Application In Dye Removal Research Articles

Eu2CuO4 nanostructures: A simple co-precipitation pathway, characterization, and promising photocatalytic application for dye removal under visible light

Contamination of water has become an international concern, and finding efficient and sustainable methods to eliminate harmful pollutants is crucial for ensuring that clean and safe water resources are available. A promising approach in this regard is photocatalysis, which uses light energy to initiate chemical reactions that break down organic contaminants into harmless byproducts. This study presents a nanophotocatalyst based on europium copper oxide (Eu2CuO4) for the elimination of hazardous pollutants. The fabrication of Eu2CuO4 nanostructures was achieved through a simple and rapid co-precipitation process. According to diffuse reflectance spectroscopy (DRS), Eu2CuO4 has an optical bandgap of 1.56 eV, making it suitable for use in visible light. A variety of techniques were used to characterize Eu2CuO4 nanostructures, including XRD, FESEM, FTIR, VSM, HRTEM, BET, EDS, and LC-MS. In order to maximize effectiveness, several variables were considered, such as the amount of Eu2CuO4 used, the concentration of toxic pollutants, and the pH of the solution. It was found that Eu2CuO4 was quite effective in degrading various organic pollutants, particularly methyl orange (MO) of water. Using 50 mg of Eu2CuO4 in the presence of 20 ppm MO and exposing it to visible radiation for 100 min resulted in 94.9 % of MO being destroyed. A further analysis revealed that hydroxyl radicals (•OH) and holes (h+) played a dominant role in pollutant photodegradation. In light of this finding, Eu2CuO4 may serve as a valuable candidate for developing new materials that are capable of successfully removing contaminants from water.

Green synthesis of Dextrin‐graft‐poly(allyl amine‐co‐methacrylic acid)/reduced graphene oxide composite and its application for dye and pesticide removal from the aqueous medium

AbstractA Dextrin‐graft‐poly(allyl amine‐co‐methacrylic acid)/reduced graphene oxide (DEXTGP/RGO) is synthesized through the grafting of a combination of allyl amine (AAM) and methacrylic acid (MAA) monomers onto the dextrin polysaccharide backbone by using the free radical copolymerization technique in an aqueous medium, with potassium peroxydisulfate serving as the initiator followed by the partial reduction of graphene oxide (GO). Various characterization techniques including FTIR, 1H/13C NMR, XRD, FESEM, EDAX, and BET analysis are utilized to characterize both the synthesized DEXTGP/RGO composite and graft copolymer. Investigations are conducted on multiple operational variables, including adsorption kinetics, isotherms, and thermodynamic parameters, for the adsorption of both MB and PL. Both intra‐particle diffusion kinetic model and pseudo‐second‐order kinetics are observed to follow for the adsorption of MB, while the Langmuir isotherm model provided a good fit for the equilibrium data. In contrast, the adsorption of PL displayed solely pseudo‐second‐order kinetics, while the equilibrium data shows good agreement with both the Langmuir and Dubinin‐Radushkevich isotherm models. Maximum adsorption capacity ( ) of the RGO composite is found to be 932.56 mg/g for MB and 311.63 mg/g for PL. The thermodynamic analysis revealed that the adsorption of dye and pesticide onto the RGO composite is a spontaneous process.

Synthesis of pumice and medical waste incinerator fly ash based phosphate geopolymers for methylene blue dye adsorption: co-valorization, parameters and mechanism

Synthesis of pumice-based geopolymer composites, GP-0, GP-10, GP-20 and GP-30, substituted with fractions of 0, 10, 20 and 30% by weight of medical waste incinerator fly ash (MWI-FA), respectively and application for dye removal.

The Effect of Silver Nanoparticles/Titanium Dioxide in Poly(acrylic acid-co-acrylamide)-Modified, Deproteinized, Natural Rubber Composites on Dye Removal.

