Congo Red Dye Research Articles

Fabrication of temperature-regulated sorbitol/mannitol-doped copper oxides derived from a Cu complex and their photocatalytic properties

In this study, a series of composites containing copper oxide (CuxO) particles doped with sorbitol/mannitol, namely Cu/CuxO@C (x = 1 or 2), was successfully derived from a novel copper complex ([Cu(IPZ)2Cl2] (Cu-Complex), where IPZ = 4-Iodopyrazole) by pyrolysis method and exploiting the stability and modulation of the coordination sites of sorbitol/mannitol, which exhibited excellent photocatalytic properties. The results showed that Cu/CuxO@C possessed high efficiency in degrading rhodamine B (RhB), gentian violet (GV), methyl orange (MO) and Congo red (CR) dyes under UV irradiation, and the degradation effect was gradually enhanced with the increase of calcination temperature. The structural and chemical states of the materials were characterised in detail. Furthermore, the effects of experimental factors such as catalyst dose, solution pH, and inorganic anions on dye degradation efficiency were investigated. The photocatalytic mechanism study demonstrated that the primary oxygen-active substance was superoxide radical (·O2-). The electron transport hypothesis explains the effective separation of electrons and holes within a substance. The Cu/CuxO@C composite was regarded as a potential photocatalyst for dye wastewater treatment due to its high photocatalytic efficiency, reusability, and universality, offering a novel solution to environmental and energy issues.

Microalgae-fungal pellets as novel dual-bioadsorbents for dye and their practical applications in bioremediation of palm oil mill effluent

Microalgae-fungal pellets were applied as novel dual-biosorbents for dye removal compared to fungal pellets. Both pellet types effectively removed anionic dyes better than cationic dyes, with the maximum adsorbing efficiency being nearly 100 % at a wide pH range of 3–8. The adsorption isotherms of anionic Congo Red dye and Coomassie brilliant blue R-250 dye using both pellet types and their biosorption kinetics were intensively studied. Noteworthy, the maximum adsorption capacity and affinity of microalgae-fungal pellets were much higher than those of fungal pellets. Both fungal pellets were also applied in the bioremediation of palm oil mill effluent (POME). The repeated treatment of POME by replacing pellets every 12 h enhanced the percent removal of color, phenolic compounds, and COD up to 90.97 ± 0.36 %, 70.71 ± 0.90 % and 56.55 ± 1.98 %, respectively. This study has demonstrated the promising potential for addressing dye removal and bioremediation of colored-industrial effluent in a sustainable and economically viable manner.

Synthesis of high surface area mesoporous ZnAl2O4 with excellent photocatalytic activity for the photodegradation of Congo Red dye

The large-scale release by the textile and other industries of organic dyes into water courses degrades the aquatic environment and results in serious health problems for wildlife, humans, and domestic animals. The removal of such dyes from wastewater is therefore a pressing and important challenge. The efficient photocatalytic destruction of these dyes using sunlight is an elegant and attractive potential solution. In this work, mesoporous ZnAl2O4 nanomaterials were prepared with high specific surface area, high pore volume and uniform pore size distribution using a modified sol–gel synthetic protocol. BET analysis showed that the highest surface area achieved for ZnAl2O4 reached 344 m2/g. The texture, structure and chemical composition of these materials were further studied using XRD, FTIR, TEM, EDS, CHN and XPS analysis and zeta potential measurements. Band gap energies were obtained from UV/vis spectra and showed a strong decrease as particle size decreased, shifting absorption into the visible range for the finest materials and indicating the potential to improve the efficiency of photocatalysis under solar irradiation. Photocatalytic activity was evaluated by studying the photodegradation of Congo Red dye and, for the best materials, showed that 99 % of the dye was degraded in only 30 mins. These results compared very favourably with those of previously reported studies. The degradation products of the Congo Red were further investigated using mass spectrometry and this detailed study confirmed that true photoinduced fragmentation of the dye molecule occurred rather than simple ‘photobleaching’.

