In this study, a carbon nanotube (CNT)-infused blended polymer membrane was prepared and evaluated for phenol and benzene removal from petroleum industry wastewater. A 25:75 (by weight %) blended polysulfone/polyethersulfone (PSF/PES) membrane infused with CNTs was prepared and tested. The effect of functionalization of the CNTs on the quality and performance of the membrane was also investigated. The membranes were loaded with CNTs at different loadings: 0.5 wt. %, 1 wt. %, 1.5 wt. % pure CNTs (pCNTs) and 1 wt. % functionalized CNTs (fCNTs), to gain an insight into the effect of the amount of CNT on the quality and performance of the membranes. Physicochemical properties of the as-prepared membranes were obtained using scanning electron microscopy (SEM) for morphology, Raman spectroscopy for purity of the CNTs, Fourier transform infrared (FTIR) for surface chemistry, thermogravimetric analysis (TGA) for thermal stability, atomic force microscopy (AFM) for surface nature and nano-tensile analysis for the mechanical strength of the membranes. The performance of the membrane was tested with synthetic wastewater containing 20 ppm of phenol and 20 ppm of benzene using a dead-end filtration cell at a pressure ranging from 100 to 300 kPa. The results show that embedding CNTs in the blended polymer (PSF/PES) increased both the porosity and water absorption capacity of the membranes, thereby resulting in enhanced water flux up to 309 L/m2h for 1.5 wt. % pCNTs and 326 L/m2h for 1 wt. % functionalized CNT-loaded membrane. Infusing the polysulfone/polyethersulfone (PSF/PES) membrane with CNTs enhanced the thermal stability and mechanical strength. Results from AFM indicate enhanced hydrophilicity of the membranes, translating in the enhancement of anti-fouling properties of the membranes. However, the % rejection of membranes with CNTs decreased with an increase in pCNTs concentration and pressure, while it increased the membrane with fCNTs. The % rejection of benzene in the pCNTs membrane decreased with 13.5% and 7.55% in fCNT membrane while phenol decreased with 55.6% in pCNT membrane and 42.9% in the FCNT membrane. This can be attributed to poor CNT dispersion resulting in increased pore sizes observed when CNT concentration increases. Optimization of membrane synthesis might be required to enhance the separation performance of the membranes.

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Environmental sustainability requires development of environmentally benign and energy efficient technology for treatment and disposal of wastewater. Membrane technology has emerged as a highly viable method for water treatment throughout the years. However, their limited commercial application has prompted a lot of researchers to explore different approaches to modify the membranes to enhance their performance. Polymer blending is one of the modifying techniques currently being explored to develop materials with unique anticipated properties depending on the type of membrane needed. This technique has shown improvement in the quality of the membrane by enhancing the mechanical strength as well as the performance of the membrane. In this study, blended polysulfone (PSF) and polyethersulfone (PES) membranes were synthesized at different PSF:PES ratios (100%:0%, 0%:100%, 50%:50%, 80%:20%, 20%:80% and 25%:75%) using N-Methyl-2-pyrrolidone (NMP) as a solvent via the phase inversion method. The quality and integrity of the membranes were checked via Scanning electron microscopy (for morphology); Thermogravimetric analysis (for thermal stability), Atomic force microscopy (for surface nature) and nanotensile measurement for mechanical strength. The flux, % rejection and porosity as the performance criteria of membranes showed a massive improvement in majority of the blended membranes than in pure PES and PSF membranes. AFM images indicated lower roughness in the pure PSF membrane as compared to the blended membranes. The tensile strength only improved on the 25%:75% membrane while the elasticity increased with an increase in PES concentration in the blended membranes. These results demonstrate the diversity of blending polymeric membranes to modify specific properties for desired function and highlight the possibility of more commercial application.

Production of yarn made of high purity carbon nanotubes (CNTs) is essential to novel macro-scale applications in the making of bulletproof vests, electrically conductive wire, antennas and mechanical actuators. In this study, which serves as a preliminary investigation towards optimization and scaling-up of production of high purity yarn using direct spinning of CNT bundles in a swirled floating catalyst chemical vapour deposition (SFCCVD), yarn was produced through direct spinning of CNT bundles. CNT bundles were synthesized in the SFCCVD reactor using acetylene as the carbon source and ferrocene as the catalyst. Effect of feed flow rate and reaction temperature on the production was investigated. Morphology, degree of defect and electrical conductivity of the as-produced yarn were checked using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), Raman spectroscopy and four-probe method, respectively. CNT yarn was successfully obtained at a reactor temperature of and at acetylene flow rate of 135 ml min−1. SEM micrographs of the fibrous structure show high degree of alignment parallel to the fibre direction with good consistency. Results from the four-probe method test show a typical linear ohmic behaviour indicating that the samples are electrically conductive. Higher reactor temperature favours the production of CNT yarn with a higher electrical conductivity and less crystalline defects.

Energy efficiency is a minimal cost energy resource. It is critical in bridging the gap via reducing overall demand, allowing electricity supply to be expanded to meet increasing demand in a timely and sustainable way. Incandescent bulbs with tungsten filaments convert only about 10% of the input energy into light with the rest wasted as heat and resultant carbon dioxide gas emissions. This results in high energy and environmental inefficiency. Carbon nanotubes (CNT) yarns as filaments for replacement of tungsten in incandescent bulbs represent an economic option boosting high energy and environmental efficiency. In this study, CNT yarns were produced from methane, an abundant greenhouse gas currently flared in Africa. Synthesis of CNT yarns were carried out in a Floating Catalyst Chemical Vapour Deposition (FCCVD) reactor using ferrocene as the catalyst with direct spinning of CNT into yarn. The quality and morphology of the produced yarns at different temperatures (900 – 1000°C) were determined using Scanning Electron Microscope (SEM) and Raman Spectroscopy. The optimum temperature to produce CNT yarns was found to be at reactor temperature of 950°C. The thermodynamics associated with the production of the as-spun CNT yarns were determined by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Heat capacity of CNT yarns was calculated based on the measured heat flow at thermal stable state. A polynomial regression of the form: Cp=0.002T2 – 0.4512T+66.099 was proposed for the prediction of the thermodynamic values. Change in thermodynamic quantities of yarn such as entropy and enthalpy were determined based on the heat capacities calculated from fitted polynomial models using relationship of thermodynamic function.

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