Adsorption Of Cationic Dyes Research Articles

Adsorption of cationic dye onto Raphanus seeds: optimization, adsorption kinetics, thermodynamic studies

Dyes are one of the common contaminants in industrial wastewater. Adsorption is the most widely method which used to treat dye-contaminated water due to their easy use, cost-effectiveness, and their efficiency was high. The aim of this study is the investigating of the utilization of the activated carbon which prepared from Raphanus seeds solid residual (ACRS) as a low cost adsorbent for removing of cationic Methylene Blue dye (MB)from wastewater. measuring the surface area using BET methods and SEM. The FT‒IR and XRD was measured. Different variables (e.g.: initial concentration of the dye, pH, contact time, and dosage) have been studied. Process has been systematically investigated experimentally at (25 ± 1 °C). The % removal of MB reached 99.4% after 90-min MB adsorption (40 mg/L) was observed within 5 min of contact time for the Raphanus seeds solid residual (ACRS) dosage of 4 g/L. MB initial concentration (10 ppm) Raphanus seeds solid residual (ACRS) effectively adsorbed MB (> 99%) over a widely range of pH (from pH 2 to pH 8). However, a swift decline in removal was observed when the pH was set at 7. The results of the adsorption kinetics analysis indicate a strong correlation with the pseudo-second-order model, as evidenced by the high regression coefficients. However, the adsorption capacity diminished with a rise in temperature. Thermodynamic calculations of (MB) onto Raphanus seeds solid residual (ACRS) is an exothermic reaction. The results have been indicated that the effectiveness of MB removal by activated carbon prepared from Raphanus seeds solid residual is favorable under neutral conditions, Raphanus seeds solid residual (ACRS) can be considered an efficient, environmentally friendly, readily available, and economical adsorbent that could treat industrial wastewater contaminated with cationic textile dyes. The objective of the experiments was to investigate the impact of various factors on the response of a process or formulation. To accomplish this goal, response surface methodology (RSM) has employed as a statistical model. RSM is an efficient and effective method for optimizing processes through the use of a quadratic polynomial model. The utilization of RSM allows for a reduction in the number of experiments needed, thus minimizing the associated costs of extensive analysis. This method has been done using Box–Behnken Design (BBD) to optimize % removal of MB. The optimal conditions as obtained from the RSM is pH 7,contact time 120 min, initial concentration 10 ppm, ACRS dosage 1 g, adsorption temperature 45 °C.

Efficient adsorption of cationic dyes by a novel honeycomb-like porous hydrogel with ultrahigh mechanical property

The optimization of hydrogel structure is crucial for adsorption capacity, mechanical stability, and reusability. Herein, a chitosan and laponite-XLS co-doped poly(acrylic acid-co-acrylamide) hydrogel (CXAA) with honeycomb-like porous structures is synthesized by cooperative cross-linking of 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and laponite-XLS in reticular frameworks of acrylic acid (AAc) and acrylamide (AM). The CXAA exhibits extraordinary mechanical performances including tough tensile strength (3.36 MPa) and elasticity (2756 %), which facilitates recycling in practical adsorption treatment and broadens potential applications. Since the regular porous structures can fully expose numerous adsorption sites and electronegative natures within polymer materials, CXAA displays efficient and selective adsorption properties for cationic dyes like methylene blue (MB) and malachite green (MG) from mixed pollutants and can reach record-high values (MB = 6886 mg g−1, MG = 11,381 mg g−1) compared with previously reported adsorbents. Therefore, CXAA exhibits promising potential for separating cationic and anionic dyes by their charge disparities. Mechanism studies show that the synergistic effects of HACC, laponite-XLS, and functional groups in monomers promote highly efficient adsorption. Besides, the adsorption capacity of CXAA remains stable even after undergoing five cycles of regeneration. The results confirm that CXAA is a promising adsorbent for effectively removing organic dyes in wastewater.

