Study of heteronuclear complexation in Fe(II)-Fe(III)-Mn(II)-CH3COOH-H2O system Mairambu Zhorobekova, Altynai Mametova and Farida Miraminzoda E3S Web of Conf., 401 (2023) 04064 Published online: 11 July 2023 DOI: 10.1051/e3sconf/202340104064