Surface waters organic acids

Donors of appropriate redox potential to react with holes at the anatase surface include organic acids, carbohydrates, fats, CN, and halides 2 ). (The cyanide reaction has been studied for its utility in treatment of the waste streams from Hold mininK operations in the Canadian Northwest Territories.) More immediately releyant to natural water is the observation that an anatase slurry could effect the decoloration of a chlorinated bleach plant effluent. A sample of amber colour, pH = 1.8, and low residual chlorine was irradiated in the presence of 0.5% (wt) anatase with li((ht of 350 nm for periods up to 18 hr. The optical absorbance decreased by half in 1080 min. Small amounts of chloride and formaldehyde were detected ( ). This reaction may provide a precedent for observation of a relation between photobleachinK of humics in water and metal ions. If so, we are brouj ht to the question of the reactivity of colloidal iron oxides. 

Condensed-phase chemistry is another possible source of aerosol surfactants. The oxidation of aerosol organic material yields functionalized products which may be surface-active [98]. Oxidative processing of water-soluble species in cloud or aerosol water may result in the formation of surface-active organic acids such as malonic and malic acids [99,100]. Surface-active HULIS or organosulfate species may also form in situ in aerosol or cloud water [84, 85, 101-104]. 

Gas turbine fuels can contain natural surfactants if the cmde fraction is high in organic acids, eg, naphthenic (cycloparaffinic) acids of 200—400 mol wt. These acids readily form salts that are water-soluble and surface-active. Older treating processes for sulfur removal can leave sulfonate residues which are even more powerful surfactants. Refineries have installed processes for surfactant removal. Clay beds to adsorb these trace materials are widely used, and salt towers to reduce water levels also remove water-soluble surfactants. In the field, clay filters designed as cartridges mounted in vertical vessels are also used extensively to remove surfactants picked up in fuel pipelines, in contaminated tankers, or in barges. 

Solution porosity refers to voids formed by the solution of the more soluble portions of the rock in the presence of subsurface migrating (or surface percolating) waters containing carbonic and other organic acids. Solution porosity is also called vugularporosity where individual holes are called vugs. 

Upland surface water. This is low in hardness salts having run over impervious rocks but will often be high in organic matter, i.e. fulvic and humic acids. 

Four species of antimony have been identified in natural waters Sb(III), Sb(V), monomethylstibonic acid, and dimethylstibinic acid (the latter two are due to microbial activity)(De La Calle-Guntinas et al. 1995). In view of the high toxicity of antimony, a very low maximal admissible level of Sb in drinking water is imposed (the EC maximum admissible level of Sb in drinking and surface water is 10 xg/L). As Sb(III) is more toxic than Sb(V) and inorganic species are more toxic than organic ones, a distinction between the different species becomes mandatory. 

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