Effective removal of methylene blue from aqueous solutions using magnetic loaded activated carbon as novel adsorbent

Evaluation of electrokinetics coupled with a reactive barrier of activated carbon loaded with a nanoscale zero-valent iron for selenite removal from contaminated soils

The range between dietary deficient and toxic levels for selenium is quite narrow. In this study, the synergistic effects of electrokinetics (EK) and a permeable reactive barrier (PRB) on the reductive sequestration of Se(IV) oxyanions from spiked soils were investigated in detail. Activated charcoal (AC)-supported Fe(II) and nanoscale zero-valent iron (nZVI) were prepared as the PRB media for use in an electrolyzer. In aqueous equilibrium adsorption tests, the AC-supported nZVI medium had a higher adsorption capacity than that of the other adsorbents. The Se(IV) removal isotherms were well-fitted using the Langmuir model. The Se(IV) removal rates were accurately predicted by both pseudo-first- and pseudo-second-order kinetic models. For the coupled systems, a moderate increase in the number of PRBs and decrease in the PRB thickness in the electrolyzer enhanced the removal and catalytic recovery of Se(IV) from the spiked soil samples. A Se(VI) removal efficiency of approximately 95% and Se(VI) reduction efficiency of 90% were achieved in the optimized electrochemical system. The Se(IV) species were reduced to Se° and FeSe by the AC-supported nZVI regardless of the pH distribution. The experimental results provide guidance for the multichannel recovery of Se from abandoned ore tailings or solid wastes.

Activated carbon/metal-organic framework nanocomposite: Preparation and photocatalytic dye degradation mathematical modeling from wastewater by least squares support vector machine

Herein, Kiwi peel activated carbon (AC), Materials Institute Lavoisier (MIL-88B (Fe), and AC/MIL-88B (Fe) composite were synthesized and used as catalysts to degrade Reactive Red 198. The material properties were analyzed by the FTIR, BET-BJH, XRD, FESEM, EDX, TGA, and UV-Vis/DRS. The BET surface area of AC, MIL-88B (Fe) and AC/MIL-88B (Fe) was 1113.3, 150.7, and 199.4 m²/g, respectively. The band gap values (E_g) estimated by Tauc plot method, were obtained 5.06, 4.19 and 3.79 eV for AC, MIL-88B (Fe) and AC/MIL-88B (Fe), respectively. The results indicated that the AC/MIL-88B (Fe) composite had higher photocatalytic activity (99%) than that of pure AC (79%) and MIL-88B (Fe) catalysts (87%). The decolorization kinetic was matched well with the second-order model. Moreover, the data were modeled using least squares support vector machine which optimized with Cuckoo optimization algorithm. The optimal parameters were found 0.837 and 3.49e+02 based on σ² and γ values, respectively. The mean square error (MSE) and correlation coefficient (R²) values were obtained 3.97 and 0.948. Therefore, the attained data, materials characterization and prediction of modeling validate the composite form of MIL-88B(Fe) with new AC, had better photocatalytic activity in comparison with the individual form.

Synthesis of fibrous LaFeO3 perovskite oxide for adsorption of Rhodamine B

The LaFeO₃ perovskite oxide decorated active carbon fibers (LFO-ACFs) based on cotton fabric waste were successfully synthesized through sol-gel loading and thermal treatment. LaFeO₃ perovskite and cotton fabric waste were combined to an eco-friendly and cheap adsorbent, which could reuse the leftover materials of textile industry and realize their functional modification. The structural, morphology/microstructure and functional groups were investigated through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared spectroscopy (FTIR), respectively. The XRD pattern suggested the cotton fabric matrix didn't influence the structure of LaFeO₃ perovskite oxide. In SEM studies, LFO-ACFs still maintained fibrous shape of the raw cotton fibers, and the EDX analysis showed that the main elements of the prepared LFO-ACFs were La, Fe, O and C. The synthesized LFO-ACF was employed for adsorption of cational dye of Rhodamine B (RhB), and the effects of adsorption parameters, i.e. pH, contact time, solution temperature and initial concentration of dye, on adsorption behavior were investigated. Results suggested the adsorption performance of LFO-ACF for RhB was nearly not affected by solution pH and its maximum adsorption capacity fitted by the Langmuir isothermal model could attain 182.6 mg/g at 293 K. The adsorption kinetics followed the pseudo-second-order equation and the regeneration of LFO-ACF could be well realized through an easy pyrolysis method.

Novel carbon based bioactive nanocomposites of aniline/indole copolymer for removal of cationic dyes from aqueous solution: kinetics and isotherms

In this study, a copolymer of aniline and indole P(ANI-co-IN) and its nanocomposites based on graphene oxide (GO) and functional carbon nanotubes (CNT-COOH) were synthesized by heterogeneous emulsion polymerization.

Insight into the adsorption mechanisms of methylene blue and chromium(iii) from aqueous solution onto pomelo fruit peel

In this study, the biosorption mechanisms of methylene blue (MB) and Cr(iii) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with ab initio simulations.

Dispersive micro-solid phase extraction based on Fe3O4@SiO2@Ti-MOF as a magnetic nanocomposite sorbent for the trace analysis of caffeic acid in the medical extracts of plants and water samples prior to HPLC-UV analysis

In this work, Fe₃O₄@SiO₂@Ti-MOF-NCs, as an efficient sorbent, have been synthesized in a laboratory and utilized for extracting CA in the medical extracts of plants and water samples before their analysis by HPLC.

Influence of Al2O3 Nanoparticles on the Soil Elements

The behavior of nanoparticles released to the soil has been extensively studied in recent years; however, the effects of nanoparticles on the distribution of soil elements and on sowing are still unknown. To this end, to examine the distribution of selected elements in soil, soil samples were treated weekly with 1.0 mg and 20.0 mg of Al₂O₃ nanoparticles for 3 weeks. Additionally, different types of plants (including taproot, fibrous root and ornamental bulbous plants) were sowed in the soil samples. After each treatment, surface soil samples were collected and digested with acid digestion. The concentrations of selected elements (Ca, Mg, Fe, Al, Cu, Co, Ni) were determined using a microwave plasma atomic emission spectrometer. Al₂O₃ treatment for 3 weeks, both low and high doses, had no effect on the Al content in soil samples when compared to the controls. Additionally, Al₂O₃ showed desorption properties on the analyte elements.

Magnetic activated carbon nanocomposite from Nigella sativa L. waste (MNSA) for the removal of Coomassie brilliant blue dye from aqueous solution: Statistical design of experiments for optimization of the adsorption conditions

The present work was carried out to evaluate the removal of Coomassie brilliant blue dye by adsorption onto a magnetized activated carbon nanocomposite (MNSA) prepared from Nigella sativa L. (NS) waste. Different techniques, including infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption, were used to characterize MNSA to investigate its adsorption properties. Adsorption experiments were carried out by simultaneously optimizing four variables that usually present a strong effect in adsorption studies. A full 2⁴ factorial design with 3 central points was used. The four independent variables were the initial pH of the dye solution (pH), the initial dye concentration (C_o), the adsorbent mass (m), and the contact time (t). The sorption capacity (q) of the adsorbent and the percentage of dye removal (% Rem) from an aqueous solution were used as the responses of the factorial design. The results indicated that pH, C_o, and m were essential factors for the overall optimization of both responses (q and % Rem) and that several interactions of two, three and four factors occurred. Based on the design of the experiments (DOE), the optimized conditions for adsorption were pH = 2.00, C_o = 40.0 mg L^-1, m = 30.0 mg, and t = 3.0 h. Under these conditions, both responses, q and % Rem, were maximized, with a desirability of 85.54%. The findings of this study could be useful for industrial wastewater treatment systems.

Accumulation of U(VI) on the Pantoea sp. TW18 isolated from radionuclide-contaminated soils

Pantoea sp. TW18 isolated from radionuclide-contaminated soils was used for the bioremediation of radionuclides pollution. Accumulation mechanism of U(VI) on Pantoea sp. TW18 was investigated by batch experiments and characterization techniques. The batch experiments revealed that Pantoea sp. TW18 rapidly reached accumulation equilibrium at approximately 4 h with a high accumulation capacity (79.87 mg g^-1 at pH 4.1 and T = 310 K) for U(VI). The accumulation data of U(VI) onto Pantoea sp. TW18 can be satisfactorily fitted by pseudo-second-order model. The accumulation of U(VI) on Pantoea sp. TW18 was affected by pH levels, not independent of ionic strength. Analysis of the FT-IR and XPS spectra demonstrated that accumulated U(VI) ions were primarily bound to nitrogen- and oxygen-containing functional groups (i.e., carboxyl, amide and phosphoryl groups) on the Pantoea sp. TW18 surface. This study showed that Pantoea sp. TW18 can be considered as a promising sorbent for remediation of radionuclides in environmental cleanup.

Adsorption of basic and reactive dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon: batch and column study

The adsorption behavior of basic, methylene blue (MB), and reactive, remazol brilliant violet 5R (RBV), dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon (IBSAC) was executed via batch and column studies. The produced activated carbon was characterized through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch studies were performed to investigate the effects of contact time, initial concentration, and solution pH. The equilibrium data for both MB and RBV adsorption better fits Langmuir model with maximum adsorption capacity of 434.78 and 212.77 mg/g, respectively. Kinetic studies for both MB and RBV dyes showed that the adsorption process followed a pseudo-second-order and intraparticle diffusion kinetic models. For column mode, the breakthrough curves were plotted by varying the flow rate, bed height, and initial concentration and the breakthrough data were best correlated with the Yoon-Nelson model compared to Thomas and Adams-Bohart model. The adsorption activity of IBSAC shows good stability even after four consecutive cycles.

Magnetic particles modification of coconut shell-derived activated carbon and biochar for effective removal of phenol from water

The separation and recovery of pollutant-loaded magnetic carbon materials from organic contaminated environment is recently concerned, but the change of sorption ability and mechanism of activated carbon and biochar caused by magnetic particles modification still need to be explored. Here, the magnetic modification of two coconut shell-, coal-derived activated carbon and one biochar, and its effect on the removal of phenol from water were investigated. Magnetic activated carbon (MAC) and magnetic biochar (MBC) were prepared by co-precipitation. The increase of mass magnetic susceptibilities and energy dispersive X-ray spectroscopy (EDX) analysis showed that magnetic particles were successfully coated on the surface of virgin carbonaceous materials (VCMs). Magnetic modification enhanced the surface area and pore volume of activated carbon, and preserved those structure properties of biochar. Magnetic activated carbon had lower adsorption rates (10.641 g mg^-1·min^-1) than virgin activated carbon (20.575 g mg^-1·min^-1) while magnetic biochar exhibited higher adsorption rate (0.618 g mg^-1·min^-1) compared with virgin biochar (0.040 g mg^-1·min^-1), which were related to mass transport process. Data from Langmuir model results suggested that maximum adsorption capacities of three carbon adsorbents were increased by magnetic modification. The enhanced removal of phenol after magnetizing process may attribute to the increase of specific surface area and pore volume. Among VCMs/MCCs, magnetic coconut shell-derived carbon material with 951.84 m²/g surface area exhibited the most organic contaminant sorption performance. This finding gives insight into the adsorption mechanism of magnetic AC/BC for phenol, and provides a guidance to choose the appropriate magnetic composites to remove the organic contaminant effectively.

