Low Dye Concentration Research Articles

Acid-Basic Activation of Carbon-Containing Sorption Material and Its Application for Extraction of Methylene Blue Dye from Aquatic Media

The results of the use of thermally modified kieselguhr sludge from the production of vegetable oils (TKSH500) of the initial and activated with a 30 % solution of nitric acid (TKSH500k) and 1M sodium hydroxide solution (TKSH500sh) for purification of model solutions from the dye methylene blue (MB) are presented. The maximum activating effect was achieved as a result of acid treatment, which leads to a 38 % increase in the total acidity of the sorption material in comparison with the initial one. It is shown that the sorption isotherms of the dye on the initial and activated samples of TKSH500 have an S-shaped form. In the region of low dye concentrations, a monolayer is formed; with an increase in the dye content, sorption becomes polymolecular. Analysis of the IR spectra of sorption materials after adsorption of the MB dye showed a shift to the low-frequency region of the positions of the bands in the regions corresponding to the vibrations of the O–H and C = O bonds, which indicates the ionization of hydroxyl and carboxyl groups present in the sorption materials, and the formation of a bond between them and the MB molecule.

(Invited) Mechanistic Studies for Electrochemical Self-Assembly of Cuscn/Stilbazolium Dye Hybrid Thin Films

We have established electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films in which the inorganic is CuSCN, known as a wide bandgap p-type semiconductor, whereas the organic is 4-N,N-dimethylamino-4’-N’-methylstilbazolium chromophore (abbreviated as DAS+) as its salt with tosylate (DAST) known to exhibit second-order nonlinear optical property for terahertz emitters. The CuSCN/DAS hybrid thin films by ESA show concerted photoluminescence based on energy transfer from inorganic CuSCN to organic DAS, making us anticipate its potential use in optoelectronic devices [1]. Understanding the mechanism of ESA to obtain tuning knob to maximize its functionality is therefore important.In our previous study, switching of dye loading mechanism has been suggested, depending on DAS concentration (C DAS) in the bath [2]. With low C DAS, the loading is limited by diffusion so that DAS is entrapped within CuSCN crystal grains, while surface reaction of hybridization begins to limit the dye loading with high C DAS, resulting in formation of unique nanostructures as well as phase separation of inorganic and organic domains. The border for the switching of dye loading mechanism was found as the ratio between bulk concentrations of dye and the [Cu(SCN)]+ complex, C DAS/C comp = ca. 1/31 in case of DAS+ [3].In this study, electrochemical analysis has been performed employing rotating disk electrode (RDE) under variation of bulk concentration of dye (DAST and CNST = 4-cyano-4’-(N’-methyl)stilbazolium tosylate for comparison) to verify the proposed mechanism. CNS+ has a strongly electron withdrawing -CN group and therefore bears a much larger dipole moment of 23.5016 Debye than that of DAS+ (10.1442 Debye) as determined by DFT calculation. Thus, a much stronger interaction of CNS+ with CuSCN (essentially with SCN- ion) is expected than DAS+.The overall behavior of CNS+ has been found exactly the same as DAS+ such as changing the crystal orientation of β-CuSCN to lay down its c-axis and phase transition from β- to α-CuSCN. However, such transitions were found for smaller concentrations of CNS+ than DAS+ because of its stronger affinity with CuSCN. The switching dye loading mechanism and associated change of the hybrid structure has also been observed for CNS. Fig. 1 shows plots of amount of dye loaded into the hybrid thin films against the dye concentrations in the electrolytic bath for DAS+ and CNS+. The steep slopes in low dye concentration range represent diffusion limited loading, whereas the moderate slopes are those limited by surface reaction. The bending points, C DAS = 60 μmol dm-3 and C CNS = 200 μmol dm-3, indicate the switching borders for C comp = 2.5 mM. Because of the increased stability of adsorption of CNS+ on CuSCN surface, diffusion limited loading, thus all dyes reaching the electrode surface buried inside the film, continues to operate up to this high dye concentration. The increased stability of CuSCN/CNS surface complex also resulted in about 3 times more efficient dye uptake in the surface reaction limited regime. These results nicely confirm the validity of the proposed mechanism both for DAS+ and CNS+, and that the switching border can be varied by the stability of CuSCN/dye complex. Full analysis should be able to determine C CNS/C comp ratio as the switching border.[1] K. Uda et al. ACS Omega, 4, 4056-4062 (2019).[2] Y. Tsuda et al., Monatshefte für Chemie, 148, 845-854 (2017).[3] Y. Tsuda et al., J. Electrochem. Soc. 166(9) B3096-B3102 (2019). Figure 1

