Lake-organics, complexation copper

Complexation of Cu at Varying pH. In order to compare the effects of complexation by lake organics at different pH s, the fraction (a) of total dissolved copper (Cu ) was... 

From the results, in Figure 4, one can see that until about pH 9, organics are much more important in complexing copper than are carbonate and hydroxyl ion. At a lower pH of 6, and with organics with a stability constant as found in Lake Ontario, 90% of the copper present is complexed by 10 M organics, whereas at a pH of 8, 99.9% of the copper is complexed. 

Although there are many techniques used to clean such objects, commercial products are often simple solutions of ammonia within a hydrogen-based solvent, with the additional inclusion of a very fine and mild abrasive called diatomaceous earth (DE). DE is nearly pure silica, in the form of SiO2, with a very porous characteristic. DE consists of the skeletons of small aquatic unicellular algal organisms called diatoms, which have survived evolutionary processes for approximately 100 million years. Placed in the taxonomic family Bacillariophyceae, the cell walls of these creatures are made of silica. Because silica is more dense than seawater or freshwater, the presence of silica tends to cause diatoms to sink into the water depths. As such, DE is collected from the bottom of ancient lake beds and is currently mined and used for many commercial and industrial purposes. Thus, within metal cleaners, DE acts as an abrasive, and the alkaline ammonia dissolves any greasy residue on the metalware. In addition, the ammonia reacts with the CuO or CuS to form the soluble ammonia complex of copper, which is Cu(NH3)42+. The greasy tarnish residue can then be washed away with clean water and a damp cloth. 

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