Antifouling ultrafiltration membranes based on acrylic fibers waste/nanochitosan for Congo red and crystal violet removal

In this study, acrylic fibers waste blended with different ratios of nanochitosan (0.5%, 1%, 2% and 4%, in weight) were converted into antifouling ultrafiltration nanocomposite membranes using a phase separation technique for the remediation of Congo red (CR) and crystal violet (CV) dyes from water. The fabricated nanocomposite membranes were investigated using Fourier Transform Infrared (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The membrane hydrophilicity was estimated using contact angle measurements, which revealed that the 4% loaded nanochitosan had the highest hydrophilicity. Additionally, the water uptake, porosity, water contact angle and water flux of the nanocomposite membranes were assessed. The membrane filtration performances were explored for the removal of CR and CV as anionic and cationic dyes, respectively, at different concentrations and various applied pressures (1 bar to 4 bar). The experimental data revealed a high rejection (R) performance for CR (R≃100%) with a high water flux of about 150 L/(m2·h) to 183 L/(m2·h) for the optimized membrane with 2% nanochitosan at an applied pressure of 4 bar. The rejection for CV showed a variant rejection (70%–99%) at different dye concentrations with fluxes ranging from 93.6 L/(m2·h) to 149.5 L/(m2·h) for the same composite membrane. The composite membrane showed enhanced flux recovery after fouling by bovine serum albumin and was resistant to widespread gram-positive (Staphylococcus aureus) bacteria.Graphical abstract

Biomass-based perovskite/graphene oxide composite for the removal of organic pollutants from wastewater

Water pollution is a critical issue that affects both human health and the environment. Biomass-based LaFeO3 is prepared by the microwave-assisted method using rice straw as a cellulose source. Then LaFeO3/graphene oxide (GO) composite is prepared by ultrasonication to facilitate the perovskite-GO binding. Raman and FTIR spectra of the prepared composite identify the presence of the perovskite, biochar, cellulose and GO oxide phases and proves the surface functional groups interactions. Transmission electron microscope image shows that the GO sheets are homogeneous covered with the perovskite nanoparticles. The adsorption performance of the LaFeO3/GO composite for the removal of methylene blue (MB) and congo red (CR) dyes from aqueous solution is optimized. Adsorption follows pseudo 2nd order kinetic model and Freundlich isotherm, with maximum adsorption capacities of 319.5 and 416.7 mg/g for MB and CR, respectively. These values are higher than those reported for magnetic GO composites, indicating the excellent adsorption ability of the proposed perovskite/GO composite. A thermodynamic study shows that the adsorption of MB is exothermic, while it is endothermic for CR and combines physisorption and chemisorption characteristics for both dyes. The proposed adsorbent shows a good performance in the presence of NaCl interferent, with the possibility of regeneration and efficient successive reuse.

Sustainable solution for wastewater management: Fabrication of cost-effective β-cyclodextrin incorporated chitosan polyvinyl alcohol composite hydrogel film for the efficient adsorption of anionic congo red and tartrazine dyes

Dyes are an integral part of leather, textiles, food, and packaging materials, providing aesthetic appeal to the finished article. These industries use large amounts of water, creating wastewater with harmful, toxic, and hazardous pollutants, posing significant health and environmental risks to the public and ecological system. Therefore, to resolve this issue, a superabsorbent β-cyclodextrin incorporated chitosan polyvinyl alcohol cross-linked with citric acid composite hydrogel film (β-CD/Ch/PVA) has been developed for the effective adsorption of congo red (CR) and tartrazine dyes (TG). The Fourier-transform infrared spectroscopic (FTIR) analysis confirmed the presence of –OH, –NH2 functional groups in hydrogel film. The rough surface morphology was obtained through Field emission scanning electron microscopic (FESEM) analysis. Brunauer-Emmett-Teller (BET) method gave the surface area of hydrogel, which is 17.34 m2/g with pore diameter of 4.12 nm, indicating its mesoporous nature. Adsorption parameters like contact time, temperature, pH, initial concentration of dyes, and dosage of hydrogel have been optimized by batch adsorption studies and the Box-Behknen Design Model. In batch experiments, the hydrogel film effectiveness was confirmed, achieving high removal efficiencies of 95.38 % and 96.3 % for CR and TG dyes at pH 7 and 6, respectively. The adsorption process followed the pseudo-second-order kinetics and Langmuir model at room temperature for both dyes, and the maximum adsorption capacity was found to be 366.34 mg/g, 1436.04 mg/g for CR and TG dyes, respectively. The thermodynamic study revealed that the adsorption of dyes was spontaneous and endothermic in nature. The electrostatic interactions and hydrogen bonding between the hydrogel and dye molecules were responsible for the adsorption. This hydrogel film can be reused for 5 consecutive adsorption–desorption cycles for both dyes, maintaining upto 85 % in removal efficiency. Hence, the synthesized β-cyclodextrin incorporated chitosan polyvinyl alcohol composite hydrogel film holds great potential for the remediation of wastewater effluents and addressing environmental issues.

