Congo Red Molecules Research Articles

An attapulgite composite with high degradation performance for Congo red without using oxidants and photoexcitation

Dye wastewater poses a serious threat to water resources and the removal of dye molecules from dye wastewater has attracted much attention. In this work, attapulgite (ATP) mineral nanomaterials were firstly grafted with magnetic Fe3O4nanoparticles and then modified with polyethyleneimine (PEI) to prepare functionalized magnetic attapulgite composites (ATP-Fe3O4-PEI), which was used for the treatment of Congo red (CR) dye wastewater. The structure and surface properties of the composites were analyzed and characterized through FT-IR, XRD, SEM, TEM, BET analysis, zeta potential measurement, and VSM analysis. The removal performance of ATP-Fe3O4-PEI for CR was studied, and the removal mechanism was explored and revealed as well. It was believed that the CR removal by ATP-Fe3O4-PEI was mainly by a catalytic degradation process. Without photoexcitation and addition of oxidants in the solution, the system itself could produce H2O2 and hydroxyl radicals (·OH) to catalytically degrade the CR molecules. In addition, the removal of CR was further enhanced by adsorption of the composite material through electrostatic attraction, hydrogen bonds, and π-π interaction. Under the two removal behaviors, the removal rate of ATP-Fe3O4-PEI for CR was more than 95 % corresponding to a removal capacity of 943.77 mg·g−1 at pH = 3 and 25 °C. Moreover, the prepared ATP-Fe3O4-PEI materials have good recyclability with a removal rate and removal capacity above 82% and 799 mg·g−1 after 4 cycles. Within our best knowledge, this is the first report on the degradation of dye compounds by advanced oxidation without using oxidants and photoexcitation.

Tuning surface termination of CeO2 nanoparticles for adsorption of anionic dyes via urea content in a simple pyrolysis technique

CeO2 adsorbents with different terminated surfaces are fabricated by controlling urea content in simple pyrolysis methods. CeO2 adsorbent prepared with lower urea content is discovered to form a less positively charged surface with anoxic cerium-rich defect structures, inducing more difficult charge transfer in adsorbent interface and higher diffusion resistance in the interface of adsorbent and adsorbate. Thus, its adsorption isotherm is preferably fitted to Freundlich isotherms and its single adsorption site adsorbs multiple Congo red molecules, especially at higher dye concentrations. However, the adsorbent still has low adsorption ability. Oppositely, CeO2 adsorbent prepared with higher urea content induces forming a more positively charged surface with Ce-terminated structure due to higher Ce3+ concentration on its defect surface stabilized by Ce2O3 structure. CeO2 adsorbents with the Ce-terminated surface structures present easier charge transfer and lower diffusion resistance during dye adsorption. Significantly, they have much higher adsorption capacities of anionic dyes and their adsorption isotherm is better matched with Langmuir isotherms. Therefore, in the synthetic process of CeO2 adsorbents, urea content essentially regulates the arrangement structure of their terminated atoms, which greatly changes physicochemical properties of their terminal surfaces and influences the Congo red adsorption capacities.

Mesoporous biobased carbonaceous adsorbent for dye removal from water: Eutectic molten salts effect and adsorption mechanisms

