Degradation of anti-inflammatory drug ketoprofen by electro-oxidation: comparison of electro-Fenton and anodic oxidation processes

The electrochemical degradation of the nonsteroidal anti-inflammatory drug ketoprofen in tap water has been studied using electro-Fenton (EF) and anodic oxidation (AO) processes with platinium (Pt) and boron-doped diamond (BDD) anodes and carbon felt cathode. Fast degradation of the parent drug molecule and its degradation intermediates leading to complete mineralization was achieved by BDD/carbon felt, Pt/carbon felt, and AO with BDD anode. The obtained results showed that oxidative degradation rate of ketoprofen and mineralization of its aqueous solution increased by increasing applied current. Degradation kinetics fitted well to a pseudo-first-order reaction. Absolute rate constant of the oxidation of ketoprofen by electrochemically generated hydroxyl radicals was determined to be (2.8?±?0.1)?×?10⁹ M^?1 s^?1 by using competition kinetic method. Several reaction intermediates such as 3-hydroxybenzoic acid, pyrogallol, catechol, benzophenone, benzoic acid, and hydroquinone were identified by high-performance liquid chromatography (HPLC) analyses. The formation, identification, and evolution of short-chain aliphatic carboxylic acids like formic, acetic, oxalic, glycolic, and glyoxylic acids were monitored with ion exclusion chromatography. Based on the identified aromatic/cyclic intermediates and carboxylic acids as end products before mineralization, a plausible mineralization pathway was proposed. The evolution of the toxicity during treatments was also monitored using Microtox method, showing a faster detoxification with higher applied current values.     

Kinetic behavior of anti-inflammatory drug ibuprofen in aqueous medium during its degradation by electrochemical advanced oxidation

The electrochemical abatement of the drug ibuprofen (2-(4-isobutylphenyl)propionic acid) from aqueous solution has been carried out by anodic oxidation. The electrolyses have been performed at constant current using a small, undivided cell equipped with a Pt or thin-film boron-doped diamond (BDD) anode and a carbon-felt cathode. The results have shown that ibuprofen has been destroyed under all the conditions tested, following pseudo-first-order kinetics; however, BDD enables higher removal rates than Pt, because the former produces greater quantity of ^?OH. Using BDD anode, the pseudo-first-order rate constant increased with applied current and when NaCl replaced Na₂SO₄ as supporting electrolyte, while it is almost unaffected by ibuprofen concentration. Mineralization of ibuprofen aqueous solutions was followed by total organic carbon (TOC) measurements. After 8 h of electrolysis, TOC removal varied from 91 % to 96 % applying a current in the range of 50–500 mA. The reaction by-products were quantified by chromatographic techniques, and in particular, aliphatic acids (oxalic, glyoxylic, formic, acetic, and pyruvic) have been the main intermediates formed during the electrolyses. The absolute rate constant for the oxidative degradation of ibuprofen have also been determined, by competition kinetic method, as 6.41?×?10⁹ M^?1?s^?1.     

Efficient removal of insecticide “imidacloprid” from water by electrochemical advanced oxidation processes

The oxidative degradation of imidacloprid (ICP) has been carried out by electrochemical advanced oxidation processes (EAOPs), anodic oxidation, and electro-Fenton, in which hydroxyl radicals are generated electrocatalytically. Carbon-felt cathode and platinum or boron-doped diamond (BDD) anodes were used in electrolysis cell. To determine optimum operating conditions, the effects of applied current and catalyst concentration were investigated. The decay of ICP during the oxidative degradation was well fitted to pseudo-first-order reaction kinetics and absolute rate constant of the oxidation of ICP by hydroxyl radicals was found to be k _abs(ICP)?=?1.23?×?10⁹ L mol^?1 s^?1. The results showed that both anodic oxidation and electro-Fenton process with BDD anode exhibited high mineralization efficiency reaching 91 and 94 % total organic carbon (TOC) removal at 2 h, respectively. For Pt-EF process, mineralization efficiency was also obtained as 71 %. The degradation products of ICP were identified and a plausible general oxidation mechanism was proposed. Some of the main reaction intermediates such as 6-chloronicotinic acid, 6-chloronicotinaldehyde, and 6-hydroxynicotinic acid were determined by GC-MS analysis. Before complete mineralization, formic, acetic, oxalic, and glyoxylic acids were identified as end-products. The initial chlorine and organic nitrogen present in ICP were found to be converted to inorganic anions Cl^?, NO₃ ^?, and NH₄ ⁺.     

