The extraction efficiency of dysprosium was calculated using different methods.

Extraction time h−1	Concentration of Dy(iii) × 10−4/mol cm−3	Mass of Dy on the Cu electrode/g	Extraction efficiency/%
			ICP-AES	Mass of Dy on the Cu electrode
0	1.340	0	0	0
3	0.805	0.4218	39.9	38.7
8	0.114	0.9341	91.5	85.8
12	0.013	1.0134	99.0	93.1
16	0.011	1.0139	99.2	93.1