Adsorption mechanism of selenate and selenite on the binary oxide systems

Chan, Yu‐Wei; Kuan, Wen-Hui; Chen, Tsan‐Yao; Wang, Ming Kuang

doi:10.1016/j.watres.2009.06.056

Cited by 131 publications

(64 citation statements)

References 33 publications

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“…Thereafter, the adsorption slowed down and quickly reached equilibrium (Fig. 8).A similar behavior was observed for selenium adsorption on binary oxide systems such as Al 3+ /SiO 2 and Fe 3+ /SiO 2 , (Chan et al, 2009) and on different forms of iron oxyhydroxides and ferihydrite (Parida et al, 1997) where the adsorption rate was rapid in the first minutes and approached equilibrium at about 2 h. In the same way, selenite adsorption on magnetite nanoparticles reached equilibrium in approximately 30 min (Lopez de Arroyabe et al, 2008). Longer times to reach equilibrium have also been reported for selenium adsorption: about 30 h for selenium adsorption onto natural magnetite (Martinez et al, 2006), or 50 h for selenium adsorption onto goethite and hematite .…”

Section: Effect Of Contact Timesupporting

confidence: 73%

“…After the modification of silica particles using aluminum hydroxide (Al(OH) 3 ), it was observed that the resulting zeta potential of the mixed oxide coincided with the PZC of pure Al(OH) 3 (pH 9.1) (Meng and Letterman, 1993). In contrast to the Al(OH) 3 /SiO 2 system, pHpzc measurements for the Fe(OH) 3 /SiO 2 system showed that the pZC of the mixed oxide was much lower than that of pure Fe(OH) 3 (Chan et al, 2009). This difference was considered as the overall results contributed by negatively charged silica and positively charged ferric hydroxide.…”

Section: Point Of Zero Charge (Pzc) For Adsorbentsmentioning

confidence: 99%

“…9) could be attributed to a weaker dependence of selenite adsorption on pH in comparison to selenate (as shown in Section 3.3). Previous studies on selenium adsorption onto activated alumina (Ghosh et al, 1994) and Fe 3+ -coated silica (Chan et al, 2009) concluded that the adsorption of selenate (Se(VI)) was more strongly dependent on pH than that of selenite (Se(IV)). The theory of a partial dissolution of the adsorbent was also considered, although the solubility of magnetite at pH 3.0 was very low.…”

Section: Effect Of Contact Timementioning

confidence: 99%

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Continuation of Crosscutting Technology Development at Cast

Yoon¹

2012

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5Figure ES-2. Optimization of conditions for leaching Coal B with hydrochloric acid solutions (The selection of time/pH conditions in the dark green region should result in the removal of >30% of the sodium. Note also that a flag has been added to show the amount of sodium in the leach solution, 35% sodium removal, and the sodium content in the product ash). Coal DCoal D showed significantly greater sodium removal than Coal B for similar treatment conditions. The treatability of Coal B is demonstrated in Figures ES3 to ES5. . Coal D leach results for hydrochloric acid solutions (Greater than 75% of the sodium was removed using pH 3 acidic solutions at a 1-hour treatment time. The initial sodium, reported as sodium oxide in the ash, was 6.16 %. The removal of over one-half of the sodium can be achieved using conditions of pH 5, 0.5 hours). Recommended Future StudiesIt is recommended that future studies include, but not be limited to:• Investigation to determine if multiple leach solution contacts with new coal will allow recycle of the leach solution without detrimentally affecting the leachability of the coals and to produce a concentrated sodium bearing solution in order to limit the amount of leach solution that would have to be treated prior to water recycle or disposal.• Water cleanup will be required because of the relatively high sodium and chloride or sulfate content.• Evaluation of where and how the leachate could be introduced into the coal preparation treatment system. • Evaluation of the possible impact of pretreatment on the subsequent shipping and combustion processes.• The anticipated cost of the sodium cleansing treatment and subsequent water treatments. INTRODUCTION BackgroundThe US Department of Energy (DOE) Center for Advanced Separation Technologies (CAST), Great Northern Properties (GN), and the Montana Board Research and Commercialization Technology (MBRCT) are funding this project. The project is being administered and the research directed and conducted at CAMP. The intent of the project is to identify, and validate selected currently used (or previously studied) removal and sodium recovery treatment alternative(s) using laboratory bench-scale tests on four Montana coal samples. If the coals cannot be effectively treated by known techniques, alternative treatments will be developed. The evaluation of selected sodium removal technologies are presently underway and the following four stages are being and will be followed in future work: the successful removal of sodium from the coal so that the ash will content less than three percent, the rate at which the sodium ions are removed, characterization of the waste produced by sodium removal processing, and the overall economics of viable processes. Not part of the initial Project, but a necessary follow-up, will be the scale-up of the most appropriate sodium removal technology(s) in applications with companies using Clean Coal Technology to demonstrate sodium removal process or processes on a pilot scale. Objective and ApproachThe overall ob...

