氮氧共掺杂石墨氮化碳/氯氧化铋异质结光催化去除水体中四环素的性能与机制

Bi9O13.5Cl2-N/O/g-C3N4 heterojunction composites with enhanced photocatalytic activity for degradation of tetracycline: Performance and mechanisms

摘要:

为提升BiOCl和g-C3N4的光催化性能，以双氰胺、草酸二水合物、五水合硝酸铋、氯化铵为主要原料，采用掺杂与异质结共调控策略，通过煅烧-溶剂热-煅烧的处理方法，制备了氮氧共掺杂g-C3N4/BiOCl异质结材料Bi9O13.5Cl2- N/O/g-C3N4（NOBCN）(下角标数字为合成材料的元素原子占比)，并将其用于水体中盐酸四环素（TCH）的光催化降解反应。采用SEM、FTIR、EDS、XRD、XPS、BET等表征NOBCN的结构组成和微观形貌，考察溶液pH、共存离子对NOBCN光催化降解TCH性能的影响，探究N、O掺杂对NOBCN光催化性能提升的原因，推测其机理。结果表明，料液比(g∶L)为0.5∶1（催化剂质量和TCH溶液体积比，下同）的NOBCN在120 min时对初始质量浓度为5.0 mg/L的TCH降解率为98.4%。在pH＝3~11条件下，NOBCN对TCH的光催化降解性能影响不大，在中性或碱性（pH＝7或9）条件下，NOBCN在120 min内对TCH的降解率达100%。NOBCN以薄片花瓣的形式围绕成花朵 形状，具有较大的自由空间和多孔结构；N掺杂提高了NOBCN对可见光的吸收能力，O掺杂为NOBCN提供了大量的自由空间，促进了TCH与NOBCN的有效接触。N、O共掺杂的多重影响使NOBCN表面的结晶度提高，拥有更优异的稳定性和可重复利用性，NOBCN经5次循环使用后，TCH降解率为79.6%。常见阴离子（Cl?、SO42?）或阳离子（K+、Ca2+、Na+、Mg2+）会小幅降低NOBCN对TCH的降解性能，120 min时TCH的降解率同比下降8.5%~ 11.7%，而HCO3?、NO3?虽然会占据活性位点影响其降解能力，但作为光敏剂能够产生更多的自由基，因此基本无影响（-0.2%，-1.4%）。材料对阴阳离子影响能够良好抵抗，具有出色的环境适应能力。羟基自由基和超氧自由基为NOBCN光催化降解TCH的活性物种，O掺杂促进NOBCN光催化降解TCH过程中羟基自由基的生成，这是NOBCN对TCH降解率提升的重要原因，也是其可以适应复杂环境的主要原因。

Abstract:

In this study, the photocatalytic performance of g-C?N? was enhanced by combining doping and heterojunction methods. Co-doped with elemental nitrogen and oxygen (N/O/g-C?N?), was combined with bismuth oxychloride (Bi9O13.5Cl2) to form heterojunction materials (Bi9O13.5Cl2-N/O/g-C3N4). It was synthesized through a calcination-solvent heat-calcination method using dicyandiamide, oxalic acid dihydrate, bismuth nitrate pentahydrate, and ammonium chloride. These materials were synthesized using a doping technique and heterojunction modulation to enhance the photocatalytic performance of g-C?N?. The results indicated that the co-modulation approach broadened the material"s light absorption range and reduced its band gap, enhancing the generation of photogenerated carriers. The degradation effect of the modified photocatalytic material on tetracycline reached 98.4% at 120 min. The environmental adaptability of the material was verified through experiments, and the degradation effect on tetracycline was still more than 80% under the influence of strong acid and strong alkali and different anions and cations, and it could reach 100% under neutral and weak alkaline conditions. The degradation efficiency of 79.6% was preserved after five cycles, showing good photocatalytic degradation effect, stability and practical applicability. Common anions (Cl-, SO?2?) and cations (K?, Ca2?, Na?, Mg2?) slightly reduced the degradation performance of NOBCN on TCH, with the degradation rate decreasing by 8.5% to 11.7% at 120 minutes. In contrast, HCO?? and NO??, while occupying the active sites and potentially affecting degradation, promoted the production of free radicals as photosensitizers, resulting in negligible effects on degradation (-0.2%, -1.4%). The material demonstrates good resistance to both anionic and cationic influences, exhibiting excellent environmental adaptability. ?OH and?O2- are the active species involved in the photocatalytic degradation of TCH by NOBCN. O doping enhances the generation of hydroxyl radicals, which plays a key role in improving the degradation rate of TCH and is the primary factor contributing to its adaptability in complex environments.