Discharging a high-energy spark underwater creates a shock wave which dissipates through an acoustic field. The hydroxyl radicals created by the field are able to mildly oxidize the surfaces of ink and toner particles, thereby decreasing their zeta potential. This decrease inhibits the tendency of these particles to attach to fiber, which is negatively charged. Pilot studies showed that sparking a mixture of ONP and OMG increased both brightness and yield by 1% when the treated furnish was subsequently subjected to flotation deinking. The hydroxyl radicals are also able to oxidize the surface of microstickies and promote their agglomeration. The agglomerated particles are more easily rejected by reverse cleaners as shown in a full-scale trial. A mill trial also showed that the sparker improved clarification efficiency in a DAF.
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