Effect of Random Nanostructured Metallic Environments on Spontaneous Emission of HITC Dye.

We have studied emission kinetics of HITC laser dye on top of glass, smooth Au films, and randomly structured porous Au nanofoams. The observed concentration quenching of luminescence of highly concentrated dye on top of glass (energy transfer to acceptors) and the inhibition of the concentration quenching in vicinity of smooth Au films were in accord with our recent findings. Intriguingly, the emission kinetics recorded in different local spots of the Au nanofoam samples had a spread of the decay rates, which was large at low dye concentrations and became narrower with increase of the dye concentration. We infer that in different subvolumes of Au nanofoams, HITC molecules are coupled to the nanofoams weaker or stronger. The inhibition of the concentration quenching in Au nanofoams was stronger than on top of smooth Au films. This was true for all weakly and strongly coupled subvolumes contributing to the spread of the emission kinetics. The experimental observations were explained using theoretical model accounting for change in the Förster radius caused by the strong energy transfer to metal.

Development of Ultra-Performance Liquid Chromatography-Mass Spectrometry Method for Simultaneous Determination of Three Cationic Dyes in Environmental Samples.

Lower dye concentrations and the presence of several dyes along with other matrices in environmental samples restrict their determination. Herein, a highly sensitive and rapid ultra-performance tandem mass spectrometric method was developed for simultaneous determination of cationic dyes, namely methylene blue (MB), rhodamine B (RB) and crystal violet (CV), in environmental samples. To preconcentrate environmental samples, solid-phase extraction cartridges were developed by using hydrogen peroxide modified pistachio shell biomass (MPSB). The surface morphological and chemical functionalities of MPSB were well characterized. The developed method was validated considering different validation parameters. In terms of accuracy and precision, the %RSD for all three dyes at all four concentration points was found to be between 1.26 and 2.76, while the accuracy reported in terms of the recovery was found to be 98.02%-101.70%. The recovery was found to be in the range of 98.11% to 99.55%. The real sample analysis shows that MB, RB, and CV were found in the ranges of 0.39–5.56, 0.32–1.92 and 0.27–4.36 μg/mL, respectively.

Iodinated xanthene-cyanine NIR dyes as potential photosensitizers for antimicrobial photodynamic therapy

Photosensitizers (PSs) are chemical entities that upon light exposure are able to produce cytotoxic species such as singlet oxygen superoxide and free radicals. PSs are used in photodynamic therapy applications (PDT) to eradicate cancer cells, pathogenic bacteria, fungi, and viruses. Development of the NIR-activatable photosensitizes with high phototoxicity and low toxicity in dark conditions is challenging. Here we first report on the synthesis and antimicrobial testing of the new NIR photosensitizers based on the iodinated xanthene-cyanine dyes. These new photosensitizers exhibit high antimicrobial efficacy on Staphylococcus aureus pathogens at low dye concentration (~0.5 μM) and low NIR light dose (24.3 J/cm2).