Electro-Fenton degradation of the antibiotic sulfanilamide with Pt/carbon-felt and BDD/carbon-felt cells. Kinetics,reaction intermediates,and toxicity assessment

The degradation of 230 mL of a 0.6-mM sulfanilamide solution in 0.05 M Na₂SO₄ of pH 3.0 has been studied by electro-Fenton process. The electrolytic cell contained either a Pt or boron-doped diamond (BDD) anode and a carbon-felt cathode. Under these conditions, organics are oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton’s reaction between initially added (and then electrochemically regenerated) Fe²⁺ and cathodically generated H₂O₂. From the decay of sulfanilamide concentration determined by reversed-phase liquid chromatography, an optimum Fe²⁺ concentration of 0.20 mM in both cells was found. The drug disappeared more rapidly using BDD than Pt, and, in both cases, it was more quickly removed with raising applied current. Almost total mineralization was achieved using the BDD/carbon-felt cell, whereas the alternative use of Pt anode led to a slightly lower mineralization degree. In both cells, the degradation rate was accelerated at higher current but with the concomitant fall of mineralization current efficiency due to the greater increase in rate of the parasitic reactions of hydroxyl radicals. Reversed-phase liquid chromatography allowed the identification of catechol, resorcinol, hydroquinone, p-benzoquinone, and 1,2,4-trihydroxybenzene as aromatic intermediates, whereas ion exclusion chromatography revealed the formation of malic, maleic, fumaric, acetic, oxalic, formic, and oxamic acids. NH₄ ⁺, NO₃ ^?, and SO₄ ^2? ions were released during the electro-Fenton process. A plausible reaction sequence for sulfanilamide mineralization involving all detected intermediates has been proposed. The toxicity of the solution was assessed from the Vibrio fischeri bacteria luminescence inhibition. Although it acquired its maximum value at short electrolysis time, the solution was completely detoxified at the end of the electro-Fenton treatment, regardless of the anode used.     

Degradation of the herbicide 2,4-DP by anodic oxidation, electro-Fenton and photoelectro-Fenton using platinum and boron-doped diamond anodes

This paper reports the degradation of 2,4-DP (2-(2,4-dichlorophenoxy)-propionic acid) solutions of pH 3.0 by environmentally friendly electrochemical methods such as anodic oxidation, electro-Fenton and photoelectro-Fenton with a Pt or boron-doped diamond (BDD) anode. In the two latter techniques an O(2)-diffusion cathode was used and 1.0mM Fe(2+) was added to the solution to give hydroxyl radical (*OH) from Fenton's reaction between Fe(2+) and H(2)O(2) generated at the cathode. All treatments with BDD are viable to decontaminate acidic wastewaters containing 2,4-DP since they give complete mineralization, with loss of chloride ion, at high current due to the great production of oxidant *OH at the BDD surface favoring the destruction of final carboxylic acids. *OH formed from Fenton's reaction destroys more rapidly aromatic products, making the electro-Fenton and photoelectro-Fenton processes much more efficient than anodic oxidation. UVA light in photoelectro-Fenton with BDD has little effect on the degradation rate of pollutants. The comparative procedures with Pt lead to slower decontamination because of the lower oxidizing power of this anode. The effect of current on the degradation rate and efficiency of all methods is studied. The 2,4-DP decay always follows a pseudo-first-order kinetics. Chlorohydroquinone, chloro-p-benzoquinone and maleic, fumaric, malic, lactic, pyruvic, acetic, formic and oxalic acids are detected as products by chromatographic techniques. A general sequence accounting for by the reaction of all these intermediates with the different oxidizing agents is proposed.     

