Adsorption-Desorption of Selenium on Different Nanoscale Waste Materials in Contaminated Water

Different sources of nanomaterials on the adsorption of selenium (Se) in aqueous solutions were evaluated, including nanoscale municipal drinking water treatment residues (nWTRs) and agricultural waste pomegranate peels (PNPs), in comparison with commercial carbon nanoparticles (CNPs). Different Se(IV) treatments and application doses of each nanomaterial were evaluated. The Se adsorption kinetics were determined at different time intervals. The results showed that the Se sorption capacity of different nanomaterials and their mixtures varied significantly (p < 0.05). Se concentration, the application dosage of nanoparticles, and the interaction time of Se and nanoparticles in Se solutions significantly affect the efficiency of Se adsorption at pH 3.51. The sorption isotherm of Se varied amongst different nanomaterials. Se adsorption on CNPs, nWTRs-CNPs, nWTRs, PNPs-CNPs, nWTRs-PNPs, and PNPs at the 800 mg Se/L treatment was 79.93, 77.48, 76.00, 72.97, 70.49, and 68.16 mg Se/g sorbent, respectively. The H-type isotherm became dominant, indicating intensive interaction between Se and nanoparticles. With the Se treatment of 50 mg/L, the Se removal efficiency of CNPs, nWTRs-CNPs, nWTRs, PNPs-CNPs, nWTRs-PNPs, and PNPs was 100, 96, 93, 87, 85, and 80%, respectively, but became 100, 97, 95, 91, 88, and 85%, respectively, at a higher Se concentration of 800 mg/L. Increasing the application dosage of nanomaterials resulted in a significant increase in Se mass sorbed by the nanoparticles. Se adsorption was best predicted by the Langmuir isotherm model. The desorption rate of the Se mass sorbed by nanoparticles at 800 mg Se/L was 0.4% of the total Se adsorbed by CNPs, with 0.88% by nWTRs-CNPs and 1.69% by PNPs-CNPs, while higher Se desorption rates of 4.2, 7.3, and 17.6% were observed with nWTRs, nWTRs-PNPs, and PNPs, respectively. This study demonstrates that nanoscale municipal and agricultural solid waste materials can be effective in removing Se from contaminated water.