Degradation of aldrin in adsorbed system using advanced oxidation processes: Comparison of the treatment methods

PubMedID: 15177100In this study, Fenton, UV/Fenton, UV/H2O2, UV/Fe 2+ advanced oxidation processes have been applied for degradation of aldrin adsorbed on Na-montmorillonitte and activated carbon. Aldrin adsorbed on Na-montmorillonitte was degraded more efficiently than that of on activated carbon. For example, in UV/Fenton technique 95% of aldrin was removed from Na-montmorillonitte while 50% degradation was observed on activated carbon. Degradation of aldrin adsorbed on Na-montmorillonitte has also been achieved effectively using UV/Fe2+ technique despite the absence of H 2O2. All AOPs but Fenton have been observed nearly equally effective for degradation of aldrin on Na-montmorillonitte sorbent. Fenton reaction exhibited least activity in degradation aldrin adsorbed on Na-montmorillonitte. The experiments with activated carbon sorbent indicated that phenyl groups in activated carbon structure and aldrin molecules exhibited competitive behavior on reaction with OH• radicals. The results of infrared spectroscopy support this assumption. The degradation efficiency of aldrin using activated carbon sorbent was determined in the following order: UV/Fenton>UV/H2O2>Fenton>UV/Fe2+. © 2003 Elsevier B.V. All rights reserved

Preparation of ceramic pigments by sol-gel and combustion methods

Ceramic pigments are extensively used in the decoration of ceramic wares. These pigments need to be stable (homogeneity, colour intensity, crystallinity) at high temperatures in a glaze. Malayaite ceramic pigments (CaSnSiO5) in this research study have been prepared in two ways: by means of a sol-gel method and a combustion method. The starting substances in the sol-gel method was TEOS, Ca(NO3)26H2O, SnCl4 and Ni(NO3)26H2O whereas in the combustion reaction the same substances with the addition of CH4N2O (urea) were used. In order to elucidate the structural evolution of these pigments with heat-treatment, infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used

Degradation of bisphenol A by ozonation and determination of degradation intermediates by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry

In this study, bisphenol A (BPA), an endocrine disrupter, was removed by ozonation process. During ozonolysis, degradation kinetics and degradation intermediates of BPA were determined and degradation stoichiometry was also calculated. The degradation of BPA was found to be optimal at pH 3.0 and BPA solution with 0.509mM concentration was completely degraded after 25min ozonation time. The stoichiometric ratio between ozone and BPA were calculated to be 10.30. The pseudo-first order degradation rate constant, kObs, decreased in the range of 19.3-13.3s-1 when the initial concentration of BPA was raised from 0.051 to 0.509mM. In addition, the second order rate constant, kapp(BPA), was also calculated in the range of 2.18×104-3.56×104M-1s-1. Henry's constant, kH, increased as 5.5% depending on growth of ionic strength of BPA solution during ozonation. As a result of the increase of kH, dissolved ozone reduced throughout the ozonation. Ten different intermediates occurred during the ozonation of BPA and were identified via GC-MS and LC-MS/MS. Malonic and oxalic acids were observed among the intermediates in the first 5min of ozonation and taken as markers of mineralization. kTOC' value was calculated as 2.11M-1min-1 for BPA mineralization and the mineralization of ozonation was achieved about 30% at the end of 25min ozonation. © 2013 Elsevier B.V

Degradation of 4-chloro-2-methylphenol in aqueous solution by UV irradiation in the presence of titanium dioxide

The degradation of 4-chloro-2-methylphenol (PCOC) in aqueous solution by UV irradiation in the presence of TiO2 has been studied. It was found that only 51.4% of PCOC was degraded by this process. The improvement in degradation levels were achieved by using various oxidants as electron scavenger. Periodate ion was found to be much more efficient oxidant than the others in improving the degradation of PCOC via formation of reactive species. The effect of the oxidants used in the UV/TiO2 systems on the degradation rate of PCOC were found to be in the order of IO4 - > BrO3- > H2O2 > O2> ClO3-. Addition of metal ions to UV/TiO2/H2O2 system increased the photodegradation rate of the organic substrate. The effect of Mn2+, Cr3+, Fe2+ and Fe3+ metal ions on degradation of PCOC in the TiO2/UV/H2O2/Mn+ system was found to be in the order of Fe3+ > Fe2+ > Mn2+ > Cr3+. Langmuir-Hinshelwood rate expression was employed for the degradation of PCOC by the UV/TiO2/O2 system and adsorption equilibrium constant and the rate constant were determined to be 74.16 mM-1 and 0.0081 mM min-1, respectively. © 2004 Elsevier B.V. All rights reserved

