In this paper, the problem of distributed neutralization of toxic 2D diffusion process is discussed. The diffusion process is modelled by a parabolic PDE system. A group of mobile robots which can release neutralizing chemicals are sent to detoxify the pollution. We attempt to solve the optimal actuator location problem by using Centroidal Voronoi Tessellations. A new simulation platform (DiffMAS2D) for measurement scheduling and controls in distributed parameter systems is also introduced in this paper. Simulation results show the effectiveness of our proposed method.