Sequestering of Radioactive Thorium from Wastewater Using Highly Porous Silica Monoliths

Fabrications of new mesoporous silica adsorbents for radioactive element removal/recovery are of economic and environmental concern. Herein, a mesoporous monolithic cage of phosphonate functionalized silica (MMCS@phosphonate) was synthesized and applied for Th(IV) removal from an aqueous solution. The results demonstrate that Th(IV) adsorption is rapid, and after approximately 90 min the sorption process approaches balance (pH 3.9). The adsorption process can be well described by the Langmuir equation with a maximum sorption capacity of 120 mg/g. Moreover, the adsorption percentage increases with the mass of MMCS@phosphonate until almost complete adsorption (98.05%). Without major modifications of its composition, the mesoporous sorbent was successfully regenerated with nitric acid. Due to the inexpensive cost of silica (as a source of the adsorbent), and higher activity toward thorium ions, the MMCS@phosphonate can be of practical interest for applications in the effective extraction of trace thorium ions from acidic solutions (pH 3.5-3.9).

Automated summary

Fabrications of a new mesoporous silica adsorbent (MMCS@phosphonate) was synthesized and applied for efficient removal of thorium ions from acidic solutions. The adsorption process is rapid and can be well described by the Langmuir equation, with a maximum sorption capacity of 120 mg/g. The mesoporous sorbent can be regenerated with nitric acid and shows potential for practical applications.