The ICT joins a new project to develop novel PCB effluent treatment processes using materials from crab shells

The ICT has recently joined a new multi-partner research and development project to investigate the use of materials derived from crab shells for capturing and recovering metals from PCB manufacturing effluent. With funding support from the UK’s Technology Strategy Board (TSB), the seven partner, two year STOWURC (Sustainable Treatment of Waste Using Recycled Chitosans) project is aimed at developing sustainable materials and processes that use waste products from the seafood industry to treat effluent and recover metals such as copper.

The shells of crabs and other crustaceans, such as shrimps and lobsters, are a source of materials known as chitosans which have the ability to absorb metals including copper and nickel, as well as certain organic materials. They are thus able to recover the metals that are commonly found in PCB manufacturing effluent. The UK's seafood industry generates large volumes of shellfish waste which contains a material known as chitin. These materials are typically deemed to be of no value and are sent for disposal, often at a considerable cost. Therefore, the possibility of finding a use for these chitin-based materials could provide a sustainable use for what is currently an undesirable waste product. Although, the chitin found in crab shells absorbs metals, it can be easily converted, via a simple de-acetylation process, to chitosan, which is an even more efficient absorber. A major objective of the project is to use these waste materials to produce chitosan-based granules that can sustainably treat the effluent produced by PCB makers and companies producing similar types of metal-bearing waste products.

A key initial aspect of the project will be to change the crab shells into useable materials and this will involve their mechanical and chemical conversion into a granular form with optimized absorption capabilities. The materials will then be evaluated over a range of operating conditions to determine how well they can absorb copper. Once saturated with copper, it will be desorbed into a solution from which it can be recovered as a metal by electroplating. The overall aim is to use the materials produced from the crab shells in a similar manner to ion exchange resins, so that once the metal has been desorbed, the chitosan materials can be reused. Again, the influence of absorption, desorption and plating conditions will be studied in order to optimize the overall process efficiency. Ultimately, the project partners are aiming to develop regenerable chitosan-based materials and to define accompanying processes for a range of metals.

The project consortium represents the whole requisite supply chain, from a supplier of crab shells to an end user PCB fabricator. Specifically, the partners are Kynance Cornish Crab, Chestech, Env-Aqua Solutions, C-Tech Innovation, Invotec, the Surface Engineering Association and the Institute of Circuit Technology. In addition to their own desire to develop and exploit the new technology, the project partners have also identified international interest in using chitosan-based materials from PCB manufacturers and there are also potentially much larger applications in other sectors, including surface engineering and metal finishing. The ICT is the dissemination partner for the UK PCB industry and it will deliver details of the project and progress to its members via presentations at its evening seminars and through articles in the Institute’s journal.

Crab shells constitute a waste product that is typically expensive to dispose of; if successful, this project will enable them to become valuable raw materials that can used to treat waste from across a range of industries.

Martin Goosey

December 2013