Removal Of Catechol Research Articles

Sequential Electrochemical and Chemical Multi-Polymerization of Catechol for Abatement of Environmental Pollutants

Catechol is a substance that is commonly found in wastewaters from a variety of sectors including paper, paint, petroleum, dyes, antioxidants, pesticides, iron and steel, solvents, nylon, detergent, textile, plastic, rubber, cosmetics, and medicine. In this study, sequential electrochemical and chemical multi-polymerization of catechol was investigated for environmental pollution abatement. The effect of operating parameters like catechol concentration (2–10 g/L), ammonium persulphate (APS) concentration (2–10 g/L) and reaction temperature (20–60 °C) were evaluated using response surface methodology. Catechol concentration was determined using HPLC in a gradient mobile phase. The electrochemical behavior of the polymer was investigated by cyclic voltammetry (CV). The structural and morphological properties of polycatechol were characterized by Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive X-ray (SEM–EDX) analysis. It was observed from the SEM images a polymeric structure developed from a crystalline and heterogeneous structure when the APS concentration increased. Similarly, it was seen in SEM images that the polymers transitioned from a bulk and heterogeneous structure to a homogeneous structure as the temperature increased, and back to a heterogeneous structure as the catechol concentration increased. It was also found that catechol removal increased and reaction selectivity decreased by increasing the reaction temperature. The optimum operating conditions were found as 4 g/L catechol concentration, 9.5 g/L APS concentration, 30 °C reaction temperature with 100 cycles at 50 mV/s of electrochemical polymerization and 72 h of chemical polymerization. The results of this study show the potential of challenging new routes not only facile polymerization of organic monomers but also to decrease the undesirable pollutant concentration in the wastewater.

Adsorption of dihydroxybenzene isomers over Schiff-based network-1-derived nitrogen-enriched carbon: Effective and favorable adsorption of hydroquinone

Urbanization and modernization through intense industrial activity led to the disposal of harmful and non-biodegradable organic substances including dihydroxybenzene isomers such as hydroquinone, catechol, and resorcinol. A covalent-organic polymer Schiff-based network-1, SNW1 was synthesized, pyrolyzed, and subsequently carbonized again, after mixing with KOH, at 800 °C. The obtained carbon, prepared in two-step-carbonization (named as SNW1-2DC), was applied to the adsorption of dihydroxybenzene isomers; showed remarkable performance in hydroquinone adsorption with the maximum adsorption capacity (Q0) of 1060 mg/g at neutral conditions. This Q0 is 6.0 and 5.5 times that of activated carbon and the carbon obtained from the simple pyrolysis of SNW1, respectively; of note, this value represents the highest compared to any previously reported findings. Moreover, the regenerated adsorbent, with simple ethanol washing, performed well for up to 5 cycles. This material could be suggested as a promising adsorbent in hydroquinone removal from water. The adsorption mechanism, including hydrogen bonding, could be suggested. Interestingly, the performance of SNW1-2DC in the adsorptive removal of catechol and resorcinol was very low in comparison with that of hydroquinone. The relative adsorption performances of SNW1-2DC for dihydroxybenzene isomers could be explained with density functional theory calculation and thermodynamic parameters. The most favorable hydroquinone adsorption (among the three dihydroxybenzene isomers) over SNW1-2DC might be because of less endothermic adsorption and more effective H-boning interaction between hydroquinone and SNW1-2DC than that between catechol or resorcinol and the adsorbent.

Effect of pH on degradation and mineralization of catechol in calcium-aid ozonation: Performance, mechanism and products analysis

