Synthesis of a new thiophenol-thiophene polymer for the removal of mercury from wastewater and liquid hydrocarbons

This work reports the synthesis of a novel thiophenol-thiophene polymer (termed KFUPM-Hg) and its suitability as an adsorbent for mercury removal from wastewater and liquid hydrocarbons. KFUPM-Hg was synthesized through a Friedel-Crafts polycondensation reaction of thiophenol and thiophene in the presence of p-formaldehyde as a linker. The crosslinked polymer structure was characterized using solid-state ¹³C-nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR). Thermogravimetric analysis was performed to assess the polymer thermal stability, which indicated that the polymer is thermally stable to over 300 °C. A series of batch adsorption studies were used to investigate the effects of different parameters (pH, temperature, concentration, and time) on the mercury removal from aqueous solution as well as from a model liquid hydrocarbon media (decane/toluene mixture). The batch adsorption studies in aqueous media showed near quantitative removal of inorganic mercury (II) at 100 ppm using the thiophenol-thiophene polymer adsorbent. Furthermore, the thiophenol-thiophene polymer demonstrated excellent removal capabilities of methylmercury in a decane/toluene hydrocarbon mixture. Mercury adsorption onto KFUPM-Hg is an exothermic reversible physical process and follows pseudo-second order adsorption kinetics. Remarkably, these removal capabilities were achieved using polymers that directly incorporated thiophenol and thiophene groups during synthesis without the use of thiol-ene post-synthesis modifications.