Preparation of hemicellulose‐g‐poly(methacrylic acid)/carbon nanotube composite hydrogel and adsorption properties

An organic–inorganic composite hydrogel was prepared based on hemicellulose and multi‐wall carbon nanotubes. The effects of hydrogel amount, initial concentration, contact time, and salt concentration on the adsorption performance of the prepared hydrogels were observed using methylene blue as a model hazardous material. The results indicated that the adsorption kinetic of methylene blue on the prepared adsorbent was well fitted to the pseudo‐second‐order kinetic model and the adsorption isotherm conformed to the Freundlich model. Removal percentage of methylene blue increased with increased adsorbent amount and kept higher than 98% when adsorbent amount was above 6 g L⁻¹. Adsorption amount of methylene blue on the prepared adsorbent also increased when increasing initial concentration over the range from 50 to 500 mg L⁻¹. Both of adsorption amount and removal percentage increased with an increase in the contact time, and removal efficiency obviously deteriorated as salt concentration increased. All obtained results reported that the prepared composite hydrogel would have an application prospect in water treatment. POLYM. COMPOS., 35:45–52, 2014. © 2013 Society of Plastics Engineers     

The study of the potential capability of sugar beet pulp on the removal efficiency of two cationic dyes

This study utilizes sugar beet pulp as a low-cost absorbent to remove two different cationic dyes, methylene blue and safranin, in aqueous solutions. The effects of operational parameters on the efficiency of dye removal including pH, adsorbent mass, initial dye concentration and contact time have been investigated. All sets of experiments were carried out in batch mode. For both dyes, the maximum absorption was reached at pH 10 while point zero charge was known to be at pH 6. Boehm method showed that the amount of the acidic and basic groups have been 0.4075 mmol g⁻¹ and 0.0089 mmol g⁻¹, respectively. Freundlich and Langmuir models were used to analyse the obtained experimental data. In comparison, Langmuir model was understood to be a better fit for the experimental data than Freundlich model. Pseudo first-order and pseudo second-order models were used to determine the adsorption kinetics and it was observed that pseudo second-order model was the most suited model for both dyes. The equilibrium state for both dyes was reached after 210 min of the absorption experiment with more than 93% removal of dyes. The absorption capacities were found to be 211 mg/g and 147 mg/g for methylene blue and safranin, respectively.     

Enhanced selective adsorption of cation organic dyes on polyvinyl alcohol/agar/maltodextrin water-resistance biomembrane

In this study, we designed a novel hydrogel composite membrane based on the combination of polyvinyl alcohol (PVA), agar, and maltodextrin through a facile solution-casting router. From Fourier-transform infrared spectroscopy, contact angle, scanning electron microscopy, and swelling analyses, the formation of hydrogen bonds between surface functional groups of PVA, agar, and maltodextrin was confirmed. As a result, the PVA/agar/maltodextrin membranes exhibited a more hydrophobic nature compared with pure PVA. The thermal stability and integrity of such obtained composite membranes were also elucidated by the evaluation of thermogravimetric analysis and mechanical behavior. Besides, the composite membrane exhibited high selective adsorption for cationic dyes, namely 20.2 mg g⁻¹ for methylene blue and 19.17 mg g⁻¹ for crystal violet at initial dye concentration of 100 mg/L, an adsorbent dosage of 0.1 g, contact time of 180 min, and solution pH 7, while anionic dyes such as congo red and methyl orange are approximately zero. The adsorption kinetics and isotherm of the as-prepared composite membranes were well fitted to the pseudo-second-order and Temkin model. The effect of factors, including contact time, solution pH, PVA content, and initial dye concentration on the adsorption capacity of the as-prepared composite membrane was also investigated in detail. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48904.     

