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Chen D.,Indiana University | Szostak P.,Indiana University | Wei Z.,Ohio State University | Xiao R.,Central South University | Xiao R.,Chinese National Engineering Research Center for Control
Science of the Total Environment | Year: 2016

Nutrient loss from soil, especially phosphorous (P) from farmlands to natural water bodies via surface runoff or infiltration, have caused significant eutrophication problems. This is because dissolved orthophosphates are usually the limiting nutrient for algal blooms. Currently, available techniques to control eutrophication are surprisingly scarce. Calcium sulfate or gypsum is a common soil amendment and has a strong complexation to orthophosphates. The results showed that calcium sulfate reduced the amount of water extractable P (WEP) through soil incubation tests, suggesting less P loss from farmlands. A greater decrease in WEP occurred with a greater dosage of calcium sulfate. Compared to conventional coarse calcium sulfate, nano calcium sulfate further reduced WEP by providing a much greater specific surface area, higher solubility, better contact with the fertilizer and the soil particles, and superior dispersibility. The enhancement of the nano calcium sulfate for WEP reduction is more apparent for a pellet- than a powdered- fertilizer. At the dosage of Ca/P weight ratio of 2.8, the WEP decreased by 31. ±. 5% with the nano calcium sulfate compared to 20. ±. 5% decrease with the coarse calcium sulfate when the pellet fertilizer was used. Computation of the chemical equilibrium speciation shows that calcium hydroxyapatite has the lowest solubility. However, other mineral phases such as hydroxydicalcium phosphate, dicalcium phosphate dihydrate, octacalcium phosphate, and tricalcium phosphate might form preceding to calcium hydroxyapatite. Since calcium sulfate is the major product of the flue gas desulfurization (FGD) process, this study demonstrates a potential beneficial reuse and reduction of the solid FGD waste. © 2015 Elsevier B.V. Source


Chai L.,Central South University | Chai L.,Chinese National Engineering Research Center for Control | Yang B.,Central South University | Liu H.,Central South University | And 4 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2016

BACKGROUND: SO2 is an important gaseous pollutant that seriously affects the environment and human health. The most common method for SO2 removal is absorption by NaOH solution and then forming HSO3 -. Since generation of high-value products and reduction of alkali consumption are important for the economy and practical application, selenium-catalyzed HSO3 - disproportionation was developed in this study. RESULTS: Selenium decreased the reaction temperature of HSO3 - disproportionation from >433K to 343K. The effects of HSO3 - concentration, temperature, selenium dosage, and stirring intensity were investigated. Selenium could be used at least five times with stable catalytic performance, indicating satisfactory reusability. More importantly, a catalytic mechanism was proposed using dynamic light scattering, differential scanning calorimetry and UV-visible transmittance spectrophotometry. Results showed that selenium-catalyzed HSO3 - disproportionation experienced a solid-liquid-solid phase transformation process. During this process, SeSO3 2 - and HSe- were identified as the intermediates. Furthermore, products, i.e. sulfur and sodium bisulfate, were characterized to demonstrate their structure and composition. CONCLUSION: Selenium was an efficient catalyst for HSO3 - disproportionation. This catalytic process offered the advantages of less consumption of alkali and production of high-valuable products, and thus was a potential alternative to other technology for SO2 removal in practical applications. © 2015 Society of Chemical Industry © 2016 Society of Chemical Industry. Source


Deng X.,Central South University | Deng X.,Hunan University of Technology | Chai L.,Central South University | Chai L.,Chinese National Engineering Research Center for Control | And 6 more authors.
Journal of Hazardous Materials | Year: 2012

Bioleaching of heavy metals from contaminated soil using Penicillium chrysogenum strain F1 was investigated. Batch experiments were performed to compare leaching efficiencies of heavy metals between one-step and two-step processes and to determine the transformation of heavy metal fractions before and after bioleaching. The results showed that two-step process had higher leaching efficiencies of heavy metals than one-step process. When the mass ratio of soil to culture medium containing P. chrysogenum strain F1 was 5% (w/v), 50%, 35%, 9% and 40% of Cd, Cu, Pb and Zn were removed in one-step process, respectively. The two-step process had higher removals of 63% Cd, 56% Cu, 14% Pb and 54% Zn as compared with one-step process. The results of the sequential extraction showed that the metals remaining in the soil were mainly bonded in stable fractions after bioleaching. The results of TEM and SEM showed that during bioleaching process, although the mycelium of P. chrysogenum was broken into fragments, no damage was obviously observed on the surface of the living cell except for thinner cell wall, smaller vacuoles and concentrated cytoplasm. The result implied that P. chrysogenum strain F1 can be used to remove heavy metals from polluted soil. © 2012 Elsevier B.V. Source


Zhang S.,Central South University | Zhang S.,Chinese National Engineering Research Center for Control | Zhang S.,Environmental Protection Agency of Yizhang | Yang Z.,Central South University | And 9 more authors.
Clean - Soil, Air, Water | Year: 2014

Soil-column experiments were conducted for removing of Cd and Pb from calcareous soils by using EDTA disodium (Na2EDTA). Up to 84.4 and 73.5% of diethylenetriaminepentaacetic acid (DTPA)-extractable Cd and Pb were removed by using 0.04molL-1 Na2EDTA at 1:8 of soil-to-solution ratio (w/v). More than 99% of Cd and 97% of Pb in leachate collected from washing procedure were precipitated at pH 10 by using Na2S+Ca(OH)2, while only 56.9% of Cd and 97.5% of Pb were removed with FeCl3+NaOH. The recovered Na2EDTA from leachate treatment did not lose much of its chelating capacity in the first washing process. However, in the second and third batch washing process, the removal of DTPA-extractable Cd decreased by 26.2 and 20.2%, while the removal of DTPA-extractable Pb decreased by 33.0 and 41.1%, respectively. Due to the high content of Na+ in the treated soil, several chemical amendments were employed to remove Na+. (NH4)2SO4 was the most suitable amendment reagent and the optimal concentration of (NH4)2SO4 was 0.08molL-1 at a soil-to-solution ratio of 1:3. The total cost for recycled Na2EDTA washing decreased by 68.9% as compared with fresh Na2EDTA washing. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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