Catechol, common in industrial wastewater, is very toxic and non-biodegradable, and its desirable removal is still a challenge. Catalytic ozonation as an effective advanced oxidation process, however was limited by the application of intricately fabricated catalysts. Herein, catalytic ozonation by OH– (generated by common sodium hydroxide) with the aid of calcium was developed for catechol degradation and mineralization in this study. The removal performance, mechanism and products were investigated. The results showed that ozonation at pH 12.5 could achieve complete catechol removal and excellent mineralization (maximum of 75 % COD removal efficiency) within 15 min. The adorable effect of calcium for enhanced organics removal was observed at pH 12.5, with the formation of precipitates as well. Catechol and COD removal were fitted to the pseudo-first-order kinetic model, while the reaction constant was increased by higher pH and calcium concentration. The results of quenching experiment and EPR affirmed •OH and •O2– radicals were pivotal for the enhanced organics removal. In addition, DFT calculation revealed the O atoms were reactive sites for electrophilic and radical attack via molecular electrostatic potential, highest occupied molecular orbital, lowest unoccupied molecular orbital and Fukui index. UPLC-Q-TOF-MS analysis revealed the intermediate products and verified the brilliant performance of catalytic ozonation. According to reactive sites and intermediates identification, the degradation pathway of catechol was proposed. As tawny precipitate appeared after reaction, the characteristics of insoluble product was analyzed using FTIR, XRD and XPS. The component of the precipitate was recognized as calcium oxalate and calcium carbonate, accompanied by the decreased Ca2+ concentration at high pH, which declared the enhanced removal was linked to the precipitation of Ca2+. Finally, toxicity assessment stated the lower acute toxicity, bioconcentration factor, developmental toxicity and mutagenicity of intermediates, indicating that calcium-aid ozonation catalyzed by high pH was useful for both catechol degradation and toxicity reduction. This study provides a reference for understanding the performance and mechanism of catechol degradation. More importantly, as an environmentally friendly process, catalytic ozonation possesses a great application potential for treatment of wastewater containing metal ions in terms of simultaneous removal of organics and metal ions.

Multifunctional CuS-based micro-flower loaded with carbon dots/laccase for effectively detection and removal of catechol

The miniaturization and autonomous mobility of the artificial micro-composite have gained widespread interest and attention in the field of catechol treatment. Unfortunately, it is a bottleneck for micro-composite in realizing the integration of multiple functions such as colorimetric detection and removal of catechol. Herein, we construct a Janus micro-composite with dual functions of detection and degradation for the efficient detection and removal of catechol. The Janus micro-composite for laccase immobilization was prepared by growing manganese dioxide nanoparticles (MnO2 NPs) on the hemisphere of copper sulfide (CuS) loaded with carbon (C) dots (Lac-MnO2@C@CuS). The half-coated MnO2 NPs is used as a power source to generate oxygen (O2), which drives the Janus micro-composite for autonomous directional motion at a speed of 178.83 ± 2.07 μm/s in the presence of 5 wt% H2O2. The Janus micro-composite with excellent peroxidase-like properties could display sensitive detection of catechol with the detection limits of 0.49 μM in range of 0–100 μM. Furthermore, the Janus micro-composite could decompose H2O2 to produce abundant reactive oxygen species (ROS) through Fenton reaction, which could promote the removal rate of catechol up to 96.6%. This is a promising micro-composite platform for integrated autonomous movement and simultaneous detection/removal of catechol, which can provide a new perspective for water environment treatment.

Simultaneous removal of catechol and Cr(VI) from tannery wastewaters through Fe(III)-mediating electron transfer

Cr(VI) and catechol are common pollutants in wastewaters of tannery industry. Cr(VI) reduction by catechol results in accumulation of Cr(V)-complex and toxic o-benzoquinone. Cr(VI) reduction can be enhanced by accelerating the electron transfer from catechol to Cr(VI) using Fe(III). This electron transfer allows the continuous production of reactive oxygen species (ROS) in advanced oxidation processes, which further degrades catechol. However, the effects of catechol on Fe(III)-based Cr(VI) reduction and ROS production are not clear. In this study, the electron transfer pathway between catechol, Fe(III) and Cr(VI) was investigated along with the catechol degradation by ROS. Results show that the process of Cr(VI) reduction follows well a pseudo-second-order kinetic model, and the activation energy decreases by 4189 J/mol after electrons are transferred by Fe(III). Aqueous chromium (50 mg/L) was completely precipitated as Cr(OH)3, FexCr1-x(OH)3 or Fe(OH)3-Cr(OH)3 at Fe(III) concentration of 10 mmol/L. Residual catechol and Fe(II) in wastewater activated percarbonate, thereby producing OH for over 480 min at pH 3.0 and generating OH and CO3− for over 5 min at pH 10.0. Catechol was degraded by these ROS to butenedioic, oxalic, and formic acids, which were then mineralized to H2O and CO2. Catechol (2 mmo/L) was fully removed from wastewater with TOC removal of 37%, and the degradation was not affected by SO42− and Cl−. This study provides new insights into the removal of pollutants from wastewaters via electron transfer mediated by Fe(III), and may aid in controlling the toxic effects of Cr(VI) and catechol-like organics in natural and engineered aquatic systems.

