Synthesis and characterization of CoFe2O4@SiO2-polyethyleneimine magnetic nanoparticle and its application for ultrasonic-assisted removal of disulfine blue dye from aqueous solution

In the present work, a simple synthesis approach was applied for the fabrication of CoFe₂O₄@SiO₂-polyethyleneimine magnetic nanoparticles as an effective sorbent for ultrasonic-assisted removal of disulfine blue dye from an aqueous solution. For identification and characterization of prepared sorbent, different analysis including Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), Vibrating sample magnetometer (VSM), Energy dispersive X-ray analysis (EDX) and Transmission electron microscopy (TEM) were applied. The effect of effective parameters on the removal of disulfine blue such as pH, sorbent mass, ultrasonic time and disulfine blue concentration were also assessed. The optimum values for investigated parameters were achieved to be as follows: pH of 5.0, sorbent mass of 0.015 g, ultrasonic time of 5.0 min and disulfine blue concentration of 10.0 mg L⁻¹. Different isotherm and kinetic models were used for the evaluation of isotherm and kinetic of adsorption. Results showed that the Langmuir isotherm model was better than other isotherm models as well as the second-order equation model was selected as a kinetic model. The maximum adsorption capacity of the proposed magnetic sorbent was achieved to be 110.0 mg g⁻¹ which shows the applicability of proposed sorbent for removal of disulfine blue dye from aqueous solution.     

Fabrication and characterization of CMC‐based magnetic superabsorbent hydrogel nanocomposites for crystal violet removal

In this research work, novel magnetic superabsorbent hydrogel nanocomposites (MSHNs) based on carboxymethyl cellulose were prepared via a facile “one‐pot” two step approach. Magnetic iron oxide nanoparticles were in situ synthesized and incorporated into carboxymethyl cellulose/poly(acrylic acid) polymer hydrogel. The morphology and chemical composition of MSHNs as well as the presence of magnetic iron oxide nanoparticles were evaluated by using Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X‐Ray diffraction, ultraviolet–visible spectroscopy, thermogravimetric analysis, and vibrating sample magnetometer. The effect of different reaction parameters on the swelling capacity of MSHNs was investigated. Furthermore, batch adsorption experiments of crystal violet dye onto MSHNs were studied by varying solution pH, initial dye concentration, and temperature. Evaluation of thermodynamic parameters of crystal violet adsorption confirmed that the adsorption was spontaneous and endothermic process in nature. The equilibrium study revealed that the dye adsorption behavior of MHSNs followed the Redlich‐Peterson isotherm model. Finally, the dye adsorption experiment data was well fitted by the pseudo‐second‐order kinetic model with the regression coefficient (R²) of 0.9979. Our results suggest that the MHSNs with facile preparation method, high swelling capacity, and high dye adsorption capacity may be used as promising adsorbents for fast removal of various dyes from aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.     

Modification of microcrystalline cellulose with pyridone derivatives for removal of cationic dyes from aqueous solutions

Microcrystalline cellulose (MCC) was modified with pyridone derivatives such as pyridone diester (PDE) and pyridone diacid (PDA) by using succinic acid anhydride as a linker. The modified MCCs were characterized by the fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, elemental analysis and solid state ¹³C NMR. The adsorption capacities of the modified MCCs to cationic dyes were examined by using methylene blue (MB) as a model dye. It was found that the kinetic adsorption data followed the pseudo-second-order kinetic model, and the adsorption equilibriums were reached less than 10 min. The isothermal adsorption data were fitted with the Langmuir isotherm model very well, from which the maximum adsorption capacities of the MCCs modified with PDE and PDA were determined to be 101.01 and 142.86 mg/g, respectively. Further investigation showed that the modified MCCs were pH-dependent for adsorption of MB in aqueous solutions. The modified MCCs could be used for removal of MB from an aqueous solution at pH 8, and reused by regeneration in an acidic solution. It was tested that the modified MCCs had a high reusability for removal of MB from aqueous solutions, and still maintained high adsorption capacities even after multiple cycles of desorption–adsorption processes. Hence, the MCCs modified with PDE and PDA could be an effective and efficient approach to removal of cationic dyes from aqueous solutions.     

