Faculty of Science, Agriculture and Engineering

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Browsing Faculty of Science, Agriculture and Engineering by Subject "Acrylamide (AM)"

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    Synthesis and application of a grafted flocculant produced from a chemical combination of a bioflocculant TKT and acrylamide (AM)
    (University of Zululand, 2019) Masuku, Sicelo Keny; Basson, A.K.; Simonis, J.J.; Maliehe, T.S.
    An increase in pollution from mining, industries and agriculture has decreased the quality of fresh water in South Africa. Contaminated water is unsafe for animals to drink and for plants to absorb. Synthetic flocculants are extensively used in water and wastewater treatment due to their effectiveness and low cost. These flocculants consist of a flexible chain of high molecular weight to create a bigger surface area for biochemical reactions to take place and are documented to flocculate well in small amounts. However, these flocculants are known to be carcinogenic, neurotoxic and hazardous to the environment. Moreover, natural polymers (bioflocculants) are not toxic and are biodegradable. Nevertheless, these flocculants need to be suitably controlled because biodegradability reduces their shelf-life. Through grafting synthetic polymers onto a backbone of natural polymers, the best properties of synthetic and natural flocculants are merged. When grafted copolymers are successful, the dangling grafted chains have easy access to contaminants in wastewater. In literature it has been reported that grafted polysaccharides provide efficient, shear stable and biodegradable flocculants. This study aimed at synthesizing and applying a grafted bioflocculant produced from marine Alcaligenes faecalis HCB2 to wastewater. Extraction and purification of the bioflocculant was obtained through using the solvent extraction method. Chains of polyacrylamide (PAM) were grafted onto the backbone of bioflocculant TKT extracted from Alcaligenes faecalis HCB2 using a microwave initiated method. Various grades of TKT-g-PAM were synthesized and the one with the highest percentage grafting was used throughout this study. Physicochemical analyses of the grafted bioflocculant (TKT-g-PAM) were attained by scanning electron microscopy (SEM), Zetasizer Nano, Thermogravimetric Analyzer (TGA) and Fourier Transform Infrared (IR) Spectrophotometry. A diphenyl tetrazolium bromide (MTT) assay was used to determine the biosafety of the grafted bioflocculant. The effect of dosage size on flocculating activity was evaluated. The pH and thermal stability of TKT-g-PAM were assessed spectrophotometrically. The removal efficiencies of TKT-g-PAM on chemical oxygen demand (COD), biological oxygen demand (BOD), nitrogen and sulfur on wastewater from Tendele Coal Mine were performed using different test kits. x | P a g e The bioflocculant yield obtained after extraction and purification was 4.0 g/l. TKT-g-PAM6 was the preferred grade with the highest percentage of 62% and a weight of 0.8 g. The images provided by SEM revealed changes in bioflocculant structure from a blocky to a granular structure after grafting. This confirmed that the grafting of PAM chains was successful on the TKT backbone. The zeta potential of grafted bioflocculant (-12.6±0.1) and bioflocculant (-17.1±0.65) had a negative charge. IR observations indicated hydroxyl, carboxyl and amine groups. TKT-g-PAM6 showed less cytotoxic effect on HEK293 cells (retained 82% of cell viability after it was treated in high concentration) while CaCO2 cells (retained 64% of cell viability after it was treated in high concentration). TKT-g-PAM6 was cation and pH dependent and optimally flocculated kaolin clay suspension at a dosage of 0.2 mg/ml with 74% of flocculating activity in the presence of Ba2+. TKT-g-PAM6 was more stable at acidic pH 3-5 with the highest flocculating activity (93%) observed at pH 3. TKT-g-PAM6 was thermostable and retained more than 90% of its flocculating activity after being heated at 100 °C for 1 hour. The pyrolysis properties of the grafted bioflocculant confirmed their thermal stabilities, the IDT has been found to 215 °C (29% weight loss) and FDT to be 571 °C (36% weight loss). Flocculating efficiencies were: 87% on COD, 92% BOD, 91% N and 93% S, respectively. TKT-g-PAM6 was effective and has the potential to be used in wastewater treatment.
University of Zululand