Preparation of an ecofriendly chitosan–ZnO composite for chromium complex dye adsorption

Three chitosan‐ZnO composites were prepared by the chitin deacetylation process using zinc chloride as source material and sodium hydroxide as precipitant. The physical characteristics of chitosan‐ZnO composites were studied using Fourier Transform infrared spectroscopy and scanning electron microscopy. The adsorption of a chromium complex dye onto commercial chitosan, prepared chitosan and chitosan‐ZnO composites was investigated in aqueous dye solution. Dye calibration was carried out by UV‐vis spectroscopy. The calculated dye adsorption values for commercial chitosan, prepared chitosan, and chitosan‐ZnO composite samples are 0.0086, 0.0137, and 0.0214 mg/g respectively, indicating that the chitosan‐ZnO composites have better dye adsorption capacity than commercial chitosan and prepared chitosan. The experimental isotherm data for the composites fitted the Langmuir isotherm model well. Thus, the chitosan‐ZnO composites can be used as an effective biosorbent for the removal of anionic dyes.     

Magnetic and K+-cross-linked kappa-carrageenan nanocomposite beads and adsorption of crystal violet

Biopolymer-based magnetic beads, composed of kappa-carrageenan (κ-Car) and Fe₃O₄ nanoparticles, were synthesized. The magnetic beads were prepared through in situ precipitation of Fe²⁺/Fe³⁺ ions in the presence of carrageenan and subsequently treating with K⁺ solution. The structure of magnetic kappa-carrageenan beads (mκ-Carb) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and thermal gravimetric analysis techniques. According to SEM micrographs, an undulant and coarse structure with cubic-shaped sections was obtained when the magnetic nanoparticles were incorporated in composition of beads. The TEM image confirmed the formation of magnetic nanoparticles with an average size of 3–7 nm. The synthesized beads were examined as adsorbent to remove crystal violet dye from aqueous solutions. It was found that due to coarse surface, the rate of dye adsorption on magnetic beads can be improved slightly. The experimental adsorption kinetics was analyzed according to pseudo-first-order and pseudo-second-order kinetic models and the adsorption kinetics followed well the pseudo-second-order model. Isotherm adsorption data of dye on beads were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data have the best fit to Langmuir isotherm model, and maximum adsorption capacity of beads for dye obtained was 84.7 mg/g. The influence of pH on the variation of adsorption capacity of beads for crystal violet was not considerable. The thermodynamic parameters indicated that the adsorption of CV dye on beads is spontaneous.     

Extraction of 2-hydroxyphenol by surfactant coated nanosized magnetic particles

A colloidal suspension of magnetic particles coated with double layer surfactant molecules was prepared, characterized and used for separation of some chemicals. The aqueous magnetic fluid was prepared by chemical precipitation method and characterized by total organic carbon analyzer (TOC), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The TOC and TGA measurements indicate that the prepared magnetic particles are coated with surfactant molecules in double layers. The outer surfactant layer has free polar heads. TEM measurement results show that magnetic particles are nanosized. A mixture of 2-hydroxyphenol (strong polar) and 2-nitrophenol (weak polar) was chosen as the target system. Results show that the magnetic fluid can selectively adsorb 2-hydroxyphenol from the mixture, whereas the adsorption of 2-nitrophenol is insignificant. For 2-hydroxyphenol, the adsorption equilibrium can be described well by Langmuir isotherm, and the adsorption kinetic can be fitted well by a linear driving force mass transfer model.     

