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Deoxynojirimycin (DNJ) is an α-glucosidase inhibitor with high food values. However, the complex and costly enrichment processes have greatly prevented its application. Herein, this study aimed to propose a simple and efficient enrichment process for DNJ from Morus alba L. extracts using cation exchange resins. The LSI and D113 resins were chosen due to their excellent adsorption and desorption properties. The adsorption characteristics agreed with the pseudo-first-order kinetic model and the Langmuir isotherm model. This adsorption was chemisorption, spontaneous, endothermic and entropy-driven. Furthermore, the concentration and pH of the extracts, desorption solvent, breakthrough and elution curves, sample loading and elution rate were investigated to optimize the enrichment process by resin column chromatography. The results also showed that the purity of DNJ was improved to 44.00 % with a total recovery of 78.21 % using the LSI-D113 combination strategy. This research demonstrated the industrial feasibility of DNJ enrichment using cation exchange resins.

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Fluoroquinolone antibiotics have been extensively used in clinical treatments for human and animal diseases. However, their long-term presence in the environment increases the risk of producing resistance genes and creates a potential threat to ecosystems and the health of humans and animals. Batch equilibrium experiments were utilized to investigate the adsorption and retention behavior and mechanism of the quinolone antibiotic enrofloxacin (ENR) in farmland soil in North China. The adsorption and desorption kinetics of ENR in soil were best fitted by pseudo-second-order model (R2 > 0.999). Both the adsorption and desorption processes of ENR in soil reached equilibrium in 1 h. The desorption amounts of ENR were significantly lower than the adsorption amounts, with the hysteresis coefficient (HI) being less than 0.7. The adsorption thermodynamic process of ENR followed the Linear and Freundlich models (0.965 < R2 < 0.985). Hydrophobic distribution and heterogeneous multimolecular layer adsorption were identified as critical factors in the adsorption process. The adsorption amount of ENR gradually decreased with increasing temperature and the initial concentration of ENR. The adsorption rate of ENR was above 80%, while the desorption rate remained below 15%, indicating strong retention ability. The adsorption rate of ENR in soil decreased with increasing pH, the adsorption rate reached 98.3% at pH 3.0 but only 31.5% at pH 11. The influence of coexisting ions on adsorption primarily depended on their properties, such as ion radius, ionic strength, and hydrolysis properties, and the inhibition of adsorption increased with increasing ionic strength. These findings contribute to understanding the fate and risk of veterinary antibiotics in loess soil in North China.

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The enhanced hydrothermal stability of leather, imparted by little Cr(III), has traditionally been ascribed to strong coordinate bonds. However, this explanation falls short when considering that the heat-induced shrinking of collagen fiber is predominantly driven by rupturing weak H-bonds. This study explored the stability source via adsorption thermodynamics using collagen fiber as an adsorbent. Eleven isotherm models were fitted with the equilibrium dataset. Nine of these models aptly described Cr(III) adsorption based on the physical interpretations of model parameters and error functions. The adsorption equilibrium constants from six models could be transformed into dimensionless thermodynamic equilibrium constants. Based on the higher R2 of the van't Hoff equation, thermodynamic parameters (∆G°, ∆H°, ∆S°) from the Fritz-Shluender isotherm model revealed that the adsorption process typifies endothermic and spontaneous chemisorption, emphasizing entropy increase as the primary driver of Cr(III) bonding with collagen. Thus, the release of bound H2O from collagen is identified as the stability source of collagen fiber modified by Cr(III). This research not only clarifies the selection and applicability of the isotherm model in a specific aqueous system but also identifies entropy, rather than enthalpy, as the principal stability source of Cr-leather. These insights facilitate the development of novel methods to obtain stable collagen-based material.