Zinc oxide nanorod‐loaded activated carbon for ultrasound‐assisted adsorption of safranin O: Central composite design and genetic algorithm optimization

This paper focuses on the development of an effective methodology to obtain the optimum ultrasonic‐assisted removal of a dye, safranin O (SO), under optimum conditions that maximize the removal percentage, using ZnO nanorod‐loaded activated carbon (ZnO‐NRs‐AC) in aqueous solution. Central composite design coupled with genetic algorithm was used for parameter optimization. The effects of variables such as pH, initial dye concentration, mass of ZnO‐NRs‐AC and sonication time were studied. The interactive and main effects of these variables were evaluated using analysis of variance. The structural and physicochemical properties of the ZnO‐NRs‐AC adsorbent were investigated using field emission scanning electron microscopy and X‐ray diffraction. Adsorption equilibrium data were fitted well with the Langmuir isotherm and the maximum monolayer capacity was found to be 32.06 mg g^?1. Studies of the adsorption kinetics of the SO dye showed a rapid sorption dynamic with a ^pseudo‐second‐order kinetic model, suggesting a chemisorption mechanism.     

Study of congo red adsorption on the polyaniline and polypyrrole

Polyaniline (PANI) and polypyrrole (PPY) were synthesized via in situ chemical oxidative polymerization and are used as adsorbents for removal of Congo Red (CR) dye from aqueous solution. The effects of various experimental parameters including pH of the solution, contact time, initial concentration, adsorbent dosage, and temperature on adsorption of CR by PANI and PPY were systematically investigated. The experimental results showed that the adsorption efficiency was increased with contact time and adsorbent dosage. The maximum removal efficiency was found after 45 minutes of solid/liquid contact with adsorbent doses of 0.4 and 1.73?g/L for PANI and PPY, respectively. The kinetic data were best fitted by the pseudo-second-order model. The adsorption equilibrium results were well fitted by the Langmuir isotherm model. These results suggest that the PANI and PPY can be used as alternative adsorbents for the treatment of wastewaters containing dyes.     

Adsorption of Reactive Blue 4 dye from water solutions by carbon nanotubes: experiment and theory

Multi-walled and single-walled carbon nanotubes were used as nanoadsorbents for the successful removal of Reactive Blue 4 textile dye from aqueous solutions. The adsorbents were characterised by infrared and Raman spectroscopy, N(2) adsorption/desorption isotherms and scanning and transmission electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium isotherms at 298-323 K was fixed at 4 hours for both adsorbents. The general order kinetic model provided the best fit to the experimental data compared with pseudo-first order and pseudo-second order kinetic adsorption models. For Reactive Blue 4 dye, the equilibrium data (298 to 323 K) were best fitted to the Liu isotherm model. The maximum sorption capacity for adsorption of the dye occurred at 323 K, attaining values of 502.5 and 567.7 mg g(-1) for MWCNT and SWCNT, respectively. Simulated dyehouse effluents were used to check the applicability of the proposed nanoadsorbents for effluent treatment (removal of 99.89% and 99.98%, for MWCNT and SWCNT, respectively). The interaction of Reactive Blue 4 textile dye with single-walled carbon nanotubes (SWCNTs) was investigated using first principles calculations based on density functional theory. Results from ab initio calculations indicated that Reactive Blue 4 textile dye could be adsorbed on SWCNT through an electrostatic interaction; these results are in agreement with the experimental predictions.     

