Extent Of Decolorization Research Articles

By-product distribution and cytotoxicity assessment of ZnO-assisted photocatalytic degradation of reactive blue 250 dye

This research examined the effectiveness and feasibility of utilizing ultraviolet (UV) assisted photo-catalysis to treat wastewater effluents from textile production containing reactive blue 250 (RB 250) dye. Molecular oxygen and active species like O2•−, HO2•, H2O2 and •OH play crucial roles in the degradation process. Additionally, the degradation of dyes is influenced by several factors, including dye concentration, duration of UV irradiation, pH levels, concentration of H2O2, and the catalyst. The concentration of H2O2 and catalyst dose for the decolorization was studied at 0.6 mL and 0.5 g respectively. The discoloration was higher at low dye concentration, high H2O2 concentration, acidic conditions and high catalyst concentration. The maximum degradation (97 %) of RB 250 dye was obtained in the presence of zinc oxide nanoparticles within 90 min. The extent of decolorization of the dye was determined by UV–Vis spectroscopy. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the changes in functionalities after degradation. The disappearance of characteristic peaks associated with specific groups within the dye molecule confirmed the extensive degradation of RB 250 dye. LCMS analysis was conducted to examine the intermediates and a mechanistic degradation pathway was subsequently proposed. The cytotoxicity of the irradiated dye samples was evaluated through a hemolytic test both pre and post-treatment. The findings suggest that the UV/H2O2/ZnO treatment represents a promising approach for effectively degrading RB 250 dye.

The adsorption behaviour of biochar derived from Prosopis juliflora with surface modified by KOH against Allura red dye

This study examined the efficacy of ProsopisJuliflora with surface changes as a bioadsorbent for the removal of Allura Red dye. The effects of adsorptive dosage, pH, and contact period with starting dye attentiveness on adsorption were examined in the batch adsorption study. The study demonstrated that the Allura Red dye may be absorbed by surfaces that had been treated with KOH compound.The percentages of Allura Red dye eliminated were 67.18 %, 75.88 %, and 94.37 %, respectively. UV–visible adsorption spectroscopy is used to quantify the extent of dye decolorization. The modified surface characteristics of the adsorbent produced by ProsopisJuliflora were reported using XRD, FTIR, and SEM. The Adams-Bohart mathematical models are employed in the computation and assessment of adsorption efficiency. The adsorption-derived R2 values for the equilibrium isotherm data model were 94.63, 86.67, and 96.35. Diffusion and intraparticle regeneration were investigated to bolster the adsorption investigation.

Immobilization of fungal mycelial and laccase from Trametes hirsuta EDN082 in alginate-cellulose beads and its use in Remazol Brilliant Blue R dye decolorization

In this study, laccase from Trametes hirsuta EDN 082 was immobilized onto alginate-cellulose beads (CAC-L) and employed for the decolorization of Remazol Brilliant Blue R (RBBR) dye. The characterization and decolorization efficiency of the CAC-L beads were compared to immobilized laccase without cellulose (CA-L), immobilized fungal mycelia (CAC-FM), alginate-cellulose (CAC), and alginate beads (CA), and examined using light microscopy, FTIR, and SEM. The results showed that laccase was successfully immobilized onto alginate-cellulose beads with an enzyme loading of 1.9 U/mL and an immobilization efficiency of 97.7 %. The optimal decolorization (89.2 %) was achieved with 2 g CAC-L beads and 1.9 U/mL laccase activity at 40 °C and pH 5 for 6 h of incubation. Furthermore, the decolorization extent was >70–80 % after five cycles. The phytotoxicity test using Vigna radiata and Artemia salina revealed biodetoxification, indicating that CAC-L beads could be used as a biocatalyst for dye removal.

Degradation of Procion brilliant yellow H-E6G using ultrasonic and hydrodynamic cavitation combined with oxidants with demonstration at pilot scale.

