Design and preparation of a novel Mg-Al LDH@EDTA-Melamine nanocomposite for effective adsorptive removal of methylene blue and rhodamine B dyes from water.

This paper deals with the preparation of a novel nanocomposite consisted of magnesium-aluminum layered double hydroxide (Mg-Al LDH) and ethylenediaminetetraacetic acid (EDTA) as well as melamine (MA) as an adsorbent. This nanocomposite was utilized to adsorb different dyes such as rhodamine B (RhB) and methylene blue (MB) from water. The prepared adsorbent was characterized using FT-IR, EDS, XRD, TGA, and FE-SEM analyses. The effects of various parameters such as concentration, time, adsorbent dosage, temperature, and pH were tested to investigate their influence on adsorption conditions. Both methylene blue and rhodamine B dyes showed pseudo-second-order adsorption kinetics, and their adsorption followed the Langmuir isotherm. Moreover, the maximum adsorption capacities for methylene blue and rhodamine B were found to be 1111.103 mg/g at 45 °C and 232.558 mg/g at 60 °C, respectively. Additionally, the adsorption processes were found to be spontaneous (ΔG°< 0, for both dyes) and exothermic (ΔH° = -12.42 kJ/mol for methylene blue and ΔH° = -25.84 kJ/mol for rhodamine B) for both dyes. Hydrogen bonding and electrostatic forces are responsible for the interactions occur between the nanocomposite and the functional groups in the dyes. The experimental findings demonstrated a greater adsorption rate of MB than RhB, suggesting the adsorbent's stronger affinity for MB. This preference is likely due to MB's size, specific functional groups, and smaller molecule size, enabling stronger interactions and more efficient access to adsorption sites compared to RhB. Even after recycling 4 times, the dye adsorption percentages of the adsorbent for MB and RhB dyes were 90 % and 87 %, but the desorption percentages of the adsorbate dyes were 85 % and 80 %, respectively. The prepared adsorbent boasts several unique properties, such as the swift and effortless adsorption of MB and RhB dyes, straightforward synthesis, mild adsorption conditions, remarkable efficiency, and the ability to be recycled up to 4 times without a significant decrease in activity.

Green hybrid coagulants for water treatment: An innovative approach using alum and bentonite clay combined with eco-friendly plant materials for batch and column adsorption.

Textile industries contribute to water pollution through synthetic dye discharge. This study explores the use of natural bio-coagulants to remove acid dyes from wastewater, investigating factors like pH, coagulant dose, dye concentration, contact time, and temperature for optimal results. The optimum pH and coagulants capabilities of (CAAPP, CAAPH, CBAGL, CBAPP and CBAPH) were 3 (49.6 mg/g), 3 (42.5 mg/g), 3 (38.9 mg/g), 4 (35.7 mg/g), 4 (34.1 mg/g), and 4 (29.4 mg/g) respectively, while treating of selected BRF-221 dyes from water solution. The acidic range (3-4) was found to have the best pH for the maximal coagulation, and the optimal dose were found to be 0.05 g/50 mL. The equilibrium was attained within 45-60 min for all coagulants. After 60 min of shaking, the maximum coagulation capacities (21.9, 21.02, 16.5, 27.9, 25.3, and 23.4 mg/g) of several coagulant composites (CAAGL, CAAPP, CAAPH, CBAGL, CBAPP, CBAPH) were determined. The initial BRF-221 dye concentration in the range of 10-200 mg/L was considered as optimum for gaiting maximum elimination of dye using different coagulants. At a dye value of 100 mg/L of BRF-221, maximal coagulation capacities CAAGL (179.19 mg/g), CAAPP (166.06 mg/g), CAAPH (141.60 mg/g), and CBAGL (126.49 mg/g), CBAPP (113.9 mg/g), CBAPH (93.08 mg/g) were attained. The study found 35 °C to be the optimal temperature for maximum acid dye removal using bio-coagulants. Increasing temperature reduced coagulation capacity, indicating an exothermic process. Freundlich and Langmuir isotherms showed suitability for pseudo-first-order and pseudo-second-order kinetics in biosorption. Thermodynamic parameters were assessed for process feasibility. Effective coagulants demonstrated sensitivity to electrolyte variations. In column studies, adjusting parameters achieved maximum coagulation efficiency for removing BRF-221 dyes. The study successfully applied optimal parameters to remove real textile effluents at a practical scale. SEM, FT-IR, BET and XRD characterized coagulants, providing insights into stability and morphology.

