Reducing the concentration of Ca2+ Ions in Water Using Ultra- and Nanofiltration Ceramic Membranes

Abstract

The main regularities of processes of water purification from Ca²⁺ ions using ultra- and nanofiltration ceramic membranes, in particular, the influence of the operating pressure, the duration of the experiments, the concentrations of Ca²⁺ ions in the original solution and its temperature to reduce the content of these ions in the filtrate were identified. The cleaning process of the model solution CaCl₂ was carried out on an experimental installation of baromembranes using ultra-and nanofiltration tubular membranes of ceramic oxide (produced in Germany). By the experimental results characteristics of ceramic membranes: retention coefficient R (%) of ions Ca²⁺ and specific productivity Jv (m³/(m²×h) of membrane were calculated. It has been established that on these results the processes of water purification from Ca²⁺ ions ultra- and nanofiltration ceramic membranes is advantageously carried out at a pressure of respectively 0,6 and 1,0 MPa. It was studied that for such membranes with increasing concentrations of Ca²⁺ accordingly to 90,0 and 120,0 mg/dm³ retention coefficient of these ions was reduced to 22,2 and to 83,33 %. And specific productivity membranes remained almost unchanged. Lowering the temperature of the feed solution CaCl₂ resulted in a decrease in the specific productivity of the membrane, which is associated with a decrease in solution viscosity and without affecting the degree of its purification from Ca²⁺. It was concluded that studies have shown the high efficiency of water purification from Ca²⁺ using ceramic nanofiltration membranes compared with ultrafiltration. On the basis of obtained results, use of ceramic nanofiltration membranes in the first stage water softening, for example, prior to ion exchange to ensure boilers CHP, heating systems and boilers feeding was suggested.