This work aims to enhance the dye-removal performance of prepared poly(acrylic acid-co-acrylamide)-modified, deproteinized, natural rubber ((PAA-co-PAM)-DPNR) through incorporation with silver nanoparticles/titanium dioxide. The (PAA-co-PAM)-DPNR was prepared by emulsion-graft copolymerization with a grafting efficiency of 10.20 ± 2.33 to 54.26 ± 1.55%. The composites based on (PAA-co-PAM)-DPNR comprising silver nanoparticles and titanium dioxide ((PAA-co-PAM)-DPNR/Ag-TiO2) were then prepared by latex compounding using the fixed concentration of AgNO3 (0.5 phr) and varying concentrations of TiO2 at 1.0, 2.5, and 5.0 phr. The formation of silver nanoparticles was obtained by heat and applied pressure. The composites had a porous morphology as they allowed water to diffuse in their structure, allowing the high specific area to interact with dye molecules. The incorporation of silver nanoparticles/titanium dioxide improved the compressive modulus from 1.015 ± 0.062 to 2.283 ± 0.043 KPa. The (PAA-co-PAM)-DPNR/Ag-TiO2 composite with 5.0 phr of TiO2 had a maximum adsorption capacity of 206.42 mg/g, which increased by 2.02-fold compared to (PAA-co-PAM)-DPNR. The behavior of dye removal was assessed with the pseudo-second-order kinetic model and Langmuir isotherm adsorption model. These composites can maintain their removal efficiency above 90% for up to five cycles. Thus, these composites could have the potential for dye-removal applications.

Potential Indonesian Rice Husk for Wastewater Treatment Agricultural Waste Preparation and Dye Removal Application

This study used a novel method to transform rice husk waste into a highly effective and specific adsorbent for several dyes, including malachite green, direct yellow, congo red, and rodhamine B. The rice husk was analyzed and used for the purpose of eliminating these colors from water-based solutions. The adsorbent exhibited excellent heat stability, and the sample retained the functional groups of lignin. The parameters pertaining to kinetics were also examined. The adsorption exhibited a time-dependent rise and reached its peak after 100 minutes. In the kinetics tests, the most suitable model to characterize the behavior was found to be the pseudo-first order, with a regression value near to one. The rice husk shown significant potential and selectivity in the removal of malachite green and rodhamine B, particularly in the presence of direct yellow and congo red, from aqueous solutions.

Graphene-Enhanced Methacrylated Alginate Gel Films for Sustainable Dye Removal in Water Purification.

Self-standing nanocomposite films were prepared by three-dimensional UV-induced radical copolymerization of methacrylated alginate (MALG) with acrylic acid (AA) and reinforced with graphene oxide (GO) to improve both mechanical strength and dye adsorption capacity in wastewater decontamination operations. Dynamic mechanical-thermal analysis revealed variations in storage modulus: the higher the GO content, the higher the storage modulus (E') values. Also, the higher the temperature (associated with a lower and lower water content of films), the larger values of E' for the films of the same composition (E'(25 °C) = 676.6-1538.7 MPa; E'(100 °C) = 886.9-2066.6 MPa), providing insights into the compatibility between GO and the MALG/AA matrix, as well as, assessing the improvement in the nanocomposite's final mechanical properties. These crosslinked films in a dry state exhibited rapid water uptake and relatively short drying times (ca. 30 min at room temperature for the MALG/AA/GO composites) resulting from the swelling-drying studies and water contact angle measurements. The efficacy of methylene blue removal from water assessed via UV-VIS spectrometry revealed excellent results, expressed as an adsorption yield of 70-80% and 85-98% after 30 h and 258 h, respectively, of immersion time of films into an MB aqueous solution of 12.5 mg/L (as the contaminated water model). The reusability of the same films was evaluated by consecutive extraction processes of MB from the composite membranes when the content of desorbed dye was also spectrophotometrically monitored and conducted in acidic conditions (HCl aqueous solutions of pH 2). Overall, the introduction of GO in the developed self-standing MALG/AA nanocomposite films exhibited enhanced mechanical properties and increased efficiency for dye removal applications. Their great reutilization potential was highlighted by low drying times and a good ability to release the dye initially adsorbed. Thus, the prepared films could be suitable materials for sustainable and effective water treatment technologies.

