Congo Red Adsorption Process Research Articles

Dual cross-linked magnetic gelatin/carboxymethyl cellulose cryogels for enhanced Congo red adsorption: Experimental studies and machine learning modelling

To achieve highly efficient and environmentally degradable adsorbents for Congo red (CR) removal, we synthesized a dual-network nanocomposite cryogel composed of gelatin/carboxymethyl cellulose, loaded with Fe3O4 nanoparticles. Gelatin and sodium carboxymethylcellulose were cross-linked using transglutaminase and calcium chloride, respectively. The cross-linking process enhanced the thermal stability of the composite cryogels. The CR adsorption process exhibited a better fit to the pseudo-second-order model and Langmuir model, with maximum adsorption capacity of 698.19 mg/g at pH of 7, temperature of 318 K, and initial CR concentration of 500 mg/L. Thermodynamic results indicated that the CR adsorption process was both spontaneous and endothermic. The performance of machine learning model showed that the Extreme Gradient Boosting model had the highest test determination coefficient (R2 = 0.9862) and the lowest root mean square error (RMSE = 10.3901 mg/g) among the 6 models. Feature importance analysis using SHapley Additive exPlanations (SHAP) revealed that the initial concentration had the greatest influence on the model’s prediction of adsorption capacity. Density functional theory calculations indicated that there were active sites on the CR molecule that can undergo electrostatic interactions with the adsorbent. Thus, the synthesized cryogels demonstrate promising potential as adsorbents for dye removal from wastewater.

α-Fe2O3 nanorods on CoFe-LDH@MX via interfacial interactions for Congo red removal: Experimental and mechanistic studies

Developing a 3D material to support α-Fe2O3 nanorods to improve their adsorption performance for Congo Red (CR) is a major challenge. Herein, a novel 3D composite adsorbent was designed, where 2D material Ti3C2 MX and CoFe-LDH stacked on top of each other as the support material of α-Fe2O3 nanorods (α-Fe2O3@LDH@MX). The specific surface area of the α-Fe2O3@LDH@MX was increased by 2 times (101.28 m2/g) than original CoFe-LDH@MX, thus more favorable for capturing CR (698.25 mg/g). The results of kinetic studies demonstrate that the effective 3D composite structure enables unhindered movement of CR within the α-Fe2O3@LDH@MX. The Langmuir model can accurately describe the adsorption process of CR on the α-Fe2O3@LDH@MX, which means that the process belongs to monomolecular layer chemisorption. Molecular dynamics simulations revealed that the α-Fe2O3 interface primarily interacts with oxygen within the -SO3 group, achieving an adsorption energy up to Einteraction= −20,375.89 kcal/mol. The results of XPS analysis further revealed that interaction between Fe and O achieved the removal of CR. In this paper, the enhancement of α-Fe2O3 adsorption performance has been successfully achieved through innovative structural design. This significantly advances its potential applications and offers new insights for future material design.

Room temperature synthesis of copper-modified ZIF-8/Chitosan for enhanced adsorptive removal of congo red

The synthesis of Cu(II)-doped ZIF-8/Chitosan by means of the one-pot method at room temperature was successfully carried out. The synthesized materials exhibit enhanced adsorption properties for the removal of Congo red (CR) dye. The structural and morphological properties of Cu(II)-doped ZIF-8/Chitosan were characterized. Cu(II)-doped ZIF-8/Chitosan achieved the most optimal CR removal efficiency and CR adsorption capacity (153.85 mg/g) due to its higher specific surface area (522.776 m2/g) compared to ZIF-8/Chitosan (514.882 m2/g). Electrostatic attraction, hydrogen bonding, and π-π interaction are the main interactions for the higher adsorption performance. The CR adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. The results of the thermodynamic adsorption indicated that the process of CR adsorption by Cu-doped ZIF-8/Chitosan was an endothermic reaction. The experimental results indicate that the Cu(II)-doped ZIF-8/Chitosan material has the potential to be used in wastewater treatment for the removal of anionic dyes.

