Kristianingrum, Susila, Endang Dwi Siswani, and Sulistyani Sulistyani. “MODIFICATION OF VOLCANIC ASH OF KELUD AS SELECTIVE ADSORBENT MATERIAL FOR Zn(II) AND Cr(VI) METAL IONS”. Jurnal Sains Dasar 7, no. 1 (April 15, 2018): 35–43. Accessed May 10, 2025. https://journal.uny.ac.id/index.php/jsd/article/view/22246.