Abstract
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 Mössbauer 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.
Highlights
Heavy metal contamination in natural waters, soil, and air is one of the major global concerns because of health hazards
We present a novel method for producing iron sulfide NP-modified carbon microspheres, the determination of their phase composition and surface morphology, and the study of their performance in mercury removal from water
The Fe-to-S ratio of the dried resin was determined on several points of its surface using energydispersive X-ray analysis (EDX), and an average ratio of about 1:1 was obtained. (Note that EDX is a semiquantitative method; Fe-to-S ratios varied between 1.06:1 and 0.93:1; an example is shown in Figure S1 in Supporting Material.) The functional groups of the loaded resin can be described as [– NH?(CH2COO-)2Fe3?(H2O)x]SO42
Summary
Heavy metal contamination in natural waters, soil, and air is one of the major global concerns because of health hazards. Numerous physical and chemical methods have been developed for this purpose to date based on adsorption, precipitation, coagulation, cementation, solvent extraction, reverse osmosis, photoreduction, ion exchange, membrane separation, electrochemical deposition, or a combination of these methods [3, 6, 10,11,12] Among all of these techniques, adsorption is the most commonly used method due to its operational simplicity, removal efficiency, high adsorption rate, and the availability of a wide range of adsorbent materials [12, 13]. Saturating this resin with a trivalent metal cation requires the presence of a counteranion in the matrix for charge balance; we expected that saturation with iron(III) sulfate would provide both the sulfur and iron sources for iron sulfide nanoparticle (NP) formation both in the body and more importantly on the surface of carbon microspheres
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