Cetyltrimethylammonium Bromide-Modified Laponite@Diatomite Composites for Enhanced Adsorption Performance of Organic Pollutants.

This work aims to enhance the adsorption performance of Laponite @diatomite for organic pollutants by modifying it with cetyltrimethylammonium bromide (CTAB). The microstructure and morphology of the CTAB-modified Laponite @diatomite material were characterized using SEM, XRD, FTIR, BET, and TG. Furthermore, the influences of key parameters, containing pH, adsorbent dosage, reaction time, and reaction temperature, on the adsorption process were investigated. The kinetics, thermodynamics, and isotherm models of the adsorption process were analyzed. Finally, potential adsorption mechanisms were given based on the characterization. The research findings indicate that CTAB-La@D exhibits good adsorption performance toward Congo red (CR) over a broad pH range. The maximum adsorption capacity of CR was 451.1 mg/g under the optimum conditions (dosage = 10 mg, contact time = 240 min, initial CR concentration = 100 mg/L, temperature = 25 °C, and pH = 7). The adsorption process conformed to the pseudo-second-order kinetic model, and the adsorption isotherms indicated that the adsorption process of CR was more in line with the Langmuir model, and it was physical adsorption. Thermodynamic analysis illustrates that the adsorption process is exothermic and spontaneous. Additionally, the mechanisms of electrostatic adsorption and hydrophobic effect adsorption of CR were investigated through XPS and FTIR analysis. This work provides an effective pathway for designing high-performance adsorbents for the removal of organic dye, and the synthesized materials hold great capability for practical utilization in the treatment of wastewater.

Effective removal of Congo red from aqueous solutions using ethylenediamine-modified wheat straw as adsorbent

In this study, ethylenediamine (EDA)-modified wheat straw (EMWS) was prepared and used as an efficient adsorbent for removing Congo red (CR) from aqueous solutions. Adsorption of CR by EMWS was examined through static adsorption experiments to determine the effect of contact time, initial pH values, particle size of the adsorbent, solution concentration, and temperature. As pH ranged from 4.0 to 10.0, CR adsorption by the EMWS remained considerably elevated. The equilibrium adsorption capacity was determined to be 97.92 mg·g−1 for a CR concentration of 400 mg·L−1, pH of 4.0, temperature of 318 K, and EMWS dose of 2 g·L−1, which was found to be comparable to other materials used for CR adsorption. Following that, optimal conditions were used to conduct isothermal, kinetic, and thermodynamic studies. In the adsorption process of CR, the Freundlich isotherm model and the pseudo-second-order (PSO) kinetics provided the best fit, indicating the presence of both physisorption and chemisorption mechanisms. Electrostatic attraction and hydrogen bonding were primarily responsible for CR adsorption onto the EMWS. Based on thermodynamic investigations, the adsorption of CR on EMWS is determined to be spontaneous (ΔG < 0) and endothermic (ΔH = 60.83 kJ·mol−1), while also exhibiting an increase in disorder (ΔS = 289.9 J·mol−1·K−1). The elution was carried out using 0.20 M HCl, followed by washing the EMWS with water, resulting in no loss of functionality. This study suggests that EMWS possesses the potential to serve as a feasible and efficient adsorbent for CR removal in wastewater.

Superior Adsorption Efficiency of MIL‐101 (Cr) and Nano‐MIL‐101 (Cr) in Anionic and Cationic Dye Removal from Aqueous Solution

