John M. Coulson and John F. Richardson co-wrote a textbook on chemical engineering first published in 1954, which developed into an established series of six text books known as Coulson & Richardson's Chemical Engineering book series. They were largely responsible for the contents of the first two volumes while they were editors for the rest of the series of six volumes. Richardson continued editing the series after the death of Coulson in 1990. In order to keep the popular book series updated after the death of Richardson in 2011, Elsevier Limited has selected several eminent educators to edit/update contents of the book series. Dr. Ajay K Ray has been selected to serve as the Volume Editor for the sixth edition of Coulson and Richardson Chemical Engineering Volume 2B: Separation Processes. Dr. Ray is responsible for modifications, additions and editing of 13 chapters of the volume 2B of the book series.