Degradation and mineralization of sulcotrione and mesotrione in aqueous medium by the electro-Fenton process: a kinetic study

Introduction

The degradation and mineralization of two triketone (TRK) herbicides, including sulcotrione and mesotrione, by the electro-Fenton process (electro-Fenton using Pt anode (EF-Pt), electro-Fenton with BDD anode (EF-BDD) and anodic oxidation with BDD anode) were investigated in acidic aqueous medium.

Methods

The reactivity of both herbicides toward hydroxyl radicals was found to depend on the electron-withdrawing effect of the aromatic chlorine or nitro substituents. The degradation of sulcotrione and mesotrione obeyed apparent first-order reaction kinetics, and their absolute rate constants with hydroxyl radicals at pH?3.0 were determined by the competitive kinetics method.

Results and discussion

The hydroxylation absolute rate constant (k _abs) values of both TRK herbicides ranged from 8.20?×?10⁸ (sulcotrione) to 1.01?×?10⁹ (mesotrione) L?mol^?1?s^?1, whereas those of the TRK main cyclic or aromatic by-products, namely cyclohexane 1,3-dione , (2-chloro-4-methylsulphonyl) benzoic acid and 4-(methylsulphonyl)-2-nitrobenzoic acid, comprised between 5.90?×?10⁸ and 3.29?×?10⁹?L?mol^?1?s^?1. The efficiency of mineralization of aqueous solutions of both TRK herbicides was evaluated in terms of total organic carbon removal. Mineralization yields of about 97?C98% were reached in optimal conditions for a 6-h electro-Fenton treatment time.

Conclusions

The mineralization process steps involved the oxidative opening of the aromatic or cyclic TRK by-products, leading to the formation of short-chain carboxylic acids, and, then, of carbon dioxide and inorganic ions.     

Electrochemical incineration of indigo. A comparative study between 2D (plate) and 3D (mesh) BDD anodes fitted into a filter-press reactor

This paper compares the performance of 2D (plate) and 3D (mesh) boron-doped diamond (BDD) electrodes, fitted into a filter-press reactor, during the electrochemical incineration of indigo textile dye as a model organic compound in chloride medium. The electrolyses were carried out in the FM01-LC reactor at mean fluid velocities between 0.9?≤?u?≤?10.4 and 1.2?≤?u?≤?13.9 cm s^?1 for the 2D BDD and the 3D BDD electrodes, respectively, at current densities of 5.63 and 15 mA cm^?2. The oxidation of the organic matter was promoted, on the one hand, via the physisorbed hydroxyl radicals (BDD(^●OH)) formed from water oxidation at the BDD surface and, on the other hand, via active chlorine formed from the oxidation of chloride ions on BDD. The performance of 2D BDD and 3D BDD electrodes in terms of current efficiency, energy consumption, and charge passage during the treatments is discussed.     

Efficient removal of triphenylmethane dyes from aqueous medium by in situ electrogenerated Fenton's reagent at carbon-felt cathode

Fenton's reagent (Fe2+ +H2O2) has been electrogenerated in situ in an undivided electrolytic cell from the effective reduction of Fe3+ and O2 at carbon-felt cathode for the treatment of aqueous solutions of four triphenylmethane dyes (TPMs), namely malachite green (MG), crystal violet (CV), methyl green (MeG) and fast green FCF (FCF), at pH 3.0 and room temperature. MG has been used as a model among them to study the influence of some experimental parameters on the decay kinetics, COD removal and current efficiency. The results in such electro-Fenton system are explained in terms of the many parasitic reactions involving .OH. Higher efficiency values are obtained with rising organic content and decreasing applied current. The first stage of the mineralization process, involving aromatic by-products, leads to fast decoloration as well as quick initial COD removal that fit well to a pseudo-first-order kinetics. At prolonged electrolysis time, the mineralization rate and efficiency decrease due to the formation of hardly oxidizable compounds and the enhancement of wasting reactions. Solutions of all four TPMs are quickly degraded following a pseudo-first-order decay kinetics. The absolute rate constant (kTPM) for their reaction with .OH increases in the order MeG相似文献   

