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.     

地质聚合物微球的制备及对染料的吸附

以偏高岭土和改性水玻璃为原料，采用分散悬浮固化法制备偏高岭土基地质聚合物微球（GM）。使用扫描电子显微镜、比表面积及孔径分布测试仪、傅里叶变换红外光谱仪和X射线粉末衍射仪对其进行结构表征，并研究了GM对亚甲基蓝的吸附性能。结果表明：GM对亚甲基蓝的吸附基本符合准二级动力学模型和Langmuir吸附等温线模型，333 K时最大理论吸附量为100.1 mg/g。GM对亚甲基蓝的吸附是自发吸热过程。使用后的GM在5次循环利用后，GM对MB的去除率仍然可达81.56%，易于回收和再生。分析了GM对不同阴阳离子型染料的吸附效果，结果表明，GM对阳离子型染料具有选择性吸附。GM是一种低价、有效、绿色、可循环利用的吸附剂，可用于去除水中阳离子型染料污染物。     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

γ‐radiation‐induced preparation of polyamidoxime resins and their adsorption of methyl violet

Poly(acrylic acid–amidoxime) [P(AA–AO)] and poly(maleic acid–amidoxime) [P(MA–AO)] resins were prepared by the γ‐radiation‐induced copolymerization of acrylonitrile with acrylic acid and maleic acid, respectively. The obtained resins were amidoximated by reaction with hydroxylamine. The prepared resins were used for the removal of methyl violet (MV) dye from aqueous solutions. Batch adsorption studies were made by the measurement of the effects of pH, the amount of adsorbent, the contact time, and the adsorbate concentration. The adsorption isotherm of MV onto P(AA–AO) and P(MA–AO) was determined at 25°C with initial MV dye concentrations of 10–70 mg/L. The equilibrium data were analyzed with the Langmuir and Freundlich isotherm models. The equilibrium process was described well by the Langmuir isotherm model with maximum adsorption capacities of 398.4 and 396.8 mg/L for P(AA–AO) and P(MA–AO), respectively. The kinetics of adsorption of MV onto P(AA–AO) and P(MA–AO) are discussed. The pseudo‐second‐order kinetic model described the adsorption of MV onto P(AA–AO) and P(MA–AO) very well. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Anionic dye adsorption characteristics of surfactant‐modified coir pith,a ‘waste’ lignocellulosic polymer

The surface of coir pith, an agricultural solid waste, was modified using a cationic surfactant hexadecyltrimethylammonium bromide. Adsorption of anionic dyes on surfactant‐modified coir pith was investigated in a series of batch adsorption experiments. Two anionic dyes, acid brilliant blue (acid dye) and procion orange (reactive dye), were used in the adsorption studies. The effect of process variables such as contact time, concentration of the dyes, adsorbent dose, temperature, and pH were studied in order to understand the kinetic and thermodynamic parameters of the process. The kinetics of adsorption obeyed the second‐order rate equation. The equilibrium adsorption data were fitted into the Langmuir and Freundlich isotherms. It was found that modified coir pith yielded adsorption capacities of 159 and 89 mg/g for acid brilliant blue and procion orange, respectively. Mechanisms involving ion exchange and chemisorption might be responsible for the uptake of dyes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1538–1546, 2006     

Preparation and Application of a Novel Functionalized Coconut Coir Pith as a Recyclable Adsorbent for Phosphate Removal

Abstract

This study was to develop a new adsorbent, Iron(III) complex of an amino-functionalized polyacrylamide-grafted coconut coir pith (CP), a lignocellulosic residue, for the removal of phosphate from water and wastewater. The kinetics of adsorption follows a pseudo-second-order model. The equilibrium sorption capacity of 96.31 mg/g was determined at 30°C from the Langmuir isotherm equation. Complete removal of 16.4 mg/L phosphate in 1 L of fertilizer industry wastewater was achieved by 1.5 g/L AM-Fe-PGCP at pH 6.0. The acid treatment (0.1 M HCl) and re-introduction of Fe³⁺ lead to a reactivation of the spent adsorbent and can be reused through many cycles of water treatment and regeneration without any loss in the adsorption capacity.     

