Influence of clay suspensions on scaling

Scaling problems have been intensively investigated using carbonically pure water (i.e. synthetic water containing only calcium and carbonates ions) or natural water which only contain few particle suspensions. Nervertheless, industrial water can contain a lot of materials in suspension, especially when the water is taken from rivers. Thus, the objective of the present study is to characterise the interactions between clays in suspension and scaling phenomenon.In order to estimate the effect of clays in suspension, we first performed Rapid Controlled Precipitation assays (RCP). This method can evaluate the effect of an addition of clay in suspension on the CaCO3nucleation-growth kinetics in calcifying water. In this way we found that, whichever clay used, process kinetics always slowed down.Secondly, gravimetric scaling experiments on polyethylene were achieved. Now, results are much more contrasting. It appears that some clay like smectite leads to a high slowdown of scaling. In addition, calcium carbonate weakly deposits while clay deposits a littie. With other clay like kaolinite or granitic clay, the deposit consists of CaCO3with clay.Finally, some clay does not deposit on polyethylene at all and has almost no inhibition effect on scaling (case of a natural clay)We noticed that the antiscaling effect of clays is maximum if the clay displays the maximum quantity of suspended materials as well as a highly negative potential ζ.We should précise that if the nucleation-growth phenomenon is slowed down by clay suspensions, the deposit quantity obtained is not always minimised. This is due to the fact that some clays can also deposit themselves.