In the monocomponent retention test, various dosages of NCC were added into the furnish under the agitation speed of 750 rpm. 30 s later, the filtrate was collected and the time for the first 100 ml of filtrate was recorded to calculate the drainage rate according to the formula as follow,
100
Drainage rate (ml/s) = time
Light transmittance was measured at the wavelength of 500 nm using a Hitachi UV 4100 spectrophotometer (Hitachi, Japan). The concentration of filtrate was calculated according to the curve of light transmittance against filtrate concentration, and the first pass