Fixed-Bed Adsorption of an Azo Dye (Methyl Orange) onto Chemically and Thermally Regenerated Activated Carbons

In this study, the effectiveness of the recovery method for spent granular activated carbon (SGAC) for application in dye removal was evaluated. A comparative study of the textural (porosity), compositional, surface functionality, and adsorption performance of chemically (CAR400) and thermally regenerated activated carbons (CAR700 and CAR900) was conducted for the elimination of methyl orange (MO) dye by using a fixed-bed system. The results were compared with those of commercial activated carbon (CA). The influence of parameters such as the initial dye concentration, the flow rate, the internal diameter of the column, and the bed height was evaluated. Adsorption data were modelled by using the Thomas, Adams–Bohart, and Yoon–Nelson equations. The CAR400 activated carbon had a microporosity (1045 mg/g) comparable to that of the reference commercial (CA) activated carbon (1052 mg/g) but exhibited the least adsorption capacity. The breakthrough curves were best described by the Thomas model more than the Bohart–Adams and Yoon–Nelson’s models. Thomas’s model depicted that an increase in column diameter resulted in a decrease in the maximum adsorption capacity (qo). The CAR900 material exhibited the highest adsorption capacity (15.72 mg/g) comparable to that of commercial activated carbon, CA (16.90 mg/g). These results show that the physical/thermal regeneration of spent granular activated carbons (SGAC) is more suitable for the valorization of these waste materials for water purification applications.

Biogenic ZnO/CuO/Fe2O3 Nanocomposite: A Groundbreaking Approach for Enhanced Degradation Capabilities and Reusability in Dye Removal Applications

We present the successful synthesis of a biogenic ZnO/CuO/Fe2O3 nanocomposite using an aqueous leaf extract of Ocimum Basilicum L. The confirmation of biosynthesis was achieved through UV–Visible spectrophotometry (UV–Vis), which provided evidence of ZnO/CuO/Fe2O3 NC formation. Scanning Electron Microscopy further confirmed the nanoscale size of the NC, measuring at 65 nm. X-Ray Diffraction analysis revealed a hexagonal structure for ZnO and a monoclinic structure for CuO. The successful synthesis of the environmentally friendly ZnO/CuO/Fe2O3 NC was further verified using Fourier transformed infrared (FT-IR) spectroscopy, which identified the functional groups present in the composite. Notably, the ZnO/CuO/Fe2O3 NC demonstrated exceptional degradation capabilities for toluidine blue (TB), p-toluidine (PT), and m-Toluidine (MT), with degradation rates of 99%, 99.1%, and 99.7%, respectively, within a reaction time of 120 min. The reaction kinetics followed a pseudo-first order model, with rate constant (k) values of 0.0314 min−1 and 0.0189 min−1 for TB and PT, respectively. This high rate of dye degradation can be attributed to the low band gap of the NC, which was determined to be 1.44 eV for the indirect bandgap. Furthermore, the nanocomposite exhibited excellent degradation reusability, maintaining a high degradation rate in each cycle.

Facile synthesis of Mn3O4–ZnO composite for photocatalytic dye removal and capacitive applications

Researchers are focusing on the designing a material's chemistry with novel composition to enhance the efficiency of wastewater treatment and energy storage applications with sufficient stability. Current manuscript presents a detailed comparative study of Mn3O4–ZnO composite for photocatalytic and capacitive applications. The composite samples were prepared through chemical precipitation route to understand the effect of concentration of each component (Mn3O4 and ZnO) on structural and optical characteristics. X-ray diffraction (XRD) and Fourier Transformed Infra-Red spectroscopy (FTIR) confirmed the successful development of both phases with structural modifications in composite sample. Optical absorbance spectroscopy supported the structural amendments with variation in optical band gap (2.71–2.92 eV). Further, the equal concentration (1:1) of Mn3O4 and ZnO exhibited ∼98 % removal of methylene blue dye under UV–visible lamp (Hg lamp) with highest rate of removal (0.037 min−1) among all the prepared samples. Here, the degradation efficiency has been reduced significantly (to 30 %) in alkaline dye solution at pH = 11. Further, the capacitive measurements revealed the highest total capacitance (0.97 F/g) among all the mixed compositions.

