Preparation of Cyanobacterial Blooms-Originated Adsorbent for the Removal of Cadmium Ions

<p>A frequency of cyanobacterial blooms appearance in lakes has been increasing as a consequence of eutrophication together with global warming. Although cyanobacterial blooms have been removed/collected by a suction method, there are few ways to effectively use the cyanobacterial biomass. If added values such as adsorptive function for pollutants in aqueous solution can be provided to the cyanobacterial biomass, it would be contributed to solve problems on cyanobacterial blooms and water pollution. This study aimed to prepare adsorbent from cyanobacterial bloom sample collected in a eutrophic lake for the removal of pollutants, and attempted to remove Cd²⁺ by cyanobacterial blooms-originated adsorbent (CBA) prepared via dehydration treatment using a concentrated sulfuric acid. As a result, CBA possessed smaller specific surface area (13.1 m²/g) and higher amount of total acidic functional groups (8.29 mmol/g), and the maximum amount of Cd²⁺ adsorption was 1.43 mmol/g, which was higher than oxidized activated carbons. From these values, the number of carboxy groups per unit surface area was calculated to be 1.51 × 10²⁰ number/m², and the distance between carboxy groups was estimated to be 8.14 × 10⁻² nm, which would be one of the major reasons of higher amount of Cd²⁺ adsorption. Furthermore, adsorption/desorption experiments were repeatedly conducted 3 times, and the results showed that the adsorption amount and recovery rate were not largely varied, indicating that CBA can be reused for the Cd²⁺ adsorption. These results suggest that the preparation of adsorbent for the removal of Cd²⁺ would be one of the effective ways for the effective utilization of cyanobacterial biomass.</p>