Abstract

Dye wastewater containing non-fixed dyes discarded from different manufacturing industries is a major concern in environmental pollution. Amongst all other non-fixed dyes, anionic dyes hold a significant share in the dye wastewater (32–90%) stream, due to their extensive uses. In this study, cotton gin trash (CGT) is proposed for valorisation and utilisation as a bioadsorbent for the anionic dye. Gin trash was transformed into a film by a single-step process. Since −OH group rich CGT film tends to adsorb cationic dye, chitosan that has adsorption capability towards anionic dyes was used to modify CGT by introducing positive charges for the adsorption of anionic Acid Blue 25 (AB). The morphology, roughness, chemical structure and zeta potential of the raw CGT powder and chitosan-modified CGT (CHT–CGT) film were reported. The fabricated film showed roughness and pores in the surface favouring the dye adsorption. The adsorption process followed the physisorption phenomenon rather than the chemisorption process, where cationic CHT–CGT film attracted anionic AB. Kinetics and equilibrium adsorption of the system were described as favourable, fitting better with the Langmuir model compared to Freundlich, Dubinin–Radushkevich and Flory–Huggins isotherms. The maximum adsorption of the CHT–CGT film was 151.5 mg/g, compares favourably among other reported lignocellulosic waste. Besides, CHT–CGT film was found reusable after desorption, without significantly altering its removal efficiency. The results along with our previous report explore a sustainable pathway of adding value to CGT as a dye bioadsorbent from wastewater, where unmodified and chitosan-modified CGT films together have the potential to separate both cationic and anionic dyes concurrently.

Graphic abstract

中文翻译：

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壳聚糖修饰棉杜松子酒垃圾膜对阴离子蓝25的吸附

摘要

从不同制造行业丢弃的含有非固定染料的染料废水是环境污染的主要问题。在所有其他非固定染料中，由于它们的广泛使用，阴离子染料在染料废水中占有相当大的份额（32-90％）。在这项研究中，提出了轧棉废料（CGT）进行增值和用作阴离子染料的生物吸附剂的建议。杜松子酒垃圾通过一步一步的方法就变成了电影。由于富含-OH基团的CGT膜倾向于吸附阳离子染料，因此具有对阴离子染料具有吸附能力的壳聚糖被用于通过引入用于吸附阴离子酸性蓝25（AB）的正电荷来改性CGT。报告了原始CGT粉末和壳聚糖改性CGT（CHT–CGT）薄膜的形貌，粗糙度，化学结构和Zeta电位。制得的膜在表面上显示出粗糙和孔，有利于染料吸附。吸附过程遵循的是物理吸附现象，而不是化学吸附过程，在此过程中，阳离子CHT-CGT膜吸引了阴离子AB。系统的动力学和平衡吸附被认为是有利的，与Freundlich，Dubinin–Radushkevich和Flory–Huggins等温线相比，更适合Langmuir模型。CHT–CGT膜的最大吸附量为151.5 mg / g，在其他报道的木质纤维素废料中具有优势。此外，发现CHT–CGT膜在解吸后可以重复使用，而不会显着改变其去除效率。结果与我们之前的报告一起探索了一种可持续的途径，即为CGT作为废水中的染料生物吸附剂增加价值，

图形摘要