Synthesis of oxidized carboxymethyl cellulose-chitosan and its composite films with SiC and SiC@SiO2 nanoparticles for methylene blue dye adsorption

The cationic methylene blue (MB) dye sequestration was studied by using oxidized carboxymethyl cellulose-chitosan (OCMC-CS) and its composite films with silicon carbide (OCMC-CS-SiC), and silica-coated SiC nanoparticles (OCMC-CS-SiC@SiO2). The resulting composite films were characterized through various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS). The dye adsorption properties of the synthesized composite films were comprehensively investigated in batch experiments and the effect of parameters such as contact time, initial dye concentration, catalyst dosages, temperature, and pH were systematically evaluated. The results indicated that the film's adsorption efficiency was increased by increasing the contact time, catalyst amount, and temperature, and with a decreased initial concentration of dye solution. The adsorption efficiency was highest at neutral pH. The experimental results demonstrated that OCMC-CS films have high dye adsorption capabilities as compared to OCMC-CS-SiC, and OCMC-CS-SiC@SiO2. Additionally, the desorption investigation suggested that the adsorbents are successfully regenerated. Overall, this study contributes to the development of sustainable and effective adsorbent materials for dye removal applications. These films present a promising and environmentally friendly approach to mitigate dye pollution from aqueous systems.

Hierarchical Porous Activated Carbon from Wheat Bran Agro-Waste: Applications in Carbon Dioxide Capture, Dye Removal, Oxygen and Hydrogen Evolution Reactions.

This work reports an efficient method for facile synthesis of hierarchically porous carbon (WB-AC) utilizing wheat bran waste. Obtained carbon showed 2.47 mmol g-1 CO2 capture capacity with good CO2 /N2 selectivity and 27.35 to 29.90 kJ mol-1 isosteric heat of adsorption. Rapid removal of MO dye was observed with a capacity of ~555 mg g-1 . Moreover, WB-AC demonstrated a good OER activity with 0.35 V low overpotential at 5 mA cm-2 and a Tafel slope of 115 mV dec-1 . It also exhibited high electrocatalytic HER activity with 57 mV overpotential at 10 mA cm-2 and a Tafel slope of 82.6 mV dec-1 . The large SSA (757 m2 g-1 ) and total pore volume (0.3696 cm3 g-1 ) result from N2 activation contributing to selective CO2 uptake, high and rapid dye removal capacity and superior electrochemical activity (OER/HER), suggesting the use of WB-AC as cost effective adsorbent and metal free electrocatalyst.

Ultrasmall Gold Nanospheres Engineered with Nisin Pectin Bioconjugate: A Multifunctional Solution for Dye Removal, Detoxification, and Antimicrobial Applications

Ultrasmall Gold Nanospheres Engineered with Nisin Pectin Bioconjugate: A Multifunctional Solution for Dye Removal, Detoxification, and Antimicrobial Applications

Green surface modification of polyvinyl alcohol fibers and its application for dye removal using Doehlert experimental design

The use of eco-friendly techniques and green reagents to modify the properties of synthetic biopolymers is attracting an increasing attention. In this work, L-cysteine (CYS) modified polyvinyl alcohol electrospun fibers (PVA-CYS) were prepared using an easy, fast, and green technique. The incorporation of CYS as a source of nitrogen and sulfur shows an important enhancement in dye removal efficiency compared to polyvinyl alcohol fibers (PVA). The successful grafting of CYS on PVA was proved by FTIR, elemental analysis, SEM, AFM and TGA analysis. Doehlert experimental design was used to optimize the adsorption process of crystal violet (CV) on PVA and PVA-CYS. The two models show good correlations between experimental and predicted responses, with coefficients of determination equal to 0.946 and 0.976, for PVA and PVA-CYS, respectively. The most influencing parameter was the pH for CV removal by adsorption on PVA. However, this parameter affects less the dye removal using PVA-CYS. The modified fibers exhibit excellent adsorption ability toward CV, and the maximum adsorption capacity reaches 197 mg g−1 at neutral pH. An application of this process on a doped real wastewater demonstrates its efficacity and selectivity with a percentage of removal up to 85%.

