Preparation of modified pomelo peel's pulp adsorbent and its adsorption to uranyl ions

Using pomelo peel's pulp (PPP) as raw material, a new chemically modified PPP was prepared by the process of fermentation, cooking, freeze-drying, and so on. The adsorbent has been characterized by EDS, IR, BET and SEM. The factors of different adsorption conditions such as pH value, adsorption temperature, mass of adsorbent, adsorption time and initial concentration of UO₂ ²⁺ were investigated. The adsorption mechanism was explored by adsorption thermodynamics and kinetics experiments. The results indicate that the pH value is 6.0, the dosage of adsorbent is 500 mg l^-1, the temperature is 50°C and the adsorption time is 90 min, which is the best adsorption condition. When the initial concentration of UO₂ ²⁺ is 35 mg l^-1, the adsorbed amount of uranyl ions by the modified PPP adsorbent can reach 42.733 mg g^-1, 26.8% higher than the adsorption amount of unmodified adsorbent (31.276 mg g^-1), which is obviously enhanced. The kinetic and thermodynamic experiments show that the adsorption process is in good agreement with the pseudo second-order kinetics model, that it is an endothermic reaction, and the reaction is spontaneous. The adsorption process is entropy-dominated. The Freundlich adsorption isotherm can describe the adsorption process more accurately.