Super water absorbing polymeric gel from chitosan, citric acid and urea: Synthesis and mechanism of water absorption

•The hydrothermal synthesis of a new super water absorbent from chitosan, citric acid and urea is reported.•The maximum absorption capacity of the material was ∼ 1250 g/g of distilled water and ∼ 210 g/g of 0.1 % NaCl solution.•The high water absorption arises out of a combination of physical crosslinks consisting of electrovalent bonds and morphology.•The material, even in low quantity, delayed the evaporation of water in soil and can be used for controlled release of water. A new superabsorbent with maximum water absorption capacity of ∼1250 g/g is prepared by hydrothermal synthesis from sustainable and biodegradable resources such as chitosan, citric acid and urea (denoted as ‘CHCAUR’). CHCAUR is characterized extensively by various analytical techniques such as PXRD, SSNMR, FTIR, and TGA. Pure and saline water absorption study showed that CHCAUR could be a better adsorbent compared to the super absorbent polymer (SAP) used in commercial diaper material. The mechanism of water absorption is shown to arise out of a combination of electrostatic attraction of water to the ionic crosslinks and the presence of macropores as well as undulated surface due to the formation of nanofibrous bundles. When applied to soil CHCAUR was found to decrease water evaporation rate significantly.