The effect of oxalate on the dissolution rates of oligoclase and tremolite
The effect of oxalate on the dissolution rates of oligoclase and tremolite
复制标题
草酸盐对寡长石和透闪石溶出速率的影响
DOI：
10.1016/0016-7037(87)90306-1
复制
发表时间：
1987
影响因子：
5
通讯作者：
J. Drever
中科院分区：
文献类型：
--
作者：
M. Mast;J. Drever
在22°C的流动反应器中，研究了草酸盐对铝和其它阳离子的强螯合剂对长石和透闪石溶解速率的影响。草酸盐在0.5和1 mM的浓度基本上没有影响的透闪石的溶解速率，也没有从奥长石释放的Si的稳态速率。草酸盐对溶解速率没有影响的事实表明，Si而不是Al或Mg的脱离是速率限制步骤。在pH 4和9时，草酸盐对铝的稳态释放速率没有影响，溶解是一致的。在pH值为5和7时，奥长石溶解是一致的草酸盐的存在下，但在没有草酸铝优先保留在固体相对于Si。大的瞬态“尖峰”的Al或Si时，观察到草酸盐添加到或从系统中删除。尖峰的原因是未知的，我们建议吸附在长石表面远离网站的活跃溶解作为一种可能性。在反应器中的解决方案是相对于三水铝石和高岭石不饱和，所以既不是尖峰也不一致的溶解可以解释形成的二次沉淀。透闪石的溶解速率是独立的pH值范围2-5，并在较高的pH值降低。在我们的实验中的溶解速率的长石是独立的pH值范围4-9。由于这些矿物的溶解速率与pH值和有机配体浓度无关，因此大气中的酸沉降对花岗岩风化产生的阳离子供应速率的影响应该是很小的。
The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22°C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of release of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si.Large transient “spikes” of Al or Si are observed when oxalate is added to or removed from the system. The cause of the spikes is unknown; we suggest adsorption on feldspar surfaces away from sites of active dissolution as a possibility. Solutions in the reactors are undersaturated with respect to both gibbsite and kaolinite, so neither the spikes nor the incongruent dissolution can be explained by formation of a secondary precipitate.The rate of dissolution of tremolite is independent of pH over the pH range 2–5, and decreases at higher pH. The rate of dissolution of oligoclase in our experiments was independent of pH over the pH range 4–9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.