Using innovative copper-loaded activated alumina (Cu/AA) as the catalyst for catalytic wet peroxidation (CWPO) of catechol.

In this study, copper-loaded activated alumina (Cu/AA) was synthesized and used for the CWPO of catechol (a representative refractory organic pollutant).Various characterization techniques were deployed to characterize the catalysts, e.g., activated alumina (AA), as well as pristine and spent 1% Cu/AA. The innovative 1% Cu/AA catalyst exhibited good thermal stability up to 1173K with a marginal weight loss of 13%. The Cu species were well dispersed on the activated alumina framework with no significant cluster formation. Typically, the average copper particle size of 5nm was dispersed on the AA framework. Catechol removal was observed to be 92% with 87% mineralization at optimizedconditions (initial catechol concentration = 200mg/L, catalyst dose of 1% Cu/AA = 2g/L; temperature = 323K; pH = 6; and H2O2/catechol stoichiometric ratio = 0.5). The mineralization of catechol was analyzed using mass spectroscopy, with the associated mechanism has been elucidated. Results of this study indicated that synthesized catalyst has phenomenal advantages in terms of simple separation and high removal efficiency of catechol, suggesting the feasibility of employing Cu/AA as the effective catalyst for the CWPO of catechol.

3D hierarchical LDHs-based Janus micro-actuator for detection and degradation of catechol.

Micro/nanomotors that combine the miniaturization and autonomous motion have attracted much research interest for environmental monitoring and water remediation. However, it is still challenging to develop a facile route to produce bifunctional micromotors that can simultaneously detect and remove organic pollutants from water. Herein, we developed a novel Janus micromotor with robust peroxide-like activity for simultaneously colorimetric detection and removal of catechol from water. Such laccase (Lac) functionalized Janus micromotor consisted of calcined MgAl-layered double hydroxides (MgAl-CLDHs) nanosheets and Co3O4-C nanoparticles (Lac-MgAl-CLDHs/Co3O4-C), revealing unique 3D hierarchical microstructure with highly exposed active sites. The obtained Janus micromotors exhibited autonomous motion with a maximum velocity of 171.83±4.07µm/s in the presence of 7wt% H2O2 via a chemical propulsion mechanism based on the decomposition of H2O2 by Co3O4-C layer on the hemisphere surface of Janus micromotors. Owing to the combination of autonomous motion and high peroxide-like activity, Lac-MgAl-CLDHs/Co3O4-C Janus micromotors could sensitively detect catechol with the limit of detection of 0.24μM. In addition, such Janus micromotors also could quickly degrade catechol by •OH generated from a Fenton-like reaction. It is a first step towards using autonomous micromotors for highly selective, sensitive, and facile detection and quick removal of catechol from water.

The removal efficiency and reaction mechanism of the aluminum coagulant on phenolic compounds in the presence of hardness salts

This study is the evaluation of the coagulation efficiency of the aluminum sulfate on the removal of catechol and pyrogallol. The study has focused on the impact of inorganic components of hardness Algerian waters. Jar-test trials were conducted on the two phenolic compounds dissolved in distilled water only, which was later enriched with minerals. Several reaction parameters varied, including the effect of pH and the influence of the salt content, and this approach yielded a better understanding of interaction between phenolic compounds and calcium/magnesium salts. The results indicate that the process efficiency depends on the number and position of OH in molecules. The main mechanisms would be either a physical adsorption, an exchange of ligand, or complexation on the floc surface of aluminum hydroxide. Moreover, the addition of inorganic salts appears to improve removal efficiency of tested phenolic compounds and have an effect on the optimal pH range for coagulation.

