Background

The discard of used adsorbents may pose a great threat to human health and ecological environment. This work herein reported a facile and feasible method, with aims of (i) reusing the calcined layered double hydroxide (CLDH) adsorbent after azo dye adsorption, and (ii) being further used as a photocatalyst to enhance the degradation of typical pharmaceuticals. Calcination under inner gas flow has been utilized to carbonize adsorbed azo dye and a kind of novel carbonaceous CLDH composite material (CM-CLDH) was synthesized. This fabricated material was used as a catalyst for Ibuprofen removal in water samples under simulated sunlight irradiation.

Results

According to our experimental results, combination of carbonaceous material with CLDH showed an enhanced photocatalytic performance compared to original CLDH materials. More than 90% of Ibuprofen could be removed in less than 180 min. Introduction of carbon material narrowed catalyst’s band gap and turned its conduct band potential to a more negative state, which brought considerable light absorption and higher oxidation ability of photo-induced electrons. Furthermore, photoluminescent spectra and transient photocurrent examination confirmed that carbon material suppressed recombination of photo-induced electrons and holes through faster electron transportation. Under experimental conditions, the removal efficiency of Ibuprofen by CM-CLDH composite kept above 90% during five cycles.

Conclusion

Calcination under inner gas flow can transform organic pollutant-adsorbed CLDH to CM-CLDH composite with higher photocatalytic performance. A feasible way to reuse spent LDH adsorbents was proposed, which is a benefit to reduce second pollution of spent adsorbents in environment.

中文翻译：

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偶氮染料吸附的层状双氢氧化物煅烧的碳质复合材料，光催化效率增强，可去除水中的布洛芬

背景

废旧吸附剂的丢弃可能对人类健康和生态环境构成巨大威胁。本文的这项工作报道了一种简便可行的方法，其目的是（i）在偶氮染料吸附后重用煅烧的层状双氢氧化物（CLDH）吸附剂，以及（ii）进一步用作光催化剂以增强典型药物的降解。利用内部气流下的煅烧使吸附的偶氮染料碳化，合成了一种新型的碳质CLDH复合材料（CM-CLDH）。将该人造材料用作在模拟阳光照射下去除水样中布洛芬的催化剂。

结果

根据我们的实验结果，与原始CLDH材料相比，碳质材料与CLDH的组合显示出增强的光催化性能。不到180分钟即可去除90％以上的布洛芬。碳材料的引入使催化剂的带隙变窄，并将其导带势变为更负的状态，从而带来了可观的光吸收和光致电子的更高氧化能力。此外，光致发光光谱和瞬态光电流检查证实，碳材料通过更快的电子传输抑制了光诱导电子和空穴的复合。在实验条件下，在五个循环中，CM-CLDH复合物对布洛芬的去除效率保持在90％以上。

结论

在内部气流下煅烧可以将吸附有机污染物的CLDH转化为具有较高光催化性能的CM-CLDH复合材料。提出了一种废弃LDH吸附剂再利用的可行方法，有利于减少废弃吸附剂对环境的二次污染。