Degradation Of Reactive Black Research Articles

Smart harvesting and in-situ application of piezoelectricity in membrane filtration systems

Fouling remains one of the key challenges in membrane technology. In pressure-driven membrane separations, the vibrational energy induced by hydraulic pumps often dissipates unexploited. We present an innovative concept, in which the hydraulic pressure vibration is converted to electrical energy in the outlet of a filtration pump through an embedded piezoelectric nanogenerator (PENG) ceramic. We found that by increasing the average pressure of the hydraulic pump, the dynamic pressure fluctuation increased. The maximum output voltage of 219.6 V was obtained at 20 psi average pressure. The generated piezoelectricity was directly applied to an electro-assisted membrane cell in either alternating mode or positive/negative rectified form to mitigate membrane fouling. In the first configuration, ultrafiltration (UF) membrane was placed between two metallic electrodes. The optimum fouling resistance was achieved when the positive rectified piezoelectric pole was connected to the electrode. Water flux decline (FD) and water flux recovery ratio (FRR) were improved by 28.6% and 52.1%, respectively, compared to the case where no voltage was applied. In the second configuration, a piece of water-permeable and electro-conductive carbon nanotube (CNT) mat was mounted over the UF membrane and it was connected to the piezoelectric wafer using a wire. The alternating piezoelectricity provided the best antifouling performance in this configuration, with FD of 32.5% and FRR of 78.3%. The generated piezoelectricity was also used as a power source to drive an electro-Fenton (EF) reaction coupled with nanofiltration (NF) for reactive black 5 (RB5) dye separation. The results showed that the highest RB5 degradation rate (8.8%) was achieved when the rectified negative and positive poles were connected to the graphite paper and stainless-steel mesh electrodes, respectively. The proposed piezoelectric energy harvesting can revolutionize the traditional methods of fouling reduction in the electro-membrane processes where an external power should be applied for the oxidation reactions to occur.

Optimization, kinetics, and thermodynamics aspects in the biodegradation of reactive black 5 (RB5) dye from textile wastewater using isolated bacterial strain, Bacillus albus DD1.

This study is aimed to model and optimize the decolorization of reactive black 5 (RB5) dye using Bacillus albus DD1. The response surface methodology (RSM) along with rotatable central composite design (rCCD) is used to optimize the response, % decolorization with four input variables: (i) pH (5-9), initial dye concentration (50-500 ppm), the composition of yeast extract as nitrogen source (0.2-1%) and amount of bacterial inoculum (5-25% v/v). The % decolorization is predicted to be ≈ 98% at the optimized condition (pH = 7.6, dye concentration = 200 ppm, bacterial inoculum = 20 v/v% and yeast extract = 0.4%). Furthermore, the kinetics and thermodynamics of RB5 degradation are also determined. The kinetic order of biodegradation of RB5 is found to follow first-order kinetics with a kinetic rate constant = 0.0384. The activation energy, Ea and frequency factor, A values are calculated as 34.46 kJ/mol and 24,343 (1/Day). A thermodynamic study is also carried out at different temperatures (298 K, 308 K, 310 K, 313 K, and 318 K) using optimized conditions. The values of the ΔH and ΔS are found to be +30.79 kJ/mol, and -0.1 kJ/mol/K, respectively using the Eyring-Polanyi equation. The values of ΔG are also calculated at all temperatures.

Electrically supported mediator Co(II)-activated peroxydisulfate synergistic process for organic contaminants elimination

Among homogeneous catalysts, cobalt ions exhibit ultra-high persulfate activation performance. In this work, an electrically supported medium Co(II) activated peroxydisulfate synergistic process was established to eliminate organic contaminants in water. The synergistic catalytic effect was verified by comparing the oxidative degradation performance and reaction rate constant of different coupling systems. The decolorization ability of E-Co(II)-PDS on reactive black 5 (RB5) was explored, and the results showed that the removal rate of RB5 can reach 93.21% under the optimized conditions of current density of 5.71 mA/cm2, initial pH of 4, Co(II) concentration of 0.2 mM and PDS concentration of 5 mM. The effect of water matrix on the removal of RB5 was studied, and it was found that HCO3− and humic acid significantly inhibited the degradation of RB5, while Cl− and H2PO4− could effectively promote it at a certain concentration. Notably, the degradation of RB5 in E-Co(II)-PDS system achieved lower energy consumption, with an energy consumption per unit volume (EE/O) value of 0.4304 kWh·m−3. EPR test, quenching experiments and contribution rate analysis showed that the oxidation active species in E-Co(II)-PDS process were Co(III), sulfate radicals and hydroxyl radicals, and their oxidation contribution rates were 15.72%, 12.69% and 53.25%, respectively. Finally, the decomposition process of RB5 was proposed by the mass spectrometry results. The electric current promotes cobalt ion cycling and PDS activation through electron transfer, and induces Co(II) to promote the activation of PDS, which is the main mechanism of E-Co(II)-PDS system to achieve the robust degradation ability of RB5.

