Dehydroxylation of Aluminous Goethite: Unit Cell Dimensions, Crystal Size and Surface Area

Ruan, Huada Daniel; Gilkes, Robert

doi:10.1346/ccmn.1995.0430207

Cited by 93 publications

(30 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Generally, the shape of the curve became more sigmoidal, and the dissolution rate decreased with increasing Al substitution, a trend also observed by others (Cervini-Silva and Sposito 2002;Cornell and Schwertmann 2003;Schwertmann 1991). The shapes of our dissolution curves indicate that interdomain boundaries and surface defects may be created during the early stages of dissolution (Ruan and Gilkes, 1995), thereby increasing surface area and the rate of proton-promoted dissolution.…”

Section: Acid Dissolution Of Synthetic Goethitessupporting

confidence: 85%

“…only goethite) at the detection limit of the XRD (*5 %). Ruan and Gilkes (1995) and Schwertmann and Cornell (1991) report smaller unit-cell dimensions for goethite following Al for Fe isomorphous substitution, shifting several peak positions to higher angles. We therefore interpret the progressive shift of the 111, 511, and 610 reflections to higher angles within the series of Al-substituted goethites as confirmation of increasing Al for Fe substitution in our goethites (Fig.…”

Section: Methodsmentioning

confidence: 96%

See 1 more Smart Citation

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5

Dubbin

Bullough

2016

Aquat Geochem

View full text Add to dashboard Cite

Naturally occurring goethites often show Al for Fe substitution approaching 33 mol% Al. This substitution has potential to influence the rate of goethite dissolution and therefore the supply of bioavailable Fe. Siderophores such as ferrichrome and enterobactin have considerable potential to dissolve Fe from Fe 3? rich minerals, including Al-substituted goethites. Here, we show that Al substitution in synthetic goethites (0.021 C x C 0.098) gives rise to a significant increase in both ferrichrome-and enterobactin-mediated dissolution rates. In the presence of ferrichrome, Al-goethite (x = 0.033) yields a dissolution rate of 19.0 9 10 -3 lmol m -2 h -1 , nearly twice that of pure goethite, whereas dissolution of the most highly substituted Al-goethite (x = 0.098) is 36.9 9 10 -3 lmol m -2 h -1, more than threefold greater than the pure mineral. Similarly, in the presence of enterobactin, the dissolution rate of Al-goethite increases with increasing Al substitution. Ferrichrome is a less effective ligand than enterobactin in its dissolution of both pure goethite and the range of Al-goethites, an observation we ascribe to the lower affinity of the hydroxamate functional groups of ferrichrome for both Fe 3? and Al 3? . Despite greater affinity of both ferrichrome and enterobactin for Fe 3? over Al 3? , we observe a broadly congruent dissolution of all our Al-goethites.

show abstract

Section: Acid Dissolution Of Synthetic Goethitessupporting

confidence: 85%

Section: Methodsmentioning

confidence: 96%

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5

Dubbin

Bullough

2016

Aquat Geochem

View full text Add to dashboard Cite

show abstract

“…A estimativa de características cristalográficas em subamostras tratadas ao longo das dissoluções mostrou que o DMC (110) da goethita aumentou na maioria das amostras (Quadro 2), possivelmente por causa da persistência de cristais com maior proporção de domínios coerentes (Ruan & Gilkes, 1995b;Strauss et al, 1997). Nas amostras não-latossólicas, o DMC (110) permaneceu estável (G3 e G10) ou apresentou pequeno incremento (G7), mesmo considerando que, na última subamostra tratada dessas amostras em que este parâmetro foi estimado (480 min para G3, 80 min para G10 e 60 min para G7) (Quadro 2), o teor de Fe d inicial nessas amostras (100 mg) tenha sido dissolvido em mais de 60 % (Figura 2 a).…”

Section: Características Cristalográficasunclassified

Variabilidade de goethita e hematita via dissolução redutiva em solos de região tropical e subtropical