Delafossite-alumina nanocomposite for enhanced catalytic wet peroxide oxidation of anionic pollutants

Mass transfer efficiency and catalytic reactivity are the two major hurdles for heterogeneous catalytic wet peroxide oxidation (CWPO) technologies. To address these issues, nanocomposite CuFeO2/Al2O3 was synthesized and assessed as a novel catalyst for enhanced adsorption and oxidation of anionic pollutants (catechol and reactive red 195 (RR195)) in waters. With a positive charge on the nanocomposite by introducing Al2O3, the adsorption of anionic pollutants was promoted. The surface complexation reaction on CuFeO2/Al2O3, which fits well to the Langmuir isotherm, has engined the mass transfer of pollutants to the nanocatalyst that demonstrated 96.46% and 99.75% removal of catechol and RR195 at pH 3, respectively. CuFeO2/Al2O3 also showed good performance in various reaction media including binary pollutants system and real wastewaters. The hydroxyl radical in aqueous solution played a major role in the pollutants degradation. The CWPO, which followed the Haber-Weiss mechanism, has been accelerated by the Cu and Fe redox cycles. The robustness of the catalyst was verified by negligible amount of metal leaching from the catalysts along with stable catalytic performance after five cycles. Upon the observed results, CuFeO2/Al2O3 with the synergistic effect has shown to be a promising catalyst for removal and degradation of anionic pollutants in CWPO.

Evaluate the effectiveness of the UV/ persulfate process to remove catechol from solution aqueous

<p>Catechol is used as an antioxidant, fungicide, and polymerization inhibitors in a variety of industries such as petrochemical. Catechol must be removed from effluents before it enters to environment. This study aimed to investigate combined UV radiation and persulfate process in removal of catechol from aqueous solutions. All experiments were performed in a batch reactor. Data analysis were done with Design of Experiment (DoE) software. The effects of various variables such as pH, initial persulfate concentration, and initial Catechol concentration were investigated. The findings indicated with increases in persulfate concentration and decrease in catechol concentrations, the removal efficiency increased. Acidic pH and UV radiation were the leading factors in removal of catechol. The optimum pH, persulfate concentration, and catechol concentration were obtained 7, 0.04 M, and 100 mg l-1, respectively. More removes of catechol was achieved in optimum conditions within contact time of 60 min. The synergic effects of UV and persulfate radical were about 88%. Approximately 60% of catechol was mineralized within contact time of 60 min. Persulfate radicals resulting from UV/S2O82- were the main effective oxidants in removal and mineralization of catechol. Owing to high removal efficiency of persulfate compounds which are, also, abundant and inexpensive, these can be applied in removal of persistent organic pollutants from aqueous solutions.</p>

Removal of catechol and hydroquinone by ground corncob monitored electrochemically with a palladium/poly(1,2-diaminoanthraquinone)/glassy carbon modified electrode

ABSTRACT The adsorption behaviours of phenolic isomers, catechol (CC) and hydroquinone (HQ), on an inexpensive adsorbent, corncob, were studied. The optimum conditions required for the extractions of CC and HQ from aqueous media by the ground corncob were comprehensively studied. Further, the concentrations of CC and HQ were electrochemically determined with a palladium nanoparticles/poly(1,2-diaminoanthraquinone)/glassy carbon modified electrode (PdNPs/p1,2-DAAQ/GC/ME) by a square wave voltammetry technique in 0.05 M perchloric acid. It was confirmed that the maximum uptakes of 100 ppm CC and 100 ppm HQ were obtained at pH 8 and shaking time of 1.5 h with an adsorbent (corncob) dose of 0.1 g. The adsorptions of CC and HQ by ground corncob followed the second- and first-order models determined by the Freundlich adsorption isotherm, respectively. Corncob effectively adsorbed phenolic compounds from wastewater.

Photodegradation of catechol in water over magnetically separable Fe3O4/TiO2 composite photocatalysts