An Anionic Metal‐organic Framework for Selective Adsorption Separation toward Methylene Blue and Rhodamine B

Microporous metal organic framework NOTT‐210 was synthesized via solvothermal and dyes adsorption and separation properties were determined and discussed. NOTT‐210 with anion characteristic can selective adsorb low concentrations of cationic dyes from effluents at room temperature. And that NOTT‐210 can also separate the MB+ (methylene blue) and RB+ (rhodamine B) molecules because of size‐dependent effect and kinetics‐dependent effect. Hence, NOTT‐210 is among the very few porous MOFs which not only can adsorb low concentrations of MB+ and RB+ molecules but also has the ability to separate their mixture.

Degradation and toxicity evaluation of azo dye Direct red 83:1 by an advanced oxidation process driven by pulsed light

Water contamination by dyes is an ecological problem that can be alleviated by advanced oxidation processes (AOPs). A common AOP uses hydroxyl radicals generated by splitting H2O2 using UV light. Pulsed light (PL) technology can be used as light source in AOPs having the advantage of producing fast effects. Direct red 83:1 (DR) is an azo dye that is being used to study the elimination of dyes from wastewaters but details about its degradation by a PL/H2O2 process are missed. In this work, the effect of H2O2 and dye concentrations, pH and salts on the decolourization of DR were determined by spectrophotometry. The PL/H2O2 process was able to degrade nearly 80 % of the dye after 45 light pulses. Absence of photolysis and inhibition by hydroxyl scavenging indicate that the degradation was due to oxidation hydroxyl radicals. The decolouration was higher at low dye concentration, high H2O2 concentration and alkaline conditions, and was inhibited by salts. These results are useful for the further use of DR as model dye to study the potential of PL as an alternative light source in AOPs for dye degradation. Further studies are recommended to estimate the treatment conditions required for enhancing toxicity abatement.

Adsorption of selected azo dyes from an aqueous solution by activated carbon derived from Monotheca buxifolia waste seeds

In this study, activated carbon derived from Monotheca buxifolia waste seeds was used for the adsorptive removal of a number of selected azo dyes such as Eriochrome Black T (EBT), Remazol brilliant blue (RBB), Remazol yellow (RY) and Remazol brilliant orange (RBO) from an aqueous solution by changing the initial dye concentration, adsorbent dosage, solution pH, contact time and temperature. A Fourier transform infrared spectroscopic analysis of the activated carbon showed the existence of hydroxyls, methyl, methylene, carbonyls, alkane and alkenes groups while the scanning electron microscopic image displayed the gradual formation of cavities and open pores on the surface. The results showed that as the amount of the adsorbent and the shaking time were increased, the removal percentage of the dye increased accordingly. Higher adsorption percentages were observed at a lower dye concentration and temperature in an acidic media at a pH range (1–5). The investigated data were evaluated with the Langmuir and Freundlich adsorption models. The maximum adsorption capacities obtained from the Langmuir model were 112.36, 96.34, 97.65 and 90.91 mg/g for EBT, RBB, RY and RBO, respectively. The results indicated that the electrostatic interaction was the main cause of the adsorption of these anionic azo dyes on the surface of the activated carbon.

TADF Dye-Loaded Nanoparticles for Fluorescence Live-Cell Imaging.