AbstractMetal‐organic frameworks (MOFs) as adsorbent have received considerable attention due to their remarkably high porosity, adjustable pore shape/size, and surface functionality. This study focusses on the adsorption performance and mechanism of two different typological and structural MOFs as superior adsorbents for the efficient removal of anionic and cationic dyes in an aqueous solution. MIL‐101(Cr) and nano‐MIL‐101(Cr) were successfully synthesized by the hydrothermal method using two different protocols and both materials were confirmed by XRD, TG‐DTA‐DTG, FTIR and SEM analyses. The adsorption kinetics and isotherms were determined from the experimental data obtained under optimal conditions. The adsorption kinetics suggests the adsorption process of Congo Red (CR) and Thioflavin T (TFT) onto MIL‐101 (Cr) and nano‐MIL‐101(Cr) conformed to the pseudo‐second‐order kinetic model. The Langmuir isotherm agrees well with the experimental data, and the adsorption capacities for MIL‐101 (Cr) and nano‐MIL‐101 (Cr) were found to be 986 mg g−1 (CR) and 863 mg g−1 (TFT), 1004 mg g−1 (TFT), respectively. The adsorption mechanism is to be related to π–π stacking, hydrogen bonding, pore filling, electrostatic interaction, and partial chemical interaction. This study demonstrates that MIL‐101 (Cr) and nano‐MIL‐101 (Cr) are promising reusable adsorbents with high adsorption capacity for removing dyes from aqueous solutions.

Photogenic MnO2/Ag metal nanocomposites and their dye adsorbing activities

Manganese dioxide/silver (MnO2/Ag) nanoparticles were fabricated by using KMnO4-NaBH4 redox reaction at room temperature. The optical and structural properties of MnO2/Ag were determined using UV–visible and Fourier transform infrared spectroscopies. The morphology was established with scanning and transmission electron microcopies, and X-ray diffraction. MnO2/Ag showed excellent adsorbing activity to the removal of Congo red. The various kinetic models were used to determine the rate of dye removal. Congo red adsorption onto MnO2Ag proceeds through the pseudo-second-order kinetic model. Langmuir adsorption capacity (Q0max = 97.1 mg/g), and sorption intensity (n = 1.6) were estimated with Langmuir and Freundlich adsorption isotherm models for 250 mg/L Congo red. Elovich model suggest the adsorption of Congo red with the MnO2Ag proceeds through the film diffusion. The positive values of enthalpy changes (ΔH0), entropy changes (ΔS0), and negative Gibbs free energy changes (ΔG0) showed that the Congo red adsorption process was endothermic, spontaneous, and chemisorption process followed with physical mechanism. The results showed that the removal efficiency decreases from 98% to 89% after the six consecutive experiments.

Removal of Congo red dye from aqueous environment by zinc terephthalate metal organic framework decorated on silver nanoparticles-loaded biochar: Mechanistic insights of adsorption

In this study, zinc terephthalate-metal-organic framework decorated on the surface of poultry manure-derived biochar (ZT-MOF@Ag@C) was successfully fabricated and employed as nano-adsorbent material for Congo Red (CR)-treated aqueous solution. The physical characteristics of the developed ZT-MOF@Ag@C adsorbent were analyzed by the Brunauer–Emmett–Teller (BET) theory, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) Scanning Electron Microscopy equipped with Energy-Dispersive X-Ray Spectroscopy (SEM/EDS), and X-Ray Photoelectron Spectrometer (XPS). The characterization analysis revealed that biochar modification with ZT-MOF and AgNPs greatly enhanced the surface area. The mesopores ZT-MOF@Ag@C BET surface area of 1028 m2/g showed a maximum adsorption capacity of 416.6 mg/g. The Langmuir isotherm and pseudo-second order kinetic models best described the adsorption process of CR onto ZT-MOF@Ag@C. The thermodynamic studies revealed that the adsorption of CR on the ZT-MOF@Ag@C was spontaneous and exothermic. The as-fabricated ZT-MOF@Ag@C was observed to be stable after sixth adsorption-desorption cycles. ZT-MOF@Ag@C composite exhibited excellent potential for the treatment of CR dye from the aqueous solution. The point of zero charge, BET, XRD, XPS, SEM, and FTIR analyses confirmed that the adsorption of CR onto ZT-MOF@Ag@C nanocomposite is majorly dominated by the following mechanisms: π-π interaction, pore adsorption, electrostatic interaction, and hydrogen bonding. The biochar-derived adsorbent's performance was significantly improved through modification, thereby suggesting an effective strategy for boosting the sorbent activity.

Efficient adsorption of Congo red by micro/nano MIL-88A (Fe, Al, Fe-Al)/chitosan composite sponge: Preparation, characterization, and adsorption mechanism

MIL-88A crystals with three different metal ligands (Fe, Al, FeAl) were prepared by hydrothermal method for the first time. The three materials' crystal structure and surface morphology are different, leading to different adsorption properties of Congo red (CR). The maximum adsorption capacities of MIL-88A (Fe), MIL-88A (FeAl), and MIL-88A (Al) are 607.7 mg · g−1, 536.4 mg · g−1, and 512.1 mg · g−1 respectively. In addition, MIL-88A was combined with chitosan (CS) respectively, and MIL-88A/CS composite sponge was prepared by the freeze-drying method, which not only solved the defect that MIL-88A powder was difficult to recover but also further improved the removal ability of CR by the adsorbent. The maximum adsorption capacities of MIL-88A (FeAl)/CS, MIL-88A (Fe)/CS, MIL-88A (Al)/CS, and CS are 1312 mg · g−1, 1056 mg · g−1, 996.7 mg · g−1, and 769.6 mg · g−1, respectively. The structure and physicochemical properties of the materials were analyzed by SEM, FTIR, XRD, TGA, BET, and Zeta. The adsorption process of CR follows pseudo-second-order kinetics and Langmuir, Sips isotherm model. Combined with thermodynamic parameters, the adsorption behavior was described as endothermic monomolecular chemical adsorption. The removal of CR is attributed to electrostatic interactions, hydrogen bonding, metal coordination effects, and size-matching effects.

Preparation of a novel CSM@ZIF-67 composite microsphere to facilitate Congo red adsorption from dyeing wastewater

ABSTRACT Chitosan (CS) is commonly used as an adsorbent for wastewater treatment because of its low cost, strong adsorption properties, and high availability of raw materials required for its production. However, CS exhibits limited adaptability to pH, poor mechanical properties, and high swelling in aqueous media; these limitations restrict its widespread use. To address these issues, herein, zeolitic imidazolate framework-67 (ZIF-67) is loaded onto crosslinked CS microspheres (CSM) to prepare CSM@ZIF-67, a composite adsorbent. Next, the CSM@ZIF-67 is applied to the treatment of Congo red (CR) dye, which is typically present in printing and dyeing wastewater. The results demonstrate that the in situ synthesis of metal-organic frameworks (MOFs) on CSM improve the dispersion of MOFs and preserve the morphology of the MOFs. The adsorption equilibrium of CSM@ZIF-67 is reached within 150 min, and its adsorption capacity is as high as 538.4 mg/g at a pH of 9 and temperature of 25 °C. The CR adsorption process is consistent with the pseudo-second-order kinetic and Langmuir isotherm models, thus revealing that chemisorption is the primary rate-limiting step, and the pollutants are adsorbed on the adsorbent surface in a monolayer. Experiments on material cycling and regeneration performance reveal that the removal efficiency of CSM@ZIF-67 remains above 90%, even after five rounds of adsorption. CSM@ZIF-67 has abundant functional groups and adsorption sites and can efficiently remove CR through mutual interactions between the metal coordination effect, π–π conjugation, hydrogen bonding, and electrostatic interactions.

A novel route for the facile synthesis of NH2-MIL-53(Fe) and its highly efficient and selective adsorption of congo red

