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Biosafety Assessment of Clay-Based Utensils from Three Regions of Mozambique

Abstract

This study aimed to characterize clay deposit from three regions in Mozambique (Macupulane, Mutamba and Lichinga), evaluate the leaching of heavy metals into water boiled in clay pots produced by those clays and the non-carcinogenic human health risk. Raw clays sample were subjected to physicochemical (pH, specific surface area, and cation exchange capacity), thermal, elemental and mineralogical characterization. Furthermore, clay samples were used to produce handcrafted clay pots at different kiln temperatures (800 to 1000°C). To simulate heavy metal leaching during boiling distilled water were heated for 3, 4, and 5 hours during three consecutive days (cycles) to simulate real-life use of clay pots. Mineralogical analysis using X-ray Diffraction (XRD) revealed that kaolinite was the predominant clay mineral in Mutamba and Lichinga clays (63.10% and 67.10% wt.%), while quartz dominated in Macupulane clay (79.70 wt.%). X-ray Fluorescence (XRF) analysis indicated that all samples were primarily composed of SiO2 (47.11% to 84.92% by weight) and Al2O3 (4.92% to 26.44 wt.%). The thermal behavior of the clays aligned with their mineral composition. Leaching experiments demonstrated that Macupulane clay pots exhibited higher heavy metal leaching into boiled water during the third heating cycle and after 5 hours of boiling. The leaching process was significantly influenced by boiling time, kiln temperature, raw clay source, and repetitive use of clay pots (p<0.05). Human health risk assessment revealed that arsenic, cadmium, and chromium were the most leached heavy metals, posing unacceptable non-carcinogenic risks to consumers of water or food prepared in those clay pots.

Cossa P, Sitoe A, Madivate C, Attore F, Manhique A*

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