Fathurrahman, M., Taufiq, A., Widiastuti, D. and Hidayat, F. (2020) “(RETRACTED) Synthesis and Characterization of Silica Gel from Corncob Ash As Adsorbent of Cu(II) Metal Ion”, Jurnal Kartika Kimia, 3(2), pp. 89-95. doi: 10.26874/jkk.v3i2.66.