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RISS 인기검색어
- 검색키워드
- 저자 : Konhauser, Kurt O. (검색결과 3 건)
- 무료
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von Gunten, Konstantin,Alam, Md. Samrat,Hubmann, Magdalena,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. Elsevier 2017 Bioresource technology Vol.236 No.-
<P><B>Abstract</B></P> <P>A modified Community Bureau of Reference (CBR) sequential extraction method was tested to assess the composition of untreated pyrogenic carbon (biochar) and oil sands petroleum coke. Wood biochar samples were found to contain lower concentrations of metals, but had higher fractions of easily mobilized alkaline earth and transition metals. Sewage sludge biochar was determined to be less recalcitrant and had higher total metal concentrations, with most of the metals found in the more resilient extraction fractions (oxidizable, residual). Petroleum coke was the most stable material, with a similar metal distribution pattern as the sewage sludge biochar. The applied sequential extraction method represents a suitable technique to recover metals from these materials, and is a valuable tool in understanding the metal retaining and leaching capability of various biochar types and carbonaceous petroleum coke samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Modified four step sequential extraction method suitable for pyrolyzed materials. </LI> <LI> Untreated biochar may easily release alkaline earth and transition metals. </LI> <LI> Wood biochar releases metals more readily than does sewage sludge biochar. </LI> </UL> </P>
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Thermodynamic Analysis of Nickel(II) and Zinc(II) Adsorption to Biochar
Alam, Md. Samrat,Gorman-Lewis, Drew,Chen, Ning,Flynn, Shannon L.,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. American Chemical Society 2018 Environmental science & technology Vol.52 No.11
<P>While numerous studies have investigated metal uptake from solution by biochar, few of these have developed a mechanistic understanding of the adsorption reactions that occur at the biochar surface. In this study, we explore a combined modeling and spectroscopic approach for the first time to describe the molecular level adsorption of Ni(II) and Zn(II) to five types of biochar. Following thorough characterization, potentiometric titrations were carried out to measure the proton (H<SUP>+</SUP>) reactivity of each biochar, and the data was used to develop protonation models. Surface complexation modeling (SCM) supported by synchrotron-based extended X-ray absorption fine structure (EXAFS) was then used to gain insights into the molecular scale metal-biochar surface reactions. The SCM approach was combined with isothermal titration calorimetry (ITC) data to determine the thermodynamic driving forces of metal adsorption. Our results show that the reactivity of biochar toward Ni(II) and Zn(II) directly relates to the site densities of biochar. EXAFS along with FT-IR analyses, suggest that Ni(II) and Zn(II) adsorption occurred primarily through proton-active carboxyl (−COOH) and hydroxyl (−OH) functional groups on the biochar surface. SCM-ITC analyses revealed that the enthalpies of protonation are exothermic and Ni(II) and Zn(II) complexes with biochar surface are slightly exothermic to slightly endothermic. The results obtained from these combined approaches contribute to the better understanding of molecular scale metal adsorption onto the biochar surface, and will facilitate the further development of thermodynamics-based, predictive approaches to biochar removal of metals from contaminated water.</P> [FIG OMISSION]</BR>
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Alam, Md. Samrat,Swaren, Logan,von Gunten, Konstantin,Cossio, Manuel,Bishop, Brendan,Robbins, Leslie J.,Hou, Deyi,Flynn, Shannon L.,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. Elsevier 2018 Applied geochemistry Vol.88 No.1
<P><B>Abstract</B></P> <P>Biochar has emerged as a useful amendment to release nutrients into agricultural soil, to increase crop productivity, and as a sorbent to remediate metals and organics contamination. Since soils have heterogeneous physical properties across a given crop field, and even over a growing season, it is imperative to select the most appropriate biochar for the intended purpose and in defining the amendment level. In this study, we investigate the adsorption of Cd(II) and Se(VI) as model pollutant cations and anions, respectively, to two agricultural soils amended with a wood pin chip biochar (WPC). The proton reactivity of each sorbent was determined by potentiometric titration, and single-metal, single-sorbent experiments were conducted as a function of pH. The resulting data were modeled using a non-electrostatic surface complexation modeling (SCM) approach to determine the proton and metal binding constants and surface functional group concentrations of each soil and WPC. The SCM approach is a considerable advance over empirical modeling approaches because SCM models can account for changes in pH, ionic strength, temperature, and metal-to-sorbent ratio that may happen over the course of a growing season. The constants derived from the single-metal, single-sorbent experiments were then used to predict the extent of metal adsorption in more complex mixtures of Cd, Se, soil and WPC. Overall the SCM approach was successful in predicting metal distribution in multi-component mixtures. In cases where the predictions were poorer than expected, we identify reasons and discuss future experiments needed to further the application of SCM to sorbent mixtures containing biochar.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cd(II) and Se(VI) adsorption to biochar, soils and their admixtures is tested as a function of pH. </LI> <LI> Surface complexation modeling is applied to biochar-amended soils for the first time. </LI> <LI> Potential impacts of metal-DOC complexes is explored. </LI> <LI> Cd(II) and Se(VI) adsorption to biochar-soil mixtures is generally well-predicted by models. </LI> <LI> Surface complexation models are a promising alternative to empirical adsorption models in the systems tested. </LI> </UL> </P>
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