Removal of Zn(II) and Cr(VI) ions from aqueous medium by anionic plant-based surfactant impregnated activated carbon

Herein, anionicplant-based surfactant (sodium lauryl sulfoacetate, SLSA) was introduced for impregnation onto activated carbon (AC). This study was intended to assess its use as a potential adsorbent for removing Zn(II) and Cr(VI) ions from aqueous medium. The virgin and the impregnated AC were characterised using Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Meanwhile, their performances to remove each metal ion were measured through batch adsorption experiments over a range of SLSA concentrations (10-175 mg/L) in 6 h contact time. The results revealed that Zn(II) ion removal was gradually increased as the SLSA concentration increased. The maximum removal was obtained at SLSA concentration of 75 mg/L (SIAC-75) with 31.66% of Zn(II) ion removal. However, an opposite trend of Cr(VI) ion removal was observed as the SLSA concentration increased. It is proposed that electrostatic interaction mechanism may occur during the adsorption process. The introduction of sulfonate group (OSO3-) via SLSA impregnation imparted a negatively charged surface on AC, thus resulting in an electrostatic attraction between Zn(II) ion. However, as Cr(VI) ion may dissociate into chromate (CrO42-) ion, an electrostatic repulsion would occur. Therefore, in this study, the modified adsorbent prepared would be potentially preferred to remove Zn(II) ion.