the adsorption reached equilibrium in less than 100 min. As the adsorbent dose was increased, the removal of 2,4-DCP was increased, while the equilibrium time was slightly affected. Adsorption kinetics could be best described by the pseudo-second-order model, independent of adsorbent dosages. The adsorption behavior of 2,4-DCP onto bamboo charcoal fitted both Langmuir and Freundlich isotherms well, but followed Freundlich isotherm more precisely. This study demonstrated for the first time that activated bamboo charcoal could be used for the removal of 2,4-DCP in water treatment.     

Adsorption of γ-picoline onto acid-activated bentonite from aqueous solution

The adsorption of γ-picoline onto acid-activated bentonite was investigated. The adsorption reached a maximum at pH = 7. Pseudo-first-order, pseudo-second-order, the Elovich equation, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order model was best applicable to describe the adsorption of γ-picoline on acid-activated bentonite. The Langmuir model provided good correlation with the experimental data. The adsorption of γ-picoline was endothermic with ∆H° = 29 J/mol.     

Adsorption of γ -UPS silane onto E-glass fibers from aqueous solutions

The deposition of γ-ureidopropyltrimethoxysilane (γ-UPS) from aqueous solutions onto plasma-treated E-glass fibers was investigated over a wide range of concentrations and pH values. At low concentrations for all the deposition pHs chosen, the silane was shown to form a surface consisting of silanols. At high concentrations, the silane was shown to form a different surface, consisting of condensed Si–O–Si groups. The ureidosilane thus produced a hydrophobic surface at high concentrations. Osterholtz and Pohl demonstrated that condensation of γ-APTES (γ-aminopropyltriethoxysilane) increased rapidly between pH 6 and 7, and that the hydrolysis was slow. This pH range corresponds to the most extensive adsorption of γ-UPS onto the E-glass surface, as judged from water contact angle, mass loss, and SEM results. The silane was deposited as patches onto the E-glass fibers. At the higher solution concentrations, an outer surface or 'skin' was formed over these patches, giving the appearance of completely siloxane polymer-coated fibers. The structure under the outer surface was open and porous.     

Adsorption Behavior of Azo Dye Eriochrome Black T from Aqueous Solution by β-Cyclodextrins/Polyurethane Foam Material

β-cyclodextrin/polyurethane (β-CD/PU) materials were prepared by foaming technique. The adsorption behavior of EBT on β-CD/PU material and the influences on the adsorption efficiency were investigated. Under the optimal experimental conditions, the maximum adsorption efficiency of EBT was 93.14%. The kinetics characteristic and thermodynamic parameters were analyzed. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm equations and the results indicated that the Langmuir isotherm showed a better fit for EBT adsorption. The experimental results suggest that the β-CD/PU foam materials have potential application for the wastewater treatment containing EBT dye.     

Peanut Shell Activated Carbon： Characterization,Surface Modification and Adsorption of Pb^2＋ from Aqueous Solution

Metal ion contamination of drinking water and waste water, especially with heavy metal ion such as lead, is a serious and ongoing problem. In this work, activated carbon prepared from peanut shell （PAC） was used for the removal of Pb^2＋ from aqueous solution. The impacts of the Pb25 adsorption capacities of the acid-modified carbons oxidized with HNO3 were also investigated. The surface functional groups of PAC were confirmed by Fourier transform infrared （FTIR） spectroscopy, X-ray photoelectron spectroscopy （XPS）, Boehm titration. The textural properties （surface area, total pore volume） were evaluated from the nitrogen adsorption isotherm at 77 K. The experimental results presented indicated that the adsorption data fitted better with the Langmuir adsorption model. A comparative study with a commercial granular activated carbon （GAC） showed that PAC was 10.3 times more efficient compared to GAC based on Langmuir maximum adsorption capacity. Further analysis results by the Langmuir equation showed that HNO3 [20% （by mass）] modified PAC has larger adsorption capacity of Pb^2＋ from aqueous solution （as much as 35.5 mg·g^-1）. The adsorption capacity enhancement ascribed to pore widening, increased cation-exchange capacity by oxygen groups, and the promoted hydrophilicity of the carbon surface.     

