Adsorption Of Anionic Dyes Research Articles

Adsorption of anionic and cationic azo dyes from wastewater using novel and effective multicomponent adsorbent

Water pollution is rising worldwide, necessitating innovative and effective treatment solutions. This study introduces a multicomponent/multifunctional novel nanocomposite synthesized from polyethyleneimine (PEI), graphene oxide (GO), bentonite clay, and MgFeAl-layered triple hydroxide (LTH), termed as AGO/Bentonite/LTH. In this study, the synthesized AGO/Bentonite/LTH nanocomposite was utilized to remove azo dyes (methyl orange and crystal violet) from contaminated water samples. The novel AGO/Bentonite/LTH nanocomposite was benchmarked against its pristine materials and their binary combinations. The results indicated the superior adsorption performance of the AGO/Bentonite/LTH nanocomposite relative to all other adsorbents synthesized and examined herein. All the synthesized adsorbents were characterized using different techniques in order to reveal their textural properties, functional groups, morphology, thermal stability, and crystallinity before applying them to decontaminate wastewater samples contaminated with methyl orange (MO) and crystal violet (CV). The Langmuir adsorption isotherm model predicted that the maximum adsorption capacities of CV and MO onto the AGO/Bentonite/LTH nanocomposite are 1705.1 and 1171.8 mg/g, respectively. On the other hand, zeta potential, pH, and FTIR studies suggested the existence of multiple mechanisms governing the adsorption of CV and MO onto the AGO/Bentonite/LTH nanocomposite. Thermodynamic results indicated the endothermicity and exothermicity of CV and MO adsorption, respectively. Another interesting finding reported herein is the high reusability of this nanocomposite as demonstrated by the minimal reduction in the removal of these two pollutants with the repetitive use of the nanocomposite. Additionally, the nanocomposite can also be easily and cheaply regenerated via a few rinses with a diluted NaOH aqueous solution. These interesting observations suggest that the synthesized AGO/Bentonite/LTH nanocomposite is a potent material for efficient dye removal from contaminated water bodies.

Adsorbents prepared from epoxy-based porous materials of microcrystalline cellulose for excellent adsorption of anionic and cationic dyes

It reported a porous material prepared from microcrystalline cellulose (MCC), to achieve rapid preparation of adsorbents. The porous material was characterized by several tools including 1H NMR, FTIR, XPS, and SEM. Two adsorbents were prepared and subjected to adsorption experiments. Dye adsorption experiments show that the adsorption driving is electrostatic interactions and the process is chemisorption. The maximum capacity of Microcrystalline cellulose-g-Poly (glycidyl methacrylate)-Tannins (MPT) reached 191.3 (Methylene blue), 123.7 mg g−1 (Rhodamine B), and Microcrystalline cellulose-g-Poly (glycidyl methacrylate)-Lysine (MPL) attained 425.8 (Methylene blue), 480.7 mg g−1 (Methyl orange). The results were followed the pseudo-second-order (PSO) and agreed with the Langmuir fit model. Adsorption-desorption cycling experiments further indicate that the adsorbent possesses outstanding reproducibility. At last, epoxidized bio-porous materials are positive in the preparation of dye adsorbents with critical adsorption properties.

Polypyrrole-decorated bentonite magnetic nanocomposite: A green approach for adsorption of anionic methyl orange and cationic crystal violet dyes from contaminated water

