Reuse of Fishery Waste for Chromium(III) Removal from Wastewater

During last fifteen years many efforts have been done to consider some industrial residues as adsorbent materials able to remove heavy metals, dyes and other pollutants from industrial wastewaters. Use of residues as non conventional adsorbents is economically convenient as traditional adsorbents are characterized by high costs which tends to limit their applications despite good performances often related to adsorption processes. The number of tested residues as low-cost adsorbents is not negligible, as testified by a considerable number of papers dealing with this specific subject. Among others agro-industrial ones, such as coffee and tea waste, sugar waste, rice ad wheat residues, pistachio and peanut hulls, strawberry leaves, grass waste, almond and hazelnut shells, and oil mill solid residues, play a primary roles for dyes and heavy metals removal, and have been proved efficient also for cyanide and ammonia nitrogen adsorption. For heavy metals fly ashes have also been tested with good results. Starting from the encouraging results reported in these papers, it has been carried out an experimental research aimed at investigating the possibility of re-using wastes coming from fishery industry for the removal of chromium from tannery wastewater. Tannery industry is one of the prominent activity in Italy, producing about 5 thousands billion Euros per year, and covering about 70% of European production and a little less than 20% of word production. Tanneries use large amount of chromium to stabilize animal hides, so it is not rare to find, in spent tanning baths, Cr(III) concentrations reaching several thousands milligrams per liter. It follows that chromium removal from tannery wastewater represents a big priority for environment conservation. The reason for testing fishery waste as adsorbent material, particularly wastes coming from crustacean processing, is due to the high content of chitin into fish shells, which is the compound from which is obtained, by de-acetylation, chitosan, a well known chelating compound frequently used as chromium sequestrating agent. Moreover fishery waste disposal represent a big deal not only in Italy, but also in many other countries, such as Canada, Japan, and Alaska, characterized by an ancient tradition of seafood consumption. The most important characteristic of the study presented in the paper is the use of the residues simply washed and grinded without recourse to any other processing, and the comparison made with performances obtained using more traditional adsorbent materials.