The column consisted of four stages with stainless steel wire mesh screens

Abstract Ion exchange (IE) processes have been used extensively for the complete demineralization of water for use in boilers, over the last three or four decades where radical developments have rendered IE competitive in some circumstances with other desalination processes for the treatment of brackish water. Unlike many desalination processes fixed bed IE plants can be operated in either small or large units. Desalination by IE is effected commercially using fixed beds of ion exchange resins (IERs).
Usually a cation exchange resin bed column followed by an anion exchange resin bed column are used in series until the resins are exhausted after which they are separately regenerated. In the present work desalination in a multistage fluidization column was investigated rather than the traditional fixed bed columns. The column consisted of four stages with stainless steel wire mesh screens, onto which a bed of resin was placed. The solution was made to circulate through the column in a closed loop process at different flow rates by which the resin beads become fluidized. Four factors were investigated for their effect on the percent extraction of NaCl from a saline solution and these were: initial solution concentration, resin bed height, type of resin bed (mixed or alternate cation/anion IERs), and solution flow rate.
The results indicated that maximum extraction achieved under the optimum conditions was 76%, rendering the produced water suitable for irrigation purposes. It was also found that larger bed heights and complete fluidization promoted more rapid mass transfer and desalination. The computed results indicated that overall mass transfer coefficients were constant with initial concentration, linear with solution flow rate up till a certain value above which they decrease, and are almost exponential with resin bed height.