Congo Red Adsorption Research Articles

Synthesis, characterization and application of tetragonal BaTiO3-δ in adsorption and photocatalysis of Congo Red

The synthesis by a simple approach of the deficient Barium Titanate BaTiO3-δ (BTO) crystallizing in a perovskite structure is reported along with the physicochemical properties. Thermal analysis (TG/DSC) was performed to elucidate the synthesis process. The X-ray diffraction (XRD), BET analysis, scanning electron microscopy (SEM-EDS) and electrochemistry were investigated. The catalyst revealed a single phase with a tetragonal symmetry obtained by treatment at 650 °C. The direct band gap (3.34 eV), obtained from diffuse reflectance spectroscopy (DRS), is assigned to the charge transfer O2-: 2p-Ti4+: 3d. The electrical characterization indicated a non-degenerate conductivity due to oxygen vacancies with an activation energy of 0.33 eV. The capacitance measurements indicated n-type behavior with a flat band potential (Efb) of − 0.43 V and a carrier concentration (ND) of 3.90 ×1018 cm−3. The photocatalytic process was elucidated by the electrical impedance spectroscopy (EIS). The performance of BTO was assessed by a combination of the adsorption of Congo Red (CR) followed by its degradation under UV light. The photodegradation kinetic was well fitted by a pseudo-first-order model with an abatement of 50% and 91% under UV and solar lights respectively. Different scavengers were used to evaluate the reaction mechanism and the radicals O2•- are the main reactive species of the CR oxidation. Four regeneration cycles demonstrated the catalyst stability. A degradation mechanism was established based on the scavengers effect.

Facile fabrication of bioinspired hierarchical porous MOFs for selective adsorption of Congo red and Malachite green from vegetables and fruits juices

The dye pollution in environmental water and food caused by industrial production and illegal addition is a serious problem worldwide, which endangers ecosystem, food safety and human health. To effectively overcome these challenges, a magnetic bioinspired hierarchical porous MOFs (BHP-MOFs) based on ZIF-8, Fe3O4 and three-dimensional graphene was successfully prepared for selective adsorption of Congo red (CR) and Malachite green (MG) from aqueous solutions. The surface morphology, physicochemical structure and composition of BHP-MOFs were characterized by SEM, TEM, FT-IR, XRD, Zeta potential, TGA and VSM analysis. The prepared BHP-MOFs exhibited a large specific surface area (225.522 m2/g), high pore volume (0.248 cm 3/g) and superparamagnetism, which made it an efficient adsorbent for fast adsorption of CR and MG. The adsorption kinetics studies showed that the adsorption mechanism of CR and MG followed the pseudo-second model and the adsorption process fitted well to Langmuir isotherm equation. Thermodynamic experiments have shown that the adsorption process is spontaneous and endothermic. The maximum adsorption capacities of CR and MG were 176.06 and 448.43 mg/g, respectively. Under the optimum conditions, BHP-MOFs were successfully used as magnetic adsorbents for the removal of CR and MG in environmental water and fruit juices, with removal efficiency ranged from 97.09% to 76.00%. The reusability of the BHP-MOFs was repeated with seven cycles and removal efficiency remained at 63.01% and 82.20% for CR and MG, respectively. It is proved that BHP-MOFs composite has excellent adsorption capacity for dyes and has a wide application prospect in practical applications.

Biochar Derived from Rice Husk as Effective Adsorbent for the Removal Congo Red and Procion Red MX-5B Dyes

Biochar derived from rice husk was successfully prepared with the pyrolysis method. X-Ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Thermogravimetry analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis confirmed biochar. The results indicate that biochar is amorphous carbon. Functional groups on biochar include -OH, C-H, C-O, C=C, and C-O. The surface area of biochar of 72.252 m2/g with a pore size of 3.334 nm which is classified as mesoporous material. Biochar was used as an adsorbent on the congo red (CR) and procion red MX-5B (PR) dyes with adsorption capacities of 42.918 and 84.034 mg/g, respectively. The equilibrium adsorption occurred at 120 minutes. The adsorption isotherm and kinetics both followed the Langmuir isotherm and Pseudo Second Order (PSO), respectively. CR and PR adsorption process using biochar by physisorption and chemisorption with interactions that occur include hydrogen interactions, physical interactions, π-π interactions, and electrostatic interactions.

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.

