Congo Red Adsorption Capacity Research Articles

Highly efficient adsorption of congo red and methyl orange dyes using mesoporous α-Mn2O3 nanoparticles synthesized with Pyracantha angustofolia fruit extract

Due to the many applications of manganese oxides in water treatment, this research aimed to synthesize α-Mn2O3 nanoparticles through a green method and investigate the dye adsorption capacity of them. The α-Mn2O3 nanoparticles were successfully synthesized using KMnO4 and aqueous extract of Pyracantha angustofolia fruits under hydrothermal conditions and calcination. The products were identified using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM) analyses. The adsorption capacity of methyl orange (MO) and Congo red (CR) dyes were evaluated at different concentrations (25, 50, and 75 ppm) using α-Mn2O3 nanoparticles. Results revealed the spherical and porous structure of α-Mn2O3 nanoparticles with a specific surface area of 21.7 m2.g-1. Dye removal significantly increased with pH decrement. The adsorption capacity for MO and CR was 73.07 and 70.70 mg.g−1, respectively. The adsorption data of both dyes followed a pseudo-second-order kinetic model. The best fitted models for MO and CR adsorption were the Langmuir isotherm and the Dubinin–Radushkevich, respectively. In addition, a possible adsorption mechanism was proposed for both dyes. The findings showed that α-Mn2O3 nanoparticles are very efficient adsorbents for removing anionic dyes.

Magnetic bio-composite based on zirconium and chitosan modified activated carbon from peanut husk with enhanced antibacterial and adsorptive potential for alizarin red and congo red in wastewater

Creating new adsorbents is crucial for removing contaminants from water due to increased industrialization, which has worsened water pollution in recent years. In this study, a magnetic biocomposite, Zirconium (Zr)-doped chitosan (CS)-coated iron oxide nanoparticles (Fe3O4-NPs)-peanut husk (PH)-based activated carbon (AC) (Zr-CS/Fe3O4-NPs@PH-AC), was synthesized for efficient removal of alizarin red (AR) and congo red (CR) dyes, alongside antibacterial applications. Characterization via scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis revealed micropores and mesopores development due to chemical activation of PH biomaterial and Fe3O4-NPs addition. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) identified functional groups and structural properties. Vibrating sample magnetometry (VSM) analyzed magnetic properties. Optimal conditions for AR/CR removal were determined, including Zr-CS/Fe3O4-NPs@PH-AC dose, dye dose, contact time, and temperature, achieving maximum removal percentages. Experimentally determined maximum adsorption capacities for AR and CR were 374.3 and 154.1 mg·g−1, respectively. Cytotoxicity studies affirmed the eco-friendly and non-toxic nature of the adsorbent by exhibiting the reduction in the cell viability from 100 % to 88.68 % from the 0 to 200 μg·L−1 respectively. Additionally, the biocomposite exhibited significant antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to magnetic NPs. The material in this study shows extreme compatibility for numerous applications.

Lignin-derived porous carbon with interconnected pores for bulky dye adsorption in fixed-bed systems

The porous structure of adsorbents is an important factor of their adsorption performance, especially in fixed-bed systems. In this study, we fabricated lignin-derived porous carbon (LPC-Mg) with interconnected pores, which exhibited low resistance for the transport of contaminants in water. The maximum adsorption capacity of LPC-Mg toward Rhodamine B (RhB) and Congo red (CR) was 403.2 and 735.3 mg·g−1 in the batch adsorption mode and 330.5 and 718.6 mg·g−1 in the column adsorption mode. Microporous, hierarchical porous, and commercial activated carbon were used as carbonaceous adsorbents for comparison. The RhB and CR adsorption capacity of LPC-Mg was 1.8–26.6 and 4.0–33.6 times those of other carbonaceous adsorbents at the breakthrough points in fixed-bed systems, respectively. This study developed an effective strategy toward the improvement in the adsorption efficiency of carbon-based adsorbents in fixed-bed systems.

