Nano zero-valent iron immobilized onto biochar: an effective solution for mitigating microplastic contamination in aquatic ecosystems Yohana M. Kishiga, Makungu M. Madirisha, Regina P Mtei Department of Chemistry, College of Natural and Applied Sciences, University of Dar es Salaam, Tanzania The pervasive presence of microplastic pollutants in aquatic environments represents a pressing global concern due to its adverse impacts on living organisms. To address this issue, this study delves into the synthesis of nano zero-valent iron immobilized onto biochar derived from cashew nut shells (CNS) as a means to mitigate microplastic contamination in aquatic ecosystems. The XRD analysis unequivocally confirmed the presence of distinct diffraction peaks in the synthesized nano zero-valent iron immobilized onto biochar (nZVI/BC), signifying well-defined crystalline structures in the zero-valent iron component. Conversely, the biochar component exhibited an amorphous nature. The successful immobilization of nZVI onto the biochar matrix was clearly established. The UV-Vis Spectrophotometer analysis revealed robust absorbance signals corresponding to iron metal in the composite formulation. Furthermore, the BET results indicated a proportional increase in specific surface area with higher pyrolysis temperatures, suggesting that biochar produced at elevated temperatures offers enhanced adsorption capabilities. Additionally, both the specific surface area and pore volume of the composite surpassed those of the corresponding biochar. In terms of adsorption capacity, it was evident that the nZVI/BC composite synthesized at 700 °C displayed superior adsorption capacities for microplastics when compared to those produced at 300 and 500 °C. The research findings make a significant contribution to the principles of the circular economy by demonstrating the use of waste biomass, specifically cashew nut shells, to produce biochar and integrate it into environmentally beneficial applications. This aligns with Sustainable Development Goal 13 (Climate Action) by mitigating greenhouse gas emissions associated with waste disposal and energy-intensive production processes. Moreover, it supports Sustainable Development Goal 12 (Responsible Consumption and Production) by reducing waste and promoting resource efficiency through the utilization of agricultural waste (cashew nut shells) for microplastic removal. This work also addresses the global issue of microplastic pollution, in accordance with Sustainable Development Goal 14 (Life Below Water) and Sustainable Development Goal 15 (Life on Land), which focus on conserving and sustainably managing marine and terrestrial ecosystems.
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