Removal of congo red from water by adsorption onto activated carbon derived from waste black cardamom peels and machine learning modeling

The present work utilizes waste black cardamom (BC) as an inexpensive and environmentally friendly adsorbent for sequestering the Congo Red (CR) dye from aqueous media for the first time. Following a carbonization process at 600 °C, chemical activation with KOH was carried out for waste BC and subsequent black cardamom activated carbon (BCAC) was employed as an absorbent for CR eradication. The effect of experimental factors, including pH, adsorption time, dose and CR initial concentration, was investigated. 96.21 % of CR dye removal was achieved at pH 6 for 100 mg/L of CR concentration having 0.1 g dose at 30 °C. Maximum Langmuir adsorption capacity of BCAC was found to be 69.93 mg/g at 30 °C. The kinetic analyses showed that the CR adsorption over BCAC behaved in accordance with a pseudo-second order kinetic model as high R2 values (0.997–1) were obtained. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) demonstrated that the CR adsorption over BCAC was feasible, spontaneous and exothermic in nature. In addition, the state-of-the-art machine learning (ML) approaches namely, support vector regression (SVR) and artificial neural network (ANN) were employed for modeling the BCAC adsorbent for CR removal. The statistical analysis revealed high prediction performance of SVR model with AARE value of 0.0491 and RMSE value of 0.4635 while the corresponding values for the ANN model were 0.0781 and 0.5395, respectively. Furthermore, the plots between experimental CR data and ML forecasted data were closely matched (R2 > 0.99). Thus, it can be concluded that BC, an agro waste could be utilized for CR removal and that the adoption of ML approaches can benefit users by providing them with a tool to enhance the design and performance of wastewater treatment operations.

Nanovertenergie: Bactericidal polymer nanocomposite beads for carcinogenic dye removal from aqueous solution

This project stresses the current problems in the industrial revolution and the increasing demand for new products due to the population explosion. In the race for industrialization, the production unlimited byproducts and discharge of harmful gases in the atmosphere, discharging harmful sewage into fresh water resources and dumping of harmful waste in the soil. Polymer nanocomposites enable an eco-friendly environment that is dignified to be far for efficient than the current strategies, and likewise, anti-bacterial, and water treatment holds the future.Here, the design and development of polymer nanocomposite based on polyvinyl alcohol cross-linked with melamine-formaldehyde doped with Cu nanoparticles. The electrostatic interaction between polymer matrixes increases the chemical stability after doping Cu nanoparticles. The chemical stability order of polymer nanocomposites was confirmed by contact angle (58-90o) in water> NaOH> HCl. The polymer nanocomposite films were analyzed for the Congo red (CR) dye adsorption using Batch adsorption methods. Three parameters were used to determine dye adsorption by contact time, pH, and the dye concentration of CR dye. The dye adsorption analysis reveals that CR dye adsorption increases in polymer nanocomposite films from (C1-C5). CR dye adsorption increase with respect to contact upto 80% mg L−1, but the adsorption percentage decreases (68-13%) as the pH (4-10) increases values. The anti-bacterial results reveal that the inhibition against B. subtilis 736 and S. aureus is 40 mm and 35 mm, respectively, after the encapsulation of Cu nanoparticles. The present study launched a positive effort to design and develop an eco-friendly, very efficient, and safe synthesis of nanomaterials with unparalleled properties like waste water treatment discharge from textile industries for cleaner production, bactericidal, and packing industries.

Congo red dye adsorption onto cationic amino-modified walnut shell: Characterization, RSM optimization, isotherms, kinetics, and mechanism studies

Congo red (CR) dye contamination in aquatic ecosystems often threatens human and aquatic health. This work synthesized a chemically modified, cationic amino-modified walnut shell (CMWS) adsorbent to treat CR dye-contaminated water. Central composite design (CCD) using standard response surface methodology design was performed to understand optimal conditions for removing dye with minimal experimentation. Maximum removal efficiency (94.12%) was achieved through CMWS than the raw walnut shell (RWS). Hydrogen bonding, pore filling, and electrostatic attractions effectively removed CR dye using CMWS. To understand cost-effectiveness and practical applicability, an adsorption-desorption analysis of CMWS was performed up to the third cycle with a removal efficiency of 82.18% with biomass loss of 26%. This study recommends CMWS as a potential adsorbent for CR dye removal and is worth investigating in the future.