Paper sludge saccharification for batch and fed-batch production of bacterial cellulose decorated with magnetite for dye decolorization by experimental design

Cellulosic wastes represent a great environmental challenge, with potential conversion to product-added value through microbial fermentation. Currently, bacterial cellulose (BC) is considered a promising natural polymer for multiple applications. However, the high production cost challenges its wide application. Hence, the current study evaluated the applicability of paper sludge as a cost-effective medium for both cellulases and BC production. The local isolate Streptomyces rochei revealed the highest cellulase production titer (about 3 U/mL) at optimized conditions. For BC production, batch and fed-batch fermentation strategies were evaluated using enzymatically hydrolyzed paper sludge. The results asserted the advantage of fed-batch fermentation for advanced BC production (3.10 g/L) over batch fermentation (1.06 g/L) under the same cultivation conditions. The developed BC membranes were characterized through different instrumental analyses, which revealed an increase in fiber diameters and crystallinity under fed-batch fermentation. Furthermore, BC/magnetite (BC/Fe3O4) nanocomposite was developed by an in-situ approach. The newly developed composite was evaluated for dye removal applications, using methyl orange (MO) as a model. The dye removal conditions were optimized through Box Behnken design (BBD), which indicated maximal MO removal (83.5%) at pH 3.0 and BC/Fe3O4 concentration of 0.1 mg/dL after 60 min. Therefore, the current study asserts the good applicability of enzymatically hydrolyzed paper sludge as a medium for cost-effective BC production and the high capacity of BC/magnetite nanocomposite for MO decolorization. The study paves the way for the cost-effective implementation of BC/magnetite nanocomposite for dye removal.Graphical

Heterogeneous MIL-88A on MIL-88B hybrid: A promising eco-friendly hybrid from green synthesis to dual application (Adsorption and photocatalysis) in tetracycline and dyes removal

Herein, the green synthesis of heterogeneous dual functional MIL88A-on-MIL88B hybrids (MIL: Materials InstituteLavoisier) with different amounts of MIL88B compared to MIL88A, including 1:2, 1:1, and 2:1, has been carried out. The photocatalytic degradation of tetracycline and adsorption of tetracycline and dyes (Direct Red 80, Direct Red 23, Acid Blue 92, and Reactive Orange 14) were investigated. Although the ratio of MIL88A-on-MIL88B (1:1) hybrid displayed the best activity, there is a slight difference in the photocatalytic performance of the other mass ratios studied. The result revealed that after 70 min of forming MIL88A on MIL88B, the best pollutant removal performance is obtained. During the limited synthesis time, the lopsided growth of MIL88A on the MIL88B surface limits the formation of sufficient functional groups and new pores between MIL88B as the substrate and MIL88A, which are effective and decisive in the performance. In the photocatalytic studies, the synthesized composite had good compatibility with the zero-order kinetics, and hydroxyl radicals were recognized as the most active species in the photocatalytic reaction. In the adsorption process, the MIL88A-on-MIL88A composite followed pseudo-second-order kinetics and the Langmuir isotherm. Besides, mechanisms such as π-π interaction/stacking, hydrogen bonding, and π-metal interaction were proposed for the pollutant adsorption process.

