Decolorization of an azo dye Orange G in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study.

To establish cost-efficient operating conditions for potential application of Fenton oxidation process to treat wastewater containing an azo dye Orange G (OG), some important operating parameters such as pH value of solutions, dosages of H(2)O(2) and Fe(2+), temperature, presence/absence of chloride ion and concentration of the dye, which effect on the decolorization of OG in aqueous solution by Fenton oxidation have been investigated systematically. In addition, the decolorization kinetics of OG was also elucidated based on the experimental data. The results showed that a suitable decolorization condition was selected as initial pH 4.0, H(2)O(2) dosage 1.0 x 10(-2)M and molar ratio of [H(2)O(2)]/[Fe(2+)] 286:1. The decolorization of OG enhanced with the increasing of reaction temperature but decreased as a presence of chloride ion. On the given conditions, for 2.21 x 10(-5) to 1.11 x 10(-4)M of OG, the decolorization efficiencies within 60 min were more than 94.6%. The decolorization kinetics of OG by Fenton oxidation process followed the second-order reaction kinetics, and the apparent activation energy E, was detected to be 34.84 kJ mol(-1). The results can provide fundamental knowledge for the treatment of wastewater containing OG and/or other azo dyes by Fenton oxidation process.

Oxidative decomposition of p-nitroaniline in water by solar photo-Fenton advanced oxidation process.

The degradation of p-nitroaniline (PNA) in water by solar photo-Fenton advanced oxidation process was investigated in this study. The effects of different reaction parameters including pH value of solutions, dosages of hydrogen peroxide and ferrous ion, initial PNA concentration and temperature on the degradation of PNA have been studied. The optimum conditions for the degradation of PNA in water were considered to be: the pH value at 3.0, 10 mmol L(-1) H(2)O(2), 0.05 mmol L(-1) Fe(2+), 0.072-0.217 mmol L(-1) PNA and temperature at 20 degrees C. Under the optimum conditions, the degradation efficiencies of PNA were more than 98% within 30 min reaction. The degradation characteristic of PNA showed that the conjugated pi systems of the aromatic ring in PNA molecules were effectively destructed. The experimental results indicated solar photo-Fenton process has more advantages compared with classical Fenton process, such as higher oxidation power, wider working pH range, lower ferrous ion usage, etc. Furthermore, the present study showed the potential use of solar photo-Fenton process for PNA containing wastewater treatment.

Degradation of azo dye Acid black 1 using low concentration iron of Fenton process facilitated by ultrasonic irradiation.

A combination of ultrasonic and low concentration iron (<3 mgL(-1)) of Fenton process (US/Fenton) has been used to treat wastewater containing Acid black 1 (AB1). The results show that the oxidation power of low concentration iron of Fenton could be significantly enhanced by ultrasonic irradiation. The degradation of AB1 in aqueous solution by US/Fenton can receive better results compared with either Fenton oxidation or ultrasonic alone. Many operational parameters, such as ultrasonic power density, the pH value, the Fe(2+) dosage, the H(2)O(2) dosage, AB1 concentration and the temperature, affecting the degradation efficiency were investigated. Also, the effects of various inorganic anions (such as Cl(-), NO(3)(-), CO(3)(2-), etc.) on the oxidation efficiency of US/Fenton were studied. Under the given test conditions, 98.83% degradation efficiency was achieved after 30 min reaction by US/Fenton. The effect of various inorganic anions was in the following decreasing order: SO(3)(2-)>CH(3)COO(-)>Cl(-)>CO(3)(2-)>HCO(3)(-)>SO(4)(2-)>NO(3)(-). The results show that the US/Fenton can be an effective technology for the treatment of organic dyes in wastewater.

A kinetic study on the degradation of p-nitroaniline by Fenton oxidation process.

A detailed kinetic model was developed for the degradation of p-nitroaniline (PNA) by Fenton oxidation. Batch experiments were carried out to investigate the role of pH, hydrogen peroxide and Fe(2+) levels, PNA concentration and the temperature. The kinetic rate constants, k(ap), for PNA degradation at different reaction conditions were determined. The test results show that the decomposition of PNA proceeded rapidly only at pH value of 3.0. Increasing the dosage of H(2)O(2) and Fe(2+) enhanced the k(ap) of PNA degradation. However, higher levels of H(2)O(2) also inhibited the reaction kinetics. The k(ap) of PNA degradation decreased with the increase of initial PNA concentration, but increased with the increase of temperature. Based on the rate constants obtained at different temperatures, the empirical Arrhenius expression of PNA degradation was derived. The derived activation energy for PNA degradation by Fenton oxidation is 53.96 kJ mol(-1).

Upregulation of heme oxygenase-1 in Kupffer cells blocks mast cell degranulation and inhibits dendritic cell migration in vitro.