In the presented study, a novel polypyrrole-decorated bentonite magnetic nanocomposite (MBnPPy) was synthesized for efficient removal of both anionic methyl orange (MO) and cationic crystal violet (CV) dyes from contaminated water. The synthesis of this novel adsorbent involved a two-step process: the magnetization of bentonite followed by its modification through in-situ chemical polymerization. The adsorbent was characterized by SEM/EDX, TEM/SAED, BET, TGA/DTA-DTG, FTIR, VSM, and XRD studies. The investigation of the adsorption properties of MBnPPy was focused on optimizing various parameters, such as dye concentration, medium pH, dosage, contact time, and temperature. The optimal conditions were established as follows: dye concentration of Co (CV/MO) at 100 mg/L, MBnPPy dosage at 2.0 g/L, equilibrium time set at 105 min for MO and 120 min for CV, medium pH adjusted to 5.0 for MO dye and 8.0 for CV dye, and a constant temperature of 303.15 K. The different kinetic and isotherm models were applied to fit the experimental results, and it was observed that the Pseudo-2nd-order kinetics and Langmuir adsorption isotherm were the best-fitted models. The maximal monolayer adsorption capacities of the adsorbent were found to be 78.74 mg/g and 98.04 mg/g (at 303.15 K) for CV and MO, respectively. The adsorption process for both dyes was exothermic and spontaneous. Furthermore, a reasonably good regeneration ability of MBnPPy (>83.45%/82.65% for CV/MO) was noted for up to 5 adsorption-desorption cycles with little degradation. The advantages of facile synthesis, cost-effectiveness, non-toxicity, strong adsorption capabilities for both anionic and cationic dyes, and easy separability with an external magnetic field make MBnPPy novel.

Construction of C8/threonine-functionalized mesoporous silica aerogel based on mixed-mode and its adsorption properties for both anionic and cationic dyes

High adsorption and desorption efficiencies for both anionic and cationic dyes are still a challenge for adsorbents to treat dyestuffs wastewater. In this study, the C8/threonine-functionalized mesoporous silica aerogel based on mixed-mode was constructed to overcome the challenge, with properties of hydrophobicity and switchable surface charge of n-octyl and threonine groups. With methylene blue and azophloxine as cationic and anionic dye models, batch tests were conducted. The consequences proofed the adsorption process was efficient and fast, and the highest adsorption quantities for methylene blue and azophloxine were estimated as 274.30 mg/g and 152.43 mg/g, respectively. Additionally, the adsorbent showed good removal efficiency and reusability. The desorption efficiencies exceeded 97% using low concentration HCl or NaOH as eluents. Mechanism investigation proved that adsorption process relied on hydrophobicity and electrostatic interactions. These results instructed that SG-C8/Thr was a promising adsorbent with excellent adsorption and desorption efficiencies for both anionic and cationic dyes.

Halloysite nanotubes (MHNTs) modified S-scheme g-C3N4/γ-Fe2O3 photocatalyst for enhancing charge separation and photocatalytic activity

Photocatalysis is a surface process and an increase in the adsorption of target molecules on the surface of a photocatalyst could be of prime necessity in the photodegradation efficiency enhancement of dyes. To attain such a purpose, this study equips g-C3N4 with pores-modified halloysite nanotubes (MHNTs), then gets it wrapped by γ-Fe2O3 nanoparticles with high specific surface area (SSA) and S-scheme mechanism through a one-pot synthesis and co-precipitation, respectively. Characterization of fabricated photocatalysts is conducted to detect physical, chemical, optical, magnetic, and electrical properties by XRD, FT-IR, XPS, FE-SEM, EDX+MAP, TEM, BET, DRS, PL, VSM, Photocurrent, and EIS analyses. This research introduces a novel, ternary nanocomposite (g-C3N4/MHNTs/γ-Fe2O3) with dual functionality towards adsorption of both anionic and cationic dyes. Modified halloysite nanotubes (MHNTs), due to predominant negative charges (Si-O) on their outer surface, perform a significant role in the separation of holes (h+) from the photocatalysts and higher adsorption in MB photodegradation. In contrast, the inner surface of MHNTs through positive charges of AL-OH is beneficial for the electron (e-) separation and MO treatment. MHNTs with mesopores structure (Mean pore diameter: 10.6 nm) and high specific surface area (76.25 m2/g) contribute to higher adsorption and rapid transfer of photoexcited charges to the surface of ternary photocatalyst (g-C3N4/MHNTs/γ-Fe2O3 – 59.06 m2/g). After adding γ-Fe2O3 to g-C3N4/MHNTs, band gap of g-C3N4/MHNTs/γ-Fe2O3 reduces to 2.70 eV from 2.85 eV of g-C3N4/MHNTs, indicating influential role of γ-Fe2O3 nanoparticles in shifting photocatalytic activity of the ternary photocatalyst towards larger wavelengths (≥ 900 nm), and real world’s application (under illumination of sunlight). Among fabricated photocatalysts, g-C3N4/MHNTs/γ-Fe2O3 excels at degrading both MB and MO with the efficiency of %99.99 in 60 min and %89.1 in 120 min, respectively. To recognize the photocatalytic mechanism of the ternary photocatalyst, a trapping experiment was utilized for detecting oxidizing radicals in the photocatalytic process and then a photocatalytic mechanism was proposed.

