Water Research Group (WAREG), School of Environmental Engineering, Universiti Malaysia Perlis, 02600 Arau, Perlis, Malaysia.
Water Research Group (WAREG), School of Environmental Engineering, Universiti Malaysia Perlis, 02600 Arau, Perlis, Malaysia.
Sci Total Environ. 2020 Jun 10;720:137370. doi: 10.1016/j.scitotenv.2020.137370. Epub 2020 Feb 19.
Complete degradation of azo dye has always been a challenge due to the refractory nature of azo dye. An innovative hybrid system, constructed wetland-microbial fuel cell (CW-MFC) was developed for simultaneous azo dye remediation and energy recovery. This study investigated the effect of circuit connection and the influence of azo dye molecular structures on the degradation rate of azo dye and bioelectricity generation. The closed circuit system exhibited higher chemical oxygen demand (COD) removal and decolourisation efficiencies compared to the open circuit system. The wastewater treatment performances of different operating systems were ranked in the decreasing order of CW-MFC (R1 planted-closed circuit) > MFC (R2 plant-free-closed circuit) > CW (R1 planted-open circuit) > bioreactor (R2 plant-free-open circuit). The highest decolourisation rate was achieved by Acid Red 18 (AR18), 96%, followed by Acid Orange 7 (AO7), 67% and Congo Red (CR), 60%. The voltage outputs of the three azo dyes were ranked in the decreasing order of AR18 > AO7 > CR. The results disclosed that the decolourisation performance was significantly influenced by the azo dye structure and the moieties at the proximity of azo bond; the naphthol type azo dye with a lower number of azo bond and more electron-withdrawing groups could cause azo bond to be more electrophilic and more reductive for decolourisation. Moreover, the degradation pathway of AR18, AO7 and CR were elucidated based on the respective dye intermediate products identified through UV-Vis spectrophotometry, high-performance liquid chromatography (HPLC), and gas chromatograph-mass spectrometer (GC-MS) analyses. The CW-MFC system demonstrated high capability of decolouring azo dyes at the anaerobic anodic region and further mineralising dye intermediates at the aerobic cathodic region to less harmful or non-toxic products.
由于偶氮染料的难降解性质，完全降解偶氮染料一直是一个挑战。本研究构建了一种创新性的复合系统——人工湿地-微生物燃料电池（CW-MFC），用于同时修复偶氮染料和回收能源。该系统考察了电路连接方式和偶氮染料分子结构对偶氮染料降解率和生物电能产生的影响。与开路系统相比，闭路系统表现出更高的化学需氧量（COD）去除率和脱色效率。不同运行系统的废水处理性能按以下顺序递减：CW-MFC（R1 种植-闭路）>MFC（R2 植物-闭路）>CW（R1 种植-开路）>生物反应器（R2 植物-开路）。其中，酸性红 18（AR18）的脱色率最高，为 96%，其次是酸性橙 7（AO7），为 67%，刚果红（CR），为 60%。三种偶氮染料的电压输出按以下顺序递减：AR18>AO7>CR。结果表明，偶氮染料结构和偶氮键附近的取代基对脱色性能有显著影响；含较少偶氮键和更多吸电子基团的萘酚型偶氮染料，由于偶氮键更具亲电性和还原性，更容易发生脱色反应。此外，通过紫外-可见分光光度法、高效液相色谱（HPLC）和气相色谱-质谱联用（GC-MS）分析鉴定的各自染料中间产物，阐明了 AR18、AO7 和 CR 的降解途径。CW-MFC 系统在厌氧阳极区具有高效的偶氮染料脱色能力，并进一步在有氧阴极区将染料中间产物矿化为毒性较小或无毒的产物。