Evaluation of Fe2+/Peracetic Acid to Degrade Three Typical Refractory Pollutants of Textile Wastewater

In this work, the degradation performance of Fe2+/PAA/H2O2 on three typical pollutants (reactive black 5, ANL, and PVA) in textile wastewater was investigated in comparison with Fe2+/H2O2. Therein, Fe2+/PAA/H2O2 had a high removal on RB5 (99%) mainly owing to the contribution of peroxyl radicals and/or Fe(IV). Fe2+/H2O2 showed a relatively high removal on PVA (28%) mainly resulting from ·OH. Fe2+/PAA/H2O2 and Fe2+/H2O2 showed comparative removals on ANL. Additionally, Fe2+/PAA/H2O2 was more sensitive to pH than Fe2+/H2O2. The coexisting anions (20–2000 mg/L) showed inhibition on their removals and followed an order of HCO3− > SO42− > Cl−. Humic acid (5 and 10 mg C/L) posed notable inhibition on their removals following an order of reactive black 5 (RB5) > ANL > PVA. In practical wastewater effluent, PVA removal was dramatically inhibited by 88%. Bioluminescent bacteria test results suggested that the toxicity of Fe2+/PAA/H2O2 treated systems was lower than that of Fe2+/H2O2. RB5 degradation had three possible pathways with the proposed mechanisms of hydroxylation, dehydrogenation, and demethylation. The results may favor the performance evaluation of Fe2+/PAA/H2O2 in the advanced treatment of textile wastewater.

Efficient removal of azo dyes by Enterococcus faecalis R1107 and its application in simulated textile effluent treatment

This study aimed to exploit the potential of Enterococcus faecalis R1107 in the bioremediation of azo dyes. The maximal decolorization of Congo Red (CR), Reactive Black 5 (RB5), and Direct Black 38 (DB38) were 90.17%, 96.82%, and 81.95%, respectively, with the bacterial treatment for 48 h. 65.57% of CR and 72.64% of RB5 could be decolorized by E. faecalis R1107 within 48 h when the concentration of azo dyes increased up to 1000 mg/L. FTIR analysis confirmed that E. faecalis R1107 could effectively break down the chemical structures of three azo dyes. E. faecalis R1107 alleviated the phytotoxicity of azo dyes and improved seed germination, which contributed to the increase in the lengths of roots, stems, and leaves of Vigna radiata seedlings. Transcriptomic analysis suggested that the gene regulatory networks in E. faecalis R1107 synergistically improved the degradation and detoxification of RB5, including the major metabolic pathways, the secondary metabolism, the transport system, the amino acid metabolic pathways, and the signal transduction systems. Simulated textile effluent (STE) was used to mimic real textile effluent to evaluate the bioremediation potential of E. faecalis R1107, and 72.79% STE can be decolorized after E. faecalis R1107 treatment for 48 h. In summary, our study demonstrated that E. faecalis R1107 might be well suitable for potential applications in the bioremediation of textile effluent.