Harnessing synergy: Polydopamine-hBN integration in electrospun nanofibers for Co (II) ion, methylene blue and crystal violet dyes adsorption.

In today's world, major pollutants, such as cationic dyes and heavy metals, pose a serious threat to human health and the environment. In this study, a novel adsorbent was created through the electrospinning of polyvinyl alcohol/polyacrylic acid (PVA/PAA), incorporated with hexagonal boron nitride (hBN) coated with polydopamine (PDA). The integration of hBN and PDA substantially enhanced the adsorption capacity of the PVA/PAA fibers, making them highly effective in adsorbing cationic dyes such as methylene blue and crystal violet, as well as cobalt (II) ions, from contaminated water. The adsorbents were assessed to understand how their adsorption behavior varies with pH, as well as to examine their adsorption kinetics and isotherms. The results indicate that the PVA/PAA-hBN@PDA adsorbent has maximum adsorption capacities of 1029.57 mg/g, 793.65 mg/g, and 62.46 mg/g for methylene blue, crystal violet, and cobalt (II) ions, respectively. This underscores the superior performance of the PVA/PAA-hBN@PDA adsorbent when compared to both the PVA/PAA and PVA/PAA-hBN adsorbents. The adsorption kinetics adhered to a pseudo-second-order model, indicating chemisorption, whereas the Langmuir model implied a monolayer adsorption. Overall, the findings of this study highlight the efficacy of harnessing the synergistic capabilities of hBN and PDA within the PVA/PAA-hBN@PDA adsorbents, providing an efficient and eco-friendly approach to removing cationic dyes and heavy metals from contaminated water, and thereby contributing to a cleaner and safer environment for all.

The Use of Various Types of Waste Paper for the Removal of Anionic and Cationic Dyes from Aqueous Solutions.

This study examined the possibility of using various types of waste paper-used newsprint (NP), used lightweight coated paper (LWC), used office paper (OP), and used corrugated cardboard (CC)-for the removal of anionic dyes, Acid Red 18 (AR18) and Acid Yellow 23 (AY23), and cationic dyes, Basic Violet 10 (BV10) and Basic Red 46 (BR46), from aqueous solutions. The scope of this research included the characterization of sorbents (FTIR, SEM, BET surface area, porosity, pHPZC, effectiveness of water coloration), determination of pH effect on the effectiveness of dye sorption, sorption kinetics (pseudo-first-order model, second-order model, intraparticular diffusion model), and the maximum sorption capacity (Langmuir models and Freundlich model) of the tested sorbents. The use of waste paper materials as sorbents was found to not pose any severe risk of aquatic environment contamination. AR18, AY23, and BV10 sorption intensities were the highest at pH 2, and that of RB46 at pH 6. The waste paper sorbents proved particularly effective in removing cationic dyes, like in the case of, e.g., NP, which had a sorption capacity that reached 38.87 mg/g and 90.82 mg/g towards BV10 and BR46, respectively, and were comparable with that of selected activated carbons (literature data).

Multiphase electroextraction of malachite green from surface water and its determination using digital imaging and chemometric tools.

