Methylene blue removal from aqueous solution by magnetic clinoptilolite/chitosan/EDTA nanocomposite

In this study, clinoptilolite as a natural zeolite which was magnetized using precipitation of maghemite nanoparticles was coated by chitosan and then modified by thylenediamine tetra-acetic acid to add functional groups and its performance in the removal of toxic methylene blue from aqueous solution was investigated. Synthesized magnetic nanocomposite was characterized by VSM, XRD, SEM, and FTIR analyses. The saturation magnetization of the final nanocomposite was obtained as 22.2 emu/g. In addition, the factors affecting adsorption process and its optimization were investigated using response surface methodology and central composite design. Data obtained by different isotherm, adsorption kinetic and thermodynamic models were also studied. The results showed good agreement of these data with the Freundlich isotherm model (R ² = 0.99), and it was found that adsorption follows the second-order kinetics model (R ² = 1). Negative values of ΔG and positive values of ΔH obtained from this adsorption thermodynamic study revealed that the methylene blue adsorption process is exothermic and spontaneous. The optimum conditions to ensure maximum adsorption efficiency were determined, and included pH = 5.54, adsorbent amount of 0.03 g, temperature of 31.18 °C, and initial solution concentration of 16.21 mg/l which resulted in a removal efficiency of 99.44%. The results indicated that this nanocomposite can be used as a proper adsorbent for adsorbing methylene blue and other dye contaminants.     

Amoxicillin removal from aqueous matrices by sorption with almond shell ashes

The adsorption of the antibiotic amoxicillin at low concentration levels (µg?L^?1 order) from aqueous solution on almond shell ashes has been investigated, either by kinetic or equilibrium assays. The effect of the adsorbent amount, initial concentration of the antibiotic, particle diameter (d_p) and temperature were considered to evaluate the adsorption capacity of the adsorbent. The results showed that amoxicillin sorption is dependent on these four factors. The adsorption process was relatively fast and equilibrium was established in about 12 hours. The optimum parameters for an initial concentration of 450?µg?L^?1 were 50?mg of adsorbent, 303?K and d_p?<?600?µm. A comparison of kinetic models showed that pseudo-second order kinetics provides the best correlation of the experimental data. Isotherm data adjusted better to Langmuir equation, with an adsorption capacity of 2.5?±?0.1?mg?g^?1 at 303?K. The desorption process was also evaluated (maximum efficiency of 5%). Thermodynamic parameters were calculated and the negative value of ΔH⁰ and ΔG⁰ showed that adsorption was exothermic and a spontaneous process.     

Structural and adsorption behaviour of ZnO/aminated SWCNT-COOH for malachite green removal: face-centred central composite design

In this study, an effective adsorbent was synthesized to remove malachite green (MG), which is one of the toxic dyes. Firstly, single walled carbon nanotube with carboxylated acid (SWCNT-COOH) was functionalized with diethylenetriamine and a new nanocomposite was obtained using nano zinc oxide (ZnO) powder. The effects of pH (3–7), the amount of adsorbent (5–15 mg) and the initial concentration (10–50 mg L^–1) of the solution on the adsorption uptake were investigated. The optimal parameters that maximize the adsorption uptake according to the specified working range are found to be 4.63 for pH, 49.94 mg L^–1 for initial concentration, 5.25 mg for the adsorbent dose, and the maximum adsorption capacity has been found as 52.26 mg g^–1. The excellent fitting of the pseudo-second kinetic model with (R² = 0.9912) was fitted the experimental data. The Freundlich isotherm model gave a clue about the type of adsorption. Furthermore, thermodynamic results showed that adsorption process was endothermic.     

