Ozone oxidation combined with activated carbon adsorption (O(3)/AC) has recently started to be developed as a single process for water and wastewater treatment. While a number of aspects of aqueous ozone decomposition are well understood, the importance and relationship between aqueous ozone decomposition and organic contaminant degradation in the presence of activated carbon is still not clear. This study focuses on determining the contribution of homogeneous and heterogeneous reactions to organic contaminants removal in O(3)/AC system. Benzothiazole (BT) was selected as a target organic pollutant due to its environmental concern. A reactor system based on a differential circular flow reactor composed by a 19 cm(3) activated carbon fixed bed column and 1 dm(3) storage tank was used. Ozone was produced from pure and dry oxygen using an Ozocav ozone generator rated at 5 g O(3)h(-1). Experimental results show that BT removal rate was proportional to activated carbon dosage. Activated carbon surface contribution to BT oxidation reactions with ozone, increased with pH in absence of radical scavengers. The radical reaction contribution within the pH range 2-11 accounted for 67-83% for BT removal in O(3)/AC simultaneous treatment. Results suggest that at pH higher than the pH of the point of zero charge of the activated carbon dissociated acid groups such as carboxylic acid anhydrides and carboxylic acids present on activated carbon surface could be responsible for the observed increase in the ozone decomposition reaction rate. A simplified mechanism and a kinetic scheme representing the contribution of homogeneous and heterogeneous reactions on BT ozonation in the presence of activated carbon is proposed. 相似文献
Regional Environmental Change - The State of Mato Grosso in Brazil has undergone intensive land use changes over the past decades. Native ecosystems have been converted into agrosystems for the... 相似文献
Futures trading has been introduced for aluminium and oil in recent years and the range of contracts available on various minerals and oil products continues to widen. Concern has been expressed by producers of a number of minerals, including nickel and platinum, that the introduction of futures trading may introduce a speculative element to price determination that will create inappropriate or excessively volatile prices. It is the purpose of this article to analyse the role of futures trading in relation to trade in underlying commodities in general and especially for trade in minerals and oil. Evidence from oil and platinum markets, in particular, is adduced and examined in the light of earlier evidence of the influence of futures trading on underlying commodities. The contribution of futures trading is examined in detail and conclusions are reached on the significance of futures trading for minerals and oil. 相似文献
It is in the nature of astrophysics that many of the processes and most of the objects one tries to understand are physically inaccessible. Thus, it is important that those aspects that can be studied in the laboratory be rather well understood. The electron-screening effect on fusion reactions addresses one such aspect: the observed effect under laboratory conditions is presently not understood. 相似文献
In the Amazon basin, few studies have focused on environmentally sound land-use alternatives that are linked to markets. This paper analyzes land uses carried out by traditional inhabitants ( ribeirinhos ) on three islands in the Amazon estuary. Management of the native floodplain forest is the most extensive form of land use on these islands. Such management varies in response to local economic and ecological conditions but invariably targets key nontimber forest resources destined for local markets, requires minimal input of labor and capital, and maintains a considerable stock of biotic resources. While restricted to a specific forest type, this form of land use is associated with relatively high population densities and, if supported by appropriate development policies, could provide an environmentally sound land-use alternative for hundreds of thousands of rural inhabitants of Amazonia. 相似文献
Titanium dioxide photocatalysis, using 200 mgl−1 of TiO2, and photo-Fenton, using 20 mg l−1 of iron, were applied to the treatment of dimethoate dissolved in water at 50 mg l−1. A heterogeneous photocatalysis test was performed in a 35-l solar pilot plant with Compound Parabolic Collectors (CPCs)
under natural illumination. A homogeneous photocatalysis test was performed in a different solar pilot plant with four CPC
units and a total volume of 75 l. In this work total disappearance of dimethoate and 90% of mineralization were attained in
both solar treatments. Treatment time, hydrogen peroxide consumption and ferric phosphate precipitation during photo-Fenton
treatment were discussed.
An erratum to this article can be found at 相似文献
Leaching of acidic herbicides (2,4-D, flumetsulam, and sulfentrazone) in soils was estimated by comparing the original and modified AF (Attenuation Factor) models for multi-layered soils (AFi). The original AFi model was modified to include the concept of pH-dependence for Kd (sorption coefficient) based on pesticide dissociation and changes in the accessibility of soil organic functional groups able to interact with the pesticide. The original and modified models, considering soil and herbicide properties, were applied to assess the leaching potential of selected herbicides in three Brazilian soils. The pH-dependent Kd values estimated for all three herbicides were observed to be always higher than pH-independent Kd values calculated using average Koc data, and therefore the original AFi model overestimated the overall leaching potential for the soils studied. 相似文献
This work describes the nitration of aromatics upon near-UV photolysis of nitrate and nitrite in aqueous solution and upon photocatalytic oxidation of nitrite in TiO2 suspensions. Phenol is used in this work as a model aromatic molecule and as a probe for *NO2/N2O4. The photoinduced nitration of phenol in aqueous systems occurs upon the reaction between phenol and *NO2 or N2O4, and is enhanced by the photocatalytic oxidation of nitrite to *NO2 by TiO2. Aromatic photonitration in the liquid phase can play a relevant role in the formation of nitroaromatics in natural waters and atmospheric hydrometeors, thus being a potential pathway for the condensed-phase nitration of aromatics. Furthermore, the photoinduced oxidation of nitrite to nitrogen dioxide suggests a completely new role for nitrite in natural waters and atmospheric aerosols. 相似文献
Forests provide ecosystem services, including timber production. In some cases, private forest owners perform management actions in order to enhance the provision of such services, or they may be encouraged by public policies and payments. This paper focuses specifically on the decision to set forest land aside for biodiversity conservation, as part of the more general question of the efficiency of multiple-use vs. specialised management of forest lands. We propose an econometric analysis to identify factors in the set-aside choice and measure the impact of this decision on forest management costs. The results show that the set-aside choice depends on the landowners’ income and motivations related to forest amenities. The choice of specialised management, as reflected in the set-aside decision, has a significant and positive impact on the intensity of management in the remainder of the forest and on management costs. From a policy implications point of view, these results suggest that instruments such as forest certification, subsidies and reverse auctions for conservation will be most likely to attract the interest of those forest owners with personal motivations and forest properties that offer both benefit and cost advantages in opting for such specialised management strategies.