Assembly of Chitosan/Caragana Fibers to Construct an Underwater Superelastic 2D Layer-Supported 3D Architecture for Rapid Congo Red Removal.

Developing environmentally friendly bulk materials capable of easily and thoroughly removing trace amounts of dye pollutants from water to rapidly obtain clean water has always been a goal pursued by researchers. Herein, a green material with a 3D architecture and with strong underwater rebounding and fatigue resistance ability was prepared by means of the assembly of biopolymer chitosan (CS) and natural caraganate fibers (CKFs) under freezing conditions. The CKFs can randomly and uniformly distribute in the lamellar structure formed during the freezing process of CS and CKFs, playing a role similar to that of "steel bars" in concrete, thus providing longitudinal support for the 3D-architecture material. The 2D layers formed by CS and CKFs as the main basic units can provide the material with a higher strength. The 3D-architecture material can bear the compressive force of a weight underwater for multiple cycles, meeting the requirements for water purification. The underwater compression test shows that the 3D-architecture material can quickly rebound to its original shape after removing the stress. This 3D-architecture material can be used to purify dye-containing water. When its dosage is 3 g/L, the material can remove 99.65% of the Congo Red (CR) in a 50 mg/L dye solution. The adsorption performance of the 3D architecture adsorbent for CR removal in actual water samples (i.e., tap water, seawater) is superior than that of commercial activated carbon. Due to its porous block characteristics, this material can be used for the continuous and efficient treatment of wastewater containing trace amounts of CR dye to obtain pure clean water, meaning that it has great potential for the effective purification of dye wastewater.

Advanced chitosan-based composites for sustainable removal of Congo red from textile wastewater

The non-biodegradable Congo red (CR) dye which is widely used in textile industries has poses carcinogenic risks due to its complex reactions that may generate benzidine. Effective treatment of industrial effluent containing CR dye is imperative. This study assessed chitosan (Cs) and chitosan/fly ash (Cs/Fa) composites for biosorbing CR dye from synthetic textile wastewater. Fly ash varied in the range of (1:0.25–1:1) with chitosan to assess adsorption performance. Characterization techniques included FTIR, SEM, EDX, BET, and zeta potential analyses. Response surface methodology guided the determination of optimal variables. The study examined Cs and Cs/Fa dosage (A), time (B), and initial dye concentration (C) effects on CR removal. Incorporating fly ash substantially cut adsorption costs by 50% while enhancing dye removal up to 85% at pH 6. Improved acidic stability of chitosan (Cs/Fa 1:0.75) was notable. Chitosan (Cs) exhibited a high Congo red removal efficiency of 98% while the chitosan/fly ash (Cs/Fa) composites showed a substantial removal efficiency of 94%. Optimal conditions were 2 g L−1 of adsorbents, initial CR concentration of 40 mg L−1 for 120 min. Freundlich isotherm model best described adsorption behavior. Pseudo-second-order kinetics correlated significantly (R2 = 0.999). This study showed the potential of Cs and Cs/Fa bio-composites for effective textile wastewater treatment.

