Insight into immobilization mechanisms of metal/metalloid ions and herbicide molecules on waste-derived Na-X zeolite covered with macromolecules

• High-carbon fly ash (HiC FA) was managed effectively through zeolite synthesis. • Immobilization potential of zeolite Na-X and its precursor was compared. • Na-X was a good adsorbent of metal cations (cadmium and copper ones). • Na-X modified with anionic polyacrylamide adsorbed Se(IV) more effeciently. • Herbicides were bound more strongly by Na-X after cationic polyacrylamide addition. Immobilization of toxic compounds on the solids limits their bioavailability in natural ecosystems. The use of waste-derived adsorbents for this purpose has additional benefit – the possibility of managing undesirable and dangerous by-products. Thus, the main aim of the study was to explore immobilization mechanism of metals (Cd, Cu), metalloids (As, Se), and herbicides (diuron, glyphosate) on zeolite Na-X free of ash residue, coming from waste solution after high carbon fly ash (HiC FA) conversion, under specific conditions – in multicomponent solutions as well as after solid modification with polymers. Immobilization strength was assessed based on adsorption/desorption studies, whereas the solid surface was investigated by XPS, FTIR, SEM-EDS, etc. The results obtained for Na-X was compared with those measured for its precursor, HiC FA. It was found that Na-X was a good adsorbent of Cu(II) and Cd(II) cations – it bound 195.8 mg/g (58.7 %) of Cd(II) and 126.9 mg/g (38.1 %) of Cu(II) mainly in the form of hydroxides. The Na-X modification with polymers made its adsorption capacity towards metalloid anions and herbicides higher. Anionic polyacrylamide increased the Se(IV) adsorption from 0.2 to 67.5 mg/g. Cationic polyacrylamide contributed to higher immobilization of glyphosate and diuron by 43.9 % and 46.4 %, respectively.