Assessment of <Emphasis Type="Italic">Urtica</Emphasis> as a low-cost adsorbent for methylene blue removal: kinetic,equilibrium, and thermodynamic studies

Methylene blue (MB) removal using eco-friendly, cost-effective, and freely available Urtica was investigated. The morphology of the adsorbent surface and the nature of the possible Urtica and MB interactions were examined using SEM analysis and the FTIR technique, respectively. Various factors affecting MB adsorption such as adsorption time, initial MB concentration, temperature, and solution pH were investigated. The adsorption process was analysed using different kinetic models and isotherms. The results showed that the MB adsorption kinetic follows a pseudo-second-order kinetic model and the isotherm data fit the Langmuir isotherm well. Thermodynamic parameters, such as ΔG°, ΔH°, and ΔS°, were also evaluated, and the results indicated that the adsorption process is endothermic and spontaneous in nature. The MB adsorption capacity of Urtica was found to be as high as 101.01 mg g^?1, higher than those of many other adsorbents studied in the literature. This superior adsorption capacity, along with the ready availability of Urtica, render this adsorbent potentially suitable for practical applications.     

Quartzite an efficient adsorbent for the removal of anionic and cationic dyes from aqueous solutions

Quartzite obtained from local source was investigated for the removal of anionic dye congo red (CR) and cationic dye malachite green (MG) as an adsorbent from aqueous solution in batch experiment. The adsorption process was studied as a function of dye concentration, contact time, pH and temperature. Adsorption process was described well by Langmuir and Freundlich isotherms. The adsorption capacity remained 666.7 mg/g for CR dye and 348.125 mg/g for MG dye. Data was analyzed thermodynamically, ΔH⁰ and ΔG⁰ values proved that adsorption of CR and MG is an endothermic and spontaneous process. Adsorption data fitted best in the pseudo-first order kinetic model. The adsorption data proved that quartzite exhibits the best adsorption capacity and can be utilized for the removal of anionic and cationic dyes.     

Removal of cibacron blue 3G-A (CB) dye from aqueous solution using chemo-physically activated biochar from oil palm empty fruit bunch fiber

A novel biodegradable adsorbent called pyrolysed empty fruit bunch fibres (PEF) was prepared by chemo-physical activation of empty fruit bunch fibres (EFB) biochar for removal of cibacron blue 3G-A (CB) dye from aqueous solution. PEF was characterized using FTIR, SEM-EDX, XRD and BET techniques. The N₂ adsorption-desorption isotherms indicated PEF’s surface area to be 362.84 m²g⁻¹ and XRD attributed amorphous nature to PEF. After adsorption process, PEF has smoother surface morphology, increase in carbon by weight and shift in functional groups. The established adsorption optimum conditions were pH 10, 45 min contact time and 0.10 g/100 mL adsorbent dosage with 99.05% CB dye removal capacity at 343 K and initial dye concentration 100 mg/L. Desorption ratio >90% after seventh cycle of adsorption-desorption experiments confirmed high reusability (regeneration) of PEF. Pseudo second order kinetic and Freundlich were better fitted with kinetic and isotherm model respectively, while mechanism of adsorption was controlled by film diffusion (external mass transfer). Thermodynamic studied revealed ΔG, ΔS and ΔH to be −3.12 MJ/mol K, 9.11 kJ/mol K, 6.83 kJ/mol respectively at 343 K. The negative value of ΔG, positive values of ΔS and ΔH indicated spontaneity, feasibility and endothermic nature of CB dye adsorption from aqueous solution onto PEF.     

Adsorption of cinnabarinic acid from culture fluid with magnetic microbeads

In this study, antimicrobial pigment cinnabarinic acid (CA) was produced from Pycnoporus cinnabarinus in laboratory‐scale batch cultures. Magnetic poly(ethylene glycol dimethacrylate‐N‐methacryloyl‐l‐tryptophan methyl ester) [m‐poly(EGDMA‐MATrp)] beads (average diameter = 53–103 µm) were synthesized by copolymerizing of N‐methacryloyl‐l‐tryptophan methyl ester (MATrp) with ethylene glycol dimethacrylate (EGDMA) in the presence of magnetite (Fe₃O₄) and used for the adsorption of CA. The m‐poly(EGDMA‐MATrp) beads were characterized by N₂ adsorption/desorption isotherms (Brunauer Emmet Teller), X‐ray photoelecron spectroscopy, scanning electron microscopy, infrared spectroscopy, thermal gravimetric analysis, electron spin resonance and swelling studies. The efficiency of m‐poly(EGDMA‐MATrp) beads for separation of CA from culture fluid was evaluated. The effects of pH, initial concentration, contact time and temperature on adsorption were analyzed. The maximum CA adsorption capacity of the m‐poly(EGDMA‐MATrp) beads was 272.9 mg g⁻¹ at pH 7.0, 25 °C. All the isotherm data can be fitted with the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The adsorption process obeyed pseudo‐second‐order kinetic model. Thermodynamic parameters ΔH = 5.056 kJ mol⁻¹, ΔS = 52.44 J K⁻¹ mol⁻¹ and ΔG = −9.424 kJ mol−¹ to ‐11.27 kJ mol−¹ with the rise in temperature from 4 to 40 °C indicated that the adsorption process was endothermic and spontaneous. Copyright © 2015 John Wiley & Sons, Ltd.     