Nanofiber films reinforced with biomass extracts and their high efficiency in adsorbing dyes

In this study, polyacrylonitrile (PAN) was used as precursor and calcium Lignesulfonate (CLS) as additive to prepare composite films by electrospinning technology for the adsorption of methylene blue (MB) and Congo red (CR) dyes. The composite films were characterized by Brunauer-Emmett-Taylor analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). The effects of pH value, temperature, concentration and reaction time on adsorption efficiency were investigated. When the content of CLS is 20 wt%, the composite membrane has excellent adsorption performance, and the maximum adsorption capacity of MB and CR are 48 and 23 mg/g.

Citric acid steam-assisted decomposition method for the synthesis of meso-macroporous magnesium oxide with rich oxygen defects: Efficient removal and convenient recovery property of Congo red and Ni(II)

The removal of Congo red (CR) and heavy metal ion nickel (Ni(II)) from wastewater is a critical concern for safeguarding the aquatic environment and promoting sustainable development. Herein, a novel citric acid steam-assisted decomposition method is applied to form meso-macroporous magnesium oxide (MgO) with rich oxygen defects. As the gelation process of xerogel precursor could be significantly promoted by the steam-assisted process with citric acid solution as steam source, the morphology structure of MgO changes into loose aggregates with sharp edges and is covered by a layer of MgO nanoparticles. The synthesized MgO, with a high surface area (103.60 m2 g−1), meso-macroporous structure and abundant oxygen defects, exhibits super adsorption capacities for CR (7109.85 mg g−1) and Ni(II) (1405.88 mg g−1). The MgO (0.4 g L−1) could completely remove CR (200 mg L−1) in 30 min, while 10 min for Ni(II) (200 mg L−1) adsorption. The adsorption mechanism of MgO for CR and Ni(II), including electrostatic interaction, oxygen vacancy capture, hydrogen bonding and ion exchange, is effectively enhanced due to the appearance of meso-macroporous structure and oxide defects, such as 5-coordinated oxygen anion (O5C2−) for terrace, 4-coordinated oxygen anion (O4C2−) for edge and 3-coordinated oxygen anion (O3C2−) for corner. The easy calcination is applied to recycle MgO after CR adsorption and the CR removal efficiencies are above 98 % after five cycles. Meanwhile, a nickel chelator (Na2EDTA) and calcination are used to regenerate the MgO after Ni(II) adsorption and the adsorbent shows an insignificant removal efficiency loss after three cycles. The meso-macroporous MgO with rich oxygen defects has the characteristics of high adsorption speed, high adsorption capacity and convenient recovery property, and is expected to become an ideal material for the rapid treatment of high concentration wastewater.

Pore structure evolution and adsorption behaviors of porous poly (vinyl alcohol) hydrogel prepared using Na2SO4 and CaCO3 as porogens

AbstractIn this work, porous poly (vinyl alcohol) (PVA) hydrogels with different pore sizes were fabricated using inorganic non‐metallic porogens by an environmentally friendly method, providing a potential solution for the field of wastewater treatment. PVA hydrogels have gained much attention in the field of wastewater treatment due to their excellent adsorption performance and porous network structure. However, the employment of inorganic non‐metallic salts as porogens for PVA hydrogels has received limited attention so far. In this study, porous PVA hydrogels were prepared by freeze‐thawing and freeze‐drying with sodium sulfate (Na2SO4) and calcium carbonate (CaCO3) as porogens. PVA‐Na exhibited denser network structure with the concentration of Na2SO4 solution increased, and the tensile stress was enhanced by about 45 times. Meanwhile, the tensile stress of PVA‐Ca was improved significantly from 0.06 to 1.67 MPa, and the network structure became looser after adding CaCO3. Moreover, a comprehensive investigation was conducted on the adsorption performance of porous PVA hydrogel for Congo red (CR). Finally, five adsorption models were fitted to investigate the adsorption mechanism of porous PVA hydrogels, in which the maximum adsorption capacity of CR by PVA‐Na‐0.5 was predicted to be 215 mg/g by the Langmuir isothermal model fitting.Highlights The structure of PVA hydrogels was adjusted by Na2SO4 and CaCO3, respectively. The tensile stress of PVA‐Na with dense network structure increased 45 times. Compared to PVA‐FD, swelling equilibrium time of PVA‐Na reduced from 24 to 6 h. Equilibrium swelling rate of PVA‐Ca declined by half in comparison to PVA‐FD. Langmuir isothermal model predicted qmax of 215 mg/g for CR by PVA‐Na‐0.5.

Graphene oxide intercalated Alk-MXene adsorbents for efficient removal of Malachite green and Congo red from aqueous solutions

Currently, adsorbents with high adsorption performance for eliminating pollutants from discharged wastewater have received many researchers’ attention. To this aim, a novel AMXGO absorbent was fabricated by intercalating graphene oxide (GO) into alkalized MXene (Alk-MXene) layer which exhibited high efficacy for the removal of cationic Malachite Green (MG) and anionic Congo Red (CR). Analysis of FTIR, XRD, SEM and TG presented that AMXGO absorbent have a typical three-dimensional layer by layer structure and abundant oxygen-containing groups and its thermal stability was remarkably improved. BET results elucidated that AMXGO1 adsorbent has larger specific surface area and pore volume (16.686 m2 g−1, 0.04733 cm3 g−1) as compared to Alk-MXene (4.729 m2 g−1, 0.02522 cm3 g−1). A dependence of adsorption performance on mass ratio between Alk-MXene and GO, initial dye concentration, contact time, temperature and pH was revealed. Maximum adsorption capacity of MG (1111.6 mg/g) and CR (1133.7 mg/g) were particularly found for AMXGO1 absorbent with a mass ratio of 3:1 and its removal for both dyes were higher than 92%. The adsorption process of AMXGO1 adsorbent for both MG and CR complies with pseudo-second-order kinetic model and Freundlich isotherm model. In addition, adsorption mechanism was explored that synergism effects as electrostatic attraction, π-π conjugates, intercalation adsorption and pore filling were the main driving force for the high adsorption performance of dye. Therefore, AMXGO adsorbent has a potential application prospect in the purification of dye wastewater.

Preparation of metal organic framework by strategy of ligand premodification coupling with dual ligands and adsorption behaviors for organic dyes

The method of ligand premodification coupling with dual ligands to introduce several functional groups can regulate the pore structure of the porous materials to meet different demands and to maintain the integrity of the framework. Amino groups was introduced into organic ligand by reacting with polyethyleneimine and then it was applied as one of the ligands to prepare porous materials. A series of porous materials were synthesized through varying the additional amount of modified ligand and characterized by several techniques such as BET, FTIR, XRD, XPS, SEM and EDS. The prepared materials were then used to remove organic dyes methyl orange (MO), methylene blue (MB) and Congo red (CR) from aqueous solution. The porous materials exhibited larger adsorption capacities and fast adsorption rate for MO and MB as certain modified ligand introduced. Due to steric hindrance of introduced amino chain, the adsorption capacities for CR decreased. The results of adsorption kinetics and adsorption isotherm studies showed that the adsorption process was more in line with pseudo-second kinetic model and Langmuir isotherm. The adsorption selectivity of the material for MB compared to MO could be controlled by altering the amount of modified ligand The prepared porous materials can be used as fascinating adsorbents for removal of dyes from aqueous solution in a wide pH range, and it was attractive and useful from practical viewpoint.

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.

The Suitability of Fe3O4/Graphene Oxide Nanocomposite for Adsorptive Removal of Methylene Blue and Congo Red

In this study, Fe3O4/GO nanocomposite was synthesized by hydrothermal method and tested for its efficiency in removing methylene blue (MB) and congo red (CR) from water. The synthesized nanocomposite was characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The optimal values for MB and CR removal were determined to be pH 6.0, an adsorbent weight of 50.0 mg, and a contact time of 10 min. The adsorption isotherms of the contaminants on the nanocomposite were analyzed using the Freundlich model, indicating a heterogeneous distribution of active sites on the adsorbent surface. The highest adsorption capacity of MB and CR is 135.1 and 285.7 mg.g-1, respectively. Moreover, Fe3O4/GO nanocomposite recycled five cycles with proper adsorption capacity. Overall, the Fe3O4/GO nanocomposite holds great promise for efficient and sustainable water treatment, providing safe and clean water globally.

