Browsing by Author "De Kock, Lueta-Ann"

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    A comprehensive adsorption study of 1-Hydroxy-2-Naphthoic acid using cost effective engineered materials
    (Elsevier, 2020-05-16) Zeb, Muhammad Aurang; Murtaza, Ghulam; Hussain, Muhammad Aamer; Kubra, Khadija Tul; Muvhiiwa, Ralph; De Kock, Lueta-Ann; Hassard, Francis
    The naphthoic acids are challenging and costly to remove from water and soil. 1-Hydroxy-2-Naphthoic acid (HNA) is a phenanthrene decomposition product from petroleum-contaminated environments during the aerobic decomposition of polyaromatic hydrocarbons. The hydrogeological mobility of hydrocarbon breakdown products represent a pollution risk (e.g. for drinking water sources). Adsorption to biochar produced from agricultural by-products is a useful strategy to remediate contaminated wastewaters. Here, we examine the controls on the HNA adsorption to the adsorbents magnetite, clay minerals, biochar and magnetite enriched companion materials, namely the influence of contact time, contaminant concentration and ionization effects at different pH. The adsorption of HNA was investigated using low-cost and readily available adsorbents: (i) wheat straw biochar, (ii) rice husk biochar, (iii) sugarcane biochar, (iv) zeolite, (v) montmorillonite, (vi) magnetite and their enriched magnetic companions. Magnetite enriched biochar exhibited greater adsorption rates compared with their nonmagnetic analogs for HNA. The maximum adsorption capacity of the magnetite enriched compounds (initial water concentration of 0.32 mmol HNA.L) was 0.45 mmol.HNA.g of enriched zeolite. The magnetite enriched biochar and conventional biochar showed similar adsorption kinetics although magnetite enrichment improved the efficacy of adsorption. The adsorption fitted the pseudo-second order model in all cases, suggesting the dominant mechanism of adsorption was chemisorption. The magnetite enrichment reduced intra-particle diffusion, possibly due to fouling or blocking of pores within the particles, as evidenced by the decrease in diffusion rate constants. Overall, HNA adsorption improved after magnetic enrichment due to magnetite competing with inhibition sites on the biochar carriers. These findings translate into equivalence between magnetite and magnetic biochars, suggesting cheaper alternative materials could be synthesized in situ with the biochar acting as both an adsorbent and carrier, increasing the prospect of designer biochars for targeted pollutant removal. This approach has the potential to be used for wastewater treatment or for application as a soil additive for remediation of runoff from contaminated soils.
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    Interactions between organic model compounds and ion exchange resins
    (American Chemical Society , 2019-07-22) Finkbeiner, Pascal; Moore, Graeme; Tseka, Tebogo; Nkambule, Thabo; De Kock, Lueta-Ann; Jefferson, Bruce; Jarvis, Peter Robert
    Ion exchange (IEX) can successfully remove natural organic matter (NOM) from surface water. However, the removal mechanism is not well understood due to the complexity and variability of NOM in real source waters as well as the influence of multiple parameters on the removal behaviour. For example, this includes the physicochemical properties of the NOM and IEX resin, and the presence of competing anions. Model compounds with a range of physical and chemical characteristics were therefore used to determine the mechanisms of NOM removal by IEX resins. Fifteen model compounds were selected to evaluate the influence of hydrophobicity, size and charge of organic molecules on the removal by ion exchange, both individually and in mixtures. Three different resins, comprising polystyrene and polyacrylic resin of macroporous and gellular structure, showed that charge density (CD) was the most important characteristic that controlled the removal, with CD of >5 meq mgDOC-1 resulting in high removal (≥89%). Size exclusion of compounds with high MW (≥8 kDa) was evident. The hydrophobicity of the resin and model compound was particularly important for removal of neutral molecules such as resorcinol, which was best removed by the more hydrophobic polystyrene resin. Relationships were identified that provided explanations of the interactions observed between NOM and IEX resin in real waters.
