Competitive Removal of Heavy Metal Ions by Starch-Graft-Acrylic Acid Copolymers

Graft copolymerization of acrylic acid (AA) onto starch was carried out with ceric ammonium nitrate as initiator under nitrogen atmosphere. The structures of the synthesized graft copolymers were identified by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The grafting percentages (GP%) of starch-graft-acrylic acid (S-g-AA) copolymers were determined. Increasing the molar concentration of AA from 0.1 to 0.5 mol/L caused a significant increase in the GP%. The effect of GP% of S-g-AA copolymers on the competitive removal of Pb²⁺, Cu²⁺, Cd²⁺ ions from aqueous solution was investigated at pH 4.5. The concentrations of each ion in aqueous solution were equal to each other, which were kept constant at 4 mmol/L. Metal ion removal capacities were determined by atomic absorption spectrophotometer (AAS). Metal ion removal capacities of S-g-AA copolymers rose with the increase in GP% of the copolymers and the order of the removal of heavy metal ions was Pb²⁺ > Cu²⁺ > Cd²⁺.     

Adsorptions of Some Heavy Metal Ions in Aqueous Solutions by Acrylamide/Maleic Acid Hydrogels

Abstract

In this study, acrylamide—maleic acid (AAm/MA) hydrogels in the form of rod have been prepared by γ-radiation. They have been used for adsorption of some heavy metal ions such as uranium, iron, and copper. For the hydrogel containing 40 mg of maleic acid and irradiated at 3.73 kGy, maximum and minimum swellings in the aqueous solutions of the heavy metal ions have been observed with water (1480%) and the aqueous solution of iron(III) nitrate (410%), respectively. Diffusions of water and heavy metal ions onto hydrogels have been found to be of the non-Fickian type of diffusion. In experiments of uranyl ions adsorption, Type II adsorption has been found. One gram of AAm/MA hydrogels sorbed 14–86 mg uranyl ions from solutions of uranyl acetate, 14–90 mg uranyl ions from solutions of uranyl nitrate, 16–39 mg iron ions from solutions of iron(IV) nitrate, and 28–81 mg copper ions from solutions of copper acetate, while acrylamide hydrogel did not sorb any heavy metals ions.     

Behaviors of Acrylamide/Itaconic Acid Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Abstract

In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with γ-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178–219 mg uranyl ions from the solutions of uranyl acetate, 42–76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.     

Adsorptive Removal of Pb(II) and Cu(II) Ions from Aqueous Solutions by Cross-Linked Chitosan-Polyphosphate-Epichlorohydrin Beads

In this study, the cross-linked chitosan-polyphosphate-epichlorohydrin (CCPE) beads were prepared by cross-linking chitosan with both polyphosphate and epichlorohydrin and used as bioadsorbent for the removal of Pb(II) and Cu(II) ions from aqueous solutions. The effects of the dosage of CCPE beads, solution pH, initial metal ion concentration, contact time, and temperature were investigated. Then, three important factors were selected to optimize the removal processes by the orthogonal test. The results show that CCPE beads can effectively remove the Pb(II) and Cu(II) ions from aqueous solutions, and the maximum percentage removals for Pb(II) and Cu(II) ions are 99.7% and 91.2%, respectively. The data show also that the removal processes for both Pb(II) and Cu(II) ions fit best the pseudo-second order kinetic model. Moreover, the decrease of the adsorption ability of CCPE beads is less than 10% after reuse for 9 times, which suggests that CCPE beads have good reusability.     

玉米淀粉接枝丙烯酸共聚反应研究

对于过硫酸铵-亚硫酸氢钠组成的氧化还原引发体系下的淀粉-丙烯酸接枝共聚反应。本课题较系统地研究了引发剂浓度、单体浓度、单体中和度、反应温度和反应时间等因素对该接枝共聚反应的影响,通过物料的二次加入有效地提高了该反应的接枝效果,并对该接枝共聚物进行了红外测试表征。     

油页岩灰渣合成Na-A沸石用于去除水溶液中Cu2+（英文）

Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffrac- tion and Brunaner Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu （II） from aqueous solutions. The effects of operating pa- rameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption iso- therm is 156.7 mg.g-t of Cu （lI）. The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy （AG）, enthalpy （AH） and en- tropy （AS）, are used to predict the nature of the adsorption process. The negative AG values at different tempera- tures confirm that the adsorption processes are spontaneous.     