Uranium extraction from aqueous solution using dried and pyrolyzed tea and coffee wastes

The adsorption of U(VI) onto dried and pyrolyzed tea and coffee wastes was investigated. The adsorption properties of the materials were characterized by measuring uranium uptake as a function of solution pH, kinetics and adsorption isotherms. pH profile of uranium adsorption where UO₂ ²⁺ is expected to be the predominant species was measured between pH 0 and 4. Both Langmuir and Freundlich adsorption models were used to describe adsorption equilibria, and corresponding constants evaluated. Using the Langmuir model, the maximum adsorption capacity of uranium by dried tea and coffee wastes was 59.5 and 34.8 mg/g, respectively at 291 K. Adsorption thermodynamic constants, ΔH° ΔS° and ΔG° were also calculated from adsorption data obtained at three different temperatures. Adsorption thermodynamics of uranyl ions on dried tea and coffee systems indicated spontaneous and endothermic processes. Additionally, a Lagergren pseudo-second-order kinetic model was used to fit the kinetic experimental data for both adsorbents and the constants evaluated. Dried tea and coffee wastes proved to be effective adsorbents with high capacities and significant advantage of a very low cost.     

Water-insoluble cyclodextrin polymer crosslinked with citric acid for paraquat removal from water

The anionic water-insoluble cyclodextrin polymer (polyCTR-β-CD) was crosslinked between β-cyclodextrin (β-CD) and citric acid (CTR) at 180?°C during 30?minutes to eliminate paraquat (PQ) from water. The reaction yield was equal to 70.2%, the ionic exchange capacity corresponded to 3.29?mmol·g^?1 and the β-CD content was 0.29?mmol·g^?1. Then, samples were characterized by SEM, ATR-FTIR, TGA, BET and stereoscopic microscope. Adsorption experiments were investigated with different factors such as pH of the solution, contact time, initial concentration of paraquat and adsorption temperature. The relevant pH was equal to 6.5 and the optimal contact time was 120?minutes to attain adsorption equilibrium. At 30?°C, the adsorption capacity was increased (9.4, 17.4 and 20.8?mg·g^?1) when the initial concentration of paraquat was raised (25, 50 and 200?mg·L^?1 respectively). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. For thermochemistry parameters at different temperatures, the negative ΔG° showed a spontaneous adsorption process, the negative ΔH° indicated an exothermic process and the positive ΔS° exhibited an increase disorder. Finally, the reusability of the insoluble polymer was reached 78.3% after four regeneration cycles in methanol.     

Modified bentonite by polyhedral oligomeric silsesquioxane and quaternary ammonium salt and adsorption characteristics for dye

To remove methylene blue dye from water by adsorption, bentonites were modified by polyhedral oligomeric silsesquioxane (POSS) and three kind of quaternary ammonium surfactants (dodecyl trimethyl ammonium bromide, tetrabutyl ammonium bromide, cetyl trimethylammonium bromide) in aqueous solution. Systematic adsorption experiments were carried out, the adsorption mechanism was studied, and the factors governing the adsorption of methylene blue on modified bentonite were discussed. The adsorption capacity of methylene blue on all three modified bentonites in 1000 mg·L⁻¹ solutions quickly reached equilibrium within 2000 s, and the removal rate was basically 100%; however, the removal rate in raw bentonite samples was only 60%. The pseudo second-order kinetic model can provide satisfactory kinetic data fitting. The obtained adsorption isotherms fit well with the Dubinin-Radushkevich isotherm model. The thermodynamic results showed that the adsorption process was a spontaneous endothermic physical adsorption process. With increasing pH and KCl concentration, the removal of methylene blue increased significantly. The results of this study confirmed that the modified bentonite is a candidate material as a cationic dye adsorbent.     