Dye-polluted wastewater is released from various industries, such as textile and paint industries. Among different reclamation techniques, adsorption has been widely used for dye removal. Carbonaceous adsorbents, such as graphene, are among the most sought-after compounds for adsorption applications because of their high specific surface area and adjustable surface features. In this study, graphene-like carbon (GLC) was prepared from biomass as it is a facile and eco-friendly approach. Biomass-derived GLC was prepared by pyrolyzing waste wood in the presence of FeCl3/ZnCl2 as a eutectic binary mixture. Brunauer–Emmett–Teller (BET) and Raman analyses revealed that FeCl3 had a template effect during pyrolysis, whereas ZnCl2 acted as a pore former. Moreover, FeCl3 and ZnCl2 concentrations positively affected the BET value, regardless of the salt type. Further, waste wood-derived graphene-like carbon (WGLC) pyrolyzed at 900 °C with biomass: FeCl3: ZnCl2 at a ratio of 1:2:1 (WGLC-121) showed the highest specific surface area (2073.78 m2 g−1) and could remove >90 % of rhodamine B (RhB) and Congo red (CR) dyes. The pseudo-second order kinetic model showed a stronger correlation with the experimental data than the pseudo-first order model. While intra-particle diffusion was the rate-determining step in RhB adsorption, it did not influence CR adsorption. Further, the Freundlich model better explained the RhB (qmax = 633.86 mg g−1) and CR (qmax = 141.28 mg g−1) adsorption and revealed the superiority of WGLC-121 in dye removal compared to the previously reported adsorbents. The adsorption isotherm, energy, and thermodynamic parameters confirmed that the dyes were adsorbed through physisorption. Furthermore, the inter-molecular interaction between the RhB and CR molecules influenced the dye adsorption rate and isotherm. The findings of this study demonstrate the high potential of a binary mixture of FeCl3 and ZnCl2 for preparing carbonaceous adsorbents from waste wood to remove dyes from industrial wastewater.

Adsorption and Removal of Industrial Dyes by Water-Stabilized Aluminum-Based Metal–Organic Frameworks

Pollution of water resources by industrial dyes can threaten environmental safety and human health even at low concentrations. We proposed the adsorption removal of a typical azo dye, Congo red (CR), by CAU-23, an aluminum-based metal–organic framework (MOF). To characterize CAU-23, X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and thermogravimetry (TG) were employed. An investigation of the impact of the material on the adsorption kinetics, thermodynamics, and ionic strength of CR was conducted. The results demonstrated that the quasi-second-order kinetic model and Langmuir isotherm were in harmony with our experimental sorption data. Additionally, thermodynamic parameters of adsorption such as enthalpy and free energy were evaluated. Nanoporous CAU-23 with excellent water stability and suitable pore size is well suited for capturing CR molecules. Importantly, through a comprehensive investigation of experimental and theoretical studies, CAU-23 forms π–π interactions and electrostatic attraction with CR molecules, characteristics that promote CAU-23 as one of the most promising adsorbents for the elimination of CR from water.

Synergistically tailoring the hierarchical channel structure of graphene oxide membrane through co-assembly strategy for high-performance butanol dehydration

A significant boost in permeate flux along with the desirable separation factor remains a challenging issue for graphene oxide (GO) membranes in pervaporation applications. Herein, a facile approach of co-assembling pristine and etched GO nanosheets was proposed to tailor the hierarchical channel structure (involving the slits, defects and interlayer galleries) of GO membrane and achieve remarkable improvements in both the permeate flux and water/butanol separation factor. Pristine GO nanosheets guarantee a defect-free membrane structure, while etched GO (eGO) provides abundant defects/slits for molecular transport, thus reducing molecular diffusion resistance and doubling permeate flux. The introduction of eGO confers a more ordered nanosheet assembly and narrower interlayer spacing, thus strengthening the size-exclusion effect of the interlayer channels towards butanol molecules and realizing a 3-times enhancement in the separation factor. The subsequent intercalation of Congo red (CR) molecules ulteriorly optimizes the interlayer channels and results in the superior water/butanol separation factor of 5705 with the permeate flux of 4.81 kg/(m2h). This work provides a facile and feasible method for constructing high-performance GO-based membranes with great potential for practical butanol dehydration process.

Efficient removal of refractory dyestuffs from textile wastewater by composite hydrated alumina derived from waste aluminum polishing solution

The present investigation is aimed at fabricating a cheap and efficient adsorbent for the removal of refractory dyestuffs from wastewater. By using waste aluminium polishing solution as the raw material, a composite hydrated alumina (CHA) was successfully prepared and its properties were characterized by the methods of FTIR, SEM, EDS, BET, TGA, and XPS. It was shown that the resulting two-layer adsorbent exhibits a flower-like shape, in which, alumina acts as the core and the surface is modified by phosphate groups and hydrogen bonds in the outer layer. Various functional groups on the surface provide multiple interactions with anionic dyestuffs such as Congo red (CR) and Reactive blue (RB). However, due to the contained N- double bond in the molecular structure in CR, the adsorbent exhibits an especially excellent selectivity and adsorption capacity for the removal of CR, which is caused by the formation of the hydrogen bonds between the hydroxyl groups of CHA and the azo and aromatic rings in CR molecule. The obtained results provide a novel approach to remove refractory organic pollutants from wastewater by using a cheap adsorbent derived from industrial waste.

