Study of the Process of Sorption of Iron and Copper from Sulfuric Acid in Their Joint Presence by Natural Zeolite

The most promising method for the purification of concentrated technical sulfuric acid is the purification sorption method, which is the most effective and innovative, using a natural sorbent. Study of the process of sorption of iron and copper cations from concentrated technical sulfuric acid by a natural zeolite. The specific surface area of the zeolite isolated from reactive sulfuric acid is 4.781 m2/g. The true absorption volume in the zeolite after the purification of sulfuric acid decreases to a value of 147.0068 mL/g for a zeolite sample. The adsorption pore volume for the zeolite after the acid purification calculated from the obtained results is 0.229 mL/g. The physicochemical methods of analysis (NGR, IR, X-ray diffraction, DTA, porosimetry, electron microscopy) and chemical methods revealed that in concentrated sulfuric acid the Fe–O bonds of octahedrons and SiO bonds of tetrahedrons of the zeolite framework are stable. The sorption process was carried out under conditions of a room temperature of T = 25 °C, the ratio “zeolite: H2SO4” of 10:100, and a process time of 5–50 min. The specified concentration of the Fe and Cu cations was created by introducing the calculated amount of FeSO4·7H2O and CuSO4·5H2O, in order to identify the patterns of the sorption process of copper and iron in their joint presence (CFe > CCu; CFe = CCu). The regularities of sorption of iron and copper cations by zeolite in their joint presence on the model system “H2SO4–zeolite–Fe–Cu” were studied and selective sorption capacity of zeolite with respect to iron cations was revealed. The maximum degree of sorption of iron cations in concentrated sulfuric acid is achieved in 10–15 min and makes up 95% and that of copper 30.6%. The process of iron sorption from sulfuric acid occurs according to the types of ion isomorphism and ion exchange, as indicated by a very high number of sorbed Fe ions and the absence of their release (desorption) from the zeolite into the solution. The Cu cations are sorbed by zeolite from acid by the ion exchange method, which is confirmed by the physicochemical analysis methods.