Solid-phase synthesis of bi-functionalized porous organic polymer for simultaneous removal of Hg(II) and Pb(II)

Abstract The post-modification has been promoted as an efficient approach to achieve task-specific functionalization, but conventionally consumes huge amounts of solvent, which brings great challenges in environmental risks and energy efficiency. In this work, a bi-functionalized adsorbent is fabricated by a simple yet efficient solid-phase post-modification approach. Through one-pot ball milling at room temperature, 3-mercaptopropyltri-methoxysilane (3-MPTS) and 3-aminopropyltrimethoxysilane (3-APTS) are simultaneously grafted on the polyhydroxy naphthalenediol-based porous organic polymers (NTPOP). The operating conditions are optimized through an orthogonal experiment (L9(34)), which shows superior efficiency that at room temperature by consumption only 1 mL ethanol, it takes 2 h to successfully graft 1 mmol silylation reagent on 1g NTPOP at 300 rpm. The obtained bi-functionalized adsorbent NTPOP-SH-NH2 shows excellent adsorption performance with high Langmuir adsorption capacity of Hg(II) of 357 mg g−1 and Pb(II) of 212 mg g−1, and the second-order rate constant of 0.3003 mg−1 min-l and 0.1687 g mg−1 min-l, respectively. More importantly, in a natural water containing organic compounds and various inorganic salts, NTPOP-SH-NH2 shows strong tolerance with the adsorption performance of Hg(II) and Pb(II) maintains almost unchanged. Furthermore, NTPOP-SH-NH2 exhibits extensive applicability for multi heavy metals ions, such as Hg(II), Pb(II), Cd(II), Cr(III), and Ni(II), that an extremely high removal efficiency of higher than 99% was achieved for each metal ion when they co-exist in the natural aqueous solution. Therefore, this environmentally friendly solid-phase post-modification method provides a promising strategy for the synthesis of bi-functionalized adsorbents with high removal efficiency of heavy metal ions.