Metal-organic frameworks (MOFs) have shown attractive advantages in adsorbing dyes from wastewater. However, their complex synthesis processes and poor stability have limited their applications. Herein, we proposed a novel two-step route to prepare NH2-MIL-53(Fe) at room temperature and investigated its dye adsorption performance. The prepared NH2-MIL-53(Fe) displayed high water stability in the pH range of 3–11. Moreover, NH2-MIL-53(Fe) showed a significantly higher adsorption capacity and faster adsorption rate towards congo red (CR) than the other selected dyes, with more than 99 % of CR being removed by NH2-MIL-53(Fe) within 20 min. The maximum adsorption capacity of NH2-MIL-53(Fe) for CR was 1877 mg·g−1. Besides, the removal efficiency of CR could maintain higher than 80 % within the tested pH range (3 to 11), and removal efficiency was consistently higher than 95 % at different NaCl concentrations (0 to 0.4 M). The dynamic CR adsorption process matched the pseudo-second-order kinetic model and fitted well using the Langmuir model, suggesting that the adsorption of CR onto NH2-MIL-53(Fe) was a monomolecular-layer chemical adsorption process. More importantly, NH2-MIL-53(Fe) showed high removal efficiency and good reusability towards CR in both synthetic and model wastewater. Mechanistic studies suggested that the removal of CR was attributed to the synergistic effects of the π-π stacking interactions, hydrogen bonds and electrostatic interactions between CR and NH2-MIL-53(Fe). Overall, the present study provides a novel strategy for the facile synthesis of NH2-MIL-53(Fe), highlights the excellent adsorption performance and reusability towards CR and underlies the adsorption mechanisms involved.

Different Adsorption Behaviors and Mechanisms of Anionic Azo Dyes on Polydopamine–Polyethyleneimine Modified Thermoplastic Polyurethane Nanofiber Membranes

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater.

Preparation of Hydrochar from Salacca zalacca Peels by Hydrothermal Carbonization: Study of Adsorption on Congo Red Dyes and Regeneration Ability

Hydrochar of Salacca zalacca peels (HC-SP) is prepared by hydrothermal carbonization treatment of Salacca zalacca peels (SP) obtained from local fruits at Palembang, South Sumatera, Indonesia, with the resulting yield weight reaching 90%. Materials are characterized using the XRD diffraction, FTIR spectrum, and SEM-EDX. The XRD pattern shows the characteristics of the formation of amorphous compounds. The FTIR spectrum confirms the presence of functional groups O-H, C-H, C=C, and C-O. Data of SEM-EDX show that materials have heterogeneous morphologies, form aggregates, and in HC-SP materials there is an increase in carbon content from the initial material. The capacity of SP in the congo red (CR) adsorption process is 33.003 mg/g and increases to 133.333 mg/g in HC-SP. The maximum dye adsorbed was achieved at pH 4. The adsorption kinetics followed PSO with the equilibrium adsorption occurring at 90 minutes, and the adsorption isotherm followed the Langmuir isotherm with the value of R2 closer to the value of 1. A positive 4H value indicated that the adsorption is an endothermic process. In contrast, an 4S value suggested that the degree of irregularity in the adsorption process is small in large concentrations. Based on data regeneration ability, materials of SP and HC-SP can be used in the three cycles regeneration process of the CR adsorption process. The adsorption process of CR occurs physically and chemically based on enthalpy values and FT-IR data after being adsorbed with CR.

Combustion process for magnetic copper–cobalt ferrite and its Congo red adsorption property

A rapid combustion process was introduced for the preparation of magnetic copper–cobalt ferrite, which was characterized using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Brunauer–Emmett–Teller techniques (BET). The prepared magnetic copper–cobalt ferrite showed a large specific surface area (104.6 cm2 g−1) and nanoscale particle size (55.4 nm), with a saturation magnetization of 19.6 Am2 kg−1. The nanoparticles were used to adsorb and remove Congo red (CR) from dyestuff wastewater, and the adsorption mechanism was revealed. Compared with the pseudo-first-order kinetic model and intraparticle diffusion kinetic model, the pseudo-second-order kinetic model was better at describing the CR adsorption process on the Cu0.5Co0.5Fe2O4 nanoparticles, while the Temkin isotherm best fitted the CR adherence on the Cu0.5Co0.5Fe2O4 nanoparticles. All data suggested that the adsorption of CR on the Cu0.5Co0.5Fe2O4 nanoparticles followed the mono-multilayer hybrid chemisorption mechanism. In addition, as the pH increased from 2 to 10, the adsorption capacity of the Cu0.5Co0.5Fe2O4 nanoparticles for CR decreased, indicating that an acidic environment was beneficial for the adsorption of CR on the Cu0.5Co0.5Fe2O4 nanoparticles. When recycling the Cu0.5Co0.5Fe2O4 nanoparticles after adsorbing CR, the relative adsorption rate was still 62.5% of the initial adsorption capacity after five cycles, revealing the reusability and promising applicability of Cu0.5Co0.5Fe2O4 nanoparticles in sewage treatment.