Starch/rice husk ash based superabsorbent composite: high methylene blue removal efficiency

Superabsorbent hydrogels composites based on the biopolymer starch (ST) and rice husk ash (RHA) were successfully developed and tested towards the removal of methylene blue (MB), a cationic dye. RHA content hit the morphology, mechanical and water uptake properties of the composite. Batch adsorption experiments, carried out under pH 5 at 33 °C and with 2000 mg L^?1 as the initial concentration of MB, showed that at 5 wt% RHA the composite exhibited a remarkable adsorption capacity reaching up to 1906.3 mg g^?1 within 60 min. The adsorption kinetics followed the pseudo-second-order model and intraparticle diffusion was involved in this process. The Langmuir adsorption isotherm suggested a monolayer formation and spontaneous process. Thermodynamic parameters confirmed the spontaneity of the adsorption and suggested electrostatic interaction among the cationic dye molecules and the anionic adsorption sites on the adsorbent surface. FTIR analysis confirmed the adsorption process occurs via electrostatic mechanism associated with hydrophobic interactions. The adsorbents showed reusability with slight loss of adsorption capacity in five consecutive adsorption/desorption cycles. These results demonstrate ST/RHA superabsorbent composite as a low-cost, eco-friendly, robust and powerful adsorbent material for wastewater remediation.     

Adsorption behavior of cationic dyes on citric acid esterifying wheat straw: kinetic and thermodynamic profile

The kinetic and thermodynamic behaviors of cationic dye adsorption onto citric acid esterifying wheat straw (EWS) from aqueous solution were investigated. Two cationic dyes, methylene blue (MB) and crystal violet (CV) were selected as adsorbates. The kinetic and thermodynamic parameters of dye adsorption were examined with a batch system by changing various experimental factors (e.g. initial pH, EWS dosage, dye concentration, contact time, temperature). The MB and CV removal ratios came up to the maximum value beyond pH 4. The 2.0 g/L or up of EWS could almost completely remove MB and CV from 250 mg/L of dye solution. The adsorption percentages of MB and CV kept above 95% over a range from 50 to 350 mg/L of dye concentration when 2.0 g/L of EWS was used. The isothermal data followed the Langmuir model. The adsorption processes could be described by the pseudosecond-order kinetic model. The dual linear plots of intraparticle diffusion indicated that two intraparticle diffusion steps occurred in the dye adsorption processes. The thermodynamic study indicated that the adsorptions of dyes were spontaneous and endothermic. High temperatures favored the adsorption processes.     

Adsorption of Methylene Blue on Poly (Methacrylic Acid) Modified Chitosan and Photocatalytic Regeneration of the Adsorbent

The preparation of poly(methacrylic acid) modified chitosan microspheres (PMAA-GLA-CTS) and its application for the removal of cationic dye, methylene blue (MB), in aqueous solution in a batch system were described. The modified chitosan was characterized using FTIR and XPS analysis. The effects of the pH of the solution, contact time, and initial dye concentration were studied. The adsorption capacity of the microspheres for MB increased significantly after the modification as a large number of carboxyl groups were introduced. The equilibrium process was better described by the Langmuir rather than the Freundlich isotherm. According to the Langmuir equation, the maximum adsorption capacity was 1 g · g^?1 for MB. Kinetic studies showed better correlation coefficients for a pseudo-second-order kinetic model, confirming that the sorption rate was controlled by a chemisorption process. Photocatalytic regeneration of spent PMAA-GLA-CTS using UV/TiO₂ is effective. Further, the regenerated PMAA-GLA-CTS exhibits 90% efficiency for a subsequent adsorption cycle with MB aqueous solutions.     

