Nano-Catalytic Ozonation of 4-Nitrochlorobenzene in Aqueous Solutions

In this paper, efficiency of nano-ZnO particles on catalytic ozonation of 4-nitrochlorobenzene (4NCB) using semi-batch reactor has been studied at various pHs. During the catalytic ozonation, TOC and concentration of nitrate ions was monitored. Results indicate that degradation of 4NCB was improved by combination of nano-ZnO with ozone. The effect of ZnO particle size and pH are also examined. According to the results, concentration of 4NCB decreased with increasing of particle size from nanosized to microsized and pH from 3.0 to 9.0. Based on the results, it suggests radical hydroxyl does not affect on the degradation of 4NCB in catalytic ozonation, but the surface of catalyst plays main role. Kinetic studies showed degradation of 4NCB followed pseudo-first-order kinetic and maximum degradation rate was observed at pH=3

Synergistic degradation of diazo dye Direct Red 5B by Portulaca grandiflora and Pseudomonas putida

Plants and bacterial consortium of Portulaca grandiflora and Pseudomonas putida showed complete decolorization of a sulfonated diazo dye Direct Red 5B within 72 h, while in vitro cultures of P. grandiflora and P. putida independently showed 92 and 81 % decolorization within 96 h, respectively. A significant induction in the activities of lignin peroxidase, tyrosinase, 2,6-dichlorophenol indophenol reductase and riboflavin reductase was observed in the roots of P. grandiflora during dye decolorization; whereas, the activities of laccase, veratryl alcohol oxidase and 2,6-dichlorophenol indophenol reductase were induced in the cells of P. putida. Plant and bacterial enzymes in the consortium gave an enhanced decolorization of Direct Red 5B synergistically. The metabolites formed after dye degradation analyzed by UV-Vis spectroscopy, Fourier transformed infrared spectroscopy and high performance liquid chromatography confirmed the biotransformation of Direct Red 5B. Differential fate of metabolism of Direct Red 5B by P. grandiflora, P. putida and their consortium were proposed with the help of gas chromatography-mass spectroscopy analysis. P. grandiflora metabolized the dye to give 1-(4-diazenylphenyl)-2-phenyldiazene, 7-(benzylamino) naphthalene-2-sulfonic acid, 7-aminonaphthalene-2-sulfonic acid and methylbenzene. P. putida gave 4-hydroxybenzenesulfonic acid and 4-hydroxynaphthalene-2-sulfonic acid and benzamide. Consortium showed the formation of benzenesulfonic acid, 4-diazenylphenol, 6-aminonaphthalen-1-ol, methylbenzene and naphthalen-1-ol. Consortium achieved an enhanced and efficient degradation of Direct Red 5B. Phytotoxicity study revealed the nontoxic nature of metabolites formed after parent dye degradation. Use of such combinatorial systems of plant and bacteria could prove to be an effective and efficient strategy for the removal of textile dyes from soil and waterways

Efficiency of response surface methodology for optimizing Reactive Blue 21 dye removal with modified bentonite

Bentonite was modified with cetyltrimethylammonium bromide by a simple method and was used as an adsorbent for the removal of Reactive Blue 21 dye. Reactive Blue 21 is an important dye used in the textile industry, which is very harmful for living creatures, especially humans. The response surface methodology (RSM) was used to study the effect of independent variables such as dye concentration (20, 40, 60, 80 and 100 mg/dm3), time (10, 20, 30, 40 and 50 min), initial pH (2, 4, 6, 8, 10) and modified bentonite dosage (1, 2, 3, 4 and 5 g/dm3) on Reactive Blue 21 dye removal efficiency from aqueous solutions. At the optimum conditions (modified bentonite dosage 5 g/dm3, dye concentration 61.3 mg/dm3, pH 4.78; time14.31 min), the predicted removal of Reactive Blue 21 on modified bentonite was 93.22%. In a confirmatory experiment, 92.01% dye removal has been obtained. Thus, the experimental investigation and statistical approach enabled us to model adsorption of Reactive Blue 21 on modified bentonite