Magnetic chitosan-functionalized waste carton biochar composites for efficient adsorption of anionic and cationic dyes

In this study, BC-CoFe2O4-CS magnetic composite was successfully prepared from waste cardboard and investigated as an efficient adsorbent for the removal of amaranth and methyl orange in aqueous solution. First, the fibers obtained from the cardboard waste were carbonized by a hydrothermal process to produce biochar. Subsequently, the final magnetic composites were synthesized by in situ growth and Schiff base crosslinking reactions. The composites were characterized by zeta potential, Brunauer–Emmett–Teller measurements, Fourier transform Infrared spectroscopy, Scanning electron microscopy, Energy dispersive spectrometer,X-ray Diffraction, Thermogravimetry analysis and Vibrating sample magnetometer. The effects of adsorbent dosage and initial solution pH on dye removal efficiency were studied. The results showed that the maximum adsorption capacity of amaranth could reach 500.6 mg·g−1 at pH = 2, the adsorbent dosage of 0.5 mg·ml−1, and methyl orange could reach 644.0 mg·g−1 at pH = 4, the adsorbent dosage of 0.5 mg·ml−1. The adsorption process followed the pseudo-second order kinetic models and Langmuir isotherm. BC-CoFe2O4-CS was easily separated from the aqueous solution due to the loading of CoFe2O4 magnetic nanoparticles. Besides, the BC-CoFe2O4-CS could be further used after the adsorption experiments with or without desorption and still showed good adsorption performance in the actual water samples. Therefore, it is expected that the composite material prepared from waste cartons can be used for the treatment of dye-containing wastewater due to its low cost, high efficiency, and simple application.

A simple, efficient, and rapid method for dye removal from wastewater using an IDA-GO@Fe3O4 magnetic nanocomposite.

With the rapid advancement of the dye and textile industry, there has been increasing concern regarding the contamination of wastewater with dyes and its potential influence on human health. Therefore, the removal of dye pollutants from wastewater has become a matter of significant importance. In this study, a magnetically responsive iminodiacetic acid-functionalized graphene oxide (IDA-GO@Fe3O4) nanocomposite was utilized for the adsorption of both cationic and anionic dyes. The IDA-GO@Fe3O4 nanocomposite was synthesized and thoroughly characterized using several analytical techniques such as XRD, SEM, FT-IR, TGA and BET analysis. The prepared magnetic nanocomposite had a much higher thermal stability than pure graphene oxide. The negatively charged surface of the IDA-GO@Fe3O4 magnetic nanocomposite made it an excellent candidate for removing cationic dyes. The effects of various factors, including pH, initial concentration (isotherms), amount of adsorbent, and contact time (kinetics), on adsorption efficiency were investigated. The optimal conditions for the removal of methylene blue were determined to be 0.005 g of adsorbent, a pH of 10, and a contact time of 160 minutes. In contrast, the optimal conditions for the removal of methylene orange were found to be 0.005 g of adsorbent, a pH of 2, and a contact time of 120 minutes. Experimental data shows that the adsorption capacity for MB is reported as 437.10 mg g-1 at pH 10, while for MO it is 165.65 mg g-1 at pH 2. Furthermore, the adsorption process followed a pseudo-second-order kinetic model and Langmuir isotherm model. The proposed adsorption mechanism of MB and MO dyes onto the IDA-GO@Fe3O4 nanocomposite involve various interactions, such as electrostatic interactions, H-bonding, n-π, and π-π interactions. Importantly, the IDA-GO@Fe3O4 nanocomposite exhibited outstanding recyclability, retaining its effectiveness even after five successive cycles for MB. This suggests a straightforward method for developing high-performance IDA-GO@Fe3O4 magnetic nanocomposites for efficient wastewater purification and environmental remediation applications.

