One-Pot Synthesis of Layered Disodium Zirconium Phosphate: Crystal Structure and Application in the Remediation of Heavy-Metal-Contaminated Wastewater

摘要

Inorganic ion exchangers offer advantages whenever operation at high temperatures or in oxidizing environments is required. A novel two-dimensional disodium zirconium phosphate, Zr(NaPO4)(2)center dot H2O, was reported and investigated as an ion exchanger for heavy metals. The material was synthesized by a novel minimalistic solventless approach, and its solid-state structure was determined from powder X-ray diffraction data. Zr(NaPO4)(2)center dot H2O crystallizes in the space group P2(1)/c with cell parameters a = 8.7584(1) angstrom, b = 5.3543(1) angstrom, c = 18.1684(3) angstrom, beta = 109.053 (1)degrees, and Z = 4. Its layered structure is similar to that of a-zirconium phosphate, Zr(NaPO4)(2)center dot H2O. However, unlike a-zirconium phosphate which is limited in practical applications by its narrow interlayer spacing (d = 7.6 angstrom), the disodium zirconium phosphate has a larger spacing of 8.6 angstrom between planes. The material with inherent structural advantages displays excellent sorption for heavy metals such as Pb2+, Cu2+, Cd2+, and Tl+, maintaining its high selectivity with distribution coefficients, K-d, of 10(4)-10(5) mL/g even in the presence of a large excess of Na+, K+ , Mg2+, and Ca2+, which are commonly present in underground water. In particular, the maximum sorption capacity for the highly toxic Tl+ is a record high, 5.07 mmol/g (1036 mg/g). The fast reaction kinetics indicate that the exchangeable positions in Zr(NaPO4)(2)center dot H2O are readily accessible, in contrast to Zr(NaPO4)(2)center dot H2O. The ease of preparation, benign nature, and advantageous ion-exchange properties make Zr(NaPO4)(2)center dot H2O a highly promising sorbent for the treatment of water polluted with heavy metals.