Modeling and Optimization of Adsorption Removal of Reactive Orange 13 on the Alginate–Montmorillonite–Polyaniline Nanocomposite via Response Surface Methodology

In this work, an alginate–montmorillonite–polyaniline (Alg–MMT–PANI ) nanocomposite (NC) was synthesized and applied for the adsorptive removal of reactive Orange 13 (RO13 ) as a model azo dye compound. The Alg–MMT–PANI NC was prepared by the polymerization of aniline in the presence of Alg–MMT hybrid through in situ polymerization. The optimization and modeling of the removal process was carried out using the response surface methodology (RSM ) based on central composite design (CCD ). Important parameters influencing the adsorption removal of RO13 , including the initial concentration of RO13 , pH , adsorbent dose, and contact time, were selected as input variables for RSM . Furthermore, the adsorption kinetic studies revealed that the experimental data best fitted with a pseudo‐second‐order model. Additionally, adsorption isotherm studies revealed that the obtained data were well fitted to the Langmuir isotherm model and, accordingly, the maximum adsorption capacity, q_m , was obtained at level of 111.111 mg/g.     

Preparation of graphene oxide–chitosan composite and adsorption performance for uranium

The composite adsorbent graphene oxide–chitosan was prepared using graphite and chitosan as the initial materials. The structures and morphology of the products were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. The products were used to remove uranium from aqueous solution by batch adsorption experiments. The effects of pH, adsorbent dosage, contact time, initial uranium concentration and temperature on the uranium removal were investigated, and the results were fitted by the adsorption isotherm models. The adsorption kinetic and thermodynamic were also studied in detail.     

Non-linear modelling of the adsorption of Indigo Carmine dye from wastewater onto characterized activated carbon/volcanic ash composite

Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities like Indigo Carmine (IC), remains a highly contested agenda from a global point. The birth of non-linear modelling for these auxiliary entities is also of significant interest in order to avoid loss of some useful information. With the renaissance of activated carbon (AC), the AC prepared from palm kernel shells (PKSAC) and composite prepared by combining the PKSAC and porous volcanic ash (BVA) from the foot of active volcanic mountain of Cameroon will be of significant contribution for ever increasing pollution problems. Non-linear modelling method was used to model the uptake capacity by adsorption process of IC onto PKSAC and PKSAC/BVA composite. Effects of contact time (0–60 min), adsorbent dose, pH of solution and initial dye concentration (10–20 ppm) were studied on the quantity removal of the hazardous IC dye from aqueous solution in a batch experiment. The prepared PKSAC and PKSAC/BVA composite were characterized using Nitrogen adsorption at 77 K (BET), Fourier transform Infrared spectroscopy (FTIR), Sacanning electron microscopy with energy dispersive X Ray (SEM-EDX), and particle size. The optimum IC uptake was 11.025 and 12.642 mg/g for PKSAC and PKSAC/BVA composites adsorbent respectively. Four Isotherms and kinetic non-linear regression models each were used to model the adsorption data. It results that for the isotherm models, the Langmuir and Freundlich isotherm models best fitted the adsorption phenomenon while pseudo-first and pseudo-second order kinetic models well described the adsorption mechanism. Furthermore, the adsorption speed constant (α) of the Elovich kinetic model being higher than the desorption coefficient (β) implies chemisorption was the dominant mechanism in the adsorption process. The composite shows 14.67% higher in retention capacity of the IC dye than the pristine carbon. Conclusively, the expanding of activated carbon/volcanic ash composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.     

羧基化石墨烯对4种离子型染料的吸附脱色

合成的羧基化石墨烯（G-COOH）用FT-IR进行表征,并对G-COOH用于水溶液中甲基紫、中性红、灿烂黄和茜素红4种离子型染料的吸附性能进行了研究。 考察了吸附剂用量、吸附时间、初始浓度以及溶液pH值等条件对吸附效果的影响。 同时,研究了甲基紫染料的脱附性能,结果表明,用NaOH/EtOH混合溶液洗脱甲基紫,洗脱率可达88.2%,洗脱后的G-COOH可再利用。 从热力学角度探讨得出,G-COOH对阳离子染料甲基紫和中性红的吸附行为能够较好的符合Langmuir等温吸附模型,而对阴离子染料灿烂黄和茜素红的吸附行为则能够较好的符合Freundlich等温吸附模型,计算的吸附参数表明,G-COOH对4种染料的吸附过程容易进行。 动力学研究表明,G-COOH对4种离子型染料的吸附行为均能较好的符合准二级吸附模型。 该实验研究表明,在处理染料废水时,G-COOH为相当优异的吸附剂。     

