Othmani Bouthaina, Gamelas José A F, Rasteiro Maria Graça, Khadhraoui Moncef
Laboratory for Environmental Engineering and Eco-technology, ENIS, University of Sfax, Sfax 3038, Tunisia.
Department of Chemical Engineering, CIEPQPF, FCTUC, University of Coimbra, 3030-790 Coimbra, Portugal.
Polymers (Basel). 2020 Aug 30;12(9):1964. doi: 10.3390/polym12091964.
Dye invasion in wastewaters is undeniably one of the crucial environmental concerns in addition to the supplement of toxic synthetic chemical flocculants used for color removal using the conventional coagulation-flocculation process. With the aim to improve the flocculation stage in terms of reagents safety and ensure dyes removal, the present study explores the flocculating effectiveness of two natural, stable, and eco-friendly cactus formulations, namely 60 °C oven-dried (DP) and lyophilized (LP) cladodes. Both formulations were assessed to treat cationic (Methylene blue; MB) and anionic (Methyl Orange; MO) dye solutions as a substitution attempt for the currently questioned employed synthetic chemical flocculants. Obtained results demonstrate that, in conjunction with alum as coagulant, the lyophilized powder (LP) bio-based flocculant appears to be the most efficient cactus formulation, showing a significant color (83%) and a turbidity (69%) abatement for the cationic dye (MB) and, respectively, 63% and 62% for the anionic one (MO). Additionally, the flocculation activity of the LP formula remained high over an eight-month period of storage. Moreover, based on the Fourier transform infrared (FTIR) spectroscopic analysis and the chemical characterization of cactus formulations, the occurring flocculation mechanisms of the dye removal are presumed to be based on both adsorption and bridging phenomena. Further, the significant color and turbidity decline achieved upon the addition of the lyophilized cactus cladodes powder (LP), enhancing thus the coagulation performance of the alum-based coagulant, proved the effectiveness of this bio-flocculant compared to the commonly used chemical flocculant (polyacrylamide). Hence, it was suggested that lyophilized cactus cladodes as a natural flocculant could be one of the effective surrogates to chemical flocculants conventionally used in wastewater treatment for the sake of a safer and sustainable environment.
除了在传统混凝-絮凝过程中使用有毒合成化学絮凝剂来去除颜色外，废水中的染料侵入无疑是关键的环境问题之一。为了在试剂安全性方面改进絮凝阶段并确保染料去除，本研究探索了两种天然、稳定且环保的仙人掌制剂的絮凝效果，即60℃烘箱干燥（DP）和冻干（LP）的仙人掌茎片。评估了这两种制剂对阳离子（亚甲基蓝；MB）和阴离子（甲基橙；MO）染料溶液的处理效果，作为对目前备受质疑的合成化学絮凝剂的替代尝试。获得的结果表明，与作为混凝剂的明矾一起使用时，冻干粉末（LP）生物基絮凝剂似乎是最有效的仙人掌制剂，对阳离子染料（MB）的脱色率（83%）和浊度去除率（69%）显著，对阴离子染料（MO）分别为63%和62%。此外，LP配方的絮凝活性在八个月的储存期内保持较高。此外，基于傅里叶变换红外（FTIR）光谱分析和仙人掌制剂的化学表征，推测染料去除过程中发生的絮凝机制基于吸附和架桥现象。此外，添加冻干仙人掌茎片粉末（LP）后显著的颜色和浊度下降，从而提高了明矾基混凝剂的混凝性能，证明了这种生物絮凝剂与常用化学絮凝剂（聚丙烯酰胺）相比的有效性。因此，有人建议，冻干仙人掌茎片作为一种天然絮凝剂，为了更安全和可持续的环境，可能是废水处理中传统使用的化学絮凝剂的有效替代品之一。
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