Hydrothermal synthesis of Mg/Al-layered double hydroxide modified water hyacinth hydrochar for remediation of wastewater containing mordant brown dye.

A high-performance dye adsorbent of Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH) was synthesized by a simple hydrothermal method. The surface functional groups, elemental composition, crystalline structure, and surface morphology of the prepared (MgAl@WH) were determined using different analytical techniques. The characterization results revealed that the (MgAl@WH) hydrochar surface offered more active adsorption sites, facilitating the mordant brown (anionic dye) adsorption, leading to its superior performance with much higher uptake capability (311.0 mg g-1 at 298 K) than Mg/Al double hydroxide nanosheets (MgAl DLHs, 80.2 mg g-1 at 298 K) and dried water hyacinth (WH, 10.0 mg g-1 at 298 K). The adsorption behavior of MgAL@WH follows the pseudo second order kinetic model (R2 = 0.999) and Langmuir isotherm model (R2 = 0.999). Moreover, MgAl@WH bonded efficiently with mordant brown dye via hydrogen bonding and interlayer anion exchange with monolayer formation. Additionally, the recycling tests revealed that the MgAl@WH can be reused over 10 cycles without significant change in the removal efficiency. Based on the obtained findings, Mg/Al-layered double hydroxide modified water hyacinth hydrochar (MgAl@WH), for its economic and environmental benefits, has recently been used as an efficient adsorbent to remediate industrial wastewater containing anionic dyes.

Highly efficient batch adsorption of anionic dye in wastewater using nanocomposite: Experimental and theoretical studies

The adsorptive properties of the Erionyl Red (ER) dye on bentonite (B) intercalated with cetyltrimethylammonium bromide (HDTMA-B) were investigated using experimental and statistical physics methods. The dye was then taken up by the intercalated bentonite from a real water sample. After intercalation, X-ray diffraction analysis indicates an increase in HDTMA-B basal spacing to 15.2 Ả. Scanning electron microscopy images show the formation of large particles and many cavities. The results revealed that the material had high properties to adsorb organic molecules (greater than 99 %). The Langmuir-Freundlich model, described the isotherms, whereas the second-order model better captured the kinetic of dye adsorption. The maximum ER uptake observed was 478 mg g−1 at a temperature of 328 K. Reusability of nanocomposite showed stability, over five cycles. Thermodynamic analysis suggested spontaneous (negative ΔG°) and endothermic (positive ΔH°) adsorption processes. The statistical physics model was also used to estimate the orientation of ER adsorption on the material. The oxygens connected to the dye in the HDTMA-B structure played in particular an important role in the adsorption mechanisms of dye. This study combines experiment data with a theoretical approach to provide a new explanation for the mechanism. The removal of dyes from wastewater, in particular Erionyl red, is vital for the protection of the environment and public health. Nanocomposite appears to be an effective, durable, and environmentally friendly adsorbent for the removal of Erionyl red dye from synthetic solutions and real wastewater.

