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Adsorption of Lead (pb)by Soils and Their Clay Fraction

J. C. JOARDAR
Department of Soil, Water and Environment, University of Dhaka, Dhaka

M. H. RASHID
Department of Soil, Water and Environment, University of Dhaka, Dhaka

S. M. IMAMUL HUQ
Department of Soil, Water and Environment, University of Dhaka, Dhaka

Abstract/ Executive Summary:

Adsorption of lead by three soils and their clay fraction were studied separately with three soil series viz. Ghior (high clay content), Ghatail (medium clay content) and Rajoir (organic soil). The maximum amount of lead was adsorbed by Ghior soil followed by the Ghatail soil while the minimum was adsorbed by the organic Rajoir soil. Variations in adsorption among the soils were attributed to the content and nature of the clay fraction, presence of organic matter, iron content and magnitude of CEC. Adsorption of lead by clay fraction of the corresponding soils showed a different trend to that of adsorption of lead by the whole soil. The order was Rajoir > Ghatail > Ghior soils. The extent of adsorption appeared to have varied with the variation of mineral types in the clay fraction of the soils.

Keywords: Adsorption, lead, clay mineralogy

Location: Mymensingh, Madaripur and Gopalgonj

Start Date:

End Date:

Program Area: Knowledge Management

Commodity: Contamination of soil

Objectives:

The aim of the present work was to investigate the adsorption of lead in a few selected soils of Bangladesh and the clay fraction thereof as potential binding agents.

Methodology:

Two mineral soils and one organic soil were used in the present research work . The soils were collected from three districts (Mymensingh, Madaripur and Gopalgonj) of Bangladesh. The soils collected represent the Ghatail (Mymensingh), Ghior (Madaripur), and Rajoir (Gopalgonj) series. After collection, the soils were air dried and ground to pass through a 2 mm sieve. The bulk sample was thoroughly mixed and stored. Particle size analysis was performed by hydrometer method (Day 1965). The textural class was determined by following Marshall's triangular co-ordinates USDA (1951) . Soil pH was measured by a combined electrode pH meter at a soil : water ratio of 1 : 2.5 Jackson (1973). The total lead content was extracted by aqua regia (3 : 1, HCI : HN0₃). The samples were digested for approximately 4 - 5 hours, using a sand bath as a heating source and the water soluble Pb was extracted by shaking 10 g samples of soil with 50 ml distilled water at a 1: 5 soil water ratio for 24 hours. After dissolution, samples were diluted to volume, mixed and filtered prior to analysis (Portman and Riley 1964). Then, the lead content in the extracts was estimated by Atomic Absorption Spectrophotometer following calibration of the equipment. With every set of digestion a blank and a spiked sample were included to ensure the QA/QC. Soil clay fractions were separated by the method of Jackson (1975). The following two groups of potential adsorbent materials were selected for the lead adsorption test: (i) Soils (Ghatail, Ghior and Rajoir): On the basis of their clay content. (ii) Clays (Separated from the selected soils).

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 31(1): 63-74, June 2005

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The values of adsorption maximum increased with decreased proportion of illite and montmorillonite minerals in the soil clays. This is evident by the fact that clay of Rajoir soil, containing less amounts of illite and montmorillonite, has b values of 1864.68 as compared to the values of 1370.29 and 1263.68 observed for clays of Ghatail and Ghior soils which contained higher amount of illite and montmorillonite respectively. The clay content and the nature of minerals present should be considered when predicting the lead adsorptive capacity of a soil and clarifying interaction of lead and soil.

Knowledge Management: Journal