Adsorption-desorption characteristics of steel slag for ferrous and sulfur ions
Ferrous ion (Fe<sup>2+</sup>) and reduced sulfur ion (S<sup>2-</sup>) were main toxic elements in the cold waterlogged paddy soil. How to remove Fe<sup>2+</sup> and S<sup>2-</sup> effectively was the key to improve the quality of cold waterlogged paddy...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Zhejiang University Press
2015-07-01
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| Series: | 浙江大学学报. 农业与生命科学版 |
| Subjects: | |
| Online Access: | https://www.academax.com/doi/10.3785/j.issn.1008-9209.2014.05.131 |
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| Summary: | Ferrous ion (Fe<sup>2+</sup>) and reduced sulfur ion (S<sup>2-</sup>) were main toxic elements in the cold waterlogged paddy soil. How to remove Fe<sup>2+</sup> and S<sup>2-</sup> effectively was the key to improve the quality of cold waterlogged paddy soil. Steel slag has been confirmed as a good sorption material in waste water treatments for some heavy metals and organic pollutants. These properties suggested that steel slag might have the ability to adsorb and fix Fe<sup>2+</sup> and S<sup>2-</sup> from cold waterlogged paddy soil, and improve the quality of cold waterlogged paddy soil by reducing Fe<sup>2+</sup> and S<sup>2-</sup>.The characteristics of Fe<sup>2+</sup> and S<sup>2-</sup> adsorption-desorption by steel slag were studied in the present study, to reveal whether steel slag was a good sorption material for Fe<sup>2+</sup> and S<sup>2-</sup>, and to understand whether steel slag had the potentiality in controlling Fe<sup>2+</sup> and S<sup>2-</sup> and improving the quality of cold waterlogged paddy soil.The sorption of Fe<sup>2+</sup> and S<sup>2-</sup> by steel slag was studied using batch incubation experiments, while the effects of adsorption time (0.25, 0.5, 1, 1.5, 2, 3 or 4 h, respectively) , Fe<sup>2+</sup> and S<sup>2-</sup> concentration (10, 30, 50, 100, 150 mg/L Fe<sup>2+</sup> or 10, 30, 50, 80, 100 mg/L S<sup>2-</sup>, respectively) , pH (the pH range of adsorption system was from 1.00 to 12.00) , temperature (designed as 15, 25, 35 or 45 ℃, respectively) and ionic strength (0.01 mol/L NaCl, 0.02 mol/L NaCl or 0.005 mol/L MgCl<sub>2</sub>, respectively) in adsorption reaction solution on the sorption were investigated. Except for adsorption time experiments, all treatments were shook 3 h and stood for one night for complete adsorption reaction. Then, the adsorption reaction solution was centrifuged at 4 000 r/min for 10 min and filtrated for further determination of Fe<sup>2+</sup> and S<sup>2-</sup> concentrations. The stability of Fe<sup>2+</sup> and S<sup>2-</sup> adsorbed by steel slag was further validated by desorption experiments under similar conditions.The results showed that the adsorption kinetics of Fe<sup>2+</sup> and S<sup>2-</sup> by steel slag followed the Elovich kinetics equation, and the correlation coefficients were 0.94 and 0.89 respectively. Freundlich isotherm model could simulate the adsorption processes better than other models, and the correlation coefficients for Freundlich isotherm model were 0.97 and 0.94 respectively. Their parameters were all less than 1, which indicated that the adsorption processes were non-preferential adsorption. Free energy variation (ΔG) for the Fe<sup>2+</sup> sorption was greater than 0, which indicated that this reaction was non-spontaneous; but ΔG for the S<sup>2-</sup> sorption was less than 0, which indicated that this reaction was spontaneous. The adsorption process was endothermic because high temperature was beneficial to their adsorption. And the adsorption process had greater pH adaptability range from 1.50 to 11.50. The adsorption of Fe<sup>2+</sup> was major in inner sphere complexation, while the adsorption of S<sup>2-</sup> was major in outer complexation, which were consistent with the results in thermodynamic experiments. The adsorption rates were all very high, but the desorption rates were low in all experimental conditions, which showed that the adsorption stability of steel slag was superior.On the whole, steel slag had good ability to remove Fe<sup>2+</sup> and S<sup>2-</sup>, might be a potential adsorbent in controlling Fe<sup>2+</sup> and S<sup>2-</sup> and improving the quality of cold waterlogged paddy soil. |
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| ISSN: | 1008-9209 2097-5155 |