Quintáns-Fondo Ana, Santás-Miguel Vanesa, Nóvoa-Muñoz Juan C, Arias-Estévez Manuel, Fernández-Sanjurjo María J, Álvarez-Rodríguez Esperanza, Núñez-Delgado Avelino
Department of Soil Science and Agricultural Chemistry, Engineering Polytechnic School, Universidade de Santiago de Compostela, Lugo, Spain.
Department of Plant Biology and Soil Science, Faculty of Sciences, University of Vigo, Ourense, Spain.
Front Chem. 2018 Mar 6;6:51. doi: 10.3389/fchem.2018.00051. eCollection 2018.
The purpose of this work was to elucidate the repercussion of changing pH, incubation time and As(V) competition on fluoride (F) sorption on forest and vineyard soil samples, pyritic, and granitic materials, as well as on the by-products pine sawdust, oak wood ash, mussel shell ash, fine and coarse mussel shell, and slate processing waste fines. To reach this end, the methodological approach was based on batch-type experiments. The results indicate that, for most materials, F sorption was very high at the start, but was clearly diminished when the pH value increased. However, oak wood ash and shell ash showed high F sorption even at alkaline pH, and pine sawdust showed low F sorption for any pH value. Specifically, F sorption was close to 100% for both ashes at pH < 6, and around 70% at pH 10, while for forest soil it was close to 90% at pH < 2, and around 60% at pH values near 8. Regarding the effect of incubation time on F sorption, it was very low for both soils, pyritic material, granitic material, and both kinds of ashes, as all of them showed very rapid F sorption from the start, with differences being lesser than 10% between sorption at 30 min and 1 month of incubation. However, sawdust and slate fines sorbed 20% of added F in 30 min, remaining constant up to 12 h, and doubling after 30 days. And finally, mussel shell sorbed 20% at 30 min, increasing to close to 60% when incubation time was 30 days. This means that some of the materials showed a first sorption phase characterized by rapid F sorption, and a slower sorption in a second phase. As regards the effect of the presence of As(V) on F sorption, it was almost negligible, indicating the absence of competition for sorption sites. In view of that all, these results could aid to appropriately manage soils and by-products when focusing on F removal, in circumstances where pH value changes, contact time vary from hours to days, and potential competition between F and As(V) could take place.
本研究旨在阐明pH值变化、孵育时间和五价砷（As(V)）竞争对森林土壤、葡萄园土壤样品、黄铁矿、花岗岩材料以及副产品松木锯末、橡木灰、贻贝壳灰、粗细贻贝壳和板岩加工废粉中氟化物（F）吸附的影响。为实现这一目的，采用了基于批次实验的方法。结果表明，对于大多数材料，F的吸附在开始时非常高，但随着pH值的升高明显降低。然而，橡木灰和贝壳灰即使在碱性pH值下也表现出高F吸附，而松木锯末在任何pH值下F吸附都较低。具体而言，在pH < 6时，两种灰分的F吸附率接近100%，在pH 10时约为70%，而对于森林土壤，在pH < 2时接近90%，在pH值接近8时约为60%。关于孵育时间对F吸附的影响，对于两种土壤、黄铁矿材料、花岗岩材料和两种灰分来说都非常低，因为所有这些材料从一开始就表现出非常快速的F吸附，孵育30分钟和1个月时的吸附差异小于10%。然而，锯末和板岩细粉在30分钟内吸附了20%添加的F，直到12小时保持不变，30天后增加一倍。最后，贻贝壳在30分钟时吸附了20%，孵育时间为30天时增加到接近60%。这意味着一些材料表现出第一个吸附阶段，其特征是快速F吸附，而在第二阶段吸附较慢。至于As(V)的存在对F吸附的影响，几乎可以忽略不计，表明不存在吸附位点的竞争。鉴于所有这些结果，在关注F去除的情况下，当pH值变化、接触时间从数小时到数天不等且F和As(V)之间可能发生潜在竞争时，这些结果有助于适当地管理土壤和副产品。
