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

Abstract

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 CaCO3 induced by Bacillus subtilis, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd2+ and Pb2+ are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd2+ and Pb2+ were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd2+, 100% for Pb2+, and the desorption rate was smaller than 3%. Further experiments revealed that the biogenic CaCO3 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 CaCO3 adsorbed Cd2+ or Pb2+, it did not produce a new phase, which indicated that biogenic CaCO3 and heavy metal ions were governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO3 for Cd2+ and Pb2+ were mainly attributed to its large total specific surface area. The findings could improve the state of knowledge about biogenic CaCO3 formation in the environment and its potential roles in the biogeochemical cycles of heavy metals.

Bio-mineralisation, characterization, and stability of calcium carbonate containing organic matter

“…These biogenic CaCO 3 crystals are normally nanometric, of diverse crystal types, wrapped in rich organic matter, and complex elemental compositions, differing from non-biogenic carbonates. [1][2][3][4][5][6] Calcium carbonate deposition is a common phenomenon in seawater, fresh water, soil, and other environments. Calcium carbonate generates seven structural forms: calcite, monohydrocalcite, ikaite, aragonite, vaterite, hemihydrate calcium carbonate, and amorphous calcium carbonate (ACC), among which calcite is the most stable structural form at normal temperature and pressure.…”

“…10 Because the formation and precipitation of CaCO 3 lead to the deposition of atmospheric CO 2 , or reduces CO 2 emissions in water or soil, it plays a positive role in reducing atmospheric CO 2 concentrations and retarding the greenhouse effect. [28][29][30] In addition, biogenic CaCO 3 has good adsorption properties for heavy metals, 5 and compared with abiotic calcium carbonate, it shows greater potential. 31 Our purpose is to elucidate the nucleation patterns and crystallisation processes involved and determine the composition and structure of biogenic CaCO 3 .…”

“…Bacillus subtilis , as a popular strain used in microbial fertilisers, has been developed rapidly and widely in agricultural production across China. 5,32,33 During the process of bacterial culture, a large amount of ACC and vaterite precipitation was observed, which showed obvious biological effects. Although there are already some research reports on bacteria-induced carbonate, further study is still needed outlining the ACC and vaterite mineralisation micro-process induced by agricultural fertiliser strain.…”

Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist

“…They also act within mitochondria (Carafoli & Krebs, 2016), and hydrogenosomes, (Humphreys et al, 1994(Humphreys et al, , 1998, and a plethora of specialized organelles for life in highly specialized, variable, and sometimes stressful environments. Examples of the latter are manifest in gravitaxis (Häder & Hemmersbach, 2017), mineral nucleation (Omelon et al, 2013, Liu et al 2018) and acidocalcisomes (Docampo et al, 2013). The ubiquity of bound calcium in S. vortens and its persistence after formalin or ethanol fixation in cellular structures have prompted our extensive use of X-Rhod, 5F, AM, a fluorogen first employed by Gerencśer & Adam-Visi ( 2001) as an outstandingly revealing agent of the morphology of this protist.…”

Preparation and bacteriostatic research of porous polyvinyl alcohol / biochar / nanosilver polymer gel for drinking water treatment

“…To address this problem, calcium carbonate (CaCO 3 ) can be added to the PVA during the material preparation process (as was done in this study), and the CaCO 3 can be eluted during the subsequent processing so that the porosity of the PVA increases and the contact area with water increases, thereby enhancing the antibacterial effect. At the same time, calcium carbonate can bind metal ions with smaller radii, such as Cu 2+ and Pb 2+ 24 , 25 . Therefore, the addition of calcium carbonate also enhances the heavy metal adsorption capacity to bacteriostatic material.…”