Monira Begum and SM Imamul Huq,
Keywords: Calcareous, non-calcareous, sorption, desorption, desorptivity, residence time.
Abstract: A laboratory batch experiment was conducted using calcareous (Ishurdi series) and non-calcareous soils (Amjhupi and Dhamrai series) to evaluate the desorption pattern of arsenic under three viz.,5, 10 and 20 ?g ml-1 imposed treatments of arsenic. The desorption was observed at 2, 4, 6, 8 and 24 hour residence time with arsenic solution followed by 2, 4, 6 and 24 hour of extraction to release the sorbed arsenic with 0.1 N EDTA solution. Average percent desorption of arsenic decreased with increasing residence time from 2 hour to 8 hour of arsenic sorption irrespective of the calcareousness of the soil. 87.21 % of the sorbed arsenic desorbed back into the solution for the 2 hour sorbed one and the minimum of 3.88 % desorbed for the 8 hour sorption. Quantity wise, a maximum of 9.49 ?g g-1 As was found to have desorbed from soils having 24 hour of sorption that amounted to 11.4 % of the amount sorbed. Desorption of As was more in the non-calcareous Dhamrai soil. Although the highest imposed treatment of arsenic (20 ?g ml-1) caused the highest desorption, the desorptivity of the element however, did not vary widely with solute concentration.
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