Adsorption of phthalic acid and salicylic acid by two variable charge soils as influenced by sulphate and phosphate

Abstract

Low-molecular-weight (LMW) organic acids exist widely in soils, especially in the rhizosphere, and the adsorption of these acids may affect their reactions in soils. The adsorption behaviour of phthalic acid and salicylic acid by two variable charge soils (a Rhodic Ferralsol and a Haplic Acrisol) was investigated. Both soils exhibited great adsorption capacity for these organic acids, with a greater affinity for phthalic acid. The Rhodic Ferralsol adsorbed more organic acids of both kinds than the Haplic Acrisol, which was consistent with the content of iron and aluminum oxides in the two soils. The iron oxides in these soils played a significant role in adsorption of the organic acids, whilst the soil aluminosilicate minerals, such as kaolinite, showed a small adsorption capacity. The presence of phosphate and sulphate caused a decrease in the adsorption of both organic acids because of their competition with them for sorption sites. The phosphate showed a bigger inhibition on the adsorption than sulphate as a result of a greater amount of phosphate adsorbed by the soils. The adsorption of both organic acids was affected by pH only slightly at pH < 4.5. However, the adsorption decreased with the increase in pH at pH > 4.5. A similar trend was observed for the phosphate system, but the opposite was seen for the sulphate system. This suggests that the inhibition of sulphate on the adsorption of the organic acids decreased with the increase in pH, because the adsorption of sulphate decreased strongly with increasing pH.

Citramalic acid and salicylic acid in sugar beet root exudates solubilize soil phosphorus

“…The competition between salicylic acid and P for sorption sites in two variable-charge soils was documented as well by Xu et al [31]. On the other hand, Fox et al [27] compared 16 organic acids and found no significant differences between salicylic acid and water in P solubilization.…”

Phosphate affects the adsorption of tetracycline on two soils with different characteristics

“…The high rate application of P fertilizer generally causes P accumulation in soils. Phosphate is known to convey negative charges to the soil particle surface (Marchi et al, 2006;Antelo et al, 2007;Guan et al, 2007;Xu et al, 2007), which in turn will decrease the adsorption of anionic pesticides, such as 2,4-D (Vasudevan and Cooper, 2004) and glyphosate (Gimsing et al, 2004;Wang et al, 2005; and other anionic pollutants such as arsenate (Gao and Mucci, 2001). We found that P significantly affected the adsorption behaviors of TC on soils.…”

Adsorption of phthalic acid and salicylic acid and their effect on exchangeable Al capacity of variable-charge soils

“…Salicylic or phthalic acids in solution were measured by ultraviolet spectroscopy with wavelength 304 nm for salicylic acid and 280 nm for phthalic acid, respectively [27]. The recovery of the acids was found to range from 97 to 103%.…”