Investigation on efficient adsorption of cationic dyes on porous magnetic polyacrylamide microspheres

Effect of a pH-controlled co-precipitation process on rhodamine B adsorption of MnFe2O4 nanoparticles

We investigated the effect of a pH-controlled co-precipitation process on the adsorption behavior of manganese ferrite (MnFe2O4) nanoparticles as well as their structural and magnetic properties. The pH of prepared MnFe2O4 nanoparticles is typically an important factor affecting the adsorption capacity of an adsorbent. In this study, MnFe2O4 nanoparticles were prepared using a co-precipitation method at four different pH values of 9.0, 9.5, 10.0, and 10.5. The adsorption behaviors on rhodamine B (RhB) by MnFe2O4 nanoparticles prepared at different pH values were investigated. It was found that, via a pH-controlled process, MnFe2O4 nanoparticles prepared at pH 10.5 showed the highest RhB removal efficiency. The results indicated that the large pore size and surface charge of MnFe2O4 nanoparticles improved the adsorption capacities for RhB. Kinetic data were fitted to a pseudo-second order kinetic model and revealed that equilibrium was reached within 60 min. The isotherm data showed that the Langmuir maximum adsorption capacity of the MnFe2O4 nanoparticles prepared at pH 10.5 for RhB was 9.30 mg g-1.

Flocculation performance of lignin-based flocculant during reactive blue dye removal: comparison with commercial flocculants

A novel lignin-based flocculant (LBF) with superior flocculation performance was prepared from paper mill sludge in this work. The functional groups of LBF and alkaline lignin (AL) were determined by Fourier transform infrared spectroscopy (FTIR). The flocculation performance of LBF integrated with polyaluminum chloride (PAC) was tested in reactive dye wastewater treatment. Floc properties and color removals in multiple flocculation systems were discussed. Results indicated that the dye removal (93%) was greatly facilitated as the LBF was integrated with PAC (PAC + LBF). In addition, floc properties and color removals were significantly improved in the presence of Ca²⁺ and Mg²⁺. In contrary, flocculation performance was greatly restricted in the presence of SO₄^2-. LBF was less pH sensitive and shear sensitive than polyacrylamide (PAM) due to the enhanced charge neutralization and bridging action. On the basis of that, LBF could be used as a promising flocculant in dye wastewater treatment.

Synthesis of nanoporous cobalt/carbon materials by a carbonized zeolitic imidazolate framework-9 and adsorption of dyes

The cobalt/carbon material Z9-600 exhibits a high adsorption capacity for methylene green and a high regeneration efficiency after 4 cycles of use and reuse.

A versatile bio-based material for efficiently removing toxic dyes, heavy metal ions and emulsified oil droplets from water simultaneously

Developing versatile materials for effective water purification is significant for environment and water source protection. Herein, a versatile bio-based material (CH-PAA-T) was reported by simple thermal cross-linking chitosan and polyacrylic acid which exhibits excellent performances for removing insoluble oil, soluble toxic dyes and heavy metal ions from water, simultaneously. The adsorption capacities are 990.1mgg^-1 for methylene blue (MB) and 135.9mgg^-1 for Cu²⁺, which are higher than most of present advanced absorbents. The adsorption towards organic dyes possesses high selectivity which makes CH-PAA-T be able to efficiently separate dye mixtures. The stable superoleophobicity under water endows CH-PAA-T good performance to separate toluene-in-water emulsion stabilized by Tween 80. Moreover, CH-PAA-T can be recycled for 10 times with negligible reduction of efficiency. Such versatile bio-based material is a potential candidate for water purification.

