Properties of Fly Ashes from Thermal Power Stations in Relation to Use as Soil Amendments

Abstract

Recycling fly ashes is a good alternative to disposal with the significant economic and environmental benefits. Characterization of fly ashes can be helpful to evaluate their use potentials. This study aimed to investigate the physical, chemical and mineralogical properties of fly ashes from five thermal power stations in Northern Vietnam in relation to use as sandy soil amendments. The results showed that the fly ashes were dominated by silt-sized and spherical particles and had low bulk densities. There was almost not significant difference in the surface charges among the fly ashes; however, their surface areas varied widely. The fly ashes were alkaline. The electrical conductivity and cation exchange capacity in the fly ashes were higher than those in the sandy soil. The concentrations of extractable K, P, Ca 2+ and Mg 2+ in the fly ashes were higher compared with the sandy soil. The major matrix elements in the fly ashes were Si, Al, and Fe together with significant percentages of K, Mg, Ca and Ti. Quartz was the most predominant mineral present in the fly ashes. Several radioactive elements were found in the fly ashes with very low concentrations. The potential to release trace elements from the fly ashes was below the regulatory guidelines. The amendment of fly ashes to the sandy soil led to the substantial decrease in the hydraulic conductivity but the increase in the plant-available water contents of the sandy soil. It is recommended to use the fly ashes as soil amendments for sandy soil amelioration.

Study on the Application of Fly Ash for Soil Amelioration

“…Figure 3 shows that these fine particles were aggregated into micron and sub-micron sizes. This result is compatible with previous reports about fly ash (Khairul Nizar et al, 2014;Thien et al, 2019). Based on these special properties, it is believed that adding fly ash as an amendment to low texture soils might change the soil's properties, such as the water holding capacity, cation exchange capacity, water movement, and bulk density (Pathan et al, 2003).…”

“…Physically, different natural coal and combustion conditions will create different properties of produced fly ash. However, very fine particles with a low to medium bulk density as well as a high surface area (Thien et al, 2019) have been considered as an amendment for altering the light texture, enhancing the water capacity, and improving the cation exchange capacity of soils. Agricultural utilization of fly ash has been proposed because of its considerable content of elements.…”

“…Chemically, fly ash is rich in many macro and micro plant nutrients, including a high content of Si, Al, Fe, Ca, Mg, Na, and K (Korniejenko et al, 2019), and other trace elements such as B, Mo, S, Se, and Sr (Zierold & Odoh, 2020). Fortunately, heavy metal and radioactive element concentrations in most fly ash produced in Vietnam are below the permissible limits of QCVN 03-MT:2015/BTNMT for heavy metals such as As, Cd, Pb, Cu, and Cr (Sushil & Batra, 2006;Le Van Thien et al, 2016) and lower than the soluble threshold limit concentration for radioactive elements (Jambhulkar et al, 2018;Thien et al, 2019). In Vietnam, fly ash from the Pha Lai thermal power plant has been used as an ameliorant in coastal sandy soil.…”

“…In Vietnam, fly ash from the Pha Lai thermal power plant has been used as an ameliorant in coastal sandy soil. The results showed that fly ash significantly improved the moisture-holding and the acidity and cation exchange capacities (CEC) as well as the content of macronutrients of grey and sandy soils (Nguyen Thi Bich Ngoc, 2012;Le Van Thien et al, 2016;Thien et al, 2019). In this study, fly ash collected from the Mong Duong 2 power plant was added to sandy soil at different levels to investigate how this fly ash influences the physical and chemical properties of the soil as well as the productivity of experimental plants (soybean).…”

Effect of fly ash amendment on sandy soil properties and peanut yields

“…FA was derived from pulverized fuel coal combustion and captured by the emission control device. Properties of FA were previously described [7]. Briefly, the proportion of silt-sized particles was 75.88%.…”