Synthesis of adipic acid dihydrazide-decorated coco peat powder-based superabsorbent for controlled release of soil nutrients

Superabsorbent composites based on agricultural byproducts represent a promising strategy for recycling exploitable waste resources and relieving environmental stress, but their development is usually hindered, because the traditional pretreatment technology for lignocellulosic raw materials is intricate and time-consuming, and always generates pollution-causing effluents. In this research, we firstly employ adipic acid dihydrazide as an outstanding decorating substrate for the pretreatment of CP, and then synthesize a novel superabsorbent (MA-CP@ADH-g-PAA) through grafting poly(acrylic acid) onto an MA-modified CP@ADH surface. Compared with conventional acid and alkali pretreatment approaches, CP@ADH, without the need for any harsh reaction conditions or complex equipment, has avoided possible pollution during the process and simultaneously introduced plenty of amine groups onto the inert CP surface. The CP@ADH had a higher degree of substitution than that of pristine CP, and the grafting efficiency reached 75.2%. The swelling equilibrium of the MA-CP@ADH-g-PAA reached about 470.02 g g−1 in distilled water, and the swelling behavior under load and load-free both fitted well with the pseudo-second-order model. Owing to their excellent water absorbing and holding capacity, and slow release behavior of soil nutrients, it is believed that the MA-CP@ADH-g-PAA superabsorbent product could have potential industrial applications, especially in agricultural and horticultural usage.