Hazardous Azo Dye Research Articles

Fluoro-Hydroxyapatite/Chitosan composites as an eco-friendly adsorbent for Direct Red 23 dye removal: Optimization through Response Surface Methodology

This study presents the development of an innovative and eco-friendly Fluoro-Hydroxyapatite/Chitosan (FHAP-CS) adsorbent for removing Direct Red 23 (DR23) dye from aqueous solutions. Synthesized via the sol-gel method by incorporating fluoride (F) and chitosan (CS) into hydroxyapatite, FHAP-CS was characterized using FTIR, XRD, SEM, TGA, and N2 adsorption/desorption to evaluate its structural, surface, and morphological properties. The results demonstrated that FHAP-CS exhibited enhanced particle definition, reduced particle size, increased surface area, and superior adsorption capacity compared to pure HAP, HAP-CS, and FHAP.The adsorption of DR23 dye onto FHAP-CS was optimized using Central Composite Design and Response Surface Methodology. The results demonstrated that the quadratic regression models were statistically significant (R² = 0.99) and can accurately predict adsorption behavior. The monolayer adsorption mechanism of DR23 dye onto FHAP-CS was confirmed by fitting the batch adsorption data to the Langmuir isotherm model, and the process followed pseudo-second-order kinetic models. Under optimal conditions: a [DR23]0= 350 mg/L, pH of 5.11, FHAP-CS dose of 1.60 g/L, agitation speed of 240 rpm, and contact time of 120 min the adsorption capacity reached approximately 152.36 mg g-1. These findings suggest that FHAP-CS is an effective and cost-efficient adsorbent for removing hazardous azo dyes from wastewater.

Ingenious development of bandgap engineered MIL-101(Fe) core-shell supported on SnO2/ZnO heterojunction and its photocatalytic activity towards azo dye degradation: Process optimization and mechanistic insight

Water pollution is a pressing global concern, exacerbated by industrial effluents containing hazardous azo-dyes such as Trypan blue (TB) and Methyl orange (MO), which contaminate water bodies and threaten ecosystems. The scarcity of pure water intensifies the urgency to develop effective remediation strategies to tackle the toxic dye pollutants. In the present work, an attempt has been made to fabricate and utilize a novel ternary MOF-based SnO2/ZnO@MIL-101(Fe) photocatalyst for the removal of TB and MO dyes from an aqueous medium. The photocatalyst was characterized using various analytical techniques, like XRD, FTIR, UV–vis DRS, PL, SEM, TEM, and XPS, which provide insights into the composites’ crystal structure, morphology, and optical properties, which are crucial for understanding their photocatalytic behavior. The photocatalytic performance of the heterojunction was investigated under various reaction parameters such as catalyst dosage, initial concentration of dyes, and light irradiation time. The results demonstrated the superior performance of the SnO2/ZnO@MIL-101(Fe) composites in degrading the mono-azo and di-azo dyes under visible light irradiation via a photo-fenton process. The maximum degradation efficiency of 97.44 % and 98.8 % were obtained for TB and MO within 30 and 55 min, respectively. Furthermore, the change in the total organic carbon (TOC) was monitored to verify the degree of mineralization of the azo dyes. The extremely high dye degradation activity and TOC removal can be attributed to the formation of a suitable heterojunction interface between the components of the photocatalyst, leading to effective charge carrier transport and the generation of active radicals. Finally, based on the radical scavenging experiments, ESR, and VB-XPS analysis, a plausible mechanism for the photodegradation process was derived. This research contributes to the advancement of sustainable water treatment technologies by providing insights into the design, fabrication, and utilization of novel composites for efficient remediation of dye-contaminated wastewater.

Efficacy of electrospun PAN/g-C3N4 nanofibers as a photocatalyst for the deterioration of hazardous azo dyes

PAN and PAN/g-C3N4 nanofibers were fabricated using the electrospinning technique. Meanwhile, g-C3N4 nanoflakes were synthesized using the thermal decomposition technique. The challenge of reusing powder catalysts was ultimately surmounted due to the use of dispersed g-C3N4. Characterization of the as-fabricated PAN/g-C3N4 NFs was performed employing wide-angle powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–Vis spectrophotometry (UV–Vis), thermogravimetry analysis (TGA), N2 adsorption-desorption isotherms (BET) and X-ray photoelectron spectrometer (XPS). According to morphological studies, g-C3N4 nanoflakes get uniformly decorated over PAN fibers with a greater specific surface area and smaller band gap than g-C3N4, exhibiting maximal uniformity in dispersion. Under solar light irradiation, PAN (71%), g-C3N4 (84%), and PAN/g-C3N4 nanofibers (95%) showed excellent photocatalytic performances for the degradation of Methyl orange dye (MO) in 120 min with 95% degradation. Similarly, PAN (61%), g-C3N4 (72%), and PAN/g-C3N4 nanofibers (91%) showed photocatalytic performances for the degradation of Congo red dye (CR) in 160 min with 91% degradation. This effective degradation was due to a shift in band gap with high porosity of PAN/g-C3N4 NFs compared to pure materials such as PAN and g-C3N4.

Utilization of Azadirachta Indica Latex for Synthesis of Silver Nanoparticles its Application in Photocatalytic Degradation of Methylene Blue Dye

The use of extract from indigenous plant species for the synthesis of metallic nanoparticles has significant importance as they have a capacity to act as potential reducing, capping and stabilizing agent. In this research, latex of Azadirachta indica (Neem) was selected for green synthesis of silver nanoparticles (AgNPs). Maximum absorbance was achieved at 425 nm (λmax) for AgNPs. FTIR vibrational peaks of AgNPs were observed at 3462, 2933, 1732, 1658, 1458, 1381, 1244, and 1028 and near 600 cm -1. Moreover, Atomic Force Microscopy (AFM) showed that the synthesized AgNPs were face-centered cuboid, spherical, hexahedral, and pentagonal structures ranging in size between 7.15-71.5nm. XRD analysis shows that most of the nanoparticles have spherical crystalline structure. Photocatalytic degradation of hazardous azo dye; Methylene blue dye (MB) was performed in the presence of synthesized AgNPs as catalysts under UV-induced photocatalytic degradation. The degradation efficiency after 180 minutes of reaction time was 82 % which proposes its potential to use as environmental pollutant eradicators in the treatment of textile industries wastewater.

Rapid catalytic reduction of environmentally toxic azo dye pollutant by Prussian blue analogue nanocatalyst.

The release of toxic azo dyes pollutants in the environment from different industries represents a public health concern and a serious environmental problem. Therefore, the conversion of hazardous methyl orange (MO) azo dye to environmentally benign products is a critical demand. In this work, an eco-friendly Prussian blue analogue (PBA) was synthesized and its catalytic activity toward the reduction of MO was investigated. The PBA copper(ii) hexacyanocobaltate(III) (Cu3[Co(CN)6]2) was synthesized by a facile inexpensive chemical coprecipitation method without using hazardous solvents. The nanocatalyst was characterized using XPS, Raman, FTIR spectroscopy, and XRD. The chemical reduction of MO using NaBH4 and the PBA as nanocatalyst was monitored by UV-VIS spectroscopy. Toxic MO was completely reduced in 105 s with a rate constant (k) 0.0386 s-1 using only 10 μg of the PBA nanocatalyst. Besides the powerful catalytic activity, the nanocatalyst also showed excellent stability and recyclability for ten consecutive cycles, with no significant decrease in the catalytic performance. Therefore, the proposed PBA is a promising, stable, cost-effective, and eco-friendly nanocatalyst for the rapid elimination of hazardous azo dyes.

Fabrication of core–shell beads, hollow capsules, and AuNP-embedded catalytic beads from an ultrasmall peptide hydrogel

Hydrogel beads have emerged as a new class of soft materials that infuse the noble properties of macro-dimensional hydrogels in tiny, easily operable, and robust droplets. Usually, polymeric hydrogels are used in the production of hydrogel beads due to their high structural rigidity and durability, and low molecular weight hydrogel beads are relatively uncommon. Herein, we employed an ultra-short peptide (Pyrene-Lys-Cys, PyKC) based low molecular weight injectable hydrogel, that remains insoluble in bulk solvents, to create stable hydrogel beads using a simple extrusion technique. To enhance durability and applicability, the beads are coated with a polymeric shell, resulting in a core–shell configuration. The shell of the core–shell beads can be modified through a variety of organic conjugation reactions. Also, the core (hydrogel) can be sacrificed using DMSO, resulting in the formation of hollow organic capsules. Furthermore, the core–shell beads enabled the in-situ synthesis and stabilization of gold nanoparticles on the bead surface. The gold-loaded beads demonstrated remarkable catalytic efficiency in the reduction of p-nitrophenol and hazardous azo dyes. In a nutshell, the extremely modular and customizable nature of the PyKC-based core–shell hydrogel bead may allow it to function as a unified platform for multifaceted applications.

Investigation of the Photocatalytic Activity of Electrospun and Surface-Modified PAN/α-FeOOH Nanofibers for the Degradation of Hazardous Azo Dyes.

Decoration of α-FeOOH nanorods over PAN nanofibers was performed using the electrospinning technique. The as-designed decorated nanofibers were characterized using various techniques such as wide-angle powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectrophotometry (UV-vis), thermogravimetry analysis (TGA), N2 adsorption-desorption isotherm (BET), and X-ray photoelectron spectrometry (XPS). α-FeOOH NRs were decorated uniformly over PAN fibers, as observed from its morphological investigation, which shows novelty. 1D α-FeOOH nanorods with PAN nanofibers have not been studied for photocatalytic characteristics. No literature mentions that α-FeOOH nanorods coated in PAN NFs act as photocatalysts to degrade hazardous azo dyes. α-FeOOH nanorods on PAN NFs inhibit aggregation and increase dye binding, boosting photocatalytic performance. PAN/α-FeOOH NFs have a maximal specific surface area with a reduced bandgap than α-FeOOH NRs. PAN/α-FeOOH nanofibers showed excellent photocatalytic activity for the degradation of Trypan blue (TB) (120 min, 99.7%) and Eriochrome black T (EBT) dyes (160 min, 97.6%), respectively, under solar light irradiation. PAN/α-FeOOH NFs have the potential to be used in the degradation of azo dyes and the treatment of wastewater due to their low energy requirements and versatility.

Synergistic effects of noble metal doping and nanoengineering on boosting the azo dye mineralization activity of nickel oxide

The present investigation involves the synthesis of a nanostructured ceramic material, namely silver-doped nickel oxide (Ni1−x(Ag)xO), by a wet-chemical method supported by a surfactant. The physicochemical, electrical, textural, compositional, and optical characteristics of nickel oxide and its Ag-doped variant were assessed using several analytical procedures, comprising X-ray diffraction, FTIR, current-voltage testing, scanning electron microscopy (SEM), elemental (EDX), and photoluminescence analysis. These materials were then used as a photocatalyst under W-light exposure to examine the annihilation of a hazardous azo dye (crystal violet). Under optimal circumstances (pH = 9, photocatalyst dosage = 0.01 g/80 mL, dye concentration = 15 ppm, reaction time = 80 min), Ag-doped nickel oxide nanocatalyst displayed more potent dye annihilation activity than pure nanocatalyst. The Ag-doped nickel oxide nanocatalyst exhibits a significant degradation efficiency of 94.44% towards Crystal violet (CV) dye, and it lost just 7.5% efficacy after four consecutive reusability tests. The degradation process used hydroxyl radicals as principal active species and followed a pseudo-1st order kinetic model with a rate constant (k) value of 0.024 min−1. Incorporating silver in the crystal structure of nickel oxide as a dopant effectively reduces the band gap energy, therefore facilitating the absorption of a broader range of light wavelengths. Additionally, the presence of silver helps to mitigate electron-hole recombination, a process that may hinder the efficiency of photocatalysis. Using nanotechnology in combination with silver doping improves the surface properties of the photocatalyst. These approaches work together to boost the photocatalytic activity of nickel oxide. This study proposes a novel methodology to enhance the photocatalytic capabilities of a basic ceramic material, making it a promising candidate for environmental remediation.

Joint Multi-Optimization of an Extremophilic Microbial Bioanode for Mitigation of Mixed Hazardous Azo Dyes in Textile Synthetic Wastewater

