RESUMEN
The application of natural coagulants derived from food byproducts in domestic wastewater tertiary treatment, which contains a number of impurities as suspended colloidal particles, has a potential use as essential substitutes for traditional inorganic coagulants. These biomaterials are a sustainable and environmentally friendly alternative that can be used to improve water quality and human health. In this study, prickly pear (PP) fruit peel mucilage gel was evaluated as a novel coagulant for the tertiary stage of domestic wastewater treatment. Jar tests were performed on residual raw water at the inlet (influent) and outlet (effluent) of the tertiary wastewater treatment (constructed wetland) with a coagulant dose of 12 mg L-1 at a pH of 13. The efficiency of green (i.e., mucilage) and inorganic chemical (i.e., FeCl3) coagulants was compared on the basis of turbidity and color removal. The flocs produced by the coagulants were characterized structurally by FTIR spectroscopy and Zeta potential analysis and morphologically by scanning electron microscopy (SEM). The results showed that the turbidity and the color removal efficiency of the mucilage compared to the FeCl3 at the outlet of the treatment (effluent) were practically the same, reaching 94% turbidity and 85-87% color removal efficiency with both coagulants. The structure and morphology of the flocs generated by the coagulants showed a higher content of organic matter trapped in the flocs. The floc formation observed mechanisms were adsorption/bridging for mucilage and charge neutralization for FeCl3. The results of this study demonstrated that the PP mucilage green coagulant can be used to enhance the quality of treatment of domestic wastewater in an eco-friendly and biodegradable manner.
RESUMEN
The peels obtained as a byproduct from the processing of fruits (prickly pears) of the Cactaceae family are a rich source of mucilage, a hydrocolloid biopolymer that may have potential application in water/wastewater treatment as a natural coagulant. In this study, the structural (UPLC-QTOF-MS, FTIR, Raman, NMR, XRD, and zeta potential), morphological (SEM), and thermal (DSC/TGA) characterizations of the mucilage extracted from the peels of Opuntia ficus-indica (OFI) fruits were carried out. UPLC-QTOF-MS results revealed the presence of a branched polymer with an average molecular weight of 0.44 KDa for this mucilage in aqua media. The NMR spectra of mucilage in DMSO-d6 indicated that it seemed well-suited as a coagulant with its typical oligosaccharide structure. FTIR studies confirmed the presence of hydroxyl and carboxyl functional groups in the mucilage, indicating its polyelectrolyte nature that could provide coagulating properties through binding and adsorption mechanisms. Likewise, the zeta potential of -23.63 ± 0.55 mV showed an anionic nature of the mucilage. Power XRD technique evidenced the presence of crystalline poly(glycine-ß-alanine), glutamic acid, and syn-whewellite. SEM images revealed an irregular and amorphous morphology with cracks, which are suitable characteristics for adsorption mechanisms. The mucilage exhibited two endothermic transitions, with a decomposition temperature in uronic acid of 423.10 °C. These findings revealed that mucilage obtained from OFI fruit peels has molecular and physicochemical characteristics that are suited to its possible application as a natural coagulant in water/wastewater treatments.
RESUMEN
Natural coagulants derived from by-products have gained popularity as sustainable alternatives to inorganic coagulants in water/wastewater treatment due to their abundant availability, biodegradability, low cost, easy disposal and low sludge volumes. In this study, the mucilage obtained from the peel of Opuntia ficus-indica fruit was evaluated as a biocoagulant for treating synthetic turbid water and compared with a traditional chemical coagulant (FeCl3). The effects of coagulant dosage and pH on the turbidity and color-removal efficiency of synthetic turbid water were analyzed. To estimate the coagulation mechanism, the flocs produced under optimal values were characterized structurally (FTIR and zeta potential) and morphologically (SEM). The optimal condition for the removal of turbidity and color was a coagulant dose of 12 mg/L at pH 13. For the optimal values, the biocoagulant and the FeCl3 presented a maximum removal of 82.7 ± 3.28% and 94.63 ± 0.98% for turbidity and 71.82 ± 2.72% and 79.94 ± 1.77% for color, respectively. The structure and morphology of the flocs revealed that the coagulation mechanism of the mucilage was adsorption and bridging, whereas that of FeCl3 was charge neutralization. The results obtained showed that the mucilage could be used as an alternative coagulant to replace FeCl3.
