Theses and dissertations (Applied Sciences)
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Item Removal of selected heavy metals from wastewater using modified agricultural waste(2023-09) Msimango, Maureen Nomaxhosa; Qwabe, L. Q.; Ntola, P.This study explores the potential of utilizing inexpensive adsorbent materials derived from agricultural waste to eliminate Zn (II), Ni (II) and Cd (II) from water-based solutions. Sugarcane bagasse was chemically modified to extract cellulose and further functionalize extracted cellulose to prepare carboxymethyl cellulose which were used as biosorbents. The biosorbents were characterized using XRD, FTIR (ATR), and SEM for confirmation of physical and chemical properties and surface morphology of the adsorbents. In batch experiments, the effect of various parameters such initial concentration (10-300 mg/L), pH (2- 8), adsorbent mass (0.1-1.7 g), and contact time (5-150 min). Adsorption was poor for all metals below pH 4 and reached maximum removal efficiency at pH 6. The increase in initial concentration favoured the increase in removal efficiency but reaches a maximum beyond 100 mg/L. The increase in biosorbent mass shows favours increase in removal efficiency for Ni (II) and Cd (II) but a decrease was observed for Zn(II). The removal efficiency increased with contact time and reached equilibrium at 60 minutes for all metals and biosorbents. The maximum adsorption capacities of Zn(II), on SCB, SCBC, and CMC were 12.3, 20.9 , and 33.5 mg/g respectively. Ni (II) adsorption capacities on SCB, SCBC, and CMC, were 41.9, 25.4, and 125.7 mg/g respectively. The maximum capacities of Cd(II) on SCB, SCBC, and CMC, were 11.3, 20.8, and 21.6 mg/g respectively. The performance of CMC superseded SCB and SCBC. Kinetic experiments showed that the adsorption process followed pseudo second order whereas the equilibrium studies showed that the adsorption process followed the Langmuir adsorption isothermItem Design and optimization of an adsorption method for the removal of textile azo dyes from aqueous solutions using Plantago lanceolata(2021) Kaunda, Thabisile Penelope; Gengan, Robert Moonsamy; Singh, T.Water is an essential commodity for human survival; however, this resource is predicted to be scarce within the 21st Century due to pollution and industrialization. Textile industries are among the many polluters of water, and hence methods to remediate textile waste-water need attention. In this study, a common garden weed Plantago Lanceolata was used for the preparation of novel activated carbon materials as an adsorbent for the degradation of textile azo dyes Reactive Blue 222 (RB), Reactive Red 195 (RR), and Reactive Yellow 145 (RY). The activated carbon was modified with four different chemical activators to produce phosphoric acid-based activated carbon (H3PQ4-AC), sulfuric acid-based activated carbon (H2SO4-AC), potassium hydroxide-based activated carbon (KOH-AC), and sodium hydroxide-based activated carbon (NaOH-AC). These materials were characterized by Fourier- transfer infrared spectroscopy (FTIR), scanning electron microscope with energy dispersive Xray (SEM/EDX), high resolution transmitting electron microscope (HRTEM), and a thermogravimetric analyzer with differential scanning calorimeter (TGA/DSC). The initial concentration of the adsorbate, adsorbent dosage concentration, contact time, temperature, and pH were optimized. The four materials adsorption capacity was studied, and H3PQ4-AC produced the best results of adsorption capacity 98,98% - 100%, with optimum agitation time of 70 minutes, the optimum dosage of 0.8 g/60 ml of adsorbent, and pH of 6. The experimental data were fitted using Langmuir (type 1- 4), Freundlich, Temkin, and Dubinin-Radushkevich isotherms. The data from this study best fitted the Langmuir isotherm type 1: RB (qm -15.58 mg g 1 ), RR (qm - 11.24 mg g 1 ) and RY (qm - 11.24 mg g 1 ). Furthermore, the reaction rate followed the pseudosecond-order kinetic model while the intraparticle diffusion model had no impact. Its thermodynamic parameters indicated the reaction as spontaneous and exothermic. Furthermore, a nanocomposite was prepared from