Decolorization Rate Research Articles

TiO2/Zn0.5Cd0.5S heterojunction for efficient photocatalytic degradation of methylene blue and its photocatalytic mechanism

TiO2/Zn0.5Cd0.5S composites were prepared by co-precipitation-hydrothermal method.The two substances come together to form a heterojunction structure. After recombination, the band gap decreases, the response range to visible light becomes larger, the recombination efficiency of electron-hole pair becomes lower, and the electron transfer rate becomes faster. In the photocatalytic process, 90%-TiO2/Zn0.5Cd0.5S photocatalyst has the best effect, the decolorization rate reaches 94.2% at 240 min, and the reaction rate constant is 0.0142 min−1, respectively 2.1 times for Zn0.5Cd0.5S and 5.2 times that of TiO2, and the active group is O2–· during the degradation process.

Mechanism and Adsorptive Performance of Ash Tree Seeds as a Novel Biosorbent for the Elimination of Methylene Blue Dye from Water Media

In this work, Ash samara seeds are used as a new biosorbent in raw form, without activation, to purify water containing cationic textile dyes. The study of this process is carried out in batch mode. The different physico-chemical parameters are studied such as the point of zero charge, the moisture content, the ash content, the volatile matter, the mass effect, and the pH of the solution. Fourier transform infrared spectroscopy characterization shows the existence of significant OH, C=O, C-O-C, and C=C functional groups. The performance is satisfactory: the decolorization rate is 95 ℅, under the experimental conditions: 2.4 g/L biomaterial, pH ∼ 7, and Ci = 25 mg/L. Several kinetic and isothermal models are applied: Avrami proved to be the best fit to the experimental data, the calculated amount is Qcal = 10.09 mg/g with R2=0.99 and χ2=0.018. The non-linear Liu modelling agrees with the experimental results Qmax = 100.48 mg/g with R2 = 0.987, χ2=11.67, and RMSE= 2.91. The thermodynamic study suggests that the methylene blue biosorption process is favorable, spontaneous, and exothermic. The mechanisms involved are non-covalent bonds (π-π interactions, hydrogen bonds, n-π interactions, Van der Waals forces), and that the process is multi-docking (n<1) reflecting the biosorption of methylene blue in a parallel site on the adsorbent surface.

Ultrasonic-Assisted Synthesis of CdS/Microcrystalline Cellulose Nanocomposites With Enhanced Visible-Light-Driven Photocatalytic Degradation of MB and the Corresponding Mechanism Study.

A simple and efficient ultrasonic-assisted approach was designed to synthesize CdS/microcrystalline cellulose (MCC) nanocomposite photocatalyst. The obtained products have been characterized by XRD, FE-SEM, TEM, UV-Vis DRS, and nitrogen adsorption isotherms. The results showed that the intimate contact of MCC and CdS is beneficial for enhancing the photocatalytic performance because heterojunction formation can efficiently promote the separation of photogenerated electrons and holes of the nanocomposite photocatalyst. By using 10% MCC coupled CdS, the decoloration rate of methylene blue (MB) in the solution under visible-light was increased nearly 50%. In addition, the reuse experiments confirmed that the CdS/MCC nanocomposite photocatalyst had outstanding cycle performance and durability. Mechanism study demonstrated that hydroxyl radicals, photogenerated holes and superoxide radicals were the active species in the photocatalytic oxidization degradation of MB.

Enhanced photocatalytic degradation of Acid Blue dye using CdS/TiO2 nanocomposite