Mussel-inspired encapsulation of poly(pyrogallol-tetraethylenepentamine) resin into mesoporous MSU-H matrix and its rapid removal feature for Congo red from aquatic environment

Removing organic dyes from polluted water by mesoporous polymeric composite has recently attracted intensive attentions. Herein, the mesoporous poly(pyrogallol-tetraethylenepentamine)/MSU-H (PPTA/MSU-H) adsorbent was tapped for the capture of Congo red (CR) in aquatic environment via mussel-inspired encapsulation strategy. Many characterizations (e.g. FT-IR, SEM, BET, etc) are employed to confirm the successful decoration of PPTA resin. Effects of composite components, initial concentrations, environmental temperatures, adsorbent dosages, initial pH values, and foreign ions on the removal of CR by PPTA/MSU-H-x composites have been investigated successively. At optimal conditions of process variables, PPTA/MSU-H-20 exhibits the highest R% value (94.79 %) and reaches adsorption equilibrium at 180 min. The adsorption behavior of the representative adsorbent is matched well with the pseudo-second-order model, meaning one CR molecule binds with two capture sites. Furthermore, it indicates a monolayer homogeneous adsorption on PPTA/MSU-H-20 with the maximum theoretical capacity of 222 mg g−1 according to the well fitted Langmuir model. The removal mechanism of CR may be ascribed to hydrogen bonding, π-π stacking, electrostatic attraction, pore filling effects, and addition reaction. Overall, results reveal that mesoporous PPTA decorated adsorbent has a rewritable refabrication character and excellent specificity for the anionic dye purification in polluted water.

Fe, N, S co-doped cellulose paper carbon fibers as an air-cathode catalyst for microbial fuel cells

The heteroatoms and transition metal co-doped carbon-based catalysts are an important way to improve the catalytic activity of oxygen reduction reaction (ORR). Herein, we reported a facile method to obtain iron, nitrogen, and sulfur co-doped cellulose paper carbon fibers as catalysts (Fe–N–S/CFs) for ORR in microbial fuel cells (MFCs) with the adsorption recovery of Congo red molecules from dye wastewater. The thermal treatment promoted the etching of carbon surface by ferric ions, resulting in increased surface roughness for forming the defective carbon structure. The rich active species and defective carbon formed on the etched surface to enhance the electroactive surface area and effective sites. Fe–N–S/CFs catalysts achieved high half-wave potential due to the synergy effect between chemical components and defect structures. The assembled single-chamber air cathode MFC gained a high maximum power density of 1773 ± 40 mW m−2 versus Pt/C MFC of 1325 ± 94 mW m−2. This work provides a strategy for recovering dye molecules from wastewater to prepare non-precious metal catalysts for enhancing ORR activity.

Comparative study of ZIF-8-materials for removal of hazardous compounds using physio-chemical remediation techniques

The inherent toxicity, mutagenicity and carcinogenicity of dyes that are discharged into aquatic ecosystems, harming the health of humans and animals. ZIF-8 based composites are regarded as good adsorbents for the breakdown of dyes in order to remove or degrade them. In the course of this research, metal-organic framework materials known as ZIF-8 and its two stable composites, ZIF-8/BiCoO3 (MZBC) and ZIF-8/BiYO3 (MZBY), were produced via a hydrothermal process and solvothermal process, respectively, for the dangerous Congo red (CR) dye removal from the solution in water using adsorption method. According to the findings, the most significant amount of CR dye that could be adsorbed is onto MZBC, followed by MZBY and ZIF-8. The pseudo-second-order kinetic model was used effectively to match the data for adsorption behavior and was confirmed using the Langmuir isotherm equation. There is a possibility that the pH and amount of adsorbent might influence the adsorption behavior of the adsorbents. According to the experiment results, the technique featured an endothermic adsorption reaction that spontaneously occurred. The higher adsorption capability of MZBC is because of the large surface area. This results in strong interactions between the functional groups on the surface of MZBC and CR dye molecules. In addition to the electrostatic connection between functional group Zn–O–H on the surface of ZIF-8 in MZBC and the –NH2 or SO3 functional group areas in CR molecules, it also includes the strong π–π interaction of biphenyl rings.

