Enhanced coagulation process for removing dissolved organic matter, microplastics, and silver nanoparticles

Abstract

Dissolved organic carbon (DOC), microplastics (MPs), and silver nanoparticles (AgNPs) in water are of major concern because of their direct and indirect toxic effects on aquatic organisms and human exposure via water. This work investigated the effect of poly aluminum chloride (PACl) coagulation for reducing DOC, MPs, and AgNPs. This work used water from a canal in Thailand with a DOC of 5.2 mg/L in the experiment. AgNPs of 5–20 mg/L were added to canal water to create synthetic water for the PACl coagulation. Polyethylene and polypropylene (PP) type MPs were identified in the raw water with Fourier transform infrared spectroscopy. Coagulation with 15 mg/L of PACl performed better in the PP removal. The PACl coagulation at dosages of 15, 40, and 70 mg/L removed DOC by 16–20%, 44–52%, and 46–63% and AgNPs by 34–90%, 53–93%, and 81–95%, respectively. The presence of AgNPs at high levels could inhibit the efficiency of DOC reduction by the PACl coagulation. The FESEM identified the adsorption of silver-containing nanoparticles onto the flocs with increased dosages of PACl. So, PACl is a coagulant in the removal of AgNPs that can reduce health hazards and eco-toxicological risks in water sources due to the release of silver.

Keywords:

• Coagulation
• microplastics
• polyaluminium chloride
• removal characteristics
• silver nanoparticles

Acknowledgments

The authors would like to thank the Faculty of Engineering, Prince of Songkla University, Hatyai Campus for assistance with the equipment.

Data available

The authors confirm that the data supporting the findings of this study are available within the article and Appendix.

Additional information

Funding

The work was funded by the Center of Excellence on Hazardous Substance Management (HSM), Bangkok, Thailand under contract number HSM-PJ-CT-18-20.