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Theses and dissertations (Engineering and Built Environment)

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Subject: search.filters.subject.Factory and trade waste—Purification

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    Treatment of industrial effluent using specialized, magnetized coagulants
    (2023-05) Sibiya, Nomthandazo Precious; Rathilal, Sudesh
    The rapid degradation of water quality caused by industrial effluent presents a significant threat to public health and the ecosystem. This necessitates ecologically sustainable solutions through the coagulation treatment method. Coagulation with chemical coagulants (e.g. alum) is costeffective, but comes with non-recoverability, health and environmental risks. As a result, this study proposes a magnetic-coagulation separation technique as an alternative. Against this brief, the goal of this research was to produce specialized magnetic coagulants for the treatment of industrial wastewater. Three magnetized coagulants (MCs) viz. chitosan magnetite (CF), eggshell magnetite (EF), and rice starch magnetite (RF) were synthesized via the co-precipitation technique by using chitosan, eggshell, or rice starch with Fe3O4 nanoparticles (F) in three distinct ratios (1:2, 1:1, and 2:1). The analytical results via the Fourier-transform infrared (FTIR) spectroscopy, Brunauer– Emmett–Teller (BET) analyzer, X-ray diffraction (XRD) analyzer, and scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy respectively affirmed the success of MCs functional and molecular properties, surface area, crystal structure, surface morphology, and elemental compositions. Following that, a series of investigations were carried out utilizing coagulation and dissolved air flotation (DAF) methods to investigate the application and treatability performance of the MCs. Amongst the MCs, the RF(1:1) was found to be the most successful, removing over 75% of the turbidity, total suspended solids (TSS), and over 50% of the chemical oxygen demand (COD) from a local industrial effluent. Furthermore, response surface methodology (RSM) based on a Box–Behnken design (BBD) was used to optimize and compare the coagulation and DAF methods. With coagulant dose (2 – 4 g), settling/flotation time (10 – 60 min) and mixing rate (50 – 150 rpm), the optimum coagulation conditions of 4 g dose, 30 minutes of settling time, and a mixing rate of 50 rpm, achieved a desirability of 87.20%. A 15-min flotation time, with a mixing rate of 50 rpm, and a coagulant dose of 4 g resulted in 77.4% desirability in the DAF method. The DAF method was considered to be more favorable with a shorter settling/flotation time and a desirability of 75% with 95% confidence. Notably, the RSM-BBD models demonstrated a strong correlation (0.9 < R 2 < 1) with predicted results that were consistent with the experimental data. The recent findings indicate that the prospects of MCs are possible for wastewater treatment, and hence magnetic separation technology should be given consideration in water and wastewater treatment settings.