Enhancement of synchronous bio-reductions of vanadium (V) and chromium (VI) by mixed anaerobic culture

The co-occurrence of toxic vanadium (V) and chromium (VI) in groundwater receives incremental attention while knowledge on their interactions in biogeochemical processes is limited, with lack of efficient removal means. This study is the first to realize synchronous bio-reductions of V(V) and Cr(VI) with high efficiency by mixed anaerobic culture. After 72-h operation, 97.0 ± 1.0% of V(V) and 99.1 ± 0.7% of Cr(VI) were removed, respectively, with initial concentration of 1 mM for both V(V) and Cr(VI). Cr(VI) bio-reduction took priority while V(V) detoxification was inhibited. V(IV) and Cr(III) were the identified reduction products, both of which could precipitate naturally. Initial Cr(VI) and acetate concentrations as well as pH affected this process significantly. High-throughput 16S rRNA gene sequencing analysis indicated the accumulation of Anaerolineaceae, Spirochaeta and Spirochaetaceae, which could contribute to V(V) and Cr(VI) bio-reductions. The new knowledge obtained in this study will facilitate understanding the biogeochemical fate of co-existing V(V) and Cr(VI) in groundwater and development of bioremediation strategy for their induced combined pollution.

Removal of Cd(II) and Fe(III) from DMSO by silica gel supported PAMAM dendrimers: Equilibrium, thermodynamics, kinetics and mechanism

A series of silica gel supported amino-terminated PAMAM dendrimers (SG-G1.0 - SG-G3.0) were used for the removal of Cd(II) and Fe(III) from dimethylsulfoxide (DMSO). Various parameters that influence adsorption behaviors including temperature, contact time, and initial metal ion concentration were studied. The adsorption mechanism was revealed by combining the results of experiment and density functional theory (DFT) calculation. It indicates that the adsorption capacities for Cd(II) and Fe(III) are largest among the metal ions tested. The adsorption capacity of SG-G1.0 - SG-3.0 for Cd(II) and Fe(III) follows the order of SG-G2.0 > SG-3.0 > SG-G1.0. The adsorption isotherm shows the adsorption capacities for both metal ions increases with raising the temperature and initial metal ion concentration. The adsorption isotherm is consistent with Langmuir model and the adsorption process is dominated by chemical adsorption mechanism. Thermodynamic parameters indicates that the adsorption for both Cd(II) and Fe(III) is spontaneous and endothermic. Kinetic adsorption indicates that the adsorption equilibrium times for Cd(II) and Fe(III) is about 200 and 350 min, respectively, which can be described by a pseudo-second-order model and controlled by film diffusion process. FTIR analysis and theoretical calculation revealed that the carbonyl O atoms, secondary amine N atoms, and primary amine N atoms are the primary factor responsible for PAMAM adsorption by forming tetra- and penta-coordinated chelates with metal ions.

Adsorption behavior of Ni(II) onto activated carbons from hide waste and high-pressure steaming hide waste

This work reports the preparation and adsorption of Ni(II) via activated carbons which produced from hide waste (HWAC) and high-pressure steaming hide waste (HWSAC) with potassium silicate as the activating agent. The best preparation condition for HWAC and HWSAC was the activation temperature of 700 °C using an impregnation ratio of 2:1. Both of them were characterized by N₂ adsorption/desorption isotherms, SEM and FT-IR spectra. The surface area of HWAC and HWSAC was 1804.37 and 1361.26 m²/g, respectively. Despite the surface area of HWAC being larger than that of HWSAC, but the adsorption capacity of Ni(II) for HWAC was lower than that for HWSAC. Furthermore, the adsorption capacity of Ni(II) for both HWAC and HWSAC showed pH-dependent behavior and increased with the increase in pH value, which can be attributed to the functional groups of HWAC and HWSAC materials through the electrostatic attraction. The adsorption data for HWAC and HWSAC were fitted with four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first order model, pseudo-second order model, intra-particle diffusion and Elovich equation), indicating that Langmuir isotherm and Pseudo-second order model fitted well with high coefficient of determination (R² > 0.99) for both the two adsorbents. The positive enthalpy of adsorption (ΔH) and free energy of adsorption (ΔG) indicate a spontaneous and endothermic nature of the process. These results demonstrated that activated carbon can be prepared from hide waste which could remove heavy metal such as Ni(II) effectively.