Efficient adsorption of dyes from aqueous solution by poly(vinyl alcohol‐co‐ethylene) nanofibre membranes modified with β‐cyclodextrin

In this paper, highly absorbent poly(vinyl alcohol‐co‐ethylene) nanofibre membranes modified by β‐cyclodextrin were prepared to adsorb dyestuff from water, and 1,2,3,4‐butanetetra carboxylic acid was used as a crosslinking agent, which greatly enhanced the adsorption capacity of the modified membranes. Field emission scanning electron microscopy and Fourier Transform–infrared spectroscopy were used to characterise the surface morphology and chemical structures of the membranes. Methylene Blue (MB) was used as the main adsorbed dye. The effect of pH value and concentration of the MB solution were also investigated, and equilibrium adsorption reached 139.2 mg/g when the pH value was 10.0. The adsorption process fitted well with the Langmuir adsorption isotherm model and was in accord with the pseudo‐second‐order kinetic model. Moreover, the modified membranes proved to have selective adsorption, especially for some cationic dyes other than MB, and had the potential to be recycled multiple times.     

Magnetic Zinc Ferrite–Alginic Biopolymer Composite: As an Alternative Adsorbent for the Removal of Dyes in Single and Ternary Dye System

Recently, magnetic bio-composites as adsorbent are widely being explored in waste water treatment because of their exceptional properties like high adsorption capacity, selectivity and cost-effective nature. In the present study, a novel recyclable magnetic composite containing magnetic zinc ferrite and alginate in alginic form (ZnFN–Alg) was developed. Various techniques like Fourier Transform-Infra Red, X-ray diffraction, transmission electron microscope with energy dispersive spectra, Brunauer–Emmett–Teller, thermo gravimetric-differential thermal analysis and Point Zero Charge (pH_zpc) were used to characterize the surface morphology of magnetic composite. The magnetic composite was used as adsorbent to remove congo red, crystal violet and brilliant green dyes in single and ternary systems. The kinetic studies data was best fitted to Lagergren pseudo second order whereas mechanism of adsorption was described by intra particle diffusion model in single as well as ternary systems. The adsorption equilibrium data was best fitted to Langmuir isotherm among various adsorption isotherm models. Thermodynamic studies confirmed that the adsorption process was spontaneous in nature. The regeneration ability of ZnFN–Alg composite was studied individually in single and ternary dye systems for seven cycles and showed significant results. It was concluded that magnetic ZnFN–Alg can serve as suitable alternative for the removal of dyes in single and ternary systems.     

Removal of Methylene Blue from Aqueous Solutions by using Cold Plasma,Microwave Radiation and Formaldehyde Treated Acorn Shell

In this paper, cold plasma (CPTAS), formaldehyde (FTAS), and microwave radiation treated (MTAS) acorn shell obtained from Quercus petraea tree as biosorbent was characterized and its dye removal ability at different dye concentrations was studied. The isoelectric point, functional groups and morphology of acorn shell was investigated as adsorbent surface characteristics. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and UV–Vis spectrophotometry were used. Methylene blue (MB) was used as model cationic dye. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms. The results indicated that the data for adsorption of MB onto treated acorn shell fitted well with the Langmuir isotherm model. Comparison of adsorption capacities of CPTAS with FTAS has shown a significant increase by as much as about 30 mg/g (33.32%) in MB adsorption.The pseudo-first order, pseudo-second order kinetic models were examined to evaluate the kinetic data, and the rate constants were calculated. Adsorption kinetic of dyes followed pseudo-first order kinetics. Thermodynamic parameters such as free energy, enthalpy, and entropy of dye adsorption were obtained. The results indicated that acorn shell could be used as a natural biosorbent for the removal of cationic dyes.     

Adsorption performance of mesoporous silicas towards a cationic dye. Influence of mesostructure on adsorption capacity

The dye adsorption performance of four mesoporous silicas with different structure and textural properties, MCM-41, MCM-48, SBA-15 and mesocellular silica foam (MCF), was studied and compared by using toluidine blue O (TBO) as dye model in aqueous solution. These materials were characterized by X-ray diffraction (XRD), small-angle X-ray scattering, nitrogen adsorption-desorption analyses, and transmission electron microscopy (TEM). The effect of some parameters such as adsorbent dosage, contact time, temperature, and pH on the TBO removal in aqueous solution was studied. Results showed that adsorption capacity raised when adsorbent dosage, contact time and pH solution were increased while an increase in temperature decreased the adsorption of TBO. Langmuir, Freundlich and Temkin isotherm models were employed to elucidate the adsorption mechanism while the adsorption rate data were analyzed according to the pseudo-first and second-order kinetic models. Results showed that adsorption of TBO onto MCM-48, SBA-15, and MCF fitted well the Freundlich isotherm model while the kinetic studies showed that adsorption process could be better described by the pseudo-second-order model for all mesoporous silicas. Finally, some solvents were evaluated to carried out dye desorption from the TBO-loaded mesoporous silicas founding that acetic acid was the most efficient.     

