Department of Civil and Environmental Engineering , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States.
Center for Environmental Implications of NanoTechnology , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States.
Environ Sci Technol. 2019 May 21;53(10):5936-5945. doi: 10.1021/acs.est.9b00511. Epub 2019 May 6.
Sulfidized nanoscale zerovalent iron (SNZVI) has desirable properties for in situ groundwater remediation. However, there is limited understanding of how the sulfidation type and particle properties affect the reactivity and selectivity of SNZVI toward groundwater contaminants, or how reactivity changes as the particles age. Here, SNZVI synthesized by either a one-step (SNZVI-1) or two-step (SNZVI-2) process were characterized, and the reactivity of both fresh and aged (1d to 60 d) nanoparticles was assessed. The measured S/Fe ratio was 5.4 ± 0.5 mol % for SNZVI-1 and 0.8 ± 0.1 mol % for SNZVI-2. XPS analysis indicates S, S, and S species on the surface of both SNZVI-1 and SNZVI-2, while S is the dominant species inside of the SNZVI nanoparticles. SNZVI-1 particles were hydrophobic (contact angle = 103 ± 3°), while the other materials were hydrophilic (contact angles were 18 ± 2° and 36 ± 3° for NZVI and SNZVI-2, respectively). SNZVI-1, with greater S content and hydrophobicity, was less reactive with water than either NZVI or SNZVI-2 over a 60 d period, resulting in less H evolution. It also had the highest reactivity with TCE and the lowest reactivity with nitrate, consistent with its higher hydrophobicity. In contrast, both NZVI and SNZVI-2 were reactive with both TCE and nitrate. Both types of SNZVI remained more reactive after aging in water over 60 d than NZVI. These data suggest that the properties of the SNZVI made from a one-step synthesis procedure may provide better reactivity, selectivity, and longevity than that made from a two-step process.
硫化纳米零价铁（SNZVI）具有原位地下水修复的理想特性。然而，对于硫化类型和颗粒性质如何影响 SNZVI 对地下水污染物的反应性和选择性，以及随着颗粒老化反应性如何变化，人们的了解有限。在此，通过一步（SNZVI-1）或两步（SNZVI-2）工艺合成的 SNZVI 进行了表征，并评估了新鲜和老化（1 天至 60 天）纳米颗粒的反应性。SNZVI-1 的测量 S/Fe 比为 5.4±0.5mol%，SNZVI-2 的测量 S/Fe 比为 0.8±0.1mol%。XPS 分析表明，SNZVI-1 和 SNZVI-2 的表面均存在 S、S 和 S 物种，而 SNZVI 纳米颗粒内部的主要物种是 S。SNZVI-1 颗粒是疏水性的（接触角=103±3°），而其他材料是亲水性的（NZVI 和 SNZVI-2 的接触角分别为 18±2°和 36±3°）。SNZVI-1 具有更高的 S 含量和疏水性，与水的反应性比 NZVI 或 SNZVI-2 都低，在 60 天内导致 H 演化减少。它对 TCE 的反应性最高，对硝酸盐的反应性最低，这与其较高的疏水性一致。相比之下，NZVI 和 SNZVI-2 都与 TCE 和硝酸盐反应。在 60 天的水老化后，两种类型的 SNZVI 的反应性都比 NZVI 高。这些数据表明，与两步法合成的 SNZVI 相比，一步法合成的 SNZVI 具有更好的反应性、选择性和耐久性。
