Removal of chloropyrifos ethyl, tetradifon and chlorothalonil pesticide residues from citrus by using ozone.

The removal of chloropyrifos ethyl, tetradifon and chlorothalonil pesticide residues from the lemon, orange and grapefruit matrices were achieved by ozonation. All of chlorothalonil residues adsorbed onto the orange matrix were completely removed after 5 min ozonation. The highest removal percentages of tetradifon and chloropyrifos ethyl were achieved as 98.6 and 94.2%, respectively for the lemon and grapefruit matrices. All of diffused chlorothalonil and chloropyrifos ethyl residues were completely removed from both orange and grapefruit matrices after 5 min ozonation. Increasing of applied ozone dosage was not significantly effect on the removal percentages of pesticides whereas increasing of ozonation temperature caused a negative effect on the removal percentages of pesticides. The washing of the matrices with tap water was not as effective as ozonation in the removal of residual pesticides. Our results show that ozone treatment has a great potential for removing of residual pesticides from lemon, orange and grapefruit matrices.

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

This 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 0.30-1.82 mM, 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 0.223 min(-1). Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5 min and 30 min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10 min, 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 26 min.

Detection of double bond-ozone stoichiometry by an iodimetric method during ozonation processes.

In this study, the stoichiometry of decolorization of four dyes (Basic Yellow 28, Malachite Green, Reactive Black 5 and Reactive Red 198) was investigated using ozonation processes. The decolorization of Basic Yellow 28 (BY28) and Malachite Green (MG) was optimal at an acidic pH value of 3, whereas decolorization of Reactive Black 5 (RB5) and Reactive Red 198 (RR198) was optimal at a basic pH of 10. Stoichiometric Ratios (SR) between ozone and dyes were calculated to be 3.5, 7.1, 11 and 16.1 for BY28, MG, RB5 and RR198, respectively. The correlation between ozone-double bond (DB) with the best linear fit and the least relative error (epsilon (%)) was between aromatic ring number (A(N)(R)) and SR, with regression coefficients of 0.993 and 4.6, respectively. Also, the relationship between total double bond number (DBN(T))-SR had respective values of 5.1 and 0.983 for the epsilon (%) and regression coefficient. Additionally, the pseudo-first order decolorization rate constants, k', were decreased from aromatic ring number 2(A(2)(R)) to aromatic ring number 5(A(5)(R)).

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

Biosorption 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 degrees C, respectively. The theoretical max biosorption capacity of activated sludge was 294 mg g-1 at 20 degrees 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.

Comparison of the treatment methods efficiency for decolorization and mineralization of Reactive Black 5 azo dye.

Degradation of Reactive Black 5 (RB5), a well-known non-biodegradable disazo dye, has been studied using UV/TiO2, wet-air oxidation (WAO), electro-Fenton (EF) and UV/electro-Fenton (UV/EF) advanced oxidation processes (AOPs). The efficiency of substrate decolorization and mineralization in each process has been comparatively discussed by decreases in concentration and total organic carbon content of RB5 solutions. The most efficient method on decolorization and mineralization was observed to be WAO process. Mineralization efficiency was observed in the order of WAO>UV/TiO2>UV/EF>EF. Final solutions of AOPs applications after 90 min treatment can be disposed safely to environment. Photocatalytic degradation kinetics of RB5 successfully fitted to Langmuir-Hinshelwood (L-H) kinetics model. The values of second order degradation rate constant (k'') and adsorption constant (K) were determined as 5.085 mg L(-1)min(-1) and 0.112 L mg(-1), respectively.

Comparison of several advanced oxidation processes for the decolorization of Reactive Red 120 azo dye in aqueous solution.

In this study UV/TiO2, electro-Fenton (EF), wet-air oxidation (WAO), and UV/electro-Fenton (UV/EF) advanced oxidation processes (AOPs) have been applied to degrade Reactive Red 120 (RR120) dye in aqueous solution. The most efficient method on decolorization and mineralization of RR120 was observed to be WAO process. Photocatalytic degradation of RR120 by UV/TiO2 have been studied at different pH values. At pH 3 photocatalytic degradation kinetics of RR120 successfully fitted to Langmuir-Hinshelwood (L-H) kinetics model. The values of second order degradation rate (k") constant and adsorption constant (K) were determined as 4.525 mg L(-1) min(-1) and 0.387 L mg(-1), respectively. Decolorization efficiency observed in the order of WAO > UV/TiO2 = UV/EF > EF while WAO > UV/TiO2 > UV/EF > EF order was observed in TOC removal (mineralization). For all AOPs, it was found that degradation products in reaction mixture can be disposed safely to environment after 90 min treatment.

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

In this study, Fenton, UV/Fenton, UV/H2O2, UV/Fe2+ 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 H2O2. 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+.