Effective adsorption of polycyclic aromatic Congo red dye by modified garlic peel

To evaluate the competence of garlic peel (GP) as a low-cost bio-adsorbent, GP was chemically modified with sodium carbonate (Na2CO3) and hydrochloric acid, and used to adsorb Congo red (CR). The surface morphology, chemical characterization and structural information of the adsorbents were studied by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The impact of different adsorption settings on the removal effectiveness of CR by sodium carbonate-treated garlic peel (Na2CO3-GP) was also studied. The optimum conditions for effective adsorption of CR by Na2CO3-GP is found to be pH of 7, 90 minutes of equilibrium contact duration, 50 mg/L of initial CR concentration, 200 revolutions per minute of stirring (RPM), 0.10 g/mL of adsorbent dosage, and temperature of 298 K. As indicated by Langmuir isotherm, monolayer adsorption occurs at a maximum capacity of 52.6 mg/g for Na2CO3-GP. Adsorption kinetic studies suggest chemisorption, the process follows a pseudo-second-order model and thermodynamics of adsorption specifies that the process is spontaneous. The results explicitly show that Na2CO3-GP can be an effective bio-adsorbent for the removal of CR.

Potassium citrate-derived porous carbon with high CO2 capture and Congo red adsorption performance

The objective is to achieve the goal of carbon neutrality, controlling CO2 emissions is a primary problem to be solved in the current environmental protection field. Eliminating the environmental pollution of dyes in industrial wastewater is also an urgent problem to be solved in the field of environmental protection. The adsorption technique is an effective way to deal with these two issues. Developing high-efficiency adsorbents is an essential work in the adsorption field. In this work, a simple carbonization method has been developed to prepare porous carbon. The morphology and structure of the prepared porous carbon were investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and surface area measurement. By studying the influence of preparation conditions on the structure and properties of the prepared carbon materials, it was found that the carbon materials prepared at 900 ℃ (PCMCA-900) exhibited a high specific surface area of 1476 m2 g−1 and a high total pore volume of 0.951 cm3 g−1. The PCMCA-900 showed the highest CO2 uptake of 7.67 mmol g−1 at 0 ºC and the adsorption capacity of PCMCA-900 decreased by less than 5% after 10 times recycling. Moreover, when PCMCA-900 was used as an adsorbent to remove Congo red in water, an adsorption capacity of 652.3 mg g−1 was achieved. Therefore, potassium citrate-derived porous carbon is a desirable candidate for excellent CO2 adsorption and Congo red in industrial wastewater.

Ionic liquid-water interfacial synthesis of ionic liquid incorporated metal-organic frameworks with enhanced adsorption properties

In the present work, a two-phase system composed of a hydrophobic ionic liquid (IL) containing copper ions (Cu(II)) and water containing organic linkers was constructed and the Cu-based metal-organic framework (Cu-MOF) formed at the IL-water interfaces at room temperature. The IL 1,3-bis(carboxymethyl)imidazolium chloride ([BCMIM]Cl) was also introduced in the MOF structures via using it as co-linker. The adsorption capacity of the synthesized Cu-MOF and [BCMIM]Cl modified Cu-MOFs was evaluated using the organic dye Congo red (CR) as target compound. Experimental results suggested that the incorporation of [BCMIM]Cl in the Cu-MOF remarkably improved the CR adsorption capacity due to the strong π-π and electrostatic interactions between the cation of [BCMIM]Cl and CR. The adsorption behavior of CR on [BCMIM]Cl modified Cu-MOF fitted well with pseudo-second-order kinetics and Freundlich isotherm model. Thermodynamic analysis suggested the adsorption of CR on [BCMIM]Cl modified Cu-MOF was a physical adsorption process. Finally, compared with reported adsorbents, the [BCMIM]Cl modified Cu-MOF exhibited higher CR adsorption capacity, indicating that it was a promising adsorbent for the removal of organic dyes from water.

