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.
The issues of trace element emissions during coal combustion has been a concern in recent years due to their environmental pollutant. To study the trace element transformation, the thermodynamic calculation (FactSage 7.2) was used. Five kinds of pure mineral oxides (Al2O3, CaO, Fe2O3, K2O, and MgO) and As, B, Cr, F, and Se in fly ash were considered for trace elements. The results confirm that all mineral oxides have a good correlation with arsenic to form Ca3(AsO4)2, FeAsO4, K3AsO4, and Mg3(AsO4)2. Boron has a good relationship with Al, Ca, and Mg to form (Al2O3)9(B2O3)2, Ca3B2O6, and Mg3B2O6. Chromium has a good correlation with K and Ca to form K2CrO4, CaCr2O4. Furthermore, FeF3(s) KF(s), and AlF3(s) are predicted from the interaction of fluorine with Fe2O3, K2O, and Al2O3. The effect of mineral oxides on selenium partitioning are not observed. The inhibition order of trace elements by mineral oxides is as follow: As (Al2O3 > MgO > CaO > Fe2O3 > K2O), B (Al2O3, CaO, Fe2O3, K2O, > MgO), Cr (CaO > K2O > Al2O3, MgO, Fe2O3), F (CaO > MgO > Al2O3 > Fe2O3 > K2O). The results will be useful to control the trace element emissions.
Inductively coupled plasma system was used in drinking water treatment system to kill the microorganisms in water such as total coliforms (TC), fecal coliforms (FC) and other coliforms (OC) from river water. The aim of this study was to investigate the effect of flowrate on removal efficiency (RE), death rate, and death yield and energy consumption of bacteria's. The frequency of the system was set at 4.6 MHz. The results show that the removal efficiencies and death rate of TC, FC and OC decreased with increasing flowrate. Compared to FC, the first-order reactions of TC and OC were lower in the following order: FC > OC > TC. The death yield of TC and OC significantly increased when the removal efficiency increased. The electromagnetic flux varied from 19.44 to 20.55 W/cm2 and the energy consumption was 0.26, 0.32, and 0.67 with flow rate at 20, 10 and 5 mL/minute, respectively. These results are very necessary to improve drinking water treatment.
The leaching process of arsenic (As) from coal fly ash collected from the coal-fired power plant in Japan was investigated with six different kind of paper sludge ashes (PS ash XA, XB, XC, YA, YB, and YC) as an inhibitor and their mass addition ratio 0 to 30%. To study the arsenic leaching mechanism, thermodynamic calculation (FactSage 7.2) was used to predict the possible As-bearing compounds in the fly ash and its distribution during the combustion and leaching process. The results indicated AlAsO4(s) was the most probable species resulting compound from arsenic interaction with fly ash components under the combustion process. PS ash YB containing the highest calcium content shows a considerable immobilization ability for arsenic due to arsenic reaction with calcium compound in the leaching process. CaO in PS ash generates high pH leachate during the leaching process and promotes calcium with arsenic to form a precipitate. The arsenic leaching ratio by thermodynamic calculation and experimental, again PS ah YB, shows the best effect in the arsenic leaching concentration with addition ratio in the range 15-30%. It was found that the arsenic fixation capacity of PS ash increases as the calcium content in PS ash increases because the chemical reaction between calcium compounds and arsenic is accelerated during the leaching process. Predicting arsenic species based on the combustion and leaching process will be useful to choose the best available control technology to minimize the effect of arsenic into the environment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.