The influences of four heating rates on the combustion and pyrolysis behavior in the N₂ and air atmosphere were investigated by the Fourier transform infrared spectrometry (FTIR) and thermogravimetric (TG) analysis. the distributed activation energy model (DEAM) and Flynn-Wall-Ozawa (FWO) were used to estimate Ea and A, ΔH, ΔG and ΔS. Experimental results showed that the similar thermal behavior emerged, but the temperatures in the air and N₂ atmospheres representing the end of the reaction were about 500 °C and 550 °C, respectively. The results of FTIR showed the peak positions were basically the same, but the concentrations of aromatics, aldehydes and ketones produced by pyrolysis in the N₂ atmosphere were higher. When the heating rate was 20 K/min, the comprehensive combustion parameters were 56.442 and 6.871 × 10⁻⁷%²/(min²• K³) in the air and N₂ atmospheres, respectively, indicating that the peanut shells had great potential to become bioenergy.

The feasibility of removal of sulfate ions from the sodium alkali FGD wastewater using the ettringite precipitation method was evaluated. Factors affecting the removal of sulfate ions, such as NaAlO₂ dosage, Ca(OH)₂ dosage, solution temperature, anions (Cl⁻, NO₃⁻ and F⁻), and heavy metal ions (Mg²⁺ and Mn²⁺), were investigated, and the optimal experimental conditions for the removal of sulfate ions were determined. Experimental results indicate that the ettringite precipitation method can effectively remove SO₄²⁻ with removal efficiency of more than 98%. All the investigated factors have influences on the removal of sulfate ions, and among them, the dosage of reagents, solution temperature, and fluoride ions have the strongest influence. In addition, the method can effectively synergistically remove F⁻ and heavy metal ions with removal efficiencies of more than 90% and 99%, respectively; meanwhile, Cl⁻ and NO₃⁻ also can be removed minimally by the method. The result of actual wastewater treatment shows that the method is feasible for treating high-concentration sulfate wastewater. The ettringite precipitation method has the potential to be a commercial application in the future.

The desulfurization and denitrification wastewater (DDW) from the wet flue gas treatment project is difficult to be treated and recycled because of high chloride ion (Cl⁻) concentration. Cl⁻ can cause equipment and piping corrosion. However, there is a lack of cost-effective treatment technologies for the removal of Cl⁻ from the DDW. In this research, the feasibility of Cl⁻ removal from the DDW using Friedel’s salt precipitation method was evaluated. Factors affecting the Cl⁻ removal, such as Ca(OH)₂ dosage, NaAlO₂ dosage, solution’s initial pH, solution’s temperature, reaction time, stirring speed, and anions (SO₄²⁻, NO₃⁻, and F⁻), were investigated, and the optimal experimental conditions for Cl⁻ removal were determined. Experimental results showed that Friedel’s salt precipitation method can remove Cl⁻ effectively and can achieve synergistic removal of SO₄²⁻, F⁻, and heavy metal ions. Under the best experimental conditions, the average removal efficiencies of Cl⁻, SO₄²⁻, F⁻, and heavy metal ions reach more than 85%, 98%, 94%, and 99%, respectively. The Cl⁻ removal mechanism studies showed that Cl⁻ can be removed by precipitation as Ca₄Al₂Cl₂(OH)₁₂. The purified wastewater and the precipitated solid can be reused to reduce the consumption of water and alkali. Friedel’s salt precipitation method is an effective control technology for the synergistic removal of Cl⁻, SO₄²⁻, F⁻, and heavy metal ions and has enormous potential to be applied in the industrial wastewater treatment field.

In this work, the feasibility of the simultaneous removal of NO_x and SO₂ through a simple process using a composite absorbent (NaClO₂/Na₂S₂O₈) was evaluated. Factors affecting the removal of NO_x and SO₂, such as NaClO₂ and Na₂S₂O₈ concentrations, solution temperature, the initial pH of solution, gas flow rate, and SO₂, NO, and O₂ concentrations were studied, with a special attention to NO_x removal. Results indicate that a synergistic effect on NO_x removal has been obtained through combination of NaClO₂ and Na₂S₂O₈. NaClO₂ in the solution played a more important role than did Na₂S₂O₈ for the removal of NO_x. The above factors had an important impact on the removal of NO_x, especially the solution temperature, the initial pH of the solution, and the oxidant concentrations. The optimum experimental conditions were established, and a highest efficiency of NO_x removal of more than 80% was obtained. Meanwhile, tandem double column absorption experiments were conducted, and a NO_x removal efficiency of more than 90% was reached, using NaOH solution as an absorbant in the second reactor. A preliminary reaction mechanism for NO_x and SO₂ removal was deduced, based on experimental results. The composite absorbent has the potential to be used in the wet desulfurization and denitration process, to realize the synergistic removal of multi-pollutants.

The effects of ozone concentration, NaOH concentration, type and concentration of additives, initial pH, temperature, and NO and SO₂ concentration on simultaneous removal of NO and SO₂ were studied through ozone oxidation combined with wet absorption. Results indicated that ozone concentration and the type and concentration of additives had the most significant effect on NO removal. The optimal ozone concentration was 250 ppm (NO/NO₂ = 1), and the best additive was KMnO₄. The removal efficiency of NO_x was as high as 97.86% when NO/NO₂ = 1, and the concentration of KMnO₄ was 0.025 mol/L. Considering economic and other factors, the KMnO₄ concentration was selected to be 0.006 mol/L. At this time, the removal efficiencies of NO_x and SO₂ were 81.35 and 100%, respectively. This method has potential application prospects for simultaneous removal of SO₂ and NO in the industrial flue gas.