Reuse of waste casein peptides to capture Cu (II) for long-term antibacterial reutilization

To date, researchers have worked on developing new pathways to control and manage food and industrial wastes (e.g. dairy wastewater, heavy metals, etc.), but most do not involve the reuse of these wastes. Herein, we propose to use casein peptides (CPs) based on dairy waste to capture Cu2+ from industrial wastewater, which is reduced to copper and cuprous oxide nanoparticles (consisting of metallic Cu and Cu2O crystalline phases) distributed on CPs. The prepared product CPs/Cu/Cu2O NPs showed prominent antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as multidrug-resistant bacteria from livestock wastewater through generating reactive oxygen species (ROS) in combination with released Cu2+. The method proposed in this study is also applicable to extract Cu2+ from actual electroplating wastewater for bacterial disinfection. Finally, we achieved the modulation of the composition of Cu/Cu2O NPs loaded on CPs. [Display omitted] •Conversion of dairy waste casein to casein peptides as a green adsorbent.•Recovery of Cu2+ ions from wastewater and in situ reduction to Cu/Cu2O NPs.•The CPs/Cu/Cu2O NPs formed after capturing Cu2+ have excellent antimicrobial activity.•Adjustable ratio of Cu and Cu2O in CPs/Cu/Cu2O NPs.