Green Extraction of Phyto- Flocculant for Drinking Water Disinfection and Turbidity Treatment

Abstract

Conventional water treatment relies heavily on chemical coagulants and disinfectants, which are expensive, potentially harmful to the environment, and may pose health risks, underscoring the need for sustainable, eco-friendly alternatives that ensure safe, and effective water treatment. This study investigated, extracted, and optimized a green phyto-flocculant from wild Sesame (Sesamum spp.) for disinfection and turbidity removal in wastewater treatment plants, demonstrating a sustainable, environmentally friendly approach to drinking water treatment. Phytochemicals were extracted and modified using 500 mL of an ethanol–water solution containing 50 g of plant parts. The pH of the extract was adjusted dropwisely to a neutral condition using 1 M sodium hydroxide and 0.1 M ferric chloride, thereby producing a black precipitate that was washed and oven-dried at 60 °C for 24 h. Preliminary phytochemical screening of wild Sesame (flower, leaf, root, seed, stem, and whole plant), using 70% ethanol, confirmed the presence of tannins, phenols, flavonoids, steroids, and other secondary metabolites through characteristic colour changes. Liquid Chromatography-Mass Spectrometry (LC-MS) results showed that different metabolites were present in the plant parts, including 2 phenols (Gingerol), 5 Tannins (Vanillic acid 4-|A-D- glucoside), 2 steroids (Capronor), and 19 flavonoids. The prepared composite was further analysed using selected characterization techniques, such as Scanning Electron Microscope and Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). Analysis showed both crystalline and amorphous phases, with the seed extract exhibiting a high amorphous content (83%), which is favourable for water treatment applications. The FTIR spectra verified the existence of characteristic –OH, –NH, –COOH, C=O, C–C, and C–H functional groups. The (SANS 241: 2015) recommended standard was used to determine the best-performing Sesame plant flocculant for the treatment of water at 4 and 100 μg/mL flocculant concentrations, and the seed complied with all parameters compared to other flocculants. The seed extract at 100 μg/mL showed the highest performance for Malamulele water works. The central composite model predictions closely matched experimental results, confirming its suitability for optimizing disinfection and turbidity removal using the wild Sesame flocculant. Optimal conditions were 100 μg of flocculant dosage, 90 min of treatment time, and 30 rpm agitation, achieving 100% disinfection and 99% turbidity removal with a high desirability of 0.967. These complied with the SANS drinking water standards and outperformed the current treatment quality observed at Malamulele Water Works.