Mineralization of paracetamol in aqueous medium by anodic oxidation with a boron-doped diamond electrode

The degradation of 100ml of solutions with paracetamol (N-(4-hydroxyphenyl)acetamide) up to 1 g l(-1) in the pH range 2.0-12.0 has been studied by anodic oxidation in a cell with a boron-doped diamond (BDD) anode and a graphite cathode, both of 3-cm2 area, by applying a current of 100, 300 and 450 mA between 25 and 45 degrees C. Complete mineralization is always achieved due to the great concentration of hydroxyl radical (*OH) generated at the BDD surface, with release of NH4+ and NO3- ions. The mineralization rate is pH-independent, increases with increasing applied current and temperature, but decreases when drug concentration raises from 315 mg l(-1). Reversed-phase chromatography revealed a similar complex paracetamol decay in acid and alkaline media. Ion-exclusion chromatography allowed the detection of oxalic and oxamic acids as ultimate carboxylic acids. When the same solutions have been comparatively treated with a Pt anode, a quite poor mineralization is found because of the production of much lower *OH concentration. Under these conditions, the degradation rate is enhanced in alkaline medium and polymerization of intermediates is favored in concentrated solutions. Paracetamol can be completely destroyed with Pt and its kinetics follows a pseudo-first-order reaction with a constant rate independent of pH.     

Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization,rate-constant determination and carbofuran degradation pathway analysis

Carbofuran (CBF) removal in a continuous-flow photocatalytic reactor with granular activated carbon supported titanium dioxide (GAC-TiO₂) catalyst was investigated. The effects of feed flow rate, TiO₂ concentration and addition of supplementary oxidants on CBF removal were investigated. The central composite design (CCD) was used to design the experiments and to estimate the effects of feed flow rate and TiO₂ concentration on CBF removal. The outcome of CCD experiments demonstrated that reactor performance was influenced mainly by feed flow rate compared to TiO₂ concentration. A second-order polynomial model developed based on CCD experiments fitted the experimental data with good correlation (R² ～ 0.964). The addition of 1 mL min^?1 hydrogen peroxide has shown complete CBF degradation and 76% chemical oxygen demand removal under the following operating conditions of CBF ～50 mg L^?1, TiO₂ ～5 mg L^?1 and feed flow rate ～82.5 mL min^?1. Rate constant of the photodegradation process was also calculated by applying the kinetic data in pseudo-first-order kinetics. Four major degradation intermediates of CBF were identified using GC-MS analysis. As a whole, the reactor system and GAC-TiO₂ catalyst used could be constructive in cost-effective CBF removal with no impact to receiving environment through getaway of photocatalyst.     

Electrochemical advanced oxidation processes: today and tomorrow. A review

In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical (^?OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which ^?OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which ^?OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.     

Oxidation of artificial sweetener sucralose by advanced oxidation processes: a review

Sucralose, a chlorinated carbohydrate, has shown its increased use as an artificial sweetener and persistently exists in wastewater treatment plant effluents and aquatic environment. This paper aims to review possible degradation of sucralose and related carbohydrates by biological, electrochemical, chemical, and advanced oxidation processes. Biodegradation of sucralose in waterworks did not occur significantly. Electrochemical oxidation of carbohydrates may be applied to seek degradation of sucralose. The kinetics of the oxidation of sucralose and the related carbohydrates by different oxidative species is compared. Free chlorine, ozone, and ferrate did not show any potential to degrade sucralose in water. Advanced oxidation processes, generating highly strong oxidizing agent hydroxyl radicals (^?OH), have demonstrated effectiveness in transforming sucralose in water. The mechanism of oxidation of sucralose by ^?OH is briefly discussed.     

Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed.     

Enhanced removal of tetracycline via advanced oxidation of sodium persulfate and biochar adsorption

Advanced oxidation of antibiotic tetracycline (TC) is becoming an accessible and efficient technology. The removal of TC from the complex wastewater needs to be lucubrated. In this study, a TC removal system involving degradation and adsorption was established. TC degradation was accomplished by enhanced advanced oxidation via the addition of sodium persulfate (SP) and biochar into simulated wastewater containing Mn²⁺ and TC wastewater. The adsorption of TC and its derivatives was removed by biochar. The results indicate that the optimized reaction parameters were 3.0 g/L of biochar prepared at 600 °C (B600) and 400 mg/L of SP under acidic condition, and the removal percentage of TC was 87.48%, including 74.23% of degradation and 13.28% of adsorption; the anions Cl^?, NO₃^?, and H₂PO₄^? had negligible effects on the removal of TC in this Mn²⁺/B600/SP system. The system also functioned well with an aqueous solution with a high chemical oxygen demand (COD) concentration. Electron paramagnetic resonance (EPR) analysis indicated that ·OH and SO₄^? free radicals were present in the Mn²⁺/B600/SP system. Based on the testing and analysis results, a removal mechanism and potential TC degradation pathway for this system were proposed. TC can be degraded by ·OH and SO₄^? via three degradation pathways. Mn²⁺ can be precipitated as MnO₂, and a part of the TC and its derivatives can be adsorbed on the biochar surface. The Mn²⁺/B600/SP system also performed satisfactorily for a complex aqueous solution with various cations and antibiotics.

     

Anodic oxidation of benzoquinone using diamond anode

The anodic degradation of 1,4-benzoquinone (BQ), one of the most toxic xenobiotic, was investigated by electrochemical oxidation at boron-doped diamond anode. The electrolyses have been performed in a single-compartment flow cell in galvanostatic conditions. The influence of applied current (0.5–2 A), BQ concentration (1–2 g dm^?3), temperature (20–45 °C) and flow rate (100–300 dm³ h^?1) has been studied. BQ decay kinetic, the evolution of its oxidation intermediates and the mineralization of the aqueous solutions were monitored during the electrolysis by high-performance liquid chromatograph (HPLC) and chemical oxygen demand (COD) measurements. The results obtained show that the use of diamond anode leads to total mineralization of BQ in any experimental conditions due to the production of oxidant hydroxyl radicals electrogenerated from water discharge. The decay kinetics of BQ removal follows a pseudo-first-order reaction, and the rate constant increases with rising current density. The COD removal rate was favoured by increasing of applied current, recirculating flow rate and it is almost unaffected by solution temperature.     

Accelerated photo-transformation of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) in water by dissolved organic matter

The ubiquitous dissolved organic matter (DOM) has an important influence on transformation of organic contaminants through the production of reactive substances, such as ^?OH, ¹O₂, and ³DOM*. The photolysis of a higher chlorinated polychlorinated biphenyl (PCB) congener (2,2′,4,4′,5,5′-hexachlorobiphenyl, PCB 153) under simulated sunlight in presence of humic acid (HA) was investigated. Degradation of PCB 153 was accelerated significantly by the addition of HA, with a rate constant of 0.0214, 0.0413, and 0.0358 h^?1 in the initial 18 h of irradiation in presence of 1, 5, and 20 mg/L HA, respectively. The main photodegradation products analyzed by gas chromatography mass spectrometry were 4-hydroxy-2,2′,4′,5,5′-pentaCB and 2,4,5-trichlorobenzoic acid. Main reactive species involved were determined by the electron spin-resonance spectroscopy, including ¹O₂ and ^?OH. Special scavengers were added to elucidate the photolysis mechanisms. By using the specific scavengers, it turned out that ^?OH accounted for 29.3 % of the degradation, and the intra-DOM reactive species (¹O₂, ^?OH, and ³DOM*) accounted for 59.6 % of the degradation. Photo-transformation sensitized by DOM, which involves both aqueous and intra-DOM reactions of PCBs with reactive species, may be one of the most important mechanisms for natural attenuation of PCBs.     

