Crystal growth and its inhibition related to industrial water systems.

Industrial cooling water systems face several challenges related to formation of sparingly soluble electrolytes. Utility plants, manufacturing facilities, air-conditioning systems are some applications that use "hot" processes for their operations. These processes have to be cooled. Water is the universal cooling medium because it is cost effective and has a high heat capacity. After cooling water comes in contact with the "hot" process, it needs to be re-cooled for reuse. This cooling is achieved by evaporation in the cooling tower. The end result is the concentration of all species found in the water until they reach a critical point of "scaling", leading to precipitation, and ultimately deposition of mineral salts. The species usually associated with these deposits (depending on the water chemistry) are calcium carbonate, calcium phosphate(s), silica/metal silicates etc.

Prevention of scale formation is greatly preferred by industrial water users to the more costly (and often potentially hazardous) chemical cleaning of the adhered scale, in the aftermath of a scaling event. Classic examples of scales that require laborious mechanical and potentially dangerous cleaning are silica and silicate salts. Phosphorous compounds, usually referred to as organic phosphates or phosphonates, are an integral part of a water treatment program. They function as scale inhibitors by adsorbing onto crystal surfaces of insoluble salts and prevent further crystal growth.

Our research program on chemical water treatment focuses on a number of topics. These, in summary, are:

• Chemical water treatment, prevention and inhibition of mineral scale deposits (such as SiO2, CaCO3, Ca3(PO4)2, CaSO4, MgSiO3); metal corrosion inhibition.
• Synthesis, characterization, selection and utilization of dispersant homo-, co-, and terpolymers; study of polymer/surface interactions.
• Precipitation and dissolution kinetics of sparingly soluble salts; organophosphorous chemistry; calcium coordination chemistry.
• Colloidal silica and silicates-containing composite materials. Mechanistic studies on formation and dissolution of colloidal silica. Effects of polymers on colloidal silica properties.
• Technology and technology transfer related to cooling water applications, operation of cooling towers, oilfield applications, water and wastewater purification and treatment.

Figure 1. Precipitation of CaCO3 in the presence of amino-tris-methylene-phosphonate and two different dispersant polymers.Dramatic differences in morphology are evident.

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