Preparation of CeO₂/CaO with Anti-sintering for Efficient Capture of As₂O₃ from Flue Gas at a High Temperature

Abstract

Arsenic emissions from coal-fired power plants are highly toxic and volatile, posing a serious threat to human health and the natural environment. The removal of arsenic from coal-fired flue gases has attracted widespread attention worldwide. Calcium-based sorbents can capture arsenic, thus solving the environmental problem of heavy metal arsenic pollution from coal-fired power plants, but its sintering and low capture efficiency impede its application. Doping CaO with CeO2 is an efficient technique to improve resistance to sintering and facilitate capture efficiency. In this study, the CeO2/CaO sorbent was synthesized by the sol–gel method and then carried out in the flue gas at high temperatures from 600 to 900 °C to capture gaseous arsenic. The introduction of CeO2 not only reduces the grain size of CaO, but uniformly dispersed CeO2 forms a barrier layer that effectively prevents the growth and sintering of CaO grains. As a result, the sintering resistance of the sorbent is enhanced, and the sorbent exhibits excellent thermal stability. On the basis of characterization analysis, lattice oxygen provided by cerium oxide greatly promotes the reaction process of As­(III) oxidation to As­(V). The experimental results demonstrate that CeO2/CaO possesses the highest arsenic capture capacity compared to untreated CaO and CeO2. With the increase of the temperature, the capture efficiency of CeO2/CaO increases and reaches a maximum of 1.90 mg/g at 900 °C. Additionally, the density functional theory (DFT) was further used to study the adsorption energy of untreated CaO and CeO2/CaO. The results exhibited that CeO2/CaO has stronger adsorption capacity for As2O3. Finally, the adsorption mechanism of As2O3 on CeO2/CaO was proposed. As a result of the excellent anti-sintering property and high capture capacity, CeO2/CaO is expected to be an excellent sorbent for arsenic removal from coal combustion flue gas.

Thermodynamic research on the effect of CaO on the transformation of arsenic and sulfur in coal in different pyrolysis atmospheres

“…Even though there are numerous pieces of literature about the effect of Ca on arsenic 2,4,23,28 or sulfur [34][35][36][37][38] separately, there are not too many papers about the effect of Ca on arsenic and sulfur together. The current related literature includes experimental work, 6,11,21,39 thermodynamic equilibrium calculation, 40 and kinetic behavior.…”

“…Arsenic stays with a particular matter, which goes to the environment as ash. There are a few technologies to control its release, such as coal washing before combustion, arsenic capture sorbent, 2–4 and so forth. Besides, atmosphere and temperature have a great effect on arsenic distribution during the reaction 5 .…”

Nickel-Doped CaO to Improve Its Antisintering Property and Electron-Transfer Ability for the Removal of As2O3 from Flue Gas: Experiments and DFT Simulations

“…In the adsorption apparatus depicted in Figure 1, 33 simulated arsenic adsorption tests were conducted. Two important components of the system are the fixed bed and the arsenic generator.…”

“…Diagram showing the formation and adsorption of arsenic vapor. Reproduced with permission from ref . Copyright 2021.…”