A novel mesoporous silica with enhanced phosphonic functional groups (PFGs) and without any silane agents was provided by Sol-Gel technique for selective adsorption of U(VI) from aqueous solutions (AqS). The absorbent was synthesized based on the achieving the four best performance characteristics including availability, economically, adsorption efficiency, and selectivity which are undoubtedly defined the usefulness of the adsorbents. The sorption results exhibited the highest uranium adsorption capacity, qe, of 820.7 mg/g at pH ≈ 8 which indicated the adsorbent is the best alternative for uranium adsorption from the nearly neutral solutions such as seawater. The recovery percentages by the adsorbent in the aqueous environments involving other elements such as Mg, Cd, Hg, As, Ca, Na, Ni and the salty environment with high concentration of Cl- ions are indicated that the adsorbent presents the acceptable selectivity for uranium adsorption from the AqS such as industrial wastewater. Several activities and factors including removing the silane agents, using sodium metasilicate as an available and low-cost source of silica, and using the Sol-gel method as an unexpansive synthesis technique caused to reduce the synthesis costs from 222.787 EUR/kg for the template method to 60.078 EUR/kg for Sol-gel method which confirm the synthesis of a cost-effective adsorbent.