This study introduces a novel method for the quantification of malachite green (MG), a pervasive cationic dye, in surface water by synergizing multiphase electroextraction (MPEE) with digital image analysis (DIA) and partial least square discriminant analysis. Aimed at addressing the limitations of conventional DIA methods in terms of quantitation limits and selectivity, this study achieves a significant breakthrough in the preconcentration of MG using magnesium silicate as a novel sorbent. Demonstrating exceptional processing efficiency, the method allows for the analysis of 10 samples within 20 min, exhibiting remarkable sensitivity and specificity (over 0.95 and 0.90, respectively) across 156 samples in both training and test sets. Notably, the method detects MG at low concentrations (0.2 µg L-1) in complex matrices, highlighting its potential for broader application in environmental monitoring. This approach not only underscores the method's cost-effectiveness and simplicity but also its precision, making it a valuable tool for the preliminary testing of MG in surface waters. This study underscores the synergy among MPEE, DIA, and chemometric tools, presenting a cost-efficient and reliable alternative for the sensitive detection of water contaminants.

Sustainable Bio-Based Adsorbents for Simultaneous and Efficient Removal of Hazardous Dyes from Aqueous Solutions.

Dyes provide a notable environmental issue as a result of their intrinsic poisonous and carcinogenic characteristics. An estimated 60,000 metric tons of dyes has been discharged into the environment, leading to a substantial increase in water pollution. The mitigation of these dyes is a substantial and intricate challenge. The primary objective of this research is to conduct a comprehensive analysis of the adsorption of cationic dyes containing positively charged groups such as sulphonates, amines, and triphenylmethanes. The adsorption study was carried out using four different low-cost adsorbents derived from biowaste, specifically Groundnut Shell (GS), Mosambi Peel (MP), Mango Bark (MBARK), and Mango Leaves (ML). The adsorbent materials were characterized using FTIR, UV-Vis spectroscopy, scanning electron microscopy (SEM), point-of-zero charge (PZC), and BET techniques. The adsorption capacity was found to be between 1.5 and 2.2 mg/gm for Groundnut Shell, Mosambi Peel, Mango Bark, and Mango Leaves for individual dye removal (Crystal violet, Methylene blue, Rhodamine B, and Malachite green). It was observed that adsorbent derived from mango bark showed excellent adsorption (%) in a mono-component dye system and, thus, was explored for the simultaneous removal of a mixture of the same dyes. MBARK exhibited an excellent overall dye removal efficiency of 94.44% (Qe = 2.7 mg/g) for the dye mixture in 60 min. From a detailed kinetic investigation, it was concluded that the adsorption followed the pseudo-second-order model (R2= 0.99963 to 1 for different dyes and adsorbents) hinting at chemisorption. The effect of the pH of the analyte solution and the dosage of adsorbent was also studied for simultaneous removal. The isothermal studies demonstrated that the Langmuir adsorption model (R2 = 0.99416) was the best-fitted model, suggesting monolayer adsorption. The adsorption process was predicted to be governed by ion exchange, electrostatic interaction, hydrogen bonding, pi-pi interaction, etc., based on charge, functional groups, and pH of dyes and adsorbent. Thus, this study highlights the application of low-cost biowaste as a potential adsorbent for the mitigation of toxic industrial dyes present in wastewater.

Cellulose Nanofibrils-Reinforced Pectin Membranes for the Adsorption of Cationic Dyes from a Model Solution.

In the presented research, a facile, one-step method for the fabrication of cellulose nanofibrils/pectin (CNFs/PC) membranes is described, which were tested further for their ability to remove cationic dyes from the prepared model solutions. For this purpose, ten membranes were prepared with different quantities of CNFs and PC with/without citric acid (CA) or CaCl2 as mediated crosslinking agents, and they were characterised comprehensively in terms of their physical, chemical, and hydrophilic properties. All the prepared CNFs/PC membranes were hydrophilic with a Water Contact Angle (WCA) from 51.23° (without crosslinker) up to 78.30° (CaCl2) and swelling of up to 485% (without crosslinker), up to 437% (CaCl2) and up to 270% (CA). The stability of membranes was decreased with the increase in PC; thus, only four membranes (M1, M2, M3 and M5) were stable enough in water after 24 h, and these were additionally applied in the adsorption trials, using two structurally different cationic dyes, i.e., C.I. Basic Yellow 28 (BY28) and C.I. Basic Blue 22 (BB22), in four concentrations. The highest total surface charge of M3 (2.83 mmol/g) as compared to the other membranes influenced the maximal removal efficiency of both dyes, up to 37% (BY28) and up to 71% (BB22), depending on the initial dye concentration. The final characteristics of the membranes and, consequently, the dye's absorption ability could be tuned easily by changing the ratio between the CNFs and PC, as well as the type and amount of crosslinker.