Thermally activated delayed fluorescence (TADF) molecules offer nowadays a powerful tool in the development of novel organic light emitting diodes due to their capability of harvesting energy from non-emissive triplet states without using heavy-metal complexes. TADF emitters have very small energy difference between the singlet and triplet excited states, which makes thermally activated reverse intersystem crossing from the triplet states back to the singlet manifold viable. This mechanism generates a long-lived delayed fluorescence component which can be explored in the sensing of oxygen concentration, local temperature, or used in time-gated optical cell-imaging, to suppress interference from autofluorescence and scattering. Despite this strong potential, until recently the application of TADF outside lighting devices has been hindered due to the low biocompatibility, low aqueous solubility and poor performance in polar media shown by the vast majority of TADF emitters. To achieve TADF luminescence in biological media, careful selection or design of emitters is required. Unfortunately, most TADF molecules are not emissive in polar media, thus complexation with biomolecules or the formation of emissive aggregate states is required, in order to retain the delayed fluorescence that is characteristic of these compounds. Herein, we demonstrate a facile method with great generalization potential that maintains the photophysical properties of solvated dyes by combining luminescent molecules with polymeric nanoparticles. Using an established swelling procedure, two known TADF emitters are loaded onto polystyrene nanoparticles to prepare TADF emitting nanomaterials able to be used in live-cell imaging. The obtained particles were characterized by optical spectroscopy and exhibited the desired TADF emission in aqueous media, due to the polymeric matrix shielding the dye from solvent polarity effects. The prepared nanoparticles were incubated with live human cancer cells and showed very low cytotoxicity and good cellular uptake, thus making fluorescence microscopy imaging possible at low dye concentrations.

Novel approach for effective removal of methylene blue dye from water using fava bean peel waste

Fava bean peels, Vicia faba (FBP) are investigated as biosorbents for the removal of Methylene Blue (MB) dye from aqueous solutions through a novel and efficient sorption process utilizing ultrasonic-assisted (US) shaking. Ultrasonication remarkably enhanced sorption rate relative to conventional (CV) shaking, while maintaining the same sorption capacity. Ultrasonic sorption rate amounted to four times higher than its conventional counterpart at 3.6 mg/L initial dye concentration, 5 g/L adsorbent dose, and pH 5.8. Under the same adsorbent dose and pH conditions, percent removal ranged between 70–80% at the low dye concentration range (3.6–25 mg/L) and reached about 90% at 50 mg/L of the initial dye concentration. According to the Langmuir model, maximum sorption capacity was estimated to be 140 mg/g. A multiple linear regression statistical model revealed that adsorption was significantly affected by initial concentration, adsorbent dose and time. FBP could be successfully utilized as a low-cost biosorbent for the removal of MB from wastewater via US biosorption as an alternative to CV sorption. US biosorption yields the same sorption capacities as CV biosorption, but with significant reduction in operational times.

Low-cost sisal fibers/polypyrrole/polyaniline biosorbent for sequestration of reactive orange 5 from aqueous solutions

Abstract Sisal is a natural fibrous low-cost biomaterial that is frequently found in the surrounding environment and has no toxic effects. To upgrade its performance and applicability, sisal was modified with polypyrrole/polyaniline via in-situ chemical oxidative polymerization technique for reactive orange 5 elimination from aqueous media. Nowadays, dye pollution and its subsequent adverse effects have been of great concern for all around the world. The prepared composite was characterized by SEM, FTIR, and XRD analysis; they indicated that the polypyrrole and polyaniline were successfully coated on sisal. Optimum contact time was found at 120 min, and at the adsorbent dosage of 200 mg, almost 97 % of dye was removed. At low dye concentration (5−10 ppm), the efficiency of the sorption system was significantly acceptable (99 %). pH 2 had the maximum adsorption capacity due to attraction between negatively charged dye and positive nature of sisal composite. In view of thermodynamics, the process was endothermic and so better removal was observed at 45 °C. Langmuir/Freundlich and Pseudo-second order could satisfactorily expound the sorption system with R2 values of greater than 0.99, exhibiting that physisorption/chemisorption occurred. Sisal/polypyrrole/polyaniline was more than 5.69 times effective than raw sisal for dye adsorption. In the case of synthetic wastewater, the removal efficiency reached 81 %. Hence, the low-cost sisal/polypyrrole/polyaniline composite was a promising alternative for reactive orange 5 removal.