A brass-mesh structured photoreactor applied in the photocatalytic degradation of RB5 dye

• Brass-mesh structured reactor with large surface area was used for RB5 degradation. • The washcoating technique provided a layer with high content of immobilized catalyst. • The use of solar radiation indicated a photocatalytic efficiency of 67.5%. • The monolith showed good stability after 5 cycles of photocatalytic reaction. • The studied photoreactor is a promising alternative for textile dye degradation. A photocatalytic structured reactor of calcined brass-mesh monolith immobilized with TiO 2 was built for textile dye photodegradation. The photocatalytic efficiency of these materials was investigated at the reactive black 5 (RB5) degradation at a recycle reactor. The effects of feed flow (1, 2, and 3 L h −1 ), pH medium (4, 7, and 9), and the radiation source (solar and artificial) were studied. The results of the tests performed with artificial radiation (UV-A and UV-B) showed that the flow modification did not lead to a significant difference in the degradation of the dye chromophore group, thus proving the structured system characteristics when operating at high flow values. Regarding the radiation type, the use of solar radiation indicated a photocatalytic efficiency of 67.5%. The monolithic systems also showed good stability after 5 consecutive cycles of photocatalytic reaction, maintaining a degradation higher than 80%. It was observed that the toxicity tests of seeds and bacteria illustrated that the products obtained after the photodegradation were not toxic, guaranteeing the quality of water. Based on the results obtained in this work, the brass-mesh monolith consists of an efficient system for RB5 degradation, rising as a promising alternative to textile effluent treatment. Graphical Abstract .

Comparative study of g-C3N4/Ag-based metals (V, Mo, and Fe) composites for degradation of Reactive Black 5 (RB5) under simulated solar light irradiation

In present work, a comparative study on the heterojunction formation between g-C3N4 and a series of Ag-based metal oxides (Ag4V2O7, AgFeO2 and Ag2Mo2O7) catalysts prepared via a facile hydrothermal method was conducted in the degradation of Reactive Black 5 (RB5). HRTEM, XRD, UV–vis, PL results confirmed that Ag-based metal oxides were successfully incorporated into the framework of g-C3N4. The optical properties of the prepared catalysts showed an enhanced light absorption in the visible light region and improved charge carrier’s separation. Photoelectrochemical (PEC) analysis revealed that g-C3N4/Ag2Mo2O7 catalyst possessed remarkably faster charge transport and high conductivity compared to other samples. g-C3N4/Ag2Mo2O7 catalyst exhibited the best photocatalytic RB5 degradation of 96.8% after 50 min of simulated solar light irradiation. The photocatalytic activity followed the trend: g-C3N4/Ag2Mo2O7 > g-C3N4/Ag4V2O7 > g-C3N4/AgFeO2 > g-C3N4, in accordance with the amount •OH radicals determined by fluorescence spectroscopy. Effect of Ag2Mo2O7 loadings revealed that 20 wt% g-C3N4/Ag2Mo2O7 demonstrated the highest photodegradation efficiency of RB5 due to the high formation of •OH radicals in the photocatalytic reaction. The mechanistic study for degradation of RB5 was proposed for the improved photoactivity as evidenced by the radical scavenger’s test. Moreover, the g-C3N4/Ag2Mo2O7 catalyst could be reused several times without significant loss of photoactivity, making it an excellent candidate to be used in wastewater remediation.

Reactive black 5 dyeing wastewater treatment by electrolysis-Ce (IV) electrochemical oxidation technology: Influencing factors, synergy and enhancement mechanisms

Reactive black 5 (RB5) dyeing wastewater poses a serious threat to the water environment safety and biological life health. It is of great significance to use an enhanced type of electrolysis-Ce(IV) electrochemical oxidation technology for the efficient treatment of RB5 dyeing wastewater. In this study, the effects of single-factor experimental conditions such as cerium (Ce) ion concentration, pH, current value, different catalytic systems on RB5 degradation effect in electrolysis-Ce(IV) system were investigated. The experimental results showed a significant synergistic and enhanced effect between the direct electrochemical oxidation process and Ce(IV) treatment alone, and their combination (electrolysis-Ce(IV)) could significantly enhance the RB5 treatment with a removal efficiency up to 91.6%. In addition, the background ions HCO3−, Cl−, PO43− and HA had an inhibitory effect on the electrolysis-Ce(IV) system, whereas Cl− had an enhanced effect. Meanwhile, reasonable energy consumption for the removal of RB5 was achieved in electrolysis-Ce(IV) with a maximum electrical energy per order (EE/O) value of 4.89 kWh·m−3. There are three possible reaction ways for RB5 degradation, and the generated organic intermediates with low molecular weight and biotoxicity, which facilitates further mineralization of the product and biodegradation. In the electrolysis-Ce(IV) system, the driving force for the oxidative removal of RB5 were direct electrochemical oxidation function, Ce(IV) ions and hydroxyl radicals, where direct electrochemical oxidation function and Ce(IV) ions were the key and dominant effect for RB5 removal. Compared with the direct electrochemical oxidation system alone, the Ce(IV) in the electrolysis-Ce(IV) system contributes much to enhancing and improving the RB5 degradation and is the key and core active degradation substance.