ABSTRACT Catechol is a serious polluter for effluents released from different industrial sectors. This compound is toxic and persistent under environmental conditions. The purpose of the current research was to evaluate the photocatalytic degradation of catechol by using the illuminated Fe3O4/TiO2 nanoparticles at some catalyst dosages, pHs, catechol concentrations, purging gases, H2O2 contents, organic materials. The results of the FT-IR and XRD analyses indicated the combination of the Fe3O4 and TiO2nanoparticles.The one-factor-at-a-time (OFAT) method was used to study the kinetics and the impacts of some key variables. In order to investigate the photocatalytic decomposition of catechol, a solution containing catechol and the Fe3O4-TiO2 nanocomposite was made and allowed to reach the equilibration within 30 min. Magnet was permanently done for 3 min to separate the nanocomposite from the mixture solution. Catechol contents were detected by HPLC through a calibration curve which was indicated according to the Beer–Lambert law. Under the optimum conditions pH 3, [catechol]0 50 mg/L, nanocatalyst dose 0.5 g/L, H2O2 content 5 mM, all of the pollutant was decomposed over 60 min. kobs increased between 0.0029 and 0.0004 min−1 with enhancing catechol content (10 to 200 mg/L). Photocatalytic studies showed o-Benzoquinone, 1,2,3-trihydroxybenzene, 1,2,4-trihydroxybenzene and organic acids to be the main degradation products of catechol in aqueous solution. The electrical-energy consumption for the photocatalytic removal of catechol using the UV/Fe3O4/TiO2 method was lower than those of the UV/Fe3O4, UV/TiO2 and UV processes. Also, the efficiency increased with the addition of H2O2 in comparison with ambient conditions. Moreover, organic compounds presented an inhibition effect on the removal efficiency.

Ultrasonic-assisted H2O2/TiO2 process in catechol degradation: kinetic, synergistic and optimisation via response surface methodology

ABSTRACT This experimental study investigated the performance of Catechol degradation by US/TiO2/H2O2 process as an integrated advance oxidation process. In this experimental study, initial pH, dose of TiO2, initial concentration of Catechol, H2O2 concentration and reaction time parameters optimised BBD. The results suggest that US/TiO2/H2O2 process has a high efficiency in Catechol degradation. Optimum condition of US/TiO2/H2O2 process is pH = 3.43, H2O2 concentration = 130 mg/l, TiO2 dose = 0.34 g/l, Catechol concentration = 12.52 mg/l and reaction time = 70.64 min. According to predicate point, the percentage of Catechol removal in this condition was 96.2 and 92.34 as a predicated and experimental percentage of Catechol removal by this process. The kinetics of reaction follows pseudo-first-order kinetic. The synergist effect of sonolysis, TiO2 and H2O2 is 2.09 fold. 70 and 63% of initial COD and TOC were removed. Presence of radical scavenger has an adverse impact on the performance of US/TiO2/H2O2 process.

Synthesis and Characterization of TiO2-CaO and TiO2-CaO-Fe2O3 Photocatalyst for Removal of Catechol

TiO2-CaO and TiO2-CaO-Fe2O3 photocatalysts have been synthesized through the surfactant-assisted sol-gel method. The catalysts were characterized using XRD, FTIR, SEM-ED Sand BET surface area. XRD pattern showed the formation of anatase TiO2 crystal phase both in TiO2-CaO and TiO2-CaO-Fe2O3. The TiO2-CaO has higher crystallinity than TiO2-CaO-Fe2O3. Based on the peak refinement using Rietveld, there are two peaks identified as Fe2O3 hematite in the sample TiO2-CaO-Fe2O3. BET surface area analysis showed that the average pore size of TiO2-CaO and TiO2-CaO-Fe2O3 catalysts are 8.04 and 8.41 nm respectively, indicating both catalysts are mesoporous.FTIR spectra show that the vibration of Ti-O, Ca-O, and Ca-TiO2 were observed in both catalysts. SEM images confirm that both catalysts are porous material. The catechol removal using TiO2-CaO and TiO2-CaO-Fe2O3 improved with the increase of catalyst concentration. After 360 minutes of UV radiation, the removal of catechol using TiO2-CaO-Fe2O3 reached 46.0%, 48.3%, and 69.2%, while when using TiO2-CaO, it reached 22.1%, 36.8%, and 57.0% for 0.1 g, 0.15 g, and 0.2 g of catalysts, respectively. The photocatalytic activity of TiO2-CaO-Fe2O3 is not so strong compared to TiO2-CaO catalyst but the catechol adsorption property of TiO2-CaO-Fe2O3 is higher than that of TiO2-CaO catalyst.

Thiol-Ene Click Synthesis of Phenylboronic Acid-Functionalized Covalent Organic Framework for Selective Catechol Removal from Aqueous Medium.

