Effect of low-molecular-weight organic acids on the adsorption of fluoride on soils with variable charge
低分子量有机酸对几种可变电荷土壤吸附氟的影响

The effect of four low molecular weight organic acids on the adsorption of fluoride on soils with variable charge was investigated with a batch method. The results showed that organic acids reduced the adsorption of fluoride through competition with F - for sorption sites. The oxalic acid and malonic acid with simple chemical structure were more effective than citric acid and malic acid in reducing F - adsorption. The effect of organic acids on F - adsorption increased with the increase in pH. A higher content of iron oxides in soils led to more reduction in F - adsorption by organic acids. At low pH and with more fluoride added, existence of organic acids increased the adsorption of fluoride due to the competition of organic acids with F - for soluble Al and the increase of free fluoride in soil solution. This kind of effect mainly occurred in the soils with a higher solubility of Al.