Enhanced removal of aqueous chromium(VI) by KOH-activated soybean straw-based carbon

Activated carbon has attracted much attention in the remediation of heavy metal pollution; however, it is still a challenge to explore a cheap and efficient activated carbon for the removal of chromium(VI) from water. In this study, based on the concept of treating pollution with waste, a high adsorption performance activated carbon was prepared by in situ carbonization and activation of soybean straw residue with potassium hydroxide as a chemical activator for the purpose of enhancing Cr(VI) removal capacity. The structure and property of the generated soybean straw-based activated carbon (SSAC) was characterized by SEM, FTIR, BET analysis, and XPS. The influence factors (i.e., pH, adsorbent dosage, initial Cr(VI) concentration) on the removal of Cr(VI) by SSAC were studied by batch experiments. Results revealed that SSAC not only exhibited porosity with a huge specific surface area of 1800.28 m(2) g (-1) but also had abundant electron-donating groups (such as C =C, C-OH) on the surface to reduce Cr(VI) to Cr(III), which both promoted a high adsorption capability with the maximum Cr(VI) adsorption capacity of 294.12 mg g(-1) at pH =2. The adsorption process was in accordance with the Langmuir model and the pseudo second-order model corresponding to monolayer and chemical adsorption, respectively, and it was spontaneous and endothermic. As for the study of mechanism, reduction and electrostatic adsorption may dominate the removal of Cr(VI) by SSAC. All these results indicated that SSAC had the potential to efficiently remove Cr(VI) in aqueous solutions, which may be a promising adsorbent to provide a potential solution for solving the problems of heavy metal pollution and straw agricultural residue disposal.

Automated summary

In this study, a high adsorption performance activated carbon was prepared from soybean straw residue for efficient removal of chromium(VI) from water. The generated soybean straw-based activated carbon had a large specific surface area and electron-donating groups on the surface, which promoted a high adsorption capability. The adsorption process was found to be spontaneous, endothermic, and dominated by reduction and electrostatic adsorption mechanisms.