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Section: Effect Of Contact Timesupporting

confidence: 73%

Section: Point Of Zero Charge (Pzc) For Adsorbentsmentioning

confidence: 99%

Section: Effect Of Contact Timementioning

confidence: 99%

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Continuation of Crosscutting Technology Development at Cast

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2012

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“…No entanto, para o solo LVA-B, com predomínio de óxido de Al e goethita (Quadro 3), o processo de adsorção não mostrou-se tão reversível, já que grande parte do Se adsorvido não foi dessorvida. Dessa forma, deduzse que, possivelmente, o Se tende a ficar ligado via complexo de esfera interna, como observado por Chan et al (2009) e conforme demonstrado no trabalho de Wijnja & Schulthess (2000b). Esses autores afirmam que, em óxido de Al, o Se forma preferencialmente complexos de esfera externa, porém, em pH < 6, uma pequena fração também está presente como complexo de esfera interna.…”

Section: Quadro 7 Coeficiente De Distribuição (K D ) Para Cada Solo unclassified

“…Muitos estudos sobre o comportamento ambiental geoquímico do Se têm sido apresentados em inúmeras publicações (Li et al, 2008;Chan et al, 2009). Isso porque o Se é um elemento essencial para humanos e animais, mas que se torna tóxico em concentrações elevadas.…”

Section: Introductionunclassified

Sorção de selênio em solos do bioma cerrado

Abreu¹,

Carvalho²,

Curi³

et al. 2011

Rev. Bras. Ciênc. Solo

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O estudo da distribuição de Se em solos é de extremo interesse devido à estreita faixa entre níveis de deficiência e toxidez. A espécie química de Se com maior potencial toxicológico é o ânion selenato, em razão de sua alta mobilidade em solos, sendo assim de grande importância a compreensão de seu comportamento em solos tropicais. Foi realizado um experimento de adsorção, utilizando-se 2 g de solo em 20 mL de solução, contendo dez diferentes concentrações de Se na forma de Na2SeO4, com tempo de agitação de 24 h, em solução eletrolítica de NaNO3 0,03 mol L-1. Para estudar o efeito do tempo na adsorção, realizou-se um experimento nas mesmas condições das do ensaio de adsorção, porém foi utilizada somente a concentração de 1 mg L-1 Se, variando o tempo de agitação de 15 min a 72 h. A isoterma de adsorção de Freundlich foi a de melhor ajuste aos dados experimentais. Para o estudo cinético, o melhor modelo foi o de pseudossegunda ordem, e o tempo necessário para a adsorção do Se atingir o equilíbrio foi de aproximadamente 4 h. De modo geral, os valores obtidos para Kd foram baixos; assim, conclui-se que o Se tende a ficar mais em solução do que retido nas partículas do solo. Portanto, os solos mais intemperizados, gibbsíticos e goethíticos e com maior conteúdo de argila foram os que tiveram maior afinidade pelo selênio. Nos solos com textura média ou arenosa, esse elemento tende a ser menos retido, razão pela qual pode ser absorvido pelas plantas ou ser facilmente lixiviado, podendo causar malefícios ao ecossistema.

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Adsorption of selenite and selenate ions onto thiourea‐formaldehyde resin

Gezer

Gülfen

Aydın

2011

J of Applied Polymer Sci

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In the present work, thiourea-formaldehyde (TUF) chelating resin was synthesized and used in the adsorptions of selenite (SeO The effects of initial acidity and initial selenium concentrations on the adsorptions were examined by batch technique. The synthesized resin was applied to the elemental analysis to determine its composition. FT-IR spectra and SEM/EDS were also recorded before and after selenite adsorption. It was found that selenite and selenate ions were adsorbed onto TUF resin at strong acidic conditions (3-5M HCl). The adsorption capacities of the resin were calculated as 833.3 mg g À1 TUF resin for selenite ions and 526.3 mg g À1 TUF resin for selenate. All the adsorption data obtained for both selenite and selenate ions fitted well to the Langmuir isotherm. It was seen that the adsorption mechanisms in the both adsorptions were governed by the reduction of selenite or selenate to elemental selenium, Se

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Adsorption mechanism of selenate and selenite on the binary oxide systems

Cited by 131 publications

References 33 publications

Continuation of Crosscutting Technology Development at Cast

Continuation of Crosscutting Technology Development at Cast

Sorção de selênio em solos do bioma cerrado

Adsorption of selenite and selenate ions onto thiourea‐formaldehyde resin

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