4. Effect of Sorbent Particle Size The effect of sorbent particle size on biosorption of dyes is shown in Fig. 3. The dyes adsorbed increased as the sorbent particle size decreased. It was suggested that the increase in sorption depended on the large external surface area for small particles; this removes more dye in the initial stages of the sorption process than the large particles. This criteria was considered vital in choosing the ideal particle size as 125-250 mì, furthermore smaller particles than this tend to clog the column during industrial applications.