Hierarchically porous carbon derived from pore remodeling of waste polymeric membranes for high-efficiency adsorption applications

It is extremely significant but technically challenging to construct a hierarchically porous carbon with prominent superiority in substance affinities and mass transfer for improving the adsorption performance. Herein, the waste-derived carbon (AC-KOH) with multimodal pore structures was successfully synthesized by thermally remodeling the pores of waste hollow fiber membranes collected from sewage-treatment plants. Mechanism study revealed that KOH etching in the original pores of polyvinylidene fluoride (PVDF) film leaves micropores, while the development of meso‑macropores is induced by polyethylene terephthalate (PET) liner pyrolysis and subsequent re-crosslinking and cyclization surrounding KOH. The synergism of macro-meso-micropores enabled the fast diffusion of molecules from the bulk solution to adsorption sites, thereby AC-KOH exhibited fast adsorption kinetics for removing four types of phenolic pollutants and small dye molecules (molecular weight <350 g/mol). More importantly, hierarchically porous AC-KOH displayed a 24 times higher kinetic constant than that of PVDF-AC with mono-micropores for the adsorption of larger Congo red molecules (697 g/mol), with a maximum adsorption capacity of 2519.2 mg/g, which is much higher than many reported adsorbents. This work offers a sustainable way toward waste membrane reutilization and demonstrates a new design strategy for constructing hierarchical pores to overcome the technical challenges of adsorption.

Adsorption of methylene blue and Congo red from aqueous solution on 3D MXene/carbon foam hybrid aerogels: A study by experimental and statistical physics modeling

In this paper, a new type of adsorbent MXene/carbon foam hybrid aerogel (MCF) was synthesized from Ti3C2TX-MXene and melamine foam (MF), and its removal properties of both cationic and anionic dyes were studied. The physicochemical properties of MCF were analyzed by a variety of characterization techniques, while its dye adsorption mechanism was further elucidated by the statistical physics models. The results show that MCF exhibited excellent adsorptive efficiency towards the two hazardous dyes methylene blue (MB) and Congo red (CR), and their adsorption capacity were 356.97 mg/g and 647.75 mg/g, respectively, which were fitted better for the Langmuir equation and quasi-second-order kinetic model. Moreover, the mechanism of MCF-MB and MCF-CR adsorption systems was discussed through the saturated multilayer model at the molecular level. The numerical simulation results show that the MB molecules were adsorbed by MCF in the form of dimer, which was a process of multi-anchoring (303 K and 318 K), single connection (333 K) and mixed adsorption orientation. On the contrary, CR molecules were adsorbed as monomers, which was a process of multi-anchored and pure non-parallel adsorption directions (303 K and 318 K) and mixed adsorption orientation (333 K). From the statistical physical and thermodynamic analysis, the adsorption mechanism of MB and CR onto MCF was mainly determined by the receptor density (Dm), which was a reversible endothermic adsorption process driven by the physical interaction, and high temperature was beneficial to the occurrence of high adsorption capacity.

A tunable CuDyO4 affixed exfoliated S-doped graphene oxide s-scheme heterojunction sheet photocatalytic degradation towards dye from aqueous solution

