Heavy metal removal from contaminated scallop waste for feed and fertilizer application

The present work elucidates environmental friendly removal process of heavy metals by using biomass waste and natural product. The process consists of the following three steps: (1) leaching of all metals including heavy metals by dilute sulfuric acid, (2) removal of turbid organic materials from the leach liquor by means of coagulation using astringent persimmon extract enriched with persimmon tannin leaving all heavy metal ions in the leach liquor and (3) adsorptive removal of heavy metals by means of adsorption onto the gel prepared from apple waste. The operational conditions at these three steps were discussed in detail, among which the pH adjustment is the key factor; i.e. the lower the pHs the higher the efficiency of the leaching, while reverse was the case for the adsorption.