In situ remediation efficacy of hybrid aerogel adsorbent in model aquatic culture of Paramecium caudatum exposed to Hg(II).

Silica-gelatin hybrid aerogel of 24 wt% gelatin content is an advanced functional material suitable for the high performance selective adsorption of aqueous Hg(II). The remediation efficacy of this adsorbent was tested under realistic aquatic conditions by exposing cultures of Paramecium caudatum to Hg(II) and monitoring the model cultures by time-lapse video microscopy. The viability of Paramecium was quantified by analyzing the pixel differences of the sequential images caused by the persistent movement (motility) of the cells. The viability of Paramecium displays a clear exposure-response relationship with Hg(II) concentration. Viability decreases with increasing Hg(II) concentration when the latter is higher than 125 μg L. In the presence of 0.1 mg mL aerogel adsorbent, the viability of the cells decreases only at Hg(II) concentrations higher than 500 μg L, and 220 min survival time was measured even at 1000 μg L Hg(II). The effective toxicity of Hg(II) is lower in the presence of the aerogel, because the equilibrium concentration of aqueous Hg(II) is low due to adsorption, thus Paramecium cells do not uptake as much Hg(II) as in the un-remediated cultures. Video imaging of Paramecium cultures offers a simple, robust and flexible method for providing quantitative information on the effectiveness of advanced materials used in adsorption processes for water treatment.