Facile fabrication of La/Ca bimetal-organic frameworks for economical and efficient remove phosphorus from water

Abstract

In this study, low-cost and water-stable La/Ca bimetallic organic framework (La/Ca-BDC) are synthesized and used for the efficient removal of phosphorus in water. The study of adsorption isotherms shows that the high concentration of Ca in La/Ca-BDC-1 (prepared with Ca molar fraction in the precursor as high as 50%) has little interference to the phosphorous adsorption capacity (66.0 mg g−1) compared with that of the La-BDC (71.0 mg g−1), or only 7.0% drop, but it translates to significantly reduced cost of phosphorus removal by about 40.0%. The kinetic study of phosphorus removal process using the synthesized La/Ca-BDC-n conforms to the pseudo-second-order kinetic model. In addition, the synthesized La/Ca-BDC-1 is suitable for phosphorus removal in wide pH water (3.0–9.0). More importantly, the manufactured La/Ca-BDC-1 can efficiently remove the phosphorus in the actual water. In addition, even if there are interfering ions (Ca2+, Mg2+, CO32–, HCO3–, SO42- and Cl-) with concentration of five times of the phosphorus, the phosphorus removal efficiency of La/Ca-BDC-1is hardly affected. Interestingly, the removal efficiency of La/Ca-BDC-1 for phosphorus is still higher than 70% after five cycles. From the FT-IR and XPS analysis, it is shown that ligand exchange and complexation are the main phosphorus removal mechanisms of La/Ca-BDC-1.