Aqueous two-phase systems (ATPS) are a substitute for conventional liquid-liquid extraction systems and, are usually composed of a salt solution and the polymer polyethylene glycol (PEG). Polyvinylpyrrolidone (PVP) is an alternative polymer, inexpensive, stable, and it has great potential for ATPS. This study aimed to investigate the effect of the molecular weight of the polymer (10 000 and 40 000) and the temperature (298.15, 318.15 and 338.15 K) in the system composed of PVP10 or PVP40 + manganese sulfate + water. The Merchuk equation has been used to correlate the experimental binodal data. For all systems, the higher the temperature, the higher the two-phase region and the slope of the tie-line. The increase in the molecular weight of the polymer resulted in the expansion of the twophase region. Furthermore, the UNIQUAC model was used to fit the experimental LLE data. (C) 2018 Elsevier B.V. All rights reserved.