ABSTRACT
Pine bark (NPB) is a common agricultural waste in Portugal and was investigated as biosorbent in its natural state and after sodium hydroxide treatment (MPB). Surface modification was carried out using NaOH solutions with concentration 10, 20 and 30% (wt%). The best adsorption capacity of NPB was 8.35 mg g−1, while with MPB the maximum was 17.06 mg g−1. A Box-Behnken design was used to obtain the response surface and identify the optimal operating region as well as the variables with the most influence on Cr(III) removal efficiency. The results showed that the Cr(III) adsorption is favored in the case of the initial pH 4.8, initial Cr(III) concentration of 137.3 mg L−1, liquid-to-solid ratio of 200. The temperature did not affect the process. As main conclusion, this study demonstrated that this low cost biosorbent has good potential to recover chromium from wastewaters, and at the same time protect environment.