Study of Cu(II) biosorption by dried activated sludge: Effect of physico-chemical environment and kinetics study

PubMedID: 15811681Biosorption is a recent technology used to remove heavy metal ions from aqueous solutions. The biosorption of copper ions from aqueous solution by dried activated sludge was investigated in batch systems. Effect of solution pH, initial metal concentration and particle size range were determined. The suitable pH and temperature for studied conditions were determined as 4.0 and 20°C, respectively. The theoretical max biosorption capacity of activated sludge was 294 mg g-1 at 20°C for <0.063 mm particle size. The equilibrium data fitted very well to both Langmuir and Freundlich isotherm models. The pseudo first and second-order kinetic models were used to describe the kinetic data. The experimental data fitted to second-order kinetic model. The particle size and initial metal concentration were effected the biosorption capacity of dried activated sludge. An increase in the initial metal concentration increases of biosorption capacity, which also increases with decreasing particle size. Dried activated sludge has different functional groups according to the FT-IR results. © 2005 Elsevier B.V. All rights reserved

Decolorization of the textile dyes reactive blue 220, acid red 414 and basic yellow 28 by ozone and biodegradation of oxidation products

In this study, decolorization of Reactive Blue 220, Acid Red 414 and Basic Yellow 28, decolorization kinetics, and biodegradability of intermediates after ozonolysis were studied. Effect of pH on ozonolysis was studied, and pH 3 was the best among pH values of 3, 7 and 11. The decolorization kinetics of these dyes can be described by a first-order reaction model, and the first-order rate constants ofRB 220, AR 414 and BY28 were 0.175-0.1303, 0.164-0.096 and 0.2092-0.1154 min-1, respectively. Total organic removal was determined to be 24.74, 17.15 and 23.37% for RB220, AR 414 and BY 28, respectively, after 30-min ozonation of 800 mg L-1 dye. The respirometric biologic oxygen demand of Pseudomonas putida (30-min ozone treatment of 800 mg L-1 of dye) was 490, 460 and 451 for RB220, AR 414 and BY 28, respectively. Our results showed that ozonation is an effective way to remove the color from aqueous solutions of these dyes, and that the by-products are non-toxic to P. putida. © by PSP

Decolorization of malachite green, decolorization kinetics and stoichiometry of ozone-malachite green and removal of antibacterial activity with ozonation processes

PubMedID: 21115218This study aimed to identify degradation intermediates and to investigate the stoichiometry of decolorization and degradation, decolorization kinetics, and removal of antibacterial activity of malachite green (MG) using ozonization processes. The decolorization of MG was optimal at an acidic pH value of 3 based on molecular ozone attack on MG molecules. The stoichiometric ratio of decolorization between ozone and MG was calculated to be 7.0 with a regression coefficient of 0.995, whereas the ratio for degradation was calculated as 13.1 with a regression coefficient of 0.998. With MG concentrations in the range of 0.30-1.82mM, the concentration of decolorized MG increased with higher initial concentrations of MG, whereas the ozonolytic decolorization rates of MG, decreased with increasing initial concentration. The pseudo-first-order degradation rate constants (k') decreased with the initial concentration and ranged from 0.769 to 0.223min-1. Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5min and 30min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10min, the decrease of antibacterial activity was very low (10%) for Bacillus subtilis and Staphylococcus epidermidis because the degradation intermediates, phenol and benzoic acid, also have antibacterial activity. The antibacterial activity of both MG and its intermediates were removed successfully with ozonation times above 26min. © 2010 Elsevier B.V