Nanoporous activated carbon materials from pomelo peel for efficient adsorption of anionic and cationic dyes

The present research focuses on the synthesis and the modification of mesoporous silica SBA-15 using in situ polymerization of pyrrole. The structural/textural and morphological features of adsorbents were investigated through X-ray diffraction, nitrogen sorption at 77 K, thermogravimetric analysis, Fourier transform infrared spectroscopy, zeta potential measurements and scanning electronic microscopy. Several nanocomposites containing different percentages of polypyrrole were tested for the adsorption of both anionic and cationic dyes. The effect of adsorbent nature, pH, contact time, adsorbent dose and initial dye concentration were investigated and discussed in terms of adsorption efficiency. The adsorption efficiency of MO dye increased in the following sequence: SBA-15 < PPy/SBA-15(1%) < PPy/SBA-15(10%) < PPy/SBA-15(30%) < PPy/SBA-15(50%). The adsorption of MB dye is preferably carried out by parent material SBA-15 and nanocomposite PPy/SBA-15(1%). The experimental data were verified by the Langmuir and Freundlich isotherms, and the kinetic data were fitted by pseudo-first-order and pseudo-second-order models. The obtained results showed that the adsorption of the both dye by nanocomposite PPy/SBA-15 followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. The adsorbed amounts recorded for MO and MB dyes are 41.66 and 58.82 mg/g, respectively.

Biobased amphoteric aerogel with core-shell structure for the hierarchically efficient adsorption of anionic and cationic dyes

Chitosan (CS) is largely employed in environmental applications as an adsorbent of anionic dyes, due to the presence in its chemical structure of amine groups that, if protonated, act as adsorbing sites for negatively charged molecules. Efficient adsorption of both cationic and anionic dyes is thus not achievable with a pristine chitosan adsorbent, but it requires the combination of two or more components. Here, we show that simultaneous adsorption of cationic and anionic dyes can be obtained by embedding Linde Type A (LTA) zeolite particles in a crosslinked CS-based aerogel. In order to optimize dye removal ability of the hybrid aerogel, we target the crosslinker concentration so that crosslinking is mainly activated during the thermal treatment after the fast freezing of the CS/LTA mixture. The adsorption of isotherms is obtained for different CS/LTA weight ratios and for different types of anionic and cationic dyes. Irrespective of the formulation, the Langmuir model was found to accurately describe the adsorption isotherms. The optimal tradeoff in the adsorption behavior was obtained with the CS/LTA aerogel (1:1 weight ratio), for which the maximum uptake of indigo carmine (anionic dye) and rhodamine 6G (cationic dye) is 103 and 43 mg g−1, respectively. The behavior observed for the adsorption capacity and energy cannot be rationalized as a pure superposition of the two components, but suggests that reciprocal steric effects, chemical heterogeneity, and molecular interactions between CS and LTA zeolite particles play an important role.

The efficiency of acid treatment on natural calcium bentonite (natural bentonite) for anionic dye adsorption was investigated using methyl orange (MO) as a probe. Additionally, adsorption experiments were accomplished between the natural bentonite, acidified bentonite, and a cationic dye (methylene blue, MB). Acid functionalization in natural bentonite (RF) was carried out with HCl and H2SO4 acids (RF1 and RF2, respectively). The samples were characterized by chemical analysis, mineralogy, particle size, and thermal behavior with the associated mass losses. The adsorption efficiency of MO and MB dyes was investigated by the effects of the initial concentration of adsorbate () and the contact time (). The acid treatment was efficient for increasing the adsorption capacity of the anionic dye, and the values measured were 2.2 mg/g, 67.4 mg/g e 47.8 mg/g to RF, RF1 e RF2, respectively. On the other hand, the acid functionalization of bentonite did not significantly modify the MB dye adsorption. The Sips equation was the best fit for the adsorption isotherms. Thus, we found that the acid-functionalized bentonite increases the anionic dye adsorption by up to 8000%. The increased adsorptive capacity of acidified bentonite was explained in terms of electrostatic attraction between the clay surface and the dye molecule.

Microwave synthesis of amino-functionalized MCM-41 from coal gasification fine slag for efficient bidirectional adsorption of anionic and cationic dyes

In this present study, composites films of starch (St), Starch/CTA-bentonite (S@CB) and Starch/CTA-magadiite (S@CM) were fabricated by a solution casting process using glycerol as a plasticizer. The prepared samples were tested for the adsorption of cationic MB dye. The composites were characterized by X-ray diffraction XRD, Fourier transform infrared spectroscopy FTIR and scanning electronic microscopy SEM. These characterizations confirmed the interaction and immobilization of the modified solids as well as their commendable dispersed in the starch matrix. Equilibrium adsorption data of MB was carried out at 298 K. Two isotherm models (Freundlich and Langmuir) were tested for modeling the adsorption isotherms by the nonlinear form. Higher adsorption capacity and improved stability were achieved by composite films. The obtained data showed that the adsorption of MB dye on both composite films followed the Langmuir adsorption isotherm model and their kinetics was followed by the pseudo-second order model. The maximum adsorption values of MB dye were 89.82 and 76.59 mg/g for S@CB and S@CM composites, respectively.

