Removal of calcium and magnesium ions from hard water using modified Amorphophallus campanulatus skin as a low cost adsorbentAjeng Yulianti Dwi Lestari, Abdul Malik, Sukirman, Muhammad Irfan Ilmi and Mahathir SidiqMATEC Web Conf., 154 (2018) 01020DOI: https://doi.org/10.1051/matecconf/201815401020