SERS substrates based on silver nanoparticles and graphene oxide

Simple work methods for preparing active coatings for surface-enhanced Raman scattering (SERS) are demonstrated in the article. SERS active films of colloidal silver nanoparticles and composites based on graphene oxide and silver nanoparticles were obtained. The prepared disperse solutions of silver nanoparticles and graphene oxide/Ag nanoparticles composites have different stability. Using a scanning electron microscope, the structure of the prepared films was studied. A comparative characteristic of the obtained SERS active substrates is given. The dye Rhodamine 6G was used as the test substance. It was shown that the smallest enhancement of the Raman signal is produced by a coating of colloidal silver nanoparticles, while the graphene oxide/Ag nanoparticles composite obtained by the 2-stage method provides the greatest gain. The different ability to amplify the Raman signal is explained by the difference in the structure and composition of the obtained SERS active films. All prepared coatings make it easy to detect low dye concentrations (from a 10–6 M solution) both with resonance (532 nm) and nonresonance (632.8 nm) excitation.

Effect of energetic disorder on triplet-triplet annihilation in organic semiconductors

We present a model for the triplet-triplet annihilation in organic phosphorescent host-guest systems that considers the effect of the energetic disorder on the kinetics of the annihilation. Nonequilibrium (time-dependent) transport of the triplets that arises from the progressive relaxation of triplets in the energy landscape is taken into account in the model. Triplet excitons are considered to move between the guest sites (dye molecules) via the thermally activated tunneling mechanism; the annihilation step, however, takes place through the F\"orster mechanism. Based on the model developed, and by calculating the time evolution of the triplet concentration, we investigate the effect of the various parameters on the effective annihilation coefficient. At low dye concentrations, it is shown that relaxation of the triplets is not completed during their lifetimes, and therefore, the annihilation process occurs entirely in the nonequilibrium. We also address the competition between two pathways for the annihilation process: single-step, long-range annihilation, and diffusion-assisted annihilation. By a quantitative comparison with experimental data reported in the literature, we demonstrate certain conditions in which there is a considerable contribution from the diffusion to the total annihilation rate. The model presented in this work can also be used for the excitons that diffuse by the F\"orster mechanism.

MINERAL-BASED MAGNETIC NANOCOMPOSITE SORBENTS

The article is devoted to the synthesis of mineral-based magnetic nanocomposite sorbents and the study of the influence of modification by magnetite and molybdenum disulfide on the structural-sorption and surface properties of native saponite clay. Modification of native saponite clay with nanoscale magnetite increases the specific surface area and changes pore’s distribution of the original clay from monomodal to bimodal. Next modification of magnetic saponite by micro-sized and nano-sized molybdenum disulfide results in blocking of the secondary porous structure (bimodality disappears of magnetic saponite), but it is increasing the specific surface area. It was found that the sorption activity of modified and unmodified saponite in the region of low concentrations of cationic and anionic dyes (Methyl blue and Congo red) is almost the same. The study of Congo red dye adsorption from highly concentrated solutions showed significant differences in the sorption activities of modified and unmodified saponite samples: the largest sorption capacity characteristic of ternary composites (saponite modified by magnetite and by nano-sized molybdenum disulfide). These ternary composites had in 62 times more activity than native saponite clay and 10 times more than magnetic saponite. It is established that all the samples are characterized by basic properties, but the sample of native saponite modified by magnetite and nano-sized molybdenum disulfide has the largest number of active centers (both acidic and basic character). Thus, it is shown that the modification of the native saponite clay significantly affects not only the texture-sorption but also the surface properties of the native saponite clay.

Effect of fluorescent dye positioning and concentration on the growth parameters and lipid content of Chlorella sp. in a flat panel photobioreactor.

In this study, two different concentrations of fluorescent dye Rhodamine 6G (R6G) with two different strategies were used in a double layer flat panel photobioreactor (PBR) for investigation of its effect on growth parameters of microalgae Chlorella sp. Results showed that in the first strategy, when the light passed through the dye before reaching the broth, biomass productivity rate (P) and maximum specific growth rate (µmax) relative to control case, were increased up to 60 and 23% respectively. Increasing in these parameters were more, for the low dye concentration. Also, in the second strategy, when the light passed through the microalgae before reaching the dye solution, P and µmax for lower concentration increased about 9 and 15%, respectively. But using high dye concentration growth of the algae was decreased. Furthermore, using R6G caused increase in the lipid and chlorophyll content of the microalgae Chlorella sp.