Photocatalytic degradation is essential for the successful removal of organic contaminants from wastewater, which is important for ecological and environmental safety. The advanced oxidation process of photocatalysis has become a hot topic in recent years for the remediation of water. Cadmium sulphide (CdS) nanostructures doped with Titanium oxide (CdS/TiO2) nanocomposites has manufactured under ambient conditions using a simple and modified Chemical Precipitation technique. The nanocomposites crystal structure, thermal stability, recombination of photo-generated charge carriers, bandgap, surface morphology, particle size, molar ratio, and charge transfer properties are determined. The production of nanocomposites (CdS-TiO2) and their efficient photocatalytic capabilities are observed. The goal of the experiment is to improve the photocatalytic efficiency of TiO2 in the visible region by doping CdS nanocomposites. The results showed that as-prepared CdS-TiO2 nanocomposites has exhibited the highest photocatalytic activity in the process of photocatalytic degradation of AB-29 dye, and its degradation efficiency is 84%. After 1 h 30 min of visible light irradiation, while CdS and TiO2 showed only 68% and 09%, respectively. The observed decolorization rate of AB-29 is also higher in the case of CdS-TiO2 photocatalyst ~ 5.8 × 10−4mol L−1 min−1) as compared to the reported decolorization rate of CdS ~ 4.5 × 10−4mol L−1 min−1 and TiO2 ~ 0.67 × 10−4mol L−1 min−1. This increased photocatalytic effectiveness of CdS-TiO2 has been accomplished by reduced charge carrier recombination as a result of improved charge separation and extension of TiO2 in response to visible light.

Non-traditional power supply mode: Investigation of electrodeposition towards a better understanding of PbO2 electrode for electrochemical wastewater treatment

The power supply mode is a non-negligible character in electrochemical process. Constant current mode is used in the traditional electrodeposition preparation process of PbO2 electrode, and there are very few studies on its electrodeposition power supply mode. In this paper, two non-traditional power supply modes (linear increase power supply mode and linear decrease power supply mode) were used to fabricate PbO2 electrodes, and the properties of prepared electrodes were compared with those of the traditional constant current power supply mode. On the premise of improving the electrode properties, the non-traditional power supply mode also significantly reduced the energy consumption of the electrodeposition process of PbO2. After material characterization (Scanning electron microscope, X-ray diffraction), electrochemical characterization (Electrochemical impedance spectroscopy, linear sweep voltammetry etc.) and stability test, it can be seen that the electrode surface prepared by the non-traditional power supply mode was spherical particles and its average grain size was smaller than that of the traditional one. The PbO2 electrode prepared by linear increase power supply mode had higher oxygen evolution overpotential (1.962 V), more active sites, smaller membrane impedance (33.15 Ω) and better stability (accelerated life up to 125.1 h). In the electrocatalytic oxidation tests of the three electrodes, the PbO2 electrode prepared by linear increase mode had the best performance in decolorization rate, Chemical oxygen demand removal rate, average current efficiency and energy consumption. Owing to favorable effects obtained, non-traditional power supply mode could be considered a promising alternative for PbO2 electrode preparation and applied electrochemical process for wastewater treatment.

Coordination and hydrogen bond-coadjusted highly stretchable wet-spun poly(acrylic acid) fiber and its stable activity as Fenton catalyst

High stretching is an effective route to attain high performance fiber. Therefore, the stretchability of wet-spun poly(acrylic acid) (PAA) fiber is important for the preparation of high performance PAA fiber by stretching. A combination of coordination and hydrogen bonding was synergistically used to prepare highly stretchable wet-spun PAA fibers, and high stretching was subsequently carried out to induce the production of molecular orientation and fibrillar crystals, which can remarkably enhance the strength of resulting fiber. The breaking strength of stretched fiber reached up to 1.631cN/dtex, increasing by 2813% compared to that of unstretched fiber. Moreover, high stretching was used to thin the resulting fiber and promote the transformation of PAA chains from coiled to extensional conformation, so that the carboxyl groups wrapped by coiled PAA chains were exposed to the environment. When the highly stretched fiber was used to decolorize methylene blue (MB) aqueous solution, the exposed carboxyl groups can quickly re-coordinate with the iron ions eluted by MB aqueous solution to minimize the loss of iron ions. The measurement results showed that the average concentration of eluted iron ions was only 3.20 mg/L during 40 operation cycles for the highly stretched fiber, decreasing by 64.0% compared to that of unstretched fiber. Due to low iron ion leaching-out, the highly stretched fiber showed superstable activity in catalyzing H2O2 to oxidatively decolorize MB. The research results revealed that the obtained fiber can decolorize more than 90% MB within 3 min during 40 cycles without showing any obvious attenuation in decolorization efficiency and decolorization rate. In this case, the Fenton catalysts reported by literature are scarcely comparable to the prepared fiber in many aspects. Therefore, the fiber prepared in this work can be expected to show great potential for application in the field of dye wastewater treatment.