Preparation and application of glycidyl methacrylate and methacrylic acid monomer mixture‐grafted poly(ethylene terephthalate) fibers for removal of methylene blue from aqueous solution

A novel fibrous adsorbent that grafts glycidyl methacrylate (GMA) and methacrylic acid (MAA) monomer mixture onto poly(ethylene terephthalate) (PET) fibers was used for removal of methylene blue (MB) in aqueous solutions by a batch equilibration technique. The operation parameters investigated included, pH of solution, removal time, graft yield, dye concentration, and reaction temperature. The adsorption rate of MB is much higher on the MAA/GMA‐grafted PET fibers than on the ungrafted PET fibers. MB was removed 99% the initial dye concentration at 10 mg L⁻¹ and 93% at 200 mg L⁻¹ by monomers mixture‐grafted PET fibers. Pseudofirst order and pseudosecond order kinetic equations were used to examine the experimental data of different graft yield. It was found that the pseudosecond order kinetic equation described the data of dye adsorption on fibrous adsorbent very well. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm models. The data was that Freundlich isotherm model fits the data very well for the dyes on the fibers adsorbent. The dye adsorbed was easily desorbed by treating with acetic acid/methanol mixture (50% V/V) at room temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Facile preparation of agaraldehyde chitosan-based composite beads as effectual adsorbent especially towards amido black

Agaraldehyde and chitosan (CHI) functional beads as dye adsorbent were prepared under aqueous medium under ambient temperature and used for removing seven dyes from aqueous solutions. The resulting porous CHI-A_ald (R-A_ald-CHI) bio-beads were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscope. The dye removal efficiency was studied using seven dyes (amido black [AB], bromophenol blue, crystal violet, bismarck brown, cotton blue, methyl orange, methylene blue), but detail study was done on AB. AB adsorption was followed the Langmuir-isotherm and pseudo-second order kinetics. The effects of adsorption parameters were investigated, and maximum AB 1506 mg/g was adsorbed under the optimum conditions. The linear and nonlinear forms of Langmuir and Freundlich isotherms and two kinetic models pseudo-first-order and pseudo-second-order were studied. The results show that adsorption follow both isotherm model while for kinetics of adsorption follow pseudo-second-order. The results of this work showed that R-A_ald-CHI was encouraging adsorbent to remove dyes from wastewater, especially AB.     

Citric acid modified waste cigarette filters for adsorptive removal of methylene blue dye from aqueous solution

Waste cigarette filters (CFs) were recycled and modified with a nontoxic and low-cost citric acid (CA). The modified CFs were employed in the adsorptive removal of methylene blue (MB) dye from aqueous medium. The influence of pH, contact time, initial dye concentration, and adsorbent dose on adsorption of MB dye was evaluated. The adsorption studies were conducted by employing linear and nonlinear Langmuir and Freundlich isotherm models. The adsorption capacity of CF obtained through linear and nonlinear Langmuir model were 88.02 and 94 mg g⁻¹, which improved up to 163.93 and 168.81 mg g⁻¹, respectively, after the introduction of functional groups in CF-CA. The adsorption kinetics data were well fitted by pseudo-second order kinetics with coefficient of regression (R²) closed to unity. The removal efficiency of CF-CA was 97% at equilibrium time of 4 h. Desorption studies indicated that CF-CA could be regenerated by using HCl (0.1 M) and desorption efficiency was up to 82% upon second cycle of reusability experiment. This study proposed a green and economical use of recycled CFs in dyes wastewater treatment, simultaneously reducing the negative environmental impact due to their improper disposal.     

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.     

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     

NaOH改性花生壳对亚甲基蓝染料吸附性能的研究

花生壳用5%的NaOH溶液改性作吸附剂处理亚甲基蓝染料废水,考察pH值、吸附剂投加量、染料浓度和温度及吸附时间对染料吸附性能的影响。结果表明,吸附最佳的工艺条件为:温度25℃,吸附剂投加量0.3 g,亚甲基蓝的初始浓度3.5 g/mL,反应时间135 min,pH值7。此时改性花生壳对亚甲基蓝的吸附率达99.57%。     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

瓜子壳和花生壳吸附去除亚甲基蓝染料的影响研究

试验以农业固体废弃物花生壳、瓜子壳为生物吸附材料,以亚甲基蓝染料为吸附对象,考察不同条件(如吸附剂用量、溶液pH值和吸附时间等)对亚甲基兰染料吸附效果的影响,结果表明,吸附剂量为2.0 g时,瓜子壳和花生壳对染料的吸附效果较好,均能达到吸附平衡;染料溶液在弱酸或碱性条件下,有利于花生壳和瓜子壳对亚甲基蓝的吸附;花生壳和瓜子壳对亚甲基蓝的吸附均在30 min内达到饱和。而瓜子壳对溶液中亚甲基兰染料的吸附能力要高于花生壳的吸附能力,可作为含亚甲基兰染料印染废水的处理材料。     

