Fabbricino M.,University of Naples Federico II |
Naviglio B.,Italian Leather Research Center |
Tortora G.,Italian Leather Research Center |
d'Antonio L.,University of Naples Federico II
Journal of Environmental Management | Year: 2013
Results of a lab-scale experimental study are presented that aim to verify the use of ground shrimp shells, not otherwise conditioned, as an adsorbent material to remove chromium(III) from tannery wastewater. The obtained removal efficiency is found to be always over 90%, confirming the capacity of the tested materials to remove chromium(III). The adsorption process is well described by the Brauner-Emmett-Teller isotherm, indicating the existence of both weak and strong adsorption sites inside the shells. Kinetic tests allow to verify that the removal process takes place rapidly during the first 2 h and then tends to reach a plateau: the pseudo second-order model is found to be able to simulate with good approximation, the adsorption process. Analyses comparing the treatment process using shrimp shells vs. other chemical products frequently used for chromium removal, supported by microscopic observations, indicate that the efficiency obtained using shrimp shell is comparable to the efficiency obtained using sodium bicarbonate and sodium hydroxide, but the removal mechanism is different as the adsorption on the polysaccharidic matrix of the shells prevails over the precipitation of chromium salts. The skin tanned with recovered chromium is found to be of low quality; on the contrary satisfying tanning results are obtained using, as tanning agent, the sludge produced by the adsorption process without any further treatment, except for pH correction. © 2013 Elsevier Ltd.