Adsorption of Trace Estrogens in Ultrapure and Wastewater Treatment Plant Effluent by Magnetic Graphene Oxide

In the current study, graphene oxide, Fe3+, and Fe2+ were used for the synthesis of magnetic graphene oxide (MGO) by an in situ chemical coprecipitation method. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to characterize the well-prepared MGO. The prepared MGO was used as an adsorbent to remove five typical estrogens (estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (17α-E2), estriol (E3), and synthetic estrogen (EE2)) at the ppb level from spiked ultrapure water and wastewater treatment plant effluent. The results indicated that the MGO can efficiently remove estrogens from both spiked ultrapure water and wastewater treatment plant effluent in 30 min at wide pH ranges from 3 to 11. The temperature could significantly affect removal performance. A removal efficiency of more than 90% was obtained at 35 °C in just 5 min, but at least 60 min was needed to get the same removal efficiency at 5 °C. In addition, an average of almost 80% of the estrogens can still be removed after 5 cycles of MGO regeneration but less than 40% can be reached after 10 cycles. These results indicate that MGO has potential for practical applications to remove lower levels of estrogens from real water matrixes and merits further evaluation.

Preparation and characterization of activated carbons from winemaking wastes and their adsorption of methylene blue

This work reports the preparation of activated carbons via the hydrothermal treatment at 523 K/30 bar of two common winemaking wastes: bagasse and cluster stalks. The hydrothermal carbons produced by the above treatment were turned into activated carbons via their exposure to KOH and carbonization at 1073 K. These were then subjected to Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy examination, and the determination of their Brunauer–Emmett–Teller surface area. The ability of the activated carbons to adsorb methylene blue in aqueous solution was then examined, determining the influence of time, methylene blue concentration, and temperature. Equilibrium conditions were reached for reaction times between 180 and 240 min at pH 7. The adsorption isotherms were found to better fit the Langmuir than the Freundlich model, and the adsorption kinetics fitted a pseudo-second-order model. The maximum adsorption at 303 K was 714–847 mg g−1. Thermodynamic studies revealed the adsorption of methylene blue to be spontaneous and exothermic. These results show that high-quality activated carbons can be produced from winemaking waste.

Response surface optimization, kinetic and thermodynamic studies for effective removal of rhodamine B by magnetic AC/CeO2 nanocomposite

The activated carbon (AC) was obtained from waste scrap tires and modified by bimetallic Fe and Ce nanoparticles in order to combine both the high surface area and the active sites for enhanced adsorption of the dye. The produced nanocomposite was used as a novel cost-effective magnetic in rhodamine B (RhB) removal from aqueous solutions. The FT-IR, SEM, EDX, TEM, and surface area analysis methods were implemented to characterize the morphological, chemical, thermal and surface properties of the developed adsorbent. The optimum batch experimental conditions were found under the response surface methodology. The adsorption equilibrium data were well fitted by the Langmuir isotherm model. The adsorption capacity was 324.6 mg g^-1. The kinetic and thermodynamics studies were also carried out to understand the adsorption mechanism. The study indicated that RhB adsorption by the AC/Fe/Ce magnetic adsorbent has an endothermic character and followed the pseudo-second-order kinetics model. By using ethanol solution, RhB was desorbed at high efficiency and the prepared material could be recycled for up to ten cycles. Thus, the magnetic nanocomposite is an effective and promising adsorbent for the cleaning treatment of RhB ions from wastewater by a large scale designed adsorption system.

Fabrication of cotton textile waste-based magnetic activated carbon using FeCl3 activation by the Box–Behnken design: optimization and characteristics

Cotton textile waste-based magnetic activated carbon was prepared via simultaneous activation-pyrolysis using FeCl₃ as a novel activating agent.

