Eco-friendly preparation of biochar nanomaterials from waste walnut shell and their adsorption application

The modified biochar nanomaterials were prepared by a simple polymerization and calcination method using spent walnut shell as raw material. And the prepared samples were characterized by means of various techniques. The influence of different adsorption materials, solution concentration and operation temperature on the adsorption efficiency of adsorbent to methylene blue in water were investigated. The results show that the prepared biochar sample C-1 had the highest BET surface area of 418.1 m 2 /g and the best adsorption efficiency of 97.61% at room temperature. And that the adsorption efficiency of the adsorbent was still remained 59.21% after 4 times of regeneration cycles. Furthermore, the adsorption process were further analyzed through adsorption kinetics and thermodynamic models. The results indicate that the adsorption was a spontaneous endothermic process and was well confirmed with pseudo-2nd-order kinetic model. Therefore, the adsorbent shows a potential application prospect. At the same time, it also provides an eco-friendly and inexpensive method for the effective utilization of other biomass resources and turning waste into treasure.