Scientists are working on different ways to recover silver from laundry wastewater, according to a report in ACS Sustainable Chemistry & Engineering.
The objective of the research is to prevent the entry of silver into the environment as some of the metal is washed away off clothes when they are put in the laundry.
Silver nanoparticles are integrated into clothing products by manufacturers to kill odour-causing bacteria.
Once these particles enter the environment, they are believed to cause harm to marine ecosystem and impact the effectiveness of bacterial processing during the treatment of wastewater.
According to the paper, recovering the nanomaterial from laundry water is affected by low concentrations of silver in the water and high concentrations of competing ions.
In addition, uncertainty regarding exact forms of silver are present in the wastewater makes it difficult to recover the metal.
Based on previous research by Sukalyan Sengupta and Tabish Nawaz, ion-exchange technology emerged as highly selective for silver.
However, the study did not take into account the role played by detergent chemistry, which could interfere with the method. As a result, the researchers decided to examine the impact of detergent chemistry in the current report.
During the study, the scientists identified that silver mainly exists as a positively charged ion after analysing how silver interacts with individual detergent ingredients.
The ion is said to interact with negatively charged ions in the detergent at different pH ranges.
The finding enabled the group to use an ion-exchange resin to recover as much as about 99% of the silver, depending on the pH and concentration of the ions.
The group tested the resin with detergent components and reused it over five cycles.
During the exercise, the resin continued to display the ability to remove silver, although the addition of bleaching and water-softening agents did not yield positive results, negatively impacting the resin’s efficiency.