Environmentally-friendly and ultrasonic-assisted preparation of two-dimensional ultrathin Ni/Co-NO3 layered double hydroxide nanosheet for micro solid-phase extraction of phenolic acids from fruit juices

In this paper, we report an environmentally-friendly and low cost synthetic approach for large-scale fabrication of 2-dimentional porous Ni/Co-NO₃-based layered double hydroxide (Ni/Co-NO₃-LDH) nanosheet through ultrasonic-assisted process. The synthesis procedure used ethylene glycol/water system as an eco-friendly solvent system. The synthesized LDH was characterized by FE-SEM, TEM, XRD, and FT-IR techniques. FE-SEM and TEM images showed porous structure surface morphology of the synthesized LDH. Also, For Ni/Co-NO₃-LDH, a hexagonal ultrathin layered was obtained owing to ultrasonic irradiation and applied processing conditions. The prepared LDH was used as sorbent in dispersive micro solid-phase extraction procedure. Two phenolic acids including p-hydroxybenzoic acid and p-coumaric acid were selected as model compounds. Some experimental factors affecting the extraction efficiency of the analytes were investigated and optimized. Finally, the sorbent was used for the extraction of model compound from fruit juice samples followed by high performance liquid chromatography. Linear dynamic range of 0.5-500µgL^-1 with a low detection limit (0.1µgL^-1) was obtained by the method. The relative standard deviations were 2.5 and 4.3% for p-hydroxybenzoic acid and p-coumaric acid, respectively. All recoveries were between 82 and 92%.

Removal of endrin and dieldrin isomeric pesticides through stereoselective adsorption behavior on the graphene oxide-magnetic nanoparticles

A novel stereoselective removal behavior of isomeric endrin and dieldrin pesticides from sample solution is demonstrated using nanocomposite of graphene oxide (GO) and iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs). The removal efficiency of endrin and dieldrin was found higher when GO-MNPs was used as a separating probe than the individual use of GO and MNPs. The removal efficiency of both the pesticides was found to be more favorable when the dosage amount of GO-MNPs was 30 mg for 30-min contact time with pH 4.0 at room temperature. The good correlation of determination (R ²) with 0.975 and 0.973 values obtained for endrin and dieldrin, respectively demonstrated a well fitting of Langmuir adsorption isotherm model. The higher removal percentage (86.0%) and higher slope value of Langmuir adsorption isotherm were estimated for endrin compared to dieldrin (74.0%). The reason for higher adsorption percentage of endrin is due to the endo-position of oxygen atom in molecule favors more interaction of molecules with GO-MNPs compared to the exo-position of oxygen present in dieldrin. In addition, the higher value of R ² for endrin and dieldrin demonstrated better suitability of pseudo-first-order and pseudo-second-order kinetic models, respectively. The advantages of the present method are use of simple UV-vis spectrophotometry for monitoring and low-cost use of GO-MNPs nanomaterial for the removal of pesticides from sample solution.

Characteristics and adsorption study of the activated carbon derived from municipal sewage sludge

Sewage sludge-based activated carbon is proved to be an efficient and low-cost adsorbent in treatment of various industrial wastewaters. The produced carbon had a well-developed pore structure and relatively low Brunauer-Emmett-Teller (BET) surface area. Adsorptive capacity of typical pollutants, i.e. copper Cu(II) and methylene blue (MB) on the carbon was studied. Adsorptions were affected by the initial solution pH, contact time and adsorbent dose. Results showed that adsorption of Cu(II) and MB on the produced carbon could reach equilibrium after 240 min. The average removal rate for Cu(II) on the carbon was high, up to 97% in weak acidic conditions (pH = 4-6) and around 98% for MB in a very wide pH range (pH = 2-12). The adsorption kinetics were well fitted by the pseudo-second order model, and both Langmuir and Freundlich isotherm models could well describe the adsorption process at room temperature. The theoretical maximum adsorption capacities of Cu(II) and MB on sewage sludge-based activated carbon were 114.94 mg/g and 125 mg/g, respectively. Compared with commercial carbon, the sewage sludge-based carbon was more suitable for heavy metal ions' removal than dyes'.