Application of nickel hexacyanoferrate and manganese dioxide-polyacrylonitrile (NM–PAN) for the removal of Co²⁺, Sr²⁺ and Cs⁺ from radioactive wastewater

In this study, a nickel hexacyanoferrate and manganese dioxide-polyacrylonitrile (NM–PAN) composite was synthesized and used for the sorptive removal of Co²⁺, Sr²⁺, and Cs⁺ in radioactive laundry wastewater. Single-and multi-solute competitive sorptions onto NM–PAN were investigated. The Freundlich (Fr), Langmuir (Lang), Kargi–Ozmıhci (K–O), Koble–Corrigan (K–C), and Langmuir–Freundlich (Lang−Fr) models satisfactorily predicted all the single sorption data. The sorption isotherms were nonlinearly favorable (Freundlich coefficient, N_F = 0.385–0.426). Cs⁺ has the highest maximum sorption capacity (q_mL = 0.855 mmol g^–1) for NM−PAN compared to Co²⁺ and Sr²⁺, wherein the primary mechanism was the physical process (mainly ion-exchange). The competition between the metal ions in the binary and ternary systems reduced the respective sorption capacities. Binary and ternary sorption models, such as the ideal adsorbed solution theory (IAST) model coupled with single sorption models of IAST–Fr, IAST–K–O, IAST–K–C and IAST–Lang–Fr, were fitted to the experimental data; among these, the IAST–Freundlich model showed the most satisfactory prediction for the binary and ternary systems. The presence of cationic surfactants highly affected the sorption on NM−PAN due to the increase in distribution coefficients (K_d) of Co²⁺ and Cs⁺.