Fast and highly efficient removal of organic dyes from aqueous solution by attapulgite modified with different amino groups

Type of functional groups of the adsorbent is crucial for an adsorption process which significantly affects adsorption rate and adsorption capacity for certain adsorbate. In this study, attapulgite (APT) was modified with different amino groups and the adsorbents obtained were used to remove toxic organic dyes from aqueous solution. Five adsorption kinetic models and three adsorption isotherm models were employed to estimate the adsorption behaviors for organic dyes methylene blue (MB) and Congo red (CR) onto the adsorbents. The results showed that adsorption behaviors of the adsorbents for MB were different from those for CR, and among the four adsorbents, APT exhibited the highest adsorption capacity for MB (307.27 mg/g) while APT modified with hyperbranched polyamide-amine (APT-(3)) had the highest adsorption capacity for CR (1277.33 mg/g) according to adsorption kinetic data, indicating the type of amino groups did have a significant impact on adsorption. It can be concluded that APT-(3) exhibited certain adsorption selectivity for CR. In addition, the adsorption of MB and CR was a fast and highly efficient process. The results indicated that the APT samples used can remove and enrich cationic and anionic dyes and can be potentially used in the wastewater treatment.

The effective removal of Congo red dye via chitosan-layered double hydroxide composite and the deep insight into mechanism

In this study, the chitosan microspheres (CSM) were successfully prepared by emulsion crosslinking method, and layered double hydroxides (LDH) was grown in situ on the surface of the chitosan microspheres to prepare chitosan-layered double hydroxide composites (CS@LDH). The properties of CS@LDH composites were characterized by means of SEM, XRD, FT-IR and EDS. The removal effect of the composite on Congo red (CR) dye was studied. The batch adsorption experiments indicated that chitosan intercalated LDH obtained better adsorption capacity for CR than CSM and LDH, the equilibrium adsorption capacity of CS@LDH, CSM and LDH was 745.8, 285.5 and 226.4mg g−1, respectively. The results of adsorption dynamics and isotherm models showed that the adsorption process was more consistent with Elovich nonlinear model and Temkin isotherm model. The characterization of CS@LDH after adsorption of CR implied that the affinity between CS@LDH and CR mainly involved electrostatic interaction was revealed via Independent Gradient Model based on the Hirshfeld partition of molecular density (IGMH) and Hirshfeld surface analysis. In addition, molecular dynamics (MD) simulations were conducted to analyze the influence of CS@LDH on the structure and properties of CR. The results indicate a significant adsorption effect of CS@LDH on CR.

Synthesis of glutamic acid-based coordination polymer for dye removal from aqueous solution

In this work, a cost-effective and eco-friendly coordination polymer (Zr-CP) was synthesized through the combination of natural amino acids as ligands with Zr4+ metal cation under aqueous conditions at room temperature and used for the treatment of dyeing wastewater. The results showed that Zr-CP exhibited a high adsorption potential for Congo red (CR) in various simulated dyeing effluents. It possesses a theoretical adsorption capacity for CR up to 381.68 mg/g at room temperature 25 ℃ in pH 7, probably due to the abundance of primary amino functional groups in its chemical structure. The thermodynamic analysis indicates that the use of Zr-CP as an adsorbent in the wastewater purification process endothermic and spontaneous in nature. Among the tested isotherms, the Langmuir model was found to best fit the equilibrium data, with a coefficient R2 value of 0.98. Besides, the adsorption behavior of this bio-based coordination polymer for Congo red was found to adhere to the pseudo-first-order kinetic equation with higher correlation coefficient R2 of 0.98. Moreover, Zr-CP showed outstanding cycle performance and sustained a high dye removal efficiency even after five reuses. These results indicate that Zr-CP, a biologically derived coordination polymer, offers the advantages of affordability and efficiency, making it a promising adsorbent for the removal of organic pollutants from printing and dyeing effluents.

