Technology : Bubbles boost silver recycling

时间:2019-02-27 07:03:01166网络整理admin

POURING precious metals down the drain is not only expensive but environmentally unsound. Silver-based solutions are widely used in photography, and normally only about 80 per cent of the silver is recovered for reuse. But Bruno Pollet, a postgraduate at Coventry University, says he can recover 95 per cent using ultrasound to boost the traditional recycling process. The most common way of recovering silver is electrolysis, in which silver ions are deposited as a metal on a stainless steel cathode. Pollet says that ultrasound can make this process more effective. The slowest stage in silver electrolysis is the silver ions’ journey across the diffusion layer, a static layer of fluid that normally clings to solid surfaces, including cathodes. This holds up the whole process. Ultrasound disrupts this layer by creating tiny bubbles in the fluid that send out high-pressure jets as they collapse. These jets squirt through the diffusion layer and give the ions an easier passage. The use of ultrasound to enhance chemical processes, or sonochemistry, is being investigated by several researchers. But Pollet says he and his supervisors, Phil Lorimer and Tim Mason, are the first to look at silver reclamation. “The beauty of this process is that it can also be used to reclaim a variety of other metals, such as zinc, cadmium and lead,