Insights into the phosphate adsorption behavior onto 3D self-assembled cellulose/graphene hybrid nanomaterials embedded with bimetallic hydroxides.

ABSTRACT

3D self-assembled cellulose/graphene hybrids (3D cell/GO hybrids) were used as the host for encapsulating the Zr and La hydroxides, forming the Zr/La-cell/GO hybrids. After phosphate adsorption, the crystallization peaks of LaPO4·xH2O in saturated Zr/La-cell/GO hybrids were observed and they were reduced with the increase in pHs. Especially, a low crystallization was observed at pH 10.0 as compared with those at pH 3.0 and 6.0; this also corresponded well to the varied adsorption capacity as a function of pHs. The increased humic acid (HA) amounts (150 mg/L) only resulted in a low capacity loss (16.3%) in phosphate uptake from 25.3 to 21.2 mg/g. A noticeable La leach (2.1 mg/L) was observed at the HA level of 150 mg/L but no Zr leach was detected, and therefore, complexation of La with HA seemed a potential explanation for the increased La leaching. The interference of different coexisting anions on phosphate uptake followed the order as F- > SiO32- > HCO3- > SO42- > NO3- > Cl-. Phosphate uptake by Zr/La-cell/GO hybrids was significantly reduced at the co-existing fluoride partially due to the stronger electro-negativity of fluoride to combine with the protonated Zr/La hydroxides. In addition, Ca2+ laden on the Zr/La-cell/GO hybrids significantly enhanced the adsorption of phosphate by Zr/La-cell/GG hybrids due to the formation of calcium phosphate precipitation in framework of Zr/La-cell/GG hybrids.