Textile-effluent treatment using Aloe vera mucilage as a natural coagulant prior to a photo-Fenton reaction

In this study, the mucilage of Aloe vera was used as a new auxiliary coagulant in pre-treatment using a combined system based on the photo-Fenton (PF) process for the treatment of textile effluents. Coagulation-flocculation (CF) using a combination of coagulants showed better performance in the elimination of turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), and natural organic matter (NOM) when compared with a single inorganic coagulant. In addition, the combination of coagulants allowed a 28% reduction in the concentration of the inorganic coagulant used. To remove the dissolved and recalcitrant matter after CF, the pretreated effluent was subjected to a PF process that is efficient in the degradation and mineralization of dissolved organic compounds; this resulted in the elimination of 82.48% of COD, 80.34% of DOC, and 79.65% of NOM, as well as the formation of inorganic ions. The toxicity of the samples was evaluated base on three organisms of different trophic levels: Lactuca sativa, Artemia salina, and Eisenia fetida. The results showed that the samples treated by CF or CF/PF were non-toxic to A. salina and E. fetida. However, in the L. sativa bioassay, the root growth parameter revealed toxicity in the effluents before and after treatment, excluding the untreated effluents with doses of 100 and 200 mL L-1 and the effluent with a dose of 100 mL L-1 treated by the CF process.

Automated summary

In this study, the mucilage of Aloe vera was used as a new auxiliary coagulant for the pre-treatment of textile effluents. The combination of coagulants showed better performance in removing turbidity, COD, DOC, and NOM compared to single inorganic coagulants. After coagulation-flocculation, a photo-Fenton process was used to degrade and mineralize dissolved organic compounds, resulting in the reduction of COD, DOC, and NOM. The toxicity of the treated samples was evaluated using three organisms, and the results showed that the treated samples were non-toxic to two of the organisms.