MoO3/HAp nanocomposites encapsulated in graphene oxide nanoparticle: Development of a novel ternary nanostructure and evaluation of its photocatalytic activity for the treatment of wastewater in environmental remediation

The growing problem of water contamination can be efficiently addressed using easily recoverable photocatalysts. Graphene Oxide (GO) is a well-studied photocatalyst for industrial effluent remediation, pharmaceutical degradation, and dye degradation. Its photophysical characteristics are morphology-dependent and show enhanced activity in MoO3/HAp nanocomposites. Hydrothermal synthesis of MoO3/HAp nanocomposites encapsulated in graphene formed a unique ternary nanostructure. XRD and XPS confirmed the crystalline phase and oxidation states, while FT-IR and EDAX validated atomic bonds and component dispersion. FE-SEM and HR-TEM showed a mesoporous surface and narrow size distribution. The visible-light-active MoO3/HAp/GO had a bandgap of 2.6 eV and low recombination rate. Photodegradation tests on antibiotics (Ciprofloxacin and Levofloxacin) and dyes (Congo Red and Methylene Blue) demonstrated high photocatalytic ability. Solar light achieved 98 % degradation for Ciprofloxacin, 88 % for Levofloxacin, 91 % for Congo Red, and 93 % for Methylene Blue. Post-photocatalytic analysis showed high catalyst reusability (13 % and 7 % reduction after 4 cycles for antibiotics; 13 % decrease after 5 cycles for dyes). Trapping experiments revealed that •OH and O2•- were key for antibiotic breakdown, while e− and h+ were crucial for dye degradation. This research highlights MoO3/HAp/GO's potential to eliminate persistent pollutants.

Novel wastepaper nanocellulose/chitosan‐based nanocomposite membrane for effective removal of the textile dye Congo red from aqueous solution

AbstractDevelopment of a cost‐effective and environmentally friendly method to treat dye wastewater is of utmost importance. In this experimental study, wastepaper was used as the raw material for the extraction of cellulose nanocrystals to fabricate a nanocomposite membrane with chitosan. During the extraction process, acid hydrolysis (Sulfuric acid) followed by bleaching (hydrogen peroxide) was adopted. To confirm the nano‐range, particle size analysis, and FESEM were performed, which confirmed the presence of particles in the nano‐range ranging from 313.8 to 122.1 nm and FESEM observed results showed transformation of fibrous to rod shaped nanocrystals after acid hydrolysis. After successful nanocomposite fabrication a porous sieved network of membrane was observed and after adsorption successful adhesion of dye molecules over the membrane matrix was also confirmed. FTIR data showed that during adsorption mechanism some of the prominent peaks gets disappeared suggest interaction of dye molecules onto the nanocomposite. The contact angle of 21.0° was observed for the ChNC3 nanocomposite showed super hydrophilic behavior. Tensile strength was also observed in terms of young's modulus, ultimate strength, and elongation at break. The elasticity and stiffness of a material are usually indicated by its young modulus. In AH CNCs and ChNC3, the young modulus was seen to be increasing from 195< 693, respectively. On the other hand, the ultimate strength indicates AH CNCs and ChNC3 and shows a downward trend of 1.56> 0.316, respectively. Furthermore, the potentiality of the nanocomposite membrane was analyzed for Congo red dye in synthetic wastewater prepared in the laboratory. During the batch study, various working parameters were taken such as initial dye solution (20–100 ppm), pH (1–7), contact time (10–60 min), and dosage (0.1–0.5 mg/L). To know about adsorption, Langmuir and Freundlich isotherm were analyzed it was observed that Freundlich isotherm show best fitted modeling with R2 = 0.99, and n = 1.6 showing favorability of the heterogeneous adsorption. To determine the interaction between the adsorbate and adsorbent, pseudo first order and pseudo second order kinetics models were analyzed, and it was observed that chemisorption interaction followed between the adsorbate and adsorbent. Thermodynamic parameters were analyzed, which confirmed the spontaneous and favorable adsorption mechanism. To avoid fouling problems and maintain cost effectiveness, the resulting, nanocomposite membrane was desorbed using an appropriate solvent. After 5 cycles, the desorption rate decreased from 54% to 38%. This developed nanocomposite membrane appears to be effective in effluent waste treatment because of its simple formulation approach.