Sugarcane biomass colonized by Pleurotus ostreatus for red 4B dye removal: a sustainable alternative

ABSTRACT Biosorption of the red 4B dye was evaluated using non-colonized sugarcane bagasse and colonized by Pleurotus ostreatus. The fungal colonization caused an increase in the acid and phenolic groups, making the biosorbent surface more positive, with lower thermal stability due to decomposition of lignocellulosic compounds, lower pHpcz, and smaller pores. The biosorbents showed better adsorption at pH 2.0 and required 260 min to reach equilibrium. The kinetic data fit the pseudo-second order mathematical model, which predicts strong chemical interaction between adsorbent and adsorbate. The mathematical models that best fit the isothermal data were the combination of Langmuir for low dye concentrations and Freundlich for high dye concentrations in the solution for the non-colonized biosorbent, which predict that adsorption occurs in monolayer and multilayer, respectively. For the colonized biosorbent, the model that best fits the isothermal data (25°C and 40°C) was the Freundlich model, showing that the adsorption for this case occurs in multilayers. Thermodynamic studies (25°C, 40°C and 50°C) show that increasing temperature decreases the biosorption capacity (exothermic process for both biosorbents), and the system shows low spontaneity with increasing concentration. Also, the entropy for non-colonized sugarcane bagasse increases at low concentrations, however after fungal colonization, it decreases for both. In industrial effluent, the non-colonized biosorbent presented a higher biosorption capacity, but fungal colonization demonstrates greater sustainability by initially allowing the production of mushrooms.

UV/H2O2, UV/H2O2/SnO2 and Fe/H2O2 based advanced oxidation processes for the degradation of disperse violet 63 in aqueous medium

The photodegradation of disperse violet 63 dye was investigated in aqueous solution using UV/H2O2, UV/H2O2/SnO2 and Fenton reagent. The maximum decolorization was achieved in 60 min with 50 mg l−1 of dye concentration. The suitability of each process depends upon dye concentration. The photo degradation is very effective at low dye concentration. The degradation percentage increased by enhancing initial amount of hydrogen peroxide and UV irradiation time. The influence of operational parameters like pH, H2O2 concentration, catalyst amount and dye concentration were investigated. After 60 min reaction time, the maximum decolorization of disperse violet 63 with UV/H2O2, UV/H2O2/SnO2 and Fe/H2O2 was 81%, 92.7% and 96.4% respectively. The results indicated that Fenton process had more photocatalytic activity for degradation of disperse violet 63 dye than that of UV/H2O2 and UV/H2O2/SnO2. After 60 min, the comparative decomposition order was Fe/H2O2 > UV/H2O2/SnO2 > UV/H2O2. It may be concluded that Fenton process could possibly be used for the remediation of toxic pollutants from textile effluents.

Silica nanoparticles with thermally activated delayed fluorescence for live cell imaging.

Thermally activated delayed fluorescence (TADF) has revolutionized the field of organic light emitting diodes owing to the possibility of harvesting non-emissive triplet states and converting them in emissive singlet states. This mechanism generates a long-lived delayed fluorescence component which can also be used in sensing oxygen concentration, measuring local temperature, or on imaging. Despite this strong potential, only recently TADF has emerged as a powerful tool to develop metal-free long-lived luminescent probes for imaging and sensing. The application of TADF molecules in aqueous and/or biological media requires specific structural features that allow complexation with biomolecules or enable emission in the aggregated state, in order to retain the delayed fluorescence that is characteristic of these compounds. Herein we demonstrate a facile method that maintains the optical properties of solvated dyes by dispersing TADF molecules in nanoparticles. TADF dye-doped silica nanoparticles are prepared using a modified fluorescein fluorophore. However, the strategy can be used with many other TADF dyes. The covalent grafting of the TADF emitter into the inorganic matrix effectively preserves and transfers the optical properties of the free dye into the luminescent nanomaterials. Importantly, the silica matrix is efficient in shielding the dye from solvent polarity effects and increases delayed fluorescence lifetime. The prepared nanoparticles are effectively internalized by human cells, even at low incubation concentrations, localizing primarily in the cytosol, enabling fluorescence microscopy imaging at low dye concentrations.