Adsorptive recovery of an essential rose oil component from aqueous solution by nanoporous carbon (CMK-3)

A nanoporous carbon (CMK-3) was synthesized and used to adsorb 2-phenylethanol (PEA) from aqueous solutions. The characterization of CMK-3 by N₂ adsorption isotherm revealed the formation of a nanoporous carbon with average pore diameter and surface area of 3.34 nm and 1268 m² g^?1, respectively. Column-like particle morphology of CMK-3 was observed from scanning electron microscope images. To evaluate the feasibility of CMK-3 as a potential PEA adsorbent, batch adsorption experiments were conducted for aqueous PEA solutions. The results showed that CMK-3 is an efficient sorbent for the separation of PEA from water. The optimized adsorbent doses were found to be 0.3 and 2.2 g L^?1 for 30 and 300 mg L^?1 PEA, respectively. Our studies about the effect of pH on CMK-3 adsorption capacity revealed that the adsorption capacity increased at lower pH due to the protonation of PEA. Three adsorption models, Langmuir, Freundlich and Temkin were used to describe the adsorption isotherms. Thermodynamic parameters such as ΔG ⁰, ΔH ⁰, and ΔS were also evaluated, and it was found that the sorption process was spontaneous, endothermic, and physical in nature. The adsorption kinetics was investigated in detail and the pseudo-second-order kinetic equation fitted the experimental data very well. The mechanistic study by Weber-Morris model revealed that the overall adsorption process was simultaneously governed by external mass transfer and intraparticle diffusion. Almost all (97 %) adsorbed PEA was successfully recovered into ethanol which is a common solvent in fragrance industry. CMK-3 was proved to be a promising adsorbent for the adsorption-recovery of PEA from aqueous solution.     

Kinetics of Acid Blue 1 Adsorption from Aqueous Solution by Carbonaceous Substrate Produced from Biotic Precursor

Adsorption of acid blue 1 from aqueous solution onto carbonaceous substrate produced from the wood of Paulownia tomentosa was investigated. The samples characterized by FTIR, SEM, EDS and XRD techniques, indicated that the surface functional groups like carboxyl, lactones or phenols and ethers have disappeared at high activation temperature （800 ℃） and as a result porous structure was developed that has a positive effect on the adsorption capacity. Bangham and parabolic diffusion models were applied to the kinetic adsorption data, which show that the adsorption of acid blue 1 was a diffusion controlled process. The reaction rate increased with the increase in temperatures of both the adsorption and activation. Thermodynamic parameters like △E^≠, △H^≠, △S^≠ and △G^≠ were calculated from the kinetic data. The negative values of △S^≠ reflected the decrease in the disorder of the system at the solid-solution interface during adsorption. Gibbs free energy （△G^≠）, representing the driving force for the affinity of dye for the carbon surface, increased with the increase in sample activation and the adsorption temperatures.     

Liquid phase adsorption of Congo red dye on functionalized corn cobs

This study investigates the adsorption of Congo red (CR) dye onto corn cob based activated carbon (CCAC) in the batch process. The activated carbon was characterized using FTIR, SEM, and EDX techniques, respectively. The effect of operational parameters such as the initial dye concentration (10–50?mg/L), contact time (5–160 minutes), and solution temperature (30–50°C) were studied. The amount of the CR dye adsorbed was found to increase as these operational parameters increased. Kinetic data for CR dye adsorption onto CCAC were best represented by the pseudo second-order kinetic model. Four different isotherms namely Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were used to test the adsorption data. It fitted the Langmuir isotherm model most. Thermodynamic parameters such as ΔH⁰, ΔS⁰, and ΔG⁰ were evaluated. The adsorption process was found to be exothermic and spontaneous. The study shows that CCAC is an effective adsorbent for the adsorption of CR dye from aqueous solution.     

