An experimental study on the simultaneous removal of NO and SO2 with a new wet recycling process based on the micro-nano bubble water system.

The micronano bubble water system (MNBW) generated by a micronano bubble generator (MNBG) has the superior oxidation properties and can improve gas solubility. In the study, a new wet recycling process based on MNBW is proposed to simultaneously remove nitric oxide (NO) and sulfur dioxide (SO2). The important experimental parameters such as initial water pH, initial water temperature, NO and SO2 concentrations, and the presence of oxygen (O2) were investigated to explore the feasibility of desulfurization and denitration with MNBW. The experimental results showed that decreasing initial water pH or increasing initial water temperature and NO and SO2 concentrations were not conducive to the removal of NO or SO2. O2 could promote the removal of NO, but it had no effect on SO2 removal. In addition, SO2 removal efficiency always remained high and did not change obviously during the experimental period. However, NO removal efficiency gradually decreased in the first 50 min and then became stable.

Effects of nZVI dosing on the improvement in the contaminant removal performance of constructed wetlands under the dye stress.

In this study, different dosages of nanoscale zero-valent iron (nZVI) were used to improve the nitrogen removal efficiency in CWs under different C/N ratios and dye stress conditions. The addition of nZVI enhanced the dye and nitrogen removal efficiencies in constructed wetlands (CWs) through chemical reduction and biological denitrification processes. However, total nitrogen (TN) and dye removal efficiencies firstly increased and then decreased with the increases of the nZVI dosage and influent COD/N (C/N) ratio. Under the influent C/N ratio of 5, the higher TN removal efficiencies (80.2%, 55.1%, and 69.14% under 25 mg/L, 50 mg/L, and 75 mg/L dye concentration, respectively) and higher COD removal efficiencies (48.3%, 74.95%, and 30.76% under 25 mg/L, 50 mg/L, and 75 mg/L dye concentration, respectively) were obtained in CWs by adding the optimal nZVI dosage (0.1 g/L). The dye removal efficiencies in CWs with nZVI at C/N = 1 (75%-91%) and at C/N = 5 (81%-97%) were all significantly higher than that in CWs without nZVI (60%-82%). Moreover, the functional bacteria for nitrogen removal in denitrification and the dye degradation (Zoogloea and Acinetobacter) were enriched in CWs with 0.1 g/L nZVI.

The grain growth mechanism of nano-CaO regenerated by nano-CaCO3 in calcium looping.

The grain growth mechanism of nano-CaO-based CO2 adsorbents in calcium looping (CaL) process was studied to figure out the main factors affecting sorption durability. First, the thermal growth characteristics of nano-CaCO3 grains and nano-CaO grains at 750-850 °C was measured to fit the grain growth kinetic models. The activation energy data of grain growth of nano-CaCO3 and nano-CaO were obtained as 104.8 kJ mol-1 and 212.8 kJ mol-1 respectively, which indicated that the grain growth of nano-CaCO3 was easier than that of nano-CaO. Then, the grain sizes of regenerated nano-CaO undergoing 10 CaL cycles were compared with those derived from nano-CaCO3 suffering high temperature heat-treatment under the same looping temperature and time. It was found that CaCO3-CaO chemical conversion could accelerate the grain growth of regenerated nano-CaO. Based on these results, the grain growth mechanism of regenerated nano-CaO grain in CaL process was proposed. The thermal growth of nano-CaCO3 grain was the key issue to influence the grain growth of regenerated nano-CaO. Therefore, shortening the high temperature residence time as well as preventing the interface contact of nano-CaCO3 grains were good for limiting the grain growth of regenerated nano-CaO.