In arid and semi-arid regions of the world, agricultural production is greatly limited by water scarcity and inefficient water use. Water absorbent hydrogel is a technological solution that can retain soil water for plants. A lignin-based hydrogel as a natural plant-based water absorbent was prepared from lignin alkali polymers and poly (ethylene glycol) diglycidyl ether (PEGDGE) in adjusted alkali (NaOH) solution. The maximum swelling capacity of the hydrogel was achieved in 1.5 M NaOH with 0.5 mmol PEGDGE glignin--1. Water swelling capacity was 34 g gHydrogel--1 dry weight of hydrogel in distilled water, which reduced to 53 and 64% in 0.1 M NaCl and 0.1 M CaCl2 solution, respectively. Biodegradability and phytotoxicity tests showed that 6.5% of the sample mass decomposed after 40 days of incubation in soil solution media and the hydrogel was not phytotoxic to wheat seeds. These findings support the use of lignin-based hydrogel as an environmentally friendly additive to promote water retention in dry, saline soils. Further assessments are needed due to the limitation of this study in order to understand the efficiency of lignin-based hydrogel application in different soils with different biota.

Keywords