On the potential of pristine Cocos nucifera L. tissues for green desalination

Coconut palm tree (Cocos nucifera L.) tissues were used as a readily available, low-cost and green adsorbent to desalinate seawater. The tree bark (CB), husk (CH), leaves (CL) and roots (CR) were examined in their fresh (F) and dry (D) forms. The salinity removal (adsorption) efficiency followed the trend: F_CB ≈ F_CR > F_CL > D_CR > F_CL > D_CR. The sorbents from the coastal region desalinated more efficiently than those from a non-coastal region. Also, the fresh tissues were more effective and efficient than the dry parts. The salinity retention ability (desalination : desorption) follows the trend: F_CR (22.2) > F_CB (19.0) ≫ D_CR (12.3) > D_CB (11.0) > D_CL (6.14) ≈ F_CL (6.10) > F_CH (4.3) > D_CH (2.1). Moreover, the desalination fitted the pseudo-second-order kinetics than the pseudo-first-order, suggesting the predominance of chemisorption over physical removal. Overall, water pH, conductivity, total dissolved solids and dissolved oxygen (DO) correlated positively and strongly with desalination. By contrast, the density and redox potential correlated negatively, whereas temperature and DO showed no definite influence. Conclusively, F_CR and F_CB are the most suitable coconut palm tree tissues for desalination. Future studies should include chemical characterization of the tissues and system optimization for upscaling. This article is part of the theme issue ‘Developing resilient energy systems’.