Waste rice straw and coal fly ash composite as a novel sustainable catalytic particle electrode for strengthening oxidation of azo dyes containing wastewater in electro-Fenton process

A novel catalytic particle electrode (CPE) was synthesized from waste rice straw and coal fly ash which was employed to strengthen electro-Fenton treating actual azo dyes containing wastewater. Results showed that the prepared CPE exhibited excellent electro-catalytic activity and significantly improved performance of pollutants removal at near-neutral pH condition, achieving over 73.5 and 90.5% of chemical oxygen demand (COD) and color removal percentages, respectively, allowing discharge criteria to be met. And the electro-Fenton with CPE improved the biodegradability of wastewater in terms of BOD₅/COD, resazurin dehydrogenase activity, and toxicity, indicating the potential application of integrated biosystem for this type of wastewater. On the basis of inhibition of different radical scavengers and fluorescence test, it was deduced that the main contribution of the novel CPE was responsible for catalyzing electro-generate H₂O₂ to produce more hydroxyl radicals in electro-Fenton, and the positive role of generation of superoxide anion at near-neutral pH was also proved, further the possible reaction mechanism was proposed. Moreover, CPE showed the advantages of superior stability and low cost at successive runs and the results offered new insights for sustainable use of waste materials.

Multifunctional PMMA@Fe₃O₄@DR Magnetic Materials for Efficient Adsorption of Dyes

Magnetic porous microspheres are widely used in modern wastewater treatment technology due to their simple and quick dye adsorption and separation functions. In this article, we prepared porous polymethylmethacrylate (PMMA) microspheres by the seed-swelling method, followed by in situ formation of iron oxide (Fe₃O₄) nanoparticles within the pore. Then, we used diazo-resin (DR) to encapsulate the porous magnetic microspheres and achieve PMMA@Fe₃O₄@DR magnetic material. We studied the different properties of magnetic microspheres by different dye adsorption experiments before and after the encapsulation and demonstrated that the PMMA@Fe₃O₄@DR microspheres can be successfully used as a reusable absorbent for fast and easy removal of anionic and aromatic dyes from wastewater and can maintain excellent magnetic and adsorption properties in harsh environments.

Cellulose nanocrystal-reinforced keratin bioadsorbent for effective removal of dyes from aqueous solution

High-efficiency and recyclable three-dimensional bioadsorbents were prepared by incorporating cellulose nanocrystal (CNC) as reinforcements in keratin sponge matrix to remove dyes from aqueous solution. Adsorption performance of dyes by CNC-reinforced keratin bioadsorbent was improved significantly as a result of adding CNC as filler. Batch adsorption results showed that the adsorption capacities for Reactive Black 5 and Direct Red 80 by the bioadsorbent were 1201 and 1070mgg^-1, respectively. The isotherms and kinetics for adsorption of both dyes on bioadsorbent followed the Langmuir isotherm model and pseudo-second order model, respectively. Desorption and regeneration experiments showed that the removal efficiencies of the bioadsorbent for both dyes could remain above 80% at the fifth recycling cycles. Moreover, the bioadsorbent possessed excellent packed-bed column operation performance. Those results suggested that the adsorbent could be considered as a high-performance and promising candidate for dye wastewater treatment.

Electrospun H4SiW12O40/cellulose acetate composite nanofibrous membrane for photocatalytic degradation of tetracycline and methyl orange with different mechanism

H₄SiW₁₂O₄₀ (SiW₁₂)/cellulose acetate (CA) composite nanofibrous membrane was prepared by electrospinning in which CA was employed as the support of SiW₁₂. Characterization with Fourier transformation infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) indicated that SiW₁₂ has been successfully loaded into the CA membrane and its Keggin structure remained intact. The as-prepared composite membrane exhibited enhanced photocatalytic activity in the decomposition of tetracycline (TC) and methyl orange (MO) compared with pure SiW₁₂ under ultraviolet irradiation. The optimal mass ratio of SiW₁₂ to CA was 1:4, and the corresponding degradation efficiency for TC and MO was 63.8% and 94.6%, respectively. It is noteworthy that the degradation rate of MO increased more evidently than that of TC under the same conditions, which may be attributed to the different role that CA nanofibrous membrane played in the TC and MO photodegradation process. Besides providing more contact area between SiW₁₂ and the pollutant in TC photodegradation, CA membrane played an additional role that donated electron to SiW₁₂ in the MO degradation process, leading to a different photocatalytic mechanism with greatly enhanced degradation rate. Moreover, the composite membrane presented an excellent reusability, which was mainly ascribed to the water-insolubility of CA and the hydrogen bonds between CA and SiW₁₂. This work will be useful for the design of biopolymer-based membrane photocatalysts applied to antibiotics and dyes wastewater treatment.