超声辅助合成磁性四氧化三铁/氧化石墨烯复合物及其在染料去除中的应用（英文）

A simple ultrasound-assisted co-precipitation method was developed to prepare ferroferric oxide/graphene oxide magnetic nanoparticles (Fe3O4/GO MNPs). The hysteresis loop of Fe3O4/GO MNPs demonstrated that the sample was typical of superparamagnetic material. The samples were characterized by transmission electron microscope, and it is found that the particles are of small size. The Fe3O4/GO MNPs were further used as an adsorbent to remove Rhodamine B. The effects of initial pH of the solution, the dosage of adsorbent, temperature, contact time and the presence of interfering dyes on adsorption performance were investigated as well. The adsorption equilibrium and kinetics data were fitted well with the Freundlich isotherm and the pseudo-second-order kinetic model respectively. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption of Rhodamine B. And the adsorption process was endothermic in nature. Furthermore, the magnetic composite with a high adsorption capacity of Rhodamine B could be effectively and simply separated using an external magnetic field. And the used particles could be regenerated and recycled easily. The magnetic composite could find potential applications for the removal of dye pollutants.     

Adsorption of trypsin onto magnetic ion‐exchange beads of poly(glycidylmethacrylate‐co‐ethyleneglycoldimethacrylate)

Magnetic beads were prepared from glycidyl methacrylate (GMA), and ethyleneglycol dimethylmethacrylate (EGDMA) in the presence of Fe₃O₄ nano‐powder via suspension polymerization. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super‐paramagnetic. The effects of contact time, pH, ionic strength, and temperature on the adsorption process have been studied. Adsorption equilibrium was established in about 120 min. The maximum adsorption of trypsin on the magnetic beads was obtained as 84.96 mg g^?1 at around pH 7.0. At increased ionic strength, the contribution of the electrostatic component to the overall binding decreased, and so the adsorption capacity. The experimental equilibrium data obtained trypsin adsorption onto magnetic beads fitted well to the Langmuir isotherm model. The result of kinetic analyzed for trypsin adsorption onto magnetic ion‐exchange beads showed that the second order rate equation was favorable. It was observed that after six adsorption–elution cycle, magnetic beads can be used without significant loss in trypsin adsorption capacity. Finally, the magnetic beads were used for separation of bovine serum albumin (BSA) and trypsin from binary solution in a batch system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nickel ion removal by porous potassium magnesium titanate made from plate-like crystals

Plate-like potassium magnesium titanate (KMTO) powder prepared by molten salt growth method and the KMTO porous ceramic synthesised by polymeric sponge replication method were used as sorbents to remove nickel ions from wastewater. Both powder and porous ceramic were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The maximum adsorption capacities of powder and porous ceramic were 96 and 24?mg?g^??1 respectively at a pH value of 6 (25°C). However, the removal efficiencies of both could reach up to 99%. Moreover, the adsorption kinetics for the KMTO powder and the porous ceramics followed the pseudo-second-order kinetic model, and the equilibrium data for the KMTO powder fitted the Langmuir isothermal model well, while the porous ceramics fitted with the Freundlich model. The mechanism of the adsorption by the KMTO powder and the porous ceramic was ion exchange. It was also shown that the nickel saturated KMTO powder and the porous ceramics were stable in leaching tests.     

