Experimental study of ammonia removal from water by membrane distillation (MD): The comparison of three configurations

This study tries to compare the separation performance of three kinds of membrane distillation (VMD, DCMD and SGMD) used in the removal of ammonia from water in terms of mass transfer coefficient (Ka) and selectivity (β). For all three MD configurations, equations to determine their Ka and β values from experimentally obtained results were derived. Experiments of three MD configurations were conducted, respectively, to measure the ammonia concentration and transmembrane flux. So, on the ground of derived equations, Ka and β were evaluated. It was found that, in comparison of three MD configurations with each other under similar operation conditions, VMD shows the highest Ka but the lowest β, DCMD gives the highest β and moderate Ka, and SGMD has the moderate β and lowest Ka. Factors that may affect the separation processes, such as the membrane characteristics, the feed temperature, the feed and permeate velocity, and the initial concentration and PH of the feed were also experimentally examined.