Effect of cross-linking degree on uranyl ions adsorption using TBP-impregnated styrene-divinylbenzene resin in nitric acid and hydrochloric acid

This study evaluates the adsorption performance of tributyl phosphate-impregnated styrene-divinylbenzene-silica (TBP-STY-DVB-SiO2) resins with varying tributyl phosphate (TBP) contents and cross-linking (CL) degrees for uranyl ion recovery in acidic media. Batch adsorption experiments conducted in 0.1–9 M nitric acid (HNO3) and hydrochloric acid (HCl) revealed that both TBP content and CL degree significantly influence uranium uptake. The resin containing 23.08% TBP and 50% CL degree exhibited the highest distribution coefficient (Kd), achieving optimal performance at 5 M HNO3 and 9 M HCl. Lower CL degree enhanced diffusion but compromised structural stability, while higher CL degree restricted accessibility to active sites. The 50% CL degree resin provided the best balance between mechanical strength and functional accessibility. This work presents the first systematic evaluation of CL degree and TBP content effects on uranyl adsorption by TBP-STY-DVB-SiO2 resins, offering new insights into extractant resin design for efficient uranium recovery from highly acidic solutions.