Aqueous Two‐Phase Partitioning of Glucose Isomerase from Actinoplanes missouriensis in the Presence of PEG‐Derivatives and its Immobilization on Chitosan Beads

Abstract

Purification of glucose isomerase by its partitioning in a PEG‐salt aqueous two‐phase system (ATPS) in the presence of PEG derivatives has been studied. Selective partitioning of the proteins was observed towards the PEG phase containing PEG‐benzoate and PEG‐palmitate, enriching glucose isomerase in the salt phase. Cross‐current extraction in 4 stages in the presence of PEG‐palmitate gave an enrichment factor of ～5 for the enzyme. After initial purification with ATPS, glucose isomerase was immobilized on cross‐linked chitosan beads. The immobilized enzyme was stable over a wider pH range (5.2–9.0) and showed an optimum pH of 6.5     

Removal of Parabens from Aqueous Solution Using β-Cyclodextrin Cross-Linked Polymer

The removal of four parabens, methyl-, ethyl-, propyl-, and benzyl-paraben, by β-cyclodextrin (β-CD) polymer from aqueous solution was studied. Different β-CD polymers were prepared by using two cross-linkers, i.e., hexamethylene diisocyanate (HMDI) and toluene-2,6-diisocyanate (TDI), with various molar ratios of cross-linker. β-CD-HMDI polymer with molar ratio of 1:7 and β-CD-TDI polymer with ratio 1:4 gave the highest adsorption of parabens among the β-CD-HMDI and β-CD-TDI series, and were subsequently used for further studies. The adsorption capacity of β-CD-HMDI is 0.0305, 0.0376, 0.1854 and 0.3026 mmol/g for methyl-, ethyl-, propyl-, and benzyl-paraben, respectively. β-CD-TDI have higher adsorption capacities compared with β-CD-HMDI, the adsorption capacity are 0.1019, 0.1286, 0.2551, and 0.3699 mmol/g methyl-, ethyl-, propyl-, and benzyl-paraben respectively. The parameters studied were adsorption capacity, water retention, and reusability. Role of both cross-linker in adsorption, hydrophobicity of polymers, and adsorption capacity of different parabens were compared and discussed. All experiments were conducted in batch adsorption technique. These polymers were applied to real samples and showed positive results.     

Effect of Narrow Oxirane Adduct Distribution on the Adsorption of Disodium Alcohol Ethoxylates Sulfosuccinate at Air–Aqueous Solution Interface

Adsorption behaviors at the air–water interface were presented for disodium alcohol ethoxylate sulfosuccinates (AESS) with narrow and broad oxirane adduct distribution. The CMC and equilibrium surface tension γ_eq of broad‐range distributed (BRD) and narrow‐range distributed (NRD) AESS₂ (with average degrees of ethoxylation of 2) were measured by the Wilhelmy plate method, while the adsorption and thermodynamic parameters were calculated. The effect of temperature and inorganic electrolyte on adsorption behaviors of these two surfactants was also investigated. The results show that NRD AESS₂ displays a lower CMC and higher γ_eq compared with BRD AESS₂. At the same time, the maximum surface excess concentration Γ_max of NRD AESS₂ was lower than that of BRD AESS₂ because of its larger steric hindrance, leading to the different adsorption and thermodynamic parameters. The adsorption of NRD AESS₂ and BRD AESS₂ was weakened with increasing temperature and enhanced in the presence of inorganic electrolyte.     

Cu–Fe Incorporated Graphene-Oxide Nanocomposite as Highly Efficient Catalyst in the Degradation of Dichlorodiphenyltrichloroethane (DDT) from Aqueous Solution

Topics in Catalysis - Fe/graphene oxide and Cu–Fe/graphene oxide nanocomposite were synthesized by the atomic implantation method to study the photocatalytic degradation of...     

