Chemistry of Iron Sorption-Desorption in Three Different Soils of Bangladesh

Abstract

A laboratory incubation experiment was conducted for ascertaining the chemistry of iron sorption-desorption among the three different soils, namely calcareous ‘Ishurdi series' and non calcareous ‘Amjhupi' and ‘Dhamrai series'. The sorption- desorption behavior was observed under three different iron treatments-0.5 ppm, 1.00 ppm and 2.5 ppm, while the sorption chemistry was studied for 2, 4, 6, 24 and 48 hour of incubation and desorption chemistry was done for 2, 4, 6 and 24 hour of extraction with 0.1N EDTA solution followed by 6 and 24 hour of incubation with different treatments (0.5 ppm, 1.00 ppm and 2.5 ppm) of iron solution. Maximum iron sorption of 35.72 ppm was found for the calcareous Ishurdi soil after 48 hour followed by the non calcareous Amjhupi and Dhamrai soil. There may be higher chemisorption and/or complexation reaction which are favored under conditions provided by the calcareous soils and this might be the reason for greater sorption in Ishurdi soil. The desorption study showed that with increasing extraction period (from 2hour to 24 hour) iron desorption increases. But with increasing sorption incubation period from 6 hour to 24 hour, iron desorption decreases for all the three soils. Concentration of iron in the soil solution and soil properties such as pH, clay content and calcareousness might have positive influence on iron sorption- desorption chemistry. Thus most significant iron desorption was observed for non calcareous soils, Amjhupi (r=0.9988) and Dhamrai (r=0.9986) soil, followed by calcareous Ishurdi soil (r=0.9779).