复合改性膨胀石墨的制备及对酸性艳蓝染料的吸附

采用相同反离子协同磷酸活化法, 以十六烷基三甲基溴化铵(CTAB)-KBr为复合改性剂, 制备了一种高效吸附剂复合改性膨胀石墨(M-EG), 通过扫描电子显微镜(SEM)、 傅里叶变换红外光谱(FTIR)及X射线电子能谱(XPS)等对膨胀石墨(EG)和改性膨胀石墨(M-EG)的形貌结构、 组成和价态进行了表征, 考察了EG和M-EG对酸性艳蓝染料废水的处理效果. 结果表明, 复合改性后的膨胀石墨孔隙度变大, 表面含氮和溴官能团增多. 吸附剂M-EG对酸性艳蓝染料废水具有较高的吸附性能, 在pH=1.0及30 ℃条件下对染料的去除率达到94.13%; EG符合二级动力学吸附模型, 用Langmuir等温线方程拟合效果较好; M-EG符合二级吸附动力学方程, 同时符合Langmuir和Freundlich等温吸附模型; M-EG的吸附动力学常数大于EG吸附动力学常数.     

Facile synthesis of bioglass nanospheres for the adsorption of cationic and anionic dyes from aqueous solution

A novel adsorbent, bioglass nanospheres (BGN), has been prepared by a facile process. The BGN were spheres with an amorphous structure and a relatively high specific surface area, as indicated by SEM, transmission electron microscopy, BET, FTIR, and XRD. This paper was aimed at evaluating the adsorption behavior of this new material for the adsorptive removal of cationic (methylene blue, neutral red) and anionic (congo red) dyes from aqueous solution. The effects of the initial dye concentration, contact time, solution pH, and temperature were investigated. The adsorption kinetics showed that the adsorption behavior followed the pseudo-second-order kinetic model. The adsorption isotherm fit well to the Langmuir model. Thermodynamic analyses showed that the adsorption was physisorption, and it was also a spontaneous and endothermic process. The BGN exhibited a good reusability after five consecutive cycles for cationic dyes. In addition, the possible adsorption mechanism was also proposed based on the above experimental results.     

Utilization of industrial waste as a novel adsorbent: Mono/competitive adsorption of chromium(VI) and nickel(II) using diatomite waste modified by EDTA

The adsorption of Cr(VI) and Ni(II) using ethylenediaminetetraacetic acid‐modified diatomite waste (EDTA‐DW) as an adsorbent in single and binary systems was investigated. The EDTA‐DW was characterized using various analytical techniques, including Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, X‐ray diffraction, scanning electron microscopy and energy‐dispersive spectrometry. The adsorption experiment was conducted by varying pH, adsorbent dosage, initial concentration and temperature. In the single system, the sorption data for Cr(VI) fitted the Langmuir isotherm, but the Ni(II) adsorption data fitted well the Freundlich isotherm. The maximum sorption capacity of Cr(VI) and Ni(II) was 2.9 mg g^?1 at pH = 3 and 3.64 mg g^?1 at pH = 8, respectively. The kinetic data for both Cr(VI) and Ni(II) followed well the pseudo‐second‐order kinetic model in single and binary systems. Meanwhile, the extended Langmuir and extended Freundlich multicomponent isotherm models were found to fit the competitive adsorption data for Cr(VI) and Ni(II). In addition, in the binary system, the existence of Ni(II) hindered the adsorption of Cr(VI), but the presence of Cr(VI) enhanced the removal of Ni(II). This study provides some realistic and valid data about the usage of modified diatomite waste for the removal of metal ions.     