Inda

Kämpf

2005

Rev. Bras. Ciênc. Solo

View full text Add to dashboard Cite

RESUMODezenove amostras de horizontes B latossólicos, uma de B plíntico, uma de B incipiente e uma de horizonte Cr foram submetidas a dissoluções seletivas da goethita e da hematita por ditionito-citratro-bicarbonato de sódio a 20 o C em intervalos de tempo entre 5 e 3.840 minutos. O diâmetro médio do cristal (DMC), área superficial específica (ASE) e substituição do ferro por Al (substituição por Al 3+ ) da goethita e da hematita nas amostras foram estimados, por difratometria de raios X (DRX), em subamostras não tratadas e em subamostras tratadas selecionadas ao longo das dissoluções seletivas. O controle das fases de goethita e hematita que persistiram após cada etapa da dissolução seletiva foi realizado pelo método da difratometria diferencial de raios X (DDRX). A cinética dissolutiva dos cristais foi descrita por meio da segmentação das curvas de dissolução do ferro no tempo em intervalos em que o comportamento dissolutivo foi linear. As taxas de dissolução nos diferentes segmentos lineares foram estimadas a partir do coeficiente angular da reta relativa a cada segmento. Em amostras goethíticas latossólicas, a metodologia discriminou diferentes fases de goethita (populações heterogêneas) quanto à substituição por Al 3+ , DMC e ASE e ofereceu condições para classificar o grau de estabilidade da goethita em baixa, média, alta e muito alta estabilidade. Amostras goethíticas oriundas de ambientes pedogênicos jovens e amostras hematíticas latossólicas caracterizaram-se pela maior homogeneidade de seus cristais, classificados como de baixa e média estabilidade. Nas amostras goethíticas, a proporção de cristais com maior estabilidade (alta substituição por Al 3+ e cristalinidade) em cada população mostrou associação positiva com a proporção de gibbsita em relação a caulinita nas amostras. A hematita apresentou menor resistência à dissolução por redução em relação à goethita, exceto quando a última combinou baixa substituição por Al 3+ e alta ASE. A caracterização de populações heterogêneas

show abstract

“…Micro-, meso-, and macro-pores, as well as voids, which contribute to the increase in specific surface area, were observed to be developed [5]. An increase in specific surface area has been reported to be related highly to the decrease in particle or crystal size [33], and the specific surface area is the most important factor in controlling the kinetic P adsorption [25]. The mineral compositions and surface/structural defects are also important factors that affect the P adsorption [25,[47][48][49].…”

Section: Effect Of Modification Process On P Adsorptionmentioning

confidence: 97%

Adsorption of Phosphorus by Modified Clay Mineral Waste Material Relating to Removal of it from Aquatic System

Jiang¹,

Su²,

Ruan

et al. 2014

IJEMA

View full text Add to dashboard Cite

This study examined the application of modified clay mineral waste material (MCMWM) for removal of phosphorus (P) from aquatic systems including surface water and wastewater related to the application of recycled solid waste materials. The effects of ionic strength and pH on P adsorption by MCMWM were investigated at pH values of 3, 5, 6, 7 and 9 with P concentrations of 10, 20, 40, 100 and 200 mg/L in solution. The P adsorption was rapidly at the early stage with 95% of P in solution being adsorbed for 10 mg/L P in solution at a high pH range within 0.5 hr. The amount of P adsorbed increased with increasing ionic strength. The amount of P adsorbed increased continuously as pH values increased from 3 to 9 for P adsorption at 10 mg/L. Other series of P concentrations in solution showed variable trends due to the rates of P adsorption being affected by pH associated with the effect of ionic strength. The maximum amounts of P adsorbed and the highest percentages of P adsorbed were obtained at pH 9 for all levels of P concentrations, and at pH 7 for the lower P concentrations in solution. Calcium (Ca) ion was found to form a bridge for P adsorption in solution as the increases in the amount of P adsorbed at high pH values was related to the performance of Ca in favoring P to be adsorbed either onto the surfaces or incorporated into the structural bonds of MCMWM. Ionic strength, pH and modification process have been found to be the important factors that influenced P adsorption in solution.

show abstract

Dehydroxylation of Aluminous Goethite: Unit Cell Dimensions, Crystal Size and Surface Area

Cited by 93 publications

References 36 publications

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5

Variabilidade de goethita e hematita via dissolução redutiva em solos de região tropical e subtropical

Adsorption of Phosphorus by Modified Clay Mineral Waste Material Relating to Removal of it from Aquatic System

Contact Info

Product

Resources

About