Enhanced adsorption removal of anionic dyes via a facile preparation of amino-functionalized magnetic silica

A novel amino-functionalized magnetic silica (Fe₃O₄@SiO₂-NH₂) was easily prepared via a one-step method integrating the immobilization of 3-aminopropyltriethoxysilane with a sol-gel process of tetraethyl orthosilicate into a single process. This showed significant improvement in the adsorption capacity of anionic dyes. The product (Fe₃O₄@SiO₂-NH₂) was characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectrometry, zeta potential and vibrating sample magnetometry. The adsorption performance of Fe₃O₄@SiO₂-NH₂ was then tested by removing acid orange 10 (AO10) and reactive black 5 (RB5) from the aqueous solutions under various experimental conditions including initial solution pH, initial dye concentrations, reaction time and temperature. The results indicated that the maximum adsorption capacity of AO10 and RB5 on Fe₃O₄@SiO₂-NH₂ was 621.9 and 919.1 mg g^-1 at pH 2, respectively. The sorption isotherms fit the Langmuir model nicely. Similarly, the sorption kinetic data were better fitted into the pseudo-second order kinetic model than the pseudo-first order model. In addition, the thermodynamic data demonstrated that the adsorption process was endothermic, spontaneous and physical. Furthermore, Fe₃O₄@SiO₂-NH₂ could be easily separated from aqueous solutions by an external magnetic field, and the preparation was reproducible.

Synthesis of citric acid functionalized magnetic graphene oxide coated corn straw for methylene blue adsorption

The citric acid functionalized magnetic graphene oxide coated corn straw (CA-mGOCS) as a new adsorbent was synthesized in this work for the elimination of methylene blue (MB) from waste water. The as-prepared CA-mGOCS was tested by SEM, FTIR, XRD, Roman spectrum, TGA, particle size analyzer, BET and magnetic properties analyzer. Some factors affecting adsorption removal efficiency were explored. As a result, the addition of 5g CS (CA-mGO5CS) had the better adsorption performance than other adsorbents. The pseudo-second-order model and the Freundlich described the adsorption behavior well. The equilibrium adsorption capacity was 315.5mgg^-1 for MB at pH=12 and 298k. The electrostatic incorporation as well as hydrophobic interactions between CA-mGO5CS and MB determined the favourable adsorption property. Besides, the thermodynamic studies results ΔG<0, ΔH<0, ΔS<0 suggested that the adsorption was a spontaneous, exothermic and randomness decrease process. Finally, reusability studies imply that CA-mGO5CS has an excellent reproducibility.

Adsorption-desorption behavior of magnetic amine/Fe3O4 functionalized biopolymer resin towards anionic dyes from wastewater

In this work, a new kind of magnetic amine/Fe3O4 functionalized biopolymer resin (amine/Fe3O4-resin) was prepared and applied to remove various anionic dyes from water. Methyl Orange (MO), Reactive Brilliant Red K-2BP (RBR) and Acid Red 18 (AR) were selected as the typical anionic dye for this research. Meanwhile, amine/Fe3O4-resin was characterized by VSM, XRD, FT-IR, SEM, TEM and XPS. Three anionic dyes removed by amine/Fe3O4-resin were investigated using batch adsorption technique, and the parameters including adsorbent dosage, pH, contact time and temperature were considered. Due to a large number of amine groups and high surface areas, amine/Fe3O4-resin exhibited a remarkably high adsorption capacity for all three dyes, reaching 101.0mg/g, 222.2mg/g and 99.4mg/g for RBR, MO and AR at 25°C, respectively. The pseudo second order model and Langmuir model agreed well with the experimental data, and regeneration experiments indicated its merit of separability and reusability.

Enhanced adsorption capacity of polypyrrole/TiO2 composite modified by carboxylic acid with hydroxyl group

Carboxylic acid with hydroxyl group enhanced the adsorption capacity of PPy/TiO₂ composites.

