Analysis of constant-current electro-osmotic dewatering

An analytical solution of the basic differential equation for a constant-current electro-osmotic dewatering is presented by assuming that both a modified consolidation coefficient C-e and an electro-osmotic pressure gradient E-pg are constant. Bentonite was used as an experimental material. Electro-osmotic dewatering of homogeneous bentonite cake was conducted under a constant electric current density i of 0.125-4 A/m(2). C-e and E-pg, both obtained by a fitting method, increase with increasing i. The final moisture distribution of the material can be explained well by the present theory. The progress of electro-osmotic dewatering can be represented by the average consolidation ratio U-c as in a mechanical expression. The agreement between calculated and experimental U-c under the condition i < 1 A/m(2) is satisfactory. The coincidence between theory and experiment for i > 1 A/m(2) is good for the first half of the dewatering process but rather poor for the second half of the process, since the creep deformation of the material is not considered in the basic differential equation.