Thiophene network polyamides (TPPA) with tri(4-aminophenyl)benzene: Synthesis and removal of Hg2+ from aqueous solution

Abstract

In this study, the thiophenyl polyamide (TPPA) derived from tri(4-aminophenyl) benzene was synthesized for the removal of Hg2+ from the aqueous solution. The adsorbent was characterized by the Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption, thermogravimetric analysis and differential scanning calorimetry. The adsorption capacity of Hg2+ is 518.7 mg g−1 at a dose of 1.1 g/L of adsorbent. TPPA was shown to have the following advantages: (i) the high selectivity for the excess metal ions Hg2+, (ii) the stability in the pH values ranging between 2 and 6, and (iii) the proper recyclability (87 % of Hg2+ can be removed in 5 adsorption–desorption cycles). Our analysis suggests the models of the pseudo-second-order kinetics and the Langmuir isotherm are suitable for the description of the adsorption of Hg2+ on the thiophene network polyamide. Our experimental and theoretical results reveal the relationship between the structures and the adsorption capacities of TPPA, identifying the oxygen atom (amide) and the sulphur atom (thiophene) as the most important chemical-reaction sites.