Surface functionalized Casuarina equisetifolia pine powder for the removal of hetero-polyaromatic dye: characteristics and adsorption

ABSTRACT

The seed of Casuarina equisetifolia, the genus of Pinus of the family Pinaceae was examined for the potentiality of adsorbing a thiazine-based hetero-polyaromatic dye from water system. For which, the surface functionalization of Casuarina equisetifolia(SFCE) was achieved through H₂SO₄ acidic bath to treat methylene blue (MB) dye contaminated water. The SFCE was characterised using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) to analyse morphological, physical and chemical behaviour after surface modification. The effects of adsorption process influencing variables such as pH, concentration of MB dye, contact time and temperature was examined. The maximum adsorption capacity of 0.5 gL⁻¹ SFCE for the concentration ranging from 20 to 100 mgL⁻¹ of MB was investigated using different variables. The effect of parameters including pH, time and temperature were optimised at a speed of agitation of 150 rpm. The adsorption data retrieved from batch experiments were fit with Langmuir, Freundlich, Temkin and Dubinin-Raduskevich (D-R) isotherm models, and as a result, Freundlich presents the best fit (R² > 0.97). Pseudo-second order kinetic was superior indicating that SFCE-MB system has undergone the chemisorption mechanism (R² > 0.99) spontaneously. Overall, the tested system with synergistic effect was witnessed with maximum adsorption efficiency of 42.19 mg g⁻¹ to remove dye from industrial wastewater.

KEYWORDS:

• Casuarina equisetifolia
• acid bath
• adsorbent
• methylene blue
• removal

Acknowledgments

The authors are grateful to Director, CSIR-CSMCRI, Bhavnagar for the infrastructure provided and technical staff members of AESD & CIF, CSIR-CSMCRI for the analytical support. The manuscript has been assigned CSIR-CSMCRI: 09/2020 registration.

Disclosure statement

The authors declare that they have no known conflicts of interests.