Removal of the Anionic Dye Congo Red from an Aqueous Solution Using a Crosslinked Poly(vinyl alcohol)-ZnO-Vitamin M Nanocomposite Film: A Study of the Recent Concerns about Nonlinear and Linear Forms of Isotherms and Kinetics.

This paper deals with the preparation, characterization, and application of a crosslinked poly(vinyl alcohol)/ZnO-vitamin M (PVA/ZnO-VM) nanocomposite film for the removal of Congo red (CR) from an aqueous solution. The characterization of a crosslinked PVA/ZnO-VM nanocomposite film showed that the structure became more regular and also the surface morphology appeared smooth in comparison with pure PVA. The obtained data from Brunauer-Emmett-Teller (BET) proved the mesoporous structure for this nanocomposite film. Several effective factors were examined for the adsorption ability of the nanocomposite film, including solution pH (2-10), sorbent amount (0.02-0.08 g), contact time (3-240 min), initial concentration of the adsorbate (30-300 mg·L-1), and temperature (318-358 K). The optimal conditions are as follows: pH = 10, adsorbent amount = 0.06 g, and C0 = 200 mg·L-1. The removal efficiency of the nanocomposite film was 92% after 4 h at the ambient temperature. To interpret the adsorption process, nonlinear and linear forms of kinetic and isotherm models were considered. The obtained data followed nonlinear pseudo-second-order and linear Langmuir isotherm models, which indicated the monolayer formation of CR over the crosslinked PVA/ZnO-VM nanocomposite film with the maximum adsorption capacity of about 56.49 mg·g-1. Also, the adsorption process of CR by the crosslinked PVA/ZnO-VM nanocomposite film is a spontaneous and exothermic reaction.

Effect of Fomes fomentarius Cultivation Conditions on Its Adsorption Performance for Anionic and Cationic Dyes.

Lab-cultivated mycelia of Fomes fomentarius (FF), grown on a solid lignocellulose medium (FF-SM) and a liquid glucose medium (FF-LM), and naturally grown fruiting bodies (FF-FB) were studied as biosorbents for the removal of organic dyes methylene blue and Congo red (CR). Both the chemical and microstructural differences were revealed using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, zeta potential analysis, and scanning electron microscopy, illuminating the superiority of FF-LM and FF-SM over FF-FB in dye adsorption. The adsorption process of CR on FF-LM and FF-SM is best described by the Redlich–Peterson model with β constants close to 1, that is, approaching the monolayer Langmuir model, which reach maximum adsorption capacities of 48.8 and 13.4 mg g–1, respectively, in neutral solutions. Adsorption kinetics follow the pseudo-second-order model where chemisorption is the rate-controlling step. While the desorption efficiencies were low, adsorption performances were preserved and even enhanced under simulated dye effluent conditions. The results suggest that F. fomentarius can be considered an attractive biosorbent in industrial wastewater treatment and that its cultivation conditions can be specifically tailored to tune its cell wall composition and adsorption performance.

Synthesis of MgNiCo LDH hollow structure derived from ZIF-67 as superb adsorbent for Congo red

Adsorption materials with large specific surface area and porous structures exert a beneficial impact on improving the adsorption performance. In this work, MgNiCo LDH hollow structure (MNC HS) is fabricated through a simple one-step solvothermal method using ZIF-67 as the sacrificial template. Electron microscopy shows that the MNC HS retains the dodecahedral shape of ZIF-67. The as-prepared sample exhibits efficient adsorption for Congo red (CR) in water, which is due to the hierarchical structure and large specific surface area that provides more adsorption sites and electrostatic interaction. The CR adsorption process fits the pseudo-second-order model better by kinetics simulation; while Langmuir model is more accurate than Freundlich model in describing the adsorption isotherms of CR. The maximum adsorption capacity calculated by the Langmuir model can reach 1194.7 mg g−1, which is much higher than that of the sample MgNiCo LDH (MNC) synthesized by conventional methods. The cycle tests also show that the as-prepared adsorbent has good stability and recycling ability.