Bioelectrochemical systems (BESs), rather than physicochemical processes, are used for wastewater remediation, electricity production, and zero carbon dioxide emission. Textile effluents contain organic and inorganic compounds that can fuel BESs. The main goal of this study was to understand the interplay between the anode material, its surface area, the potential applied to the working electrode (WE), and the concentration of the co-substrate, and how these factors lead to the formation of highly efficient thermohalophilic bioanodes (THB) retrieved from Chott El Djerid (SCD) hypersaline sediment for the treatment of synthetic textile wastewater. To this end, twenty-seven bioanode formation experiments were designed using a Box-Behnken matrix and response surface methodology to understand concomitant interactions. All experiments were conducted in electrochemical reactors of final volume 750 mL inoculated with 80% of enrichment medium containing three azo dyes at a concentration of 300 ppm and 20% of biocatalyst microbial SCD source, at 45 °C. The optimal levels were predicted using NemrodW software as carbon felt (CF) anode material, 6 cm2 anode surface, 7 g/L glucose concentration, and −0.1 V applied potential. These theoretical results were experimentally validated, using maximum current output of 5.23 ± 0.30 A/m2, decolorization rate of 100%, and a chemical oxygen demand (COD) removal rate of 96 ± 1%. Illumina Miseq results revealed that bacterial community harbored the bioanode was dominated at phylum level by Firmicutes (67.1%). At the species level, the biofilm was mainly colonized by Orenia metallireducens species (59.5%). Obtained findings show a promising application of THB in the degradation of recalcitrant molecules as well as for the energy recovery.

Lychaete pellucida as a novel biosorbent for the biodegradation of hazardous azo dyes

The majority of textile wastes are made up of toxic dyes. Additionally, because these compounds are soluble, wastewater may include significant concentrations. In this work, the green alga Lychaete pellucida is used for the bioremoval of four common azo dyes, Reactive Blue 4 (RB4), Reactive Red 120 (RR120), Reactive Brilliant Yellow 3G (RBY3G), and Reactive Green12 (RG12), with the application of two models of sorption isotherms, Langmuir and Freundlich. The spectrophotometer method was used to identify optimum conditions (temperature, pH, dye concentrations, algal biomass, and contact time) to remove these dyes onto dry freshwater macroalgae. The optimum pH for L. pellucida was 8. The optimum biosorbent amount is 2 g/L. Then, the best-removed dye concentration was 5 mg/L, the optimum contact duration was 120 min, and the optimum temperature was 25 °C. Under optimum conditions, the percent of dye removal was about 95% for all used azo dyes. This is the first report on the use of Lychaete pellucida for the efficient biodegradation of hazardous azo dyes.

Photocatalytic degradation of food colorant azo dyes using iron and fluorine co-doped TiO[formula omitted]/SiO[formula omitted] nanocomposites: Semi-pilot study cum density functional theory calculations

Remediation of hazardous azo dyes such as Allura Red, Sunset Yellow, and Tartrazine, from the wastewater of the food industries is of great importance. Here, we have used a custom-designed semi-pilot fixed-bed photoreactor to degrade these three important azo dyes via a photocatalytic approach using Fluorine and iron co-doped titanium dioxide/silica nanocomposite (F-Fe-TiO 2/SiO 2). The nanocomposite photocatalyst was synthesized by the sol–gel coupled dipping method and was characterized using several techniques. The as-developed photocatalyst showed a bandgap of 2.92 eV, allowing us to use it under both visible light and solar light irradiation. Additionally, density functional theory calculations were used to gain more insight into how the dopants (F and Fe) affect the bandgap of the photocatalyst. The photo-degradation process was optimized by investigating the effects of pH, the concentration of the dyes, and the flow rate of the wastewater solution. The results of this study suggest that the combination of the as-designed photocatalyst and photoreactor can significantly reduce the total organic carbon (TOC) content in the model wastewater including three azo dyes and therefore, have a great potential to be scaled up for industrial wastewater treatment via a green approach.

Facile synthesis and physicochemical characterization of κ-Carrageenan-silver-bentonite based nanocatalytic platform for efficient degradation of anionic azo dyes

Water pollution due to textile industry effluents is a global concern that warrants versatile research solutions for degrading them, and for a sustainable environment. In the present work, by using the imperative role of nanotechnology, a facile one-pot synthesis has been devised to generate κ-carrageenan capped silver nanocatalyst (CSNC), and was immobilized on 2D bentonite (BT) sheets to generate nanocatalytic platform (BTCSNC) for the degradation of anionic azo dyes. The nanocomposite(s) were physicochemically characterized using UV–Vis, DLS, TEM, FESEM, PXRD, ATR-FTIR, TGA, BET and XPS etc., to obtain insights into the nanocomposite composition, structure, stability, morphology and mechanism of interaction. The obtained CNSC are monodispersed, spherical with a size of 4 ± 2 nm, and were stabilized by the functional groups (-OH, COO‾, and SO3‾) of κ-Crg. The broadening of peak corresponding to basal plane (001) of BT montmorillonite in PXRD spectra established its exfoliation upon addition of CSNC. XPS and ATR-FTIR data evidenced the absence of covalent interactions between CSNC and BT. The catalytic efficiency of CSNC and BTCSNC composites were compared for the degradation of methyl orange (MO) and congo red (CR). The reaction followed a pseudo first order kinetics, and immobilization of CSNC on BT resulted in a 3–4 fold enhancement in degradation rates. The rates achieved for the degradation kinetics are: MO degradation within 14 s (Ka 9.86 ± 2.00 min−1), and CR degradation within 120 s (Ka of 1.24 ± 0.13 min−1). Further, a degradation mechanism has been proposed by analyzing the products identified through LC-MS. The reusability studies of the BTCSNC evidenced the complete activity of the nanocatalytic platform for six cycles, and gravitational separation method for catalyst recycling. In a nutshell, the current study provided an environmentally friendly, sizable, and sustainable nano catalytic platform” for the remediation of industrial wastewater contaminated with hazardous azo dyes”.

Application of systematic evidence mapping to identify available data on the potential human health hazards of selected market-relevant azo dyes

BackgroundAzo dyes are used in textiles and leather clothing. Human exposure can occur from wearing textiles containing azo dyes. Since the body’s enzymes and microbiome can cleave azo dyes, potentially resulting in mutagenic or carcinogenic metabolites, there is also an indirect health concern on the parent compounds. While several hazardous azo dyes are banned, many more are still in use that have not been evaluated systematically for potential health concerns. This systematic evidence map (SEM) aims to compile and categorize the available toxicological evidence on the potential human health risks of a set of 30 market-relevant azo dyes. MethodsPeer-reviewed and gray literature was searched and over 20,000 studies were identified. These were filtered using Sciome Workbench for Interactive computer-Facilitated Text-mining (SWIFT) Review software with evidence stream tags (human, animal, in vitro) yielding 12,800 unique records. SWIFT Active (a machine-learning software) further facilitated title/abstract screening. DistillerSR software was used for additional title/abstract, full-text screening, and data extraction. Results187 studies were identified that met populations, exposures, comparators, and outcomes (PECO) criteria. From this pool, 54 human, 78 animal, and 61 genotoxicity studies were extracted into a literature inventory. Toxicological evidence was abundant for three azo dyes (also used as food additives) and sparse for five of the remaining 27 compounds. Complementary search in ECHA’s REACH database for summaries of unpublished study reports revealed evidence for all 30 dyes. The question arose of how this information can be fed into an SEM process. Proper identification of prioritized dyes from various databases (including U.S. EPA’s CompTox Chemicals Dashboard) turned out to be a challenge. Evidence compiled by this SEM project can be evaluated for subsequent use in problem formulation efforts to inform potential regulatory needs and prepare for a more efficient and targeted evaluation in the future for human health assessments.

Synthesis and Characterization of Graphene Oxide and Chitosan Decorated Nano Zerovalent Iron for Efficient Adsorptive Removal of Hazardous Azo Dye from Aqueous Medium

The main aim of the study was to synthesize nano zerovalent iron (NZVI) modified with graphene oxide (GO) and chitosan (CS) in the form of a magnetic ternary nanocomposite. Three ternary nanocomposites i.e. GO-CS-NZVI, GO-NZVI-CS and CS-NZVI-GO were synthesized to further understand the possible binding tendencies among these components in the final ternary composite. These ternary composites were characterized by FTIR, SEM and EDS techniques to understand the effect of mutual interaction of the three components during synthesis on the overall structure and morphology of the ternary composite. Furthermore, these ternary nanocomposites were employed in the removal of Congo red (an anionic, carcinogenic, azo dye) and also a mixture of dyes Congo red and Rhodamine B (a cationic, carcinogenic dye). A maximum of 98% removal of Congo red and 98.7% removal from the mixture of dyes was observed with ternary nanocomposite GO-CS-NZVI within 30 min. Equilibrium adsorption efficiency (qe) was calculated to be 48.15 and 79 mg/g for Congo red and mixture of dyes (Congo red & Rhodamine B), respectively. A comparative analysis of bare NZVI with these ternary nanocomposites was also conducted to further understand the effect of modification of NZVI with graphene oxide and chitosan on the structure, morphology and its dye removal efficiency.

Fabrication of Novel Nanohybrid Material for the Removal of Azo Dyes from Wastewater

This study attempted to harness the dual benefit of adsorption and photocatalytic degradation for efficiently removing a model anionic azo dye, Orange G, from an aqueous solution. For this purpose, a series of bifunctional nanohybrids containing different proportions of naturally occurring biopolymer chitosan and ternary photocatalyst made of kaolinite, TiO2, and ZnO were prepared through the dissolution of chitosan in acid and subsequent deposition on ternary photocatalyst. The characterization through Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrum (EDS) have confirmed the successful fabrication of nanohybrids from TiO2 and chitosan. The adsorptive separation of Orange G from the aqueous solution and subsequent degradation under solar irradiation was thoroughly studied by recording the λmax value of dye in the ultraviolet–visible (UV-Vis) spectrophotometer at various operating conditions of pH, dye concentration, contact time, and compositional variation. The nanohybrid (TP0.75CS0.25) fabricated from 75% ternary photocatalyst (w/w) and 25% chitosan (w/w) removed 97.4% Orange G within 110 min at pH 2.5 and 10 mg/L dye concentration. The relative contribution of chitosan and ternary composite on dye removal was understood by comparing the experimental results in the dark and sunlight. Recyclability experiments showed the suitability of the nanohybrid for long-term repeated applications. Equilibrium experimental data showed a better correlation with the Langmuir isotherm and pseudo-second-order kinetic model. The rapid and nearly complete removal capacity, long-term reusability, and simple fabrication technique make this novel nanohybrid a promising advanced material for removing hazardous azo dyes from industrial effluents.

An integrative study for efficient removal of hazardous azo dye using microbe-immobilized cow dung biochar in a continuous packed bed reactor

The effluents from the industries such astextile, paper and pulp, cosmetic and pharmaceutical sector consists of huge load of hazardous azo dye, which enters the water bodies and affects the environment and human health. In this work dye degrading Lysinibacillus sp.was immobilized on the surface of cow dung biochar for treatment of wastewater containing Malachite green (MG), Auramine yellow (AY) and Methyl orange (MO) azo dye in a fabricated continuous packed bed reactor (CPBR). The adsorption isotherm study suggested that Langmuir isotherm showcased comparatively a better model than Freundlich. The dye removal efficiencies were calculated as 52.360 ± 0.209 and 78.241 ± 0.211% for the free and immobilized bacterial cells in a batch study. The dye decolorization process was further investigated by performing the statistical optimization of parameters through Central composite design model-based response surface methodology (CCD-RSM) and artificial neural network (ANN). The dye removal efficiency by CCD-RSM and ANN model was found to be 98.420 and 97.320%, respectively. Prediction made by the developed models suited well with the test runs. This study suggested that RSM and ANN can be considered as effective tools to model and predict trace pollutants removal by CD biochar.

Sudan I monitoring as a hazardous azo dye using an electroanalytical tool amplified with NiO/SWCNTs-ionic liquid catalysts

Sudan I is an azo dye that causes cancer and is not allowed to be used in food products. The current study focused on the design and manufacture of an electrochemical sensor modified with NiO/SWCNTs, as a nano-catalyst, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (1H3MIbTMI), as an ionic liquid binder, to monitor Sudan I as azo additive dyes in various food samples. The modified carbon paste electrode (CPE/NiO/SWCNTs/1H3MIbTMI) offered superior electrochemical performance metrics as an analytical sensor to detect trace levels of Sudan I within the concentration range of 1.0 nM–250 μM. The limit of detection was determined as 0.3 nM by the differential pulse voltammetric (DPV) technique. The proposed CPE/NiO/SWCNTs/1H3MIbTMI can be put forward to be employed as an analytical instrument for sensing Sudan I in various culinary sauces, including chili, tomato, and strawberry sauces. The obtained recovery range was determined as 97.6%–104.35%. These findings demonstrated the effectiveness of the newly created material and its potential for usage as a novel analytical instrument.

