Research on The Removal of Scale Ions from Circulating Cooling Wastewater by Chemical Coagulation Process

¹ Harbin Institute of Technology, Shenzhen Graduated School, Shenzhen 518055, China.
² China Coal Research Institute, Beijing, China, 100013

^* Corresponding author: du@cct.org.cn

Abstract

In this paper, the circulating cooling wastewater was treated by chemical coagulation process through adding NaOH/Na₂CO₃.The effect of NaOH and Na₂CO₃ dose on removal of scale ions, such as Ca²⁺, Mg²⁺, Ba²⁺, Sr²⁺, SiO₂, was studied and the removal mechanism was discussed. The results showed that the increase of NaOH dose was beneficial to the removal of above-mentioned scale ions. When NaOH was only added, the removal efficiency of Ca²⁺, Mg²⁺, Ba²⁺, Sr²⁺, SiO2 was 86.3%, 91.6%, 86.5%, 58.1%, 84.2%, respectively. When 680 mg/L of NaOH and 300 mg/L of Na2CO3 were added, and the effluent pH was above 11.2, the removal efficiency of Ca²⁺, Mg²⁺ was 95.8% and 89.4%, respectively, and the concentration of Ca2+and Mg2+ was below 20 mg/L, which met the target of wastewater treatment. Finally the possible removal mechanism of Ca²⁺, Mg²⁺, Ba²⁺, Sr²⁺and SiO₂ was discussed.