© The Author(s) 2013. Published by Science and Education Publishing. Table 2. Four factor five level central composite design for preparing synthetic sample Experiment Number A B C D 1 70 7 0.75 45 2 130 3 11 4 5 2.25 6 8 9 75 10 12 13 14 15 16 17 40 1.5 60 18 160 19 100 20 21 22 23 30 24 90 25 Ravi Shankar et al. Removal of Lignin from Wastewater through Electro-Coagulation. World Journal of Environmental Engineering, 2013, Vol. 1, No. 2, 16-20. doi:10.12691/wjee-1-2-1 © The Author(s) 2013. Published by Science and Education Publishing.