Efficient Removal Of Organic Dyes Research Articles

Magnetic activated carbon for the removal of methyl orange from water via adsorption and Fenton-like degradation

Water pollution caused by organic dyes is a critical environmental issue. Although activated carbon (AC) is commonly used for dye adsorption, its effectiveness is limited by challenges in separation and regeneration. To address these limitations, a convenient recyclable magnetic activated carbon (MAC) was fabricated via co-precipitation and calcination method, serving as adsorbent and catalyst for methyl orange (MO) removal through a Fenton-like degradation process. Characterization techniques, including XRD, FTIR, SEM and TEM, confirmed that Fe3O4 nanoparticles (10–20 nm) were uniformly dispersed on AC surface. The MAC maintaining a high surface area (997 m2/g) and pore volume (0.795 cm3/g) and exhibited superparamagnetic properties with a saturated magnetization of 5.52 emu/g, enabling effective separation from aqueous solutions by magnet. Batch adsorption studies revealed that MO adsorption onto MAC followed pseudo-second-order kinetic and Freundlich isotherm model, with a maximum adsorption capacity of 205 mg/g at 25 °C. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. Simultaneous degradation of MO and in-situ regeneration of MAC were achieved via Fenton-like reaction using sodium persulfate (PS). Under a PS concentration of 9 mmol/L, the MO removal efficiency near 95% after 60 min, with a total organic carbon (TOC) reduction of 83.1%. The reaction of Fe3O4 and oxygen functional groups on AC surface with PS facilitated the generation of SO4•-, thereby enhancing catalytic degradation of MO. The degradation efficiency improved as the temperature increased from 25 °C to 45 °C. Cycle tests demonstrated that the MO removal efficiency of MAC remained above 90% after 5 cycles of regeneration. Overall, this study highlights the potential of MAC for efficient removal of organic dyes from water through the coupling of adsorption and Fenton-like degradation, providing a promising solution for addressing water pollution challenges.

New recyclable and functionalized chitosan-based polyurethane foams for effective and incessant removal of Orange II (OII) and Rhodamine B (RhB) dyes from water

The development of new efficient materials for the removal of water-soluble toxic organic dyes has been one of the focused research areas in the recent past. There is a strong demand for the new materials as most of the reported techniques/materials suffer from serious limitations. In this regard, a series of flexible chitosan-based task-specific polyurethane foams (PUCS-GP, PUCS-CA-GP, PUCS-TA-GP, and PUCS-GA-GP) associated with naturally available hydroxycarboxylic acids was developed. The basis for the preparation of these task-specific and functionalized PU foams is to possess amine groups for trapping the anionic dyes (example: Orange II denoted as OII) and carboxylic acid groups for attracting the cationic dyes (example: Rhodamine B denoted as RhB) under specified pH conditions. Batch adsorption experiments were conducted to assess and improve various parametric conditions. The experimental results revealed that the adsorption kinetics closely agree with the pseudo-second-order model having a maximum sorption capacity of 38.3 mg/g at pH 3 for OII on PUCS-GP and 48.4 mg/g at pH 6 for RhB on PUCS-CA-GP. Furthermore, the adsorption process was described by isotherms, kinetic equations and thermodynamic parameters (ΔG°, ΔH° and ΔS°). Notably, the regeneration of OII and RhB dyes from the exhausted PUCS-GP and PUCS-CA-GP materials was effectively accomplished. The recovered PUCS-GP shows >90 % OII and PUCS-CA-GP displays >70 % RhB removal efficiency even after twelve adsorption–desorption processes under mild conditions, demonstrating excellent recyclability/durability. The advantages of these functionalized foam materials are facile preparation, high adsorption capacity, good reusability, and very efficient removal of organic dyes from wastewater streams.

