Estimation of colloidal deposition from heterogeneous populations.

This paper reports a study of size-heterogeneous colloid filtration in a new bed using different types of colloids under different conditions of flow and solution chemistry. Depth-wise variation of the particle-size-distributions f(i)(x), and the total liquid-phase colloid concentration, C(x) are measured which are used to estimate the depth-wise variation of the liquid-phase concentration for each distinct section of the heterogeneous population, C(i)(x). It is observed that log C(i)(x) is linear with depth, for some systems, while it shows deviation from linearity, with the slope decreasing with depth, for others. Deposition-rates for these distinct sections of the heterogeneous population, k(i), are estimated from the slopes of the log C(i)(x) data. These deposition-rates were then compared with predicted homogeneous-population deposition-rates from Colloid Filtration Theory (CFT), which shows agreement between the CFT-based-deposition-rates and heterogeneous-population-data based deposition-rates, for low flow velocities. At higher flow velocities a gap between the CFT-based and Data-based deposition-rates is observed. Deposition-rates from CFT are then used in a heterogeneous-colloid-filtration model, to examine if heterogeneous colloid deposition can be expressed as the sum of its parts. It is observed that, the sum-of-parts model provides a reasonable estimate of colloidal deposition from heterogeneous populations. Based on these results, it is possible to make predictions of colloidal deposition from complex heterogeneous suspensions. A new method for studying heterogeneous colloid filtration is also proposed.