Chitosan-grafted salicylaldehyde/algae composite for methyl violet dye removal: adsorption modeling and optimization.

In this study, a hydrothermal approach was employed to graft chitosan (Chit)/algae (ALG) with salicylaldehyde (SA), resulting in the synthesis of a biocomposite named salicylaldehyde-based chitosan Schiff base/algae (Chit-SA/ALG). The main objective of this biocomposite was to effectively remove methyl violet (MV), an organic dye, from aqueous solutions. The adsorption performance of Chit-SA/ALG toward MV was investigated in detail, considering the effects of three factors: (A) Chit-SA/ALG dose (ranging from 0.02 to 0.1 g/100 mL), (B) pH (ranging from 4 to 10), and (C) time (ranging from 10 to 120 min). The Box-Behnken design (BBD) was utilized for experimental design and analysis. The experimental results exhibited a good fit with both the pseudo-second-order kinetic model and the Freundlich isotherm, suggesting their suitability for describing the MV adsorption process on Chit-SA/ALG. The maximum adsorption capacity of Chit-SA/ALG, as calculated by the Langmuir model, was found to be 115.6 mg/g. The remarkable adsorption of MV onto Chit-SA/ALG can be primarily attributed to the electrostatic forces between Chit-SA/ALG and MV as well as the involvement of various interactions such as n-π, π-π, and H-bond interactions. This research demonstrates that Chit-SA/ALG exhibits promising potential as a highly efficient adsorbent for the removal of organic dyes from water systems.

The novelty of this work comes from introducing a new bio-organic based composite adsorbent of chitosan (Chit) biopolymer and algae (ALG) biomass. Moreover, the functionality and chemical stability of Chit­ALG composite was further developed by grafting process with salicylaldehyde (SA) using hydrothermal process. The incorporation of ALG biomass into polymeric matrix of Chit and grafting process with SA makes Chit a unique hybrid adsorbent toward cationic dye (methyl violet dye).

Revealing the interface chemistry of polyaniline grafted biomass via statistical modeling of multi-component dye systems: optimization, kinetics, thermodynamics, and adsorption mechanism.

The growing need to examine the adsorption capabilities of innovative materials in real-world water samples has encouraged a shift from single to multicomponent adsorption systems. In this study, a novel composite, PANI-g-SM was synthesized by covalently grafting a lignocellulosic biomass, Saccharum munja (SM) with polyaniline (PANI). The as-synthesized composite was investigated for the simultaneous adsorption of cationic (Methylene Blue (MB); Crystal Violet (CV)) and anionic dyes (Reactive Red 35 (RR); Fast Green FCF (FG)) from four single components and two binary systems, MB + RR and CV + FG. Further, the effect and interaction of pH (2-11), dosage (0.01-0.04 g/10 mL), and initial concentration (0.0313 to 0.1563 mmol/L) on the elimination of dyes by PANI-g-SM were studied through a novel design of Box-Behnken of Response Surface Methodology (RSM) technique which was found to be highly useful for revealing the chemistry of interfaces in multi-component systems. The extended Langmuir model for the binary system indicated the presence of synergism, as result the maximum monolayer adsorption capacity increased by 44.44%, 645.83%, 67.88%, and 441.07% for MB, RR, CV, and FG dye, respectively. Further, the adsorption process mainly followed a pseudo-second-order kinetic model, and the thermodynamic studies revealed the exothermic nature of adsorption for RR and FG dye while endothermic for MB and CV dye, respectively with Δ G varying from - 1.68 to - 6.12 kJ/mol indicating the spontaneity of the process. Importantly, the efficacy of the composite was evaluated for the treatment of textile industry effluent highlighting its potential as an adsorbent for wastewater treatment.