• S-scheme heterojunction SGOxCu 1-x DyO 4 was successfully synthesized by hydrothermal route. • The heterojunction exhibited high photocatalytic efficiency for removal of organic pollutants. • The heterojunction materials showed better performance compared with pristine material. • As-prepared heterojunction can be employed for successive use. In this work, visible light-responsive s-scheme heterojunction SGOxCu 1-x DyO 4 was felicitously fabricated by the in-situ hydrothermal method. These were subsequently investigated for the photocatalytic degradation of an aqueous solution of Congo red (CR) dye molecules in the presence of visible light illumination. The morphology and elemental analysis of the composite were carried out by XRD, SEM and EDS. The FTIR spectra indicated the formation of composites for the hosts SGOxCu 1-x DyO 4 . Similarly, PL spectroscopy was employed to investigate the effective charge separation in the composts and from UV analysis band groups of the composites were found. Narrowing down of band gap from 3.2 eV of bare CuDyO 4 to 2.7 eV for SGO 0.25x Cu 1-x DyO 4 led to the production of photoinduced electrons and holes and the prevention of reunion of these charges. The optimal photocatalyst SGO 0.25x Cu 1-x DyO 4 demonstrated 93% degradation efficiency against CR after 60 minutes of exposure to visible light radiations. When compared with CuDyO 4 , SGOxCu 1-x DyO 4 exhibited greatly enhanced dye degradation efficiency. The recyclability test indicated that SGOxCu 1-x DyO 4 is a highly stable photocatalyst with four successive displaying degradation efficiency of 87%, 84% 78% and 71%, respectively. Owning to high photocatalytic efficiency and the potential to be used for multiple cycles SGO 0.25x Cu 1-x DyO 4 may be recommended for the practical elimination of CR dye from wastewater.

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.

Optimized adsorption and effective disposal of Congo red dye from wastewater: Hydrothermal fabrication of MgAl-LDH nanohydrotalcite-like materials

• MgAl-LDH was synthesized ideally using the hydrothermal method. • MgAl-LDH exhibited excellent adsorption capacity for CR dye compared with previously prepared LDH compounds and other sorbents. • The experimental adsorption data adequately fit the Langmuir isotherm model. • Pseudo-second-order kinetic model best represents the adsorption data. • The interaction mechanism of CR to the MgAl-LDH surface was strengthened by electrostatic attraction. The effectiveness of Congo red (CR) adsorption from aqueous solutions onto MgAl-layered double hydroxide (MgAl-LDH) nanosorbents was examined in this study. MgAl-LDH was synthesized using the hydrothermal method, and physicochemical characterization was performed via powdered X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared analysis, and zeta potential measurements. For optimum adsorption of CR onto the synthesized MgAl-LDH nanosorbent, the adsorption process was employed in batch experiments. Adsorption parameters, such as the adsorbent dosage, solution pH, contact time, and initial adsorbate concentration, vary with the adsorption kinetics and isotherm mechanism. The results of the batch experiments indicated rapid adsorption of CR dye from aqueous solutions onto MgAl-LDH during the first 30 min until equilibrium was achieved at 180 min with a dye concentration of 50 mg/100 mL and MgAl-LDH adsorbent dosage of 0.05 g. The experimental adsorption data fit adequately with the monolayer coverage under the Langmuir isotherm model ( R 2 = 0.9792), and showed the best fit with the pseudo-second-order kinetic model ( R 2 = 0.996). The change in zeta potential confirmed the effective adsorption interaction between the positively charged MgAl-LDH and the negatively charged CR molecules with electrostatic interactions. This work is distinguished by the successful hydrothermal preparation of MgAl-LDH in the form of homogenous nanoscale particles (∼100 nm). The prepared MgAl-LDH showed a high adsorption capacity toward anionic CR dye with a maximum adsorption capacity of 769.23 mg/g. This capacity is higher than those reported for other adsorbents in previous research.

Capability of potato peel powder (PPP) for the adsorption of hazardous anionic Congo dye