Multi‐responses optimization of simultaneous adsorption of methylene blue and malachite green dyes in binary aqueous system onto Ni:FeO(OH)‐NWs‐AC using experimental design: derivative spectrophotometry method

In this research, response surface methodology (RSM) approach using Central Composite Design (CCD) coupled by derivative spectrophotometry method was applied to develop mathematical model and optimize process parameters for simultaneous adsorption of methylene blue (MB) and malachite green (MG) from aqueous solution using Ni:FeO(OH) ‐ NWs‐AC. The optimal conditions to adsorption of MB and MG in binary mixture solution from aqueous solution were found at pH 8.0, MB concentration 20 mg L^‐1, MG concentration 20 mg L^‐1, adsorbent dosage 0.033 g and contact time 40 min. At these conditions, high adsorption efficiency (99.39% and 100.0% for MB and MG, respectively) was achieved. Among experimental equilibrium, Langmuir isotherm model fitted well with maximum monolayer adsorption capacity of 28.6 and 29.8 mg g^‐1 for MB and MG, respectively. The adsorption kinetic data followed pseudo second‐order kinetics for MB and MG dyes.     

Insight from adsorption properties of Xylidyl Blue embedded hydrogel for effective removal of uranyl: Experimental and theoretical approaches

Applications of a hybrid material consisting of polyacrylamide (PAA) and Xylidyl Blue (XB) for the removal of uranyl ions from aqueous solutions has been investigated with all details. Adsorption experiments were performed at batch mode and constant temperature. Experimental parameters affecting adsorption process such as pH, initial uranyl concentration, time and temperature were studied on the removal of the uranyl ions. The isotherms assays were carried out with synthetic solutions and adsorption data were evaluated by using Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Morphological and chemical characterizations of new synthesized material were investigated by UV-VIS-NIR spectroscopy and SEM/EDX techniques and pH_pzc experiments. The results of the kinetic experiments are consistent with pseudo-second-order models and intra-particle diffusion models with a slightly better fit to the latter. Equilibrium was achieved within 3 h. The value of rate constant for adsorption process was calculated as 1.055 mol⁻¹ kg min⁻¹ at 318 K. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that the adsorption of uranyl ions onto XB@PAA was feasible, spontaneous and endothermic nature under the studied temperature. The developed material has also a potential as a sensor because its color turn from pink to red by adsorption of uranyl ions.     

Study of the adsorbent properties of nickel oxide for phenol depollution

Phenol and its derivatives are considered as dangerous pollutants due to these harmful effects on health and the environment. Treatment of the waters charged by these compounds by adsorption remains very important. For these reasons, this study was designed to prepare nickel oxide by precipitation method in order to remove these pollutants from aquatic environments. Indeed, structural and textural properties of this solid have been determined by various physicochemical methods (X-ray diffraction, Fourier transform in the infrared, N2 adsorption/desorption (BET), ATD / ATG thermal analysis and scanning electron microscopy (SEM)). In addition, several adsorption tests were carried out in order to show the effectiveness of this solid for the elimination of phenol in aqueous solution and to determine the physicochemical parameters which affect adsorption. Our results have shown 5.29 mg·g⁻¹ of adsorption capacity with 98% of yield. Furthermore, it was shown that adsorption process was endothermic. For the kinetic study, it was demonstrated that phenol adsorption on NiO follows the pseudo-second-order and the Langmuir model better adaptable for the isotherm of desorption. Moreover, thermodynamic study shows positive values of ΔS ° (266.6 JK⁻¹·mol⁻¹) suggesting a randomness increase of the solid/liquid interface. ΔH ° (60.41 kJ·mol⁻¹) was also positive confirming the endothermic nature of the adsorption processes. However, ΔG ° (kJ·mol⁻¹) was negative suggesting the spontaneity of the phenol adsorption. In summary, this work suggests that phenol adsorption on NiO was linked to the chemical adsorbate/adsorbent interactions.     