Removal of Reactive Blue 21 onto magnetic chitosan microparticles functionalized with polyamidoamine dendrimers

Chitosan/poly(amidoamine) (MCS/PAMAM) microparticles were prepared as magnetic adsorbents for removal of Reactive Blue 21 (RB 21) dye from aqueous solution. Characterization of these particles was carried out using scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffractometry and vibrating sample magnetometry. The results indicate that the magnetic chitosan microparticles (MCS) were functionalized with PAMAM dendrimers and maintained its intrinsic magnetic properties. The effects of initial pH, adsorbent dose, initial concentration, contact time and temperature on adsorption were investigated. Kinetic studies showed that the dye adsorption process followed a pseudo-second-order kinetic model but that the adsorption rate was also influenced by intraparticle diffusion. Equilibrium adsorption isotherm data indicated a good fit to the Langmuir isotherm. The maximum adsorption capacities obtained from the Langmuir model were 555.56, 588.24, 625.00 and 666.67 mg g⁻¹ at 303, 313, 323 and 333 K, respectively. The thermodynamic parameters revealed the feasibility, spontaneity and endothermic nature of the adsorption. Recycling experiments confirmed the relative reusability of the adsorbent.     

Removal of Acid Red G dye from aqueous solutions by adsorption to MCM-41-layered double hydroxides composite

MCM-41 supported layered double hydroxides (LDH) composite materials (ML) were synthesized and studied for removal of Acid Red G (ARG), an anionic dye, with the adsorption method. ML was prepared using in situ synthesis procedure for the low supersaturation coprecipitation method, and ML10 and ML20 presented promising application towards ARG dye adsorption capacity in industrial wastewater. Powder samples were characterized by Xray diffraction, FTIR spectroscopy, scanning electron microscopy and energy dispersive spectrometry. The effects of different reaction time, initial solution pH and temperature on the dye adsorption capacity were investigated. Adsorption process was well described by pseudo-second-order kinetic model and Langmuir isotherm model. The fitting curves showed that ML10 and ML20 had higher adsorption rates and maintained a certain theoretical saturated adsorption capacity (92.19807mg/g and 96.41947mg/g, respectively) compared with LDH.     

Polyaniline‐functionalized magnetic nanoparticles for the removal of toxic dye from wastewater

A novel and inexpensive approach was adopted to develop a magnetic nanocomposite for the adsorption of cationic dye from an aqueous solution. This nanocomposite, which was based on a superparamagnetic iron oxide nanocore, was functionalized with a hydrophilic coating of polyaniline (PANI). The nanoparticle size, colloidal stability, surface chemistry, and magnetic properties were studied extensively by transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The polymeric functionalized magnetic nanocomposite had an average core size of 20–40 nm and a shell size of 6–10 nm. To evaluate the potential of such nanocomposites for dye adsorption, malachite green (MG) was exposed with different operational parameters, such as the pH, temperature, initial concentration of the dye, contact time, and reusability. The rate of the adsorption followed pseudo‐second‐order kinetics with the adsorption isotherm fit the Langmuir isotherm model well. The maximum adsorption capacity was 240 mg of MG/g of adsorbent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40840.     

阴离子聚电解质修饰磁性氧化石墨烯对碱性品红的吸附性能

采用简便一步溶剂热法制备了一种阴离子聚电解质聚（4-苯乙烯磺酸-共聚-顺丁烯二酸）钠盐（PSSMA）修饰的磁性氧化石墨烯复合材料（M-rGO/PSSMA）,并将其用作水溶液中阳离子型染料碱性品红（BF）去除的吸附剂。采用FTIR、SEM、TEM、TGA、VSM、DLS对制备的M-rGO/PSSMA进行表征。考察了溶液pH、吸附时间以及染料初始浓度对BF在M-rGO/PSSMA及M-rGO上吸附性能的影响;探讨了等温吸附过程、吸附动力学以及吸附机理。研究表明,M-rGO表面PSSMA的接枝可有效提高其对BF的吸附容量。PSSMA修饰后的磁性氧化石墨烯对BF的最大吸附容量高达588.2mg/g,是未经PSSMA修饰M-rGO吸附容量的3倍。另外,M-rGO/PSSMA对BF的吸附动力学和吸附等温数据分别符合准二级吸附动力学模型和Langmuir等温吸附模型。利用NaOH的乙醇溶液可对M-rGO/PSSMA进行有效的再生;通过外加磁场作用可实现吸附剂的回收再利用。本文所制备的石墨烯基复合材料可望成为环境废水中阳离子污染物去除的优良吸附剂。     