We report a thiol-ene click strategy for the preparation of a novel phenylboronic acid-functionalized covalent organic framework (COF) for selective removal of catechol in aqueous solution. Vinyl-functionalized 2,5-diallyloxyterephthalaldehyde (Da-V) was prepared as a building ligand. Da-V was then condensed with 1,3,5-tris(4-aminophenyl)benzene (Tab) to give a vinyl-functionalized COF DhaTab-V. Subsequently, 4-mercaptophenylboronic acid (4-MPBA) was covalently linked on DhaTab-V via thiol-ene click reaction to give phenylboronic acid-functionalized COF DhaTab-PBA. The adsorption isotherms, energetics and kinetics, and reusability of DhaTab-PBA for the adsorption and removal of catechol from aqueous solution were investigated in detail. This phenylboronic acid-functionalized COF is promising as sorbent for selective removal of catechol from aqueous medium with large adsorption capacity and good reusability.

Adsorptive Removal of Catechol from Aqueous Solution with a Water-Stable and Hydroxyl-Functionalized Terbium–Organic Framework

Nowadays, water pollution caused by diverse poisonous compounds, particularly hydroxy aromatic compounds and their derivatives, has become a prominent environmental issue because of the possible toxicity to human beings. This research adopted an adsorptive method to remove catechol using a water-stable hydroxyl-functionalized terbium–organic framework for the first time. The as-synthesized new metal–organic framework (Tb–MOF) shows favorable thermostability and water stability based on results of thermogravimetric analyses, water vapor sorption, and powder X-ray diffraction. Along the c axis, Tb–MOF has a three-dimensional framework with channels of 8.4 × 8.1 A2 as well as high adsorption capacity with the maximal adsorption capacities of 260 mg/g for catechol than that of any reported adsorbent so far. Thermodynamics, adsorption kinetics, effects of pH, and effects of temperature were investigated in a batch reactor. The remarkably high adsorption capacity of Tb–MOF could be explained by the appropriate ...

Efficient Fe/CuFeO2/rGO nanocomposite catalyst for electro‐Fenton degradation of organic pollutant: Preparation, characterization and optimization

The nanocomposite of zero‐valent iron and delafossite CuFeO2 supported on reduced graphene oxide was synthesized for the first time to evaluate its performance as the heterogeneous catalyst toward electro‐Fenton (EF) removal of catechol. X‐ray diffraction, Fourier transform‐infrared, scanning electron microscopy and Brunauer–Emmett–Teller (BET) were used to characterize the nanocomposite. It was found that the rhombohedral structure of CuFeO2 remained stable during the nanocomposite preparation. The BET surface area of the nanocomposite increased about 102 times in comparison with bare CuFeO2. The influence of the operating parameters was investigated. The optimum operating conditions were pH 3, Fe/CuFeO2/rGO: 1 g/l; catechol: 7.5 × 10−4 mol/l; and I: 150 mA, which led to 99% and 78.4% catechol and chemical oxygen demand removal in 120 min, respectively. The stability of the catalyst by leaching measurements was studied. Only 2% and 3.1% of iron and copper, respectively, was leached in the solution. The obtained results introduced Fe/CuFeO2/rGO as a stable and appropriate catalyst for removal of organic compounds by the EF process. It was inferred from the scavenger utilization that hydroxyl radical plays a major role in catechol elimination and EF reaction followed by the Haber–Weiss mechanism at optimum conditions. The gas chromatography–mass spectrometry analysis was performed to detect the intermediate products, and an acceptable degradation pathway was proposed. The EF degradation of catechol follows a pseudo‐first‐order kinetics model with a rate constant of 3.69 × 10−2 min−1 for the optimum operating conditions. The reusability of Fe/CuFeO2/rGO was investigated for six cycles, and the catalytic efficiency almost remained.