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    Multifunctional heterogeneous ion-exchange membranes for ion and microbe removal in low-salinity water
    (MDPI, 2023-02-08) Mudau, Fulufhelo Hope; Hassard, Francis; Motsa, Machawe Mxolisi; De Kock, Lueta-Ann
    Here, multifunctional heterogeneous ion-exchange metal nanocomposite membranes were prepared for surface water desalination and bacterial inactivation under low-pressure (0.05 MPa) filtration conditions. Ultrafiltration (UF) heterogeneous ion exchange membranes (IEMs) were modified with different concentrations of AgNO3 and CuSO4 solutions using the intermatrix synthesis (IMS) technique to produce metal nanocomposite membranes. Scanning electron microscopy (SEM) images revealed that the metal nanoparticles (MNPs) (Ag and Cu) were uniformly distributed on the surface and the interior of the nanocomposite membranes. With increasing metal precursor solution concentration (0.01 to 0.05 mol·L−1), the metal content of Ag and Cu nanocomposite membranes increased from 0.020 to 0.084 mg·cm−2 and from 0.031 to 0.218 m·cm−2 respectively. Results showed that the hydrodynamic diameter diameters of Ag and Cu nanoparticles (NPs) increased from 62.42 to 121.10 nm and from 54.2 to 125.7 nm respectively, as the metal precursor concentration loaded increased. The leaching of metals from metal nanocomposite membranes was measured in a dead-end filtration system, and the highest leaching concentration levels were 8.72 ppb and 5.32 ppb for Ag and Cu, respectively. The salt rejection studies indicated that ionic selectivity was improved with increasing metal content. Bacterial filtration showed higher antibacterial activity for metal nanocomposite membranes, reaching 3.6 log bacterial inactivation.
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    Quantifying the performance of a hybrid anion exchanger/adsorbent for phosphorus removal using mass spectrometry coupled with batch kinetic trials
    (Taylor and Francis, 2017-07-20) Martin, Benjamin D.; De Kock, Lueta-Ann; Gallot, Maxime; Guery, Elodie; Stanowski, Sylvain; MacAdam, Jitka; McAdam, Ewan J.; Parsons, Simon A.; Jefferson, Bruce
    Increasingly stricter phosphorus discharge limits represent a significant challenge for the wastewater industry. Hybrid media comprising anionic exchange resins with dispersions of hydrated ferric oxide nanoparticles have been shown to selectively remove phosphorus from wastewaters, and display greater capacity and operational capability than both conventional treatment techniques and other ferric-based adsorbent materials. Spectrographic analyses of the internal surfaces of a hybrid media during kinetic experiments show that the adsorption of phosphorus is very rapid, utilising 54% of the total capacity of the media within the first 15 min and 95% within the first 60 min. These analyses demonstrate the importance of intraparticle diffusion on the overall rate in relation to the penetration of phosphorus. Operational capacity is a function of the target effluent phosphorus concentration and for 0.1 mg P L−1, this is , which is 8–13% of the exhaustive capacity. The adsorbed phosphorus can be selectively recovered, offering a potential route to recycle this important nutrient. The main implication of the work is that the ferric nanoparticle adsorbent can provide a highly effective means of achieving a final effluent phosphorus concentration of 0.1 mg P L−1, even when treating sewage effluent at 5 mg P L−1.
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    Resin-loaded heterogeneous polyether sulfone ion exchange membranes for saline groundwater treatment
    (MDPI, 2022-07-27) Mudau, Fulufhelo; Motsa, Machawe; Hassard, Francis; De Kock, Lueta-Ann
    Arid areas often contain brackish groundwater that has a salinity exceeding 500 mg/L. This poses several challenges to the users of the water such as a salty taste and damage to household appliances. Desalination can be one of the key solutions to significantly lower the salinity and solute content of the water. However, the technology requires high energy inputs as well as managing waste products. This paper presents the fabrication of ultrafiltration heterogeneous ion exchange membranes for brackish groundwater treatment. Scanning electron microscopy (SEM) images showed a relatively uniform resin particle distribution within the polymer matrix. The mean roughness of the cation exchange membrane (CEM) and anion exchange membrane (AEM) surfaces increased from 42.12 to 317.25 and 68.56 to 295.95 nm, respectively, when resin loading was increased from 1 to 3.5 wt %. Contact angle measures suggested a more hydrophilic surface (86.13 to 76.26° and 88.10 to 74.47° for CEM and AEM, respectively) was achieved with greater resin loading rates. The ion exchange capacity (IEC) of the prepared membranes was assessed using synthetic groundwater in a dead-end filtration system and removal efficiency of K+, Mg2+, and Ca2+ were 56.0, 93.5, and 85.4%, respectively, for CEM with the highest resin loading. Additionally, the anion, NO3− and SO42− removal efficiency was 84.2% and 52.4%, respectively, for the AEM with the highest resin loading. This work demonstrates that the prepared ultrafiltration heterogeneous ion exchange membranes have potential for selective removal for of ions by ion exchange, under filtration conditions at low pressure of 0.05 MPa.