Efficient and reusable Cu (II)-metalated silica-based inorganic-organic hybrid catalyst for dye degradation

An efficient silica-based inorganic-organic hybrid was synthesized by using 3-(2-aminoethylamino)propyltrimethoxylsilane as linker and 2-Quinolinecarboxaldehyde for Schiff's base formation which was further coordinated by Cu (II) chloride. The hybrid was characterized by relevant techniques, i.e., FT-IR, DRUV-Vis, SEM, EDX, ICP-AES, TGA and EPR technique which support its formation. The synthesized hybrid material was successfully used as heterogeneous catalyst for degrading Reactive Black-5 (RB-5), a non-biodegradable diazo dye. The degradation mechanism follows advanced oxidation technique utilizing hydrogen peroxide as an environmentally amiable green oxidant; where the hybrid catalyst decomposes H2O2 to generate ·OH free radicals. Effects of dye concentration, H2O2 concentration and temperature variation on dye degradation process were studied and best reaction conditions for maximum degradation of RB-5 were also worked out. The catalyst showed 87% dye degradation in 130 ​min at best reaction conditions. Easy separation, reusability and efficient dye degradation ability of the catalyst are the motivating factors for the development of such hybrid material for solving critical environmental issues.

Magnetic CuNiFe2O4 nanoparticles loaded on multi-walled carbon nanotubes as a novel catalyst for peroxymonosulfate activation and degradation of reactive black 5.

Novel copper-nickel ferrite nanocatalyst loaded on multi-walled carbon nanotube (MWCNTs-CuNiFe2O4) was synthesized and applied to activate peroxymonosulfate (PMS) in the degradation of the reactive black 5 (RB5). The structure of the catalyst was well characterized by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The MWCNTs-CuNiFe2O4/PMS system showed a high performance in the degradation of RB5 with a kinetic rate of 1.5-2.5 times higher than homogeneous and heterogeneous systems. Maximum degradation efficiency (99.60%) was obtained at an initial pH of 7, catalyst dosage of 250 mg/L, PMS dosage of 4 mM, the temperature of 25 °C, and reaction time of 15 min. Anion experiments emphasized that the presence of nitrate, carbonate, and phosphate in the solution reduced the degradation efficiency by producing reactive species with low oxidation potential. The RB5 degradation rate evolved with temperature, and the activation energy was obtained to be 44.48 kJ/mol. The mechanism of PMS activation and production of free radicals was proposed based on tert-butyl alcohol (TBA), ethanol (EtOH), and potassium iodide (KI) scavengers. Trapping experiments showed that both sulfate (SO4•-) and hydroxyl (•OH) radicals are involved in the catalytic degradation of RB5. The effective treatment of real wastewater and tap water by the MWCNTs-CuNiFe2O4/PMS system requires a long reaction time. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that RB5 can be degraded via methylation, decarboxylation, hydroxylation, and ring/chain cleavage pathways. The stable catalytic activity after three consecutive cycles suggested that MWCNTs-CuFe2O4 is a novel reusability catalyst in PMS activation.

Low-cost flow photoreactor for degradation of Reactive Black 5 dye by UV/H2O2, Fenton and photo-Fenton processes: a performance comparison

In this work, a flow photoreactor was designed and set up using low-cost and recyclable parts to develop chemical treatments based on advanced oxidation processes (AOP) of highly colored textile wastewater. To evaluate this sustainable system´s efficiency, we investigated and compared the performance of three types of destructive methods (UV/H2O2, Fenton, and photo-Fenton) on the decolorization of aqueous solutions of Reactive Black 5 dye (RB5). We also analyzed the effect of the oxidant and dye concentrations on the rate of color removal in each one of the three methods. The results showed that, regardless of the initial operating conditions, the photo-Fenton process achieved the highest degradation rates, particularly when the highest ratio between the oxidant and dye concentrations was used ([H2O2]: [RB5] = 24.5 mg L-1: 25 mg L-1), leading to complete color removal within only 10 minutes of reaction. With the same initial condition, the Fenton and UV/H2O2 processes were also capable of removing the color entirely, even though they demanded more extended runs of 25 min. and 45 min., respectively. The effect of pH on the decolorization by the photo-Fenton process was also investigated, showing the same high performance at pHs 3 and 4. The degradation profile achieved by the photo-Fenton treatment was appropriately fitted by a pseudo-first-order kinetic. The non-expensive photoreactor proved to be quite useful for the degradation of the RB5, mainly when this azo dye underwent the photo-Fenton process.

Photodegradation of Reactive Black 5 and raw textile wastewater by heterogeneous photo-Fenton reaction using amino-Fe3O4-functionalized graphene oxide as nanocatalyst

Amino-Fe3O4-functionalized graphene oxide (AmGO) was synthesized and had its photocatalytic properties investigated in the degradation of Reactive Black 5 (RB5) dye and raw textile wastewater (RTW). Graphene oxide was synthesized via modified Hummers method and functionalized with diethylenetriamine and FeCl3 to obtain the AmGO. A 23 factorial design was carried out to optimize the best working conditions; the most statistically significant effect was the AmGO dosage, followed by the initial pH. Kinetics studies were performed and Chan & Chu model the most representative of the experimental data with R2 ≥ 0.95. Experiments of adsorption kinetics were carried out and evidenced that the adsorption of RB5 by AmGO was slower than photodegradation, in which the equilibrium state was reached after 300 min. Moreover, pseudo-second-order model showed the best fit with adsorptive capacity at equilibrium of 53.06 mg∙g−1. AmGO employment in the photodegradation of RB5 exhibited 75 % removal efficiency in less than 2h for the initial dye concentration of 100 mg∙L−1. AmGO also showed satisfactory recycling capacity, since it maintained RB5 removal up to 97 % after 6 cycles. RTW photodegradation experiments exhibited removal efficiencies of 53.25 % for apparent color, and 64.55 % for turbidity. Phytotoxicity assays using cucumber seeds showed low toxicity of the samples after photodegradation, which indicated that toxic compounds were fully mineralized.

Biotreatment of sulfonated dyestuffs with energy recovery in microbial fuel cell: Influencing parameters, kinetics, degradation pathways, mechanisms, and phytotoxicity assessment

Removal of recalcitrant sulfonated dyestuff intermediates from wastewater has been an urgent challenge for environmental technologies. In this regard, the biodegradations of monoazo Methyl Orange (MO) and diazo dyes Reactive Black 5 (RB5) towards wastewater treatment and bioelectricity generation in microbial fuel cell were investigated and compared through the studies on azo dye concentration, aeration, sampling points arrays, and electrode spacings. The degradation of diazo RB5 yielded higher chemical oxygen demand removal, decolourization efficiencies, and power generation over monoazo MO. The decolourization efficiency of RB5 (97.62%) increased with an increase of RB5 concentration (50 mg/L), suggesting that the system has the capability of removing higher RB5 concentration. However, contrary results were obtained with MO due to its toxicity. This study also demonstrated that the decolourization rate of diazo RB5 (0.1533 h−1) was ≈ 53% higher than monoazo MO (0.0727 h−1). The findings revealed that the degradation kinetic was remarkably influenced by the chemical structure of dye, where dye with more electron-withdrawing groups at para position are more susceptible to be reduced. Higher output voltage (568.59 mV) and power generation (108.87 mW/m2) were attained with RB5 due to electron donor availability and electron-shuttling characteristics of RB5 decolourized intermediates. Furthermore, detailed degradation pathways of MO and RB5 were presented based on the UV–vis and GC-MS results. The phytotoxicity assessment via Sorghum bicolor seeds had further verified the reduction in toxicity after the treatment of azo dyes.