Microwave‐synthesized Pepper Peduncle Carbon,Characterization, and Its Adsorption Studies

Adsorption on activated carbon is an efficient method for the removal of toxic dyes. However, since commercially available charcoal is quite expensive, activated carbon obtained from agricultural by‐products may serve as a good replacement. In this study, activated carbon was prepared from pepper peduncle, an agricultural waste product, by microwave activation. The synthesized carbon was characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermal gravimetric analysis techniques. It was then used for the adsorption of methylene blue dye from an aqueous solution, which was studied as a function of the dye concentration, contact time, and temperature. The adsorption data were fitted to Freundlich and Langmuir isotherm models. The adsorption kinetics was studied by employing first‐ and second‐order kinetic models, and it was found that the adsorption of methylene blue on the synthesized activated carbon follows a second‐order kinetic model. Effect of temperature on the adsorption process was studied, and the thermodynamic parameters such as activation energy, change in enthalpy, entropy, and free energy of adsorption were calculated on the basis of the absolute theory of reaction rate expressions. About 99.5–91.8% of the dye was removed for an initial dye concentration in the range 20–100 mg/g in 1 h. Thus the synthesized activated carbon was found to be very efficient in adsorbing the dye.     

Adsorption study for removal of Congo red anionic dye using organo-attapulgite

The organo-attapulgite was prepared using hexadecyltrimethylammonium bromide (HTMAB) with equation equivalent ratio of HTMAB to CEC of attapulgite added and then used as adsorbent for the removal of Congo red (CR) anionic dye from aqueous solution. Adsorbent characterizations were investigated using infrared spectroscopy and X-ray diffraction. The effects of contact time, temperature, pH and initial dye concentration on organo-attapulgite adsorption for CR were investigated. The results show that the amount adsorbed of CR on the organo-attapulgite increase with increasing dye concentration, temperature, and by decreasing pH. The adsorption kinetics was studied with the pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and the rate constants were evaluated. It was found that the adsorption mechanisms in the dye/organo-attapulgite system follow pseudo-second-order kinetics with a significant contribution of film diffusion. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model, and the maximum adsorption capacity was 189.39 mg g⁻¹ for the adsorbent. Kinetic and desorption studies both suggest that chemisorption should be the major mode of CR removal by the organo-attapulgite. The results indicate that HTMAB-modified attapulgite could be employed as low-cost material for the removal of Congo red anionic dye from wastewater.     

A novel green synthesis of Fe3O4 magnetic nanorods using Punica Granatum rind extract and its application for removal of Pb(II) from aqueous environment

We described a novel and eco-friendly approach to remove toxic heavy metal of Pb(II) by using dimercaptosuccinic acid (DMSA) anchored Fe₃O₄ magnetic nanorods (MNRs) which were synthesized via facile method utilizing Punica Granatum rind extract which was a non toxic waste material. The DMSA@Fe₃O₄ MNRs were characterized by X-ray diffraction (XRD), Fourier transformed infrared analysis (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and desorption techniques, and vibrating sample magnetometer (VSM). These DMSA@Fe₃O₄ MNRs have been used for the removal of Pb(II) from aqueous solution. The adsorption isotherm data fitted well with Langmuir isotherm and Freundlich model, the monolayer adsorption capacity was found to be 46.18 mg/g at 301 K. The experimental kinetic data fitted very well with the pseudo-second-order model. The results indicate that the biogenic synthesized DMSA@Fe₃O₄ MNRs act as significant adsorbent material for removal of Pb (II) from aqueous environment.     

Removal of methylene blue by seed-watermelon pulp-based low-cost adsorbent: Study of adsorption isotherms and kinetic models

Based on the abundance of seed-watermelon pulp (SWP) in Xinjiang, China, SWP was employed to prepare low-cost adsorbent toward the removal of methylene blue (MB). The effects of contact time at different initial concentration were studied. The widely used adsorption isotherm models including Langmuir, Freundlich, and Temkin isotherms were employed to depict the adsorption process. The Langmuir isotherm was best fitted to the experimental data. Batch kinetic studies showed that an equilibrium time of 300 minutes was needed for the adsorption. The adsorption properties can be well described by pseudo-second-order kinetic model and the MB uptake was not controlled by intraparticle diffusion mechanism.     