Kupffer cells (KCs) influence liver allografts by interacting with other non­parenchymal cells. However, the exact mechanism remains unclear. Upregulation of heme oxygenase-1 (HO-1) in KCs upon interaction with mast cells (MCs), and the effects on dendritic cell (DC) function, were investigated in the present study. KCs, MCs and DCs were prepared from 8­10­week­old C57BL/6 mice. KCs were pretreated with PBS, dimethyl sulfoxide, hemin (50 µM; HO­1 inducer), and zinc protoporphyrin (50 µM; HO­1 inhibitor) for 8 h. Reverse transcription­polymerase chain reaction and western blotting was performed to determine HO­1 mRNA and protein levels in KCs, respectively. C­C motif chemokine receptor 7 (CCR7) surface molecules were measured using flow cytometry, and prostaglandin E2 (PGE2), C­C motif chemokine ligand (CCL) 19 and CCL21 were measured by ELISA. The Transwell model was used to investigate the migration of DCs. Pretreatment of KCs with hemin induced HO­1 transcription and protein expression, and interacted with and stabilized MC membranes. When co­cultured with MCs, the expression of CCR7 on DCs was reduced, and PGE2, CCL19 and CCL21 were similarly decreased. DC migration was also impaired. Upregulation of HO­1 in KCs blocked MC degranulation and reduced DC migration.

[N2O emissions from agricultural ecosystem in Sichuan-Chongqing region].

A regional nitrogen cycling model IAP-N was adopted to estimate nitrous oxide (N2O) emission from the agro-ecosystem in the Sichuan-Chongqing Region during 1990-2004. The county level agricultural activities data were used, and Sichuan-Chongqing Region was divided into four sub-areas by the geographical characteristics, environment and local climatic conditions and administrative division. The results showed that annual averaged N2O emissions (in nitrogen gauge) in 1990-1994, 1995-1999, 2000-2004, respectively, were 52.3, 58.2, 62.0 Gg/a, of which 55% came from the N2O direct emission of the fertilized croplands. They were 29.6 (7.6-63.3), 33.0 (8.4-71.8), 34.0 (8.5-75.8) Gg/a, equals to 4.73, 5.39, 6.11 kg/(hm2 x a), respectively. Upland/glebe was the primary source of the N2O direct emission. Meanwhile, paddy-upland rotation system also played an important contribution to it. The increasing rates of N2O emission from agro-ecosystem and N2O emission flux in cropland were much higher in 1995-1999 than in 1990-1994. The N2O emission flux in the cropland showed a continuous increasing trend in 2000-2004, but the increasing rates of total N2O emission from agro-ecosystem were stagnant due to the decrease of arable land area. The N2O emission of agro-ecosystem mainly came from Chengdu Plain and Chongqing. The contributions of different sources to the total N2O emission of agro-ecosystem were variable in the region. For instance, the primary source of N2O emission was the direct emission from croplands in Chengdu Plain and Chongqing, whereas, in northwest region of Sichuan province was the N2O emission induced by grazing. The results will provide a scientific basis for policy maker to make fertilizer effectively applied and mitigate GHG emission from agro-ecosystem of Sichuan-Chongqing Region.

[Agro-ecosystem ammonia emission in Sichuan-Chongqing region].

Ammonia (NH3) emission from agro-ecosystem in the Sichuan-Chongqing region during 1990-2004, was estimated by the regional nitrogen cycling model IAP-N. The county level agricultural activities data were used, and Sichuan-Chongqing region was divided into four sub-areas by the geographical characteristics , environment and local climatic conditions and administrative division. The results showed that average annual ammonia emissions (in nitrogen gauge) in 1990-1994, 1995-1999, 2000-2004 were 626.7, 670.5 and 698.8 Gg x a(-1) respectively. The ammonia emission appeared increasing trend, whereas, the contribution of various ammonia sources presented little change. For instance, in 2000-2004, the contributions of NH3 emission from fertilized cropland, manure management system and field residues burning to the total ammonia emission of agro-ecosystem in the Sichuan-Chongqing region were 53%, 46% and 1%, equals to 374.9, 318.2 and 5.6 Gg x a(-1) respectively. But the contributions were variable in different regions. Ammonia emission was primarily induced by fertilized cropland in Chengdu plain and Chongqing hilly area, whereas, in northwest sub-region of Sichuan province was manure management system. The geographical distribution of ammonia emission from agro-ecosystem in the Sichuan-Chongqing region was generally "east high and west low". Ammonia emissions in sub-regions of Chongqing hilly area, Chengdu plain, southwest and northwest sub-regions were 165.6, 408.8, 85.9 and 38.8 Gg x a(-1), respectively, during 2000-2004. At the same time, ammonia density were 20 and 28 kg x (hm2 x a)(-1) in sub-regions of the Chongqing hilly area and the Chengdu plain, whereas, 9.1 and 1.6 kg x (hm2 x a)(-1) in southwest and northwest sub-regions, respectively. The results will provide a scientific basis for making fertilizer effectively applied and mitigate NH3 and GHG emissions from agro-ecosystem of Sichuan-Chongqing region.