Adsorption of Cu(II) from aqueous solution by modified magnetic starch st/Fe3O4-g-pAA

The composite particles (St/Fe3O4) were prepared using the co-precipitation method, whereby FeSO4 and FeCl3 were precipitated under alkaline conditions. The particles were composed of a starch matrix and Fe3O4. Subsequently, AA was grafted and cross-linked onto the composite particles (St/Fe3O4) via a one-step traditional free radical polymerization method, resulting in the formation of polymer-modified composite particles (St/Fe3O4-g-pAA). The initiator used in this process was 2,2'-Azobis(2-methylpropionitrile). The structures of St/Fe3O4 and St/Fe3O4-g-pAA were characterized by FTIR, thermogravimetric analysis and hysteresis loop. The impact of varying parameters, including the dosage of the St/Fe3O4 and St/Fe3O4-g-pAA adsorbents, the initial pH value of the Cu(II) solution, the initial Cu(II) concentration, the absorption time, and the temperature, on the adsorption behavior of Cu(II) was investigated. The results demonstrated that St/Fe3O4-g-pAA exhibited excellent adsorption performance for Cu(II), with a unit adsorption capacity of 123.92 mg/g and a maximum removal rate of 85% when the original concentration of the Cu(II) solution was 10. The experiment was conducted with 24 mg/L of Cu(II) at a pH of 7 at room temperature, with a mass of 1.5 mg of St/Fe3O4-g-pAA and an adsorption time of 3 h. The adsorption process followed the Langmuir model and the pseudo-second-order kinetic model, which was dominated by chemical adsorption and belonged to single-layer adsorption. The results of the renewable performance studies demonstrated that following eight cycles of adsorption, 92% of the initial adsorption effect was retained. It can therefore be concluded that the St/Fe3O4-g-pAA adsorbent material prepared in this work is an effective means of improving the adsorption rate of Cu(II).