Heterogeneous activation of peroxymonosulfate with Fe3O4 magnetic nanoparticles for degradation of Reactive Black 5: Batch and column study

In the present study, magnetite nanoparticles (Fe3O4) were used to activate peroxymonosulfate (PMS) in the degradation of Reactive Black 5 (RB5) from aqueous solutions. 94.86% of RB5 was degraded using Fe3O4 dosage of 250 mg L−1, PMS of 2 mM at pH of 7 after 60 min. The RB5 degradation rate was improved with temperature, and the activation energy was obtained to be 13.36 kJ mol−1. The presence of chloride, carbonate, nitrate, and bicarbonate in the solution reduced the rate of RB5 degradation due to the scavenging effect and the production of reactive species with low oxidation potential. Fe3O4 exhibited excellent stability for 240 min in a column reactor. The scavenging experiments emphasized that both SO4•- and •OH play an important role in the tests; however, SO4•- was the dominant species for RB5 degradation. The possible mechanism of PMS decomposition into reactive species by Fe3O4 was proposed. The column reactor showed a degradation efficiency of 95.65%, 80%, and 50% for RB5 in the synthetic sample, surface water, and textile wastewater, respectively. Toxicity was assessed by culturing Escherichia coli (E. coli) under the optimal condition. Five RB5 degradation products were identified by gas chromatography-mass spectrometry (GC-MS), and SO42-, NH4+, NO3-, CO2 and H2O were produced as the final mineralized products in the Fe3O4/PMS system. Comparative experiments have shown that the Fe3O4 catalyst has high efficiency in PMS activation and RB5 degradation; however, the presence of ultrasound, heat, and ultraviolet in the catalytic system can be beneficial to increase the degradation rate during fewer reaction times.

Photocatalytic degradation of RB5 textile dye using immobilized TiO2 in brass structured systems

In this paper, it was used a monolithic-type structured photoreactor with a high surface area calcined brass as a substrate for TiO2-P25. The TiO2 immobilization over the monoliths was carried out by the washcoating process. The films were characterized via XRD and diffuse reflectance. The monoliths were tested at a recirculation reactor using a solar simulator as an energy source and their efficiency was evaluated at Reactive Black 5 (RB5) textile dye photodegradation. It was investigated the effect of the impregnated catalyst mass, the monolith size, the initial dye concentration and the reaction medium pH. The preliminary tests of the brass calcination temperature (500, 600, and 700 °C) showed the formation of ZnO and CuO semiconductors at the brass surface, thus suggesting that the monoliths can act as photocatalysts. Furthermore, the brass calcined at 500 °C showed the greater formation of both oxides (ZnO and CuO) and greater photocatalytic efficiency. The TiO2/brass monolith presented more than 59 % of degradation for an initial dye concentration of 12.5 mg.L−1. In regarding to stability test, the system set forth a decrease at RB5 degradation efficiency of 62 % and presented an adherence of 77.5 % after 5 cycles of monoliths reuse. Therefore, the brass monolithic systems with immobilized TiO2 showed to be a feasible alternative for textile effluent treatment.

Dye degradation potential of Acinetobacter baumannii strain VITVB against commercial azo dyes

The textile industry is an age-old industry in human civilization and to date, it contributes to a major portion of the economy in several nations. However, the generation of a huge volume of toxic colored effluent is a major environmental concern. Azo dyes are extensively used for textile dyeing and are thus found in the wastewater. In this article, bacterial bioremediation of azo dyes was studied. Acinetobacter baumannii strain VITVB, a gram-negative bacterium aerobically decolorized 500 mg L−1 of two textile azo dyes Reactive Blue 221 (RB-221) and Reactive Black 5 (RB-5) with 90% and 87% efficiency after 48 h under static condition. Dye degradation was further maximized by optimization studies. A. baumanii VITVB exerted maximum dye degradation within 24 h under optimized conditions of pH 9, temperature at 45 °C, 5% NaCl concentration, and supplementation of 1% starch (Carbon source) and 1% peptone (Nitrogen source) in growth media. Dye Degradation was then analyzed. Fourier transform infrared spectra of pure and degraded dyes revealed that the potential bacterial strain targeted the characteristic chromophore group (N = N) during the break down of dyes. High-performance liquid chromatography of pure and degraded dyes presented the emergence of different peaks at altered retention times, which also indicates the degradation of dyes. Gas Chromatography–Mass Spectrometry chromatogram revealed probable end products as diphenylmethane from RB-221 degradation and benzene,1,1'-Pentylidenebis from RB-5 degradation. Finally, phytotoxicity and biotoxicity assays implied the nontoxicity of the degraded metabolites of RB-221 and RB-5. Pure dyes inhibited seed germination, showed marked phenotypic changes and cellular damages in plants (Cicer arietinum and Tagetes erecta) while the degraded metabolites promoted a healthy seed germination rate and no marked cellular damages or phenotypic changes in plants. Artemia salina cysts also showed a similar pattern as major hatchability inhibition occurred with pure dyes compared to degraded dye metabolites.