Thermodynamics, kinetic study and equilibrium isotherm analysis of cationic dye adsorption by ternary composite

This article investigates the kinetics, equilibrium, and thermodynamics of brilliant green dye adsorption on Fe3O4/CdS/MWCNTs. The effects of adsorbent dosage (0.01–0.06 g), contact time (1–120 min), temperature (278, 288,298 and 308 K), ionic strength (NaCl and CaCO3 salt), and initial solution pH (4,6,7, and 10) were all studied in relation to the adsorption of BG dye. Langmuir (R2 = 0.86883), Temkin (R2 = 0.96323) and Freundlich (R2 = 0.96958) and isotherms were fitted to describe the equilibrium of BG adsorption process. Isothermal models showed that BG adsorption was a favorable process on ternary composite Adsorption kinetics were well fitted by Pseudo-second order kinetic model (R2 = 0.99396). The thermodynamic parameters ΔH° = −0.0277 kJ.mol−1 and ΔS° = −60.9031 J mol−1.k−1 indicate endothermic and spontaneous adsorption process, (ΔG° > 0) non-spontaneous, and exothermic. Five adsorption/desorption cycles were demonstrated by the adsorbents’ high reusability.

Surface‐Modified Mesoporous V2‐xSb2xO5‐δ Ceramics for Improving the Electrostatic Chemisorption of Methylene Blue

AbstractHerein, mesoporous V2‐xSb2xO5‐δ (Sb−V−O) compounds, encompassing a compositional range of x varying between, 0.05≤x≤0.08, with orthorhombic Pmmn space group symmetry, are synthesized by high‐temperature solid‐state reaction method. Scanning electron microscopy indicated the formation of microscale rods and flakes and EDS spectra affirmed the stoichiometric precision of their composition adhering to the formulated chemical formula. Nitrogen adsorption isotherms exhibited the distinctive type IV pattern, accompanied by an H3 hysteresis loop, signifying the formation of mesoporous micro rods and flakes. Brunauer‐Emmett‐Teller measurements demonstrated an augmented surface area, ranging from 16.67–28.74 m2/g, mirroring the effect of the increase in the concentration of Sb cations. The study demonstrated complete Methylene Blue dye removal within a brief 90 minute period, highlighting its efficacy in water remediation. The adsorption kinetics was aptly described by the pseudo‐second‐order model which exhibited a high degree of fit (R2=0.99). Freundlich adsorption isotherm was used to describe the multilayer adsorption of MB dye on the Sb−V−O surface indicating an exponential increase in adsorption active sites. Enhanced cationic MB dye adsorption on negative Sb−V−O surface is attributed to the electrostatic chemisorption by the interaction of NMe2+ on the negative surface modified Sb−V−O compounds.

Facile in-situ fabrication of graphene oxide/poly(ionic liquid) composites and their adsorption performance for methyl orange

This work reveals a facile in-situ fabricating strategy for graphene oxide/poly(ionic liquid) composites toward the effective adsorption of methyl orange in aqueous solution. This synthetic route includes the formation of novel surfactant-free ionic liquid microemulsions and the stable solubilization of graphene oxide. To characterize the designed composites, FTIR, XRD, TGA, SEM, DSC, and XPS analyses were conducted, and the adsorption isotherms/kinetics of the designed composites toward methyl orange were further investigated. Results indicated that graphene oxide/poly(ionic liquid) composites can be in-situ synthesized facilely within the surfactant-free ionic liquid microemulsions, and the network structure of composites can be adjusted effectively by altering the dosage of co-solvent. In addition, the graphene oxide/poly(ionic liquid) composites prepared in situ exhibited a remarkable adsorption performance of methyl orange. These findings indicate the great application potential of graphene oxide/poly(ionic liquid) composites in the field of cationic dye adsorption.