Synthesis of Gd<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>FeO<Subscript>3</Subscript> perovskite-type nanopowders for adsorptive removal of MB dye from water

In the present study, nanoparticles of perovskite-type Gd_0.5Sr_0.5FeO₃ (GSFO) were fabricated by a sol–gel method. A series of analytical techniques were used to characterize the crystallinity, morphology, specific surface area and grain size of GSFO powders. The thermal decomposition process of the complex precursor was examined by means of differential thermal analysis–thermal gravimetric analysis. X-ray diffraction results showed that a single perovskite phase was completely formed after calcination at 700 °C. In addition, transmission electron microscopy images revealed that the average size of the particles is approximately 35.23 nm in diameter. The surface morphology and composition of these nanopowders were also investigated using a scanning electron microscope and an energy dispersive X-ray spectrometer. GSFO nanoparticles showed excellent adsorption efficiency towards methylene blue dye in aqueous solution. The adsorption studies were carried out at different pH values, initial dye concentrations, various adsorbent doses and contact time in batch experiments. The dye removal efficiency was found to be increased with increasing the initial pH of the dye solution, and GSFO exhibited good dye removal efficiency at a basic pH, especially at a pH of 12. Experimental results indicated that the adsorption kinetic data follow a pseudo-second-order rate for the tested dye. The isotherm evaluations revealed that the Redlich–Peterson model attained better fits to the experiment's equilibrium data than the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models.     

Selective and effective adsorption of methyl blue by barium phosphate nano-flake

We report the synthesis of barium phosphate (BP) nano-flake and its adsorption behavior to methyl blue (MB) in aqueous solution. The as-obtained BP nano-flake revealed pure rhombohedral crystal structure. The adsorption capacity of MB onto BP reached 1500mgg(-1). The adsorption equilibrium results fitted well with the Freundlich isotherm model. The adsorption process took less than 30min to reach equilibrium. The adsorption kinetics was elucidated by the pseudo-second-order kinetic equation. It followed 2-stage and 3-stage intra-particle diffusion models for the low and high concentration of dye solutions, respectively. The adsorption of MB using the BP nano-flake was highly selective, compared with the adsorption of other dyes. The interactions between MB and BP were mainly the ionic interaction and hydrogen bonds, which were confirmed by the X-ray photoelectron spectroscopic results and the density functional theory calculations. The BP nano-flake revealed less than 5% decrease in adsorption amount when it was recycled and reused five times. The present work shows that the BP nano-flake is promising for practical applications in MB removal from aqueous solutions.     

Amin-functionalized magnetic-silica core-shell nanoparticles for removal of Hg2+ from aqueous solution

Magnetic nanoparticles with monodisperse shape and size were prepared by a simple method and covered by silica. The prepared core-shell Fe₃O₄@silica nanoparticles were functionalized by amino groups and characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. The synthesized nanoparticles were employed as an adsorbent for removal of Hg²⁺ from aqueous solutions, and the adsorption phenomena were studied from both equilibrium and kinetic point of views. The adsorption equilibriums were analyzed using different isotherm models and correlation coefficients were determined for each isotherm. The experimental data were fitted to the Langmuir–Freundlich isotherm better than other isotherms. The adsorption kinetics was tested for the pseudo-first-order, pseudo-second-order and Elovich kinetic models at different initial concentrations of the adsorbate. The pseudo-second-order kinetic model describes the kinetics of the adsorption process for amino functionalized adsorbents. The maximum adsorption occurred at pH 5.7 and the adsorption capacity for Fe₃O₄@silica-NH₂ toward Hg²⁺ was as high as 126.7 mg/g which was near four times more than unmodified silica adsorbent.