Functionally graded chitosan ferrite beads for photocatalytic degradation of Eriochrome Black T and Congo red dyes

Functionally graded chitosan ferrite beads for photocatalytic degradation of Eriochrome Black T and Congo red dyes

Green Synthesis of Mn‐Doped ZnO Nanoparticles Using Ipomoea Staphylina Leaf Extract: Characterization and Application of Photocatalytic Dye Degradation, Antibacterial and Antioxidant Activity

AbstractZinc oxide nanoparticles (ZnO NPs) and manganese‐doped zinc oxide nanoparticles (Mn‐ZnO NPs) were synthesized via a cost‐effective green combustion method employing watery leaf extracts from Ipomoea Staphylina. The nanoparticles were thoroughly characterized using FT‐IR, P‐XRD, UV‐DRS, and FE‐SEM with EDX techniques. X‐ray photoelectron spectroscopy (XPS) confirmed the successful doping of Mn in ZnO NPs. Evaluation of photocatalytic efficiency revealed that ZnO NPs degraded 76 % of Congo red dye (CR), while Mn‐doped ZnO NPs exhibited a higher degradation efficiency of 92 %. The photocatalytic performance of Mn‐doped ZnO NPs surpassed that of ZnO NPs, indicating their superior photocatalytic properties. Furthermore, both ZnO and Mn‐doped ZnO NPs displayed notable antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumonia. Additionally, Mn‐doped ZnO NPs exhibited significant antioxidant activity, demonstrated by their ability to scavenge 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH⋅) free radicals. These findings suggest that biosynthesized pure and doped NPs using plant extract can be promising candidates for antibacterial and antioxidant applications in biomedical, pharmaceutical, and wastewater treatment fields.

Synthesis and Performance of ZnAl@Layered Double Hydroxide Composites with Eucheuma cottonii for Adsorption and Regeneration of Congo Red Dye

Synthesis and Performance of ZnAl@Layered Double Hydroxide Composites with Eucheuma cottonii for Adsorption and Regeneration of Congo Red Dye

Valorization of polyurethane foam waste through the decoration with nano-polyaniline for dye decontamination from polluted water.

Two polyurethane polyaniline nanocomposites have been synthesized using two in situ polymerization routes of dried and wet bases to valorize the polyurethane waste. The physical and chemical properties of polyurethane-based nanocomposites were compared using SEM, XRD, FTIR, and Zeta potential. SEM images showed that the average particle size of the dried-based composite was 56 nm, while the wet-based composite had an average size of 75 nm. The separation efficiency for methylene blue (MB) and Congo red (CR) dyes was evaluated against free polyurethane foam waste. It was evident that pure polyurethane (PPU) achieved only 4.79% and 16.71% removal for MB and CR, respectively. These dye decontamination efficiencies were enhanced after nano polyaniline decoration of polyurethane foam either through dried base polymerization (DPUP) or wet base polymerization (WPUP). WPUP composite records 11.23% and 85.99% for MB and CR removal, respectively, improved to 26.69% and 90.07% removal using DPUP composite for the respective dyes. The adsorption kinetics, isotherms, and thermodynamics were investigated. The experimental results revealed the pseudo-second-order kinetic model as the most accurately described kinetics model for both CR and MB adsorption. The Langmuir model provided the best fit for the data, with maximum adsorption capacities of 110.98 mg/g for CR and 26.86 mg/g for MB, with corresponding R-squared values of 0.9974 and 0.9608, respectively. Regeneration and reusability studies of PPU, WPUP, and DPUP showed effective reusability, with DPUP displaying the highest adsorption capacity. These results aid in creating eco-friendly and cost-efficient adsorbents for dye removal in environmental sanitation.

Screening different solid supports for Pseudomonas aeruginosa biofilm formation and determining its efficiency for decolorization and degradation of congo red.