Microfiltration of cationic dyes using nano-clay membranes

Water resources cover 70% of earth surface with only 3% as fresh and the remaining frozen or unavailable. As a result, water and wastewater treatment have attracted a great deal of attention during last decades. Among various pollutants, dyes in textile wastewaters can have serious impacts on the environment. In the present study, low-cost ceramic nano-clay microfiltration membranes with low sintering temperature were fabricated via dry pressing, with natural zeolite as pore former. Flat disks were fabricated by sintering a mixture with various proportions of clay, zeolite and polyethylene glycol at 900 °C and characterized using FE-SEM, open porosity test, zeta potential, water permeability and acid-base treatment. Also, Membrane porosity was enhanced by increasing the zeolite content reaching 30.2% at 30 wt% and then decreased. The 30% zeolite membrane was selected for microfiltration of methylene blue, crystal violet and methyl orange from aqueous solutions. Initial and time filtered solution concentrations for each dye were measured using a UV–visible spectrophotometer. Methylene blue and crystal violet are cationic dyes due to the presence of NC(CH)₃ ⁺ while SO₃^- makes methyl orange anionic. The membrane had negative charge at pH = 6, suggesting adsorption of cationic dyes as the removal mechanism. 95.55% removal of crystal violet was obtained for the 54 mg L⁻¹ solution at 1 bar and 90.23% removal of methylene blue was obtained at optimal conditions with a 35.76 mg L⁻¹ concentration and 1.5 bar transmembrane pressure. However, less than 10% methyl orange removal was obtained, due to its negative charge. Membranes can be recovered completely by eliminating the adsorbed dyes via heat treatment at 300 °C for 1 h. The results approve the as-fabricated clay membranes cost-effective with high rejection of cationic dyes.     

High-performance heterocyclic para-aramid aerogels for selective dye adsorption and thermal insulation applications

The high-performance polymer para-aramid (PPTA) is discovered to gel too soon during the polymerization process, resulting in poor processing performance. In this work, a homogeneous polymer solution containing heterocyclic para-aramid (HPPTA) was successfully synthesized by introducing 2,4-aminophenyl-5-aminobenzimidazole groups into the molecular chains of PPTA, and then HPPTA aerogel was prepared using a supercritical drying technique that took advantage of the HPPTA solution's excellent property of slow gelation. When the HPPTA polymer mass fraction was 1 wt%, the aerogel had the lowest density of 0.086 g cm⁻³ with a BET specific surface area of 376.59 m² g⁻¹. The HPPTA-2 aerogel had better adsorption performance for anionic dye methyl orange, with a maximum adsorption capacity of 319.47 mol g⁻¹; however, its adsorption capacity for cationic dye methylene blue and neutral dye dimethyl yellow was very low, at only 19.68 and 0 mol g⁻¹, respectively. The selective adsorption ability of HPPTA aerogel made it a simple and scalable platform for removing anionic dyes from water solutions. Furthermore, the HPPTA aerogel has outstanding thermal properties for thermal insulation applications in severe environments due to the synergistic effect of the 3D porous structure inside the aerogel and the exceptional thermal stability of the HPPTA.     

Transformation of Mytella falcata residual shell into CaAl/LDH adsorbent: Removal of methyl orange and methylene blue dyes