The current study focuses on the degradation of Procion brilliant yellow H-E6G, an azo dye, using ultrasonic and hydrodynamic cavitation (HC), evaluating the impact of various parameters on the extent of degradation. The use of only ultrasound showed less oxidation capacity as indicated by only 19.1% degradation at an optimized power of 140 W, pH of 2.5, temperature of 40°C, and initial dye concentration of 15 ppm. The effectiveness of hybrid approaches involving US + H2 O2 , US + Fenton, and US + H2 O2 + potassium persulfate (KPS) was subsequently evaluated under optimized conditions. A notable enhancement in decolorization extent was observed for combined operations, including US + H2 O2 , US + Fenton, and US + H2 O2 + KPS (dual oxidant scheme) with the actual decolorization extents as 80.6%, 85%, and 92.2% respectively. An optimized scheme of US + H2 O2 + KPS was also utilized to decolorize the dye at a pilot scale using a US flow cell and also an HC reactor that yielded 91.8% and 88% reductions in initial concentration. The dye decolorization was elucidated to follow first-order kinetics for all the individual and combination approaches. The obtained values of the rate constants were also utilized for the evaluation of the synergistic index. A toxicity analysis was also performed on the dye, both before and following treatment, utilizing two bacterial strains. A comparative analysis of various treatment approaches has been presented focusing on factors such as cavitational yield, operational expenses, and energy requirements. The study elucidated that the combination of US + H2 O2 + KPS effectively removes Procion brilliant yellow H-E6G giving 92.2% as the maximum degradation at an operating cost of 0.1862 $/L. PRACTITIONER POINTS: First depiction of cavitative degradation of Procion brilliant yellow H-E6G Optimizing the equipment operating parameters and chemical oxidants Demonstration of optimized treatment scheme at pilot scale Evaluation of various approaches based on synergy and costs of treatment US + H2 O2 + KPS is the best approach for dye degradation.

A INFLUENCE OF OPERATING PARAMETERS ON DECOLORATION OF INDIGO CARMINE SOLUTIONS USING GAMMA RADIATIONS

Abstract: It has been observed that the process parameters influence the extent of decoloration of synthetic dyes during gamma radiolysis in aqueous solutions. The influence of some factors viz. concentration of dye, dye solution pH, addition of H2O2 on the colour bleaching of Indigo Carmine dye in aqueous medium was studied using 60Co gamma radiation source (dose rate was 0.386 kGy/hr). The dose required for the thorough decoloration was observed to be the direct function of the dye concentration in the solution. Further, when pH of solution was increased, the extent of decoloration reduced, for all the concentrations. H2O2 addition had the accelerating effect on the overall decoloration. The addition of H2O2 was governed by the critical value which corresponds to optimum dose of H2O2 that is required for maximum decoloration.

Bioremediation of Azo Dye Brown 703 by Pseudomonas aeruginosa: An Effective Treatment Technique for Dye-Polluted Wastewater

Dye-polluted wastewater poses a serious threat to humans’, animals’ and plants’ health, and to avoid these health risks in the future, the treatment of wastewater containing dyes is necessary before its release to environment. Herein, a biological approach is used; the textile azo dye brown 703 is degraded utilizing Pseudomonas aeruginosa. The bacterial strain was isolated from textile wastewater dumping sites in Mingora, Swat. The optimization for bacterial degradation was carried out on the nutrient broth medium, which was then subjected to a variety of environmental physicochemical conditions and nutritional source supplementation before being tested. Under micro-aerophilic circumstances, the maximum decolorization and degradation of dye occurred at a 20 ppm dye concentration within 3 days of incubation at a neutral pH and 38 °C. The decrease in the intensity of the absorbance peak in the UV–Vis spectrum was used to measure the extent of decolorization. Initially, 15 bacterial strains were isolated from the textile effluent. Out of these strains, Pseudomonas aeruginosa was found to be the most potent degrading bacteria, with a degradation extent of around 71.36% at optimum conditions. The appearance and disappearance of some new peaks in the FT-IR analysis after the degradation of brown 703 showed that the dye was degraded by Pseudomonas aeruginosa. The GC–MS analysis performed helped in identifying the degraded compounds of azo dye that were utilized in illustrating the under-study process of brown 703 degradation. The biodegradation brought about by Pseudomonas aeruginosa can be employed successfully in the future as an eco-friendly approach with far reaching results.

