Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C1835664 (TOC)
 2,763 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study the treatment efficiency of different AOPs (O3/OH- H2O2/UV-C and TiO2/UV-A) were compared for the oxidation of simulated reactive dyebath effluent containing a mixture of monochlorotriazine type reactive dyes and various dye auxiliary chemicals at typical concentrations encountered in exhausted reactive dyebath liquors. A525 (color), UV280 (aromaticity) and TOC removal rates were assessed to screen the most appropriate oxidative process in terms of reactive dyebath effluent treatment. Special emphasis was laid on the effect of reaction pH and applied oxidant (O3, H2O2) dose on the observed reaction kinetics. It was established that the investigated AOPs were negatively affected by the Na2CO3 content (= 867 mg/L) which is always present at high concentrations in dychouse effluents since it is applied as a pH buffer and dye fixation agent during the reactive dyeing process. The ozonation reaction exhibited almost instantaneous decolorization kinetics and a reasonable TOC reduction rate. It appeared to be stable under the investigated advanced oxidation conditions and outranked the other studied AOPs based on the above mentioned criteria. Besides, the electrical energy requirements based on the EE/O parameter (the electrical energy required per order of pollutant removal in 1 m3 wastewater) was calculated for the homogenous AOPs in terms of decolorization kinetics. In view of the electrical energy efficiency, ozonation and H2O2/UV-C oxidation at the selected treatment conditions appear to be promising candidates for full-scale dyehouse effluent decolorization.
 ...
PMID:Advanced oxidation of a reactive dyebath effluent: comparison of O3, H2O2/UV-C and TiO2/UV-A processes. 1190 71

The photocatalytic oxidation (PCO) of a monoazo dye Procion Red MX-5B under various physico-chemical conditions was investigated. Degradation of the dye by PCO was enhanced by augmentation in UV intensity, titanium dioxide and hydrogen peroxide concentrations but was inhibited by increase in initial dye concentration. The PCO process was affected by pH in a peculiar way. In the presence of 100 mg/l of TiO2 and the absence of H2O2, the highest reaction rate was observed when the initial pH was 10. With 500 mg/l of TiO2 and 10 mM of H2O2, the reaction was the fastest at initial pH of 3-5. The optimal conditions for the degradation of the dye, at an UV intensity of 17 mW/cm2, were determined to be: TiO2 concentration, 500 mg/l; initial H2O2 concentration, 10 mM; initial pH, 5.0. Monitoring of TOC loss showed that the dye was mineralized by 90% within 80 min under these conditions. Nevertheless, the persistence of a low level of TOC indicated that mineralization was not complete and dead-end product(s) which was (were) resistant to PCO might have accumulated.
 ...
PMID:Degradation of azo dye Procion Red MX-5B by photocatalytic oxidation. 1192 71

Advanced chemical oxidation of raw and biologically pretreated wastewater by ozonation, H2O2/UV-C treatment and the successive combination of ozonation and H2O2/UV-C oxidation was investigated. For the raw textile wastewater, the application of successive O3 + H2O2/UV-C oxidation enhanced the COD and TOC removal efficiency of the H2O2 (50 mM)/UV-C process by a factor of 13 and 4, respectively. In case of the biotreated textile wastewater, the preliminary ozonation step increased COD removal of the H2O2 (10 mM)/UV-C treatment system from 15% to 62%, and TOC removal from 0% to 34%, but did not appear to be more effective than applying a single ozonation process in terms of TOC abatement rates. Enhancement of the biodegradability was more pronounced for the biologically pre-treated wastewater with a two fold average increase in the BOD5/COD ratio for the studied chemical oxidation systems.
 ...
PMID:The effect of pre-ozonation on the H2O2/UV-C treatment of raw and biologically pre-treated textile industry wastewater. 1220 Nov 15

Nearly 91% of organic pollutants in Hong Kong leachate could be effectively removed by the UASB (upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD (chemical oxygen demand) of leachate was lowered from an average of 5620 mg/L to 1910 mg/L after the UASB treatment at 37 degrees C, and was further lowered to 513 mg/L after fenton coagulation. The remaining refractory residues could be further removed by photochemical oxidation with the addition of H2O2. The BOD/COD ratio was greatly increased from 0.062 to 0.142, indicating the biodegradability of organic residues was improved. The photochemical oxidation for the fenton-coagulation supernatant was most effective at pH 3-4, with the addition of 800 mg/L of H2O2, and UV radiation time of 30 minutes. The final effluent contained only 148 mg/L of COD, 21 mg/L of BOD (biochemical oxygen demand) and 56 mg/L of TOC (total organic carbon).
 ...
PMID:Photo-assisted fenton oxidation of refractory organics in UASB-pretreated leachate. 1221 91

The release performances of an organic and mineral activated sludge matrix were studied for a wide range of disintegration treatments like mechanical, thermal, thermal-chemical and oxidative disintegration techniques. The maximal COD release was 35% of total COD after 24 hours contact time at 95 degrees C. A limiting value of 60% COD release was obtained for 500 and 700 bars after 10 passes. Concerning theoxidative disintegration techniques (O3 and H2O2), a limiting value of around 60-65% of TOC release was observed. Therefore, it was hypothesised that thermal and mechanical treatments allow mainly for breaking apart the micro-organisms while the oxidative treatment destroys the sludge flocs and disrupts the micro-organisms. A release effect of the mineral fraction is observed only oxidative disintegration techniques.
 ...
PMID:A comparative study between mechanical, thermal and oxidative disintegration techniques of waste activated sludge. 1247 56