A global water crisis is emerging due to increasing levels of contaminated water and decreasing clean water supply on Earth. This study aims to address the removal of azo dye from wastewater to enable its reuse. Recently, utilizing microorganisms has been proven to be a practical choice for the remediation of azo dyes in wastewater. Hence, in this study, we employed a preformed biofilm of Pseudomonas aeruginosa on a solid support (called substrate) to degrade azo dyes. This process offers several advantages, such as stability, substrate portability, more biofilm production in less time, and efficient utilization of enzymes for remediation. From 50 ppm of initial Congo Red concentration, 75.74% decolorization was achieved within ten h using a preformed biofilm on a coverslip. A maximum of 52.27% decolorization was achieved using biofilm during its formation after 72h of incubation. The Fourier-transform infrared (FTIR) spectroscopic analysis of Congo Red dye before and after remediation revealed a significant change in peak intensity, indicating dye degradation. Phytotoxicity studies performed by seed germination with Vigna radiata revealed that, after 5-7 days, almost 40% more seeds with longer root and shoot lengths were germinated in the presence of treated dye compared to the untreated one. This data indicated that the harmful Congo Red was successfully degraded to a non-toxic product by Pseudomonas aeruginosa biofilm grown on a glass substrate.

Heterogeneous electro-Fenton oxidation of Congo red using carboxylic group activated carbon felt cathode: Electrokinetic mechanism and performance

In this study, the carboxyl functional group (–COOH) saturated-carbon-felt (ACF) as functional cathode was prepared and used in heterogenous (Fe2+) electro-Fenton (EF) catalytic degradation of Congo red (CR) in waster. As a heterogeneous catalyst, size-controlled magnetite (Fe3O4) nanoparticles (MNPs) were applied to the surface of the ACF cathode. The selectivity of ACF toward the two-electron oxygen-reduction reaction was estimated based on the proportion of H2O2 production; it was determined as >89 %. The removal efficiency of ACF for CR dye was 94 ± 2 % over 40 min reaction time, almost double that of a pristine CF cathode (48 ± 3 %). The kinetics data fitted to a pseudo-second order (PSO) model with K2 of 8.8 × 10−4 ± 1.72 × 10−5 mol−1 cm3 min−1 (0.88 ± 0.02 M−1 min−1). The mineralization current efficiency and TOC for CR were observed as 58 ± 2 %, and 83 ± 3 %, respectively. Overall, the results insight that the system could be a viable alternative method for treating dye-contaminated water.

Synthesis and characterization of magnetic carbon dots (CDs)-based hybrid material as an adsorbent for the removal of organic dye from water

In recent years, the rapid advancement of materials science and the desire for new functions has led to an enormous demand for novel materials, which could be used in various applications. As a result, hybrid materials have gained the interest of the scientific community due to the infinite combinations of individual components, which could lead to materials with unique properties. In this study, a carbon dots (CDs)-CuFe2O4 nanohybrid material was successfully prepared through a solvothermal process and utilized as an adsorbent for the removal of Congo Red (CR) dye from aqueous environment. The nanohybrid material combines interactive surface functional groups due to CDs and high magnetic saturation due to CuFe2O4 nanoparticles, resulting in enhanced selectivity towards CR dye and easy separation after utilization with an external magnet. The as-prepared material was characterized by various techniques, including XRD, micro-Raman, FT-IR, HR-TEM/EDS, N2 porosimetry, and SQUID. Finally, its capability in the removal efficiency of CR dye was investigated at different initial CR concentrations, contact times and pH values via UV–Vis spectroscopy.