Adsorption of zinc onto anionic ion-exchange resin from cyanide barren solution☆

Removal of zinc from cyanide barren solution is obligatory for its reuse in leach process. Batch experiments were carried out to evaluate the adsorption capacity of resins under different experimental conditions, including con-centration, resin amount, initial pH, contact time and temperature. More than 99%of adsorption was achieved under the optimal condition. High adsorption rates on the resin were observed at the beginning and plateau values were obtalned in 60 min. The thermodynamic parameters (free energy changeΔG, enthalpy changeΔS and entropy changeΔH) for the adsorption were evaluated. The adsorption kinetic mechanism was studied with four models. The experimental results show that the adsorption follows the Langmuir isotherm and the kinetics follows the pseudo-second-order model.     

Study on Synthesis of Chitosan Coated Cellulose to the Adsorption Properties for Au~（3＋）

合成了壳聚糖包覆纤维素（CHCC）吸附剂,其结构经FTIR、元素分析进行表征。研究了对Au3＋的吸附包括pH的影响、吸附动力学、吸附选择性和吸附热力学。结果表明：吸附容量受pH影响较大;液膜扩散是吸附的主控制步骤,pH=3时优先选择吸附Au3＋;吸附热力学符合Freundlich模型。-NH2、-OH参与对Au3＋的吸附,树脂中的-CHO可能被Au3＋氧化。     

Sorption Potential of Styrene‐Divinylbenzene Copolymer Beads for the Decontamination of Lead from Aqueous Media

Abstract

The decontamination of lead ions from aqueous media has been investigated using styrene‐divinylbenzene copolymer beads (St‐DVB) as an adsorbent. Various physico‐chemical parameters such as selection of appropriate electrolyte, contact time, amount of adsorbent, concentration of adsorbate, effect of foreign ions, and temperature were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using St‐DVB beads as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at 0.001 mol L^?1 acid solutions (HNO₃, HCl, H₂SO₄ and HClO₄) using 0.2 g of adsorbent for 4.83×10^?5 mol L^?1 lead concentration in two minutes equilibration time. The adsorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms over the lead concentration range of 1.207×10^?3 to 2.413×10^?2 mol L^?1. The characteristic Freundlich constants i.e. 1/n=0.164±0.012 and A=2.345×10^?3±4.480×10^?5 mol g^?1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.971±0.011 mmol g^?1, which suggests monolayer coverage of the surface. The sorption mean free energy from D‐R isotherm was found to be 18.26±0.75 kJ mol^?1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of lead increases with the rise in temperature. Thermodynamic parameters i.e. ΔG, ΔH, and ΔS have also been calculated for the system. The sorption process was found to be exothermic. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.     

Catalytic Combustion of Methane over Cobalt–Magnesium Oxide Solid Solution Catalysts

A series of cobalt–magnesium oxide solid solution catalysts (CoMgO) have been prepared using urea combustion methods, and characterised by X-ray diffraction (XRD) and laser Raman (LR). The catalytic activities for methane combustion have been tested in a continuous-flow microreactor. The Co content has a significant effect on the activity of the cobalt–magnesium oxide solid solution catalysts. The catalysts containing 5 and 10% Co have the lowest light-off temperature in methane combustion. In the preparation of cobalt–magnesium oxide solid solution catalysts, higher urea to metal ratio favors the formation of the catalysts with smaller crystal particles and leads to a better catalytic performance for methane combustion. Addition of lanthanum nitrate to the solution of Co and Mg nitrate depressed the formation of the cobalt–magnesium oxide solid solution and decreased the activity of the catalysts for methane combustion. The cobalt–magnesium oxide solid solution catalysts are very stable when the calcination or reaction temperature is no more than 900°C. However, the catalytic activity decreases rapidly after high temperature (>1000°C) calcination, possibly due to sintering of the catalyst and thus decrease of the surface area.     

