Investigation of adsorption and desorption properties of uranyl cations on humic acid immobilized chitosan/PVA composite

Uranium is an important radioactive pollutant in environmental systems such as groundwater, soil and sediment, with an important energy source potential. Although various methods are used to remove of pollutants, adsorption stands out as an inexpensive and easily applicable method. Adsorbents such as clay, natural or synthetic polymers are commonly used to remove metal ions from aqueous solutions. In this study, a novel adsorbent with high affinity for uranyl cation was synthesized from natural biopolymers such as humic acid and chitosan, and adsorption of uranyl cation on this adsorbent was investigated. The study consists of two stages: In the first stage, the humic acid with different proportions was embedded into chitosan/PVA hydrogel matrix, and the synthesized materials were characterized by using various methods such as pH sensitivity, swelling/deswelling behavior, swelling kinetics and diffusion coefficient determination. In the second stage, the equilibrium time, isotherm type and maximum adsorption pH were specified for uranyl adsorption on the 3% (by mass) HA embedded adsorbent. Adsorption capacity of Ch/PVA/HA:3 for uranyl cation was determined as batch test and column capacity and adsorption kinetics were found to be compatible with the pseudo second order kinetic model. In addition, desorption with sodium acetate and sodium nitrate solutions were studied. All results were compared with those of obtained from uranyl adsorption on Ch/PVA. As a result, it was determined that the biopolymeric adsorbent containing 3% (by mass) humic acid inhibited the mobilization of uranyl ions.