Sustainable coproduction of xylooligosaccharide, single-cell protein and lignin-adsorbent through whole components’ utilization of sugarcane bagasse with high solid loading

Free-waste biorefining of lignocellulosic biomass is environmentally friendly and accelerates the achievement of carbon neutrality. Here, we developed a sequential process of biorefining using a high solid loading of sugarcane bagasse (SB) as feedstock to coproduce xylooligosaccharide, glucose and xylose for the first time, including a three-step chemical pretreatment with a combination of diluted potassium hydroxide and phosphoric acid, followed by hydrolysis with recombinant endo-xylanase from Pichia pastoris and cellulase and xylanase from Penicillium oxalicum. The novel process achieved a maximum xylooligosaccharide yield of 5.59 g/100 g SB, comprising 77.1 % xylobiose, 18.5 % xylotriose and 4.4 % xylotetraose, a glucose yield of 32.96 g/100 g SB and a xylose yield of 7.68 g/100 g SB. The obtained glucose and xylose were used for the cultivation of Candida utilis, resulting in 13.20 g single-cell protein/100 g SB, 56.5 % of which was crude protein. Lignin residues were precipitated from the generated waste liquids by adjusting the pH, with a recovery extent of 94.15 %, used as lignin-adsorbent. The lignin-adsorbent could efficiently adsorb the dyes Acid Black 1, Direct Orange S and Procion Red MX-5B, with decolorization extents of 92.33 %, 93.00 % and 65.46 %, respectively. The final supernatant rich in phosphorus and potassium could be used as the feedstock of liquid fertilizer to nourish plants. This explored strategy provides an alternative option to utilize all components from SB that is eco-friendly.

Catalytic activation of peroxymonosulphate with manganese and cobalt coated micro sand particles for the treatment of Floor-wash containing Reactive Black 5 (RB5) dye

Reactive Black 5 (RB5) is an azo dye widely used in various industries. This work is focused on treating Floor wash wastewater, which is one of the most voluminous and coloured streams emerging from RB5 manufacturing units. It is possible to reuse this water if it is efficiently decolorized. Water containing RB5 dye is hard to treat using conventional treatments due to its high stability and solubility. In this work, decolorization of simulated Floor-wash was investigated using peroxymonosulphate (PMS) and heterogeneous catalyst. The simulated floor-wash containing 100 mg/L of RB5 was prepared using tap water. The synthesis of manganese and cobalt-coated micro sand (MnCoMS) particles was done to efficiently activate peroxymonosulphate (PMS). The operational parameters such as catalyst dosage, PMS concentration, initial pH, reaction time, and reusability of MnCoMS were investigated. Under optimum conditions: 200 mg/L PMS, 10 g/L MnCoMS, and initial pH 9.5, 97.8 % of initial 100 mg/L RB5 was decolorized at the end of 60 min reaction time. RB5 decolorization was slightly slower at initial pH near neutral (7–7.8) as compared to that at acidic (4.5) or alkaline (9.5) pH values. The rate and extent of RB5 decolorization increased with an increase in PMS concentration from 50 mg/L to 200 mg/L. Similarly, the increase in MnCoMS concentration from 5 to 25 g/L increased the rate of RB5 decolorization. However the %RB5 decolorization at the end of 60 min was almost constant for MnCoMS concentration of 10 g/L and above. Experiments conducted in the presence of scavengers revealed that sulphate and hydroxyl radicals played important role in RB5 decolorization. The MnCoMS catalyst demonstrated excellent reusability with > 80 % RB5 decolorization achieved till the sixth use. Overall, PMS activation by heterogeneous catalyst MnCoMS is an efficient method for rapid decolorization of floor-wash containing RB5 dye.

