The pore size distribution and specific surface area of the attapulgite is a crucial parameter for the uptake of pigments of oil. Bleaching of the soybean oil with three attapulgites with different pore size distribution, which were assigned a, b, and c, respectively was investigated. The specific surface area and the pore size distribution of the attapulgites were characterized. The Freundlich isotherm analysis was used to evaluate the sorption capacity of the three attapulgite. Sample b gave the highest surface area and sample c the lowest. Sample b exhibited a wider pore distribution (8-65 Å ) whereas samples a and c had more micropores smaller than 15 Å . Sample a, in contrast to samples b and c, was characterized by some larger pores (100-170 Å ). The sorption capacity followed the sequence: attapulgite sample c > attapulgite sample a > attapulgite sample b. The sorption capacity was decided by the pore size distribution. The more pores with a distribution range 8-32 Å (i.e., close to the diameter of the pigments), the more pigments were removed. The attapulgite sample c, which had most pores (8-32 Å ) was the best.

The high-pressure phase diagrams of binary Se–N system have been constructed using the CALYPSO method and first-principles calculations. Four stable compounds (Cmc21-SeN2, P21 /m-SeN3, P1̅-SeN4, and P1̅-SeN5) were identified at high pressures. Various peculiar nitrogen polymerization forms composed of single/double nitrogen–nitrogen bonds were found at the nitrogen-rich condition, such as N∞-chains in P21/m-SeN3, oligomeric N8-chains in P1̅-SeN4, and distorted N6 3– anion rings in P1̅-SeN5. Peculiar nitrogen polymerization forms make these compounds potential high-energy-density materials (HEDMs). Especially, P1̅-SeN5 has the highest energy density of 4.08 kJ g–1 among the selenium nitrides. The polymerization mechanism of nitrogen in the Se–N system has been explored using the “Lewis-like” two-center–two-electron and three-center–two-electron bonding analysis. Using the nitrogen-rich P1̅-SeN5 as a prototype, it is found that the famous N6 distortion in the polymerized nitrogen HEDM can be explained by the interatomic mechanical unbalance which is induced by the three-center two-electron bonding between the metal atom and the two neighboring nitrogen atoms.

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