Effect of Additive Material on Controlling Chromium (Cr) Leaching from Coal Fly Ash

Abstract

Coal fly ash contains a considerable number of toxic elements that can be leached into the environment, such as chromium (Cr), thereby quickly leading to severe contaminations. In this research, the leaching behaviors of Cr were analyzed from 14 kinds of coal fly ash samples collected from the electrostatic precipitators of coal-fired thermal power plants in Japan. The level of Cr concentration found in the samples varied from 0.00 to 82.93 μg/L. However, Cr toxicity depends on its valence state; Cr6+ is more toxic than Cr3+. Additive materials containing high calcium content were used to control the leaching concentration of Cr, such as Ca(OH)2, paper sludge ash, and blast furnace cement. This research used several instruments. An X-ray fluorescence was adopted to measure the major chemical composition of the fly ash samples and the additive materials. A thermogravimetric analyzer was used to examine the calcium compounds in the additive materials. Inductively coupled plasma was used to determine the Cr leaching concentrations from the fly ash samples. Findings showed that the three-additive mixture had a promising effect on controlling the Cr leaching concentrations. These results were also supported by FactSage 7.2 simulation.

Heavy Metals and Metalloids Leachability from Composite Ground Materials Peat – Fly Ash – Lime

“…Based on the results of studies as well as literature of the subject, it can be concluded that the low leachability of heavy metals and metalloids is related to the high pH value (Desfitri et al 2020, Leelarungroj et al 2018. The reduction of heavy metals can also be the result of a pucolanic reaction and the formation of the CSH phase and ettryngite (Leelarungroj et al 2018, Liu et al 2018.…”

A Role of Mineral Oxides on Trace Elements Behavior during Pulverized Coal Combustion

“…At T < 1200 °C, Cr2O3, and CrO2 were formed in the solid phase. Cr becomes volatile only at high combustion temperatures, and gaseous species leave the combustion zone and cooling condition [20,22]. The effect of mineral oxides on Cr, the presence of Ca and K make Cr less volatile due to the formation of CaCr 2 O 4 and K 2 CrO 4 , and the effect of Al 2 O 3 , Fe 2 O 3 , MgO is not affected on Cr as shown in Figure 3a-e.…”

“…Barbulescu et al, 2019 [15] It is necessary to understand TEs behavior during the coal combustion and gasification processes. Using the computation method of the thermodynamic equilibrium, lots of research has been studied TEs behavior and transformation during combustion and/or gasification process [16][17][18][19][20][21][22][23]. Liu et al [21] investigated the effects of sewage sludge (SS) co-combustion conditions and interactions with Al 2 O 3 , CaO, Fe 2 O 3 , and SiO 2 .…”

“…At T < 1200 • C, Cr 2 O 3 , and CrO 2 were formed in the solid phase. Cr becomes volatile only at high combustion temperatures, and gaseous species leave the combustion zone and cooling condition [20,22].…”

Influence of Blending High-Calcium Additive on Environmental Safety of B, F, and Se: A Case Study from Thermodynamic Calculation

“…In addition, the temperature during the leaching process also affects the leaching of trace elements from fly ash at temperatures above 30 • C, and the trace elements are stabilized completely, regardless of the pH [16]. For the development of additives that inhibit the leaching of trace elements into the environment, a previous study found that calcium helps to decrease the trace element leaching concentration; the application of mixture-based additives (PS ash + cements + Ca(OH) 2 ) had a promising effect in terms of inhibiting the leaching of several trace elements, including by controlling the leaching of As, B, Cr, F, and Se [17][18][19].…”