Core-shell graphene oxide and Carboxymethyl cellulose Vortex ring aerogel particles for the adsorptive removal of contrasting azo dyes from water

Synthesis of zirconium-based metal-organic framework under mild conditions and its application to the removal of cationic and anionic dyes from wastewater

Decontamination of organic dyes from wastewater requires efficient and compatible materials that must be able to remove dyes with different charges at the same time. In this study, composites of layered double hydroxide (LDH) and hydrochar (HC) were prepared and tested for use as general-purpose sorbents for the simultaneous removal of cationic and anionic dyes (i.e., methylene blue (MB), methyl orange (MO), and reactive yellow (RY)). Characterization studies reveal that the surface functional groups on composites are –OH, NO3, M–O bonds. It was observed that crystallinity of LDH decreased with an increasing amount of HC. Preliminary experiments showed that the dyes (i.e., MB, MO, and RY) were well removed simultaneously onto the composite with HC (2.0 g HC/prepared composite). This composite was selected for more experiments, and the adsorption efficiency was optimized by the multivariate technique using the response surface methodology (RSM). Removal efficiency of 100% was obtained for all three dyes with an adsorption capacity of 243, 5.3, and 16.3 µmol g−1 for MB, MO, and RY, respectively. Elovich’s initial intake rates (α) were 4,272, 441, and 99.5 mg g−1 min−1 for RY, MB, and MO, respectively. Data fitted in various models suggested second-order multiplex kinetics, where the surface heterogeneity response was sorbate dependent.

Removal of anionic and cationic dyes from aqueous solution with activated organo-bentonite/sodium alginate encapsulated beads

Facile synthesis of lignin-based Fe-MOF for fast adsorption of methyl orange

Surface decoration of MnNiWO4 nanostructures on carbon nanofiber to build nanocomposites towards the removal of anionic azo and cationic dyes under light illumination

In this study, chitosan nanoparticles (ChNs) were used as an adsorbent for single and simultaneous uptake of cationic (methylene blue (MB)) and anionic (methyl orange (MO)) dyes. ChNs were prepared based on the ionic gelation method using sodium tripolyphosphate (TPP) and characterized by zetasizer, FTIR, BET, SEM, XRD, and pHPZC. The studied parameters that affect removal efficiency included pH, time, and dyes' concentration. The results showed that in single-adsorption mode, the removal of MB is better in alkaline pH, contrary to MO uptake which presents higher removal efficiency in acidic media. The simultaneous removal of MB and MO from the mixture solution by ChNs could be achieved under neutral conditions. The adsorption kinetic results showed that adsorption of MB and MO for both single-adsorption and binary adsorption systems comply with the pseudo-second-order model. Langmuir, Freundlich, and Redlich-Peterson isotherms were used for the mathematical description of single-adsorption equilibrium, while non-modified Langmuir and extended Freundlich isotherms were used to fit the co-adsorption equilibrium results. The maximum adsorption capacities of MB and MO in a single dye adsorption system were 315.01 and 257.05 mg/g for MB and MO, respectively. On the other hand, and for binary adsorption system, the adsorption capacities were 49.05 and 137.03 mg/g, respectively. The adsorption capacity of MB decreases in solution containing MO and vice versa, suggesting an antagonistic behavior of MB and MO on ChNs. Overall, ChNs could be a candidate for single and binary removal of MB and MO in dye-containing wastewater.

Selective removal of anionic and cationic dyes by magnetic Fe3O4-loaded amine-modified hydrochar

Aramid nanofibers/Bacterial cellulose nanocomposite aerogels for high-efficient cationic dye removal

In this work, Schiff base network-1 (SNW-1), as a new generation of covalent organic frameworks (COFs), was synthesized and modified by fabrication of a composite with clay mineral montomorillonite (Mt). It was used for simultaneous removal of anionic and cationic dyes from aqueous solutions. The fabricated composite was characterized successfully with various techniques. Tartrazine (TT) and methylene blue (MB) were selected as model anionic and cationic dyes, respectively. The effects of the percentage of each component in the composite, initial pH, and initial dye concentration were evaluated on the adsorption capacity. Adsorption reaction models and adsorption diffusion models were used to study the kinetic process of adsorption. Adsorption of both dyes reached equilibrium after 40min. The obtained results were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) models to predict the isotherms of adsorption. Under optimum conditions for removal of each dye with the composite, the maximum adsorption capacity of 519.2 and 602.7mgg-1 were obtained for TT and MB, respectively. The used SNW-1/Mt composite could be regenerated by salty methanol. The high adsorption capacity and excellent reusability make SNW-1/Mt composite attractive for the simultaneous removal of anionic and cationic dyes from aqueous solutions.