Decolorisation of Methylene Blue with Sodium Persulfate Activated with Visible Light in the Presence of Glucose and Sucrose

The paper presents the results of research on the methylene blue (MB) degradation with sodium persulfate (PDS) activated with visible light (Vis) in the presence of glucose and sucrose. The following test were examined: absence and presence of sugars in concentrations of 50–300 mM, presence and absence of Vis radiation, pH of the model solution (6.0–12.0), identification of free radicals, kinetics of the pseudo-first-order reaction. The degradation of the MB ranges from 58 to 84% depending on the pH of the model solution. The highest degradation degree (about 83–84%) was observed after 90 min of visible light irradiation for the process conducted in the presence of persulfate (6.5 mM) and glucose/sucrose (100.0 mM) at pH = 12.0 (PDS-12/100G/Vis and PDS-12/100S/Vis). The mathematically calculated half-life of MB (t/2) has been reduced in the visible-light system irradiated from 111.8 min (PDS in pH = 6.0) to 68.0 min (PDS-6/100S/Vis) and from 58.7 min (PDS in pH = 12.0) to 36.9 min (PDS-12/100S/Vis). Decolorisation of the methylene blue takes place with the participation of three radicals: sulfate $$ {\mathrm{SO}}_4^{\bullet -} $$, hydroxyl OH• and superoxide $$ {\mathrm{O}}_2^{\bullet -} $$. The dominant radicals were superoxide radicals. In a slightly acidic environment (pH = 6.0), there were hydroxyl and sulfate radicals. At pH = 12, hydroxyl radicals were mainly responsible for the degradation of methylene blue. The results of this study showed that method may be an interesting alternative for the treatment of coloured wastewater containing low dye concentrations.

A 2.5D Electrode System Constructed of Magnetic Sb–SnO2 Particles and a PbO2 Electrode and Its Electrocatalysis Application on Acid Red G Degradation

A novel electrode consisting of a Ti/PbO2 shell and Fe3O4/Sb–SnO2 particles was developed for electrochemical oxidation treatment of wastewater. Scanning electron microscope (SEM), X-ray diffraction (XRD), the current limiting method, toxicity experiments, and high-performance liquid chromatography were adopted to characterize its morphology, crystal structure, electrochemical properties, the toxicity of the wastewater, and hydroxyl radicals. Acid Red G (ARG), a typical azo dye, was additionally used to test the oxidation ability of the electrode. Results indicated that the 2.5D electrode could significantly improve the mass transfer coefficient and •OH content of the 2D electrode, thereby enhancing the decolorization, degradation, and mineralization effect of ARG, and reducing the toxicity of the wastewater. The experiments revealed that, at higher current density, lower dye concentration and higher temperature, the electrochemical oxidation of ARG favored. Under the condition of 50 mA/cm2, 25 °C, and 100 ppm, the ARG, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal efficiency reached 100%, 65.89%, and 52.52%, respectively, and the energy consumption and the current efficiency were 1.06 kWh/g COD, 8.29%, and energy consumption for TOC and mineralization current efficiency were 3.81 kWh/g COD, 9.01%. Besides, the Fe3O4/Sb–SnO2 particles after electrolysis for 50 h still had remarkable stability. These results indicated that the ARG solution could be adequately removed on the 2.5D electrode, providing an effective method for wastewater treatment.