Investigate Performance of ATGF nanocomposite based on guar gum polymer for adsorption of Congo Red dye and alpha lipoic acid drug from wastewater: study kinetics and simulation

AbstractIn this study, the synthesized nanocomposite novel arginine/thiourea/guar gum/ferrite (ATGF) adsorbent was evaluated for the adsorption of alpha lipoic acid (ALA) and Congo Red (CR) from wastewater. The synthesized nanocomposite was examined by Brunauer–Emmett–Teller theory (BET), Termal gravimetric analysis (TGA), Fourier transform infrared spectrometer (FT‐IR), field emission scanning electron microscopy (FE‐SEM), X‐ray Diffraction (XRD), Vibrating sample magnetometer (VSM), and energy dispersive X‐ray (EDX). For the removal of ALA and CR from aqueous solution, the capacity of the nanocomposite was investigated by working on a series of experiments such as the effect of adsorbent dose, initial concentration, contact time, pH and temperature. The adsorption kinetics of these two pollutants were investigated using pseudo‐first‐order and pseudo‐second‐order velocity equations. The nanocomposite kinetics follow pseudo‐second‐order. Langmuir and Freundlich isotherms were investigated. The results show that the Langmuir isotherm model gives the maximum adsorption capacity of ALA as 96.93 mg g−1 and of CR as 229.34 mg g−1 on the nanocomposite. © 2024 Society of Chemical Industry.

The potential of Gd doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

The study shows that the addition of gadolinium ions has a significant impact on the structure, morphology, and adsorption properties of Ni-Co spinel ferrite that was synthesized by the sol-gel auto-combustion method. The research also indicates that the higher the Gd content, the greater the increase in the lattice parameter, which suggests that Gd3+ ions uniformly replaced the octahedral Fe3+ ions. The morphology and chemical composition of Gd-doped Ni-Co ferrites have been studied using SEM and EDS. Gd adding to the NiCoFe matrix increases the BET surface area by 50% (from 48 to 72 m2/g) and promotes the formation of mesopores with an average radius from 3.9 to 4.9nm. The pHPZC values of Gd-doped ferrites are in the range of 7.22-7.39, which means that the ferrite surface will acquire a positive charge at natural pH, so this will promote the adsorption of Congo red anionic dye through electrostatic interaction forces. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to explain the mechanism of CR adsorption on the Ni0.5Co0.5GdxFe2-xO4 adsorbent surface. The ionic-covalent parameter has been estimated to describe the surface acid-base properties. Overall, this study highlights the potential of Gd3+ doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

Effect of solvothermal reaction time on adsorption and photocatalytic activity of spinel ZnFe2O4 nanoparticles

The present investigation explored the impact of solvothermal reaction time on the adsorption properties of synthesized spinel ZnFe2O4 Nanoparticles (ZF NPs) and their photocatalytic activity for the degradation of congo red (CR) dye. The structure, morphology and chemical composition is identified for the synthesized ZF NPs. The reaction times for the solvothermal synthesis of ZF NPs were investigated at time intervals of 6 hrs and 18 hrs which are denoted as ZF-6 h and ZF-18 h respectively. The XRD confirms the formation of spinel-type ZF-6 h and ZF-18 h with crystallite size of 5.50 nm and 8.36 nm for ZF-6 h and ZF-18 h respectively. The FESEM image of ZF-6 h exhibits microspheres, whereas in ZF-18 h NPs, the microspheres undergoes deformation. TEM analysis of ZF-6 h revealed that the microspheres were consists of 8–10 nm size ZF-NPs. Raman spectroscopy and XPS studies indicates, the reaction time influence the occupancy with 64 % and 32 % of inversion of Zn2+ cations from tetrahedral to octahedral sites in ZF-6 h and ZF-18 h, respectively. The surface area of mesoporous ZF-6 h and ZF-18 h are 138.29 m2/g and 128.41 m2/g respectively as confirmed using BET and BJH techniques. The CR dye adsorption capacity of 123.73 mg/g for ZF-6 h is higher compared to ZF-18 h (99.93 mg/g). The maximum dye removal efficiency evaluated for ZF-6 h NPs and ZF-18 h NPs was 87.33 % and 73.09 % respectively upon exposure of natural sunlight. The recyclability study identifies that ZF-6 h NPs remain stable for three degradation cycles. These results indicate that reaction time in solvothermal synthesis is sensitive to the morphology and physicochemical properties of ZF NPs. The enhanced performance of such ZF NPs is attributed to the synergistic effect of adsorption followed by photocatalytic (photo-Fenton) degradation of dyes.