Gas absorption in slurries that contain fine particles is frequently encountered in a variety of situations in the chemical industry. Research on the modeling of these systems was first started almost 40 years ago by Professor Sharma's group and the pioneering first paper in the field originated from the Bombay UDCT. The enhancement in gas absorption was shown when the particle size is smaller than the film thickness for mass transfer. Many developments have occurred in this field since then, both on the modeling of such systems and application of the concept of the "micro-phase" enhancement to practical systems. It is the objective of this paper to take stock of these developments and provide a review on the modeling of these systems. The systems are classified into three main categories: (i) reacting particles, (ii) adsorbing particles, and (iii) catalytic particles. The modeling aspects of each class is discussed in detail and critically evaluated. Systems where the products form as a microphase are also discussed briefly.