CdS quantum dots modified two-dimensional MXene photocatalytic membrane for efficient removal of organic dyes from aquatic systems

MXene, a novel two-dimensional (2D) material, has been applied for the removal of dye molecules from wastewater; owing to its ability to stack into unique interlayer permeation channels. However, the narrow interlayer permeation channels of MXene limit its high permeability, and the dye contaminants tend to block the channels on the membrane surface as well as between the laminae. In view of this, CdS quantum dots (QDs) were incorporated with photocatalytic ability into the MXene channels, and the fabricated CdS QDs@MXene/PVDF photocatalytic composite membrane had high separation efficiency by using PVDF polymer as the support layer. The results manifested that; the CdS QDs were homogeneously dispersed in the MXene separation layer, and the introduction of CdS QDs optimized the interlayer permeation channels of MXene, with permeate flux of 502.6 L·m−2·h−1. The composite membrane exhibited an excellent removal of Congo red and Rhodamine B (CR and Rh B) dyes under the coupling of membrane separation and photocatalytic process, with the optimal removal ratio of 97.3 % for CR and 98.5 % for Rh B, respectively. Moreover, the CdS QDs endowed the membrane with self-cleaning ability, superior permeability and selectivity under five consecutive photocatalytic cycles, demonstrating the great in-situ resistance to contamination. After five intermittent cycles, the dye retention rate still exceeded 90 % and the permeate flux reached 388.0 L·m−2·h−1. This study provides an exceptional reference for quantum dots modified two-dimensional MXene membranes.

Co3O4–TiO2 supported into N-doped magnetic 3D porous microspheres as the “one stone with two birds” strategy for highly efficient removal of organic dyes via synergistic adsorption-photocatalysis

Constructing heterojunctions with rich porosity and unique microstructures is the main way to obtain efficient adsorption and photocatalysis. A ternary composite of Co3O4–TiO2 supported in N-doped magnetic 3D porous microspheres (Co3O4–TiO2/N-MCMs) was successfully constructed with hierarchical pore structures, large specific surface areas, and abundant active sites. The Co3O4–TiO2/N-MCMs possessed excellent adsorption and solar degradation capabilities for representative azo dye (methyl orange, MO) and triphenylmethane dye (rhodamine B, RhB), and the total removal rate of the two dyes with different initial concentration reached up to 99.0% and 99.2% within 2 h, respectively. MO and RhB were rapidly adsorbed and enrichment into Co3O4–TiO2/N-MCMs via pore filling, and then degraded by the nucleophilic reagents (•O– 2 and •OH). Characterizations and theoretical calculations demonstrated that Co3O4–TiO2/N-MCMs contained a sufficient amount of p-n type heterojunctions between Co3O4 and TiO2, which could effectively promote spatial separation of photogenerated e--h+ pairs to improve degradation ability and reduce band gap to extend visible-light absorption. Moreover, N-doping could further transfer photogenerated electrons from heterojunctions to reaction areas to effectively prolong the lifetime of photogenerated electrons. The LC-MS results showed that MO and RhB can be mineralized into H2O and CO2 without generating any secondary pollution. Furthermore, Co3O4–TiO2/N-MCMs exhibited excellent magnetic separation capability and reusability. This study designed a novel photocatalyst for highly efficient removal of organic dyes via “One stone with two birds” strategy of synergistic adsorption-photocatalysis, which could simplify the treating process and exhibit a highly promising in practical applications.

Surface modified of chitosan by TiO2@MWCNT nanohybrid for the efficient removal of organic dyes and antibiotics