Removal of acid red 88 by a magnetic graphene oxide/cationic hydrogel nanocomposite from aqueous solutions: adsorption behavior and mechanism

In this study, a kind of magnetic graphene oxide/cationic hydrogel nanocomposite (MGO–CH) was synthesized and characterized for acid red 88 (AR88) removal.

Green method to fabricate porous microspheres for ultrasensitive SERS detection using UV light

A green method to fabricate porous polymer microspheres with SERS activity for ultrasensitive SERS detection using UV light.

Synthesis, characterization of nitrogen-doped mesoporous carbon spheres and adsorption performance

Nitrogen-doped mesoporous carbon spheres (NMCS) were prepared by a nanocasting route using benzoxazine resins as the precursor of nitrogen and carbon, and ordered mesoporous silica spheres as the hard template to remove methyl orange (MO).

Electrospun H4SiW12O40/chitosan/polycaprolactam sandwich nanofibrous membrane with excellent dual-function: adsorption and photocatalysis

Scheme of the structure of the SNM, the treatment of Cr(vi) and MO in aqueous solutions, and the regeneration process.

Surface area control of nanocomposites Mg(OH)2/graphene using a cathodic electrodeposition process: high adsorption capability of methyl orange

The nanocomposites Mg(OH)₂/graphene (nano-MG) were controllably prepared by a facile cathodic electrodeposition.

Nanosorbcats of methylene blue on novel Fe2O3 nanorods for photocatalytic water oxidation

MB@pfa@Fe₂O₃ nanorods are efficient recyclable nanosorbcats for LED light driven dioxygen generation using water as oxygen source.

Fe3O4@P(DVB/MAA)/Pd composite microspheres: preparation and catalytic degradation performance

Fe₃O₄@P(DVB/MAA)/Pd composite microspheres were synthesized with a combination of coating and loading processes using Fe₃O₄ nanoparticles as a core.

Selective adsorption and separation of organic dyes from aqueous solution on polydopamine microspheres

Polydopamine (PDA) microspheres, synthesized by a facile oxidation polymerization route, were evaluated as a potential adsorbent for selective adsorption and separation of organic dyes. The adsorption processes towards nine water-soluble dyes (anionic dyes: methyl orange (MO), eosin-Y (EY), eosin-B (EB), acid chrome blue K (ACBK), neutral dye: neutral red (NR), and cationic dyes: rhodamine B (RhB), malachite green (MG), methylene blue (MB), safranine T (ST)) were thoroughly investigated. The adsorption selectivity of organic dyes onto PDA microspheres was successfully applied for the separation of dyes mixtures. Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for adsorption of representative organic dyes including MB, MG and NR. The pseudo-first-order and pseudo-second-order kinetics models were used to fit the adsorption kinetics process. Five isothermal adsorption models (Langmuir, Dubnin-Radushkevich, Temkin, Freundlich and Harkins-Jura) were used to investigate the adsorption thermodynamics properties. The results showed that the PDA microspheres owned good selective adsorption ability towards cationic dyes. The adsorption kinetics process conformed to the pseudo-second-order kinetics model and the Langmuir isotherm model was more appropriate for tracing the adsorption behavior than other isotherm models. Thus, we can conclude PDA microspheres may be a high-efficiency selective adsorbent towards some cationic dyes.

Poly(4-styrenesulfonic acid-co-maleic acid)-sodium-modified magnetic reduced graphene oxide for enhanced adsorption performance toward cationic dyes

PSSMA-modified magnetic reduced graphene oxide nanocomposites (PSSMA/M-rGO) were prepared and used for enhanced adsorption of cationic dyes.

Adsorption behavior of one-dimensional coordination polymers [Cu(bipy)X]n (X = 2Cl− and SO42−) toward acid orange 7 and methyl orange

A kind of one-dimensional coordination polymer, [Cu(bipy)X]_n (X = 2Cl⁻ or SO₄²⁻), was prepared by Cu²⁺ and 4,4′-bipyridine (bipy) through a facile method, and used as the adsorbent for removal of acid orange 7 (AO7) and methyl orange (MO) from water.