Photocatalytic degradation is an effective and challenging strategy in purifying wastewaters containing organic pollutants. Thus, developing a suitable photocatalyst and clarifying the degradation mechanism are extremely worthwhile. In this work, Zn 2+ -decorated porous g-C 3 N 4 with nitrogen vacancies (g-C 3 N 4-δ ) is prepared with the facile sonication-calcination method. Benefitting from the modified geometric structure and electronic properties, compared with g-C 3 N 4-δ , the resulting composites deliver reduced micropore percentage, enhanced separation and migration of photogenerated carriers, narrowed band gap, and improved reducing capacity of photoinduced electrons, favoring the photocatalytic reaction. Particularly, Zn 2+ (2)-g-C 3 N 4-δ (10 mg) displays the highest photocatalytic activity toward eliminating tetracycline (TC, 10 mg L -1 , 50 mL), and the degradation efficiency (63.9%) within 30 min is 3.4 times that of g-C 3 N 4-δ (18.9%) irradiated by visible light. Moreover, the optimal composite demonstrates satisfactory recyclability and excellent universality. This study suggests a novel way to construct g-C 3 N 4 -based photocatalysts for efficiently degrading organic contaminants in water.
Min Chen,Jiangzhou Luo,Honglei Ling,Xueping Zong,Song Xue
Developing membranes that combine excellent gas separation performance with robust resistance to plasticization is highly demanded for membrane separation but remains a challenge. Herein, a series of Zn 2+ functionalized poly(benzoxazole-co-imide) membrane was constructed via co-polymerizing (4,4′-hexafluoroisopropylidene) diphthalic anhydride (6FDA) with o-hydroxyl diamine 2,2′-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (BisAPAF) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) followed by thermal rearrangement (TR) and Zn 2+ modification processes. The TR conversion opened the polymer chains with larger d-spacing and higher BET surface area, thus, greatly increased the gas permeability . Meanwhile, the post Zn 2+ modification resulted in a huge improved selectivity because of the π-complexation reactions between Zn 2+ and CO 2 and the formation of a Zn 2+ coordination crosslinking network. As a result, due to the synergistic effect of TR and Zn 2+ modification, the overall gas transport properties of these newly developed membranes were greatly improved. Furthermore, the dual network structures that arise from the remaining network PI and the Zn 2+ coordination crosslinking contribute to the resultant membrane with excellent anti-plasticization capability. A represent membrane termed as PBOI-Zn 2+ -14h membrane exhibits great CO 2 /CH 4 separation performance, delivering a CO 2 permeability of 1048.1 Barrer and a CO 2 /CH 4 selectivity of 46.1 that is exceeded the 2008 Roberson limitation. Furthermore, this membrane possesses remarkable resistance to CO 2 -induced plasticization, withstanding pressures above 35 Bar. Overall, this study presents an effective way for constructing polymer membranes with both high gas separation performance and strong resistance to plasticization issue.
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