Considering the increase in the discharge of industrial effluents containing dyes and antibiotic resistance as a consequence of increasing the prescription and easy distribution of antibiotic drugs at the global level, designing efficient, biodegradable and non-toxic absorbents is necessary to reduce environmental harm effects. Herein, we present a series of novel eco-friendly ternary hybrid nanocomposite hydrogels CS/TiO2@MWCNT (CTM) composed of chitosan (CS), TiO2, and multiwalled carbon nanotube (MWCNT) for removal of methylene blue (MB) and methyl orange (MO) and common antibiotic ciprofloxacin (CIP) in aqueous medium. The combination of MWCNT and TiO2 improves the physicochemical properties of CS hydrogel and increases the adsorption capacity toward pollutants in the presence of different loadings. CTM hydrogel showed a specific surface area of 236.45 m2 g−1 with a pore diameter of 7.89 nm. Adsorption mechanisms were investigated in detail using kinetic, isotherm, and thermodynamic studies of adsorption as well as various spectroscopic techniques. Adsorption of these pollutants by CTM nanocomposite hydrogel occurred using various interactions at different pHs, which showed the obvious dependence of CTM adsorption capacity on pH. Electrostatic attractions, complex formation, π-π stacking and hydrogen bonds played a key role in the adsorption process. The adsorption of MB, MO, and CIP was fitted with the Langmuir isotherm with maximum adsorption capacities of 531.91, 1763.6, and 1510.5 mg g−1, respectively. CTM had a minor decrease in adsorption strength and showed good structural stability even after 8 adsorptions–desorption cycles. The total cost of producing a 1 kg adsorbent was calculated to be $ 450, which helped us determine the economic feasibility of the adsorbent in large-scale applications.

Upcycling of PVC waste to high-value sorbent with KOH-activation for efficient removal of organic dyes

Polyvinyl chloride (PVC), known for its chemical stability and flame-retardant qualities, has many uses in various fields, such as pipes, electric wires, and cable insulation. Research has established its potential recovery as a fluidic fuel through pyrolysis, but the use of PVC pyrolysis oil, which is tainted by chlorine, is constrained by its low heat value and harmful environmental effects. This study engineered a layered double hydroxide (LDH) to tackle these challenges. The LDH facilitated dechlorination during PVC pyrolysis and bolstered thermal stability via cross-linking. During pyrolysis with LDH, PVC was transformed into carbon-rich precursors to sorbents. Chemical activation of these residues using KOH created sorbents with a specific surface area of 1495.4 m2 g⁻1, rendering them hydrophilic. These resulting sorbents displayed impressive adsorption capabilities, removing up to 486.79 mg g⁻1 of methylene blue and exhibiting the simultaneous removal of cations and anions.

Design of novel FeSe2/ZnO composites and their application in photodegradation of methylene blue

Water pollution has become one of the major global issues, posing serious threat to both humans and aquatic life. The elimination of organic industrial pollutants from wastewater is currently a major area of research. Herein, we report for the first time a novel FeSe2/ZnO composite system for highly efficient removal of organic dyes under visible light. FeSe2/ZnO composites with varying mass ratios of FeSe2 were successfully prepared through simple and low-cost chemical method. The physiochemical properties of the prepared FeSe2/ZnO composites were carefully evaluated and compared with those of pure ZnO rods and FeSe2 flowers. UV–vis spectroscopy confirmed that the coupling of FeSe2 with ZnO caused a significant improvement in the optical absorption of ZnO. The bandgap energies of FeSe2/ZnO composites showed a red shift with increasing the ratio of FeSe2 flowers. The prepared samples were evaluated for their photocatalytic response against the removal of methylene blue dye. Compared to the pure FeSe2 and ZnO, the composites displayed impressive photocatalytic performance. Among the prepared samples, composite with an optimum ratio of 75 wt% FeSe2 revealed outstanding photocatalytic efficiency, making it a promising candidate for the removal of organic pollutants.

Carbon encapsulated ZnO nanoplates for efficient removal of organic dyes from aqueous medium by adsorption: Role of organic ligand and calcination temperature

