Optimization of nickel removal from aqueous solutions by physical-modified biochar

Nowadays, the use of biochar as a new and suitable adsorbent to remove inorganic pollutants from water sources has grown significantly. The present study was conducted to evaluate the effects of biochar physical modifications compared to unmodified biochar on nickel (Ni) removal efficiency in aqueous solutions.

After the production of cypress cones biochar (RB), biochar particles (<164 µm) were crushed into very small (<26 µm) dimensions (BMB) using a planetary ball mill and after evaluation their various properties by SLS, BET, FTIR and SEM techniques, their application (RB and BMB) in optimizing the Ni removal from aqueous solutions were evaluated using the response surface methodology (RSM: Box-Behnken design).

Based on the results, the physical modification of biochar (BMB) decreased the particle size by 6.2 times, increased the specific surface area by 4.9 times, increased (containing oxygen) and decreased (aliphatic and OH stretching groups) of specific functional groups and finer surface morphology, compared to RB. The use of BMB in the aqueous solution caused an increase of 9.7% (on average) in the removal of Ni compared to the RB sample. The fitting of the data obtained from Ni removal in the Box-Benken model in both adsorbents shows the appropriate prediction of this model in the optimization of Ni removal from aqueous solutions.

According to the results of this research, the physical modification of biochar, as a simple, cheap, and environmentally friendly method, due to the increase in the efficiency of Ni pollutant removal, can be introduced as a suitable method in the activation of biochar, which further research is required based on the type of biochar and various pollutants.