Kinetics and Isotherms Studies on the Adsorption of Anionic Dyes and As (V) in Aqueous Solutions Employing Modified Chitosan-Alumina Nanocomposites (CSAO3 and CAO3)

Kinetics and Isotherms Studies on the Adsorption of Anionic Dyes and As (V) in Aqueous Solutions Employing Modified Chitosan-Alumina Nanocomposites (CSAO3 and CAO3)

Synthesis of 2-amino-terephthalic acid crosslinked chitosan/bentonite hydrogel; an efficient adsorbent for anionic dyes and laccase

This research article presents the fabrication of NH2-terephthalic acid crosslinked chitosan-bentonite composite, which adopted a facile synthesis approach and offered efficient adsorption capacity for organic dyes. A novel hydrogel material named CB 5:1 demonstrated remarkable adsorption for anionic dyes (Congo red (CR) and brilliant blue (BB)) while showing a negligible affinity for cationic dyes. Adsorption isotherm studies revealed the adsorption capacity of 4950 mg/g and 2053 mg/g (per g of composite's dry weight) for CR and BB following the Langmuir adsorption model. Kinetics and thermodynamic studies were also conducted while the adsorption of anionic dyes in the presence of metal ions, cationic dyes, anionic dyes, and in simulated water remained unaffected. Laccase, an industrially important enzyme, was also immobilized on CB 5:1 to achieve enzyme stability and reusability, resulting in a staggering immobilization capacity (4782 mg/g) at pH 6.0. Laccase immobilized product was employed to perform dye degradation (> 90 % for CR and > 75 % for BB), and the reusability was tested. Overall, our crosslinked product proved appealing for removing high concentrations of anionic organic dyes from polluted water and could be envisaged for practical use.

PH-sensitive multi-arm star polyampholytes: A novel approach for simultaneous adsorption of anionic and cationic dyes

This study introduces star-shaped polyampholyte adsorbents, comprising poly(acrylic acid) cores and poly(2-(dimethylamino)ethyl methacrylate) arms. Reversible addition fragmentation chain-transfer (RAFT) polymerization and distillation-precipitation approach were utilized to prepare star polyampholytes in different monomer/RAFT agent ratios (70, 130, and 200). Well-defined and star-like structures were validated employing proton nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. pH-dependent self-assembled particle morphologies were scrutinized using field emission scanning electron microscopy and dynamic light scattering. The adsorbents exhibited substantial potential for efficient dye removal from wastewater, attaining up to 76.6% adsorption (pH = 2) for methylene orange and 48.3% (pH = 10) for methylene blue in single-dye systems using Star AA_DMAEMA_200 and Star AA_DMAEMA_130, respectively. Dual-dye systems revealed captivating synergistic interactions, showcasing intricate behaviors between dyes. The influence of molecular weight intricacies on adsorption dynamics unveiled a spectrum of diverse trends, underscoring the absorbents' versatility. These findings not only deepen our understanding of the adsorption process but also underscore the paramount potential of star-shaped polyampholyte absorbents in addressing complex environmental color removal challenges.

Chitosan and silica nanoparticles-modified xanthan gum-derived bio-nanocomposite hydrogel film for efficient uptake of methyl orange acidic dye

In this contribution, a bio-nanocomposite hydrogel film (CS/XG.SiO2) of chitosan/silica NPs-modified xanthan gum was prepared via a facile solution casting blending approach and utilized to capture the anionic methyl orange (MO) from aqueous solution. A Taguchi standard method was used to optimize the hydrogel nanocomposite synthesis reaction conditions after comprehensive characterization using various techniques. Under various operating parameters, the hydrogel biofilm was tested for its effectiveness in adsorbing MO dye in a batch process. In agreement with Langmuir isotherm, the CS/XG.SiO2 biofilm was capable of adsorbing MO at a maximum capacity of 294 mg/g at pH 5.30, contact time 45 min, temperature 25 °C, and concentration (C0) 50 mg/L. Pseudo-second-order model and adsorption kinetics data well matched. The thermodynamic data indicate that adsorption occurred spontaneously and exothermically. The main mechanisms driving the adsorption are electrostatic interactions and hydrogen bonding between the CS/XG.SiO2 nanocomposite and the dye. Furthermore, the biofilm is regenerative, allowing for up to five reuses while maintaining a 75 % dye removal efficiency. This study highlights that the CS/XG.SiO2 hydrogel nanocomposite is an inexpensive, reusable, and eco-friendly bio-adsorbent that is capable of anionic dye adsorption.