氨基和羧基功能化磁性微球去除水溶液中Cd(Ⅱ)和Pb(Ⅱ)

以甲基丙烯酸和丙烯酰胺为功能单体,通过悬浮聚合法制备了氨基和羧基双功能化的磁性复合微球(Fe3 O4@SiO2-NH2/COOH),并探讨了其对水溶液中Cd(Ⅱ)和Pb(Ⅱ)的吸附性能.X-射线衍射(XRD)分析表明,制备的磁性吸附剂内核为Fe3 O4.红外光谱(FT-IR)和扫描电镜(SEM)测试表明,氨基和羧基对Fe3 O4@SiO2表面改性成功.吸附试验显示,Fe3O4@SiO2-NH2/COOH吸附Cd(Ⅱ)和Pb(Ⅱ)的最优pH值分别为5.0和5.5,吸附过程均符合动力学准二级模型和Langmuir吸附等温模型,吸附剂对Cd(Ⅱ)和Pb(Ⅱ)最大吸附量分别为207.807 mg/g和168.995 mg/g.实际饮用水样中Cd(Ⅱ)和Pb(Ⅱ)的吸附表明,去除率分别可达97.74％和91.44％.该磁性吸附剂对两种重金属离子吸附量大、去除率高,具有良好的实际应用潜力.     

Removal of Basic Dye from Aqueous Solution using Cinnamomum camphora Sawdust: Kinetics,Isotherms, Thermodynamics,and Mass-Transfer Processes

Cinnamomum camphora sawdust (CCS) was employed as a cheap and effective biosorbent to remove basic dye from aqueous solutions. The biosorbent was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Adsorption experiments were carried out in a batch system as a function of initial pH, adsorbent dose and particle size, ionic strength, initial dye concentration, and reaction temperature. The selected basic dye (malachite green) adsorption onto CCS significantly depended on these factors. By comparative kinetic analysis, the rate of sorption was conformed with good correlation to pseudo-second-order kinetics. Equilibrium data were fitted well by Langmuir isotherm with the maximum adsorption capacity of 155.0 mg/g at the temperature of 318 K and pH 7.0 ± 0.1. Thermodynamic parameters proved that malachite green dye biosorption process was spontaneous and endothermic within the investigated temperature range. The mechanism of adsorption was also studied. It was found that the adsorption of malachite green onto CCS was mainly governed by film diffusion. The electrostatic attractions and ionic interactions between malachite green dye and CCS might be responsible for the adsorption process. The comparative investigation suggested that the sawdust could be considered as a potential adsorbent for malachite green dye removal from wastewater.     

Synthesis and characterization of magnetic beads containing aminated fibrous surfaces for removal of Reactive Green 19 dye: kinetics and thermodynamic parameters

BACKGROUND: Poly(HEMA‐co‐MMA) beads were prepared from 2‐hydroxyethyl‐methacrylate (HEMA) and methylmethacrylate (MMA) in the presence of FeCl₃. Thermal co‐precipitation of Fe(III) ions containing beads with Fe(II) ions was carried out under alkaline conditions. The magnetic beads were grafted with poly(glycidylmethacrylate; p(GMA)), and the epoxy groups of the grafted p(GMA) brushes were converted into amino groups by reaction with ammonia. RESULTS: The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), Mössbauer spectroscopy and scanning electron microscopy (SEM). The maximum adsorption of Reactive Green‐19 (RG‐19) dye on the p(GMA) grafted and amine modified magnetic beads was around pH 3.0. The adsorption capacity of magnetic beads was 84.6 mg dye g^?1. The effects of adsorbent dosage, ionic strength and temperature have also been reported. Batch kinetic sorption experiments showed that a pseudo‐second‐order rate kinetic model was applicable. CONCLUSION: The p(GMA) grafted and amine modified magnetic beads (adsorbent) were expected to have the advantage of mobility of the grafted chains in the removal of acidic dyes from aqueous solutions. The magnetic beads have potential as an adsorbent for removal of pollutants under various experimental conditions without significant reduction in their initial adsorption capacity. Copyright © 2011 Society of Chemical Industry     

