Energy-saving preparation of a bioflocculant under high-salt condition by using strain Bacillus sp. and the interaction mechanism towards heavy metals

A highly efficient bioflocculant, i . e ., Na-Bsp was successfully prepared by using a tolerant strain- Bacillus sp. under high-salt condition without sterilization. Salt-containing medium was not infected by other strains throughout the whole incubation period in 168 h. The as-prepared Na-Bsp was found to be cation-dependent, exhibiting high flocculant efficiency (FE) i.e., 97.69 ± 0.61%, towards kaolin particles by aid of Fe 3+ . High FE values were well maintained under a wide pH range and/or boiled water treatment , likely because of the main constituent of polysaccharide . The presence of hydroxyl, carboxyl, and amine groups on the bioflocculant surface were possibly responsible for strong interactions with heavy metals. The adsorption capacities of Pb 2+ , Cu 2+ and Cr 6+ were 1000.0, 434.8 and 384.6 mg g −1 , respectively. The changing of structure and configuration of bioflocculant during the metal adsorption were explored by the scanning electron microscope with electron energy loss spectroscopy and three-dimensional excitation-emission fluorescence spectrometry . This study provided a novel production method, whereby the conventional sterilization could be avoided, which is of great environmental significance for steam-saving. Furthermore, the as-prepared Na-Bsp exhibited high adsorption capacities toward heavy metals, which sheds lights on its potential usage as an alternative adsorbent.