Quinoline and cholesterol based organogelator for selective adsorption of cationic dyes

A novel quinoline and cholesterol based organogelator G1 has been successfully synthesized and characterized. G1 could form stable organogels in ethanol, n-propanol, n-butanol, isobutanol, acetone and ethyl acetate (EA), and the concentration-dependent 1HNMR revealed that hydrogen bonding, π-π stacking and van der Walls interaction were the main driving force to form organogels via the self-assembly of G1. Furthermore, the G1-EA gel realized selective adsorption properties for cationic dyes, such as malachite green (MG), brilliant green (BG), rhodamine B (RB) and crystal violet (CV). The results revealed that at pH = 9.90, c0 = 18 mg·L−1, the adsorption process of G1-EA gel for MG reached equilibrium in 7 h, and the removal rate was 99.13 %. The selective adsorption experiments of the G1-EA gel indicated that the cationic dyes (MG and BG) were efficiently adsorbed out of the mixed dyes solutions. Also, the adsorption isotherm and the adsorption kinetics for the adsorption process were investigated, the results suggested that the Freundlich equation and the quasi-second-order kinetic model were more appropriate to describe the adsorption process.

Selective Adsorption of Dyes and Fe3+ Sensing via Tb3+ Incorporation in an Anionic Cadmium-Organic Framework.

A three-dimensional (3D) anionic cadmium-organic framework, namely [(CH3)2NH2][Cd1.5(DMTDC)2] ⋅ 2DMA ⋅ 0.5H2O (Cd-MOF; DMA=N,N-dimethylacetamide), was successfully synthesized under solvothermal conditions by using a linear thienothiophene-containing dicarboxylate ligand, 3,4-dimethylthieno [2,3-b]-thiophene-2,5-dicar-boxylic acid (H2DMTDC). Single-crystal X-ray diffraction analysis reveals that Cd-MOF exhibits a 3D anionic framework with pcu α-Po topology, featuring rectangle and rhombus-shaped channels along b- and c- axis direction. Cd-MOF demonstrates selective adsorption of cationic dyes over anionic and neutral dyes. Additionally, Tb3+-loaded Cd-MOF serves as a fast-response fluorescence sensor for the sensitive detection of Fe3+ ions with a low limit of detection (8.90×10-7 M) through fluorescence quenching.

Enhancing the valorization of pulping black liquors in production effective aerogel–carbon nanostructure as adsorbents toward cationic and ionic dyes

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.

Optimization-driven modelling of hydrochar derived from fruit waste for adsorption performance evaluation using response surface methodology and machine learning

This study aims to explore the potential of integrating Design of Expert (DOE) with Machine Learning (ML) to optimize and predict the adsorption process of solid adsorbent The prediction and optimization of adsorption performance can be improvised using statistical analysis and advanced predictive tools, resulting in substantial cost and energy savings. Firstly, the Response Surface Methodology-Central Composite Design (RSM-CCD) model was used to design and optimize the experiments on the adsorption of cationic dye using biomass-hydro char. Secondly, Random Forest (RF) was used to train the experimental results of RSM-CCD. It is well-suited for small datasets, withstands noise, and effectively reduces overfitting to predict adsorption performance. RF model demonstrated excellent accuracy, achieving a removal efficacy of 97.4 % with a significant R2 value of 0.9981 compared to the RSM-CCD, which had a removal efficiency of 95.6 % and R2 0.9372. The physicochemical analysis also shows the novel hybrid hydrochar from fruit waste exhibits remarkable characteristics, including a higher content of carbon (78 %) and a surface area of 670 m2/g. In summary, RSM-CCD with ML provides precise optimization and predictions of the adsorption efficacy of the novel hydrochar. This has significant value for industrial applications in the field of material discovery.

