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Research articles

ScienceAsia 45 (2019): 253-259 |doi: 10.2306/scienceasia1513-1874.2019.45.253

Acid soil amendment by zeolite, sepiolite and diatomite

Chompoonut Chaiyaraksa*, Mintra Tumtong

ABSTRACT:     The aim of this research was to reduce the heavy metal movement to the biosystem using clay minerals including zeolite, sepiolite, and diatomite. The clay soil and sandy loam soil were made contaminated with 200, 350, 700, and 250 mg of Zn, Cu, Cr, and Ni per kg of soil, respectively. The ratio of clay minerals added to soils was 2.5%, 5%, and 7.5%. The determination of various forms of heavy metals bound to soil mixed with clay minerals and left for a period of 30 and 60 days was carried out using the sequential extraction method. The results indicated that Ni and Zn were mostly in an exchangeable form, while Cu and Cr were mostly in an oxide bound form and an organically bound form. The pH of the soils increased after adding clay minerals. Diatomite caused the smallest change in the pH value. Chromium had the best adsorption capacity by bonding with various elements in the soil, followed by Cu, Zn, and Ni, respectively. The addition of sepiolite caused more heavy metals in a stable form than adding zeolite and diatomite. When adding clay minerals to both types of soil, the highest impact was on Ni, followed by Zn, Cu, and Cr, respectively. The bioavailable index (BI) value was the least when adding sepiolite. The risk of heavy metals moving to the biosystem was lower when increasing the incubation time. Without adding any clay mineral, the BI value of metals in the sandy clay loam soil was higher than that in the clay soil.

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a Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520 Thailand

* Corresponding author, E-mail: kcchompoonut@gmail.com

Received 16 Apr 2019, Accepted 20 Jun 2019