Ultrasonic-assisted ozone degradation of organic pollutants in industrial sulfuric acid

In this work, a combination of ozone (O3) and ultrasound (US) has been firstly used to decolorize black concentrated sulfuric acid with high organic content. The effect of different reaction factors on the transparency, extent of decolorization, H2SO4 mass fraction, and organic pollutants removal is studied. In addition, the systematic interaction between ultrasound and ozone on the decolorization process is reviewed through comparative experiments of O3, US and US/O3. A sulfuric acid product that meets the requirements for first-class products in national standards, with an extent of decolorization of 74.07%, transparency of 70 mm, and a mass fraction of 98.04%, is obtained under the optimized conditions. Under the same conditions, it has been established that the treatment time can be saved by 25% using the US/O3 process compared to using O3. Further, the production of oxidative free radicals (•OH) in a concentrated sulfuric acid system is enhanced using the US/O3 process compared with O3. In addition, the degree of effectiveness of different oxidizing components on the decolorization process is revealed by adding different free radical shielding agents when the US/O3 process is used.

Decolorization of an aqueous solution of methylene blue using a combination of ultrasound and peroxate process

For oxidative decolorization of an aqueous solution of methylene blue (MB), the “Sonoperoxate” process, a combination of ultrasonic (US) irradiation and “Peroxate” process, – US/H2O2/KIO4 was used in the current work. In order to minimize the costs of oxidants, energy consumption, and reduce the duration of decolorization, the studies were performed to understand the influence of the molar ratio MB:H2O2:KIO4, the MB initial concentration, the ultrasonic power, and the pH value of the initial solution on the decolorization of MB. The best conditions for decolorization of an MB aqueous solution using the “Sonoperoxate” process have been established as initial MB concentration of 62.6 μM, the molar ratio MB:H2O2:KIO4 of 1:100:25, pH of 4.00, US power of 60 W and the decolorization duration of 300 s. Under these conditions, the decolorization extent was quite high (95.6%). An increase in the processing duration to 3600 s led to a marginal increase in the decolorization extent of MB to 98.2%. The rate constants of the processes US/H2O2, US/KIO4, H2O2/KIO4, and US/H2O2/KIO4 were used to calculate the value of the synergetic coefficient for the hybrid process, US/H2O2/KIO4. The obtained synergetic coefficient was 3.25 at the molar ratio MB:H2O2:KIO4 as 1:100:25, and 1.62 at the molar ratio of 1:200:50 indicating the dominant contribution of KIO4. The effect of ultrasound as an activator of oxidants (periodate, hydrogen peroxide) has been conclusively established in the current work.

Intensified degradation of Acid Violet 7 dye using ultrasound combined with hydrogen peroxide, Fenton, and persulfate

• First detailed study into ultrasound induced decolorization of acid violet 7 containing effluent. • Establishing the optimum operating parameters for both individual and combined approaches. • Ultrasound + Fenton is the best treatment approach resulting in complete removal. • Hydroxyl radicals are more effective as compared to the sulphate radicals for acid violet 7 removal. • Kinetic analysis and quantifying the mineralization of the effluent. In the present work, the sonochemical degradation of an acid dye, acid Violet-7, has been investigated using an ultrasonic bath at an working volume as 1 L. Effect of ultrasonic power, treatment time, temperature, pH, ultrasonic frequency, initial concentration, and combination with oxidants such as H 2 O 2 , Fenton’s reagent and persulfate on the decolorization has been studied. The results showed that lower dye concentration, acidic conditions and lower temperature (20 ˚C) favored the decolorization for the only ultrasound approach. The maximum extent of decolorization for only ultrasound based process was 76.3% under conditions of 20 ppm dye concentration, 100 W power, pH 3 and 40 kHz frequency. For the combination approaches, maximum effect was seen for Fenton reagent where the combination of US + Fenton resulted in almost 100% decolorization and extent of COD reduction as 80.9%. Combinations of ultrasound and H 2 O 2 or ultrasound and KPS demonstrated comparatively lower efficacy compared to US + Fenton. Kinetic studies were also performed for various treatment approaches. It has been clearly elucidated that ultrasound in combination with optimized loading of Fenton reagent are effective in treating Acid Violet-7 dye containing effluents.