Anisotropic Chitosan-nanocellulose/Zeolite imidazolate frameworks-8 aerogel for sustainable dye removal

Assembling microscopic metal–organic frameworks into macroscopic polymeric scaffolds to develop highly renewable materials has been a promising yet challenging area of research. Herein, chitosan (CS) blended with nano-cellulose (NC) was unidirectionally transformed into an aerogel with oriented macropores and then biomineralized with zeolite imidazolate frameworks-8 (ZIF-8) to form a hierarchical structured chitosan-nanocellulose/zeolite imidazolate frameworks-8 (CS-NC-ZIF-8) hybrid aerogel. Incorporating ZIF-8 significantly increases the versatility and mechanical strength with a Young’s modulus of 14.18 MPa of the CS-NC aerogel. The incorporation of ZIF-8 into the aerogel not only enhances its adsorption capacity for methylene blue, rhodamine B, acid fuchsin, and methyl orange, but also facilitates the generation of electrons from water that can be transferred to degrade > 90 % of malachite green within 90 min in each catalytic cycle, and this capability was maintained for at least 10 consecutive cycles. Remarkably, the hybrid aerogel was highly renewable after the adsorption of cationic dyes and catalytic removal of malachite green. With its facile production process, high removal efficiency, affordable and green nature, and excellent regeneration feasibility, the CS-NC-ZIF-8 aerogel stands as a promising solution for addressing challenges associated with dye-contaminated water treatment.

CTAB Surfactant Promotes Rapid, Efficient, and Simultaneous Removal of Cationic and Anionic Dyes through Adsorption on Glycerol/Citrate Polyester

The discharge of dye waste by industries has caused environmental impacts on water properties, aquatic species, and human life. The production of eco-friendly materials for dye removal from wastewater has gained increasing interest, particularly through adsorption, as it is an efficient method for removing pollutants. However, the selectivity and limited adsorption capacity of materials for simultaneously adsorbing cationic and anionic dyes make it challenging to address the prevailing dye effluent issue. In this work, a poly(glycerol citrate) polyester was prepared without a solvent, using microwave heating, and was combined with cetyltrimethylammonium bromide (CTAB) to modulate the simultaneous adsorption of cationic (Rhodamine B, RB) and anionic dyes (acid blue 113, AB and acid red 27, AR). The formation of the polyester was successfully confirmed by ATR-FTIR and the thermal properties were evaluated by TGA and DCS. In the presence of CTAB 5 mM, the material removes almost 100% of the dyes, reaching the kinetics equilibrium in 30 min following the Pseudo-second order model. Additionally, dye adsorption on the polyester in the presence of CTAB was described by the Freundlich isotherm model, indicating a heterogeneous polyester surface that promotes a multi-layer adsorption driven by electrostatic interaction and hydrogen bonds. The material showed an adsorption capacity of 73.7 ± 3.2, 82.1 ± 4.4, and 21.2 ± 0.6 mg/g for RB, AB, and AR, respectively. Our results provide evidence that the poly(glycerol citrate)/CTAB has a higher potential for application in wastewater treatment to remove both anionic and cationic dyes.

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

Hydrochar nanoparticles biosorbent (HCNPs), derived from orange peel was prepared via an in-situ hydrothermal carbonization method. The HCNPs were tested as an effective biosorbent for removing cationic MB (methylene blue) and anionic MO (methyl orange) dyes. The prepared HCNPs was characterized using FTIR, CHN/O, SEM-EDX, UV–visible, XRD, PZC-titration, BET, and XPS. The biosorbent exhibits a good specific surface-to-volume ratio (28.23 m2/g and 0.069 cc/g, respectively) and mesopores size (2.41 nm). UV–Vis data confirm the graphitic nature of the carbon structures. XPS analysis reveals a high enrichment of multiple oxygen functionalities (including C-OH, C = O, and –COO- groups) on the surface. The optimal initial pHs are 3.0 and 5.0–8.0 for removing MO and MB, respectively. Electrostatic attraction plays a substantial role, with other hydrophobic forces in dye removal and binding. Equilibrium is attained during 60/90 min, with half-biosorption-time (tHST) for MB and MO are 4.72 and 6.71 min, respectively. The highest biosorption capacities are 203.4 mg/g for MB and 113.3 mg/g for MO, closely correlated with physiochemical characteristics. Experimental data follows Langmuir isotherm and PSO kinetic models, indicating monolayer chemisorption on a homogeneous surface. The biosorption process for both dyes is exothermic and spontaneous. HCNPs show high durability over multiple biosorption/desorption cycles using HCl and NaOH (0.1 M) for MB and MO, respectively. These findings highlight the promising potential of HCNPs as efficient biosorbents for removing both anionic and cationic dyes.