不同无机酸对聚吡咯/TiO2复合物的吸附性能影响

考察了不同无机酸对PPy/TiO₂复合物吸附性能的影响。首先分别在HNO₃、H₂SO₄和H₃PO₄体系中合成了聚吡咯(PPy)/TiO₂复合物(分别简写为N-PPy/TiO₂、S-PPy/TiO₂和P-PPy/TiO₂)。以红外光谱、热重分析、Zeta电位、比表面积分析和扫描电镜等测试方法对复合物的物理化学性能进行了表征。接着以几种合成的复合对阴离子染料酸性红G和阳离子染料亚甲基蓝进行吸附研究,发现无机酸对合成的复合物的吸附性有较大的影响。几种复合物均可在30min内达到吸附平衡,并且可以重复使用6次以上吸附量没有明显的降低。其中S-PPy/TiO₂的吸附性能最好,其对ARG和MB的最大吸附量分别达到218.34mg/g和314.68mg/g。复合物对染料的吸附过程符合准二级动力学模型和Langmuir吸附等温式。对S-PPy/TiO₂进行吸附热力学研究表明,其对染料的吸附过程为熵增的自发过程。     

Anion Exchange Resins of Tri-n-butyl Ammonium Functional Groups for Dye Baths and Textile Wastewater Treatment

Effectiveness of two strongly basic anion exchange resins of the gel (Dowex PSR-2) and macroporous structure (Dowex PSR-3) was compared in order to remove three hazardous dyes such as C.I. Acid Orange 7 (AO7), C.I. Reactive Black 5 (RB5), and C.I. Direct Blue 71 (DB71) contained in water and textile wastewaters. Batch adsorption experiments were carried out to analyze the effect of phase contact time, initial dye concentration, and the presence of auxiliary materials (anionic and cationic surfactants, Na₂CO₃, and Na₂SO₄). The Langmuir model better described the adsorption process of the dyes onto both resins than the Freundlich model. The monolayer adsorption capacities (q_e) of Dowex PSR-3 were calculated as 336.4 mg/g for AO7, 317.9 mg/g for RB5, and 150.4 mg/g for DB71 at 25^°C. Dowex PSR-2 of the gel structure is characterized by considerably lower values of q_e (50.1 mg/g for AO7, 17.2 mg/g for RB5, and 9.7 mg/g for DB71). Of special importance are high values of the working ion exchange capacities of Dowex PSR-3 determined from the breakthrough curves towards AO7 and RB5 equal to 127 and 85 mg/cm³, respectively. The pseudo second-order kinetic model described the experimental sorption data better than the pseudo first-order model. Methanol addition to the 1 M HCl and 1 M NaOH solutions improved the effectiveness of dye desorption.     

Synthesis,characterization and application of acid and alkaline activated volcanic ash-based geopolymers for adsorptive remotion of cationic and anionic dyes from water

In this work, two geopolymers were prepared by acid activation (GPAc) and alkaline activation (GPAl) approaches using volcanic ash (VA) as the precursor material. The geosorbents were characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared and Brunauer-Emmett-Teller (BET) surface area analyses and their comparative adsorptive potential for anionic (Eriochrome Black T/EBT) and cationic (methylene blue/MB) dyes from water is herein reported for the first time. GPAl and GPAc had 74.47 and 42.75 m²/g BET surface areas, respectively. Equilibrium adsorption data were described by the isotherm models in the order Freundlich > Sips > Langmuir model. Relative to acid activation (GPAc), alkaline activated geopolymer (GPAl) had the highest adsorption capacity for both MB and EBT, estimated at 952 mg/g and 251 mg/g, respectively, consistent with the BET surface areas. The adsorption rates were best described by the pseudo-second order (PSO) kinetic model. GPAl exhibited faster adsorption kinetics than GPAc as denoted by the adsorption half-life, t_1/2. The thermodynamic functions indicated that the adsorption of both MB and EBT onto the geopolymers was spontaneous, exothermic and feasible. The adsorption was pH-dependent implying electrostatic interactions is the dominant driving mechanism of adsorption. The results show that alkaline activated geopolymers are better sorbents for dye removal than acid activated geopolymers under the examined conditions.     