A new technique to estimate percentage decolorization of synthetic dyes on solid media by extracellular laccase from white-rot fungus

The enormous colored effluent discharges due to increased usage of synthetic dyes in textile and other chemical industries pollute both freshwater and marine reservoirs and cause ecotoxicity and serious health problems. This issue needs to be addressed skillfully and demands an ecofriendly and economically feasible technique. Pertaining to this, the current study was focused on the use of a white rot fungus, Resinicium bicolor to decolorize and degrade a recalcitrant dye, Congo red (CR) through its extracellular laccase enzyme secreted by mycelia. This work was also intended to develop a simple mathematical formula to calculate decolorization (%) of various dye categories usually tested on the solid medium plate involving different white rot fungi. The fungus was grown on malt extract agar (MEA) plate containing media supplemented with CR, 1% (g/l) to check the extent of decolorization and hence efficacy of Resinicium bicolor laccase at an interval of 24 hours (hrs). Decolorization (%) was determined by a formula derived from ‘Plate Volume Method’ (PVM). The maximum decolorization achieved on solid medium was 97.79% and 96.79% in liquid culture medium by the end of 96 hrs without the involvement of any chemical mediators which are generally toxic and expensive. Efficient decolorization achieved in the liquid medium validated the accuracy of ‘PVM’.

Treatment of acid violet 7 dye containing effluent using the hybrid approach based on hydrodynamic cavitation

The present work investigates the degradation of the azo dye, Acid violet-7 using hydrodynamic cavitation (HC) in combination with advanced oxidation processes (AOPs). The recalcitrant nature of the dye makes the conventional methods of degradation less effective and hence it is important to explore advanced methods. The development of treatment scheme for AV-7 using HC involved the optimization of initial dye concentration (10–200 ppm) and operating pH (3–10) to maximize decolorization using the approach of HC alone. At the optimum initial dye concentration of 20 ppm, operating pH of 3 and selected inlet pressure of 4 bar, the maximum decolorization was 39.1 % and mineralization was 25.2 % obtained using individual HC process without the addition of any chemical oxidants. The combined process of HC coupled with oxidants evaluated in the work were HC+H2O2, HC + KPS and HC + Fenton which resulted in the extent of decolorization as 70.49, 77.72 and 94.02 % respectively and the extent of mineralization as 38, 48.8 and 70.4 % respectively. The dye decolorization followed first order kinetics in all the approaches and obtained rate constants were used to evaluate the effectiveness of combinations in terms of the synergistic index. Additionally, comparison of efficacy of each treatment scheme was established with the aid of cavitational yield and the treatment costs. Overall, the combination of HC and Fenton oxidation was demonstrated to be the best approach for the degradation of AC-7 dye compared to the other combined oxidation processes.

Biodegradation of azo dyes and dyes present in textile wastewaters using Bacillus sp. az28, obtained from industrial effluents

The bacterial isolate Bacillus sp. AZ28, obtained from industrial effluent, demonstrates a great capacity to degrade various azo dyes (methyl orange (MO), magneson I (MI), novacron dark blue (NDB), and novacron red FN 3GF (NRF3)), and azo dye-containing textile effluent (TE). The degradation was evident by decolorization of dyes, and the decolorization efficiency of 84-95% was achieved within 14-72 h under optimum conditions, such as 37˚C, pH 7, inoculation size 8%, 1% glucose, and 1% beef extract. The extent of decolorization of individual dye was determined by UV–Vis spectroscopy, and products of biodegradation were analyzed by FTIR spectroscopy and TLC analyses. Chemical analysis showed that the COD and BOD values were significantly reduced after treatment. Thus, the biodegradation ability under mild conditions suggests that Bacillus sp. AZ28 has potential in textile effluent treatment.
 J. Bangladesh Acad. Sci. 45(1); 117-122: June 2021

Preparation of PANI Modified ZnO Composites via Different Methods: Structural, Morphological and Photocatalytic Properties

