Morphology and Structure of CaCO₃ Scale Layers Formed under Isothermal Flow Conditions

Abstract

The morphology and the growth pattern of calcium carbonate deposits formed on inner pipe surfaces, under turbulent flow, are studied. At temperatures below 30 °C, and for relatively high supersaturations, quite compact calcite layers are obtained, consisting of crystals growing nearly perpendicularly to the substrate surface in a columnar pattern. For small supersaturations (i.e., below a critical value S c ∼ 7), the deposition rate is drastically reduced and large isolated crystals are formed. At temperatures above 30 °C, rather weak dendritic aragonite patterns are dominant. The removal of magnesium from the tap water (used in the tests) results in the formation of all three polymorphs.

A study of CaCO3 scale formation and inhibition in RO and NF membrane processes

“…This value is reasonably close to the supersaturation level (pH 8.3 and S = 4.3) at which scaling is first observed in the flow of CaCO 3 supersaturated solutions in pipes, with the same water quality [10,23].…”

“…7c and d). The dominant phase in the deposits seems to be influenced by the solution pH, as already observed in pipe flow experiments [23].…”

Effect of water chemistry on calcium carbonate deposition on metal and polymer surfaces

“…5, are consistent with those reported in the literature [26,27]. The morphologies of CaCO 3 polymorphs observed in the present work are also similar to those found in other studies [6,22,[29][30][31][32][33]. Only calcite and vaterite crystals were found on Cu after exposure in the control test.…”

“…This result may indicate a lower scaling rate for Teflon, but given that the polymer has a low thermal conductivity, the formation of small amounts of calcium carbonate is not likely to have a dramatic effect on the thermal performance. Andritsos et al [22] compared scaling on stainless steel, copper and Teflon tubes, and found that the surface had little effect. However, the experimental conditions led to a diffusion-controlled mechanism in which the surface is not expected to impact the process.…”

Inorganic fouling control in reverse osmosis wastewater reclamation by purging carbon dioxide

“…6). Development of similar distinct rhombohedral structure of calcite crystals was reported in other studies (Andritsos et al 1997;Kitamura 2001). This phenomenon can be associated with the continuous precipitation and accumulation of sparing soluble salts on the membrane surface.…”