Toxicity of CuFe and Co-doped CuFe layered double hydroxides on algae: Insights into synthesis, growth inhibition, morphological changes, and antioxidative enzyme responses

Layered double hydroxides (LDH) are widely used in a variety of industries due to their unique structural characteristics. It is essential to comprehend the environmental behavior and toxicological impacts of these substances to address potential risks caused by LDH release into the environment. In this study, CuFe and Cobalt (Co)-doped CuFe LDHs were synthesized and their toxicities to Chlorella vulgaris were investigated. In the scanning electron microscope images, the Co-doped and undoped catalysts appeared as uniformly dispersed flakes. The X-ray diffraction pattern of the Co-doped CuFe LDH confirmed the successful incorporation of Co into the crystalline lattice of the LDH. The growth of C. vulgaris was negatively affected by the presence of 1 mg/L LDHs, with membrane damage and cell wrinkling observed with 20 mg/L. The CuFe LDH-exposed algae exhibited a significantly greater decline in chlorophyll content compared to that of the Co-doped LDH-exposed algae. However, superoxide dismutase activity was elevated in algal cells exposed to the Co-doped CuFe LDH. Catalase activity increased up to 20 mg/L, followed by a decline at higher doses in CuFe LDH-exposed cells. From an ecological perspective, the lack of increased toxicity after Co doping is favorable for aquatic life. The extensive characterization, together with a rigorous toxicity assessment, provides new information about the environmental safety of cobalt doping to aid in the development of safer and more sustainable LDH-based products.