Static inhibition test was performed as described in Standard Test Method (GB/T
16632-2008, China) by EDTA titration according to following steps. First, 25 ml of
0.5 g l-1 scale inhibitor solution was dropped into 100 ml of 5 mmol l-1 CaCl2
solution in a 250-ml volumetric flask, followed by adding 5 ml borate buffer
solution (0.01 mol l-1
, pH = 9) and 7.5 ml of 0.1 mol l-1 NaHCO3 solution to the
flask. The mixture solution was diluted to 250 ml with distilled water and stirred to
ensure complete mixing, then, transferred into an Erlenmeyer flask and immerged
into water bath at 80 C for 10 h. In addition, a blank experiment without scale
inhibitor added was made as a reference. The scale inhibition efficiency (g) was
calculated using the following equation: