Collaborative Research: Development of Novel Chitosan-Biochar-Bentonite Composite Barrier Resilient to Changing Climate: Synthesis, Characterization, and Containment Mechanisms

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Climate change is linked to the steady increase in occurrence and severity of flooding events world-wide, exposing those impacted to large volumes of floodwaters and the contaminants they carry. Contaminant types vary widely, which challenges the functionality of traditional contaminant barrier systems. This research will develop novel composite materials derived from low-cost waste materials – chitosan and biochar – and bentonite as sustainable, adaptive, and resilient barrier materials. Chitosan, a biopolymer derived from crustacean shells, and biochar, a carbonaceous byproduct produced from waste biomass, can each remove different contaminant types from floodwater. The key innovation of this work is the ability of the combined synthesized materials to remove a wide range of contaminant molecules of varying size and charge, such as heavy metals, nutrients, and organics, from floodwater while functioning as a containment barrier. This work will address the need to develop sustainable engineered barrier materials that effectively mitigate flooding and intercept the transport of many contaminant types potentially found in floodwaters. This award will support outreach to K-12 students and teachers, undergraduate and graduate engineering students, academics, and public agencies through activities such as organized field trips, workshops, and seminars.The goal of this work is to develop composites synthesized from low-cost, waste materials – chitosan and biochar – as sustainable, adaptive, and resilient barrier materials in containment systems for simultaneous flood mitigation and contaminant sequestration. The research objectives are: (1) develop repeatable methods for chitosan-bentonite composite, chitosan-amended biochar, and chitosan-biochar-bentonite composite synthesis, (2) investigate the physico-chemical and electrical binding mechanisms of chitosan with bentonite and biochar through characterization studies such as zeta potential measurement, (3) investigate contaminant sequestration/degradation and chemical compatibility ranges of the synthesized composites under changing climate conditions (pH, ionic strength, dissolved organic content, and contaminant mixtures) through batch studies, and (4) investigate the potential of chitosan-biochar-bentonite composites for contaminant sequestration in containment applications and derive contaminant transport parameters through column studies. The contributions expected from this work are: (1) developing sustainable, adaptive, low-cost containment barrier materials, (2) understanding the fundamental mechanisms governing the physico-chemical interactions between the synthesized materials and the selected contaminants, and (3) assessing chemical and environmental compatibility of the synthesized materials for effective adsorption of the selected contaminants. The synthesized materials have potential to be adapted for many containment applications such as lined retention ponds and landfill liners.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.