This study analyzed the viability of using malacoculture residue (Mytella falcata) to produce layered double hydroxides (LDHs) and for its subsequent use as an adsorbent. The CaAl/LDH-RE material was produced with calcium oxide from the residue and the CaAl/LDH-AP was produced with a commercial reagent. Both were used to remove methyl orange (MO) and methylene blue (MB) dyes. The CaAl/LDH-RE presented a surface area of 28.54 m² g⁻¹, being 65.62% larger than the CaAl/LDH-AP material (17.23 m² g⁻¹). The adsorbents showed mesopores distributed on a surface formed by plates in the form of hexagonal sheets arranged in an overlapping manner. The dosage of 0.05 g L⁻¹ obtained the removal of 95% and 97% for MO, while for MB it was 94% and 93% using the adsorbents LDH/CaAl-AP and LDH/CaAl-RE, respectively. The system reached equilibrium at 90 min for MO and 120 min for MB. The pseudo-second order model well represented the kinetic data reaching 11.36 mg g⁻¹ (CaAl/LDH-RE) and 8.42 mg g⁻¹ (CaAl/LDH-AP) for MO, and 4.47 mg g⁻¹ (CaAl/LDH-RE) and 4.14 mg g⁻¹ (CaAl/LDH-AP) for MB. The Freundlich model better represented the isothermal data, where the temperature exerted little influence. Adsorbents showed similar removal percentages in real and synthetic matrices. The LDH/CaAl-RE can be applied in up to 3 cycles, maintaining its adsorption capacity. These results corroborate the use of MFW to produce CaAl/LDH-RE, which can be used for the efficient removal of organic pollutants in an aqueous solution.     

The use of chromium waste sludge for the adsorption of colour from dye effluent streams

Adsorption studies show that chromium hydroxide precipitates can be used for the removal of methylene blue, reactive blue, congo red and disperse orange dyes from aqueous media. Three different mechanisms are involved: attraction of positive surface charges on the precipitate at low pH for dye anions (reactive blue and congo red); attraction of negative surface charges on hydroxide at high pH for dye cations (methylene blue), and dye particle entrapment for the neutral disperse orange. The point of zero charge of the chromium hydroxide precipitate based on the dye adsorption studies is pH 10.5. The changes in the surface charge of such precipitates with pH can be used to achieve the removal of any charged dye species. © 2002 Society of Chemical Industry     

Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

Removal of acid dyes from aqueous solutions using a new eco-friendly nanocomposite of CoFe2O4 modified with Tragacanth gum

A new composite of cobalt ferrite and Tragacanth gum (TG) was developed and applied to remove methyl orange (MO) and methyl red (MR) from wastewater samples simultaneously. The results showed that the presence of TG improved the capability of cobalt ferrite in removing the pollutants in considerably. The adsorption properties and surface morphology of the sorbent were compared with those of bare cobalt ferrite, TG, and TG grafted copolymer. The properties of the adsorbents were studied using Fourier transform infrared, scanning electron microscope, transmission electron microscope, X-ray diffraction, and vibrating sample magnetometer, and the effects of different factors such as the amount of the adsorbent, sample pH, contact time, and initial concentration were also evaluated and optimized through response surface methodology using central composite design. The optimal conditions for the adsorption of both dyes (100 mg L⁻¹ as the concentration) were pH of 4.0, adsorbent dose of 0.5 mg mL⁻¹, and contact time of 110 min. Under these conditions, the MO and MR adsorption processes were found to follow pseudo-second-order kinetic model. The equilibrium adsorption data followed the Langmuir isotherm and the highest adsorption capacity was determined to be 336 and 387 mg g⁻¹ for MO and MR, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48605.     

Removal of methylene blue dye from aqueous solution by activated carbon prepared from cashew nut shell as a new low-cost adsorbent

Methylene blue dye was adsorbed on an adsorbent prepared from cashew nut shell. A batch adsorption study was carried out with variable adsorbent amount, initial dye concentration, contact time and pH. Studies showed that the pH of aqueous solutions affected dye removal as a result of removal efficiency increased with increasing solution pH. The experimental data were analyzed by the Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan, Toth, Temkin, Sips and Dubinin-Radushkevich models of adsorption using MATLAB 7.1. The experimental data yielded excellent fits within the following isotherm order: Redlich-Peterson>Toth>Sips>Koble-Corrigan>Langmuir>Temkin>Dubinin-Radushkevich>Freundlich, based on its correlation coefficient values. Three simplified kinetic models including a pseudofirst-order, pseudo-second-order and intraparticle diffusion equations were selected to follow the adsorption process. It was shown that the adsorption of methylene blue could be described by the pseudo-second-order equation. The results indicate that cashew nut shell activated carbon could be employed as a low cost alternative to commercial activated carbon in the removal of dyes from wastewater.