Synergistically enhancing the selective adsorption of cationic dyes through copper impregnation and amino functionality into iron-based metal-organic frameworks.

Dyes contaminating the sewages have seriously threatened the living beings and their separation from wastewater in terms of potential resource recovery is of high value. Herein, both of metal node doping and ligand group grafting were taken into account to enhance the adsorption selectivity of Fe-MOFs towards cationic dyes. The positive correlation between copper doping amount and selective coefficient (∂MOMB) for methylene blue (MB) over methyl orange (MO) within a certain range was mainly attributed to the increased surface negative charges via partial replacement of Fe(III) with Cu(II). Moreover, the amount of surface negative charges was further increased after amino functionalization and there was a synergism between Cu(II) and -NH2 in selectivity enhancement. As a result, Fe0.6Cu0.4-BDC-NH2 exhibited a 22.5-times increase in ∂MOMB and other cationic dyes including malachite green (MG) and rhodamine B (Rh. B) could also be selectively separated from binary and quaternary mixed dye systems. Moreover, Fe0.6Cu0.4-BDC-NH2 showed many superiorities like a wide pH range of 4.0-8.0, strong anti-interference ability over various inorganic ions, good recyclability, and stability. The adsorption kinetics and isotherm suggested that the MB adsorption process was a homogeneous single-layer chemisorption. Additionally, the thermodynamics manifested that the overall process was exothermic and spontaneous. According to the FT-IR and XPS spectra analysis, the electrostatic interaction and hydrogen bonding were determined as the main driving forces, and π-π interaction also contributed to the adsorption process.

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

Coal based solid waste has been recognized as a sustainable raw material for the preparation of high added value materials for wastewater treatment. In this paper, a preparation route was designed for the rapid, efficient, and low-cost preparation of MCM-41 zeolite using coal gasification fine slag as raw material. Functionalization modification of MCM-41 was carried out by grafting amino groups on its surface to improve its application performance. Moreover, the prepared functionalized material is used for bidirectional adsorption of anionic and cationic dyes. The experimental results indicate that MCM-41 zeolite with highly ordered pore structure was rapidly prepared using the advantages of fast heating and strong permeability of microwave synthesis method, with a specific surface area of up to 862.03 m2/g. Amine functionalized MCM-41 exhibits strong adsorption capacity for both cationic and anionic dyes, with maximum adsorption capacities for methylene blue and Congo red being 292.40 mg/g and 354.61 mg/g, respectively. The study of adsorption kinetics and adsorption mechanism indicate that the adsorption process is mainly controlled through chemical adsorption, including electrostatic attraction, hydrogen bonding, and π-π interactions. The results of this study will provide useful references for the use of coal based solid waste to prepare functional materials for the treatment of organic wastewater.

Reshaping environmental sustainability: Poultry by-products digestate valorization for enhanced biochar performance in methylene blue removal.

