Thermosolutal natural convection heat and mass transfer in a 2D square cavity are studied numerically in the presence of Soret effect and uniform volumetric heat generation. A hybrid scheme with simple relaxation time lattice Boltzmann method (SRT-LBM) is used to obtain the velocity field while the temperature and concentration fields are deduced from energy and species balances using a finite difference method (FDM). The study focuses on the effect of three parameters, which are the Soret parameter (Sr = -0.5, 0, and 0.5), the buoyancy ratio (N = -1 and 1), and the internal to external Rayleigh numbers ratio (0 <= R <= 80). Combined effects of these parameters on fluid flow and heat and mass transfer characteristics are examined for Lewis number Le = 2, Prandtl number Pr = 0.71, and external Rayleigh number Ra-E = 10(5). The interaction between the heat generation and the thermodiffusion may play an important role in purifying/charging the confined fluid from/with species by considering positive/negative values of Sr.