Search

The development of low-temperature aluminum electrolysis makes it possible to reduce energy consumption and greenhouse gas emissions. The KF-NaF-AlF3-based electrolyte is a promising low-temperature electrolyte for aluminum reduction. The liquidus temperatures of KF-NaF-AlF3 electrolytes with a total cryolite ratio (CRt) fixed at 1.3–2.0, and with different concentrations of NaF (with a step change of 5 mol.%), were investigated by the cooling curve method. The results showed that the liquidus temperature of KF-NaF-AlF3 mixtures increases with the increase of the CRt, which has a bigger influence on the liquidus temperature than the traditional NaF-AlF3 electrolyte currently used in aluminum smelters. When the content of NaF is 10–20 mol.%, the curves of the liquidus temperature vs. NaF content reach a peak. When the NaF content ranges from 30 to 40 mol.%, the liquidus temperature is relatively low (695–900°C). The precipitated order of the compounds in molten KF-NaF-AlF3 electrolytes with a CRt of 1.3 is as follows: K2NaAlF6 (or K3AlF6) → Na3Al5F14 → K2NaAl3F12 → KAlF4.

The cryolite ratio (CR) is an important parameter for the electrolyte in aluminum reduction cells. The measurement method for the CR of the KF-NaF-AlF3 system acid (CR

Honeycomb cordierite-based Mn–Ce/Al2O3 (Mn–Ce/Al2O3–C) and Fe–Mn–Ce/Al2O3 (Fe–Mn–Ce/Al2O3–C) catalysts were prepared by an impregnation method and investigated in low-temperature selective catalytic reduction (SCR) of NO with NH3 at 100 °C. The Fe–Mn–Ce/Al2O3–C catalyst exhibited not only higher catalytic activity, but also much better SO2 and H2O resistance in the presence of 30 ppm SO2 and/or 5 vol% H2O than Mn–Ce/Al2O3–C. After doping Fe, the NO conversion of Mn–Ce/Al2O3–C catalyst displayed an increasing trend from 79 to 84% in the absence of SO2 and H2O at 100 °C under a gas hour space velocity of 1667 h−1. The results of characterization indicated that addition of Fe was advantageous to increase BET surface area, pore volume and inhibit loss of surface Mn and Ce species. Additionally, it was helpful for generating higher concentration of Mn4+, more chemisorbed oxygen and more uniform dispersion of amorphous Mn and Ce in the surface of catalyst, which were beneficial to interact with reactants. Furthermore, in contrast to Mn–Ce/Al2O3–C, the SCR activity of Fe–Mn–Ce/Al2O3–C catalyst in the presence of H2O, SO2 and H2O and SO2 were 79, 75 and 64%, with the increase of 14, 18 and 19%, respectively. It is indicated that the addition of Fe could inhibit sulfate formation and thus enhance SO2 resistance. XPS results reveal that the doping of Fe into the ceria lattice led to some Ce4+ transferred into Ce3+ in order to maintain the electrical neutrality, thereby facilitating the reduction of Ce4+ → Ce3+ and the formation of oxygen vacancies. NH3 temperature-programmed desorption (TPD) results imply that the doping of Fe onto Mn–Ce/Al2O3–C can remarkably improve the distribution and concentration of acid sites. All the above factors contributed to the improvement of overall NH3 SCR performance of the Fe–Mn–Ce/Al2O3–C catalyst compared with that of the Mn–Ce/Al2O3–C catalyst.

Reusing reclaimed water is considered an effective way to abate water shortages in mega cities and protect the ecological status of rivers and lakes. Controlling of riverbed infiltration is an important way to protect the water environment, as it ensures the recycle of groundwater and maintained the groundwater quality in the recharge zone. The composite of attapulgite clay (AC) and modified-AC (MAC), named three-dimensional network adsorbent, was selected as the infiltration reduction materials, and the ability of controlling infiltration and purification were tested. Results showed that the permeability coefficient reached 10−6 cm/s when AC and MAC were mixed at a ratio of 95:5 and 97:3, respectively. And when the layer thickness was 2–10 cm, the infiltration reduction capacity improved with the increased layer thickness and MAC content. The result of fine particles was greater than coarse particles. As the larger average pore diameter of coarse particles, the cumulative infiltration quantity and permeability coefficient of the AC and MAC coarse particles were lower, in the range of 10.98–11.16 %. The adsorption of ammonium nitrogen (NH4 +) was linear while phosphate (PO4-P) adsorption was nonlinear. Reusing reclaimed water could significantly inhibit the adsorption of NH4 + and PO4-P by AC and MAC.