Dye removal by a novel hydrogel‐clay nanocomposite with enhanced swelling properties

Acrylamide (AAm)‐2‐acrylamide‐2‐methylpropanesulfonic acid sodium salt (AMPSNa) hydrogel and AAm‐AMPSNa/clay hydrogel nanocomposite having 10 w% clay was prepared by in situ copolymerization in aqueous solution in the presence of a crosslinking agent (N,N′‐methylenebisacrylamide (NMBA)). Swelling properties and kinetics of the hydrogel samples were investigated in water and aqueous solutions of the Safranine‐T (ST) and Brilliant Cresyl Blue (BCB) dyes. The swelling and diffusion parameters were also calculated in water and dye solutions. It was observed that the AAm‐AMPSNa/clay hydrogel nanocomposite exhibits improved swelling capacity compared with the AAm‐AMPSNa hydrogel. It was also found that the diffusion mechanisms show non‐Fickian character. Adsorption properties of the hydrogel samples in the aqueous solution of ST and BCB dyes were also investigated. Clay incorporation into the hydrogel structure increased not only the adsorption capacity but also the adsorption rate. Adsorption capacity values of the hydrogel nanocomposite were found to be 484.2 and 494.2 mg g^?1 for the ST and BCB dyes, respectively. It was seen that the adsorption of dyes by the hydrogel nanocomposite completed in 10 min while the AAm‐AMPSNa hydrogel adsorbed dyes approximately in 90 min. Adsorption data of the samples were modelled by the pseudo‐first‐order and pseudo‐second‐order kinetic equations in order to investigate dye adsorption mechanism. It was found that the adsorption kinetics of hydrogel nanocomposite followed a pseudo‐second‐order model. Equilibrium isotherms were analyzed using the Langmuir and Freundlich isotherms. It was seen that the Langmuir model fits the adsorption data better than the Freundlich model. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of environmental parameters on the sequestration of radionickel by Mg2Al layered double hydroxide

In this work, sequestration of Ni(II) from aqueous solution to Mg₂Al layered double hydroxide (Mg₂Al LDH) by adsorption process as a function of various water quality parameters and temperature was investigated. The results showed that the kinetic adsorption could be described by a pseudo-second order model very well. The adsorption of Ni(II) on Mg₂Al LDH was strongly dependent on pH and ionic strength. The presence of humic acid (HA)/fulvic acid (FA) enhanced the adsorption of Ni(II) on Mg₂Al LDH at low pH, whereas reduced Ni(II) adsorption at high pH. The Langmuir model fitted the adsorption isotherms of Ni(II) better than the Freundlich model at three different temperatures of 298, 318 and 338 K. The thermodynamic parameters (ΔH^o, ΔS^o and ΔG^o) calculated from the temperature dependent adsorption isotherms indicated that the adsorption process of Ni(II) on Mg₂Al LDH was endothermic and spontaneous. The results show that Mg₂Al LDH is a promising material for the preconcentration and separation of pollutants from large volumes of aqueous solutions.     

Adsorption of acid blue on synthesized polymeric nanocomposites,PPy/MCM-41 and PAni/MCM-41: Isotherm,thermodynamic and kinetic studies

In the this research, removal of acid blue 62 from aqueous solution using mesoporous crystalline material-41 (MCM-41) loaded by polypyrrole (PPy) and polyaniline (PAni) was investigated. Synthesized composites were characterized by SEM, TEM, FTIR, XRD and BET analysis. Langmuir adsorption isotherm showed the best compatibility with the experimental data in comparison with other isotherm models (q_m = 55.55 mg/L). Kinetic studies proved that the adsorption process is compatible with the pseudo-second-order kinetic model. Thermodynamic parameters such as Gibbs free energy changes (ΔG^o), Enthalpy changes (ΔH^o) and Entropy changes (ΔS^o) were calculated. Negative value of ΔG^o and positive value of ΔH^o show that adsorption of Acid blue 62 on PPy/MCM-41 nanocomposite is a spontaneous process also endothermic.