Super Absorbent Hydrogel Derived from Activated Charcoal Functionalized with Ethylenediamine and Cross-linked with Maleic Acid

Abstract

Superabsorbent hydrogels represent a set of polymeric materials with three-dimensional networks capable of holding a huge amount of water due to their hydrophilic nature in their structure. Their application in industries and the environment is of prime importance. This study reports the synthesis and characterization of superabsorbent hydrogels derived from activated charcoal. The activated charcoal (AC) was functionalized with ethylenediamine (EA) using sodium hydroxide as a catalyst in the absence and presence of maleic acid as a cross linker to synthesize HCE-1 and HCE-2 superabsorbent hydrogel respectively. Characterization of the hydrogels was done using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). The synthesis conditions producing optimal swelling capacity were studied by varying contact time and dosage of both activated carbon and the maleic acid. The results showed presence of C-N- stretching vibration at 1590.99 cm-1 in FT-IR spectrum of HCE-1 indicating interlinking between AC and EA monomers. XRD analysis showed a shift from amorphous to crystalline upon crosslinking. SEM analysis showed dense mast homogenous morphology with clear pores network in HCE-2 compared to the rigid rough surface observed in HCE-1 hydrogel. The dose ratio of AC: EA: maleic acid of 6:5:2 produced hydrogel with highest water absorption capacity of 1089.7±0.6%. Crosslinking the hydrogel with maleic acid was found to improve the water absorption capacity of the absorbent. The study provides a baseline for the application of the hydrogel in agriculture, especially in semi and arid regions.