Fabrication of network nanocomposite of polyaniline coating chitosan-graphene oxide-functionalized carbon nanotube and its efficacy in removing dyes from aqueous solution

In this investigation, we employed chemical oxidative copolymerization techniques to produce cross-linked polyaniline/chitosan-graphene oxide-oxidized single-wall carbon nanotubes (Cross PANI/Chito-GO-OXS NCs) as a network to increase the surface area, as well as the active centers to enhance the efficiency of the adsorption of anionic and cationic dyes. This novel material was utilized as an adsorbent for decontaminating water by eliminating acid red dye (AR1) and brilliant green dye (BG). Several analytical techniques were employed to assess the composition and structure of the synthesized adsorbent, including scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and Raman spectroscopy. To assess the efficacy of Cross PANI/Chito-GO-OXS NCs in dye removal, batch experiments were carried out under diverse conditions, such as varying pH, adsorbent quantity, agitation duration, ionic strength, and temperature. The results indicated that the optimum conditions for AR1 removal were achieved at pH 2, using 5 mg of Cross PANI/Chito-GO-OXS NCs at a concentration of 20 mg/L for 120 min. Conversely, for BG removal, the most favorable outcomes were observed at pH 6, with the use of 5 mg of Cross PANI/Chito-GO-OXS NCs at a concentration of 5 mg/L for 120 min. Under these operating conditions, the maximum removal efficiency for actual wastewater was determined to be 96.73% for AR1 dye and 95.55% for BG dye. Additionally, we analyzed the adsorption isotherm data utilizing various models. The adsorption kinetics were elucidated through a pseudo-second-order model, supported by regression data, which yielded R2 values of 0.9839 for AR1 and 0.9928 for BG, respectively, describing the adsorption of both dyes onto Cross PANI/Chito-GO-OXS NCs. Furthermore, the thermodynamic analysis revealed that the removal of AR1 dye is an endothermic process, while BG dye removal is exothermic, and both removal of AR1 and BG dyes are spontaneous and chemisorption processes.

Cationic and anionic dyes adsorption from wastewater by clay-chitosan composite: An integrated experimental and modeling study

Water contamination with organic dyes is a significant environmental concern because it results in serious problems that threaten public health. In this study, a clay-based composite from Safi City, coated with chitosan (Cs), was used as an adsorbent (SRC/Cs) to remove co-existing dyes (methylene blue (MB) and congo red (CR)) from aqueous solution. Characterization methods such as Fourier infrared transform spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDX, and zero charge point determination were performed to understand the adsorption mechanisms of the co-pollutants in the adsorbent’s surface. The effects of pertinent parameters, such as initial dye concentration, adsorbent's dose, reaction time, pH, and temperature, were optimized to maximize the adsorption of both anionic and cationic dyes. The Langmuir, Freundlich, and Temkin isotherm models were applied to simulate experimental data. The DFT method was used to identify the key mechanism for MB and CR adsorption. It was found that the composite with 30% (w/w) CS and 70% (w/w) clay showed a complete removal of the target dye with an initial dye concentration of 20 mg/L at optimized pH 2 (CR) and pH 4 (MB), 60 min of reaction time, and 600 rpm of agitation speed. The Langmuir model was suitable for modeling the MB dye adsorption, while the Temkin isotherm was representative to describe CR adsorption. The adsorption capacities of both MB and CR dyes were 97.08 mg/g and 80.9 mg/g, respectively. The kinetic study showed that their adsorption process followed the pseudo-second-order. Thermodynamic parameters such as ΔH0, ΔG0, and ΔS0 imply that the adsorption reaction was spontaneous and endothermic. Overall, this study implies the potential of the composite as a novel adsorbent for removing MB and CR in single and binary systems.