The Effect of Cobalt on the Degradation of Methyl β-D-Gluco-Pyranoside by Oxygen in Aqueous Sodium Hydroxide Solution

Abstract

The effect of Co(II) (0 to 0.25 mW CoSO₄) on the degradation of methyl β-D-glucopyranoside (MBG) at 120°C in 1.25M NaOH with 0.68 MPa oxygen pressure was studied. When the Co(II) was increased from 0.00 to 0.01 to 0.05 mM the MBG half-life decreased from 12 to 6 to 1.5 hours, reflecting approximately a 0.5 order kinetic dependence on cobalt. An oxidation-reduction cycle between Co(II) and Co(III) involving oxidation of Co(II) by oxygen and oxidation of the glucoside by Co(III), hydroxyl radical, or superoxide is proposed for the degradation. At the 0.25 mM Co(II) addition level highly adsorptive Co(OH)₂ formed prior to reaction initiation with oxygen and removed otherwise soluble cobalt from solution. This resulted in lower rates of MBG degradation than obtained even at 0.01 mM Co(II) addition. However, Co(II) solubility could be enhanced if silicate anions or polyols (including MBG) were added to the alklaine medium prior to the Co(II) addition. In reactions initially containing 0.25 mM soluble Co(II), an adsorptive precipitate, presumably CoO(OH), gradually formed after reaction initiation with oxygen. Precipitation of the Co(III) solid coincided with a rapid decline in the rate of MBG degradation. Cobalt had little effect on the products of MBG degradation.     

Extraction of 4‐Hydroxycinnamic Acid from Aqueous Solution by Emulsion Liquid Membranes

Abstract

This work reports a study of 4‐hydroxycinnamic acid extraction by emulsion liquid membranes. The effect of the presence of additives in the membrane phase on solute permeation was tested. The membrane with 2 wt.% of isodecanol, 2 wt.% of ECA4360J, and Shellsol T as diluent was selected to examine the permeation of 4‐hydroxycinnamic acid. The modeling of solute extraction was done by taking into account the mass transfer in the external phase and globule, and the reaction between the diffusing component and the stripping reagent. The agreement between the calculated results and the experimental data was found satisfactory.     

Adsorption behavior of β-lactoglobulin onto polyethersulfone membrane surface

The adsorption of whey protein onto polyethersulfone (PES) membrane was investigated by static adsorption experiments to understand fouling mechanism and optimize the process condition to minimize the membrane fouling. Adsorption isotherm was applied to calculate the isotherm parameters such as adsorption capacity (K_F) and surface heterogeneity (1/n). The K_F values increased about 3.7 times at pH 3.0, 1.5 times at pH 5.2, and 2.3 times at pH 9.0 compared to that at pH 7.0. The hydrophobic interaction by dissociation of dimer structure of β-lactoglobulin to monomer structure at acidic and alkaline conditions showed the greatly increasing of the amount of protein adsorption by the protein and membrane interaction which might form the strong and rigid protein layer on the polymeric membrane surface. The addition of salt reduced the protein adsorption on PES membrane because of the interactions between charged protein molecules and salt ions.     

Grafting of High α-Cellulose Pulp Extracted from Sunflower Stalks for Removal of Hg (II) from Aqueous Solution

Dissolving pulp containing 95.5% α-cellulose was extracted from sunflower stalks. The pulped sunflower stalks (PSFS) were used as starting material for grafting with acrylamide (Aam). All factors affecting the grafting reaction were examined. These factors include liquor ratio (LR), ceric ammonium nitrate (CAN) concentration as a catalyst, Aam concentration, as well as reaction time and temperature. The grafted PSFS (GPSFS) samples were characterized by estimation of nitrogen %. The GPSFS was utilized as adsorbent material to remove Hg (II) ions from aqueous solutions. All factors affecting adsorption process were examined. These factors include pH, adsorbent concentration, temperature, and agitation time. The adsorption data show that the maximum adsorption capacity, q_e, of Hg (II) onto GPSFS is 625 mg/g. The adsorption data also showed that the adsorption of Hg (II) onto GPSFS obeys Langmuir and Freundlich isotherms.