A Novel Method to Produce Cost Effective, Environment Friendly Superabsorbent from Eichhornia crassipes for Improved Water Retention in Soil

Eichhornia crassipes is considered the worst aquatic weed in the world as it has become a serious threat to the environment and biodiversity hence eco-friendly utilization of this hydrophyte is needed and important. Enhancement of agricultural production to cater for increased food demand is a global challenge which is aggravated by climate change and scarcity of water. Superabsorbent materials have been developed to improve water retention in soil but majority of superabsorbent are synthetic based and non-biodegradable. Therefore, this study is aimed at developing an eco-friendly superabsorbent from E. crassipes in a cost-effective manner and assess its efficacy on improved water retention in soil. E. crassipes was collected from tank nearby Faculty of Applied Sciences, Wayamba University of Sri Lanka and petiole was treated with potassium hydroxide (KOH) followed by microwave irradiation in which reaction conditions were optimized to obtain maximum water absorption and swelling capacity. Prepared superabsorbent was characterized using Fourier Transform Infrared Spectroscopy (FTIR), XRD and scanning electron microscopy (SEM) techniques. Efficacy of the superabsorbent on improved water retention was assessed using normal loam soil. The superabsorbent showed a maximum swelling index of 1276% at KOH concentration of 0.1 moles/l which is attributed to highly porous structure, presence of hydrophilic functional groups in cellulose and hemicellulose, increased number of surface hydrophilic functional groups during the KOH activation process and carboxymethyl cellulose created during microwave irradiation. Water absorption capacity of the superabsorbent is greatly influenced by KOH concentration, reaction time, microwave power and exposure time. Water retention studies in soil showed that superabsorbent has capacity to retain water for 27 days with a slow rate of water evaporation whereas soil samples without superabsorbent showed a high rate of water evaporation retaining water only for 15 days. Findings of this study disclose an innovative method for development of an eco-friendly superabsorbent from E. crassipes in a cost-effective manner excluding toxic chemical reagents which can be used for improved water retention in soil effectively for climate change resilient sustainable agriculture.