Preparation, characterization and environmental application of the composite electrode TiO2‐NTs/SnO2—Sb with carbon aerogels

AbstractBACKGROUNDResearch on electrode materials with high electrochemical activity is of great importance for the electrochemical oxidation technique. In this work, an electrode comprising titanium dioxide nanotubes with tin oxide antimony (TiO2‐NTs/SnO2—Sb) with carbon aerogels (TSS‐CAs) was fabricated and used to degrade three isomers of dihydroxybenzenes.RESULTSIt was observed that the TSS‐0.5%CAs electrode prepared with 0.5 wt% CAs possessed prominent pore structure and a larger specific surface area of 180.83 m2 g−1. Electrochemical measurements revealed that the TSS‐0.5%CAs electrode had enhanced electrochemical activity, larger electroactive area, and higher oxygen evolution potential. Relevant operational parameters including initial contaminant concentration, pH, electrolyte concentration and current density had significant effects on the electrocatalytic performance of the TSS‐CAs electrode.CONCLUSIONIt was demonstrated that a proper content of carbon aerogel could improve the structure and electrochemical performance of the TSS‐CAs electrode. The removal of catechol was higher than that of hydroquinone and resorcinol during electrochemical oxidation, due to its lower Gibbs free energy barriers. Oxidation of intermediates of dihydroxybenzenes by the TSS‐CAs electrode also was confirmed. © 2019 Society of Chemical Industry

Oxidation-precipitation of magnetic Fe3O4/AC nanocomposite as a heterogeneous catalyst for electro-Fenton treatment

The oxidation-precipitation method was used for the synthesis of Fe3O4/AC. The characterization of the catalyst was accomplished by XRD, FT-IR, FE-SEM, BET, and VSM techniques. The obtained results indicated that magnetite nanoparticles were successfully prepared with cubic spinel structures and uniform distribution on the surface of activated carbon by the oxidation-precipitation method. The effect of operating parameters was evaluated to determine the optimum operating condition for the electro-Fenton (EF) removal of catechol as a phenolic pollutant model. At the optimum operating conditions (pH 3, Fe3O4/AC: 0.9 g L−1, Catechol: 8.0 × 10−4 mol L−1 at I: 120 mA), the catechol and COD removal reached 98.2 and 76.1% in 120 min, respectively. Only 2.1% of ferrous and 3.44% of ferric ions were leached into the solution. Regarding the results from utilization of oxidant scavengers (isopropanol and BQ), it can be inferred that hydroxyl radical (responsible for 57% catechol removal) and superoxide anion radical (responsible for 40% catechol removal) is the main oxidants in acidic (pH 3) and basic (pH 10) conditions, respectively. The kinetics of EF removal of catechol was studied and the rate constant for the pseudo-first-order kinetic model was found to be 3.37 × 10−2min−1 (R2 = 0.9924). The GC-MS analysis was carried out to detect the intermediate products and a possible degradation mechanism was proposed. The reusability of Fe3O4/AC was examined for six cycles. It can be concluded that Fe3O4/AC is an applicable ultimate catalyst for EF removal of organic pollutants.

Correction to: Adsorption, Kinetics and Equilibrium Studies on Removal of Catechol and Resorcinol from Aqueous Solution Using Low-Cost Activated Carbon Prepared from Sunflower (Helianthus annuus) Seed Hull Residues

This study reports on the feasibility of remediation of catechol- and resorcinol-contaminated water using low-cost sunflower seed hull activated carbon (SSHAC). Sunflower seed hull (SSH), an abundant agricultural waste in Malawi, was used as precursor to prepare highly porous activated carbon by physicochemical activation, with zinc chloride (ZnCl2) as an activating agent. The activated carbon was characterized by FTIR, SEM-EDS, XRD and BET analyses. In this work, pertinent parameters that affect the adsorption efficiency—pH, initial adsorbate concentration, contact time, adsorbent dosage, and solution temperature—were investigated in batch mode. At the same experimental conditions, more catechol was adsorbed than resorcinol may be due to the compound’s affinity towards water and the position of the hydroxyl group on the benzene ring. A maximum equilibrium adsorption of 271 and 250 mg/g was obtained at pH 9.0 and pH 8.0 for catechol and resorcinol, respectively. The adsorption behaviour of both adsorbates (catechol and resorcinol) on SSHAC can be well described by Langmuir isotherm model and pseudo-second-order kinetic model. The value ∆G, ∆S and ∆H indicated spontaneous and endothermic adsorption process. The adsorption process was readily reversible allowing reusability of the adsorbate. This study’s outcome is value addition to this category of wastes for environmental protection.