Preparation of spunlaced viscose/PANI-ZnO/GO fiber membrane and its performance of photocatalytic decolorization

In order to solve the increasingly serious problem of printing and dyeing wastewater pollution, a kind of novel, efficient, and reusable spunlaced viscose/polyaniline-ZnO/GO fibrous membrane was fabricated in this work. Specifically, spunlaced viscose/polyaniline conductive fibrous membrane was firstly prepared by in-situ growth method, followed with the growth of zinc oxide (ZnO) and graphene oxide (GO) via the hydrothermal route to obtain spunlaced viscose/PANI-ZnO/GO fibrous membrane (SV@PANI-ZnO/GO membrane). The results show that the decolorization rate of SV@PANI-ZnO/GO membrane for methylene blue (5.0 mg/L) was 97.4% within 120 min, and the decolorization rate remained above 76.7% after five cycles. Moreover, the reaction process conformed to a quasi-first order kinetic model with the apparent rate constant of 0.0209 min–1. Meanwhile, the free radical capture experiment revealed that the main reactive species in the decolorization process was .OH. This work may provide a new method for designing photocatalytic materials for environmental applications.

Study on power generation and Congo red decolorization of 3D conductive PPy-CNT hydrogel in bioelectrochemical system

In this paper, a polypyrrole-carbon nanotube hydrogel (PPy-CNT) with 3D macroporous structure was prepared by secondary growth method. This self-supporting material with good conductivity and biocompatibility can be directly used as anode in a microbial fuel cell (MFC). The prepared material had a uniform structure with rich 3D porosity and showed good water retention performance. The effect of the mass ratio of PPy and CNT in the hydrogel were also investigated to evaluate the electrical performance of MFC. The MFC with 10:1 PPy-CNT hydrogel anode could reached the maximum power density of 3660.25 mW/m3 and the minimal electrochemical reaction impedance of anode was 5.06 Ω. The effects of Congo red concentration, external resistance and suspended activated sludge on decolorazation and electricity generation were also investigated in the MFC with the best performance hydrogel. When the Congo red concentration was 50 mg/L and the external resistance was 200 Ω, the dye decolorization rate and chemical oxygen demand (COD) removal rate could reach 94.35% and 42.31% at 48h while the output voltage of MFC was 480 mV. When activated sludge was present, the decolorization rate and COD removal rate could be increased to 99.55% and 48.08% at 48 h. The above results showed that the porous hydrogel anode had broad application prospects in synchronous wastewater treatment and electricity production of MFC.

One-step dye wastewater treatment by combined adsorption, extraction, and photocatalysis using g-C3N4 pickering emulsion

A stable liquid paraffin/water Pickering emulsion with amphiphilic graphitic carbon nitride (g-C3N4) to provide photocatalytic activity is prepared for the rapid treatment of rhodamine B (RhB) dye wastewater. The results show that the decolorization rate of RhB by liquid paraffin extraction alone is 50.9%; that by g-C3N4 adsorption alone is 51.4%. When liquid paraffin and g-C3N4 are combined to form a Pickering emulsion for treating RhB solutions, the decolorization rate increases to 78.8% in the dark. Under visible light irradiation, the decolorization rate reaches almost 100% in 25 min because of the addition of in situ photodegradation. The used Pickering emulsion can be easily recycled without performance degradation. The combination of adsorption, extraction, and photodegradation in the process intensifies the dye treatment, which does not require the separation and recovery of nano-photocatalysts or the secondary treatment of the eluent in adsorption and extraction. This work provides a convenient and promising method to form a functional and reusable Pickering emulsion for highly efficient wastewater treatment.

Decolorization of Synthetic Dyes by Tropical Fungi Isolated from Taman Eden 100, Toba Samosir, North Sumatra, Indonesia

Taman Eden 100 is one of the tourist parks located in Toba Samosir, North Sumatra, Indonesia that provides a wide range of biodiversity. The objective of this research was to obtain the potential fungal isolate with high laccase activity to decolorize synthetic dyes. The results show that six isolates of Perenniporia subtephropora EDN 050, Trametes hirsuta EDN 082, T. hirsuta EDN 084, T. hirsuta EDN 085, Deconica coprophila EDN 114, and T. pavonia EDN 134, which were confirmed by molecular identification using 5.8 rDNA/ITS analysis, exhibited decolorization activity. Six potential isolates showed the ability to decolorize textile dyes of Acid Blue 129, RBBR,Orange II, and Reactive Black 5. The highest decolorization rate of 100 ppm Acid Blue 129, RBBR, Orange II, and Reactive Black 5 dyes by using T. pavonia EDN 134 were 98.87%, 98.26%, 100%, and 98.11%, respectively after 96 h incubation. Almost all positive isolates also decolorized dyes at higher concentrations (1,000 ppm). This study offers the potential of Indonesian tropical fungal isolates for synthetic dyes waste treatment.

