3.3. Effect of adsorbent dosage on Ni(II) and Co(II) removal
Adsorbent dose is a significant factor to be considered for effective removal as it determined sorbent–sorbate equilibrium of the system [4]. In order to investigate the effect of the amount of bio-char on Ni(II) and Co(II) adsorption, adsorbent dosage in the range of 1–10 g/L was used for the adsorption experiments and the results are given in Fig. 3 for adsorption (%) and the biosorption amount (mg/g). The adsorption amount decreases with an increase in adsorbent dosage. On the other hand, the percentage of the adsorption increased first with an increasing amount of adsorbent and reached saturation. The initial increase in the percentage of adsorption can be attributed to increased biosorbent surface area and the availability of more adsorption sites. The decrease in the adsorption amount may be attributed to overlapping or aggregation of adsorption sites resulting in decrease in total adsorbent surface area. According to the results for further batch equilibrium adsorption experiments 7 g/L adsorbent dose was selected for Ni(II) and 4 g/L adsorbent dose was selected for Co(II) taking into consideration of the qe value.