This work deals with promoting the efficiency of removing the cationic and ionic dyes by new aerogel–carbon nanostructures. For cleaner production the rice straw-pulping black liquors, which regards serious environmental risk during routine disposing, is used in preparing the aerogel precursors. These aerogels (AGBs) depend on using pulping black liquor in hybrid with resorcinol and the less carcinogenic formaldehyde butyraldehyde. Black liquors from five pulping processes are used, Elemental, thermogravimetric (TGA and DTG), and FTIR-ATR analyses are used to characterize the carbon precursors. While their adsorption behavior toward cationic and anionic dyes are accessed via iodine-value, adsorption capacity and kinetic models, textural characterization, and SEM. The TGA measurements reveal that AGBs from BLs of neutral sulfite and soda-borohydride pulping reagents have higher activation and degradation energies than other aerogels. In terms of cationic and anionic dyes adsorption as well as textural characterization, the AGB-CNSs surpass that made from BLs. The discarded KOH/NH4OH black liquor is used to synthesize the best aerogel precursor for producing cationic methylene blue dye (MB) adsorbent, where it provides an adsorption capacity 242.1 mg/g. The maximum anionic brilliant blue dye (BB) adsorption capacity, 162.6 mg/g, is noticed by Kraft BL-aerogel-CNSs. These finding data overcome the literature carbon adsorbents based on lignin precursors. All examined CNSs toward MB dye follow the Langmuir adsorption equilibrium; while primarily the Freundlich model for BB dye. The pseudo-second-order kinetic model well fits the adsorption kinetics of investigated AGB-CNSs. The textural characterization and SEM revealed a mixture of mesoporous and micro porous features in the CNSs.

Mussel-inspired fabrication of pH-responsive pomelo peels as “smart” bio-based adsorbents for controllable removal of both cationic and anionic dyes

Preparation of fibrous chitosan/sodium alginate composite foams for the adsorption of cationic and anionic dyes

This study investigates the adsorption of cationic (methylene blue, MB) and anionic (methyl orange, MO) dyes onto activated carbon synthesized from almond seed shells (ASS-AC). The adsorbent was produced via carbonization and chemical activation and characterized using FTIR, XRD, SEM, and BET analyses. FTIR results revealed abundant oxygen-containing functional groups that enhanced electrostatic attraction and hydrogen bonding with dye molecules. XRD analysis indicated a predominantly amorphous carbon structure, while BET analysis showed a high surface area of 520 m²/g with dominant microporosity. Batch adsorption experiments evaluated the effects of contact time, initial dye concentration, pH, adsorbent dosage, and temperature. Adsorption kinetics followed a pseudo-second-order model (R² &gt; 0.99), suggesting chemisorption as the rate-limiting step. Thermodynamic parameters (ΔG° &lt; 0, ΔH° &gt; 0) confirmed that the adsorption process was spontaneous and endothermic. Equilibrium studies showed that MB adsorption was best described by the Langmuir model with a maximum adsorption capacity of 162 mg/g, while MO adsorption followed the Freundlich model, indicating heterogeneous multilayer adsorption. Overall, ASS-AC demonstrates strong potential as a sustainable, low-cost adsorbent for efficient removal of both cationic and anionic dyes from wastewater.

Efficient adsorption of cationic and anionic dyes using hydrochar nanoparticles prepared from orange peel

Graphitic carbon-like material (GCM) derived from edible sugar under a nitrogen environment was applied as an adsorbent for the removal of anionic and cationic dyes (methyl orange, MO) and methylene blue (MB) from wastewater. The physico-chemical characterization of GCM was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The plate-like morphology with an average size of 50-100 nm was measured from the SEM images. The measured BET 'surface area and pore volume were 574 m2/g and 0.248 cm3/g, respectively with pore diameter (d), 1.8 47 (< 2 nm) indicates that the GCM classified as a microporous. The effects of dosage, pH, contact time and concentration on the adsorption of MB and MO onto GCM were studied to unveil the adsorption process. The experimental isotherm data concurred with the Langmuir isotherm model (R2 = 0.990) for MB, while the MO isotherm data concurred with Freundlich model (R2 = 0.995). The maximum adsorption capacity achieved from the Langmuir isotherm equation at 25 °C was 38.75 and 43.48 mg/g for MB and MO, respectively, which indicates that GCM is a suitable adsorbent for the adsorption of both anionic and cationic dyes. The kinetic study demonstrated that the adsorption of both dyes onto GCM was the pseudo-second-order diffusion kinetics. The thermodynamic parameters reveal the adsorption of both dyes was endothermic spontaneous through chemical interactions. The GCM was found to be a potential adsorbent for the removal of MB and MO from an aqueous solution.

Highly effective adsorption of cationic and anionic dyes on magnetic Fe/Ni nanoparticles doped bimodal mesoporous carbon

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.

ZIF-8/Chitosan hybrid nanoparticles with tunable morphologies as superior adsorbents towards both anionic and cationic dyes for a broad range of acidic and basic environments