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Title: | Nanoscale zero-valent iron for metal/metalloid removal from model hydraulic fracturing wastewater | Authors: | Sun, Y Lei, C Khan, E Chen, SS Tsang, DCW Ok, YS Lin, D Feng, Y Li, XD |
Issue Date: | Jun-2017 | Source: | Chemosphere, June 2017, v. 176, p. 315-323 | Abstract: | Nanoscale zero-valent iron (nZVI) was tested for the removal of Cu(II), Zn(II), Cr(VI), and As(V) in model saline wastewaters from hydraulic fracturing. Increasing ionic strength (I) from 0.35 to 4.10 M (Day-1 to Day-90 wastewaters) increased Cu(II) removal (25.4–80.0%), inhibited Zn(II) removal (58.7–42.9%), slightly increased and then reduced Cr(VI) removal (65.7–44.1%), and almost unaffected As(V) removal (66.7–75.1%) by 8-h reaction with nZVI at 1–2 g L−1. The removal kinetics conformed to pseudo-second-order model, and increasing I decreased the surface area-normalized rate coefficient (ksa) of Cu(II) and Cr(VI), probably because agglomeration of nZVI in saline wastewaters restricted diffusion of metal(loid)s to active surface sites. Increasing I induced severe Fe dissolution from 0.37 to 0.77% in DIW to 4.87–13.0% in Day-90 wastewater; and Fe dissolution showed a significant positive correlation with Cu(II) removal. With surface stabilization by alginate and polyvinyl alcohol, the performance of entrapped nZVI in Day-90 wastewater was improved for Zn(II) and Cr(VI), and Fe dissolution was restrained (3.20–7.36%). The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in removal trends from Day-1 to Day-90 wastewaters was attributed to: (i) distinctive removal mechanisms of Cu(II) and Cr(VI) (adsorption, (co-)precipitation, and reduction), compared to Zn(II) (adsorption) and As(V) (bidentate inner-sphere complexation); and (ii) changes in solution speciation (e.g., from Zn2+ to ZnCl3− and ZnCl42−; from CrO42− to CaCrO4 complex). Bare nZVI was susceptible to variations in wastewater chemistry while entrapped nZVI was more stable and environmentally benign, which could be used to remove metals/metalloids before subsequent treatment for reuse/disposal. | Keywords: | Alginate entrapment Hydraulic fracturing Metals/metalloids Nanoscale zero-valent iron Salinity Wastewater treatment |
Publisher: | Pergamon Press | Journal: | Chemosphere | ISSN: | 0045-6535 | EISSN: | 1879-1298 | DOI: | 10.1016/j.chemosphere.2017.02.119 | Rights: | © 2017 Elsevier Ltd. All rights reserved. © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/ The following publication Sun, Y., Lei, C., Khan, E., Chen, S. S., Tsang, D. C., Ok, Y. S., ... & Li, X. D. (2017). Nanoscale zero-valent iron for metal/metalloid removal from model hydraulic fracturing wastewater. Chemosphere, 176, 315-323. is available at https://doi.org/10.1016/j.chemosphere.2017.02.119. |
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