Immobilization of vegetable tannins on tannery chrome shavings and their use for the removal of hexavalent chromium from contaminated water

Chestnut (C) and mimosa (M) tannins immobilized on chrome shavings (CS) as an adsorbent have been proposed to be an efficient and economical alternative in hexavalent chromium removal from aqueous solutions. The adsorption of hexavalent chromium onto chrome shavings-tannin (CS-T) adsorbents was performed using batch equilibrium technique at 25 ± 2 °C. The effect of pH is highly important especially in the case of high concentrations of hexavalent chromium. The maximum chromium uptake was obtained at pH 4. Two hours of contact time are enough to reach equilibrium. Sorption of chromium on CS-T was found to follow a pseudo-second order kinetic model (with correlation coefficients greater than 0.999). The adsorption equilibrium data fitted the Langmuir model well. The maximum adsorption capacity, of dry immobilized tannin adsorbent with 11.6% polyphenol, reached 42 mg Cr/g and 38 mg Cr/g in the case of chestnut and mimosa tannins, respectively.

► Vegetable tannins were immobilized on chrome shavings.
► This overcomes the disadvantage due to their solubilisation in water.
► Immobilized tannins were successfully used for the removal of Cr(VI) from water.
► Sorption is higher than that of several adsorbents described in the literature.
► Immobilized tannins are an efficient and low cost material for Cr(VI) removal.