Zinc sulfide (ZnS) nanomaterials have shown strong promise in the removal of elemental mercury (Hg⁰) from industrial flue gas, particularly in high-temperature environments typical of non-ferrous metal smelting. This study presents a comprehensive strategy for optimizing ZnS-based sorbents by addressing the fundamental trade-off between surface area and sulfur site reactivity—two key determinants of adsorption performance. By synthesizing ZnS at different hydrothermal temperatures (80°C, 120°C, and 160°C), researchers systematically investigated how crystal structure evolution influences both physical and chemical properties, ultimately guiding the design of high-performance materials.
X-ray diffraction (XRD) analysis revealed that low-temperature synthesis (80–120°C) yielded wurtzite-phase ZnS with high structural disorder, while increasing temperature promoted a phase transformation to sphalerite in 160-ZnS. This transition was accompanied by significant changes in morphology and crystallinity. BET surface area measurements showed a sharp decline—from 144.35 m²/g for 80-ZnS to just 20.69 m²/g for 160-ZnS—due to enhanced crystal growth and reduced nucleation. SEM and TEM images confirmed this trend: 80-ZnS and 120-ZnS exhibited amorphous aggregates with high surface roughness, whereas 160-ZnS formed well-defined microspheres with smooth, crystalline facets. High-resolution TEM and SAED patterns further confirmed the polycrystalline nature of lower-temperature samples versus the monocrystalline structure of 160-ZnS, indicating improved lattice integrity at higher temperatures.
The critical breakthrough came from analyzing sulfur speciation using XPS and Raman spectroscopy. While all samples contained S²⁻, S₂²⁻, and polysulfur (Sₓ), the molecular form of Sₓ differed significantly. In 80-ZnS and 120-ZnS, Sₓ existed predominantly as long-chain polysulfur (L-Sₓ), identified by a Raman peak at 257 cm⁻¹. In contrast, 160-ZnS displayed a dominant peak at 449 cm⁻¹, characteristic of short-chain polysulfur (S-Sₓ). This transformation, driven by thermal cleavage of sulfur chains, is pivotal: L-Sₓ exhibits negligible Hg⁰ adsorption ability, whereas S-Sₓ shows high affinity due to its reactive terminal sulfur atoms.
Adsorption experiments conducted at 180°C demonstrated that although 80-ZnS and 120-ZnS achieved superior overall Hg⁰ removal efficiency (~90%) due to their large surface areas, 160-ZnS exhibited a much higher adsorption capacity per unit surface area (CA,ad)—nearly double that of the others. This indicates that despite fewer exposed sites, each active site on 160-ZnS is far more reactive. Hg-TPD profiles supported this: while 80-ZnS and 120-ZnS released only -HgS (desorption peak ~375–384°C), 160-ZnS produced both -HgS (299°C) and -HgS (378°C), confirming dual reaction pathways involving S₂²⁻ and S-Sₓ.
Quantitative analysis of CA,ad values revealed that S₂²⁻ sites contributed similarly across samples (~0.36 g·m⁻²), but S-Sₓ sites on 160-ZnS reached 0.44 g·m⁻²—significantly higher than the 0.23 g·m⁻² observed for Sₓ sites in lower-temperature samples. This confirms that the catalytic enhancement at high temperature stems not from increased site density but from the formation of highly reactive S-Sₓ species.129-46-4 IUPAC Name
The proposed mechanism involves initial physisorption of Hg⁰ followed by chemisorption on S₂²⁻ and S-Sₓ sites:
Hg⁰(g) + surface → Hg⁰(ad)
Hg⁰(ad) + S₂²⁻ → –HgS(ad) + S₂²⁻
Hg⁰(ad) + S–Sₓ → –HgS(ad) + S–Sₓ⁻¹
This work establishes that optimal Hg⁰ capture requires balancing high surface area with the presence of reactive S-Sₓ sites.FGG Antibody Protocol To achieve this, future strategies should focus on developing synthesis methods—such as controlled capping agents, templated growth, or post-synthesis activation—that preserve high surface area while stabilizing short-chain polysulfur structures.PMID:35196696 Such approaches will enable the design of next-generation ZnS sorbents capable of efficient, stable, and regenerable mercury capture under real industrial conditions, advancing practical implementation in emission control systems.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