Ensemble meta machine learning for predicting the adsorption of anionic and cationic dyes from aqueous solutions using Polymer/graphene/clay/MgFeAl-LTH nanocomposite

Adsorption is one of the most promising wastewater treatment methods due to its simplicity and efficacy at ambient temperature and pressure. However, the technical and economic feasibility of this process largely depends on the performance of the utilized adsorbents. In this study, a promising adsorbent made of polyethyleneimine, graphene oxide (GO), bentonite, and MgFeAl-layered triple hydroxide (MgFeAl-LTH) has been synthesized and characterized. The results revealed that the synthesized nanocomposite (abbreviated as PGB-LTH) possesses good porosity and crystallinity. The adsorption performance of the PGB-LTH nanocomposite towards two harmful water pollutants (i.e., methyl orange (MO) and crystal violet (CV)) was investigated, and the results revealed that the nanocomposite outperforms its parental materials (i.e., GO, bentonite, and MgFeAl-LTH). The maximum adsorption capacity (qmax) of MO and CV onto the nanocomposite could reach 1666.7 and 1250.0 mg/g, respectively, as predicted using the Langmuir adsorption isotherm. Additionally, the PGB-LTH nanocomposite is highly reusable with an insignificant decline in performance upon repetitive use. In terms of thermodynamics, MO adsorption onto the nanocomposite is exothermic while CV adsorption is endothermic despite that both dyes adsorb spontaneously as revealed by the negative values of the Gibbs free energy change at all the examined temperatures. The generated adsorption data were utilized for constructing and assessing ensemble meta-machine learning techniques aimed at cost-effective simulation and prediction of the proposed adsorption method. Bagging and boosting methods were developed and evaluated intensively using the obtained adsorption data. The Extra Trees model achieved promising results as evidenced by the high correlation coefficient of 99% as well as low computed RMSE and MAE errors of 11.42 and 5.11, respectively, during the testing phase. These results demonstrate the model strong capability to effectively simulate and predict the adsorption process in question.

Pyridinium and trifluoromethanesulfonate bifunctional poly(ionic liquid)s for highly efficient and selective adsorption of anionic dyes

The efficient and selective removal of dyes from polluted water by low cost, durable, sustainable, and reusable adsorptions remain challenges. In this study, a pyridinium and trifluoromethanesulfonate bifunctional poly(ionic liquid)s, named Py-CF3SO3-PIL was prepared by co-polymerization of 4-vinyl pyridine (4VP), divinylbenzene (DVB) and styrene (ST), followed by quaternization with 1-bromobutane and anion exchange with lithium trifluoromethanesulfonate. The resulting bifunctional Py-CF3SO3-PIL exhibited remarkable adsorption capacity (2192 mg g−1) and efficiency (within 10 min) for selective removal (>99.9%) of methyl orange (MO) from (mixed) dye solutions. The superior adsorption capacity and selectivity of Py-CF3SO3-PIL towards the removal of MO was attributed to the strong electrostatic interactions and π-π stacking interaction between the adsorbent and MO dye. Detailed kinetic studies, adsorption isotherms, and thermodynamic experiments revealed an endothermic monolayer chemical adsorption mechanism of MO on Py-CF3SO3-PIL, which is perfectly matched with the Langmuir isotherm model (R2 > 0.999). Importantly, the Py-CF3SO3-PIL could be easily collected and regenerated for multiple repeated uses, highlighting its reusability. The exceptional adsorption capacity and selectivity towards anionic dyes make Py-CF3SO3-PIL a promising candidate for dye separation applications. Our findings will contribute to the rational design of functional poly(ionic liquid)s-based adsorbents for water purification.