Water pollution by organic dyes poses great challenge to the environment as well as living organisms. Herein, we have fabricated nanoplates of ZnO in carbon matrix by controlled calcination of zinc-metal organic frameworks (Zn-MOFs) and used as adsorbents for efficient removal of organic dyes from water. Zn-MOF of phthalic acid and 5-nitrophthalic acid produced nanoplates of ZnO (ZnO-C and ZnO-NC) in carbon matrix without and with nitrogen doping. The fabricated hybrid nanostructures were characterized using PXRD, FTIR, BET, TGA, HR-SEM, HR-TEM and XPS analysis. Both ZnO-C and ZnO-NC showed high adsorption of cationic dyes (crystal violet (CV), methylene blue (MB) and Rhodamine B (Rh B)) compared to anionic dyes (methyl orange (MO) and Eosin yellow (EY)). Nitrogen doped ZnO-NC exhibited relatively higher percentage of dyes removal (99 %) compared to ZnO-C. Interestingly, ZnO-NC showed high adsorption of MB dye across the pH range from acidic (pH = 3.0) to alkaline (pH = 11.0). The zero-point charge indicated the negative surface charge for ZnO-NC/ZnO-C that facilitated electrostatic interactions between dyes and adsorbents. Adsorption kinetics suggested a pseudo second order model and adsorption isotherm fitted well with the Freundlich model, suggesting heterogenous adsorption with multilayer coverage of dye molecules. The reusability of ZnO-NC showed only slight reduction of adsorption in three successive cycles. Further, ZnO-NC was used as column packing materials for the successful removal of both cationic as well as anionic dyes upon filtration. Thus, the present studies provided insight on the organic ligand structure and calcination temperature of MOFs for transforming them into effective organic dye adsorbent.

Sonocatalytic Fe3O4 cluster microspheres/g-C3N4 composite for efficient removal of organic dyes

Sonocatalytic Fe3O4 cluster microspheres/g-C3N4 composite for efficient removal of organic dyes

Urchin-like CO2-responsive magnetic microspheres for highly efficient organic dye removal

CO2-responsive materials have emerged as promising adsorbents for the remediation of refractory organic dyes-contaminated wastewater without the formation of byproducts or causing secondary pollution. However, realizing the simultaneous adsorption−separation or complete removal of both anionic and cationic dyes, as well as achieving deeper insights into their adsorption mechanism, still remains a challenge for most reported CO2-responsive materials. Herein, a novel type of urchin-like CO2-responsive Fe3O4 microspheres (U-Fe3O4 @P) has been successfully fabricated to enable ultrafast, selective, and reversible adsorption of anionic dyes by utilizing CO2 as a triggering gas. Meanwhile, the CO2-responsive U-Fe3O4 @P microspheres exhibit the capability to initiate Fenton degradation of non-adsorbable cationic dyes. Our findings reveal exceptionally rapid adsorption equilibrium, achieved within a mere 5 min, and an outstanding maximum adsorption capacity of 561.2 mg g−1 for anionic dye methyl orange upon CO2 stimulation. Moreover, 99.8% of cationic dye methylene blue can be effectively degraded through the Fenton reaction. Furthermore, the long-term unresolved interaction mechanism of organic dyes with CO2-responsive materials is deciphered through a comprehensive experimental and theoretical study by density functional theory. This work provides a novel paradigm and guidance for designing next-generation eco-friendly CO2-responsive materials for highly efficient purification of complex dye-contaminated wastewater in environmental engineering.

Biologically inspired Co-MOF as catalase mimics with an unexpected ROS production ability for the efficient removal of organic dyes

Developing an efficient advanced oxidation technology is of great significance for water treatment and environmental protection. Here, inspired by the structure and feature of coenzyme B12 in natural enzymes (cleavage of Co-C bond triggers the generation of radical), a Co based metal-organic framework (Co-MOF) with catalase-mimicking activity was synthesized and applied in the degradation of organic dyes. Firstly, Co-MOF nanozyme was fabricated via the coordination self-assembly strategy at room temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive scanning (EDS), powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the morphology and structure. The results showed that the obtained Co-MOF nanozyme was rhombic dodecahedral morphology with a size of ∼ 500 nm and excellent crystallinity. The enzymatic experiments proved that such nanozyme possessed a single catalase-like activity. Further research results demonstrated that Co-MOF-based degradation process of acid fuchsin (AF) or crystal violet (CV) had excellent pH adaptability (pH > 5.0). Unexpectedly, an ultra-high catalytic degradation rate (211.35 min−1 g−1 L) was successfully achieved in the catalytic degradation of AF, and it was approximately 5∼200 times of the previous optimal nanozyme or catalysts. In complex matrices and real wastewater, this catalytic process could still maintain degradation efficiency above 90% or even higher within 5 minutes, proving its excellent stability and adaptability. The results of radical and electron quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analysis demonstrated that the excellent catalytic degradation performance was attributed to the generation of reactive oxygen species (ROS) (∙O2 was the main contributor) and the existence of electron transfer. In summary, this new catalytic property endows Co-MOF nanozyme with considerable potential for dye degradation, extending the application scope of catalase mimics.

