Removal of nitric oxide using combined Fe II EDTA and coal slurry in the presence of SO 2

Arsenic removal from coal by ferric chloride enhanced leaching under ultraviolet irradiation during flue gas desulphurization with coal slurry

During coal combustion, the harmful element arsenic can be released into environment and cause potential significant harm to human beings. Therefore, it is very important to study the removal of arsenic from coal before combustion. In this work, simulated SO2-containing flue gas was used to leach arsenic from coal in a 1 L UV photoreactor. The effects of FeCl3, ultraviolet (UV), pH and the Cl-/Fe3+ molar ratio on arsenic leaching and SO2 removal were experimentally investigated and the enhancing mechanism was analysed. Experimental results demonstrated that FeCl3 and UV could efficiently increase iron and arsenic leaching percentages and SO2 removal efficiency. UV irradiation could induce the oxidation of most trivalent arsenic. The arsenic leaching percentage was significantly larger than that of iron. Low pH was favourable for iron and arsenic leaching. The optimal Cl-/Fe3+ molar ratio was determined to be 3:1. The introduced ferric chloride could not only increase the concentrations of free radicals and ferric iron oxidants, the chloride ion might also impede the formation of passive coatings, thus increasing the arsenic leaching percentage, intensifying the oxidation of trivalent arsenic and enhancing the removal of SO2.

Spontaneous intra-electron transfer within rGO@Fe2O3-MnO catalyst promotes long-term NOx reduction at ambient conditions

Iron (Fe)-based catalysts are widely used for taming nitrogen oxides (NO_x) containing flue gas, but the regeneration and long-term reusability remains a concern. The reusability can be acquired by external additives, and resultantly can not only increase the cost but can also add to process complexity as well as secondary pollutants. Herein, a self-sustainable material is designed to regenerate the catalyst for long-term reusability without adding to process complexity. The catalyst is based on reduced graphene-oxide impregnated by Fe₂O₃-MnO (rGO@Fe₂O₃-MnO; G-F-M) for spontaneous intra electron (e^-)-transfer from Mn to Fe. The developed catalyst; G-M-F exhibited 93.7% NO_x reduction, which suggests its high catalytic activity. The morphological and structure characterizations confirmed the Fe/Mn loading, contributing to e^--transfer between Mn and Fe due to its conductivity. The synthesized G-F-M showed higher NO_x reduction about 2.5 folds, than rGO@Fe₂O₃ (G-FeO) and rGO@MnO_x (G-MnO_x). The performance of G-M-F without and with an electrochemical system was also compared, and the difference was only 5%, which is an evidence of the spontaneous e^- transfer between the Mn and Fe-NO_x complex. The designed catalyst can be used for a long time without external assistance, and its efficiency was not affected significantly (<3.7%) in the presence of high oxygen contents (8%). The as-prepared G-M-F catalyst has great potential for executing a dual role NOx removal and self-regeneration of catalyst (SRC), promoting a sustainable remediation approach for large-scale applications.

Promoting Effect of H+ and Other Factors on NO Removal by Using Acidic NaClO2 Solution

In this study, NaClO2 was selected as a denitration oxidant. In order to clarify the mechanism of NaClO2 as an oxidation agent for NO removal efficiency, the effects of H+ and other factors (NaClO2 concentration, temperature, and the other gas) on the NO removal efficiency were investigated. NaClO2 showed a promotional ability on NO removal, whose efficiency increased with the increase of NaClO2 concentration. One hundred percent removal efficiency of NO could be achieved when the NaClO2 concentration was 0.014 mol/L. Furthermore, raising the reaction temperature benefited the removal of NO. The lower the pH, the better the NO removal efficiency. The promoting effect of H+ on the NO removal was studied by the Nernst equation, ionic polarization, and the generation of ClO2. Under the optimal conditions, the best removal efficiency of NO was 100%. Based on the experimental results, the reaction mechanism was finally speculated.

Simultaneous Biological and Chemical Removal of Sulfate and Fe(II)EDTA-NO in Anaerobic Conditions and Regulation of Sulfate Reduction Products

In the simultaneous flue gas desulfurization and denitrification by biological combined with chelating absorption technology, SO2 and NO are converted into sulfate and Fe(II)EDTA-NO which need to be reduced in biological reactor. Increasing the removal loads of sulfate and Fe(II)EDTA-NO and converting sulfate to elemental sulfur will benefit the application of this process. A moving-bed biofilm reactor was adopted for sulfate and Fe(II)EDTA-NO biological reduction. The removal efficiencies of the sulfate and Fe(II)EDTA-NO were 96% and 92% with the influent loads of 2.88 kg SO42−·m−3·d−1 and 0.48 kg NO·m−3·d−1. The sulfide produced by sulfate reduction could be reduced by increasing the concentrations of Fe(II)EDTA-NO and Fe(III)EDTA. The main reduction products of sulfate and Fe(II)EDTA-NO were elemental sulfur and N2. It was found that the dominant strain of sulfate reducing bacteria in the system was Desulfomicrobium. Pseudomonas, Sulfurovum and Arcobacter were involved in the reduction of Fe(II)EDTA-NO.