Carbon microspheres decorated with iron sulfide nanoparticles for mercury(II) removal from water

A new and simple method is developed to synthesize carbon microspheres decorated with iron sulfide nanoparticles for mercury ion removal from water. The synthesis is based on carbonizing polystyrene–divinylbenzene-based and iron(III) sulfate-loaded cation exchange resins between 500 and 1000 °C. The phase composition, surface area, and morphology of these materials are characterized by various spectroscopic and diffraction techniques, including Mossbauer spectroscopy, powder X-ray diffraction, Raman and scanning electron microscopy, and BET analysis. Pyrrhotite is found to be the dominant iron-containing phase. The adsorption performance of microspheres for mercury ion removal from water is studied as a function of adsorbent load and contact time at pH 6.5 using a solution of 40 mg dm−3 mercury ion. Pyrrhotite nanoparticles played a key role in mercury ion removal amounting to 70–90% of the extracted amount. A high adsorption capacity of 104 mg of mercury/g of adsorbent at an adsorbent load of 0.33 g dm−3 is achieved, and the removal kinetics could be well fitted with a pseudo-second-order kinetic model, indicating chemical sorption. The synthetic method is easy to scale up for large-scale production and materials are easy to handle, which is significant for large-scale environmental applications.