Preparation of a porous,magnetic, quaternary chitosan salt by preadsorption and desorption for azo dye adsorption from water

A porous magnetic quaternary chitosan salt (pre‐CS/EPTAC/Fe₃O₄) was successfully prepared via a kind of novel method of preadsorption and desorption. The physicochemical properties of pre‐CS/EPTAC/Fe₃O₄ were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometry. The adsorption of pre‐CS/EPTAC/Fe₃O₄ for methyl orange (MO) showed much higher dye uptakes compared with Npre‐CS/EPTAC/Fe₃O₄ without the preadsorption and desorption of MO, and the maximum adsorption capability for MO was 486.1 mg/g. Adsorption isotherms and adsorption kinetics were well fitted by the Freundlich isotherm model and the pseudo‐second order model, respectively. Thermodynamic parameters, such as the standard free energy change, enthalpy change, and entropy change, were also calculated; this indicated that the adsorption was spontaneous and exothermic. The introduction of MO preadsorption and desorption into the process of preparation improved not only the adsorption of MO but also the adsorption of acid red 1 and orange G. Furthermore, pre‐CS/EPTAC/Fe₃O₄ particles could be easily regenerated and remained almost constant (98.5%) for six cycles of adsorption and desorption. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43448     

Adsorption of Crystal Violet From Aqueous Solution by Citric Acid Modified Rice Straw: Equilibrium,Kinetics, and Thermodynamics

Rice straw, an abundant, lignocellulosic agricultural residue was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The application potential of the prepared adsorbent to remove hazardous Crystal Violet dye from its aqueous solution was investigated. The morphological and chemical characteristics of the adsorbent were established by scanning electron microscopy (SEM), surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared (FTIR) spectroscopy. Batch adsorption studies were carried out as a function of solution pH, adsorbent dose, initial dye concentration, and temperature, in order to get insights into the effect of these independent parameters on the adsorption process. The Langmuir, Freundlich, and Dubinin–Radushkevich models were used to describe the equilibrium adsorption data. The sorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and exothermic nature of the adsorption process.     

Adsorption of Nattokinase by Amino Acid-Conjugated Magnetic Nanoadsorbents

Purified nattokinase has the potential to be developed as functional food additives and drugs to prevent or treat several diseases. Arginine modified magnetic nanoparticles to isolate nattokinase from Natto broth were developed in this study. Functional nanoparticles were prepared by covalently conjugating cationic ligands onto the surface via a carbonyldiimidazole coupling method. The arginine-modified magnetic nanoparticles demonstrated the 2.4-fold adsorption of nattokinase compared with the lysine modified nanoparticles. The behavior of the adsorption and desorption for nattokinase onto surface-modified magnetic nanoadsorbents from the natto solution was systematically investigated. The results of transmission electron microscopy indicated that surface modification on nanoparticles did not affect size distribution of magnetic nanoadsorbents. The adsorption kinetics was fitted by the pseudo-first-order and pseudo-second-order equations. It was found that the pseudo-first-order rate equation was the best one for characterizing the adsorption kinetics. In this study the purification factor, the maximum adsorption capacity, and recovery yield were 8.0, 3.79 U/mg nanoparticles, and 15%, respectively. Overall, our results demonstrated that the arginine-coated magnetic nanoadsorbents could efficiently adsorb nattokinase from the Natto broth.