Extraction and Purification of Inulin from Jerusalem Artichoke with Response Surface Method and Ion Exchange Resins.

Inulin is used as an important food ingredient, widely used for its fiber content. In this study the operational extraction variables to obtain higher yields of inulin from Jerusalem artichoke tubers, as well as the optimal conditions, were studied. Response surface methodology and Box–Behnken design were used for optimization of extraction steps. The optimal extraction conditions were as follows: extraction temperature 74 °C, extraction time 65 min, and ratio of liquid to solid 4 mL/g. Furthermore, series connection of ion-exchange resins were used to purify the extraction solution where the optimal resin combinations were D202 strongly alkaline anion resin, HD-8 strongly acidic cation resin, and D315 weakly alkaline resin while the decolorization rate and decreased salinity reached 99.76 and 93.68, respectively. Under these conditions, the yield of inulin was 85.4 ± 0.5%.

Light-driven bio-decolorization of triphenylmethane dyes by a Clostridium thermocellum-CdS biohybrid

Widespread application of synthetic dyes could generate colored wastewaters causing a range of serious environmental problems. Due to the complex nature of effluents from textile industries, it is difficult to obtain satisfactory treatment of dyes-contaminated wastewater using one single method. Biohybrids coupling of photocatalysts and biocatalysts have great potential in environmental purification. However, how to select suitable organisms and enhance the hybrid’s catalytic activities remain challenging. Here, a novel biohybrid system (Clostridium thermocellum-CdS), created for light-driven biodecolorization under thermophilic treatment by using non-photosynthetic microorganism C. thermocellum self-photosensitized with CdS nanoparticles was established. The biohybrids exhibited remarkable decolorization effects on triphenylmethane dyes. The highest decolorization rate was 0.206 min−1. More importantly, enhanced catalytic activities of cadmium sulfide (CdS)-based biohybrids by controlling the particle sizes of semiconductors were demonstrated. Biohybrids systems (Clostridium thermocellum-CdS) through the self-precipitation of CdS with different particle sizes not only showed dramatic changes in the optical properties but also exhibited a very different decolorization rate. This work can not only further broaden targeted applications of CdS-based biohybrids but also demonstrate a promising route for improving biohybrids corresponding photocatalytic capabilities through in situ precipitation CdS with different particle sizes.

Degradation of acid red 73 wastewater by hydrodynamic cavitation combined with ozone and its mechanism

Many azo dyes are consumed in the textile and dyeing industry, which makes the wastewater recalcitrant and toxic to the aquatic environment. Dye degradation by the combination of hydrodynamic cavitation and ozone (HC + O3) has caused extensive interest. The degradation mechanism of the hybrid system needs further investigation. This study investigated the degradation of acid red 73 (AR73) by HC + O3. Meanwhile, the degradation pathways and mechanisms were present. The optimal operation parameters were: inlet pressure of 0.15 MPa, O3 dosage of 45 mg/min, initial dye concentration of 10 mg/L, and initial pH at 7.5. As a result, the decolorization rate, removal of UV254 and NH3–N were 100%, 71.28%, and 87.36% in 30 min, respectively. Humic acid and most of the co-existing anions (HCO3−, SO42−, Cl−, PO43−, NO3−) played a positive role in the degradation of AR73, while NO2− restrained. The reactive species of singlet oxygen (1O2), hydroxyl radicals (·OH) and super oxygen radicals (·O2−) showed synergism in the hybrid system, and the decolorization was attributed to the fracture of azo bonds by 1O2. Meanwhile, aromatic amines were generated and further degraded into small molecule compounds. The research certificated that the HC + O3 can be an effective technology for azo dye degradation.