Heterophase Grain Boundary‐Rich Superparamagnetic Iron Oxides/Carbon Composite for Cationic Crystal Violet and Anionic Congo Red Dye Removal

Iron oxide‐based nanostructures receive significant attention as efficient adsorbents for organic dye removal applications. Herein, iron oxide/carbon composite with well‐defined heterophase grain boundaries is synthesized by a simple precipitation method and followed by calcination. The local structure, spin dynamics, and magnetic properties of heterophase iron oxides/carbon composite are thoroughly investigated to explore its cationic and anionic dye removal capability. To validate the effectivity of the presence of heterogeneous grain boundaries, iron oxide/carbon nanocomposite with homogeneous grain boundaries is also examined. For an initial dye concentration of 50 mg L−1, pH 7, and adsorbent dose of 0.2 g L−1, the hetero‐IOCC exhibits a removal capacity of 71.63 and 140.19 mg g−1 for the cationic crystal violet and the anionic Congo red dyes, respectively. These values are significantly greater than those exhibited by as‐synthesized imidazole‐capped superparamagnetic α‐Fe2O3, 48.15 and 53.19 mg g−1; and homophase iron oxide/carbon nanocomposite, 12.51 and 17.95 mg g−1, respectively. Adsorption isotherms and kinetic studies indicate that the Langmuir isotherm model is found to be an appropriate model following the Elovich kinetic model. A detailed dye adsorption investigation on the pH effect, thermodynamic parameters, coexisting ionic effect, and reusability is also carried out.

Bacterial nanocellulose and its application in heavy metals and dyes removal: a review.

This review discusses the application of bacterial nanocellulose (BNC) and modified BNC in treating wastewater containing heavy metals and dye contaminants. It also highlights the challenges and future perspectives of BNC and its composites. Untreated industrial effluents containing toxic heavy metals are systematically discharged into public waters. In particular, lead (Pb), copper (Cu), cadmium (Cd), nickel (Ni), zinc (Zn), and arsenic (As) are very harmful to human health and, in some cases, may lead to death. Several methods such as chemical precipitation, ion exchange, membrane filtration, coagulation, and Fenton oxidation are used to remove these heavy metals from the environment. However, these methods involve the use of numerous chemicals whilst producing high amount of toxic sludge. Meanwhile, the development of the adsorption-based technique has provided an alternative way of treating wastewater using BNC. Bacterial nanocellulose requires less energy for purification and has higher purity than plant cellulose. In general, the optimum growth parameters are crucial in BNC production. Even though native BNC can be used for the removal of heavy metals and dyes, the incorporation of other materials, such as polyethyleneimine, graphene oxide, calcium carbonate and polydopamine can improve sorption efficiencies.

Super-wetting and self-cleaning polyvinyl alcohol/sodium alginate nanofiber membrane decorated with MIL-88A(Fe) for efficient oil/water emulsion separation and dye degradation

Membrane separation is considered an effective approach to water purification. Nevertheless, membrane fouling dramatically decreases the separation efficiency and lifetime of membranes, thus limiting its further development and application. Herein, a multifunctional self-cleaning MIL-88A(Fe) decorated polyvinyl alcohol/sodium alginate (MIL-88A(Fe)@PVA-SA) nanofiber membrane was prepared by electrospinning and in-situ growth methods for the separation of oil/water emulsions and photo-Fenton degradation of dyes. The membrane possesses superhydrophilicity with a water contact angle (WCA) of 0° and superoleophobicity with underwater oil contact angle (UCA) of 161.7°, and exhibits superior separation efficiency (>99.5 %) and permeation flux (1140–2455 L/m2/h) for different oil/water emulsions. Moreover, the membrane exhibited an outstanding photo-Fenton performance under visible light, with degradation efficiencies (~99.9 %) towards methylene blue (MB) and reactive red 24 (RR24) within 90 min. Importantly, the membrane can be easily regenerated by simple rinsing and photo-Fenton self-cleaning treatment. In this study, MIL-88A(Fe)@PVA-SA nanofiber membrane has a promising application in dye removal and oil/water separation, providing a new idea to develop novel membrane materials.