Direct grafting of cellulose nanocrystals with poly(ionic liquids) via Gamma-ray irradiation and their utilization for adsorptive removal of CR

In this work, a simple but effective method based on Gamma-ray initiated polymerization was reported for the first time through direct irradiation of CNCs and ionic liquid monomer to obtain poly (ionic liquids) functionalized CNCs (IL@CNCs). The adsorptive removal of Congo red (CR) from aqueous solution by IL@CNCs was also examined and the influence of contact time, pH values, initial concentrations and temperature on adsorption behavior was investigated in detail. Under the same adsorption conditions, the adsorption capacity was increased from 59.72 mg/g (CNCs) to 195.83 mg/g (IL@CNCs). The results of the adsorption isotherm and adsorption kinetics showed that the experimental data were more suitable to be described by the Freundlich isotherm adsorption model and the pseudo-second-order model. The adsorption process of CR on the surface of the adsorbent was endothermic and spontaneous. When the aqueous solution was acidic, it was more conducive to the adsorption of CR. At 100% breakthrough, the value of adsorption capacity is 199.95 mg/g and the value of partition coefficient is 9.64. Moreover, the adsorption capacity is expected to be further improved through adjustment of polymerization parameters and this method can also be used for preparation other poly (ionic liquids) modified composites.

Preparation and Adsorption Properties of Soybean Dreg/Hydrocalumite Composites.

The application of biomass-based composites in the field of adsorption has attracted extensive attention. Herein, soybean dreg/hydrocalumite composites were prepared by in situ self-assembly from soybean dregs and applied to the adsorption of Congo Red (CR). The composites were characterized by scanning electron microscopy, X-ray diffraction, Fourier infrared spectroscopy, and N2 physical adsorption–desorption. The results showed that the adsorption property of soybean dregs/hydrocalumite for CR was better than that of soybean dregs or hydrocalumite. Effects of preparation and adsorption conditions on the adsorption of CR by soybean dregs/hydrocalumite were also investigated. The removal rate of soybean dregs/hydrocalumite (30%BD-LDH) prepared under the optimized conditions reached 97.4% with a 486.8 mg·g–1 adsorption capacity. Also, the adsorption capacity of 30%BD-LDH was about 2.4 times and 3.0 times that of hydrocalumite and soybean dregs, respectively. In addition, the adsorption process of CR by 30%BD-LDH was more in line with the pseudo-second-order kinetic and Langmuir isothermal models.

Calcined ZnAl-LDH trapping performance in alginate beads for adsorption of Congo Red dye

ABSTRACT In this study, we report the adsorption process of Congo Red (CR) dye by calcined Layered Double Hydroxide (ZAC) at 550°C. The urea hydrolysis method was applied to produce highly crystalline Zn2Al-LDH. Samples characterisation was carried out by X-ray diffraction (XRD), Thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR). The results show that the adsorption of CR on calcined ZnAl-LDH was accompanied by the reconstruction of the layered structure. The ZAC showed higher adsorption efficiency versus other adsorbent under investigation and optimum conditions of contact time, adsorbent dose, pH and temperature were found to be 50 min, 0.02 g, 7 and 318 K, respectively. Isotherm studies show that the Langmuir isotherm model was appropriate to describe the CR adsorption data compared with Freundlich and Temkin isotherm models, with a higher correlation coefficient (R2 > 0.99) and maximum adsorption capacity of 406.5 mg/g. The thermodynamic parameters revealed that the adsorption process was spontaneous, endothermic, and governed by chemisorption. To further facilitate the recovery process in CR adsorption, we test the feasibility of applying ZnAl-LDH and its calcined product at 550°C entrapped in alginate beads. Experimental results indicate that alginate-coated ZAC beads, which exhibited remarkable adsorption performance, were more stable and require less effort to pull and separate than the alginate/ZnAl-LDH composite beads.