The Response of Microalgae Chlorella sp. to Free and Immobilized ZrO 2 and Mg(OH) 2 Nanoparticles: Perspective from the Growth Characteristics

Abstract

The biological response of Chlorella to nanometal oxides is the basis for expanding the engineering application of Chlorella and inorganic metal oxide nanoadsorbents in the treatment of nitrogen and phosphorus wastewater. The objective of this study was to ascertain the response of Chlorella to nano-ZrO₂ and nano-Mg(OH)₂ either free or immobilized to anion exchange resin D301. Our results show that immobilization of ZrO₂ and Mg(OH)₂ to D301 was significantly less harmful (p < 0.05) to Chlorella than free nano-ZrO₂ and nano-Mg(OH)₂. Chlorella has greater tolerance and positive biological response to fixed nanometal oxides, especially to D301-ZrO₂ (nano-ZrO₂ immobilized on D301), which can significantly stimulate the growth of Chlorella. Scanning electron microscopy observations indicated that most of algal cells treated with free nano-Mg(OH)₂ and nano-ZrO₂ were entrapped in the aggregates of nanoparticles and were both deformed and atrophied in appearance. In contrast, D301-Mg [nano-Mg(OH)₂ immobilized on D301] immobilized beads demonstrated relatively few malformed algal cells on the surface, and D301-Zr showed no indications of deformed or atrophied cells either within or on the immobilized beads. Therefore, immobilization appears to have obvious effect on reducing the toxicity of powder nanoparticle and carrier, and the immobilization of ZrO₂ and Mg(OH)₂ on D301 might provide a novel application to Chlorella wastewater treatment to improve algae wastewater treatment efficiency, as well as these sorts of immobilized nanoadsorbent might be regenerated using Chlorella.