Polyaniline modified zinc oxide (PANI-ZnO) photocatalyst composites were synthesized by focusing on dissolution disadvantage of ZnO. In-Situ chemical oxidation polymerization method was performed under neutral conditions (PANI-ES) whereas in hybridization method physical blending was applied using emeraldine base of polyaniline (PANI-EB). PANI-ZnO composites were prepared in various ratios of aniline (ANI) to ZnO as 1%, 3%, 6% and 9%. The alterations on the structural and morphological properties of PANI-ZnO composites were compared by Fourier Transform Infrared (FT-IR), Raman Spectroscopy, X-ray Diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-ray Analysis Unit (SEM-EDAX) techniques. FT-IR and Raman spectroscopy confirmed the presence of PANI in all composites. SEM images revealed the morphological differences of PANI-ZnO composites based on PANI presence and preparation methods. Photocatalytic performances of PANI-ZnO specimens were investigated by following the degradation of methylene blue (MB) in aqueous medium under UVA irradiation. The effects of catalyst dose and initial dye concentration were also studied. MB degradation was followed by both decolorization extents and removal of aromatic fractions. PANI-ZnO composites expressed enhanced photocatalytic performance (~95% for both methods) as compared to sole ZnO (~87%). The hybridization method was found to be more efficient than the In-Situ chemical oxidation polymerization method emphasizing the significance of the neutral medium.

Synergistic Effect of H2O2 Addition on Gamma Radiolytic Decoloration of Some commercial Dye Solutions

Gamma radiations have emerged as a potential tool to degrade and decolorize the industrial effluents containing synthetic dyes in eco friendly and efficient manner. The dose and exposure time required to achieve the efficient decolration are quite high using gamma radiations alone during gamma radiolysis of synthetic dyes. Studies have revealed that, it can be brought down significantly on addition of H2O2 as it enhances the degree of decoloration. This happens due to the formation of highly oxidizing •OH radicals that are formed due to rapid reaction of H2O2with hydrated electrons formed during radiolysis of water. Further as the dose of H2O2 increases, extent and rate of decoloration also increases up to a certain value referred to as critical dose. But further increase in dose of H2O2 beyond this critical value affects the extent of decoloration adversely. In present communication, the gamma radiation induced decoloration of Methylene Blue, Malachite Green and Indigo Carmine dyes was achieved using various doses of H2O2. It was observed that, the value of H2O2 Critical dose required for efficient decoloration varies from dye to dye indicating its dependence on structure and concentration of dye solutions.

Degradation and biotoxicity of azo dyes using indigenous bacteria-acclimated microbial fuel cells (MFCs)

This study explored a bioenergy platform of biodegradability and toxicity evaluation through microbial fuel cells (MFCs) modules for simultaneous decolorization and bioelectricity generation. The most appropriate decolorizer consortia NIU pond exhibited the extent of decolorization: Sunset Yellow FCF (93 %), Allura Red (96.6 %), and Tartrazine (91.41 %) in 3, 8, 12 h respectively. The ranking for bioelectricity generation in MFCs (unit: mW m−2) (Sunset Yellow FCF Degradation) was hot spring water (46.42) > hot spring soil (22.17) > NIU pond (17.75) > NIU soil (7.89). In the presence of the dye, power density was increased by 88 %, 84 % and 27 % for NP, HS, and HW, respectively. Acclimation process was inspected in terms of bioenergy-extracting capability to evaluate toxicity potency of model dyes. According to metagenomics analysis upon microbial populations before and after acclimation, indigenous microbial community was only predominated by Pseudomonas monteilii and of Bacillus pumilus. Significant increased biodiversity was evolved under selection of dye stress. After acclimation, community ecology in the consortia contained Klebsiella, Citrobacter, Enterococcus faecalis, Lactobacillus lactis, and Escherichia shigella. Tandem mass spectrometric analysis pointed out sunset yellow ECF was gradually degraded and decolorized intermediates steadily accumulated. MFC modules were promising platforms to select candidate biodecolorizers from microbial populations.