Coconut (Cocos nucifera) Shell Based Activated Carbon for the Removal of Malachite Green Dye from Aqueous Solutions

The adsorption of malachite green (MG) dye using coconut shell based activated carbon (CSAC) was investigated. Operational factors such as the effect of pH, initial dye concentration, adsorbent dosage, contact time, and solution temperature on the adsorption process were studied. Solution pH strongly affected the chemistry of both the dye molecule and CSAC in solution. Optimum dye removal was obtained at pH ≥ 8.0. Equilibrium was reached in 120 minutes contact time. The Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models were used to evaluate the adsorption data. The adsorption data fitted the Langmuir model most with maximum adsorption monolayer coverage of 214.63 mg/g. Pseudo-first-order, pseudo second-order, and intraparticle diffusion models were also used to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each model were calculated and discussed. Thermodynamic parameters such as ΔG⁰, ΔH⁰, and ΔS⁰ were evaluated and it was found that the sorption process was feasible, spontaneous, and exothermic in nature. The mean free energy obtained from D-R isotherm suggests that the adsorption process follows physiosorption mechanism. The results showed that coconut shells could be employed as a low-cost precursor in activated carbon preparation for the removal of MG dye from wastewaters.     

Polymer‐derived ceramic adsorbent for pollutant removal from water

Polymer‐derived ceramic components (SiOC, sample W) were produced from preceramic polymer mixture and a catalyst. After curing and pyrolysis, some of the samples etched by hydrofluoric acid to obtain carbonaceous SiOC (C‐rich SiOC, sample W‐HF). W and W‐HF were tested as an adsorbent material to remove both heavy‐metal ions (Cr (III), Pb (III), and Cd (II)) and cationic dyes (Methylene Blue (MB), Rhodamine B (RB), and Crystal Violet (CV)) from aqueous solutions. HF‐treated high surface area SiOC samples had quite high adsorption affinity for cationic dyes. According the Langmuir isotherm model the maximum dye uptake values were found to be around to 50 mg/g for sample W, whereas those for sample W‐HF ranged from 104 to 186 mg/g. Regeneration studies were conducted both by heat treatment and leaching, high recovery yields (always above 97%) of MB adsorption were obtained.     

Adsorption of Congo Red from Aqueous Solutions Using Chitosan Hydrogel Beads Formed by Various Anionic Surfactants

The structural organization of chitosan hydrogel beads (CSBs) formed by various anionic surfactants, sodium dodecyl sulfate (SDS), sodium decyl sulfate (DS), dodecyl benzenesulfonic acid sodium salt (SDBS), and dioctyl sulfosuccinate sodium salt (DSS), and their applications as adsorbents for environmental purifications were investigated using Congo red (CR) as a model dye. The adsorption capacities of CSB as a function of surfactant concentration revealed that CSBs formed by 5 g/L anionic surfactant were the most effective for CR adsorption. The structure of CSBs and their adsorption capacities for CR depend on the nature of anionic surfactants. The maximum adsorption capacities of CSB_SDS, CSB_DS, CSB_SDBS, and CSB_DSS obtained from the Langmuir isotherm model were 186.02, 209.28, 207.25, and 113.83 mg/g, respectively, indicating that CSB_DS was the best adsorbent for CR.     

Adsorption Behavior of Methylene Blue from Aqueous Solution by the Hydrogel Composites Based on Attapulgite

A series of carboxymethyl cellulose-g-poly (acrylic acid)/attapulgite hydrogel composites were synthesized for the removal of cationic dye methylene blue. Various factors affecting the uptake behavior were investigated. Adsorption rate of the hydrogel was quite fast, and adsorption equilibrium could be reached within 30 min. Adsorption kinetics well followed the pseudo-second-order equation for all systems. The Langmuir isotherm was found to best represent the data for the dye uptake. Even when 20 wt% attapulgite was introduced into the hydrogel, the corresponding maximum adsorption capacity reached 1979.48 mg/g at 30°C. The as-prepared adsorbents exhibited excellent affinity for the dye, and can be applied to treat wastewater containing basic dyes.     