H3PQ4-AC and iron oxide to produce an iron oxide/activated carbon nanocomposite. FTIR, SEM/EDX, HRTEM, and TGA/DSC fully characterized this novel material. The iron oxide/H3PQ4-AC nanocomposite produced slightly better results compared to H3PO4-AC: RB (99.60% - 100%), RR (99.59 - 100%) and RY (99.48% - 100%). The experimental data fitted Langmuir isotherm type 1, and the reaction followed the pseudo-second-order kinetic reaction model.Item Synthesis of amine-epoxy based polymers and their potential application in the remediation of selected organic dyes from synthetic effluents(2017) Raghunath, Sharista; Gengan, Robert MoonsamyThe presence of dyes in effluent poses various environmental as well as health hazards for many organisms. Although various remediation strategies have been implemented to reduce their effect, dyes still manage to infiltrate into the environment and hence new strategies are required to address some of the problems. This study investigated the innovation of two cationic water-soluble polymers viz., Proline-Epichlorohydrin-Ethylenediamine Polymer (PEP) and Thiazolidine-Epichlorohydrin-Ethylenediamine Polymer (TEP) that were used to remediate selected synthetic dyes from synthetic effluent by adsorption and dye reduction. Both polymers were synthesized using monomers of a secondary amine, epichlorohydrin and ethylenediamine and were subsequently characterized and modified and their remediation potential studied. In the first study, PEP was synthesized and characterized by 1H-NMR Spectroscopy, FT-IR Spectroscopy, dynamic light scattering, and thermogravimetric analysis (TGA). Thereafter PEP was modified with bentonite clay, by simple mixing of the reactants, to form a Proline-Epichlorohydrin-Ethylenediamine Polymer-bentonite composite (PRO-BEN); it was characterized by FT-IR Spectroscopy, scanning electron microscopy (SEM)/ energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Adsorption studies were then undertaken with a synthetic effluent containing three textile dyes, viz., Reactive Blue 222 (RB 222), Reactive Red 195 (RR 195) and Reactive Yellow (RY 145). Various conditions were investigated including pH of the solution, temperature, sodium chloride concentration, initial dye concentration and the dosage of adsorbent used. The experimental data for all dyes followed a Langmuir isotherm. The adsorption process was found to be pseudo-second order. According to the thermodynamic parameters, the adsorption of the dyes was classified as physisorption and the reaction was spontaneous and exothermic. The data were also compared using studies with alumina as an adsorbent. Results showed that PRO-BEN exhibited better absorptivity and desorption than alumina making its use a better recyclable remediation strategy for the removal of organic dyes in wastewater treatment plants. In the second study, TEP was synthesized and then characterized by FT-IR Spectroscopy, 1H-NMR Spectroscopy, TGA and DLS. Thereafter, TEP was used to prepare TEP capped gold nanoparticles (TEP-AuNPs). Herein, two methods were investigated: the Turkevich method and an adaptation of the Turkevich method using bagasse extract. The TEP-AuNPs was characterized by FT-IR Spectroscopy, SEM, EDX, DLS and TEM. Thereafter the reduction of each of Allura Red, Congo Red and Methylene Blue was investigated with the TEP-AuNPs for its catalytic activity toward dye reduction. This study showed that the batch of AuNPs prepared by the Turkevich method had higher rates of dye reduction compared with AuNPs prepared using bagasse extract. Also the quantity of TEP used as capping agent greatly influenced the size, shape and surface charge of the nanoparticles as well as their catalytic performance: the Vroman effect explained this behavior of the TEP-AuNPs. It was finally concluded that whilst PRO-BEN, in the first study, showed excellent dye remediation properties, the second study on TEP-AuNPs showed good catalytic activity for the reduction of selected dyes, however, it was more effective at lower polymer concentration. Finally, both materials displayed good potential for the clean-up of selected synthetic dyes from synthetic effluents.