Novel Chitosan-Bentonite-Biochar Composite (CBBC) Barrier for Environmental Containment

Abstract Submission: Bentonite is widely used in environmental barrier systems due to its low permeability and ability to adsorb contaminants such as heavy metals, organics, and nutrients. However, its limited interactions with a wide range of contaminants and constrained adsorption capacities reduce its effectiveness. While several amendments and modifications have been made to enhance bentonite's adsorption performance, there is a pressing need for sustainable materials in such modifications. The current study investigates the development of a novel chitosan-bentonite-biochar composite (CBBC) barrier to improve the functionality of bentonite in terms of environmental containment properties. Chitosan, derived from the deacetylation of chitin—a naturally abundant polymer—has been extensively studied for its ability to remove a wide range of contaminants. Biochar, a carbon-rich material made by thermal decomposition of organic matter in the absence of oxygen, is recognized for its adsorption potential due to its large surface area and favorable surface functional groups. Specifically, chitosan derived from crustacean shells and biochar from corn stalks and hemp stalks were selected for this study. A novel methodology was developed for synthesizing CBBC from its constituent materials. The CBBCs synthesized in this study were tested for their ability to remove nutrients, specifically phosphate and nitrate, from synthetic stormwater. Batch tests were conducted with phosphate and nitrate solutions at varying concentrations (1to 8 mg/L for phosphate and 0.5 to 10 mg/L for nitrate), representing typical concentrations in stormwater runoff. The results showed a significant increase in the adsorption capacity of the CBBC compared to bentonite alone. The adsorption capacities of bentonite and CBBCs were modeled using isotherm models to understand the potential mechanisms involved. The results of this study offer valuable insights into the effectiveness of CBBC in enhancing the removal of nutrients, highlighting its potential as an efficient barrier in stormwater detention ponds or other waste-containing impoundments.

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