Box-Behnken design optimization of bimetallic-organic frameworks for effective removal of tartrazine food dye from aqueous solutions

Lanthanum and tin-based hetero bimetallic organic frameworks (MOFs) in the form of stacked nanorods (La/Sn@MOF) exhibit promising capabilities in removing the yellow dye Tartrazine (E102) from aqueous solutions. Various techniques such as SEM, XRD, XPS, FTIR, and BET were employed to assess the adsorbent, revealing a significant surface area of 736.82 m2/g. The study thoroughly investigated the impact of pH, initial dye concentration, adsorbent dose, contact time, and temperature on the elimination of E102 dye. The clearance of tartrazine follows the Langmuir isotherm and pseudo-second-order kinetics, with a maximum adsorption capacity of 694.72 mg/g according to the Langmuir isotherm model. The pHzpc value of 6.41 suggests favorable adsorption of anionic dyes like E102 dye at pH levels below 6.4. The adsorption process was characterized by adsorption energy of 29.46 kJ/mol, indicating a chemisorption process. Thermodynamic analysis revealed that the adsorption processes were both endothermic and spontaneous, as evidenced by the negative values for ΔGo and positive values for ΔHo. La/Sn@MOF proved to be a straightforward and effective method for treating industrial wastewater, with the added benefit of being reusable for up to five cycles. Interaction between La/Sn@MOF and E102 dye was found to involve hydrogen bonding, pore filling, and π-π interactions, among other mechanisms. Optimization of the adsorption procedure was achieved using the Box-Behnken Design method (BBD).

Efficient adsorption of anionic and cationic dyes by PVA/PAA/GO composite hydrogel with three-dimensional porous double network structure

Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were introduced into graphene oxide (GO) by a water bath method, and PVA/PAA/GO (PPG) with a three-dimensional double network structure was prepared under the action of hydrogen bonding. With the help of a large number of oxygen-containing functional groups and a three-dimensional double network structure in the PPG composite hydrogel, the adsorption performance of anionic and cationic dyes was greatly improved, and the adsorption rates of 100 mg∙L−1 malachite green (MG) and Congo red (CR) within 6 min were 93 % and 55 %, respectively. For comparison, the adsorption rates of MG and CR by graphene hydrogel alone within 30 min were only 10 % and 48 %, respectively. Meanwhile, the free radical polymerization of PAA and PVA also effectively improved the mechanical strength of the graphene hydrogel, and the PPG remained structurally stable under the action of 800 g of gravity. The results of adsorption kinetics showed that the adsorption process of PPG on CR and MG was in accordance with Freundlich adsorption and pseudo-second-order kinetic adsorption. Based on the X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) results, the adsorption performance of PPG mainly originated from physical adsorption, electrostatic attraction, hydrogen bonding and π-π conjugation.

In situ polyaniline polymerization on electrospun cellulose acetate nanofibers derived from recycled waste filter butts of cigarettes for the enhanced removal of methyl orange and rhodamine

In this study, waste cigarette butts (CBs) were processed to produce electrospun cellulose acetate (CA) nanofibrous membranes modified with polyaniline (PANI) via chemical oxidation polymerization. This cost-effective method of preparing CA coated with PANI was initially investigated by comparing CA, CA-PANI, and CA-dPANI (as deprotonated PANI) for the rapid adsorption of cationic and anionic dyes. The results depicted CA-PANI with the highest dye removal capacity. As the optimum material, CA-PANI was applied to remove methyl orange (MO) and rhodamine chloride (RC) dye from an aqueous phase. Essential factors: contact time, solution pH, initial dye concentration, nanofiber dosage, and temperature of solution were evaluated with maximum equilibrium adsorption capacity and removal percentage achieved for MO as 24.87 mg/g and 99 %, for RC as 6.93 mg/g and 55 %, respectively. The adsorptive experimental data for both dyes best fitted the pseudo-second-order kinetic, intraparticle diffusion, and Freundlich models. Moreover, the thermodynamics result indicated the adsorption processes were exothermic and spontaneous in nature. Reusability studies also showed the stable performance of CA-PANI material for up to 7 adsorption-desorption cycles. The high dye removal efficiency suggests that the adsorbent material in the water filtration of azo dyes.