An apparatus suitable for a continuous fluidized ion exchange bed system comprising: a first column suitable for housing a first fluidized bed, said first column comprising a first particle-feeding means to feed ion exchange or adsorbent particles into an upper region of said first column and a first fluid-feeding means to feed a first ion-containing fluid into a lower region of said first column to form a fluidized bed in the first column, said first column further comprising a first fluid outlet in the upper region at a height above the first particle-feeding means, said lower region being remote from said upper region such that said solids and said fluid flow continuously counter-currently in the first fluidized bed, wherein the upper region comprises a first end of the first column and the lower region comprises a second end of the first column; a second column suitable for housing a second fluidized bed, a second particle-feeding means located at a point above the mid-region of the second column to feed particles into an upper end of said second column and a second fluid-feeding means to feed a second ion-eluting fluid into a lower end of said second column to form a second fluidized bed in the second column, a second fluid outlet at the upper end of the second column at a height above the second fluid-feeding means, said upper and lower ends being remote such that said particles and said fluid flow continuously counter-currently through said second column; a first means connecting the first and second fluidized beds such that the second end of said first column is connected to the upper end of said second column, wherein the first column is situated at a height above at least a portion of the second column, said first connecting means being adapted to permit passage of particles and prevent passage of said first fluid into said second column; a second means connecting the lower end of said second column to a transport section, said second connecting means being adapted to permit passage of particles and prevent passage of said second fluid; and a transport section which connects to the upper region of the first column, said transport section comprising means to hydraulically move said particles upwardly into a liquid-solids separator to separate the particles from fluid prior to entry into the first column via the first particle-feeding means. a first column suitable for housing a first fluidized bed, said first column comprising a first particle-feeding means to feed ion exchange or adsorbent particles into an upper region of said first column and a first fluid-feeding means to feed a first ion-containing fluid into a lower region of said first column to form a fluidized bed in the first column, said first column further comprising a first fluid outlet in the upper region at a height above the first particle-feeding means, said lower region being remote from said upper region such that said solids and said fluid flow continuously counter-currently in the first fluidized bed, wherein the upper region comprises a first end of the first column and the lower region comprises a second end of the first column; a second column suitable for housing a second fluidized bed, a second particle-feeding means located at a point above the mid-region of the second column to feed particles into an upper end of said second column and a second fluid-feeding means to feed a second ion-eluting fluid into a lower end of said second column to form a second fluidized bed in the second column, a second fluid outlet at the upper end of the second column at a height above the second fluid-feeding means, said upper and lower ends being remote such that said particles and said fluid flow continuously counter-currently through said second column; a first means connecting the first and second fluidized beds such that the second end of said first column is connected to the upper end of said second column, wherein the first column is situated at a height above at least a portion of the second column, said first connecting means being adapted to permit passage of particles and prevent passage of said first fluid into said second column; a second means connecting the lower end of said second column to a transport section, said second connecting means being adapted to permit passage of particles and prevent passage of said second fluid; and a transport section which connects to the upper region of the first column, said transport section comprising means to hydraulically move said particles upwardly into a liquid-solids separator to separate the particles from fluid prior to entry into the first column via the first particle-feeding means.