Bacterial Degradation of Synthetic Dye by Pseudomonas sp. Obtained from Dyeing Mill Effluent

Environmental pollution is one of the major concerns of today’s world. Due to rapid industrialization and urbanization, a large number of wastes are generated and discharged into the environment and causing major pollution problems. For obtaining reactive dye decolorizing bacterial isolates, effluent samples were collected from a dyeing mill. From bacterial pure culture, 10 isolates were selected for screening. Screening of these isolates for the capability to decolorize and degrade reactive dye was performed in a nutrient broth medium containing reactive dye. 6 isolates among these bacterial isolates showed dye decolorizing ability within 120 hours of incubation. These isolates were further identified based on cultural, morphological, and biochemical characteristics. These characteristics indicated that these six bacterial isolates were distributed to the bacterial genus of Bacillus (2 isolates), Pseudomonas (2 isolates), Aeromonas (1 isolate), and Alcaligenes (1 isolate). For the study of dye decolorization and degradation, Reactive Dark Blue dye used in jute and textile industries was chosen. Pseudomonas, a prominent dye decolorizing isolate during screening, was taken for the optimization of different physicochemical parameters. This bacterium decolorized and grew well up to 500 mgL-1 of Reactive Blue dye. Pseudomonas sp. showed noteworthy decolorization of approximately 84% at 200 mgL-1 of dye concentration after 96 h of incubation. The optimum temperature for dye degradation was at 37 °C. The maximum level of decolorization for Pseudomonas sp. was observed at pH 8.0. This isolate showed better decolorization extent under static conditions rather than shaking conditions. This result indicated that the dye had been utilized by this bacterial isolate. It can be concluded that Pseudomonas is a prospective candidate in the biodegradation of Reactive Blue dye and might be useful in bioprocess technology used for the bioremediation of dyeing mill effluents.

Decolorization and Degradation of Reactive Blue Dye Used in Jute and Textile Industries by a Newly Isolated Bacillus sp.

For biodegradation of reactive dyes used in jute and textile industries, bacteria were isolated from a dyeing mill effluent. Bacteria having a remarkable ability to decolorize and degrade reactive dye were screened by using dye Reactive Dark Blue WR (RDB-WR). Cultural, morphological and biochemical characteristics were observed, and based on these seven isolates having higher decolorizing capability was identified. Among these isolates, one of the prominent dye decolorizing isolates Bacillus sp. was taken for decolorization study. Under different physicochemical conditions, decolorization and degradation capabilities of Bacillus sp. were optimized by using RDB-WR, a dye commonly used in the jute and textile industries. This bacterium decolorized and grew well up to 500 mg L-1 of RDB-WR. Bacillus sp. showed significant decolorization approximately 86% at 200 mg L-1 of RDB-WR after 96 h of incubation. Optimum degradation of dye was achieved at 37 °C. Maximum decolorization was observed at pH 7.0 under static conditions. The study confirmed the potential of Bacillus in the biodegradation of Reactive Dark Blue WR. This bacterial isolate might be prospective in the biological treatment of dyeing mill effluents due to the high extent of decolorization.

Sonocatalytic and photocatalytic efficiency of transition metal-doped ZnO nanoparticles in the removal of organic dyes from aquatic environments

The present study investigated the efficiency of transition metal-doped ZnO nanoparticles (NPs) in the removal of Direct Blue 71 from aqueous solutions through photocatalytic (UV and visible light) and sonocatalytic processes. The ZnO particles were synthesized and analyzed by the SEM, XRD, FTIR, AFM, DLS, and zeta potential. The reaction conditions were optimized by concerned catalyst (i.e., dopant percentage and catalyst amount), solution pH, catalyst dose and initial dye concentration. The results demonstrated that the Ag-doped ZnO NPs could provide the highest UV light-based photocatalytic efficiency, while the Cu-doped NPs present the greatest sonocatalytic and visible light-based photocatalytic efficiencies. In all processes, the dye removal efficiency was better in acidic pH. Based on the insignificant difference of efficiency over the acidic range of pH, the natural pH of the dye, i.e., 5.6, was considered as the optimal pH value. Also, the increase of dopant percentage enhanced the decolorization efficiency of the catalysts. However, 2.5% dopant amount was selected as the optimal dopant content due to the negligible difference in the decolorization percentages observed using the 2.5 and 5% dopant percentages. Furthermore, the increase of catalyst dose and contact time increased the removal efficiency, while the increase of initial dye concentration resulted in a lower extent of dye decolorization.