Removal of Cr(VI) from aqueous solution by a commercial carbon black

Hexavalent chromium is classified as a human carcinogen of high carcinogenic hazard according to the US EPA. Therefore, batch adsorption experiments aiming at Cr(VI) removal from an aqueous solution were carried out using a commercial carbon black (CB) as an adsorbent. The CB was characterized by the Brunauer-Emmett-Teller and Barrett-Joyner-Halenda, scanning electron microscopy with energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy methods. Various parameters were tested, including adsorbent dose, solution pH, contact time, initial metal concentration, and temperature, so as to determine their relation to the adsorption yield. The results showed that an initial solution of pH 2.4 was most favorable for the Cr(VI) removal. The equilibrium data were analyzed by the Freundlich, Langmuir, and Temkin isotherm models. The equilibrium data best fitted according to the Freundlich isotherm model. The CB maximum adsorption capacity was found at 33.22 mg/g, thus proved to be promisingly efficient in comparison to other low-cost adsorbents. The thermodynamic parameters yielded by this study showed that the Cr(VI) adsorption on the CB was the spontaneous exothermic process.