Congo red is a toxic anionic dye that is found in large amounts in textile industry effluents. Potato (Solanum tuberosum (STP) peel powder is inexpensive and readily accessible; it was utilized in this research to remove Congo red dye from an aqueous solution. The adsorbent was characterized by Fourier-Transform infrared and scanning electron microscopy techniques. For adsorption of Congo red dye on Solanum tuberosum peels the optimum conditions were an adsorbent dose of 0.6 g, contact time of 90 minutes, solution pH of 3, with adsorbates initial concentration 30 ppm and temperature are 50 °C, respectively. According to isothermal investigations, the sorption data was best fit with Freundlich and D–R isotherm. The kinetics of the process was found best to follow the pseudo-second order with (R 2 = 1) and Q e ( cal ) = 9.97 mg/g, which is close to the Q e ( exp ) = 9.96 mg/g. The plot of these two models demonstrated that physisorption and chemical adsorption were both possible. The fact that Δ G and Δ H are negative implies that the adsorption was spontaneous and exothermic. The findings of the desorption investigation revealed that 78% of the adsorbent had been regenerated and was ready for more adsorption studies. The procedure of applicability with tap water was investigated, and the results revealed that 72% of the Congo red dye was adsorbed under optimized conditions. Potato peel powder might be used as biosorbent for the treatment of effluents from dying and textile industries due to the high capability of Congo red dye. HIGHLIGHTS Adsorptive removal of Congo red by using potato peels powder was carried out. The OH− & COO− groups on the PPP surface provided excellent binding with Congo red molecules. The equilibrium attained in 90 minute at pH 3.0. Kinetics, isotherm models, and thermodynamics were evaluated. Desorption study resulted in 78% regeneration of potato peels powder and Congo red dye.

Binary dyes adsorption onto novel designed magnetic clay-biopolymer hydrogel involves characterization and adsorption performance: Kinetic, equilibrium, thermodynamic, and adsorption mechanism

Nowadays, the treatment of dyes and pigments was considered a serious challenge in the world. In this work, a novel high-performance magnetic bio-based κ-carrageenan-kaolinite hydrogel (CKAlFe) was designed, characterized, and used for the simultaneous adsorption of Alizarin red and Congo red dyes from an aqueous solution. The morphological characterization revealed the successful preparation of non-rigid and plate-like CKAlFe adsorbent with the microporosity structure, in which the κ-carrageenan forms the amorphous part and kaolinite clay, Al2O3, and Fe3O4 are involved in the crystalline part of the structure. It was found as an efficient adsorbent with maximum adsorption capacities of 26.9 and 33.5 mg/g toward Congo red and Alizarin red molecules respectively. The adsorption capacity of CKAlFe was decreased in acidic media. The adsorption kinetics followed the pseudo-second-order kinetic model. The intra-particle diffusion controlled the adsorption rate at low initial concentrations, while the transfer rate of molecules from solution to the surface of CKAlFe played this role at higher concentrations. Also, the adsorption isotherm followed the extended Langmuir isotherm model. The thermodynamic study demonstrated that Congo red and Alizarin red binary adsorption onto CKAlFe was endothermic and spontaneously occurred, while Alizarin red molecules required more energy than Congo red to be adsorbed and a higher fraction of the active sites were occupied by Congo red molecules. The mechanism study showed that multiple interactions including π-π stacking, electrostatic interaction, dipol-dipol H bonding, and Yoshida H bonding can be involved in the adsorption process of studied dyes onto CKAlFe. Besides, the isosteric enthalpy of adsorption revealed that the adsorption type varied from physical to chemical process, increasing the amount of adsorbed dyes. The prepared magnetic hydrogel is highly capable of being used in drug delivery for selectively detection, hyperthermia/thermal ablation, and different products already on the market.

Enhanced Congo Red Adsorption and Photo-Fenton Oxidation over an Iron-Impeded Geopolymer from Ferruginous Kaolinite: Steric, Energetic, Oxidation, and Synergetic Studies.

An iron-impeded geopolymer (Fe/GP) was synthesized from natural ferruginous kaolinite and optical waste for enhanced decontamination of Congo red (CR) dye. The adsorption properties of Fe/GP were assessed using an advanced monolayer equilibrium model of one energy (R2 > 0.99). Fe/GP possessed an active site density of 391.3 mg/g, which induced an adsorption capacity of 634 mg/g at the saturation state. The number of adsorbed CR molecules per site (n = 1.56–1.62) reflected the possible uptake of two molecules per site via a multimolecular mechanism. The adsorption energy (5.12–5.7 kJ/mol) reflected the physical adsorption of the CR molecules via hydrogen bonding and/or van der Waals forces. As a catalyst, notable activity toward photo-Fenton oxidation was achieved even at high CR concentrations. Complete oxidation was observed after 30 (CR concentration: 10 mg/L), 50 (20 mg/L), 80 (30 mg/L), 120 (40 mg/L), and 140 min (50 mg/L). High oxidation efficiency was achieved using 0.1 g/L Fe/GP, 0.1 mL of hydrogen peroxide (H2O2), and a visible light source. Increasing the Fe/GP dosage to 0.3 g/L resulted in complete oxidation of CR (100 mg/L) after 220 min. Therefore, synthetic Fe/GP can be used as a low-cost and superior catalyst and adsorbent for the removal of CR-based contaminants via adsorption or advanced oxidation processes.

