Investigation of scaling mechanism on reverse osmosis membranes using «fluorescent» antiscalant

Abstract

Scaling of sparingly soluble salts could be recognized as a main factor that limits wide application of reverse osmosis (RO) membrane facilities in drinking water production and industrial water recycling. The report demonstrates a new approach to evaluate scaling rates and antiscalant behavior in commercial membrane spiral wound modules through the use of the fluorescence-tagged antiscalants and laser scanning confocal microscope (LSM) observations. Throughout the conducted study the “visualization” of scale inhibitors behavior appeared to be a very promising and universal tool for their activity understanding. Examination of membrane surface and calcite crystals in autopsied membrane modules demonstrated new unexpected results: antiscalant adsorbed either on membrane surface or on crystal surface. In the presence of calcium ions during ground water treatment antiscalant was adsorbed only on crystal surface and sorption on membrane was not detected. Fluorescence was more intensive on the surface and on the outer edges of crystal surface than inside crystal. To investigate antiscalant adsorption to membrane surface, experiments with distilled water containing antiscalant were performed. Intensive sorption of fluorescent inhibitor molecules to membrane was observed.