Adsorption of penicillin by decaffeinated tea waste

Removal of penicillin has been investigated using decaffeinated tea waste (DCTW). Decaffeination of tea waste was investigated using different methods. Results indicate that ozonation was the most effective process for removal of penicillin. Batch adsorption experiments were completed at various temperatures (20, 30, and 40°C), DCTW dosages (2, 4, 6, 8, and 10 g per 250 mL), penicillin concentrations (4, 10, and 14 mg/L), and pH (3, 7, and 10) conditions. Studies showed that adsorption reaches equilibrium within 40 min. The main factor affecting adsorption of penicillin was the solution pH, with maximum adsorption occurring at pH 3. Higher adsorbent dosages and lower penicillin concentrations also resulted in higher percentages of penicillin removal. Results show that data obeyed the pseudo-first-order kinetic and Freundlich isotherm models. This process proves that low-cost DCTW could be used as a high performance adsorbent for removing penicillin from aqueous solutions

Removal of Congo red from textile wastewater by ozonation

Congo red, which has a complex molecular structure with various diazo aromatic groups, is widely used in textile industry as an anionic dye. The purpose of this study was to investigate the degradation of Congo red in laboratory solution which had the chemical properties of the rinse waters of textile manufacturing dye-houses and the samples with Congo red alone wastewater by ozonation and to optimize the reaction parameters such as pH and time which influence the efficiencies of total organic carbon, total kjeldahl nitrogen and chemical oxygen demand removal. Ozonation of Congo red dye were carried out in a semi-batch reactor with constant ozone flow rate and concentration of 23 mL/sec and 13.6 mg/L, respectively. Decolorization was complete within a few minutes of ozonation possibly due to the cleavage of chromophore groups. It was observed that its structural destruction occurs predominantly at higher pHs. The reduction of chemical oxygen demand and destruction of the dye was more than 60 % and 42 %, respectively. Total kjeldahl nitrogen removal was accompanied by slight changes in nitrogen oxides. It can be deduced from the experimental results that: (a) the mineralization is very weak; (b) the reaction follows the indirect mechanism; i.e., the interaction of hydroxyl radicals with the dye and (c) the nitrification is rather predominant. Biological oxygen demand is declined in simulated alkalic and neutral samples respectively. At 13.6 mg O3/L, the biological oxygen demand levels were significantly enhanced. This might be attributable to the enhancement of its biodegradation at alkaline pHs

Nano-Catalytic Ozonation of 4-Nitrochlorobenzene in Aqueous Solutions

In this paper, efficiency of nano-ZnO particles on catalytic ozonation of 4-nitrochlorobenzene (4NCB) using semi-batch reactor has been studied at various pHs. During the catalytic ozonation, TOC and concentration of nitrate ions was monitored. Results indicate that degradation of 4NCB was improved by combination of nano-ZnO with ozone. The effect of ZnO particle size and pH are also examined. According to the results, concentration of 4NCB decreased with increasing of particle size from nanosized to microsized and pH from 3.0 to 9.0. Based on the results, it suggests radical hydroxyl does not affect on the degradation of 4NCB in catalytic ozonation, but the surface of catalyst plays main role. Kinetic studies showed degradation of 4NCB followed pseudo-first-order kinetic and maximum degradation rate was observed at pH=3

Degradation of trace aqueous 4-chloro-2-nitrophenol occurring in pharmaceutical industrial wastewater by ozone

Degradation of 4-chloro-2-nitro phenol by ozonation in aqueous solution was studied in a semi batch reactor under constant ozone dosage and variable pH conditions. The effectiveness of the process was estimated based on the degree of conversion of 4-chloro-2-nitro phenol. It was observed that ozonation is more effective at alkaline reaction of medium than other conditions. The degree of conversion achieved (at the first 5 minutes of the process)at pH 9 was 99.64% compared to 99.03% and 77.35% at pH 7 and 3, respectively. Another parameter used to quantify the 4- chloro-2-nitrophenol during ozonation was the pseudo first order rate constant k [min-1]. Results showed that the rate constant of the process was approximately much higher at the alkaline pH compared to acidic ones. A considerable improvement in chemical oxygen demand removal was observed at pH above 7. At pH 9, the reduction in chemical oxygen demand at the end of the process reached 56.9 %. The degree of organically bounded nitrogen conversion to nitrate was higher at pH 3. Of the total organic carbon reduction, 15.89 % was observed at pH 9. The 4-chloro-2-nitro phenol degradation intermediate products were analyzed by mass- spectrometry. The main intermediate product was chlorophenol