Anaerobic digestion is a highly effective and innovative method for treating organic waste while simultaneously generating energy. However, the treatment of the resulting digestate remains a challenging endeavor. To address this issue, poultry by-products digestate is used in this study to prepare biochars at two different pyrolysis temperatures (500/600 °C). Despite their potential, the utilization of untreated biochar is restricted due to its inadequate adsorption capacity. Therefore, each biochar was chemically activated using either HNO3 or KOH to synthesize four activated biochars (BC5@KOH, BC6@HNO3, BC5@HNO3, and BC6@HNO3). The aim is to investigate how the nature of chemical activation and pyrolysis temperature influence the adsorption of methylene blue dye. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Raman analysis, and pHpzc determination, were exploited to comprehensively elucidate the structure and composition of both unprocessed and chemically activated biochars. Among the activated biochars, the adsorbent BC5@HNO3 exhibits the highest methylene blue (MB) adsorption capacity, reaching 101.72 mg.g-1 at 298 K under (pH = 2, ads dose = 0.6 g.L-1, shaking time of 20 min, as optimal conditions for MB adsorption. Adsorption data for each adsorbent strongly aligns with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Moreover, the thermodynamic study reveals that the adsorption process was endothermic and spontaneous. The adsorption mechanism of MB dye was explored using various analytical techniques, including FTIR, SEM, PZC, and pH impact assessment. The findings suggest correlations with electrostatic interactions, hydrogen bonding, pore filling, as well as n-π and π-π interactions. Apparently, activated biochars play a crucial role in efficiently removing methylene blue dye, showcasing their potential as environmentally friendly and effective adsorbents.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem.

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

Adsorption of some cationic dyes onto two models of graphene oxide.

CONTEXT: The search for highly efficient adsorbent materials remains a significant requirement in the field of adsorption for wastewater treatment. Computational study can highly contribute to the identification of efficient material. In this work, we propose a computational approach to study the adsorption of four cationic basic dyes, basic blue 26 (BB26), basic green 1 (BG1), basic yellow 2 (BY2), and basic red 1 (BR1), onto two models of graphene oxide as adsorbents. The main objectives of this study are the assessment of the adsorption capacity of the graphene oxide towards basic dyes and the evaluation of the environmental and temperature effects on the adsorption capacity. Quantum theory of atoms in molecules (QTAIM) analysis has been used to understand the interactions between the dyes and graphene oxides. In addition, adsorption free energies of the dyes onto graphene oxides are calculated in gas and solvent phases for temperatures varying from 200 to 400 K. As a result, the adsorption free energy varies linearly depending on the temperature, highlighting the importance of temperature effects in the adsorption processes. Furthermore, the results indicate that the environment (through the solvation) considerably affects the calculated adsorption free energies. Overall, the results show that the two models of graphene oxide used in this work are efficient for removing dyes from wastewater. METHODS: We have optimized the complexes formed by the interaction of dyes with graphene oxides at the PW6B95-D3/def2-SVP level of theory. The SMD solvation model realizes the implicit solvation, and water is used as the solvent. Calculations are performed using the Gaussian 16 suite of program. QTAIM analysis is performed using the AIMAll program. Gibbs free energies as function of temperature are calculated using the TEMPO program.

Electrophoretically deposited sulfonated poly(styrene-co-divinylbenzene) on a screw for microextraction of cationic dyes from aqueous solutions.

In the present work, a novel solid-phase microextraction on a screw (MES) was employed to extract cationic dyes (malachite green, methylene blue, and rhodamine B) from food samples and fish breeding pool water. The sulfonated poly(styrene-co-divinylbenzene) was electrophoretically deposited on the surface of the grooves of a screw. Then the screw was placed inside a silicon tube as a holder to create a channel to run a test solution through it. The extracted dyes on the coated screw were eluted by a suitable eluent. High-performance liquid chromatography with an ultraviolet/visible detector was utilized for the separation and analysis of the analytes. The effective parameters of the analyte extraction efficiency were optimized. Under optimum conditions, the limits of detection were 0.15 µg/L, and calibration curves were linear in the range of 0.50-250.00 µg/L, with coefficients of determination > 0.989 for all studied dyes. The relative standard deviations of intra and inter-day (n = 3) were in the range of 2.8%-7.0% and 7.0%-9.5%, respectively. The MES was applied as a simple and repeatable method with acceptable relative recoveries (82.0%-103.0%) for the determination of cationic dyes in grape nectar, ice pop, jelly powder, and fish breeding pool water.

An Anionic Porous Indium-Organic Framework with Nitrogen-Rich Linker for Efficient and Selective Removal of Trace Cationic Dyes.