Removal of Orange II from Aqueous Solutions Using N-Vinyl Imidazole-based Hydrogels as Adsorbents

Poly(N-vinyl imidazole) hydrogel (p-VIm) and its partially quaternized analogue (p-VIm-Ar) were prepared and used for the removal of Orange II (OII). A fourier transform infrared spectrophotometer, scanning electron microscope with an energy dispersive X-ray spectrometer attached, thermogravimetric analyzer, zeta potential analyzer, and a drop shape analyzer were used for the characterization of the hydrogels. The influence of some experimental parameters, such as pH of the OII solution, contact time, and initial OII concentration on the adsorption process, was examined, and the obtained data were used to calculate the isotherm and kinetic parameters. Adsorption processes of OII onto adsorbents were coherent with the Langmuir isotherm and pseudo-second-order kinetic models. The quaternized analogue exhibited remarkable adsorption performance in the pH range of 2–12, while the effective adsorption with p-VIm occurred only at pH 2.0. The maximum adsorption capacity values of adsorbents were determined as 2331 (for p-VIm) and 1327 mg g^?1 (for p-VIm-Ar) at pH 2.0 and 132 (for p-VIm) and 1357 mg g^?1 (for p-VIm-Ar) at pH 6.0.     

淀粉接枝丙烯酸聚合型絮凝剂的合成及絮凝性能研究

以可溶性淀粉为主要原料,以丙烯酸为接枝单体,硝酸铈铵和过硫酸钾为复合引发剂,采用溶液聚合的方法对糊化处理后的淀粉进行接枝聚合,合成出环保型淀粉衍生物水处理絮凝剂。通过对接枝聚合反应温度、反应时间、引发剂用量以及丙烯酸单体用量等因素对接枝率影响的研究,确定较佳的接枝产物合成条件：淀粉10g,单体丙烯酸用量10mL,硝酸铈铵和过硫酸钾（摩尔比1：1）复合引发体系用量2mmol,接枝反应温度50℃,接枝反应时间3h,接枝率达到43．2％。利用选煤后的废水对其产品絮凝性能进行实验研究,确定较佳的废水絮凝处理条件。     

Removal of Cationic Dyes from Aqueous Solution by Hydrophobically Modified Poly(acrylic Acid) Hydrogels

Hydrophobically modified poly(acrylic acid) hydrogels were synthesized using acrylic acid (AA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and butyl methacrylate (BMA) as copolymer monomers. These hydrogels were carried out for removal cationic dyes from aqueous solution. It was found that the adsorption of cationic dye depended on the length of the side chain, hydrophobic monomer (MMA, EMA and BMA) content and pH of the solution. Increasing the hydrophobic monomer content led to an increase in the adsorption of cationic dyes on the hydrogels. The adsorption kinetics and isotherms of hydrogels were in good agreement with pseudo–second-order equation and the Langmuir equation, respectively. The cationic dyes adsorption of hydrogels involved a mechanism that combined swelling and electrostatic and hydrophobic interaction.     

Adsorption of Cu2+ and Ni2+ from Aqueous Solution by Arabinoxylan Hydrogel: Equilibrium,Kinetic, Competitive Adsorption

In this work, arabinoxylan-graft-acrylic acid (AX-g-AA) hydrogel was prepared and used as an adsorbent to remove and recover Cu²⁺ and Ni²⁺ from aqueous solutions. The influences of pH, ligand content on the adsorption capacity of the hydrogel, adsorption equilibrium, and kinetic were studied in detail. The competitive adsorption and recovery of heavy metal ions, regeneration and reusability of the hydrogel were present. Furthermore, the relationship between the physiochemical properties of the adsorbent and its adsorption performance was also studied. The results showed that a more expanded network favored the diffusion and adsorption of metal ions. Cu²⁺ and Ni²⁺ uptake by this hydrogel was pH and concentration dependent with the maximum loading of 330.1 mg/g for Cu²⁺ and 248.7 mg/g for Ni²⁺. The pseudo-second-order kinetics suggested that the ion exchange process was chemisorption-controlled. The Langmuir equation could well describe the isotherm data. Cu²⁺ and Ni²⁺ adsorbed on the hydrogel could be effectively recovered in a diluted HNO₃ solution (0.01 M) in 30 min. AX-g-AA hydrogel also exhibited highly efficient reusability, and thus could be used repeatedly.     