Preparation and characterization of Ti3C2 Mxene through back propagation neural network-genetic algorithm combined with surface method response

Mxene's distinctive two-dimensional (2D) layered structure and special surface chemistry make it highly versatile for adsorption, sensors, elecatalysis, and energy storage. However, it has always been a challenge to obtain Mxene with excellent performance. In this study, the process of Ti3C2 Mxene preparation by etching Ti3AlC2 with hydrofluoric acid was optimized using the back-propagation neural network-genetic algorithm (BPNN-GA) and response surface methodology (RSM). Compared to RSM, BPNN-GA predicted better accuracy for preparation conditions with higher values for R2 (0.9830), MSE (2.6188), RMSE (1.6183), MAE (0.8504), and MAPE (0.0089 %). The BPNN-GA optimized etching values for HF concentration, time, and temperature were 8.81 %, 7.01 h, and 45.07 ℃, respectively. Under these conditions, the Ti3C2 Mxene prepared achieved 99.39 % removal efficiency of methylene blue (MB). The preparation was validated by XRD, SEM, TEM, XPS, Zeta, and FTIR analyses, indicating Ti3C2 Mxene to be a two-dimensional crystal structure with a multilayer arrangement and surface termination groups. Zeta measurements indicated that its surface carried negative charges across a wide pH range and its suitability for cationic dye adsorption. Using BPNN-GA provides valuable guidance and a novel strategy for material preparation.

New combined experimental and DFT studies for adsorption of sole Azo-dye or binary cationic dyes from aqueous solution

Textile-toxic synthetic dyes, which possess complex aromatic structures, are emitted into wastewater from various branches. To address this issue, the adsorption process was applied as an attractive method for the removal of dye contaminants from water in this article. An unprecedented integrated experimental study has been carried out, accompanied by theoretical simulations at the DFT-B3LYP/6-31G (d,P) level of theory to investigate how single Maxilon Blue GRL (MxB) dye or and its mixture with MG (Malachite Green) dyes interact with the adsorbent and compare the obtained results with the data obtained through experimentation. The full geometry optimization revealed the physical adsorption of dyes on the Al2O3 surface. Non-linear optical properties (NLO) results emphasized that the complex MG-Al2O3-MxB is a highly promising material in photo-applications, and the adsorbed binary system is energetically more favorable compared to the adsorbed sole dye system. The experimental results for (MxB) dye adsorption onto γ-Al2O3 affirmed that the optimum conditions to get more than 98% uptake were at dye concentration 100 ppm, pH 10, adsorbent content 0.05 g, and equilibrium time only 20 min. The kinetic and isothermal studies revealed that the adsorption accepted with the pseudo-second-order and Freundlich isotherm model, respectively. The removal efficiency of the mixture of MxB and MG dyes was the highest but did not change clearly with increasing the % of any of them. The details of the interaction mechanisms of the sole and binary dyes were proven.

