AUTHOR=Tagar Uroosa , Volpe Maurizio , Messineo Antonio , Volpe Roberto 

TITLE=Highly ordered CaO from cuttlefish bone calcination for the efficient adsorption of methylene blue from water

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1132464

DOI=10.3389/fchem.2023.1132464

ISSN=2296-2646

ABSTRACT=This study focuses on the synthesis of highly ordered CaO via calcination of cuttlefish bone (CFB), at two different temperatures (900  and 1000 °C) and two holding times (0.5 and 1 h), as a potential green route for water remediation. The aim of this study is to synthesize cheap and highly ordered CaO from CFB as a green alternative to conventional adsorbents such as activated carbon. The highest calcination temperature 1000 ℃ was used to assess the morphological changes in CaO. The as-prepared highly ordered CaO was tested as an adsorbent using methylene blue (MB), as a model compound for dye contaminants in water. Different CaO adsorbent doses (0.05, 0.2, 0.4 and 0.6 g) were used, keeping a MB concentration fixed at 10 mg/L. The morphology and crystalline structure of the CFB before and after calcination was characterized via Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses, while the thermal behaviour and surface functionalities were characterised by Thermo Gravimetric Analysis (TGA) and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Adsorption experiments using different doses of CaO synthesized at 900 ℃ for 0.5 h, shwed a MB removal efficiency as high as 98% by weight using  0.4 g(adsorbent)/L(solution). Two different adsorption models, the Langmuir adsorption model and the Freundlich adsorption model along with pseudo-first order and pseudo-second order kinetic models were studied to correlate the adsorption data. The removal of MB via highly ordered CaO adsorption was better modelled by the Langmuir adsorption isotherm giving (R2 =0.93) thus proving a monolayer adsorption mechanism following pseudo-second-order kinetics (R2= 0.98), confirming that chemisorption reaction occurs between MB dye molecule. and CaO.