Effects Of Dissoved Organic Matter On Adsorption Of Pesticides And Polycyclic Aromatic Hydrocarbons To Black Carbon

Black carbon (BC), a product of incomplete combustion of fossil fuels and vegetation, is ubiquitous in the environment and is an important adsorbent in soils for contaminants. Recent studies reported that natural dissolved organic matter (DOM) can attenuate the adsorption capacity of BC for organic contaminants. In this paper, BCs of high surface areas were prepared from rice straws and firwood. Four Model DOMs (Tannic acid (TA), Pentagalloylglucose (PA),3-o-Galloylmucic acid (OA) and Gallic acid (GA)) and Two natural DOMs (humic acids(HA) and fulvic acids (FA)) were used as preloading adsorbates. The formers differed in molecular size and molecular weight, and the latters were collected from natural soil. Three typical target compounds(propanil, naphthalene (Naph) and phenanthrene (Phe)) were selected as adsorbates to evaluate the effects of DOM preloading on the adsorption.First, the effect of model DOM on propanil sorption to BC was evaluated. It showed that the preloading DOM exhibited the stronger adsorptive attenuation of propanil than the aqueous competitive DOM. The percent reduced adsorption of propanil mainly relies on the property of the DOMs rather than the characteristic of the carbons. Macromolecules (TA, PA) may cause the stronger influence of propanil adsorption than the small molecular DOM (OA, GA). The extent of the inhibitive adsorption of propanil chiefly depends on the molecular size of DOM rather than the molecular weight of DOM.Second, the influence of natural DOMs and metal ions on Naph and Phe sorption to BC was studied. It showed that the adsorption of Naph and Phe on BC were significantly inhibited by natural DOM, and decreased with increasing natural DOM loading. At the same loading, the reducing effects on adsorption of Naph and Phe were independent of the molecular weights of HA and FA.This result was inconsistent with the above findings about the model DOM’s. Compared to the single HA or FA loading, the loading of combined HA and metal ions (Fe(Ⅲ) or Al(Ⅲ)) may further attenuate the adsorption of Naph and Phe on BC. The decreasing effects on adsorption between two kinds of metal ions were with no significant differences.