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.

Wheat flour-derived amyloid fibrils for efficient removal of organic dyes from contaminated water

Amyloid fibrils derived from different proteins have been proved as a promising material for adsorption of various pollutants from wastewater, which showed advantages of low cost and eco-friendliness. However, most of the amyloid fibrils derived from animal-based proteins with high environmental footprint, while more sustainable amyloid fibrils derived from plant materials are desirable. In this study, a plant-derived amyloid fibril was extracted from the commonly used wheat flour with a simple and scalable protein purification and fibrillization process. Interestingly, the amyloid fibrils showed good adsorption capacity towards typical organic dyes (Eosin Y (EY) and Congo red (CR)) from contaminated water. Adsorption kinetic analysis indicated the adsorption process to EY or CR by wheat flour amyloid well fitted with a pseudo-second-order model. The adsorption also followed a Langmuir isothermal model with adsorption capacities of 333 mg/g and 138 mg/g towards CR and EY, respectively. This work demonstrated the feasibility to utilize the plant-based amyloid fibril for organic dyes removal from contaminated water, which provided an affordable, sustainable and scalable tool for organic dyes removal from wastewater.Graphical

Removal of organic dyes from aqueous solution using a novel pyrene appended Zn(II)-based metal-organic framework and its photocatalytic properties.

In this study, we report the efficient removal of organic dyes from aqueous solutions using a newly synthesized pyrene-appended Zn(II)-based metal-organic framework (MOF), ZnSiF6Pyrene MOF, with the chemical formula C52H32F6N4SiZn·4(CHCl3). The MOF was synthesized through a facile method at room temperature using a dipyridylpyrene ligand and ZnSiF6 metal source, resulting in a highly crystalline structure with pyrene functional groups forming the framework. The synthesized MOF was characterized using various analytical techniques, including Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD) analysis, and scanning electron microscopy (SEM). Thermal stability was assessed using thermogravimetric analysis (TGA), while the surface area of the MOF was determined using a Brunauer-Emmett-Teller (BET) surface analyzer. Furthermore, the single-crystal X-ray diffraction (SCXRD) structure was studied to authenticate its solid-state structure. The as-synthesized MOF exhibited remarkable adsorption capacity towards various organic dyes, including Congo red (CR), rhodamine B (RhB), and methyl violet (MV), due to its ample surface area and strong π-π interactions between the pyrene moieties and dye molecules, as demonstrated by experimental and in silico docking studies. The photocatalytic degradation of MV dye was also investigated. Detailed trapping tests indicate that hydroxyl (˙OH) and superoxide (O2˙-) radicals are likely the primary active species responsible for the photodegradation of the dye under study. Furthermore, the photocatalytic property of the MOF was investigated under visible light irradiation, demonstrating excellent ability to generate singlet oxygen. This study highlights the potential of pyrene-appended Zn(II)-based MOFs as promising materials for environmental remediation applications.

Porous organic polymers incorporating BODIPY moieties for efficient removal of organic dyes from aqueous solutions

The incorporation of BODIPY units into porous frameworks enhances the materials’ ability to efficiently adsorb organic dyes from aqueous solutions.

