Use of dilute boric acid for cation desorption from soils under an external electric field

Abstract

Electro‐ultrafiltration (EUF) of soils ‐ a combination of electrodialysis and ultrafiltration ‐ which works on the principle of extraction of nutrient ions from soils under an external electric field, can be employed as a useful method in soil fertility work to characterize the desorption parameters of soil nutrients. With a view to improving the efficiency of extraction of Mg, but mainly to prevent the precipitation of Mg(OH)₂ in the membrane separating the soil suspension from the cathode 0.05 M H₃BO₃, was used instead of distilled water in the EUF analysis of pure Mg solutions and different soils. The recovery of Mg from solutions was improved by using boric acid. But the objective of preventing the deposition of Mg(OH)₂ in the membrane was not fully achieved. With soils the desorption characteristics of K, Ca and Mg were appreciably affected. The addition of boric acid enhanced the desorption rate for all three elements; the most for Ca and the least for K. The effect of boric acid on the precipitation of Mg(OH)₂ in the membrane was not straightforward. Only in two cases a reduction was achieved.