Herein, we present the synthesis of a novel clay (palygorskite (Pal)) functionalised metal-organic framework (MOF)-based (UiO-66) composite applied as adsorbent for water and air treatment. The efficiency for the removal of both cationic and anionic dyes from aqueous matrices and the CO2 capture was evaluated. The composite was synthesised via an easy open-vessel thermal process. The structural, textural, compositional and morphological properties of the prepared materials were characterised using a variety of techniques including X-ray diffraction (XRD), attenuated total reflection (ATR), N2 physisorption, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The adsorption properties of the materials were evaluated for the removal of methylene blue (MB) and methyl orange (MO), as representative cationic and anionic dyes, respectively. Their efficiency in CO2 capture efficiency was also investigated. All UiO-66-based materials presented high efficiency for the removal of MO. Despite that Pal showed very low MO removal efficiency, its presence did not alter the adsorption of MO on the Pal/UiO-66 composite. On the contrary, the Pal/UiO-66 was much more efficient than pristine UiO-66 for the removal of cationic dyes. This is ascribed to the presence of palygorskite, offering multifunctionality for the treatment of waters containing both anionic and cationic dyes. In addition, although Pal presented low CO2 uptake ability, its presence in the composite did not alter significantly the CO2 adsorption efficiency of the composite compared with the pristine MOF. The findings of this study demonstrate the significance of coupling clays with MOF structures for the development of synergies that allow multifunctionality, expanding the application of MOF-based sorbents.

We investigate the removal of methyl orange (MO) and methylene blue (MB) from aqueous solution by montmorillonite-pillared graphene oxide (MGO). Experimental conditions were used that evaluate the potential of MGO in removing anionic and cationic dyes in single and binary systems, and we investigated the uptake capacity of MGO toward organic dye as a function of different pH, adsorbent dosage, temperature, and adsorption time. In the single system, the Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and calculate the isotherm constants. Moreover, the pseudo-first-order and pseudo-second-order kinetic models were applied to study the mechanism of MGO adsorbing dyes. Thermodynamic studies demonstrated that the adsorption of MO and MB onto MGO was feasible and spontaneous. In the binary system, the adsorption capacities of MO and MB by MGO were dramatically higher than those in a single system. Therefore, through the recorded adsorption results under different conditions, we could illustrate that the MGO was absolutely used as an adsorbent to be capable of simultaneous removals of MO and MB.

Application of activated carbon produced from phosphoric acid-based chemical activation of oil fly ash for the removal of some charged aqueous phase dyes: role of surface charge, adsorption kinetics, and modeling

This study presents the synthesis and use of a novel bamboo-derived magnetic activated carbon (BMAC) for the effective removal of cationic and anionic dyes, specifically methylene blue (MB), methyl orange (MO), and sunset yellow (SY), from aqueous solutions. The adsorbent was synthesized using thermal carbonization and subsequent inclusion of magnetic oxide, yielding a porous structure with improved adsorption and magnetic separation properties. Thorough characterization utilizing SEM, EDX, BET, FTIR, XRD, and TGA/DTA validated the creation of a highly porous material including uniformly dispersed magnetic particles and several surface functional groups. Batch adsorption tests were performed to examine the influences of contact time, adsorbent dosage, initial dye concentration, pH, and temperature. The findings indicated rapid adsorption kinetics, with equilibrium reached in around 60–70 min, and adsorption capacity ranked as MB > MO > SY. Augmenting adsorbent dosage enhanced removal efficiency but diminished adsorption capacity per unit mass due to site unsaturation. The maximum adsorption capacities (qm) of BMAC were 58.9, 56.3, and 32.7 mg/g for MB, MO, and SY, respectively, as determined from the Langmuir isotherm model, indicating superior performance compared with other reported magnetic activated carbon. The adsorption process was determined to be exothermic and spontaneous, as evidenced by thermodynamic characteristics. The equilibrium data were optimally characterized by the Langmuir isotherm model, indicating monolayer adsorption, whereas the kinetic studies conformed to the pseudo-second-order model, signifying that chemisorption is predominant. The adsorption mechanism encompasses electrostatic interactions, π–π stacking, hydrogen bonding, van der Waals forces, pore filling, and surface complexation with magnetic oxides. The findings indicate that BMAC is an efficient, sustainable, and magnetically recoverable adsorbent for the elimination of both cationic and anionic dyes from wastewater.

The current work involves studying the adsorption process of brilliant cresyl blue (BCB) and methyl orange (MeO) dyes using local pumpkin seed husks (LPSH). The LPSH adsorbent was analysed by using Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive x-ray spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analyses. The descriptive analysis of the morphology of LPSH revealed a heterogeneous surface, while the structural analysis showed the presence of functional groups typical of lignocellulosic structures and it was confirmed that the mesoporous surface of the adsorbent had a specific surface area of ~1.53 m2 g-1. The adsorption isotherm studies suggested that the Langmuir model best described the adsorption of MeO, while the Freundlich model is more suitable for describing the adsorption of BCB. According to the thermodynamic analyses, the adsorption of BCB was exothermic and spontaneous, whereas the adsorption of MeO was endothermic and non-spontaneous. The results of evaluating the efficiency of the LPSH adsorbent showed that the maximum adsorption capacities are ~81 mg g-1 for the BCB dye and ~8.2 mg g-1 for the MeO dye.

In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R2 = 0.9991 for MB and R2 = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R2 = 0.9970) and RO16 (R2 = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions.