Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines
The underutilized cement-rich fine fraction of concrete-based demolition waste is a potential sorbent for aqueous metal ion contaminants. In this study, crushed concrete fines (CCF) were found to exclude 33.9 mg g<sup>−1</sup> of Cr<sup>3+</sup>, 35.8 mg g<sup>−1</su...
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MDPI AG
2022-05-01
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| Online Access: | https://www.mdpi.com/2073-4352/12/5/717 |
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| author | Andrew P. Hurt Aimee A. Coleman Nichola J. Coleman |
| author_facet | Andrew P. Hurt Aimee A. Coleman Nichola J. Coleman |
| author_sort | Andrew P. Hurt |
| collection | DOAJ |
| description | The underutilized cement-rich fine fraction of concrete-based demolition waste is a potential sorbent for aqueous metal ion contaminants. In this study, crushed concrete fines (CCF) were found to exclude 33.9 mg g<sup>−1</sup> of Cr<sup>3+</sup>, 35.8 mg g<sup>−1</sup> of Ni<sup>2+</sup>, and 7.16 mg g<sup>−1</sup> of Sr<sup>2+</sup> from ~1000 ppm single metal nitrate solutions (CCF:solution 25 mg cm<sup>−3</sup>) under static batch conditions at 20 °C after 3 weeks. The removal of Sr<sup>2+</sup> followed a pseudo-second-order reaction (k<sub>2</sub> = 3.1 × 10<sup>−4</sup> g mg<sup>−1</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.999), whereas a pseudo-first-order model described the removal of Cr<sup>3+</sup> (k<sub>1</sub> = 2.3 × 10<sup>−4</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.998) and Ni<sup>2+</sup> (k<sub>1</sub> = 5.7 × 10<sup>−4</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.991). In all cases, the principal mechanism of interaction was the alkali-mediated precipitation of solubility-limiting phases on the surface of the CCF. Four consecutive deionized water leaching procedures (CCF:water 0.1 g cm<sup>−3</sup>) liberated 0.53%, 0.88%, and 8.39% of the bound Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> species, respectively. These findings indicate that CCF are an effective sorbent for the immobilization and retention of aqueous Cr<sup>3+</sup> and Ni<sup>2+</sup> ions, although they are comparatively ineffectual in the removal and sustained exclusion of Sr<sup>2+</sup> ions. As is commonly noted with Portland cement-based sorbents, slow removal kinetics, long equilibrium times, the associated release of Ca<sup>2+</sup> ions, high pH, and the formation of loose floc may preclude these materials from conventional wastewater treatments. This notwithstanding, they are potentially suitable for incorporation into permeable reactive barriers for the containment of metal species in contaminated groundwaters, sediments, and soils. |
| first_indexed | 2024-03-10T03:05:10Z |
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| spelling | doaj.art-cad8a57913c64c08992e3435848c60a62023-11-23T10:36:00ZengMDPI AGCrystals2073-43522022-05-0112571710.3390/cryst12050717Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete FinesAndrew P. Hurt0Aimee A. Coleman1Nichola J. Coleman2School of Science, Faculty of Engineering and Science, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UKHH Wills Physics Laboratory, School of Physics, University of Bristol, Bristol BS8 1QU, UKSchool of Science, Faculty of Engineering and Science, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UKThe underutilized cement-rich fine fraction of concrete-based demolition waste is a potential sorbent for aqueous metal ion contaminants. In this study, crushed concrete fines (CCF) were found to exclude 33.9 mg g<sup>−1</sup> of Cr<sup>3+</sup>, 35.8 mg g<sup>−1</sup> of Ni<sup>2+</sup>, and 7.16 mg g<sup>−1</sup> of Sr<sup>2+</sup> from ~1000 ppm single metal nitrate solutions (CCF:solution 25 mg cm<sup>−3</sup>) under static batch conditions at 20 °C after 3 weeks. The removal of Sr<sup>2+</sup> followed a pseudo-second-order reaction (k<sub>2</sub> = 3.1 × 10<sup>−4</sup> g mg<sup>−1</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.999), whereas a pseudo-first-order model described the removal of Cr<sup>3+</sup> (k<sub>1</sub> = 2.3 × 10<sup>−4</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.998) and Ni<sup>2+</sup> (k<sub>1</sub> = 5.7 × 10<sup>−4</sup> min<sup>−1</sup>, R<sup>2</sup> = 0.991). In all cases, the principal mechanism of interaction was the alkali-mediated precipitation of solubility-limiting phases on the surface of the CCF. Four consecutive deionized water leaching procedures (CCF:water 0.1 g cm<sup>−3</sup>) liberated 0.53%, 0.88%, and 8.39% of the bound Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> species, respectively. These findings indicate that CCF are an effective sorbent for the immobilization and retention of aqueous Cr<sup>3+</sup> and Ni<sup>2+</sup> ions, although they are comparatively ineffectual in the removal and sustained exclusion of Sr<sup>2+</sup> ions. As is commonly noted with Portland cement-based sorbents, slow removal kinetics, long equilibrium times, the associated release of Ca<sup>2+</sup> ions, high pH, and the formation of loose floc may preclude these materials from conventional wastewater treatments. This notwithstanding, they are potentially suitable for incorporation into permeable reactive barriers for the containment of metal species in contaminated groundwaters, sediments, and soils.https://www.mdpi.com/2073-4352/12/5/717recycledcementconcretedemolition wastechromiumnickel |
| spellingShingle | Andrew P. Hurt Aimee A. Coleman Nichola J. Coleman Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines Crystals recycled cement concrete demolition waste chromium nickel |
| title | Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines |
| title_full | Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines |
| title_fullStr | Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines |
| title_full_unstemmed | Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines |
| title_short | Interactions of Cr<sup>3+</sup>, Ni<sup>2+</sup>, and Sr<sup>2+</sup> with Crushed Concrete Fines |
| title_sort | interactions of cr sup 3 sup ni sup 2 sup and sr sup 2 sup with crushed concrete fines |
| topic | recycled cement concrete demolition waste chromium nickel |
| url | https://www.mdpi.com/2073-4352/12/5/717 |
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