Room-temperature aqueous synthesis of MOF-808(Zr) for selective adsorption of dye mixtures

ZrIV-based metal–organic frameworks (MOFs) featuring distinguished water stability, large surface area, and intriguing functionalities have immense potential for practical usage. However, conventional MOF synthesis approaches generally require high reaction temperatures and organic solvents to initiate and template the nucleation and growth, hindering sustainable and cost-effective manufacturing and application of Zr-based MOFs. In this study, a scalable, room-temperature and aqueous synthesis of MOF-808—a Zr-MOF extensively explored as an adsorbent in both academic and industrial sectors—was reported. A rational use of water/formic acid (FA) as a green co-solvent enabled the formation of Zr6-cluster in an aqueous phase, thereby facilitating subsequent coordination with H3BTC to yield well-crystallized MOF-808. The effects of the water/FA volume ratio, the total solvent volume, and reaction time on the physicochemical properties of MOF-808 were studied. The optimized synthesis conditions (FA/water = 2.7:8.1, and reaction time = 24 h) resulted in the synthesis of MOF-808 with good hydrophilicity, excellent stability, high surface area, and weak positive charges. Moreover, this synthesis approach was successfully upscaled, yielding 11.5 g of MOF-808 at a magnification factor of 48. Notably, MOF-808-V10.8 exhibited an impressive adsorption capacity for Congo Red (ca. 1500 mg/g) and demonstrated selective fractionation of dye mixtures, suggesting their potential application in dye wastewater treatment. This methodology is expected to provide guidance for aqueous and scalable fabrication of Zr-MOFs towards water-related environmental applications.

Preparation and characterization of γ-AlOOH/Fe3O4 for the highly effective removal of Congo red from wastewater

Due to the highly toxic and non-degradable nature of Congo red (CR) in wastewater, how to effectively separate CR from an aqueous solution remains a major challenge in the field of wastewater treatment. Consequently, an γ-AlOOH/Fe3O4 composite was prepared using the sol-gel method under ultrasonic stirring conditions. The structural and surface properties of the magnetic γ-AlOOH/Fe3O4 composite were analyzed in detail using a range of physical and chemical characterization methods. It was shown that the γ-AlOOH/Fe3O4 composite possessed the advantages of its layered structure, high porosity, and positively charged surface, all of which were conducive to improving the adsorption capacity of CR. During our CR adsorption experiments, the maximum adsorption amount reached 1350.11 mg g−1. Simultaneously, the whole adsorption process was more consistent with the pseudo-second order kinetic and Langmuir isotherm model. The adsorption activation energy and thermodynamic data prove that the adsorption process was chemisorption, spontaneous, and endothermic. In addition, the γ-AlOOH/Fe3O4 composite can be easily separated from treated-wastewater upon the application of an external magnetic field and its excellent reproducibility increases its practical application value. Therefore, the γ-AlOOH/Fe3O4 composite synthesized in this study has a wide range of practical applications.

Green Synthesis of Cerium-Based Metal-Organic Framework (Ce-UiO-66 MOF) for Wastewater Treatment.

Green synthesis of metal-organic frameworks (MOFs) in aqueous solutions under ambient conditions with reduced production costs and environmental effects is an efficient technique to transfer lab-scale production to industrial large scale. Hence, this work proposes a green, low-cost, sustainable, rapid, and innovative synthetic strategy to produce cerium-based (Ce-UiO-66) MOFs under ambient conditions in the presence of water as a green solvent. This synthetic strategy exhibits great potential compared to conventional solvothermal synthetic techniques, and it does not need external activation energy and organic solvents, which can achieve the standards of green chemistry. Ce-UiO-66 MOF was synthesized successfully and utilized as a green adsorbent to efficiently eliminate anionic Congo Red (CR) dye from dye-containing wastewater. The experimental adsorption results were well matched to the pseudo-second-order kinetic and Langmuir isotherm models, in which the maximum CR adsorption capacity was measured to be about 285.71 mg/g. To evidence the applicability of Ce-UiO-66 MOFs in CR adsorption, the CR adsorption reaction was performed in the presence of interfering pollutants [e.g., salts (NaCl, KCl, and MgCl2) and cationic organic dyes (Malachite Green (MG) and Methylene Blue (MB)], where the results prove the promising adsorption performances of Ce-UiO-66 MOFs toward CR dye. Interestingly, the synthesized adsorbent exhibited high structural stability during repeated adsorption-desorption cycles, where the surface area of MOFs decreased from 555 to 376 m2/g after three cycles, while its CR adsorption capacity decreased by only 10% compared to that of the fresh adsorbent. All these outstanding properties indicate that the Ce-UiO-66 MOFs will be an effective adsorbent for water and wastewater treatment applications.

