This book serves as an introduction on mass transfer models in membrane processes, with a special focus on their applications in Artificial Organs. Various such models are discussed while multiple easy to use module equations are presented, enabling readers to gain basic knowledge of the mass flow of toxins across membranes. This is particularly interesting to membrane manufacturers who may use these equations to improve the relation of module performances and production costs. Additionally, examples which specialize on artificial organs, but in principle can be applied to analogous environmental, food and biotechnology processes- are analysed. This book will appeal to readers who want to understand how membrane modules and processes can be optimized and will be a great tool for graduates, researchers and professionals working in this field.