Treatment of Basic Red 29 dye solution using iron-aluminum electrode pairs by electrocoagulation and electro-Fenton methods

The aim of this study is the treatment of Basic Red 29 (BR29) dye solution using hybrid iron-aluminum electrodes by electrocoagulation and electro-Fenton methods. The effect of current density, initial pH, supporting electrolyte, H₂O₂, and initial dye concentration on dye removal efficiency was investigated, and the best experimental conditions were obtained. Time-coarse variation of UV-Vis spectra and toxicity and chemical oxygen demand (COD) removal were also examined at the best experimental conditions. Both systems were found very successful for the removal of BR29 dye. The removal efficiency of >95 % for BR29 dye solution was reached easily in a short time. At the best experimental conditions, for the initial BR29 concentration of 100 mg/L, >95 % BR29 dye and 71.43 % COD removal were obtained after 20 and 40 min of electrolysis, respectively. Additionally, toxicity results for electro-Fenton treatment of 100 mg/L BR29 were also very promising. According to the results obtained, although electro-Fenton is more effective, both systems can be used successfully to treat textile wastewater including dyes.     

Recent updates on electrochemical degradation of bio-refractory organic pollutants using BDD anode: a mini review

Boron-doped diamond (BDD) is playing an important role in environmental electrochemistry and has been successfully applied to the degradation of various bio-refractory organic pollutants. However, the review concerning recent progress in this research area is still very limited. This mini-review updated recent advances on the removal of three kinds of bio-refractory wastewaters including pharmaceuticals, pesticides, and dyes using BDD electrode. It summarized the important parameters in three electrochemical oxidation processes, i.e., anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) and compared their different degradation mechanisms and behaviors. As an attractive improvement of PEF, solar photoelectro-Fenton using sunlight as UV/vis source presented cost-effectiveness, in which the energy consumption for enrofloxacin removal was 0.246 kWh/(g TOC), which was much lower than that of 0.743 and 0.467 kWh/(g TOC) by AO and EF under similar conditions. Finally the existing problems and future prospects in research were suggested.     

Rapid dye degradation with reactive oxidants generated by chloride-induced peroxymonosulfate activation

Transition-metal is known to catalyze peroxymonosulfate (PMS) decomposition to produce sulfate radicals. Here we report reactions between PMS and chloride, without a need of transition metals, also can be used to degrade organic dye pollutant (Rhodamine B, (RhB)). Some important operating parameters, such as dosages of PMS and Cl^?, pH of solution, temperature, ionic strength, and several common cations, were systematically investigated. Almost complete decoloration of RhB was achieved within 5 min ([PMS]?=?0.5 mM, [Cl^?]?=?120 mM, and pH 3.0), and RhB bleaching rate increased with the increased dosages of both PMS and chloride ion, following the pseudo-first-order kinetic model. However, the total organic carbon (TOC) removal results demonstrated that the decoloration of RhB was due to the destruction of chromophore rather than complete degradation. RhB decoloration could be significantly accelerated due to the high ionic strength. Increasing of the reaction temperature from 273 K to 333 K was beneficial to the RhB degradation, and the activation energy was determined to be 32.996 kJ/mol. Bleaching rate of RhB with the examined cations increased with the order of NH₄ ⁺?<?Na⁺?<?K⁺?<?Al³⁺?<?Ca²⁺?<?Mg²⁺. Some major degradation products of RhB were identified by GC-MS. The present study may have active technical implications for the treatment of dyestuff wastewater in practice.