Metal-organic frameworks (MOFs) with porosity and functional adjustability have great potential for the removal of organic dyes in the wastewater. Herein, an anionic porous metal-organic framework (MOFs) [Me2NH2]2In2[(TATAB)4(DMF)4]·(DMF)4(H2O)4 (HDU-1) was synthesized, which is constructed from a [In(OOC)4]- cluster and a nitrogen-rich linker H3TATAB (4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoic acid). The negatively charged [In(OOC)4]- cluster and uncoordinated -COOH on the linker result in one unit cell of HDU-1 having 8 negative sites. The zeta potential of -20.8 mV dispersed in pure water also shows that HDU-1 possesses negatively charged surface potential. The high electronegativity, water stability, and porosity of HDU-1 can facilitate the ion-exchange and Coulombic interaction. As expected, the HDU-1 exhibits high selectivity and removal rates towards trace cationic dyes with suitable size, such as methylene blue (MB) (96%), Brilliant green (BG) (99.3%), and Victoria blue B (VB) (93.6%).

ß-Cyclodextrin network crosslinked by novel phosphonium-based tetrakiscarboxylic acid derived from PH3 tail gas: Synthesis and application for rapid removal of organic dyes from wastewater.

Organic dyes, such as methyl orange (MO), Congo red (CR), crystal violet (CV) and methylene blue (MB), are common organic pollutants existing in wastewater. Therefore, the exploration of bio-based adsorbents for the efficient removal of organic dyes from wastewater has gained many attentions. Here, we report a PCl3-free synthetic method for the synthesis of phosphonium-containing polymers, in which the prepared tetrakis(2-carboxyethyl) phosphonium chloride-crosslinked ß-cyclodextrin (TCPC-ß-CD) polymers were applied to the removal of dyes from water. The effects of contact time, pH (1-11), and dye concentration were investigated. The selected dye molecules could be captured by the host-gest inclusion of ß-CD cavities, and the phosphonium and carboxyl groups in the polymer structure would respectively facilitate the removal of cationic dyes (MB and CV) and anionic dyes (MO and CR) via electrostatic interactions. In a mono-component system, over 99 % of MB could be removed from water within the first 10 min. Based on the Langmuir model, the calculated maximum adsorption capacities of MO, CR, MB, and CV were 180.43, 426.34, 306.57, and 470.11 mg/g (or 0.55, 0.61, 0.96 and 1.15 mmol/g), respectively. Additionally, TCPC-ß-CD was easily regenerated using 1 % HCl in ethanol, and the regenerative adsorbent still showed high removal capacities for MO, CR, and MB even after seven treatment cycles.

ß-cyclodextrin grafted multi-walled carbon nanotubes/chitosan (MWCNT/Cs/CD) nanocomposite for treatment of methylene blue-containing aqueous solutions.

ß-cyclodextrin (CD) was grafted with multi-walled carbon nanotubes/chitosan (MWCNTs/Cs) to obtain MWCNTs/Cs/CD nanocomposite (NC) for methylene blue (MB) adsorption from aqueous media. TEM, XRD, TGA, Raman spectra, and BET & BJH analyses were utilized to characterize and confirm the successful synthesis of as-prepared NC. MB capture was investigated by considering the parameters of pH (1.9-9.0), temperature (∼16-63 °C), sonication time (∼5-15 min), MB concentration (∼1.2-48 mg/L), and NC dose (0.03-0.26 mg). The obtained responses were then modelled using CCD, generalized regression neural network (GRNN), and least squares support vector machine (LS-SVM), of which the latter found to provide most reliable and accurate results (RMSE = 0.0235, MAE = 0.020, AAD = 0.0047, and R2 = 0.999). Moreover, the genetic algorithm-based optimization results showed that under the respective values of 7.05, 45.5 °C, 10 min, 23 mg/L, 0.12 g, MWCNTs/Cs/CD NC would be able to remove 96.75% of MB with an adsorption capacity of 603 mg/g, through different mechanisms mainly electrostatic interactions. Following from Dubinin-Radushkevich (D-R) isotherm (qs = 460.66 ± 8.9 and R2 > 0.99) and intraparticle diffusion kinetic (R2 = 0.75-0.90) models indicated a chemical adsorption mechanism. Besides, thermodynamic parameters (ΔH◦ = -66.9 kJ/mol, ΔG◦ = between -3.77 kJ/mol and -8.52 kJ/mol, and ΔS◦ = 237.1818 J/mol K) confirmed an endothermic and spontaneous nature for the adsorption. These findings along with appropriate recyclability (five times), turn the as prepared NC to a promising material in removing MB from aqueous solutions.

