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Food dyes with a diverse set of colorants stimulate appetite and enhance aesthetic charm of food on table but at the same time these dyes contaminate the aquatic and biological ecosystems due to their cytotoxic and carcinogenic potentials. Herein, we report magnetite catalyzed removal of sunset yellow dye from water through catalytic degradation and ozonation. The magnetite catalyst revealed about 83% catalytic degradation and 92% catalytic ozonation performance toward sunset yellow dye at 100 and 25 min, respectively. Furthermore, the persulphate/magnetite/O3 hybrid system revealed superior performance compared to the persulphate/magnetite under identical conditions. Kinetic studies revealed that the dye degradation data followed second-order kinetics, suggesting that the dye removal process is physicochemical in nature. This study further demonstrates that the persulfate/magnetite/O3 hybrid system can efficiently decompose sunset yellow dye in aqueous solution compared to the Fenton's reagent and simple catalytic decomposition processes which is attributed to its unique structural features. [ABSTRACT FROM AUTHOR]

Cocos nucifera, commonly known as coconut is rich in coir dust (CCD) at its outer surface, which is a very significant agri waste used as biosorbent for wastewater treatment. The current work addresses use of CCD for removal of hazardous Sunset Yellow dye (SY) FCF widely used as coloring agent in food industry, from wastewater. The uptake capacity in batch and column mode is 82 mg/g and 160 mg/g respectively. Characterization study including SEM, FTIR and BET results also supported the adsorption process. The comparative analysis with other natural biosorbents showed best results of biosorption with CCD. The output was better at high pH (10) and lower concentration of dye (5 mg/L). The kinetic study suggested pseudo second order rate revealing both adsorbate-adsorbent interdependency. The presence of covalent bonding or valence forces between the interfaces, suggested chemisorption as the rate limiting mechanism with valence forces, hydrogen bonding and pi-pi stacking being the chief forces responsible in binding of the dye molecules to the surface. The isotherm supported Langmuir model with monolayer and uniform adsorption at the interfaces. The interference test confirmed slight decrease in percent adsorption with interference from chloride and sulfate as dominating ions. The techno-economic feasibility highly recommended in field application of the substitute (net profit value, 1.256 Rs/m3, input cost, 0.052 Rs/m3). The industrial sample analysis with lab to land approach justified sustainability and commercial viability of the present work. HIGHLIGHTS: Facile removal of a food dye (sunset yellow, FCF) using Coconut coir dust (CCD). Uptake capacity in batch and column mode is 82 mg/g and 160 mg/g respectively. Chemisorption as the rate limiting mechanism with valence forces, hydrogen bonding and pi-pi stacking being the chief forces. Better uptake efficiency is seen at higher pH (10) and lower concentration (5mg/L). NOVELTY STATEMENT: Indiscriminate use of dyes in multidimensional industries including food industry makes water bodies unsafe. To address the issue, we have investigated efficient removal of toxic food dye (Sunset Yellow FCF) using coconut coir dust (CCD) which is a naturally available agri waste. Current protocol demonstrates the removal of dye in batch mode encompassing several batch parameters like dose, pH, concentration and time. The uptake capacity obtained in batch mode is highly significant with percent removal of 71% (82 mg/L) which is highly appreciable for a biosorbent material. Column uptake capacity with remarkable value of 160 mg/L was calculated using Thomas model rate equation in order to explore the maximum viable efficiency to extend the research for a possible pilot-scale and field application studies. The mechanism of biosorption is governed by the surface active forces including covalent forces, hydrogen bonding and pi-pi stacking. Since several agricultural/non-agricultural biomasses are available for wastewater treatment, a comparative research analysis of the removal efficiency with three other natural bio sorbents were experimented for removal of food dye and the results showed the highest uptake for CCD than others. The current study advances the understanding of coconut coir's efficacy in dye removal by comprehensively analyzing physicochemical parameters and conducting column studies to simulate real-world applications. Additionally, it investigates ion interference and validates findings with real wastewater scenarios, enhancing the authenticity and significance of the research. Thus the process firmly stands as low-cost, environment friendly substitute, and does not generate harmful by products. The uniqueness of the work lies in the fact that it is one of the best substitute compared to the other conventional methods of treatment available with a net profit value of 1.256 Rs/m3 and operating cost of 0.052 Rs/m3.The work also meets few principles of green chemistry/engineering and serves as a sustainable protocol to a great extent. [ABSTRACT FROM AUTHOR]

Magnetic molecularly imprinted polymers (MMIPs) contain the predesigned specialized recognition capability that can be chosen to build credible functional materials, that are easy to handle and have a good degree of specificity. Hence, the given piece of work is intended to design a novel electrochemical sensor incorporating magnetite-based molecularly imprinted polymers. The building materials consisted of a cross-linker (EGDMA), reaction-initiator (AIBN), monomer (methylene succinic acid-MSA), and template molecule (Sunset Yellow-SY dye). MMIPs exhibited a diameter of 57 nm with an irregular shape due to the presence of cavities based on SEM analysis. XRD patterns exhibited crystallinity, as well as amorphous peaks that are attributed to polymeric and non-polymeric frameworks of MMIPs. The crystallite size of the MMIPs from XRD analysis was found to be 16.28 nm based on the Debye-Scherrer's equation. Meanwhile, the FTIR bands showed the synthesis of MMIPs using monomer and methylene succinic acid. The sorption data at the optimized operating conditions (pH 2, sorbent dosage 3 mg, time 18 min) showed the highest sorption capacity of 40 mg/g. The obtained data best fitted to the Langmuir sorption isotherm and followed the pseudo-second-order kinetics. The magneto-sensors were applied for ultrasensitive, rapid, and simple sensing of SY dye. The electrochemical experiments were run at the operating condition range of (scan rate 10–50 mV/s, tads 0–120 s, pH 5–9, potential range 1–1.5 V for CV and 1–1.3 V for SWAdASV). The linear range of detection was set to 1.51 × 10−6 M to 1.51 × 10−6 M posing LOD and LOQ values of 8.6242 × 10−5 M and 0.0002874 M, respectively. The regression analysis value for the calibration was found to be 0.950. Additionally, high adsorption efficiency, selectivity, reusability, and strong structural stability of the magneto-sensors showed potential use for SY detection in real samples. These characteristics make MMIPs a viable electrochemical substrate for the detection of chemical contaminants in the environment and in health-related products. [ABSTRACT FROM AUTHOR]

This manuscript studies the electrical conductivity of the natural organic compound sunset yellow (SY) dye. This dye shows good conductivity, which encourages us to further analyze the AC and DC conduction mechanism of a dye-based device. This dye was characterized by using x-ray diffraction and showed that SY dye has a high degree of crystallinity. The optical bandgap was characterized by the absorption spectroscopy measurement and it was found to be 2.34 eV. The DC electrical conductivity was measured with an impedance spectrometer from the temperature range 303 K (30°C) to 373 K (100°C) with 4 V bias voltage. The well-known Arrhenius diagram was drawn from the conductivity versus temperature plot to find the activation energy. The activation energy and the conductivity were measured to be 0.466 eV and 1.01 × 10 - 8 Ω - m - 1 for the low-temperature region and 0.683 eV and 6.18 × 10 - 8 Ω - m - 1 , respectively, for high-temperature regions. AC conductivity was also measured in the temperature range of 303 K (30°C) to 373 K (100°C) with a frequency variation range of 500 Hz to 100 kHz. The AC conductivity falls below DC conductivity in higher temperature regions. The value of activation energy for the AC field decreases with increasing frequency. The influence of the applied frequency on the conduction mechanism, which made hopping conduction the dominant mechanism, can be linked to this phenomenon. The correlated barrier hopping model (CBH) is evidence for the reduction of the activation energy in the AC electric field. The polaron binding energy is found to be 2.52 × 10 - 19 eV. We found an increase in density of the localized state around both sides of the Fermi level with the increase in temperature which increased the electrical conductivity. [ABSTRACT FROM AUTHOR]

Herein, we describe the growth and morphology of well-defined dyed crystals of KH2PO4 (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.

Magnetic molecularly imprinted polymers (MMIPs) contain the predesigned specialized recognition capability that can be chosen to build credible functional materials, that are easy to handle and have a good degree of specificity. Hence, the given piece of work is intended to design a novel electrochemical sensor incorporating magnetite-based molecularly imprinted polymers. The building materials consisted of a cross-linker (EGDMA), reaction-initiator (AIBN), monomer (methylene succinic acid-MSA), and template molecule (Sunset Yellow-SY dye). MMIPs exhibited a diameter of 57 nm with an irregular shape due to the presence of cavities based on SEM analysis. XRD patterns exhibited crystallinity, as well as amorphous peaks that are attributed to polymeric and non-polymeric frameworks of MMIPs. The crystallite size of the MMIPs from XRD analysis was found to be 16.28 nm based on the Debye-Scherrer’s equation. Meanwhile, the FTIR bands showed the synthesis of MMIPs using monomer and methylene succinic acid. The sorption data at the optimized operating conditions (pH 2, sorbent dosage 3 mg, time 18 min) showed the highest sorption capacity of 40 mg/g. The obtained data best fitted to the Langmuir sorption isotherm and followed the pseudo-second-order kinetics. The magneto-sensors were applied for ultrasensitive, rapid, and simple sensing of SY dye. The electrochemical experiments were run at the operating condition range of (scan rate 10–50 mV/s, tads 0–120 s, pH 5–9, potential range 1–1.5 V for CV and 1–1.3 V for SWAdASV). The linear range of detection was set to 1.51 × 10−6 M to 1.51 × 10−6 M posing LOD and LOQ values of 8.6242 × 10−5 M and 0.0002874 M, respectively. The regression analysis value for the calibration was found to be 0.950. Additionally, high adsorption efficiency, selectivity, reusability, and strong structural stability of the magneto-sensors showed potential use for SY detection in real samples. These characteristics make MMIPs a viable electrochemical substrate for the detection of chemical contaminants in the environment and in health-related products.

Molecular imprinted polymers (MIPs) were developed by carrying out the cocktail solution of Template ((Salata, 2004)-Gingerol), monomer, crosslinker, and Ag 2 S Quantum Dots (QDs) by ex-situ dissolved in an appropriate solvent, resulting in an efficient crosslinked polymer composite. Degradation of Alizarin red S (ARS) dye and yellowish sunset (SY) azo dye under visible light irradiation was reported first time by the introduction of prepared MIPs composite. In this research, the result shows efficient photocatalyt activity of Ag 2 S-MIPs composite for the degradation of AR and SY dye with degradation% (80%) and (84%) in the aqueous wastewater. The degradation efficiency of the Ag 2 S-MIPs composite and the Ag 2 S QD associated with non-imprinted polymers (NIPs) (i.e. Ag 2 S-NIPs composite) were calculated by using different parameters such as catalyst dose, pH value, optimum time and concentration variation and the observations are evocative. Moreover, the density functional theory (DFT) approach was also used to analyze the structural, stability/energetics, and electronic features of the organic-inorganic hybrid composites of the Ag 2 S QD with the MIPs based on (Salata, 2004)-gingerol extract. The proposed QD and MIPs (EGDMA and (Salata, 2004)-Gingerol) composite model has been detected to be the most stable because it shows the largest binding energy (BE) among the three chosen composite models. It was found out that imprinted polymers were superior in enhancing the degradation of dyes when compared to non imprinted polymers. Introducing MIPs into the valence band accelerates the catalysis properties to stabilize newly fashioned excitons that are basically generated as a result of light excitation in presence of Ag 2 S Quantum Dots (QDs) and molecular imprinted polymer (MIPs). Motivation behind this work is to address the challenges related to environmental pollution causing by organic dyes. These toxins are known to cause diverse symptoms (e.g., skin irritation, eye infection, respiratory disorders, and even cancer) once exposed through ingestion and inhalation. Through incorporation of Ag 2 S QD into MIP,the purpose of this research is to enhance the selectivity, specificity and photocatalytic activity for dyes and that work holds a potential towards environmental remediation by developing a cost effective and sustainable method for controlling pollution in water. • Synthesis of Molecular Imprinted Polymer (MIPs) by using Ag2S Quantum Dots (QD) and (Salata, 2004)-Gingerol. • MIPs had a stronger response in Visible source of radiation attributed to QD-MIPs. • MIPs has high photocatalytic activity against multi-mode dyes test. • The OH, O2 − and H + are main reactive species during Ag2S photodegrading the AR and SY dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and characterization of La/Ag-MOF@CS. • Adsorption studies of food dye Sunset yellow. • The adsorbents exhibited good reusability for eight adsorption/desorption cycles. • Adsorption fit with pseudo-second-order kinetics and Langmuir isotherm model. • Optimization the adsorption results using Box–Behnken Design. In this work, the adsorbent Sunset yellow (SSY) dye, a hazardous food colorant, was to be removed from aqueous solutions using lanthanum/silver bimetal-organic frameworks (La/Ag-MOF) encapsulated onto chitosan (La/Ag-MOF@CS). According to the findings, La/Ag-MOF@CS is a successful adsorbent for removing SSY dye from water. Numerous tests, such as FT-IR, PXRD, SEM, TEM, XPS, and BET analysis, studies of the material's characteristics were carried out. A substantial pore volume of 1.683 cm3/g and a high surface area of 842 m2/g were found in the data, suggesting the possibility of a high adsorption capacity. The study of surface charge showed that a positive charge below the point of zero charge (pH 6) and a negative charge above it had an impact on the adsorption behavior. The maximal SSY dye adsorption onto La/Ag-MOF@CS was found to reach 443.53 mg.g−1. Pseudo-second-order kinetic models were used to clarify the reaction's kinetics, and the Langmuir isotherm model, demonstrated a chemisorption process. The adsorption process utilizing the adsorbent La/Ag-MOF@CS is anticipated to have endothermic and spontaneous nature. The synthetic La/Ag-MOF@CS adsorbent showed exceptional flexibility and cyclability, successfully completing up to eight adsorption–desorption cycles. In order to maximize the adsorption results, the Box-Behnken Design was utilized, demonstrating how La/Ag-MOF@CS may be applied to address real-world wastewater treatment challenges in a sustainable and useful way. [ABSTRACT FROM AUTHOR]

In this study, the removal of sunset yellow dye from aqueous solutions using orange peel powder (OPP) as an agricultural waste and modified by co-precipitating it with Fe3O4 magnetic nanoparticles (MNP-OPP) as adsorbents by a batch system was investigated. The effects of some important physical and chemical parameters such as the initial dye concentration, sorbent dosage, exposure time, temperature and pH, on the sorption of selected dye by introduced adsorbents were investigated. Optimum conditions for the removal of dye were determined. Among the different parameters investigated, it was found that the pH of the solution has the most pronounced effect on the sorption capacity of OPP and MNP-OPP. The experimental data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm models. The results indicate that the Freundlich and the Langmuir models provide the best correlation for SY-OPP and SY-MNP-OPP systems, respectively. The results indicated that orange peel modified with Fe3O4 nanoparticles is suitable as adsorbent material for adsorption of sunset yellow dye from aqueous solution.

Herein, we describe the growth and morphology of well-defined dyed crystals of KH 2 PO 4 (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping. [ABSTRACT FROM AUTHOR]

This manuscript focuses on the investigation of the effect of titanium dioxide nanoparticles doping on the electrical conductivity of Nano-cubical Sunset Yellow Dye. The successful preparation of the composite was confirmed through XRD analysis, and EDX analysis verified the composite's composition. DC conductivity measurements revealed two conduction mechanisms with activation energies of 0.683 eV and 0.466 eV for the dye without NPs at low and high-temperature regions, respectively, and 0.532 eV and 0.351 eV for the same regions in the presence of NPs. AC conductivity analysis showed single polaron hopping as the dominant charge conduction mechanism for both devices. The device with the dye-NP composite exhibited lower activation energy and improved conductivity compared to the dye-only device. The composite also displayed a higher density of localized states, and by incorporation of NPs reduced the hopping length, contributing to the enhanced conductivity of the composite device. [Display omitted] [ABSTRACT FROM AUTHOR]

Polypyrrole, polyaniline nanoparticles and their nanocomposites were prepared using microemulsion polymerization method. For the synthesis of polypyrrole and polyaniline nanoparticles sodium dodecyl sulfate as a surfactant for two reasons was used; to the creation of a micro reactor vessel and to improve the physical properties of polymers such as stability, solubility in organic solvents, conductivity, and processability. These nanoparticles were dedoped through 20% NaOH solution. The removal of sunset yellow and congo red dyes was carried out using both doped and dedoped species and nanocomposites at room temperature and under ultrasound irradiation. Also, the effect of adsorbent dosage, initial pH, effects of contact time on adsorption and ultrasonic power as experimental parameters on the removal of the sunset yellow and congo red dyes was investigated. It was found that all of the premade species including multiwall carbon nanotubes, carboxylate-multiwall carbon nanotubes, polypyrrole, polyaniline, polypyrrole/multiwall carbon nanotubes and polyaniline/multiwall carbon nanotubes can be used for removal of anionic dyes such as sunset yellow and congo red from water solutions. The highest removal efficiency for sunset yellow dye (∼99%) was achieved at 0.007 g of polypyrrole/multiwall carbon nanotubes nanocomposite, at pH = 2, at ambient temperature and at ultrasonic irradiation power 500 W and for congo red dye the highest removal efficiency (∼98%) was achieved at 0.01 g of polypyrrole/multiwall carbon nanotubes nanocomposite, at pH = 2, at ambient temperature and at ultrasonic irradiation power 500 W. The polypyrrole/multiwall carbon nanotubes and the polyaniline/multiwall carbon nanotubes adsorbents, the recovery achieved more than 80% with the proportion of 55:45 from acetone: H 2 O. The strong adsorption capacity of polypyrrole/multi-walled carbon nanotubes and the polyaniline/multiwall carbon nanotubes nanocomposites prepared with ammonium per sulfate as initiator can be attributed to the π-π electron donor-acceptor interaction and electrostatic attraction. The nanoadsorbents multiwall carbon nanotubes, carboxylate-multi-walled carbon, polypyrrole/multiwall carbon nanotubes and the polyaniline/multiwall carbon nanotubes produced with ammonium per sulfate as initiator was used to removing azo dyes from H 2 O through efficient microscale filtration and can be scaled up for commercial and industrial applications. [ABSTRACT FROM AUTHOR]

The purpose of our work is to identify the bioactive compounds of bark and leaves extract from Ailanthus excelsa Roxb. and to explore its effectiveness against synthetic food dye. The presence of primary and secondary metabolites was confirmed by carrying out phytochemicals analysis. With the prior knowledge accessible on the indispensable secondary metabolites holding antioxidant and cytotoxicity activity, the quantitative screening of total phenolic and flavonoid content in methanolic and aqueous extract of bark and leaves from Ailanthus excelsa were done. Comparatively, a higher value of flavonoid (161 ± 0.3 μg/mg) and phenolic acid content (152.4 ± 0.14 μg/mg) was found in bark extract. By FTIR analysis, the characteristic peak was obtained at 1581.63 and 1598.99 cm − 1 confirmed the presence of functional groups associated to flavonoids and other phenolic groups respectively. In bark extract, 81% of DPPH inhibition was observed when compared to ascorbic acid (standard) 92% of free radical scavenging activity. Bark extract from Ailanthus excelsa exhibited 71% cytotoxicity against HeLa cell line (cervical cancer). In examining the toxicity level of crude extracts with red blood cells (RBC), the bark extract was showed a very less (2.8%) haemolytic activity. They also showed maximum zone of inhibition in antibacterial activity i.e. 13 ± 0.5 mm against Escherichia coli culture. At a concentration of 10 mg/mL of crude extract from A. excelsa , 55% degradation of sunset yellow dye was observed. It concludes that, the compounds present in the A. excelsa , especially the bark extract showed better photocatalytic, haemolytic, antioxidant, cytotoxicity and antibacterial activity when compared to leaves extract. [ABSTRACT FROM AUTHOR]

Sunset Yellow E110 is one of the famous synthetic food dyes, which belongs to the family of azo dyes and widely used in food industry as additives and nutrient sources. Two highly sensitive and simple spectrophotometric methods are developed for determination of Sunset Yellow E110 in some commercial food samples. The first method is based on redox reaction of Sunset Yellow with copper (II) followed by complex formation. Results indicated the formation of 1:1 metal-dye complex at pH 9.0. The second one is based on its oxidation by alkaline KMnO to green manganate species. The two reactions are monitored spectrophotometrically at maximum absorbance 350 and 610 nm for methods I and II, respectively. Variables are carefully studied, and the conditions are optimized. Under the optimized experimental conditions, Beer's Law was obeyed in the concentration ranges 9.05-67.87 and 13.57-72.38 μg ml for the two methods, respectively. The apparent molar absorptivities, Sandell's sensitivity, and detection and quantification limits are calculated. Matrix effects are also investigated. The proposed methods are successfully applied for the determination of Sunset Yellow dye in commercial food products. The concentration level of the dye is found to be within the safe recommended limits. [ABSTRACT FROM AUTHOR]

Alligator weed activated carbon (AWAC) was prepared by phosphoric acid activation. The AWAC features a high surface area (736.3 m2/g) and has an abundant array of microvoids and mesopores with an average pore size of 4.05 nm. A 0.8 g/L dose of AWAC adsorbed about 96% of sunset yellow dye (SYD) at a concentration of 150 mg/L. The maximum adsorption was approximately 271 mg/g at 308 K. Orthogonal experiments for the %Removal and amount of SYD adsorbed at equilibrium revealed that the optimal conditions were pH = 3, T = 298 K, initial SYD concentration = 250 mg/L, and AWAC dose = 1.2 g/L. The kinetics and equilibrium data agreed well with the pseudo-second- order model and Freundlich isotherm equation for the adsorbent. Functional groups that may increase the adsorption capacity were detected on the surface of AWAC, such as –OH, C=C and C–O–C. Electrostatic interactions are important in the adsorption process along with chemical bond formation and hydrophobic interaction. Thermodynamic analysis illustrated that the adsorption process is spontaneous and endothermic. AWAC is a promising low-cost adsorbent for the removal of SYD from aqueous effluent. [ABSTRACT FROM AUTHOR]

The adsorption of dye sunset yellow (SY) on both raw and functionalized chitosan (CTN and CTN F) was investigated using statistical physics theory. Adsorption data of SY dye on CTN and CTN-F were experimentally obtained at 298–328 K. Statistical physics modeling analysis demonstrated that the adsorption capacities at 298–328 K of both systems were similar. This theoretical evidence explained that the functionalization of the raw chitosan via 3-aminopropyltriethoxysilane did not improve the adsorbent performance. It was also concluded that the SY dye interacted via the same orientation on CTN and CTN F. The effect of the temperature on the adsorption capacity was studied and results indicated that the SY dye adsorption on CTN and CTN-F adsorbents was endothermic. Dye adsorption capacities were due to the similarity in the number of the attracted SY dye molecules per adsorption site and the density of this receptor site. The interactions between SY dye and adsorbents (CTN and CTN F) and also between SY dye molecules were understood via the calculation of adsorption energies. Physical interactions were the responsible of the dye adsorption mechanism using adsorbents CTN and CTN-F. • Adsorption of sunset yellow dye on a raw and functionalized chitosan was investigated. • Impact of adsorbent functionalization was analyzed via statistical physics calculations. • Physical interactions were responsible for the endothermic dye adsorption. [ABSTRACT FROM AUTHOR]

The release of synthetic food dyes, like Sunset yellow, into industrial effluents can cause serious environmental and health problems. Due to its aromatic structure, it is recalcitrant towards degradation into non -toxic intermediates and its removal by efficient adsorption represents a cheap and efficient method. Herein we propose the use of thermally reduced graphene oxide (TRGO) as effective Sunset yellow dye adsorbent with an adsorption maximum capacity comparable with other sophisticated, chemically synthesized carbon-based nanomaterials. The reduced graphene oxide and the Sunset yellow adsorbed one were characterized by FT-IR, XPS and XRD spectroscopy, N 2 adsorption-desorption isotherm and TGA analysis. BET surface area reduced from 274.1 m2/g (for TRGO) to 39.9 m2/g (for TRGO-SY) showing that Sunset Yellow molecules occupied the corresponding active sites while the number of sheets resulted from the XRD spectra – from 3 to 8 in TRGO to 5 in TRGO-SY indicates the ordered intercalations in the graphene structure. The adsorption isotherm experimental data were better fitted with the Langmuir model than the Freundlich model, with the maximum adsorption capacity of the SY dye monolayer of 243.3 mg/g at pH = 6.0 and 189.0 mg/g from synthetic wastewater. The kinetic study revealed a perfect fit following the Pseudo-second order model with an equilibrium achieved within 30 min. The lack of adsorption on the starting graphene oxide is indicative for π-π interactions between the adsorbate and adsorbent. Image 1 • Green and easily available adsorbent for anionic synthetic dyes. • Thermally reduced graphene oxide-an effective Sunset yellow dye adsorbent. • Perfect fit following the Pseudo-second order model. • Very rapid rate of SY removal, reaching the equilibrium after 30 min. [ABSTRACT FROM AUTHOR]