Development and Evaluation of Solbrax-Water Nanoemulsions for Removal of Oil from Sand

Table 2

Experimental matrix for each combination of levels of the washing process of the contaminated sand and their respective efficiencies.

Systems	Time (h)	Speed (cycles·min^−1)	Temperature (K)	𝑋1^a	𝑋2^a	𝑋3^a	𝐸^b (%)
1	1	120	298	−1	−1	−1	17.33
2	1	120	318	−1	−1	1	39.13
3	1	240	298	−1	1	−1	26.65
4	1	240	318	−1	1	1	68.03
5	4	120	298	1	−1	−1	21.19
6	4	120	318	1	−1	1	83.29
7	4	240	298	1	1	−1	33.99
8	4	240	318	1	1	1	95.78
9	2.5	180	308	0	0	0	21.63
10	2.5	180	308	0	0	0	22.20
11	2.5	180	308	0	0	0	19.95
12	2.5	180	308	0	0	0	19.44
13	2.5	180	308	0	0	0	21.64

aRepresentation of minimum, maximum and center points run. ^bEfficiency calculated by the ratio of initial and final oil concentrations.