Eco-friendly fabrication of coco coir composites for hydroponic cultivation: a green chemistry approach

Abstract

In this study, we report an eco-friendly biocomposite fabrication process for valorizing coconut fibers (coco coir) by transforming them into multi-purpose biocomposites using a pectin-based one-pot aqueous process. In our green approach, we used high methoxyl pectin (degree of methoxylation: 74%) as a crosslinker for binding lignin present in coco coir under basic conditions via the transesterification reaction. The fabrication process was performed at a moderate reaction temperature (70 °C) with water as the only solvent. We conducted statistical analysis to determine the impact of different mass ratios of pectin to coco coir (1 : 5, 2 : 5, 3 : 5, 4 : 5, and 5 : 5) on the mechanical compressive strength and bulk density of the as-fabricated coco coir composite materials. As this mass ratio increased from 1 : 5 to 5 : 5, the compressive strength of the coco coir composites increased by 3 times and the bulk density increased by ca. 1.3 times. The measurements of electrical conductivity, water retention capacity, carbon-to-nitrogen ratio (C/N), and substrate acidity (pH) of these coco coir biocomposites revealed the applicability of these biocomposites as suitable growth substrates for hydroponic cultivation. These biocomposite substrates were applied to grow Daikon radish in a hydroponic system for a 30-day study to demonstrate their potential for hydroponic cultivation.