Adsorption of PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) using a carbonised Mn-based metal–organic framework

Abstract

Metal–organic frameworks (MOFs) are adsorbents suitable for water treatment. However, they are often water soluble and poorly processible, limiting their industrial applications. This study aims to develop a carbonized MOFs with high adsorption performance based on MOFs. Here, we report the production of Mn-MOF [Mn(DMF)2(H2DHTPA)]n (where DMF is N,N-dimethylformamide and H4DHTPA is 2,5-dihydroxyterephthalic acid) via a solvothermal method. This MOF shows good adsorption performance for various ions but dissolves easily in water. However, Mn-MOF-500 which was obtained by carbonising Mn-MOF at 500 °C shows high water stability. Thus, the adsorption properties of Mn-MOF-500 were investigated, revealing adsorption capacities for PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) of 126.66, 88.46, 356.21, 146.92, 51.28, and 166.10 mg/g, respectively. Based on the adsorption isotherms and the adsorption kinetics, the adsorption of PO43-, Cd(II), and As(III) occurs via monolayer chemisorption, whereas that of Pb(II), Cu(II), and As(V) occurs via monolayer chemisorption and physisorption in pores. X-ray diffractometry and X-ray photoelectron spectroscopy analysis showed that P, Cd(II), Pb(II), Cu(II), As(III), and As(V) were adsorbed on Mn-MOF-500 as PO43-, Cd(OH)2, PbO and Pb(OH)2, Cu(OH)2, Mn3(AsO3)2, and MnHAsO4, respectively.

Keywords

• Mn-MOF-500
• Adsorption
• PO43-
• Heavy metal ions