Sustainable Cu2(OH)2CO3/g-C3N4/cellulose acetate-derived porous composite membrane for Congo red and tetracycline removal with photocatalytic self-cleaning properties under natural solar irradiation

A highly efficient and sustainable Cu/CN@CA composite membrane was synthesized for the removal of typical dyes and antibiotics by incorporating a Cu2(OH)2CO3/g-C3N4 heterojunction (Cu/CN) onto a cellulose acetate (CA) membrane. The 0.2Cu/CN@CA membrane with optimized Cu/CN doping achieved superior Congo red (CR) and tetracycline (TC) adsorption capacities of 250.8 and 48.43 mg/g, respectively. Notably, the exhausted 0.2Cu/CN@CA after adsorption saturation could be effectively self-cleaned under natural solar irradiation. Consecutive adsorption-photocatalytic experiments revealed its fine stability and recyclability. Mechanistic exploration based on experimental analysis and DFT (Density Function Theory) calculations revealed that cellulose acetate accommodates the charge transfer interactions between g-C3N4 and Cu2(OH)2CO3, wherein many photogenerated electrons were generated and migrated from g-C3N4 to Cu2(OH)2CO3. This type II heterojunction transfer pathway induced the strong oxidizability of the 0.2Cu/CN@CA membrane with plenty of active species for the photocatalytic degradation of the adsorbed CR and TC contaminants under solar light irritation. This study provided a novel sustainable membrane-based adsorbent for the enhanced dye and antibiotic contaminant remediation of aquatic environments.

Removal of the Pigment Congo Red from Synthetic Wastewater with a Novel and Inexpensive Adsorbent Generated from Powdered Foeniculum Vulgare Seeds

In this research, powdered Foeniculum vulgare seed (FVSP) was treated separately with H2C2O4, ZnCl2, and a mixture of ZnCl2-CuS. The characteristics of the treated and untreated FVSP samples, as well as their abilities to eliminate Congo red (CR) from solutions, were investigated. The influences of the empirical circumstances on CR adsorption by the ideal adsorbent were studied. The thermodynamic, isothermal, and dynamic constants of this adsorption were also inspected. The ideal adsorbent was found to be the FVSP sample treated with a ZnCl2-CuS mixture, which eliminated 96.80% of the CR dye. The empirical outcomes proved that this adsorption was significantly affected by the empirical circumstances, and the second-order dynamic model as well as the Langmuir isotherm model fit the empirical data better than the first-order model and the Freundlich model. The values of Ea (15.3 kJ/mol) and ∆Ho (32.767 kJ/mol ≤ ∆Ho ≤ 35.495 kJ/mol) evidence that CR anions were endothermally adsorbed on Zn/Cu-FVSP via the ionic exchange mechanism. The superior Qmax values (434.78, 625.00, 833.33 mg/g), along with the cheapness and stability of the adsorbent used in this work, are evidence to confirm that this adsorbent will receive special interest in the field of contaminated water purification.

Cd2+ and Zn2+ Complexes with 2,4,6-Tri(2-pyridyl)-s-Triazine and Terephthalate for Rapid, High-Capacity Adsorption of Congo Red.

Three crystal complexes were designed and synthesised through the solvothermal method, with Cu2+ , Zn2+ , and Cd2+ ions as the metal centres and 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) and terephthalate (BDC2- ) as the ligands. Their compositions were determined to be Cd(TPTZ)Cl2 (Cd-MOF), {[Zn(TPTZ)(BDC)] ⋅ 3H2 O}n (Zn-MOF), and Cu2 (PCA)2 (BDC)(H2 O)2 (Cu-MOF) (PCA- =2-pyridinium amide), respectively. Cd-MOF can adsorb 90 % of Congo red (CR) in 10 s at room temperature and atmospheric pressure, and CR removal was complete at 20 s over a wide pH range. The adsorption capacity for CR reached 1440 mg g-1 in 5 min. Selective adsorption was demonstrated in mixed dyes. The adsorption kinetic data agree well with the pseudo-second-order kinetic model. The Temkin model was successfully used to evaluate the adsorption isotherms of CR on Cd-MOF at room temperature, suggesting that adsorption occurs through a hybrid of monolayer and multilayer mechanisms.

