Reagentless reduction of hydrogen carbonate-calcium hardness of water: equilibrium states and kinetics

Abstract

The equilibrium states and kinetics of changes in the concentrations of carbonate system components in water with different calcium hardness are analyzed and the possibility of reducing this indicator by an environmentally friendly method, aeration, is evaluated. Changes in the concentrations of dissolved carbon dioxide, calcium ions, hydrogen ions (pH), bicarbonate and carbonate ions in water depending on the partial pressure of carbon dioxide in soil and atmospheric air and the kinetics of reducing the bicarbonate-calcium hardness of water during its natural and forced aeration were traced. It is shown that water purification by a stream of atmospheric air microbubbles with an average radius of 50 m and a flow rate of 10 l/min can reduce the hydrogen carbonate-calcium hardness from 8 mg-eq/l to 1 mg-eq/l in 100 liters of water in 20 minutes. In the paradigm of "green chemistry", this method is more rational, environmentally friendly, and economical than ion exchange or reverse osmosis, which are currently practiced to reduce hardness in decentralized water supply systems.