Selective adsorption of cationic dyes by layered double hydroxide with assist algae (Spirulina platensis) to enrich functional groups

The present study involved the preparation, characterization, and evaluation of layered double hydroxide (LDH) with the assistance of the algae Spirulina platensis (NiAl-Sp and ZnAl-Sp). These materials were investigated for their potential for selective adsorption of cationic dyes, including rhodamine B, malachite green, and methylene blue. The adsorbents exhibit a significant level of selectivity in their capacity to adsorb malachite green in comparison to other cationic dyes. The next parameter of adsorption was evaluated in malachite green as the selective adsorption of cationic dyes. Based on the Langmuir isotherm model, the calculated maximum adsorption capacities of NiAl-Sp and ZnAl-Sp for malachite green were determined to be 478.190 mg/g (pH = 4, 50 °C for 30 min) and 123.457 mg/g (pH = 4, 30 °C for 30 min), respectively. The main processes of adsorption encompassed not only electrostatic interactions but also hydrogen bonding and π-π interactions involving the dye and the amino, hydroxyl, and carboxyl functional groups derived from Spirulina platensis. Spirulina platensis enhances the functional group of LDH. The findings of this study indicate that the NiAl-Sp and ZnAl-Sp composite demonstrated stability as a sorbent for the adsorption of malachite green. Furthermore, it was observed that this composite could be utilized for up to four adsorption cycles, but there was a noticeable decrease in its adsorption capability over time. The findings revealed that the synthesized composite adsorbents of NiAl-Sp and ZnAl-Sp exhibit high efficacy in the adsorption of malachite green from effluent.

Renewing Interest in Zeolites as Adsorbents for Capture of Cationic Dyes from Aqueous and Ethanolic Solutions: A Simulation-Based Insight into the Efficiency of Dye Adsorption in View of Wastewater Treatment and Valorization of Post-Sorption Materials.

The impact of solvents on the efficiency of cationic dye adsorption from a solution onto protonated Faujasite-type zeolite (FAU-Y) was investigated in the prospect of supporting potential applications in wastewater treatment or in the preparation of building blocks for optical devices. The adsorption isotherms were experimentally determined for methylene blue (MB) and auramine O (AO) from single-component solutions in water and in ethanol. The limiting dye uptake (saturation capacity) was evaluated for each adsorption system, and it decreased in the order of MB-water > AO-water > AO-ethanol > MB-ethanol. The mutual distances and orientations of the adsorbed dye species, and their interactions with the oxygen sites of the FAU-Y framework, with the solvent molecules, and among themselves were inferred from Monte Carlo simulations and subsequently utilized to rationalize the observed differences in the saturation capacity. The dye-solvent competition and the propensity of the dyes to form compact pi-stacked dimers were shown to play an important role in establishing a non-uniform distribution of the adsorbed species throughout the porous space. The two effects appeared particularly strong in the case of the MB-water system. The necessity of including solvent effects in modeling studies is emphasized.

Facile fabrication of lignin crosslinked hydrogel for cationic dye adsorption and antioxidant

Lignin, renowned for its abundance of hydroxyl groups, was utilized in three dimensions to fabricate a hydrogel matrix. In this study, the optimal conditions for the preparation of a lignin-crosslinked hydrogel and its potential for dye and antioxidant removal were investigated. The hydrogel was synthesized through a cross-linking reaction, with varying amounts of cross-linking agent (poly(ethylene glycol) diglycidyl ether) added to adjust for the lignin content. Chemical structure analysis of the lignin-crosslinked hydrogel was conducted using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy, confirming successful hydrogel formation. Additionally, thermal analysis revealed an increase in the maximum thermal decomposition temperature with increasing cross-linker content. The lignin cross-linked hydrogel demonstrated a significantly higher swelling ability at pH 7 compared to pH 3. The dye adsorption capacity of the lignin-crosslinked hydrogel, which was evaluated using crystal violet (CV), showed a maximum adsorption capacity of 106 mg∙g-1. The CV adsorption behavior followed Freundlich isotherms and pseudo-first-order kinetics. Moreover, the lignin-crosslinked hydrogel exhibited notable antioxidant activity, which was attributed to the phenolic hydroxyl groups of lignin macromolecules. Therefore, lignin-crosslinked hydrogels prepared using cross-linking agents have promising application potential in various fields.