Nitrogen-rich hierarchical porous polyphosphazene for rapid and efficient adsorption of anionic contaminants: Kinetics, isotherm, thermodynamics and mechanism

The rapid and highly-efficient uptake of waterbody contaminants by polymer-based adsorbent is still a challenge. Herein, a new nitrogen-rich hierarchical porous polymer (PCPM) was synthesized via a self-catalyzed polycondensation between hexachlorocyclotriphosphazene and melamine. The PCPM possessed hierarchical pore architecture with specific surface area of 321.1 m2/g and pore size distribution from 1.3 to 63.0 nm. Owing to the remarkable porous texture and nitrogen-rich active sites with high electron density, PCPM exhibited a high adsorption capacity of 187.5, 336.2, and 320.4 mg g−1 for Cr (VI), Congo red (CR), and diclofenac sodium (DCF), respectively. Moreover, the adsorption rate of these contaminants onto PCPM was very fast, reaching 90 % of adsorption equilibrium capacity for Cr (VI), CR and DCF within the first 7 min, 45 min and 30 min, respectively. Adsorption data revealed that the adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm model. The removal process was spontaneous, exothermic for Cr (VI) and endothermic for CR and DCF. FT-IR and XPS analysis demonstrated that electrostatic interaction and hydrogen bonding contributed to the adsorption of CR and DCF onto PCPM, while the removal mechanism of Cr (VI) by PCPM included redox reaction and chelation besides the above two interactions.

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.

Extremely Fast and Efficient Removal of Congo Red Using Cationic-Incorporated Hydroxyapatite Nanoparticles (HAp: X (X = Fe, Ni, Zn, Co, and Ag))

Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. The pristine and cation ion-doped HAp adsorbents were coprecipitated and subjected to hydrothermal and ultrasound treatments and subsequent microwave drying. The dopant ions significantly engineered the crystallite size, crystallinity, particle size (decreased 38–77%), shape (a rod to sphere modification by the incorporation of Ag+, Ni2+, and Co2+ ions), and colloidal stability (CS) of the adsorbent. These modifications aided in the rapid removal of the CR dye (98%) within one minute, and the CR adsorption rate was found to be significantly higher (93–99%) compared to previously reported rates. Furthermore, the kinetic, Langmuir, Freundlich, and DKR isotherms and thermodynamic results confirmed that the CR adsorption on the HAp was due to the strong chemical adsorption process. The order of the maximum CR adsorption capacity was Fe-HAp > HAp > Ag-HAp > Co-HAp > Zn-HAp. Whereas the CR regeneration efficiency was Fe-HAp (92%) > Ag-HAp (42%) > Ni-HAp (30%), with the other adsorbents exhibiting a poor recycling efficiency (1–16%). These results reveal Fe-HAp as a potential adsorbent for removing CR without the formation of byproducts.

Adsorption efficacy of functionalized Cu-BDC MOFs tethered 2-mercaptobenzimidazole analogue: A comparative study

A novel metal-organic framework [MOFs], and 2-[benzo [d]thiazol-2-ylthio)-3-hydroxy acrylaldehyde-Cu-benzene dicarboxylic acid was synthesized by solvothermal method and characterized using p-XRD, FSEM-EDX, TGA, BET, FTIR. The tethered organic linker, 2-[benzo [d]thiazol-2-ylthio)-3-hydroxyacrylaldehyde was commonly known as 2-mercaptobenimidazole analogue [2-MBIA]. Analysis of BET disclosed that addition of 2-MBIA to Cu-benzene dicarboxylic acid [Cu-BDC], reduced the crystallite size from 70.0 nm to 65.90 nm, surface area from 17.95 to 17.02 m2 g-1 and enhances the pore size from 5.84 nm with 0.027 cm3 g-1 pore volume to 8.74 nm with 0.361 cm3 g-1 pore volume. Batch experiments were conducted to optimize pH, adsorbent dosage, and, Congo red (CR) concentration. The adsorption percentage of CR on the novel MOFs was 54%. Adsorption kinetic studies revealed that the uptake adsorption capacity at equilibrium was 184.7 mg/g from pseudo-first-order kinetics which gave a good fit with the experimental data. Intraparticle diffusion model explained the process of the adsorption mechanism: diffusion from the bulk solution onto the porous surface of the adsorbent. Freundlich and Sips models were the best fit models of the several non-linear isotherm models. Temkin isotherm suggested the adsorption of CR on MOFs was of an exothermic nature.

