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Silver Recovery from Laundry Washwater: The Role of Detergent Chemistry

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journal contribution
posted on 21.11.2017, 00:00 authored by Tabish Nawaz, Sukalyan Sengupta
The use of silver nanoparticles as an antimicrobial agent on textiles is rising. Ag leaching during laundry and its subsequent discharge in the environment pose ecotoxicological risks. Removing Ag from laundry washwater is therefore an environmental necessity, but its recovery also leads to environmental sustainability. Low Ag concentration, competition from other cations (such as Ca2+, Mg2+, and Na+), and complexity of the detergent matrix make the recovery process challenging. The present study utilizes a thiol-group functionalized ion-exchange resin in a fixed-bed column to remove Ag from laundry washwater and recover it as Ag2S nanoparticles or high-purity powder. The role of each detergent component in affecting Ag speciation and the resin performance has been analyzed. Builders and bleaching agents are reported to negatively impact the resin performance. pH and cocationic species (Ca2+) concentration are reported to be critical parameters for the successful recovery scheme. The work demonstrates a closed-loop sustainable scheme by recycling and reusing the resin and the regenerant solution over 5 cycles.