Abstract
In present work, environmentally benign green aragonite crystals were synthesized from waste chicken eggshells and bivalve seashells through a simple and low-cost wet carbonation method. This method involves a constant stirring of calcium oxide slurry and magnesium chloride suspension in aqueous solution with constraint carbon dioxide injection at 80 °C. The physicochemical properties of the synthesized aragonite were further compared with the aragonite synthesized from commercial calcium oxide. The morphological analysis, such as acicular shape and optimum aspect ratio (~21), were confirmed by scanning electron microscopy. The average crystal size (10–30 µm) and specific surface area (2–18 m2 g−1) were determined by particle size and Brunauer–Emmett–Teller analysis, respectively. Moreover, a schematic crystal growth mechanism was proposed to demonstrate the genesis and progression of aragonite crystal. Green aragonite can bridge the void for numerous applications and holds the potential for the commercial-scale synthesis with eggshells and bivalve seashells as low-cost precursors.
Highlights
Precipitated calcium carbonate (PCC) has emerged as a potential inorganic material with numerous industrial applications, as filler in polymers, paints, and paper [1,2]
The present study simultaneously focuses on two problems, i.e., inorganic solid food waste management and potential alternative of limestone for the synthesis of aragonite
It has been observed that the waste shells are well equipped to be used as precursors for green aragonite synthesis as there were no considerable morphological changes when compared with aragonite synthesized from COCOMM
Summary
Precipitated calcium carbonate (PCC) has emerged as a potential inorganic material with numerous industrial applications, as filler in polymers, paints, and paper [1,2]. Synthesis of acicular shaped aragonite is evident in many studies [1,2,7,8]. A study reported that a controlled injection of CO2 in calcium hydroxide slurry suspended magnesium chloride aqueous solution can synthesize needle-shaped aragonite [7]. The remaining magnesium chloride solution can be reused for further aragonite synthesis as Mg2+ and Cl− ions are not assimilated into aragonite crystals. Mg2+ ions act as an impurity ion and promote the formation of aragonite, while simultaneously impeding the nucleation and growth of calcite crystal [7]. Another study suggested that a higher concentration of Mg2+ ions favors crystal growth of aragonite [8]. Numerous theories and empirical relationships have been proposed to rationalize this cognition, such as alteration of surface charge, inhibition of calcite nucleation, calcite poisoning model, and lack understanding related to kinetics of cation dewatering [8,9]
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