Department of Chemical Engineering, Jadavpur University, Kolkata 700032, India.
Department of Pharmaceutical Chemistry, CMR College of Pharmacy, Affiliated to Jawaharlal Nehru Technological University Hyderabad, Hyderabad, Telangana 501401, India.
Sci Total Environ. 2024 Dec 1;954:176426. doi: 10.1016/j.scitotenv.2024.176426. Epub 2024 Sep 24.
The synthetic azo dyes are widely used in the textile industries for their excellent dyeing properties. They may be classified into many classes based on their structure and application, including direct, reactive, dispersive, acidic, basic, and others. The continuous discharge of wastewater from a large number of textile industries without prior treatment poses detrimental effects on the environment and human health. Azo dyes and their degradation products are extremely poisonous for their carcinogenic, teratogenic and mutagenic nature. Moreover, exposure to synthetic azo dyes can cause genetic changes, skin inflammation, hypersensitivity responses, and skin irritations in persons, which may ultimately result in other profound issues including the deterioration of water quality. This review discusses these dyes in details along with their detrimental effects on aquatic and terrestrial flora and fauna including human beings. Azo dyes degrade the water bodies by increasing biochemical and chemical oxygen demand. Therefore, dye-containing wastewater should be effectively treated using eco-friendly and cost-effective technologies to avoid negative impact on the environment. This article extensively reviews on physical, chemical and biological treatment with their benefits and challenges. Biological-based treatment with higher hydraulic retention time (HRT) is economical, consumes less energy, produces less sludge and environmentally friendly. Whereas the physical and chemical methods with less hydraulic retention time is costly, produces large sludge, requires high dissolved oxygen and ecologically inefficient. Since, biological treatment is more advantageous over physical and chemical methods, researchers are concentrating on bioremediation for eliminating harmful azo dye pollutants from nature. This article provides a thorough analysis of the state-of-the-art biological treatment technologies with their developments and effectiveness in the removal of azo dyes. The mechanism by which genes encoding azoreductase enzymes (azoG, and azoK) enable the natural degradation of azo dyes by bacteria and convert them into less harmful compounds is also extensively examined. Therefore, this review also focuses on the use of genetically modified microorganisms and nano-technological approaches for bioremediation of azo dyes.
合成偶氮染料因其出色的染色性能而被广泛应用于纺织工业。根据其结构和应用，它们可分为许多类别，包括直接染料、活性染料、分散染料、酸性染料、碱性染料等。大量纺织工业未经预处理就连续排放废水，对环境和人类健康造成有害影响。偶氮染料及其降解产物具有致癌、致畸和致突变的特性，毒性极强。此外，接触合成偶氮染料会导致遗传变化、皮肤炎症、过敏反应和皮肤刺激，最终可能导致其他严重问题，包括水质恶化。本文详细讨论了这些染料及其对水生和陆地动植物包括人类的有害影响。偶氮染料通过增加生化需氧量和化学需氧量来降解水体。因此，应采用环保且经济有效的技术对含染料废水进行有效处理，以避免对环境造成负面影响。本文广泛综述了物理、化学和生物处理及其优缺点。具有较高水力停留时间（HRT）的生物处理既经济、能耗低、产生的污泥少，也对环境友好。而水力停留时间较短的物理和化学方法成本较高、产生的污泥较多、需要较高的溶解氧且生态效率较低。由于生物处理比物理和化学方法更具优势，研究人员正在专注于生物修复，以从自然界中消除有害偶氮染料污染物。本文对生物处理技术的最新进展进行了全面分析，包括其发展和去除偶氮染料的效果。还广泛研究了编码偶氮还原酶（azoG 和 azoK）基因的机制，这些酶使细菌能够自然降解偶氮染料，并将其转化为危害较小的化合物。因此，本文还重点介绍了利用基因修饰微生物和纳米技术进行偶氮染料生物修复的方法。
