Reutilization of melamine‐formaldehyde foam wastes: Removing Sn2+ in simulated tin‐containing wastewater to transform a fire hazard suppressant of flexible poly(vinyl chloride)

Abstract Melamine‐formaldehyde (MF) foam has wide applications due to good flame retardancy, excellent sound absorption, and high thermal stability. However, the recycling of MF foam wastes remains a challenge due to its thermosetting nature. Here, we demonstrate a new strategy for discarded foams as solid adsorbents for removing tin ions in simulated tin‐containing wastewater. Results showed that the removal rate of tin in simulated wastewater is as high as 99.996%. Moreover, after simple calcination, as‐obtained products can be used as high‐efficiency flame retardants for flexible poly(vinyl chloride) (PVC), reducing the peak of heat release rate and total smoke production of PVC by 51.8% and 45.8%, respectively, under the condition of 2.5 wt.% addition. In short, this strategy successfully converted MF foam and tin wastewater to valuable flame retardants, opening the way for the environmentally friendly recycling of MF waste and the simultaneous treatment of tin‐containing wastewater.