Metal removal is also an important step in recycling silicon from sawing waste, as metal fragments, especially iron remaining in recovered Si or SiC, degrade the quality of Si or SiC. Tsai et al. [34,35] examined the feasibility of adopting the electrokinetic method to remove metal from sawing waste. Exactly how an applied electrical field and its duration affect metal removal effi- ciency was carefully studied. The optimal operational parameters were analyzed based on a cost model. Experiment results showed that application of an electrical field of 2.0 V/cm for 120 h reduced the residual iron percentage to 0.42 wt% in the slurry, and achieved an optimal total removal efficiency of over 92% and the local removal efficiency of iron of about 98%. The electrokinetic method clearly has the advantage of no use of additive chemicals, compared with the acid treatment proposed by Wang et al. [24].