Synergistic effects of 4-nitrophenol degradation using gamma irradiation combined with a advanced oxidation process

The radiation-induced degradation of 4-nitrophenol(4-NP) was performed in combination with a Fenton reagent, H_2O_2, and Ti O_2 nanoparticles to investigate the synergetic effects of radiolytical degradation combined with other advanced oxidation processes. The experimental results indicated that the degradation efficiency of 4-NP was 87.5, 57.4, and 41.0 % at a dose of 20 k Gy when its initial concentration was 100, 200, and 350 mg/L, respectively. Radiation combined with H_2O_2, the Fenton method,and Ti O_2 remarkably increased the degradation efficiency of 4-NP, showing the synergetic effects. Radiation may enhance the biodegradability of 4-NP, suggesting that it has the potential to be used as a pretreatment method in combination with the biological method for the treatment of industrial wastewater containing toxic organic pollutants. Major intermediates during the 4-NP degradation process were identified and a possible degradation pathway was tentatively proposed.

Removal of sulfonamide antibiotics from wastewater by gamma irradiation in presence of iron ions

The presence of sulfonamide antibiotics in aquatic environments has received increasing attention in recent years.Sulfadiazine(SD),a widely used heterocyclic sulfonamide pharmaceutical,has entered into the receiving water body.In this paper,gamma rays are used to irradiate samples of sulfadiazine antibiotics-containing wastewater.The results demonstrate that SD can be effectively degraded by irradiation,but the mineralization degree of SD(in terms of TOC) is not as efficient as the SD degradation.The addition of Fe^(2+) can significantly enhance the SD degradation and mineralization through the generation of hydroxyl radical by catalytic decomposition of H_2O_2 from water radiolysis.Ion chromatography analysis indicates that sulfate ions(SO_4^(2-)) and formate(HCOO^-) are the main intermediate products.Gamma irradiation is a promising technology for removing low-concentration antibiotics from water and wastewater.

Removal of cesium from radioactive wastewater using magnetic chitosan beads cross-linked with glutaraldehyde

A novel magnetic chitosan bead cross-linked with glutaraldehyde was prepared, characterized and applied for Cs(I) removal from aqueous solution. Characteristics and mechanism of Cs(I) removal were investigated. The equilibrium data of Cs(I) adsorption by magnetic chitosan beads were fitted using the Langmuir,Freundlich, Tempkin, Redlich–Peterson(R–P), Slips and Dubini–Radushkevich(D–R) models. The maximum adsorption capacity was estimated at 3.86 mg/g from the Langmuir isotherm. FTIR study revealed that N atom was mainly involved in Cs(I) sorption by magnetic chitosan.The magnetic chitosan is a promising adsorbing material for treating Cs(I)-containing radioactive wastewater.

Degradation kinetics of 2,4-dichlorophenol by gamma ray irradiation in the presence of ozone

Gamma ray-induced degradation of 2,4-dichlorophenol(DCP) in the presence of ozone has been investigated.The results show that ozone can remarkably increase the degradation rate of 2,4-DCP in aqueous solution.The degradation kinetics of 2,4-DCP can be described by the first-order reaction model,and the rate constant was0.443,0.490 and 1.247 h^(-1),respectively,for γ-ray irradiation only,γ-ray irradiation+13 mg/L O_3 and γ-ray irradiation+30 mg/L O_3.High-performance liquid chromatography analysis shows that the dechlorinated products are 4-chlorophenol,2-chlorophenol and phenol;and the oxidation products are hydroquinone,benzoquinone,maleic,fumaric,acrylic,malonic,oxalic,acetic and formic acids.The possible pathways for 2,4-DCP degradation involving all these oxidation products are tentatively proposed.Combining γ-ray irradiation with ozonation is a promising technology for removing toxic pollutants from water and wastewater.

Ozonation as an efficient pretreatment method to alleviate reverse osmosis membrane fouling caused by complexes of humic acid and calcium ion

Humic acid has been considered as one of the most significant sources in feed water causing organic fouling of reverse osmosis (RO) membranes, but the relationship between the fouling behavior of humic acid and the change of its molecular structure has not been well developed yet. In this study, the RO membrane fouling behavior of humic acid was studied systematically with ozonation as a pretreatment method to control RO membrane fouling. Furthermore, the effect of ozone on the structure ofhumic acid was also explored to reveal the mechanisms. Humic acid alone (10-90 mg/L, in deionized water) was found not to cause obvious RO membrane fouling in 45-h operation. However, the presence of Ca^2+ aggravated significantly the RO membrane fouling caused by humic acid, with significant flux reduction and denser fouling layer on RO membrane, as it was observed by scanning electron microscope (SEM) and atomic force microscope (AFM). However, after the pretreatment by ozone, the influence of Ca^2+ was almost eliminated. Further analysis revealed that the addition of Ca^2+ increased the particle size of humic acid solution significantly, while ozonation reduced the SUVA254, particle size and molecular weight of the complexes of humic acid and Ca^2+(HA-Ca^2+ complexes). According to these results and literature, the bridge effect of Ca^2+ aggregating humic acid molecules and the cleavage effect of ozone breaking HA-Ca^2+ complexes were summarized. The change of the structure of humic acid under the effect of Ca^2+ and ozone is closely related to the change of its membrane fouling behavior.