Preparation and Properties of Ag-CRG as Water Treatment Agent
GAO Hua-sheng1, JIN Yi-zhong1, TAN Tian-en1, ZHU Qi-hua2 (1. Department of Environmental Engineering, Zhejiang University, Hangzhou 310027, China; 2. DEAN Group, Ningbo 315040, China)
Controlled-Release Glass (CRG), which is a kind of erosion-controlled release systems, is an ideal carrier to realize 0-order release of inorganic ions. Phosphate CRG specimens containing Ag2O (Ag-CRG) and AgNO3 solutions of different concentration levels were prepared. The spread-plate test and rotating coupon test were conducted to investigate the antibacterial and corrosion behaviors of silver ions and the properties of Ag-CRG in aqueous environment. The tests with the AgNO3 solutions showed that silver ions had satisfactory and persistent bacteriostatic effect when its concentration was over its Minimum Effective Dosage (MED) level of 5×10-3 mgL-1 and that the galvanic corrosion of carbon steel was aggravated when the dosage of Ag+ was increased. But addition of 5 mgL-1 polyphosphate could effectively eliminate the unfavorable effect of Ag+ at its MED level. Further bacteriostatic and corrosion tests showed that when the Ag-CRG specimens were used, the fresh polyphosphates and silver ions were released congruently and continuously to yield the combined corrosion inhibition as well as antibacterial effects as the Ag-CRG specimens dissolved constantly in water. This study concluded that the Ag-CRG could find application as a multi-purpose agent with reduced administration in the treatment of cooling water, and drinking water systems.