Modification and characterization of hydrogel beads and its used as environmentally friendly adsorbent for the removal of reactive dyes

An environmentally friendly hydrogel (R-L-Gel) beads adsorbent was prepared and modified from rabbit skin gelatin by sol-gel methods. It was characterized and applied for the adsorption of reactive brilliant orange X-GN (RO X-GN) and reactive brilliant blue KN-R (RB KN-R) dyes. The mean diameter of R-L-Gel beads synthesized by L-Arginine (L-Arg) were 4.78 mm, it has smaller surface pores (12.47 μm), larger surface area (2.681 m2/g), closer three-dimensional network structure, stronger intramolecular connection, improved thermal stability, strong structural stability, and higher isoelectric point (6.75). Batch adsorption experiments were performed to analyzed the effect of pH, adsorption kinetics and isotherm model. The maximum adsorption capacity of both dyes reached about 340.55 mg/g at pH 3, and adsorption behavior was more consistent with pseudo-second-order kinetics and Freundlich isotherm equation. R-L-Gel beads had high adsorption capacity, low swelling rate (SR = 872%) in the pH = 3, and moderate reusability. In addition, the beads loaded with reactive dyes (R-L-Gel-O/B) could adsorb again methylene blue (MB) and basic fuchsin (BF) dyes, and the adsorption capacity reached 185.55 mg/g and 271.01 mg/g, respectively. R-L-Gel beads had good application effect on mixed dyes wastewater, the decolorization rate (DR) reached 70%, After adsorption, the swelling rate of R-L-Gel and R-Gel beads were 2003%, 6060% and compressive strength was 0.395 and 0.058 MPa respectively. which was expected to become an excellent adsorbent in the water treatment industry.

Degradation of Methyl Orange by ozone microbubble process with packing in the bubble column reactor

ABSTRACT The performance of the ozone microbubble(MB) process for the degradation of Methyl Orange (MO) in a bubble column reactor with added packing was investigated. The highest decolorization efficiency of 96.04% was achieved by the ozone MB process with packing, which was 10.17% and 62.02% higher than that of the ozone MB process without packing and the ozone millimeter bubble(MLB) process, respectively while keeping other operating parameters the same. In addition, the saturation gas holdup, ozone mass transfer coefficient, and decolorization rate constant of the ozone MB process with packing were 15.32%, 0.260 min−1, and 0.027 min−1, respectively, which were much better than those of the ozone MB process without packing and the ozone MLB process. The study also suggested that within a certain porosity range, the types of packings did not affect the performance of the ozone MB process in the degradation of MO. Moreover, the optimum operating conditions were initial concentration of MO of 30 mg/L, initial pH of 3, circulating liquid flow of 75 L/h, and ozone dosage of 0.56 mg/L. The decolorization efficiency was 99.28% within 120 min.

Carbon nanotubes mediated chemical and biological decolorization of azo dye: Understanding the structure-activity relationship

Chemical structure of azo dyes molecules showed significant influence on their decolorization rate, while the structure-activity relationship between chemical structure and their reduction decolorization rate is not fully understand. In this study, we found that azo dye molecule with closer position for electron-withdrawing substituent to azo bond resulted in faster chemical and biotic reduction rate with or without presence of carbon nanotubes (CNTs), while electron-repulsive substituent closer to azo bond leading to slower azo dye chemical and biotic reduction rate no matter with or without presence of CNTs. Additionally, galvanic cell experiments implied that electron transfer process may play important roles for both chemical and biological reduction decolorization of azo dyes, and CV results indicated that the higher (azo bond breakage) reduction wave potential corresponding to a faster azo dye chemical decolorization reaction. Finally, the results of Lowest Unoccupied Molecular Orbital (LUMO) energy established that lower LUMO energy for azo dye corresponding to a faster chemical decolorization reaction. This study not only offer systematized relationships between structure property of azo dye and their decolorization rate, but also provide a universal and propagable reduction rules.

