Arsenic is a toxic and carcinogenic element; pollution of natural waters with arsenic is a global problem. Inorganic As (III) compounds are known to be more toxic than inorganic As (V) compounds. Purification of water from As (III) and As (V) using adsorption materials based on clay minerals is of increasing interest today. In this study, we investigated the possibility of purifying aqueous solutions from As (III) and As (V) using composite sorbents created by modifying montmorillonite. Montmorillonite modified with Fe3O4 nanoparticles and a cationic surfactant, showed a better degree of extraction of As (III) and As (V) from aqueous solutions compared to other modifications. The extraction rate of As(III) and As(V) by montmorillonite modified with Fe3O4 nanoparticles and a cationic surfactant did not depend on the pH of the solution and was higher than 95%. Optimal conditions for the extraction of As (III) and As (V) from aqueous solutions have been established using montmorillonite modified with Fe3O4 nanoparticles and a cationic surfactant. It has been shown that in the presence of Fe(III) ions, the degree of extraction of As(III) and As(V) by montmorillonite modified Fe3O4 nanoparticles and a cationic surfactant, decreased to 69%. Cr(III) possess the highest influence on the degree of extraction of As (III) and As (V): the degree of recovery of As (III) and As (V) using montmorillonite modified with Fe3O4 nanoparticles and a cationic surfactant, in its presence decreases and amounts to 40 and 25%, respectively. Together with As (III) and As (V), Cu (II) was almost completely removed from the solution. Adsorption process of As(III) and As(V) on montmorillonite modified with Fe3O4 nanoparticles and a cationic surfactant is best described by the Langmuir model. The sorption capacity of modified montmorillonite for As (III) and As (V) was 9.9 mg/g and 7.6 mg/g, respectively.