AUTHOR=Liu Renlu , Guan Yong , Chen Liang , Lian Bin 

TITLE=Adsorption and Desorption Characteristics of Cd2+ and Pb2+ by Micro and Nano-sized Biogenic CaCO3

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00041

DOI=10.3389/fmicb.2018.00041

ISSN=1664-302X

ABSTRACT=<p>The purpose of this study was to elucidate the characteristics and mechanisms of adsorption and desorption for heavy metals by micro and nano-sized biogenic CaCO<sub>3</sub> induced by <italic>Bacillus subtilis</italic>, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd<sup>2+</sup> and Pb<sup>2+</sup> are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd<sup>2+</sup> and Pb<sup>2+</sup> were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd<sup>2+</sup>, 100% for Pb<sup>2+</sup>, and the desorption rate was smaller than 3%. Further experiments revealed that the biogenic CaCO<sub>3</sub> could maintain its high adsorption capability for heavy metals within wide pH ranges (3–8). The FTIR and XRD results showed that, after the biogenic CaCO<sub>3</sub> adsorbed Cd<sup>2+</sup> or Pb<sup>2+</sup>, it did not produce a new phase, which indicated that biogenic CaCO<sub>3</sub> and heavy metal ions were governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO<sub>3</sub> for Cd<sup>2+</sup> and Pb<sup>2+</sup> were mainly attributed to its large total specific surface area. The findings could improve the state of knowledge about biogenic CaCO<sub>3</sub> formation in the environment and its potential roles in the biogeochemical cycles of heavy metals.</p>