Sustainable economic production of silica nanoparticles from rice husks for adsorptive removal of anionic and cationic dyes

The present study explores a novel microwave-assisted (MW) approach for advancing the sol-gel synthesis of silica nanoparticles from rice husk (RSN) to mitigate methylene blue (MB) and congo red (CR). According to physico-chemical and yield analysis, 50 min of MW calcination produced a high yield of 92 % RSN (RSN50) with a high surface area (208 m2/g). Under optimized conditions, the maximum adsorption capacities of MB and CR on RSN50 were 48.1 mg/g (at pH 5.6, Langmuir model) and 58.5 mg/g (at pH 2, Hills model), respectively. The MB adsorption kinetics on RSN50 followed a pseudo-second-order indicating chemisorption while CR adsorption on RSN50 followed a pseudo-first-order mechanism and positive ΔG signifying non-spontaneity. A regeneration study for 5 consecutive cycles showed retention of % dye removal capacity. The cost assessment showed a profit when compared to commercial silica nanoparticles proposing an efficient, economical, and sustainable substitute for varied applications.

A novel Fe-containing carbon foam with hierarchical porous structure for efficient removal of organic dyes

A novel Fe-containing carbon foam (Fe-CF) was achieved with a hierarchical porous structure by carbonization of nano‑magnesium oxide/epoxy resin mixture followed by Fe(NO3)3 activation. The structures and properties of as-prepared Fe-CF were characterized via XRD, compression strength test, FESEM, TEM, BET, Raman and XPS, meanwhile the effects of adsorption conditions on the removal performance of Congo red (CR), Malachite green (MG) and Methylene blue (MB) by the Fe-CF are investigated through batch adsorption experiments. Results show that the Fe-CF obtained at 1000 °C possesses a fluffy and porous structure without obvious collapse and closure, and the iron oxide particles are evenly distributed on its surface, which endows it with high adsorption capacities for CR (1263.36 mg g−1), MG (679.84 mg g−1) and MB (483.66 mg g−1) at the optimum conditions, respectively. Furthermore, the adsorption process can be depicted well by the Langmuir and pseudo-second-order models, and the thermodynamic analysis results reflect that the adsorption processes are thermodynamically feasible and spontaneous. More importantly, the prepared adsorbent retains relatively high adsorption ability and stability even after five regeneration cycles.

Adsorptive behaviors and mechanisms for removing three organic pollutants from aqueous solutions by polyvinyl alcohol/porous carbon composite hydrogels

Confronted with severe water contamination induced by organic pollutants, developing low-cost adsorbents with high removal efficiency is a crucial approach to addressing the issue of residual organic pollutants in wastewater. This study prepared polyvinyl alcohol/porous carbon (PVA/C) hydrogels using freeze-thaw cycles and freeze-drying processes. And the adsorption behaviors were investigated with organic pollutants including congo red (CR), ibuprofen and doxycycline hydrochloride (DOX). Compared with pure PVA hydrogels, tensile test showed that PVA/coconut shell carbon hydrogel with a mass ratio of 10:2 (PCS2) had an increase of 285.78% in tensile stress. Through the adsorption experiment, PCS2 hydrogel demonstrated a good adsorption capacity for CR (27.39 mg/g), ibuprofen (15.48 mg/g), and DOX (17.07 mg/g). Furthermore, the adsorption mechanism of three organic pollutants by PCS2 hydrogel consistent with quasi-first-order kinetic and Freundlich adsorption isotherm model, indicating its adsorption process was dominated by multilayer physical adsorption. Therefore, this paper built a green, convenient, and economic method to prepare environmentally friendly and multifunctional PVA hydrogels for water purification.