Developments of cadmium removal systems for residues wasted from scallop processing manufacture by an electrochemical method

摘要

A large amount of organic residue containing cadmium is generated and wasted from scallop processing manufacture. In order to recycle the organic residue of scallop mid-gut glands, as fish meal and fertilizer, a new technology has been developed for removing the harmful cadmium. This treatment method consists of both the process of sulfuric acid leaching, and the process of the electrodeposition of cadmium. In this investigation, a demonstration plant to enable one batch treatment of about 100 kg/day, was designed on the basis of the results of a fundamental experiment, in which the effects of several factors on cadmium removal efficiency were examined by a small scale test, and a prototype plant was built. Finally, a demonstration test was conducted. The concentration of cadmium in organic residue from scallop processing manufacture was reduced to 5 mg/kg or less (based on dry weight), by improving the dipping tank in the leaching process and the rectifier in the electrodeposition process, at the demonstration plant. The running cost of operation was reduced by starting the electrolysis of cadmium after a set period of acid-dipping of organic residue, and by clarifying several key notes on cyclic running. Moreover, a final treatment method for electrodeposits such as heavy metals was successfully demonstrated. In this method, the deposits were dissolved in sulfuric acid solution, and recycled as mineral resources.