Decolourization and biodegradation of methylene blue dye by a ligninolytic enzyme-producing Bacillus thuringiensis: Degradation products and pathway

In this study, a ligninolytic enzyme-producing strain F5 was isolated and identified as Bacillus thuringiensis, which can efficiently degrade methylene blue (MB) dye. The optimal pH, temperature, rotation speed, NaCl concentration, and inoculum of strain F5 for MB degradation were pH 6.0, 30 °C, 140 rpm, 10 g/L NaCl, 4% inoculum (v/v), and the strain F5 had salt tolerance, the MB decolorization rate reached 95% after 12 h. The degraded products were characterized by UV–vis, FT-IR, and GC-MS. Based on products analysis, four different intermediates were identified, and a new pathway for the degradation of MB was proposed. The degradation of MB by strain F5 was due to the synergistic effects of laccase (Lac), manganese peroxidase (MnP), lignin peroxidase (LiP), and NADH-DCIP reductase; among them, Lac and MnP were the key enzymes. The phytotoxicity results showed that MB degraded metabolites' toxicity was lower than that of the parent compound, indicating that the strain F5 had a detoxification effect on MB dyes.

Complete genome sequence of Shewanella algae strain 2NE11, a decolorizing bacterium isolated from industrial effluent in Peru

Shewanella is a microbial group with high potential to be applied in textile effluents bioremediation due to its ability to use a wide variety of substrates as a final electron acceptor in respiration. The present research aimed to describe a new strain, Shewanella algae 2NE11, a decolorizing bacterium isolated from industrial effluent in Peru.S. algae 2NE11 showed an optimal growth under pH 6-9, temperature between 30-40 °C, and 0-4 % NaCl. It can tolerate high concentrations of NaCl until 10% and low temperatures as 4 °C. It decolorizes azo and anthraquinone dyes with a decolorization rate of 89-97%. We performed next-generation sequencing (Pacific Bioscience®) and achieved its complete genome sequence with a length of 5,030,813bp and a GC content of 52.98%. Genomic characterization revealed the presence of protein-coding genes related to decolorization like azoreductase, dyp-peroxidase, oxidoreductases, and the complete Mtr respiratory pathway. Likewise, we identified other properties such as the presence of metal resistant genes, and genes related to lactate and N-acetylglucosamine metabolism. These results highlight its potential to be applied in the bioremediation of textile effluents and guide future research on decolorization metabolic pathways.

Novel electrospun ZIF/PcH nanofibrous membranes for enhanced performance of membrane distillation for salty and dyeing wastewater treatment

Membrane distillation (MD) has many attractive advantages such as high rejection, low operating temperature, and has shown great potential for salty and dyeing wastewater treatment. However, the existing MD membranes often suffers from low permeability and membrane pore wetting issue, which significantly limit its practical applications. Herein, Zeolitic imidazolate framework 71 (ZIF-71) was doped in poly (vinylidene fluoride-co-hexafluoropropylene) (PcH) to prepare a hydrophobic electrospun nanofibrous membrane for MD process. The incorporation of ZIF-71 nanoparticles not only improve the surface roughness and hydrophobicity of the original PcH nanofiber membrane, but also increase the permeation flux (19.2 L m−2 h−1) and desalination performance (>99.99%) of the MD membrane. What's more, ZIF/PcH membrane was used to treat salty and dyeing wastewater, still showing high permeation flux, excellent pollutant retention rate and high stability. The desalination and decolorization rate of the treated wastewater can reach more than 99.5%, and the COD removal rate can reach 99.12%. The present study suggested that ZIF-doped electrospun nanofiber membrane provide high potential applications for direct contact membrane distillation (DCMD) desalination.

Preparation and photocatalytic properties of Zn0.5Cd0.5S/BiOBr heterojunction

In this study, a Zn0.5Cd0.5S/BiOBr composite photocatalyst was constructed using an in situ growth technique. SEM and TEM revealed that the ZCS/BiOBr photocatalyst has an irregular sheet structure, and Zn0.5Cd0.5S particles form a heterojunction structure with BiOBr. The 70-Zn0.5Cd0.5S/BiOBr heterojunction exhibited the highest photocatalytic degradation efficiency for methylene blue, and the decolorization rate of MB was 99.52% in 240 min. The degradation rates were 1.83 and 4.76 times those of Zn0.5Cd0.5S and BiOBr, respectively. After four cycles, there was no significant decrease in photocatalytic activity; the main active substances involved in the degradation process were h+ and ·OH.