【フロー型反応器(thin-film flow-through reactor)による黒雲母の溶解実験】
【溶解速度式:R = kH [H+]m
+ ko + kOH[H+]n
(moles m-2 h-1)】
『Abstract
The rate and stoichiometry of biotite dissolution were studied
in the pH range 2-10 using thin-film continuous flow reactors.
The release of interlayer K is relatively fast and becomes diffusion-controlled
within a few days. The release rates of framework ions (Mg, Al,
Fe, Si) are much slower and reach an apparent steady-state within
ten days. The stoichiometry and rate of dissolution vary greatly
with pH. Consistent with surface reaction control of release rates,
an empirical rate law, R = kH [H+]m
+ ko + kOH[H+]n
(moles m-2 h-1) describes proton- and hydroxyl-catalysed
dissolution for each ion.
Si | Fe | Mg | Al | |
log kH | -4.45 | -5.10 | -4.93 | -5.31 |
m | 0.91 | 0.51 | 0.57 | 0.40 |
log ko | -7.31 | - | - | - |
log kOH | -11.29 | -15.36 | -10.57 | -12.58 |
n | -0.48 | -0.81 | -0.29 | -0.54 |
『要旨
黒雲母の溶解の速度と化学量論性についての研究を、薄膜連続式フロー型反応器を使ってpH2〜pH10の範囲で行った。層間のKの放出は比較的速く、数日で拡散律速になる。フレームワーク・イオン(Mg,Al,Fe,Si)の放出速度はかなり遅く、10日で見かけの定常状態に達する。溶解の化学量論性と速度は、pHによって大きく変動する。放出速度の表面反応律速と矛盾なく、経験的な速度則、R
= kH [H+]m + ko + kOH[H+]n
(moles/m2/時間) は各イオンに対するプロトンおよび水酸基により触媒された溶解を記述できる。
Si | Fe | Mg | Al | |
log kH | -4.45 | -5.10 | -4.93 | -5.31 |
m | 0.91 | 0.51 | 0.57 | 0.40 |
log ko | -7.31 | - | - | - |
log kOH | -11.29 | -15.36 | -10.57 | -12.58 |
n | -0.48 | -0.81 | -0.29 | -0.54 |
1. Introduction
1.1. Background
1.2. Biotite structure and composition
1.3. The weathering of biotite: mechanism and kinetic studies
1.4. Objectives
2. Experimental methods and specimen
2.1. Mineral sample
2.2. Experiments
2.2.1. Chemicals
2.2.2. Experimental conditions
2.2.3. Experimental procedure - the thin-film flow-through reactor
2.3. Calculation of dissolution rates and estimates of experimental
uncertainties and reproducibility
2.4. Solid phase analysis
3. Results and discussion
3.1. Dissolution behaviour in the thin-film flow-through reactor
3.1.1. Framework ions
3.1.2. Potassium
3.2. Alteration of the biotite - solid phase analyses
3.2.1. Observations using XPD
3.2.2. Observations using SEM and FTIR
3.2.3. Observations using Mossbauer(oの頭に¨)
analysis
3.2.4. Observations on the specific surface area
4. Modelling
4.1. A kinetic model for the dissolution of biotite
4.1.1. Modelling the pH dependent rate of multisite dissolution
4.1.2. Ion-exchange of interlayer potassium
4.1.3. Progression to congruent dissolution - an extended conceptual
model
4.2. Vermiculite stoichiometry
5. Conclusions and implications for groundwaters
Acknowledgments
References
Appendix