Effect of surface hydroxyls and porous nanostructured sensors integrated for SERS monitoring and efficient removal of organic pollutants

As an excellent nanomaterial, AlOOH has a molecular enrichment effect derived from the large number of hydroxyl groups on its surface and its porous structure, which increases the molecular density in the hot spot region of Ag nanoparticles with plasmonic properties, provides the surface-enhanced Raman scattering (SERS) activity and realizes the detection of probe molecules. In our work, the composite AlOOH@Ag is rationally formed as an SERS substrate successfully applied to the detection of Congo Red (CR) molecules even at the trace level thanks to the formation of hydrogen bonds. Our successful analysis of the toxic dye molecules Rhodamine 6G (R6G), Crystal Violet (CV) and CR in a mixture demonstrates the universality of AlOOH@Ag as an SERS substrate and the great potential for recognition of a target. Importantly, the AlOOH@Ag has excellent molecular adsorption properties to remove harmful molecules, and a dual-functional SERS sensor that integrates detection and removal is achieved. Monitoring and adsorption tests under different pH spectrum environments were also performed. Importantly, the detection in real samples is even more successful. This versatile all-in-one SERS substrate provides platforms for the development of convenient sensors to be applied in actual environmental processing.

Plasmonic Ag decorated AlOOH for highly sensitive SERS detection of affinity OH groups molecules enriched in hotspots

Significant breakthroughs have been made in the development of surface-enhanced Raman scattering (SERS) substrates constructed by depositing plasmonic Ag onto nanostructured platforms. AlOOH is widely fabricated using hydrothermal, microwave, and microemulsion methods. Among these, the high catalytic activity of AlOOH prepared by the microemulsion method is derived from its high specific surface area, more active surface OH groups, and multi-active adsorption sites. And nanomaterials with such excellent properties have not yet been fabricated on a SERS-based platform to improve the Raman-enhanced properties of Ag achieving high-sensitivity detection of probe molecules especially with affinity for OH groups. The precious metal Ag has long been known to serve as traps to capture electrons and holes generated by plasmon resonance, reducing electron–hole recombination and exhibiting high activity in photocatalytic processes. In this work, to demonstrate the SERS substrate activity of the AlOOH@Ag complex, it has been successfully applied to identify congo red (CR) molecules with high sensitivity, methyl blue (MB) and methyl orange (MO), enabling trace-level detection with enhanced performance much stronger than Ag substrate.

Adsorption of Congo Red dye on CuO nanoparticles synthesized by green method using Nyctanthes arbor‐tristis leaf extract: Experimental and theoretical study

AbstractCopper oxide nanoparticles (CONs) are synthesized using the leaf extract of Nyctanthes arbor‐tristis. They are further characterized using FE‐SEM and EDX techniques and successfully used for the removal of Congo Red (CR) dye. To enhance the removal efficiency, the effect of various parameters viz. shaking time, adsorbent dose, pH, etc. are studied. The kinetic model showed that the CR adsorption on CON followed the pseudo‐first‐order reactions. Langmuir isotherm modeling is best fitted and describes the CR‐CON adsorption system for CR dye in 90 min with Qmax at 333.33 (mg/g). At varying temperatures, the statistical physics model computed the number of bound CR dye molecules and the saturation adsorption capacity for both functional groups. At 298, 308, and 318 K, the values of “n” are 0.379, 0.358, and 0.328, respectively, which showed that CR molecules interacted with two and three functional groups of the CON surface through a horizontal adsorption orientation. The role and importance of suggested functional groups on dye adsorption as well as their thermodynamic characteristics are determined using a statistical physics model. The reused study is applied to the CON and their efficiency is excellent up to five cycles, making CON an effective pollution control material that may be commercialized in the near future.