A new Gas-Induced Reactor (GIR) has been developed to improve the efficiency of ozone utilization in water treatment. In this study, the GIR was used to investigate the behavior of ozonation of aqueous phenol solution by means of O3 and O3/H2O2 processes in order to explore the feasibility and efficiency of treating such wastewater using the new GIR. The study observed the decomposition of phenol, utilization of ozone, and variation of TOC during ozonation, varying pH values, phenol initial concentrations, ozone input concentrations, and hydrogen peroxide dosages. The study concluded that the new GIR was capable of performing effective and efficient ozonation of phenolic wastewater, maintaining high ozone utilization ratios at all experimental pH values and initial phenol and ozone concentrations. The optimal pH condition for phenol removal was around 11. The best molar ratios of initial hydrogen peroxide over input ozone among the performed experiments were about 20 at pH 7 and 10 at pH 9 and 11. The primary operational energy used for treating a tonne of wastewater was 66 MJ, giving treatment costs of about USS1.0 per tonne.
 ...
PMID:The effectiveness of a new gas-induced reactor in treating phenolic wastewater by ozonation and hydrogen peroxide. 1271 68

Photocatalytic degradations of alachlor in TiO2 suspensions with and without the use of hydrogen peroxide were studied using two different monochromatic UV irradiations (300 and 350 nm). Direct photolysis of alachlor was a rather slow process, but the addition of TiO2 enhanced the reaction rates by 12 and 26 times using 300 and 350 nm UV irradiation, respectively. The results showed that a low H2O2 dosage in photocatalysis using 300 nm UV would enhance the rates by 3.3 times, but an overdose of H2O2 will retard the rate due to the hydroxyl radicals are consumed. However, this process is impracticable at 350 nm due to the absorption characteristic of H2O2. A neutral initial pH level was found to favor the H2O2 assisted photocatalysis at 300 nm UV illumination. Eleven major intermediates were identified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and MS/MS. The major degradation mechanisms of H2O2-assisted alachlor photocatalysis include dechlorination, dealkylation, hydroxylation, cyclization, scission of C-O bond, and N-dealkylation. Bell-shaped evolution profiles of different intermediates were observed. Degradation pathways were proposed accordingly to illustrate series of degradation steps. The TOC analysis revealed the different stages of the reaction.
 ...
PMID:The hydrogen peroxide-assisted photocatalytic degradation of alachlor in TiO2 suspensions. 1278 42

Response Surface Methodology (RSM) was employed to investigate the effect of TOC ratio of high molecular weight organic matter (HMWOM) to low molecular weight organic matter (LMWOM), the LMWOM concentration and hydrogen peroxide to ferrous ion molar ratio on COD removal during the treatment of sanitary landfill leachate with Fenton reagents. The high and low levels of HMWOM/LMWOM, the LMWOM concentration and H2O2/Fe2+ were from 14 to 38, 975 to 3000 mg/L, and 1.75 to 4.00 respectively. Using the software of Design--Expert 5, a response surface quadratic model in terms of actual factors was obtained based on the experimental data, and COD removal contour plots were derived from the model accordingly. It showed that COD removal increased with the increase of HMWOM to LMWOM ratio, but decreased with increasing LMWOM concentration. There existed an optimal hydrogen peroxide to ferrous ion molar ratio so that the highest COD removal efficiency could be achieved.
 ...
PMID:[Evaluation of Fenton process for the treatment of sanitary landfill leachate with Response Surface Methodology]. 1455 75

Mineralization of a 5 mM EDTA solution at pH 3 was evaluated via TOC removal under UV-C irradiation in the presence of H2O2 at various conditions. The highest TOC removal (78%) was obtained using a 40:1 H2O2/EDTA molar ratio, after 540 min irradiation. However, a 20:1 ratio gave slightly lower results, being economically more attractive. Best results of TOC removal were obtained under pH controlled conditions. Addition of TiO2 (1 g l(-1)) was detrimental, even in the presence of H2O2, indicating that at this concentration, TiO2 inhibits the mineralization, probably by scattering or by screening of the light.
 ...
PMID:Removal of EDTA by UV-C/hydrogen peroxide. 1466 8

Hydrogen peroxide decomposition and trichloroethylene (TCE) oxidation kinetics were studied through batch slurry experiments, performed on two TCE contaminated soils (a sandy soil and a clay soil), characterized by different texture and organic fraction; besides, experiments were also performed on sandy soil columns, in order to more closely reproduce the typical conditions of an in situ treatment. The results of the batch tests indicated that hydrogen peroxide lifetime was correlated to the oxidation efficiency; namely, complete TCE oxidation was achieved only for the conditions characterized by longer hydrogen peroxide lifetime, that was obtained by addition of a proper stabilizer (KH(2)PO(4)). The soil properties were also observed to influence both hydrogen peroxide decomposition and TCE oxidation kinetics, probably as a consequence of the different TOC content. The soil column experiments, performed on 10, 20, and 30 cm long columns, indicated that hydrogen peroxide decomposition, which was almost complete at 30 cm depth, was on the contrary negligible when the stabilizer was added. In agreement with this observation, the performance of TCE oxidation were greatly improved in the latter case. Based upon the collected results, it can be concluded that hydrogen peroxide experiments may be useful, at least in the first screening phase of the design activity, for selecting, among the different operating conditions, those that may be potentially more effective for the oxidation treatment.
 ...
PMID:Application of H2O2 lifetime as an indicator of TCE Fenton-like oxidation in soils. 1507 17


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>