Adsorption of cationic dyes and antibiotics from aqueous solution by dopamine-modified peanut husk

ABSTRACT Dopamine modified peanut husks (PH/DA), a novel adsorbent, were investigated to enhance the adsorption capacity of dyes (neutral red, NR and crystal violet, CV) and fluoroquinolone antibiotics (ofloxacin, OFLX and enoxacin, ENO). Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC) and Brunauer-Emmett-Teller (BET) method were used to characterize PH and PH/DA. The findings demonstrated that the physical and chemical properties of the peanut husks were changed after dopamine-modification. As for adsorption kinetics, NR adsorption properties were satisfactorily explained by the Elovich model, whereas CV adsorption processes suited to the pseudo-second order model. Both OFLX and ENO followed the pseudo-first order model. Isotherm data showed that CV and ENO conform to the Temkin model while NR and OFLX fitted better to the Langmuir model. The q max of NR, CV, OFLX and ENO by PH/DA were 52.37, 45.92, 46.57 and 58.40 mg/g at 290 K, respectively, according to Langmuir model. The adsorbent maintained an adsorption efficiency of above 70% even after three adsorption-desorption cycles. These findings proved that PH/DA’s successful development offers important insights into the production of sorbents for water treatment based on biomass.

Adsorption of cationic dyes in wastewater with magnetic κ-carrageenan nanoparticles

The application of innovative adsorbents with high adsorption capacity and easy recovery in wastewater treatment has always been of great concern. This study employed κ-carrageenan to enhance the dispersion of magnetic nanoparticles and improve their stability through Ca2+ and Na+ crosslinkinelg. XRD, FTIR, SEM and EDS revealed that the magnetic nanoparticles were coated with κ-carrageenan. The synthesized MΚC@Fe3O4MNPs exhibited a stable structure and multiple adsorption sites, which was beneficial for the treatment of cationic dyes in wastewater. The absorption results indicated that abundant active sites on the surface of the adsorbent efficiently adsorbed the three cationic dyes. Through optimization experiments, the MΚC@Fe3O4MNPs demonstrated maximum adsorption capacities of 729.9 mg/g, 184.1 mg/g, and 311.0 mg/g for methylene blue, malachite green, and safranin T, respectively. The adsorbent could maintain excellent adsorption efficiency even after 5 cycles of use. The adsorption mechanisms for the three cationic dyes included electrostatic interactions, n-π interactions, and hydrogen bonding. Therefore, the MΚC@Fe3O4MNPs showed highly efficient adsorption and separation of cationic dyes and are suitable candidates for dye wastewater treatment.

Novel porous hydrogel beads based on amidoxime modified polymer of intrinsic microporosity for efficient cationic dye removal

Due to the high surface area and facile functionalized or modified groups of polymers of intrinsic microporosity, and the hydrophilicity of sodium alginate (SA), a simple strategy was proposed for preparing porous composite hydrogel beads with excellent cationic dye adsorption capacity and selectivity. The porous composite hydrogel beads were prepared by introducing the amidoxime modified polymers of intrinsic microporosity (AOPIM-1) into SA polymer solution and then dropping the mixture into CaCl2 aqueous solution at low temperature for crosslinking. The prepared porous SA/AOPIM-1 hydrogel beads performed excellent adsorption capacity on Rhodamine B (RhB) from aqueous solution and the Langmuir model was suitable for describing the adsorption behavior of RhB on porous SA/AOPIM-1 hydrogel beads. It is surprising that the maximum theoretical adsorption capacity obtained by fitting the Langmuir model was up to 1648.3 mg·g−1. More importantly, porous SA/AOPIM-1 hydrogel beads showed outstanding selective adsorption capacity for cationic dyes in the mixed anionic and cationic dyes solution. Besides, the adsorption capacity of porous SA/AOPIM-1 hydrogel beads could maintain above 80 % of the initial adsorption capacity after 10 adsorption/desorption cycles. The above results indicate that porous SA/AOPIM-1 hydrogel beads can be used as a promising adsorbent with for effective removal of dyes from wastewater treatment.