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Author: search.filters.author.Chaiyaraksa, ChompoonutSubject: search.filters.subject.Heavy metals

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    Reduction of heavy metal movement in soil contaminated with diesel using Corncob-Biochar
    (2021-01-01)
    Chaiyaraksa, Chompoonut
    ;
    Phumcharoen, Ketklao
    This research aimed to study the effect of biochar on the stability of Mn, Cd, and Pb in soil contaminated with diesel. The clay with pH 6.80, medium in organic matter (OM), high in cation exchange capacity (CEC), low in phosphate and salinity was from Bang Rong Subdistrict, Klong Khuen District, Chachoengsao Province (N13˚50’32.1252” E101˚ 9’5.6808”). The metal content is in the standard for use in agriculture. The soil sample was prepared to contain Mn, Pb, and Cd at 2,000 mg/kg, 550 mg/kg, and 50 mg/kg, respectively. The biochar from corncob was neutral, low in CEC, high in conductivity and OM. The surface area, pore-volume, pore radius, acid neutralization capability, and the pH at the point of zero charges (pHPZC) were 61.189 sq. m/g, 0.088 mL/g, 13.664 Angstrom, 1,000 meq/kg, and 6.80, respectively. Five percent of biochar was mixed to the soil containing 2% and 5% of diesel at room temperature for 2, 4, and 8 weeks before extraction with diethylenetriaminepentaacetic acid (DTPA) and sequential extraction. The results indicated that the higher the amount of diesel in soil, the slower the metal movement. Biochar could retard the mobility of Mn, Pb, and Cd in the soil sample. Five percent of biochar was not enough to decrease the metal mobility in soil contaminated with diesel 5%. The amount of extracted heavy metals increased with the more extended mixing period. The addition of biochar to the soil sample could change metals from unstable to stable forms.
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    Mobility retardation of Cd, Pb and Mn in acid soil using phosphate fertilizers
    (2019-05-01)
    Chaiyaraksa, Chompoonut
    ;
    Rodsa, Natthanan
    Contamination of heavy metals in soil is a major problem that causes damage to the environments. The aim of this research was to observe the efficiency of phosphate fertilizer, including phosphate rock, di-ammonium phosphate, and monopotassium phosphate in stabilizing lead, cadmium, and manganese in contaminated soil. The sampling soil was an acid sandy clay loam soil from Rayong Province which is one of the most industrialized provinces in Thailand. After applying fertilizers to the soil, the determination was on soil pH, the total concentration of heavy metals, heavy metal forms in soil and potential of heavy metals to enter the biological system. The results showed that phosphate rock, diammonium phosphate, and monopotassium phosphate increased the soil pH from 3.60 to 6.5, 7.0 and 5.2, respectively. Phosphate fertilizers could change an unstable form to a more stable form of heavy metals. Phosphate rock (7.5 g/kg<inf>soil</inf>) has the highest potential for reducing the mobility of all three metals (about 80% for manganese, 60% for cadmium, and 50% for lead), followed by monopotassium phosphate. The results obtained from the extraction with DTPA and CaCl<inf>2</inf> were closely related to the results obtained from the sequential extraction method. Phosphate rock was the best to reduce potentially toxic metals phytoavailability. Soil improvement with phosphate fertilizer was considered a good alternative for stabilizing soils contaminated with cadmium, lead, and manganese.
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    Acid soil amendment by zeolite, sepiolite and diatomite
    (2019-01-01)
    Chaiyaraksa, Chompoonut
    ;
    Tumtong, Mintra
    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.