Removal of Lead and Cadmium Ions from Aqueous Solutions Using Sulphur and Oxygen Donor Ligand Bearing Hydrogels

A new thiourea and urea functional monomers were synthesized. A series of hydrogels were prepared by photopolymerization. The hydrogels were used for the removal of Pb(II) and Cd(II) ions from aqueous solutions. The influence of the uptake conditions such as the pH, the time, and the initial feed concentration on the metal ion binding capacity of hydrogel was tested. The selectivity of the hydrogels towards the different metal ions was also tested. The adsorption isotherm models were applied. The limits of detection and quantification were calculated. The usability of the hydrogels for preconcentration studies were also investigated.     

丙烯酸接枝聚乙烯增容LLDPE／淀粉共混体系研究

就丙烯酸接枝ＬＬＤＰＥ对ＬＬＤＰＥ／淀粉可生物降解共混体系力学性能的影响进行了研究,并对其与接枝改性淀粉的配合增容作用作了进一步探索。结果表明丙烯酸接枝ＬＬＤＰＥ可以明显提高ＬＬＤＰＥ和淀粉的相容性,共混体系拉伸强度可达１０．３５ＭＰａ,伸长率达１００％。此外,研究表明脲对提高体系拉伸强度有所帮助,但导致伸长率下降。     

泡沫分离法除去水溶液中微量铜离子的工艺

以十二烷基苯磺酸为表面活性物质,自制的单金属离子水溶液为研究体系,对泡沫分离法除去水溶液中金属离子的工艺进行了研究,重点考察了溶液的pH、鼓泡气体流量、表面活性剂浓度及泡沫塔装液量的影响. 结果表明,十二烷基苯磺酸具有良好的起泡性能,对水溶液中铜离子的去除效果也比较理想,最佳操作条件下富集比为18.2,去除率为96.1%,与常规的表面活性剂十二烷基硫酸钠相比,十二烷基苯磺酸在泡沫分离过程结束后不会在体系中残留金属离子,这为探索脱盐新方法提供了依据.     

Swelling Characterization of Polyelectrolyte Poly(Hydroxamic Acid) Hydrogels in Aqueous Thiazin Dye Solutions

In this study, swelling behavior of polyelectrolyte poly(hydroxamic acid) (PHA) hydrogels have been investigated in aqueous thiazin dye solutions. PHA hydrogels were prepared by free radical polymerizations of acrylamide with some cross-linkers such as N,N′ methylenebisacrylamide (NBisA) and ethylene glycol dimethacrylate (EGDMA); then they were used in experiments on swelling and diffusion of some water-soluble cationic dyes such as methylene blue (MB), thionin (T), and toluidin blue (TB). Swelling experiments were performed in water at 25°C, gravimetrically. The equilibrium swelling percent (S%) values of PHA hydrogels were calculated as 238–2705%. Some swelling kinetic parameters such as initial swelling rate, swelling rate constant, and maximum (theoretical) swelling percent were found. Diffusional behavior of dye solutions was investigated. Dye diffusion into hydrogels was found to be non-Fickian in character. Diffusion exponent (n) is over 0.50. For sorption of thiazin cationic dyes, MB, T, and TB to PHA hydrogels were studied by batch sorption technique at 25°C. PHA hydrogels in the dye solutions showed the dark coloration. In the experiments of the adsorption, S-type adsorption in the Giles classification system was found.     

