SYNTHESIS OF HYDROGELS AND ADSORPTION/DESORPTION KINETICS OF UREA**

Hydrogels, natural or synthetic polymers, that are being used in medicine and agriculture also find their applications in environmental chemistry and engineering. The superior characteristics of hydrogels, including high capacity of water retention and adsorption of solutes, make hydrogels promising for recovery of nutrients from aqueous solutions. As valuable nutrients are being lost to environment to cause pollution, the recovery or recycle of the nutrients from their sources can be achieved by utilizing the hydrogels properties. Cellulose-base and acrylamide-base hydrogels were synthesized and characterized for their chemical structures and functional groups using TFIR spectroscopy, and further tested for swelling behavior and the adsorption and desorption capabilities by evaluating the concentration of urea using a TOC/TN instrument and mass balance. This study focuses also on their kinetic behavior both in adsorption and desorption of urea from an aqueous solution, which simulates the urea uptake from human urine and the release to a solution for recycling. Preliminary results show higher swelling capacity of acrylamide-base hydrogels than cellulose-base counterpart (188 +/- 54 % vs 22 +/- 1.0 %) and higher adsorption and desorption as well (19.1 mg N/g hydrogel vs 9.0 mg N/g, 11.0 mg N/L solution vs 4.1 mg N/L, respectively). Isotherm tests and kinetic studies are being conducted to elucidate the correlation among the chemical structures, the hydrogels’ performance and the effect of crosslinking agents. The synthesis of more environmentally friendly hydrogels are also being studied by employing other monomers and cross-linkers, and the production of more efficient adsorbent/desorbent will follow by adopting novel synthetic strategies involving hybrid-copolymers and UV initiated polymerization. The outcome of this study is expected to contribute to reuse of nutrients and reduction of the load of water treatment