Outstanding performance of electro-Fenton/ultra-violet/ultra-sound assisted-persulfate process for the complete degradation of hazardous pollutants in contaminated water

This work focuses on the degradation of the hazardous azo dye Naphthol Blue Black (NBB) utilizing an innovative approach combining electro-Fenton (EF), ultra-violet (UV), and ultra-sound (US) processes while varying the operating parameters (concentration of iron and dye, pH, current intensity). Under the optimum experimental conditions, an excellent degradation efficiency of the NBB dye is achieved after 60 min, i.e., 98%, 95%, and 65% for EF, UV, and US processes, respectively. The addition of persulfate significantly improves the efficiency and accelerates the kinetics of the NBB degradation. Combining all processes assisted with persulfate achieved 99% NBB degradation within a very short contact time of 2 min and 98% reduction in COD after 55 min. The as-obtained outstanding performance associated with the synergistic effects of EF/US/UV alongside the addition of persulfate can be adopted to degrade other hazardous substances.

Naked‐eye colorimetric and optical assay of heavy metals based on nano‐architectured prototype of organically functionalized mesoporous titania grafted with 4‐chloro‐2‐(4′‐methyl‐benzothiazol‐2′‐ylazo)‐phenol

Heavy metals are extremely toxic, causing harm to aquatic and human life. Thus, this study focused on developing simple, colorimetric, and low‐cost optical sensors for detection of metal ions with high selectivity and sensitivity. Here, a novel benzothiazole azo‐dye, namely, 4‐chloro‐2‐(4′‐methyl‐benzothiazol‐2′‐ylazo)‐phenol (CMBTAP) was synthesized and characterized by Fourier transform infrared spectroscopy (FT‐IR), 1H‐nuclear magnetic resonance (NMR), 13C‐NMR, and mass spectroscopic techniques. This azo‐dye has been anchored into the amino‐functionalized mesoporous TiO2 which synthesized using pluornic123 and cetyltrimethylammonium bromide as templates to yield CMBTAP‐M‐TiO2 (1) and CMBTAP‐M‐TiO2 (2), respectively. The designed nanosensors were characterized by FT‐IR, transmission electron microscopy, nitrogen adsorption–desorption isotherms, X‐ray diffraction, and thermogravimetric analyses. The colorimetric and optical sensing behavior of CMBTAP and its nanosensor analogs toward different metal ions like Ba2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, Hg2+, and Al3+ were explored using naked‐eye observations, steady‐state absorption, and emission techniques. Significant changes in colors, the absorption and emission spectra were observed. The action of these nanosensors is reversible where on adding ethylenediaminetetraacetic acid to the formed complexes, the original absorption and emission spectra of the free sensors are restored, demonstrating that the chelation process is reversible. For CMBTAP and the nanosensors, the binding constants of the complexes formed with the used metal ions, and limit of detection (LOD) were calculated. In comparison with CMBTAP, the results revealed that the nanosensors exhibited a stronger binding affinity, selectivity, sensitivity, and lower LODs for the studied metal ions, implying that the sensing efficiency of CMBTAP is improved after loading onto the nanostructured TiO2. Thus, we have successfully converted the hazardous azo dye into an environmentally safe optical sensor for detection of toxic metal ions in wastewater with high sensitivity.

Accurate data prediction by fuzzy inference model for adsorption of hazardous azo dyes by novel algal doped magnetic chitosan bionanocomposite

A bionanocomposite comprising of magnetic chitosan doped with algae isolated from native habitat was fabricated and utilized as an efficient adsorbent for the removal of hazardous azo dyes, namely, Direct Red 31 (DR31) and Direct Red 28 (DR28). The algal doped magnetic chitosan (Alg@mCS) was comprehensively characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction analysis (XRD), and Brunauer-Emmett-Teller (BET). On the sorption of dyes, the influence of various process variables such as pH, adsorbent dosage, contact time, temperature, and initial dyes concentration were addressed. The adsorbent demonstrated maximal removal of DR31 and DR28 at pH 5 and 3, respectively. The maximum adsorption capacity of DR31 and DR28 was observed at Alg@mCS dose of 0.6 g L−1 and 7 g L−1 in 10 and 20 min, respectively. The Redlich Peterson isotherm model was shown to be appropriate for dye adsorption, indicating monolayer coverage of the dyes on the adsorbent surface (R2 > 0.99). The adsorption process followed pseudo-second-order kinetics (R2 > 0.99). Based on 320 experimental datasets from batch studies and interpolated data, adaptive neuro-fuzzy inference system (ANFIS) models were utilized to estimate dye elimination (percent). A number of parameters were calculated to validate the model's applicability. The Alg@mCS was proven to be a useful adsorbent for eliminating toxic and harmful azo dyes from aqueous solutions.