Hydrogels with Acid Groups for Removal of Copper(II) and Lead(II) Ions

Acrylamide-maleic acid (AAM-MA) hydrogels having high acid group content prepared with different maleic acid ratios were used for the removal of Cu(II) and Pb(II) ions from aqueous solutions in competitive and noncompetitive conditions. The effects of pH, time, and initial metal ion concentration on the metal ion adsorption capacity were investigated. The adsorption isotherm models were applied on experimental data and it is shown that the Freundlich equation was the best model for Cu(II) ion while the Langmuir isotherm model was the best one for Pb(II) ion. The stability constants of acrylamide-maleic acid hydrogel-Cu(II) and Pb(II) complexes were also determined by van den Berg/Ruzic transformation, and K values obtained were 1.60 × 10³ and 1.81 × 10³ for Cu(II) and Pb(II) ions, respectively. The experiments under competitive conditions showed that the hydrogels prefered Pb(II) ion and this preference increased with increasing of carboxylic acid group content (AGC) of polymers. It is stated that these hydrogels can be regenerated efficiently (>95%) and used repeatedly.     

Preparation of starch/poly(N,N-Diethylaminoethyl methacrylate) hydrogel and its use in dye removal from aqueous solutions

Starch/poly(N,N-Diethylaminoethyl methacrylate) graft copolymer was synthesized by graft polymerizing N,N-Diethylaminoethyl methacrylate monomers onto cooked starch using ceric ammonium nitrate/nitric acid mixture as an initiator. After extracting the graft copolymer from the homopolymer and evaluating the graft yield, the graft copolymer was subjected to crosslinking treatment using epichlorohydrin in alkaline medium to convert it to hydrogel. The so prepared hydrogel was evaluated for its swelling ratio which was found to be 100. The hydrogel with its cationic functionality was tried for removing the anionic dye Direct Red 81 from its aqueous solution and all factors affecting the hydrogel adsorption capacity towards the anionic dye, like the hydrogel graft yield, the adsorbate pH, the immersion time and the hydrogel dose were studied. The data obtained from the adsorption results were found to fit well to the Langmuir adsorption model.     

淀粉接枝丙烯酸和丙烯酰胺共聚型高吸水性树脂的制备

采用淀粉接枝丙烯酸（AA）和丙烯酰胺（AM）单体,以N,N＇-亚甲基双丙烯酰胺为交联剂,以氧化还原体系（（NH4）2S2O8-Na2SO3）为引发剂,采用水溶液聚合法制备具有耐盐型高吸水性树脂,分析了制备条件对耐盐型高吸水性树脂性能的影响,确定较合理的制备工艺。     

Removal of Ce(IV) Ions from Aqueous Solutions Using Sawdust Coated by Electroactive Polymers

In this work, adsorption of the Ce(IV) ions onto polypyrrole (PPy) and polyaniline (PAn) conducting electroactive polymers as coated form on sawdust has been investigated. The effect of some important parameters such as initial concentration of the Ce(IV) ion adsorbent dosage, and contact time was studied. The experiments were carried out using both batch and column systems at room temperature. The equilibrium adsorption capacity of sawdust coated by polypyrrole and polyaniline for the removal of Ce(IV) ion was measured and extrapolated using linear Freundlich and Langmuir isotherms. It was found that sawdust modified by PPy and PAn improved the removal efficiency of Ce(IV) ions from aqueous solutions greatly.     

Removal of Co2+ Ions from Aqueous Solution by Ferrite Process

Abstract

A mathematical model was developed to investigate the characteristics of Co²⁺ removal by the pre-formed ferrite process. In this study, surface adsorption, hydrolysis-precipitation, and ion exchange were considered as Co²⁺ removal mechanisms, and incorporated into the model. In addition, a series of batch experiments was performed to remove Co²⁺ ions from aqueous solution, and the removal characteristics of Co²⁺ were analyzed by considering equilibrium pH, shaking time, ionic strength, and the effect of EDTA and Ca²⁺ as a chelating agent and a competing cation, respectively. Finally, the model proposed in this study was applied to the given experimental system, and it turned out that the pH-edge could be successfully predicted by the model. The experimental results were well-fitted by a Freundlich isotherm, and the standard enthalpy change of the reaction was 25.02 kJ·mol^?1. The removal efficiency was slightly diminished by increasing the ionic strength and the initial concentration of Co²⁺; however, the effect of the competing cation, Ca²⁺, was negligible.