Cork waste for metal removal from aqueous solution

In this work the potencial of cork waste to remove Cu (II) and Cr (VI) from aqueous solutions has been studied. Raw cork and biochar prepared by pyrolysis of the cork, were used. Kinetic and equilibrium batch sorption experiments were performed in order to compare the sorption efficiency of each material. Adsorption isotherms were expressed by Langmuir and Freundlich equilibrium models. Moreover the batch kinetic experiments were fitted to the commonly pseudo-first-order and pseudo-second-order equations. The results showed that the metal removal using raw cork as the sorbent is pH-dependent with the uptake of 61.5% for chromium at pH 3 and 55.6% for copper at pH 6. Two types of cork size (0.5mm and 2 mm particle size) showed the same adsorption potential. Biochar with high specific surface area (300 m2 g-1) can be easily prepared from the raw cork. The raw cork results show that pseudo-second-order describe better kinetic data for both metals. According to kinetic data the adsorption of chromium using biochar is the best option for removing this metal from water. Biochar is able to sorb copper and chromium. The Langmuir model is not able to fit the experimental values for Cr, nevertheless is able to fit Cu, where the maximum adsorption was 13.4 mg kg-1. Freundlich model can fit the experimental values for both metals. Where Cu maximum adsorption was 14.8 mg kg-1 and Cr maximum adsorption was 4.6 mg kg-