Insight into the adsorption of magnetic microspheres with large mesopores: Tailoring mesoporous structure and ethylenediamine functionalization for ultrahigh Congo red removal

In this study, ethylenediamine (EDA)-functionalized magnetic microspheres with large mesopores (MMMs) were fabricated and explored for the use as highly efficient adsorbents to remove Congo red (CR). The size of mesoporous channels and loading of EDA functional groups were adjusted to optimize the CR adsorption performance of resulting adsorbents. It was found that higher specific surface area (SBET) was favorable for greater CR adsorption, while increasing EDA loading resulted in CR adsorption capacity with a change of first increasing and then declining. The optimal adsorbent FSN-2 with 1.71 wt% N content possessed an ultrahigh maximum CR adsorption capacity of 1662 mg/g, ascribed to its high SBET of 530.91 m2/g and large average pore size of 8.78 nm. The experimental data were fitted best by using the Langmuir model and pseudo-second-order model, suggesting that the adsorption feature be monolayer and chemosorption. The thermodynamic parameters, i.e.ΔG, ΔH and ΔS, were also estimated, indicating the CR adsorption onto FSN-2 was spontaneous and endothermic in nature. High adsorption capacities were recorded in a wide pH range of 5.0 – 9.0, while the addition of Cl-, SO42- and NO3– had negligible effect on its CR removal. Moreover, FSN-2 showed good reusability and high stability in adsorption–desorption cycles, as well as excellent CR removal capacity in simulated actual wastewater. The adsorption mechanisms of CR onto FSN-2 mainly involved electrostatic attraction and hydrogen bonding. This work provides a new insight into the fabrication of highly efficient magnetic adsorbents by optimizing the porous structure and functional group loading for potential practical application in wastewater treatment.

Defective multi-element hydroxides nanosheets for rapid removal of anionic organic dyes from water and oxygen evolution reaction

Water pollution by dyes is one of the biggest environmental problems. Adsorption technology has been widely used in wastewater treatment. In this work, high-entropy concept is used to design surface defective hydroxides realizing the rapid removal of dyes from water. Multi-element hydroxides (MEHs) containing three (CoMnNi, MEH-Ternary), four (CoMnNiZn, MEH-Quaternary), and five (CoMnNiZnFe, MEH-Quinary) metal elements are successfully synthesized through a polyol process. These as-synthesized MEHs are composed of nanosheets with a brucite-like structure. Along with the increase in compositional complexity (i.e., configurational entropy), the thickness of the nanosheets in these MEHs decreases, while the degree of surface defects increase. These surface defects are probably the active sites for anionic dyes adsorption, suggesting rapid adsorption kinetics with shortened diffusion path length. For MEH-Quinary in 0.2 mM Congo red (CR) and MEH-Ternary in 0.4 mM methyl orange (MO) aqueous solutions, respectively, high removal efficiency > 99.0% is achieved in the first 30 s. Their pseudo-second-order rate constants are two orders of magnitude higher than that of activated carbon and hydrotalcite. MEH-Quinary has maximum CR and MO adsorption quantity of 546.4 and 404.9 mg g-1, respectively, by Langmuir model. The MEH-Quinary is also a potential electrocatalyst for oxygen evolution reaction.

Sandwich-like construction of a new aminated chitosan Schiff base for efficient removal of Congo red

Herein, a novel sandwich-like α-ketoglutaric acid Schiff base-aminated chitosan composite (α-kGl-AmCsSB) was fabricated by reacting α-ketoglutaric acid and aminated chitosan. The as-fabricated α-kGl-AmCsSB was inspected by diversified characterization tools to determine its morphology, surface charge, and chemical composition as well as define the linkage pathway between α-kGl and AmCs. The SEM images demonstrated a spongy network of AmCs with interconnected pores structure which turned to a quite rough surface due to the linkage of α-kGl to the free amine groups of AmCs. Notably, the XPS and FTIR spectra suggested the linkage of α-kGl to the amine group of AmCs. The experimental results implied the superior adsorption efficiency of Congo red (CR) onto α-kGl-AmCsSB since the maximum adsorption capacity (qmax) reached 434.78 mg/g at 25 °C and pH 3. Based on kinetics data, the adsorption of CR on α-kGl-AmCsSB followed pseudo-second-order model. Furthermore, D-R model infers that the CR adsorption onto α-kGl-AmCsSB occurred via physical interactions since the E value < 8 kJ/mol. The recyclability test was implemented for five cycles with R% > 72%. More importantly, the adsorption mechanism of CR onto α-kGl-AmCsSB was proposed and discussed. Ultimately, the novel sandwich-like α-kGl-AmCsSB exhibited advanced adsorption performance toward CR along with excellent reusability. Based on these results, we recommend more modifications on α-kGl-AmCsSB for exploiting its remarkable advantages and applying it on a large scale.