Chitosan/carboxymethylcellulose polyelectrolyte complexes (PECs) are an effective material for dye and heavy metal adsorption from water.

Granular macroscopic chitosan/carboxymethylcellulose polyelectrolytic complexes (CHS/CMC macro-PECs) were produced and tested as adsorbents for six pollutants often present in wastewaters: sunset yellow (YS), methylene blue (MB), Congo red (CR) and safranin (S), cadmium (Cd2+) and lead (Pb2+). The optimum adsorption pH values at 25 °C were 3.0, 11.0, 2.0, 9.0, 10.0, and 9.0 for YS, MB, CR, S, Cd2+, and Pb2+, respectively. Kinetic studies indicated that the pseudos-econd order model best represented the adsorption kinetics of YS, MB, CR, and Cd2+, whereas the pseudo-first order model was the most suitable for S and Pb2+ adsorption. The Langmuir, Freundlich, and Redlich-Peterson isotherms were fitted to experimental adsorption data, with the Langmuir model providing the best fit. The maximum adsorption capacity (qmáx) of CHS/CMC macro-PECs for the removal of YS, MB, CR, S, Cd2+, and Pb2+ was 37.81, 36.44, 70.86, 72.50, 75.43, and 74.42 mg/g, respectively (corresponding to 98.91 %, 94.71 %, 85.73 %, 94.66 %, 98.46 %, and 97.14 %). Desorption assays showed that CHS/CMC macro-PECs can be regenerated after adsorbing any of the six pollutants studied, with possibility of reuse. These results provide an accurate quantitative characterization of the adsorption of organic and inorganic pollutants on CHS/CMC macro-PECs, indicating a novel technological applicability of these two inexpensive, easy-to-obtain polysaccharides for water decontamination.

Magnetite carboxymethylcellulose as biological macromolecule-based absorbent for cationic dyes removal from environmental samples.

In this study, magnetite carboxymethylcellulose (CMC@Fe3O4) composite as magnetic biological molecules were synthetized for the use as adsorbent to remove four types of cationic dyes, namely Methylene Blue, Rhodamine B, Malachite Green, and Methyl Violet from aqueous solution. The characteristic of the adsorbent was achieved by Fourier Transform Infrared Spectroscopy, Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction, Vibrating Sample Magnetometer and Thermal Gravimetric Analysis techniques. Besides, essential influencing parameters of dye adsorption; the solution pH, solution temperature, contact time, adsorbent concentration and initial dye dosage were studied. FESEM analysis showed the magnetic Fe3O4-TB, Fe3O4@SiO2, Fe3O4@SiO2-NH2 and CMC@Fe3O4 composites were in spherical shape, with average size of 43.0 nm, 92.5 nm, 134.0 nm and 207.5 nm, respectively. On the saturation magnetization (Ms), the results obtained were 55.931 emu/g, 34.557 emu/g, 33.236 emu/g and 11.884 emu/g. From the sorption modelling of Isotherms, Kinetics, and Thermodynamics, the adsorption capacity of dyes is (MB = 103.33 mg/g), (RB = 109.60 mg/g), (MG = 100.08 mg/g) and (MV = 107.78 mg/g). With all the adsorption processes exhibited as exothermic reactions. The regeneration and reusability of the synthetized biological molecules-based adsorbent was also assessed.