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl−, SO42−) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10−2 min−1) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including 1O2, SO4·−, HO., and ·O2−, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination.

Impact of the stacking fault and surface defects states of colloidal CdSe nanocrystals on the removal of reactive black 5

The photodegradation of the reactive black 5 (RB5) with CdSe-MSA nanocrystals (NCs) synthesized by using mercaptosuccinic acid (MSA) was studied. The quantum confinement effect was confirmed via the blue shift of absorbance band and higher energy band gap values. Photoluminescence (PL) emissions were riddled with low energy bands arising from the recombination of trapped charge carriers. The surface stress of the nanocrystals from the ligand capped surface and the atomic position relaxation at the stacking fault interface was linked to an observed hexagonal distortion. The comparison of SO and LO modes was used to analyze the quality of NCs, defect and disorder on the NCs surface. Contact time and RB5 degradation with NCs were investigated to understand the adsorption-photocatalysis synergy. Statistical physics parameters were calculated to explain the dye adsorption on tested nanocrystals. CdSe-MSA showed remarkable UV-light photocatalytic activity with a dye degradation of 89% in 120 min.

Highly efficient solar photocatalytic degradation of a textile dye by TiO2/graphene quantum dots nanocomposite.

Herein, two sunlight responsive photocatalysts including TiO2 nanoparticles (NPs) and TiO2/graphene quantum dots (GQDs) nanocomposite for degrading a textile dye, Reactive Black 5 (RB5), were prepared. The results showed that 100% of 50ppm RB5 could be degraded by TiO2 NPs and TiO2/GQDs within 60 and 30min sunlight irradiation, respectively. Hence, much better photocatalytic activity in degradation of RB5 was achieved by TiO2/GQDs under sunlight irradiation compared with pure TiO2 NPs due to its lower band gap (2.13eV) and electron/hole recombination rate. The photocatalytic degradation mechanism of RB5 by TiO2 NPs was elucidated by adding some scavengers to the solution. The main reactive species contributing to RB5 degradation were surface hydroxyl radicals. The first-order solar degradation rate constant of RB5 for TiO2/GQDs is greater than that of TiO2 NPs under sunlight illumination.

Heterogeneous activation of peroxymonosulfate by GO-CoFe2O4 for degradation of reactive black 5 from aqueous solutions: Optimization, mechanism, degradation intermediates and toxicity

The magnetic cobalt ferrite (CoFe2O4) loaded on graphene oxide (GO) was synthesized by the co-precipitation method and used to activate peroxymonosulfate (PMS) in the degradation of the reactive black 5 (RB5). The response surface methodology (RSM) was used to optimize the laboratory parameters and the interaction between them. The maximum degradation efficiency with R2 > 99% was obtained at pH of 7, the GO-CoFe2O4 dose of 125 mg/L, the RB5 concentration of 50 mg/L, the PMS dose of 2.49 mM, and the reaction time of 3.49 min. Under optimal conditions, the degradation efficiency of the PMS/GO-CoFe2O4 process (100%) was much higher than that of GO (33%), GO-CoFe2O4 (43.12%), and PMS (14.05%) at 30 min. The RB5 degradation rate was improved with temperature, and the activation energy was calculated to be 12.47 kJ/mol. Nitrate and carbonate reduced the degradation efficiency of RB5 by reacting with the main radicals. The PMS/GO-CoFe2O4 system showed good performance for the treatment of raw water. However, it does require a longer treatment time for real wastewater. GO-CoFe2O4 showed excellent stability and reusability in five consecutive reaction cycles to remove chemical oxygen demand (COD) and total organic carbon (TOC). The proposed PMS activation mechanism based on scavenging experiments showed that SO4•- plays a dominant role in the RB5 degradation. The gas chromatography–mass spectrometry (GC–MS) analysis showed that RB5 was degraded through the pathways, including desulfonation, dechlorination, deamination, hydroxylation, dehydrogenation, and chain/ring cleavage. Toxicity tests were performed with Daphnia pulex, and the results showed that the treated effluent required more catalytic treatment and better stabilization due to the presence of cobalt ions and intermediates.