Search Results (2)

Nanofine zero−valent iron (nZVI) is a new, eco−friendly material with strong reducing and adsorbent properties that can be used to clean up heavy metal−affected soils. Herein, nZVI encapsulated with carboxymethyl cellulose (CMC−nZVI) is synthesized via an aqueous−phase reduction technique and subsequently deployed to evaluate its effectiveness in Cr(VI) soil remediation. The characterization analysis used SEM−EDS, XRD, XPS, and LSV to determine the relevant properties of the material. The results show that at an initial Cr(VI) concentration of 169.5 mg·kg⁻¹, 93.2% of Cr(VI) was removed from the soil after 10 h of treatment with CMC−nZVI at pH 3.3. The kinetic analysis showed that CMC−nZVI had the maximum equilibrium adsorption capacity for removing Cr(VI) from soil at 105.3 mg·g⁻¹. This followed a pseudo−second−order kinetic model. The study shows that CMC−nZVI converts Cr(VI) to Cr(III), which forms complexes with Fe(III) ions in the presence of hydroxide ions (OH⁻) to form a highly stable compound that eventually adsorbs into the nanomaterial’s surface for efficient removal. Full article

Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium carboxymethyl cellulose, CMC) is usually used to minimize aggregation, increase stability, and enhance transport of nZVI. We investigated the stability and dynamic aggregation of bare and CMC–nZVI as affected by variations in pH, ionic strength (IS), and nZVI particle concentration. CMC coating of nZVI resulted in smaller hydrodynamic size and larger zeta potential. The largest hydrodynamic size of nZVI was associated with bare nZVI at high IS (100 mM), pH close to the point of zero charge (PZC, 7.3–7.6), and larger particle concentration (1.0 g L⁻¹). The increase in the zeta potential of CMC–nZVI reached one- to four-fold of that for bare nZVI, and was greater at pH values close to PZC, high IS, and larger particle concentration. The stability of CMC–nZVI was increased by 61.8, 93.1, and 57.5% as compared to that of bare nZVI at IS of 1, 50 and 100 mM, respectively. Calculations of Derjaguin, Landau, Verwey and Overbeek (DLVO) interaction energy were in agreement with stability results, and showed the formation of substantial energy barriers at low IS indicating greater nZVI stability. Our results suggest that at IS above 50 mM and nZVI particle concentration larger than 0.1 g L⁻¹, the likelihood of nZVI aggregation is high. Nevertheless, CMC polymer stabilizer would enhance the stability and transport of nZVI even under these unfavorable solution chemistry conditions. Full article