| Recently, persistent organic pollutants (POPs) are becoming hot spots concerned of environmental science research because of their teratogenic, carcinogenic, cause mutation effect and environmental hormone effect. OCPs were widely used during a long period and in a great deal, and due to the stable structure, difficult to oxidation, difficult to decompose and toxic, etc. Therefore, they can almost be detected all over the world. Natural water is a complicated biological system. Besides aqueous phase, various solid phase medium including biofilms. suspended particles and sediments are also the necessary parts of natural water. These three solid phases play a decisive role to a large extent in the migration, transformation and fate of many contaminants in the whole natural aquatic environment. Black carbon has a strong adsorption to persistent pollutants and cannot be ignored in sediment. Many studies suggest that black carbon is the most important organic constituents in adsorption organic pollutants.Used selective extraction methods to extract the main chemical compositions of solid phase medium, and the effects of main chemical compositions on HCHs and DDTs adsorption were analyzed. Chemical oxidation method was used to extract black carbon components from sediment. Compared to the black carton made from the burning of rice residues through scanning electron microscope and specific surface area. Study the mechanism of black carbon adsorption pesticide.Results show that biofilms, suspended particles and sediments and their main components had stronger adsorption ability to DDTs than to HCHs. The solid phase removed metal and organic component had similar adsorption rule. Metal oxide had little influence on the adsorption. Organic and carbonaceous kind material were the most important factors on organochlorine pesticides adsorption, and iron and manganese oxide could obviously enhance the sorption ability and the nonlinearity of the isotherms. Freundlich could fit the sorption isotherms. After removed manganese oxide the n value obviously decreased, and the solid-phase after removed organic matter and metal oxide had a greater n value than not extraction solid-phase and adsorption isotherm was close to linear.Chemical oxidation could well extract black carbon from sediment (SC), relative to the overall deviation only 5.2%. The HCHs and DDTs adsorption balance state on SC was 40h later, and gradually to HCHs and DDTs SC adsorption ability of 11.91 times and 4.23 times higher than sediments, n value was 0.4360-0.5162, and adsorption isotherms presented well nonlinear. As the concentration of HCHs and DDTs increasing its adsorption on black carbon gradually reduced and gradually trended adsorption linear. PH value on SC adsorption pesticide consequences was not significant. SC containing pesticide adsorption capacity of sediment and adsorption intensity with black carbon adding concentrations increasing and gradually strengthened; and the adsorption nonlinear isotherms on black carbon content in sediments gradually obvious increased.When the relative content of black carbon and organic carbon(fBC/fOC) lower (0.1-0.2), the organic carbon except black carbon played the leading adsorption role, when fBC/fOC had a higher value (0.35-0.6), black carbon plays a leading adsorption role, and b Koc value was be more influential.The rice straw, through controlling the calcination temperature difference in 450℃and 850℃made two black carbon, BC850 had greater specific surface area about 79.62 m2/g than BC450 about 26.54 m2/g, scanning electron microscopy could be intuitive BC850 contain more rich micropores. TOC order:activated carbon >BC850> SC> BC450> sediments, the surface area and micropores of BC450 SC, visible specific surface area, affecting the adsorption quantity size. And micropores affected the adsorption isotherms of nonlinear. The black carbon in adsorption pesticide extracted mainly centered on the pore filling mechanism... |
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