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

In this study, the thiophenyl polyamide ( TPPA ) derived from tri(4-aminophenyl) benzene was synthesized for the removal of Hg 2+ 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 Hg 2+ 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 Hg 2+ , (ii) the stability in the pH values ranging between 2 and 6, and (iii) the proper recyclability (87 % of Hg 2+ 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 Hg 2+ 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.