Multi-crosslinked robust alginate/polyethyleneimine modified graphene aerogel for efficient organic dye removal

Polymer composite aerogel holds great promise for sewage treatment. Here, a novel triply crosslinked alginate/graphene aerogel for efficient organic dye removal was reported. The triple crosslinking of aerogel was realized firstly by the association between in-situ released Ca2+ ions and sodium alginate (SA). And the electrostatic attraction between polyethyleneimine-modified reduced graphene oxide (PEI-RGO) and the alginate chain provides an additional boost to crosslinking the aerogel. Moreover, the hydrogen bonding between PEI and SA also helps in achieving the crosslinking of the aerogel. Thus, the robust triply crosslinked alginate/graphene aerogel was obtained with using cost-effective precursors and a straightforward process. Additionally, the as-prepared aerogels were employed to remove the cationic dyes from wastewater. It was found that the porous alginate/graphene exhibited a strong affinity to methylene blue (MB) and neutral red (NR). The adsorption process of the aerogel towards MB was in accordance with the Langmuir isothermal model and pseudo-second-order model, and the maximum theoretical adsorption capacities were 1091.9 and 813.2 mg g−1, suggesting its potential application in sewage treatment.

Efficient removal of organic dyes using electrospun nanofibers with Ce-based UiO-66 MOFs

Cerium-based UiO-66 (Ce-UiO-66) metal-organic frameworks (MOFs) were synthesized via a facile solvothermal method and fully characterized using FTIR, XRD, BET, SEM, EDX, and zeta potential techniques. The synthesized Ce-UiO-66 particles were embedded into an electrospun cross-linked polyvinyl alcohol (PVA)/chitosan (CTS) nanofiber (EPCNF), and then employed to remove organic dyes from water. The adsorption results demonstrated that the adsorption capacities of both anionic (Congo Red (CR), Methyl Orange (MO) and Methyl Red (MR)) and cationic (Methylene Blue (MB)) dyes over the fabricated electrospun nanofibers (ENFs) increased with increasing the loadings of Ce-UiO-66 MOFs. Accordingly, the adsorption performance of EPCNF-10 (containing 10 wt% of Ce-UiO-66 MOFs) adsorbent toward these organic dyes is in the order of CR (102.04 mg/g) > MO (87.71 mg/g) > MR (65.35 mg/g) > MB (34.24 mg/g). Moreover, it was found that the Freundlich isotherm model and the pseudo-second-order kinetic model were appropriate for describing the adsorption behaviors of EPCNF-10 adsorbent toward both anionic and cationic dyes. Thus, it can be proposed that the fabricated EPCNF-10 adsorbent would be effective adsorbent materials for the removal of anionic and cationic dyes from water due to its excellent adsorption performance, facile preparation, good regeneration, and simple separation from aqueous solutions.

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.

Magnetic Mesoporous Silica Nanoparticles Functionalized with 5,5′-Dithiobis(2-Nitrobenzoic Acid) for Highly Efficient Removal of Organic Dyes from Contaminated Water

The removal of organic pollutants has become an increasingly important environmental concern. In recent years, there has been significant research into the use of nanomaterials for removing organic dyes in single-component systems. In this study, magnetic mesoporous silica nanoparticles (magnetic MSNs) were prepared with an average particle size of 170 nm. Iron oxide nanoparticles (20 nm) were embedded within the mesoporous silica structure. These nanoparticles were functionalized with amine, derivatized with thiol, and then reacted with 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB). The presence of DTNB molecules attached to the surface was confirmed by FTIR spectra, as evidenced by the appearance of peaks at ∼1528 cm−1 and ∼1365 cm−1. The nanoadsorbents demonstrated high removal efficiency for bromothymol blue (BT) and methyl orange (MO) at a pH below 5, with a maximum adsorption capacity of 139.27 mg/g and 101.62 mg/g for BT and MO, respectively. The linear regression coefficient value suggested that the adsorption of BT and MO onto magnetic MSNs-DTNB followed the Langmuir isotherm and second-order process. Overall, these findings suggest that magnetic MSNs-DTNB could be a promising nanoadsorbent for removing organic pollutants from contaminated water sources.

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

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