Investigating the effects of polypropylene-TiO2 loading on the performance of polysulfone/polyetherimide ultrafiltration membranes for azo dye removal: Experimental and molecular dynamics simulation

This research paper delves into developing and analyzing advanced composite ultrafiltration (UF) membranes specifically tailored for water treatment and dye removal applications. The composite UF membranes were designed using a combination of polysulfone (PSF), polyetherimide (PEI), and polypropylene-80 wt% TiO2 (PPTiO2) to create the active layer, while a flat polyamide (PA) serves as the support material and is prepared via the spin/spray-coating method. Three different PPTiO2 contents were considered, including 5 wt% (M05), 10 wt% (M10), and 15 wt% (M15). The properties of these membranes were characterized using a range of techniques, including Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), contact angle measurements, mechanical testing and zeta potential. Performance evaluation involved filtering Reactive Red 120 (RR120) and Direct Blue 6 (DB6) solutions through the prepared composite membranes at 5 bar and demonstrates that the optimized membrane M15 exhibited remarkable water permeability of 82.13 L.m−2.h−1 bar−1 and maximum dye rejections of 92.82 % and 97.07 % for DB6 and RR120 respectively. Furthermore, molecular dynamics (MD) simulations were conducted to analyze the thermal and structural properties of the membranes. The simulations reveal that increasing the content of PPTiO2 reduced membrane pore size, consequently limiting dye mobility and diffusion. This study is the first-of-its-kind to explore the effect of PPTiO2 content on the membrane (PSF/PEI) properties; the optimized composite UF membrane showcases exceptional water permeability and dye rejection performance, making it a promising candidate for water treatment and dye removal applications.

Calcium oxide nanoparticles: Biosynthesis, characterization and photocatalytic activity for application in yellow tartrazine dye removal

Dyes are substances that have a high polluting potential, due to their low biodegradability and chemical stability, causing serious environmental damage when disposed of incorrectly. Yellow tartrazine (YT) dye as an environmental liability requires attention, since it causes toxic effects in fish (Danio rerio) with a potential allergic effect in humans. In this context, the present study aims to synthesize and characterize calcium oxide nanoparticles (CaO-NPs) to evaluate the photocatalytic activity for the YT photodegradation under visible irradiation. CaO-NPs were synthesized by the biosynthesis method from golden linseed (Linum usitatissimum L.) extract. Central Composite Rotational Design (CCRD 23) was used to determine the ideal condition for the photocatalytic tests. X-ray diffraction (XRD), zeta potential (ZP), physical adsorption of N2, zero charge point (pHzcp), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy by Energy Dispersive Spectroscopy (SEM-EDS), Diffuse Reflectance Spectroscopy (DRS) and Field Emission Gun – Scanning Electron Microscope (FEG-SEM) were used to the CaO-NPs characterization. Thus, CaO-NPs presented SBET = 14±0.02 m2g−1, Dp = 20.9±0.02 nm and Vp = 0.054±0.004 cm3g−1, characteristic of a mesoporous material. ATR-FTIR spectrum showed characteristic stretches of specific functional groups (–CH, –CO, C = C, Ca-O, –OH) from plant extract and metallic precursor. CaO-NPs showed pHZCP equal to 7.74, positive surface charge (+12.7 mV) and bang gap energy of 2.61 eV. FEG-SEM micrographs showed that has a small agglomeration with defined morphology, but with irregular particle size (around 48 nm), and SEM-EDS micrographs showed an elemental composition (in weight) of the 50.24% oxygen, 3.32% magnesium, 2.29% iron, 10.44% calcium, 14.07% silicon, 3.33% aluminum and 0.63% potassium. Regarding CCRD 23, the ideal condition was the pH = 7.0, [CaO-NPs] = 1.2 g/L and [YT] = 20 mg/L, with 76.2% of photodegradation and a pseudo first-order reaction specific reaction rate k = 0.089 min−1. After V cycles of CaO-NPs recycling, there was a decrease of around 22.83%, indicating a saturation of the active sites available in the nanocatalyst Therefore, CaO-NPs showed potential application for TY photodegradation to be used in wastewater treatment being an alternative nanocatalyst, meeting nanotechnology and sustainable development.