Poly(acrylic acid)/poly(acrylamide) hydrogel adsorbent for removing methylene blue

Cationic dye can cause severe damage to the environment due to their refractory degradation, complex composition and strong stability. Hydrogels as adsorbents have been widely used to treatment the wastewater with dyestuff for their low prices, simple operations, and high efficiency. This work uses poly(acrylic acid) (PAA)/poly(acrylamide)(PAM)/calcium hydroxide nanoparticles (CHN) polymeric hydrogel absorbent to eliminate methylene blue (MB) dye. First, PAM/PAA/CHN hydrogel is produced through copolymerization of acrylic acid monomer and acrylamide monomer using inorganic CHN as cross-linker. And then, the adsorption performance of such PAM/PAA/CHN hydrogel adsorbent for adsorbing MB dye is explored at different conditions including pH, contacting time, adsorbent dosage, initial concentration of MB, and temperature. A maximum adsorption capability for adsorbing MB reaches 1,056 mg/g. Furthermore, the pseudo-first-order mode and Langmuir isotherm model can well describe adsorption behavior of MB dye onto such PAA/PAM/CHN hydrogel adsorbent. Thereby, as-prepared PAA/PAM/CHN hydrogel could be a potential adsorbent for eliminating organic dyes from wastewater.     

Synthesis of an ordered mesoporous carbon with graphitic characteristics and its application for dye adsorption

An ordered mesoporous carbon (OMC) was prepared by a chemical vapor deposition technique using liquid petroleum gas (LPG) as the carbon source. During synthesis, LPG was effectively adsorbed in the ordered mesopores of SBA-15 silica and converted to a graphitic carbon at 800 °C. X-ray diffraction and nitrogen adsorption/desorption data and high-resolution transmission electron microscopy (HRTEM) of the OMC confirmed its ordered mesoporous structure. The OMC was utilized as an adsorbent in the removal of dyes from aqueous solution. A commercial powder activated carbon (AC) was also investigated to obtain comparative data. The efficiency of the OMC for dye adsorption was tested using acidic dye acid orange 8 (AO8) and basic dyes methylene blue (MB) and rhodamine B (RB). The results show that adsorption was affected by the molecular size of the dye, the textural properties of carbon adsorbent and surface-dye interactions. The adsorption capacities of the OMC for acid orange 8 (AO8), methylene blue (MB) and rhodamine B (RB) were determined to be 222, 833, and 233 mg/g, respectively. The adsorption capacities of the AC for AO8, MB, and RB were determined to be 141, 313, and 185 mg/g, respectively. The OMC demonstrated to be an excellent adsorbent for the removal of MB from wastewater.     

Low-cost,green synthesis and adsorption properties for dyes of novel porous gangue/palygorskite composite microspheres

In this work, gangue/palygorskite composite microspheres were fabricated through spray drying process and activated by calcination treatment. Its microstructure and adsorption capacity for the removal of dye (MB) were also studied, systematically. Results showed that kaolinite, α-quartz and palygorskite were the major phases in microspheres after proper calcination (lower than 900°C). BET-specific surface area of the microspheres reached the maximum value of 62.23 m²/g at 700°C, and then decreased with further increasing the heating temperature. In general, composite microspheres showed the largest adsorption capacity of MB after heat-treated at 700°C. The q_max of MB onto microspheres was 29.9-51.9 mg/g. The adsorption process of MB onto microspheres was well described by both the pseudo-second-order kinetic and Langmuir isotherm model. The composite microspheres also had extraordinary recyclability. This novel microsphere could be employed as a candidate for novel absorbent and filter medium in the practical application for dye treatment in industrial applications.