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The flow of graphene oxide (GO) into natural water systems can adversely affect water environments and ecosystems. In this study, the adsorption effect of calcite on GO under different conditions was studied using calcite as adsorbent. Meanwhile, characterized by a combination of microscopic experiments, including SEM, TEM, XRD, FTIR, Raman, XPS, and AFM, additional research on the performance and the mechanism of GO sorption by calcite was conducted. The findings indicated that the highest adsorption efficiency was observed at a temperature of 303 K, pH 3, a mass of 90 mg of calcite, with an initial concentration of 60 mg L-1 GO, resulting in a 95% adsorption rate. The adsorption isotherm conformed to the model of Langmuir and Temkin, and it is a heat absorption process dominated by monolayer adsorption. The thermodynamic analysis showed that the adsorption was spontaneous and heat-absorbing. The adsorption kinetics conformed to the pseudo-second-order kinetic model, and the sorption procedure is chemisorption. In conclusion, calcite has a good sorption capacity for GO, which can provide a reference for the removal of GO in the aqueous environment.

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Chaenomeles speciosa (Sweet) Nakai fruit is a good source of phenolics with many health benefits. In this work, the enrichment of C. speciosa fruit total phenolics (CSFTP) using macroporous resins was studied. NKA-Ⅱ resin was selected for enriching CSFTP due to its highest adsorption/desorption quantity. Adsorption characteristics of CSFTP on NKA-Ⅱ resin exhibited a good fit with the Langmuir isotherm model and pseudo-second order kinetics model. This adsorption was spontaneous, exothermic, and entropy-decreasing through a physisorption mechanism. The breakthrough-elution curves were studied to optimize CSFTP enrichment conditions. One-step enrichment increased CSFTP content in the extracts from 26.51 % to 78.63 %, with a recovery of 81.03 %. A UPLC-QqQ-MS/MS method in multiple reaction monitoring (MRM) mode was established and validated for the simultaneous quantification of seven phenolic compounds. This study demonstrates the feasibility of industrial enrichment of CSFTP using NKA-Ⅱ resin and proposes a reliable method for quality control of CSFTP-rich products.

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Phosphoric acid-activated biochar has been proven to be a promising adsorbent for pollutant removal in an aqueous solution. It is urgent to understand how surface adsorption and intra-particle diffusion synergistically contribute to the adsorption kinetic process of dyes. In this work, we prepared a series of PPC adsorbents (PPCs) from red-pulp pomelo peel under different pyrolysis temperatures (150-350 °C), which have a broad specific surface area range from 3.065 m2/g to 1274.577 m2/g. The active sites on the surface of PPCs have shown specific change laws of decreasing hydroxyl groups and increasing phosphate ester groups occurring as the pyrolysis temperature rises. Both reaction models (PFO and PSO models) and diffusion models (intra-particle diffusion models) have been applied to simulate the adsorption experimental data to verify the hypothesis deduced from the Elovich model. PPC-300 exhibits the highest adsorption capacity of MB (423 mg/g) under given conditions. Due to its large quantities of active sites on the external and internal surfaces (1274.577 m2/g), a fast adsorption equilibrium can be achieved within 60 min (with an initial MB concentration of 100 ppm). PPC-300 and PPC-350 also exhibit an intra-particle-diffusion-controlled adsorption kinetic process with a low initial MB concentration (100 ppm) or at the very beginning and final stage of adsorption with a high initial MB concentration (300 ppm) at 40 °C, considering that the diffusion is likely hindered by adsorbate molecules through internal pore channels at the middle stage of adsorption in these cases.

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The Brazil nut shell was used as a precursor material for preparing activated carbon by chemical activation with potassium hydroxide. The obtained material (BNSAC) was characterized, and the adsorptive features of phenol were investigated. The characterization showed that the activated carbon presented several rounded cavities along the surface, with a specific surface area of 332 m2 g-1. Concerning phenol adsorption, it was favored using an adsorbent dosage of 0.75 g L-1 and pH 6. The kinetic investigation revealed that the system approached the equilibrium in around 180 min, and the Elovich model represented the kinetic curves. The Sips model well represented the equilibrium isotherms. In addition, the increase in temperature from 25 to 55 °C favored the phenol adsorption, increasing the maximum adsorption capacity value (qs) from 83 to 99 mg g-1. According to the estimated thermodynamic parameters, the adsorption was spontaneous, favorable, endothermic, and governed by physical interactions. Therefore, the Brazil nut shell proved a good precursor material for preparing efficient activated carbon for phenol removal.

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The adsorption isotherms, kinetics, and thermodynamics of fluoride ions (F-) on FeOOH powders in water were investigated to obtain fundamental information on FeOOH powders, which are used as F- adsorbents in drinking and industrial water, and industrial wastewater. FeOOH powders were prepared as precipitates by mixing aqueous FeCl3 and NaOH solutions (1:3 mol/mol) in the presence of 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibrils (TOCNs), carboxymethylcellulose (CMC), or TEMPO-oxidized cellulose (TOC) fibers (without nanofibrillation), and subsequent drying and pulverizing. The FeOOH:TOCN, FeOOH:CMC, and FeOOH:TOC dry mass ratios were controlled at 87:13. The amount of F- adsorbed by the FeOOH/TOCN powder per FeOOH mass was higher than those adsorbed by FeOOH, FeOOH/CMC, or FeOOH/TOC. The F- adsorption isotherms on the FeOOH-containing powders showed higher correlation coefficients with the Langmuir model than with the Freundlich model. This indicates that F- adsorbed on FeOOH initially formed a monolayer, predominantly via physical adsorption. Pseudo-second-order kinetics fitted well to the time-dependent F- adsorption behaviors on the FeOOH-containing powders. Thermodynamic analysis of F- adsorption on the FeOOH-containing powders showed that the ΔG values were negative, which indicates that F- adsorption on the FeOOH-containing powders proceeded spontaneously in water. The negative ΔG value for FeOOH/TOCN was higher than those for FeOOH, FeOOH/CMC, and FeOOH/TOC at the same temperature. This shows that the FeOOH/TOCN powder can be used as an excellent and efficient F- adsorbent in water.

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Aerogels are a class of lightweight, nanoporous, and nanostructured materials with diverse chemical compositions and a huge potential for applications in a broad spectrum of fields. This has led the IUPAC to include them in the top ten emerging technologies in chemistry for 2022. This review provides an overview of aerogel-based adsorbents that have been used for the removal and recovery of uranium from aqueous environments, as well as an insight into the physicochemical parameters affecting the adsorption efficiency and mechanism. Uranium removal is of particular interest regarding uranium analysis and recovery, to cover the present and future uranium needs for nuclear power energy production. Among the methods used, such as ion exchange, precipitation, and solvent extraction, adsorption-based technologies are very attractive due to their easy and low-cost implementation, as well as the wide spectrum of adsorbents available. Aerogel-based adsorbents present an extraordinary sorption capacity for hexavalent uranium that can be as high as 8.8 mol kg−1 (2088 g kg−1). The adsorption data generally follow the Langmuir isotherm model, and the kinetic data are in most cases better described by the pseudo-second-order kinetic model. An evaluation of the thermodynamic data reveals that the adsorption is generally an endothermic, entropy-driven process (ΔH0, ΔS0 > 0). Spectroscopic studies (e.g., FTIR and XPS) indicate that the adsorption is based on the formation of inner-sphere complexes between surface active moieties and the uranyl cation. Regeneration and uranium recovery by acidification and complexation using carbonate or chelating ligands (e.g., EDTA) have been found to be successful. The application of aerogel-based adsorbents to uranium removal from industrial processes and uranium-contaminated waste waters was also successful, assuming that these materials could be very attractive as adsorbents in water treatment and uranium recovery technologies. However, the selectivity of the studied materials towards hexavalent uranium is limited, suggesting further developments of aerogel materials that could be modified by surface derivatization with chelating agents (e.g., salophen and iminodiacetate) presenting high selectivity for uranyl moieties.

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A low-cost and environmental-friendly sodium alginate-melamine@zeolitic imidazolate framework-67 (SA-ME@ZIF-67) adsorbent was fabricated by chemical grafting and in situ growth for the removal of lead ions in wastewater. Firstly, melamine (ME) was grafted onto sodium alginate (SA) by amide reaction, and then SA-ME was dropped into a solution of calcium chloride to form hydrogel bead, and ZIF-67 was grown on the SA-ME hydrogel bead by the in situ growth method. The SA-ME@ZIF-67 adsorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The SA-ME@ZIF-67 adsorbent was used to effectively adsorb Pb(II) from aqueous solutions. The initial concentrations of lead ions, adsorbent dose, initial pH of lead ion solution, temperature, and adsorption time for the material were optimized. The adsorption isotherms and kinetics fitted to Langmuir isotherm model (R2 = 0.9281, 0.9420, and 0.9623 at the temperatures of 288.15 K, 298.15 K, and 308.15 K, respectively) and pseudo-second-order kinetic model (R2 = 0.9901) respectively. According to the Langmuir model at 308.15 K, the maximum adsorption capacity of the adsorbent for Pb(II) was 634.99 mg/g. The recycling application of the adsorbent was possible as it was easily collected and reused after five adsorption-regeneration cycles. In addition, the Pb(II) in real wastewater samples has been efficiently removed using the fabricated hydrogel. The results showed that the SA-ME@ZIF-67 adsorbent had high adsorption capacity, removal efficiency, and easy recyclability for Pb(II).

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In recent years, there has been significant interest in the study of spandex in high-elasticity sensors. As a new kind of special spandex, dyeable spandex shows strong adsorption capacity for anions. In this study, neutral red G was used as an anion adsorption simulator to study the adsorption mechanism of dyeable spandex on anionic materials. The structure of dyeable spandex was characterized by the modern instrumental analysis method, and the adsorption kinetics and thermodynamics of neutral red G on dyeable spandex were discussed. The results show that the use of mixed amines as chain extenders for dyeable spandex reduced the regularity of molecules and the crystallinity of spandex, which was beneficial to the diffusion adsorption of anions. On the other hand, the number of secondary amino groups increased, providing more adsorption sites under acidic conditions. The adsorption of neutral red G on dyeable spandex satisfied the quasi-second-order kinetics and the Langmuir adsorption model, indicating that dye adsorption on spandex was mainly electrostatic. The diffusion coefficient and equilibrium adsorption capacity of neutral red G on dyeable spandex increased significantly, whereas enthalpy and entropy decreased.

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Firstly, spherical magnesium oxide was synthesized by simple magnesium salt and specific reaction conditions. Then, lanthanum-modified spherical magnesium oxide (LSMO) was prepared by impregnation of lanthanum salt. The adsorption mechanism of the adsorbent was investigated by XRD, SEM, XPS, and FT-IR. Through the study of fluorine removal performance, for the solution with fluoride ion concentration of 10 mg·L-1, the fluorine removal efficiency of lanthanum-modified spherical magnesium oxide (15LSMO) (93.1%) with 15% impregnation mass ratio is higher than that of SMO (82.7%). In addition, in the pH range of 2-11 or in the presence of interfering ions, the fluoride removal effect of 15LSMO still meets the fluoride removal efficiency of more than 90%. The research enhanced the profound insights into the effect and mechanism of fluorine removal of lanthanum modified materials.

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Two carbon composite materials were prepared by mixing avocado biochar and methyl polysiloxane (MK). Firstly, MK was dissolved in ethanol, and then the biochar was added at different times. In sample 1 (R1), the time of adding biochar was immediately after dissolving MK in ethanol, and in sample 2 (R2), after 48 h of MK dissolved in ethanol. The samples were characterized by nitrogen adsorption/desorption measurements obtaining specific surface areas (SBET) of 115 m2 g-1 (R1) and 580 m2 g-1 (R2). The adsorbents were further characterized using scanning electron microscopy, FTIR and Raman spectroscopy, adsorption of vapors of n-heptane and water, thermal analysis, Bohem titration, pHpzc, and C H N elemental analysis. R1 and R2 adsorbents were employed as adsorbents to remove the antibiotic ciprofloxacin from the waters. The t1/2 and t0.95 based on the interpolation of Avrami fractional-order were 20.52 and 246.4 min (R1) and 14.00 and 157.6 min (R2), respectively. Maximum adsorption capacities (Qmax) based on the Liu isotherm were 10.77 (R1) and 63.80 mg g-1 (R2) for ciprofloxacin. The thermodynamic studies showed a spontaneous and exothermic process for both samples, and the value of ΔH° is compatible with physical adsorption.

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In order to remove toxic graphene oxide (GO) from aqueous solution, attapulgite (ATP) was used as adsorbent to recycle it by adsorption. In this paper, the effects of different pH, adsorbent mass, GO concentration, time and temperature on the adsorption of GO by attapulgite were studied, and the adsorption performance and mechanism were further explored by XRD, AFM, XPS, FTIR, TEM and SEM tests. The results show that when T = 303 K, pH = 3, and the GO concentration is 100 mg/L in 50 mL of aqueous solution, the removal rate of GO by 40 mg of attapulgite reaches 92.83%, and the partition coefficient Kd reaches 16.31. The adsorption kinetics results showed that the adsorption equilibrium was reached at 2160 min, and the adsorption process could be described by the pseudo-second-order adsorption equation, indicating that the adsorption process was accompanied by chemical adsorption and physical adsorption. The isotherm and thermodynamic parameters show that the adsorption of GO by attapulgite is more consistent with the Langmuir isotherm model, and the reaction is a spontaneous endothermic process. The analysis shows that attapulgite is a good material for removing GO, which can provide a reference for the removal of GO in an aqueous environment.

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Waste residue of Chinese prickly ash seeds were simply treated with aqueous ZnCl2 to prepared the high-performed activated carbon. It was characterized by the methods of XRD, SEM, EDX, FT-IR, BET and XPS. The synergetic adsorption performance of Chinese prickly ash seeds activated carbon for Pb2+, Ni2+ and Acid Orange IΙ (AO) was studied. In the single-component system, the adsorption capacity of Pb2+, Ni2+ and AO were 15.1, 10.7 and 188.4 mg/g, respectively. In the AO-Pb2+ system, the maximum adsorption capacity of Pb2+ and AO were 79.40 and 332.68 mg/g under temperature of 30°C and pH of 5.0, respectively. For AO-Ni2+ system, it was 375.6 and 38.3 mg/g, respectively. The adsorption kinetics was satisfactorily fitted by the pseudo-second-order model. The synergic adsorption process can be smoothly described by the non-modified Sips isotherm.

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Municipal and residential water purification rely heavily on activated carbon (AC), but regeneration of AC is costly and cannot be performed at the point-of-use. Clay minerals (CMs) comprise a class of naturally abundant materials with known capacities for analyte adsorbance. However, the gel-forming properties of CMs in aqueous suspension pose problems for these materials being used in water-purification. In this study, we have taken three main steps to optimize the use of CMs in these applications. First, we produced several variants of montmorillonite CMs to evaluate the effect of interstitial cation hydrophobicity on the ability of the CM to uptake chargecarrying organic pollutants. These variants include CMs with the following cations: sodium, hexyl(triphenyl) phosphonium, hexyadecyl(triphenyl)phosphonium, and hexyl(tributyl)phosphonium. Second, we synthesized polymer-clay mineral composite films composed of polyvinyl alcohol (PVA), crosslinked in the presence of a CM variant. These films were evaluated for their ability to uptake malachite green (MG). Finally, we developed a one-pot synthetic method for the generation of polymer-clay particles for use in a continuous column process. We synthesized polymer-clay mineral particles using the highest performing CM (based on the film experiments) and evaluated the equilibrium capacity and kinetics of MG uptake from solution.

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The pace of industrialization and rapid population growth in countries such as India entail an increased input of industrial and sanitary organic micropollutants, the so-called emerging contaminants (EC), into the environment. The emission of EC, such as pharmaceuticals, reaching Indian water bodies causes a detrimental effect on aquatic life and ultimately on human health. However, the financial burden of expanding sophisticated water treatment capacities renders complementary, cost-efficient alternatives, such as adsorption, attractive. Here we show the merits of washed and milled pigeon pea husk (PPH) as low-cost adsorbent for the removal of the EC trimethoprim (TMP) and atenolol (ATN) that are among the most detected pharmaceuticals in Indian waters. We found a linear increase in adsorption capacity of PPH for TMP and ATN at concentrations ranging from 10 to 200 µg/L and from 50 to 400 µg/L, respectively, reflecting the concentrations occurring in Indian water bodies. Investigation of adsorption kinetics using the external mass transfer model (EMTM) revealed that film diffusion resistance governed the adsorption process of TMP or ATN onto PPH. Moreover, analysis of the adsorption performance of PPH across an extensive range of pH and temperature illustrated that the highest adsorption loadings achieved concurred with actual conditions of Indian waters. We anticipate our work as starting point towards the development of a feasible adsorbent system aiming at low-cost water treatment.

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This paper primarily aimed to provide some concerns and continue discussion about the previous published paper in this journal. First, when the mechanism of Cr(VI) removal from solution involved in adsorption-coupled reduction was proposed, the X-ray photoelectron spectroscopy (XPS) of Cr 2p spectrum of laden adsorbent (i.e., DDTC-LDH after adsorption) needs to demonstrate the co-existence of Cr(VI) and Cr(III). The detection of reduced Cr(III) in solution after the completed adsorption of Cr(VI) only provides information on the mechanism regarding reduction, not adsorption-coupled reduction. Second, adsorption mechanism (chemisorption or physisorption) cannot be drawn only based on the best statistical fit between the time-dependent data of adsorption experiment and the kinetic model (i.e., the pseudo-second-order, Elovich, or Avrami model). Third, the constant KRP (liters per grams of adsorbent not adsorbate; L/g) of the Redlich-Peterson isotherm model is not equal to or used as the thermodynamic equilibrium constant KEqo. The application of the constant KRP for calculating the thermodynamic parameters of adsorption process (∆G°, ∆H°, and ∆G°) using the van't Hoff equation leads to a certain error in the values (sign and magnitude) of those parameters. Fourth, the pHPZC of adsorbent is significant different to its pHIEP on both meanings and analysis methods. The use of those terminologies in the fields of material and sorption (adsorption and absorption) must be correct. Finally, some important information needs to provide in the studies of adsorption isotherm and mechanism (i.e., solution pH) and characteristics of diethyldithiocarbamate intercalated-LDH (i.e., arrangement and orientation of diethyldithiocarbamate in the interlayer region of DDTC-LDH).

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The present study was designed to produce novel cross-linked Chitosan and Chitosan/ß-Cyclodextrin beads and study the adsorption of Indigo Carmine. Both adsorbents were characterized by SEM and FTIR techniques. Batch experiments were conducted in order to evaluate the effect of initial adsorbent's concentration, dye's initial concentration, initial pH and temperature. In all cases Chitosan/ß-Cyclodextrin crosslinked beads exhibited higher removal efficiency of Indigo Carmine. Higher removal rates of Indigo Carmine were observed at low values of dye's initial concentration, pH and temperature, and high concentrations of adsorbent. The equilibrium adsorption data were a good fit for both Langmuir and Freundlich models and maximum adsorption capacity was 500.0 and 1000.0 mgIC/gadsorbent for Chitosan and Chitosan/ß-Cyclodextrin crosslinked beads, respectively. Adsorption of Indigo Carmine was found to follow the pseudo-second order. The negative values of ΔGo, ΔHo and ΔSo indicate that the adsorption process is exothermic, spontaneous and favorable at low temperatures.

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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, N2 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.

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