Zein, Collagen and PVA polymer fibre blends embedded with metal (Mn and Fe) oxide nanoparticles for wastewater treatment

Abstract

The polymer and their blended fibres provide good surface and intermolecular chemistry that bring additional functionalities and structural changes that can be adapted for new usages. Natural polymers are known to possess desirable qualities in terms of biocompatibility and biodegradability. The natural polymers are chosen due to their abundance but have difficulties in the preparations hence the addition of a synthetic polymer is vital. An important property of the polymer blended fibres is its miscibility which affects the mechanical properties, the morphology and degradation. Metal oxide nanoparticles embedded into polymer blended fibres enhances the performances of the polymer blended fibre permeability, selectivity, strength, and hydrophilicity. This study reports on the synthesis and characterization of zein, collagen nanofibres, zein/PVA fibre blends, iron oxide, manganese oxide nanoparticles, Fe2O3/zein /PVA and Mn2O3/zein/PVA fibre nanocomposite blends. The zein nanofibres and zein/PVA fibre blends were electrospun using electrospinning technique. Parameters such as the concentration and voltage were investigated. These parameters had an effect on the fibre morphology. The electrospun zein nanofibres and zein/PVA fibre blends were characterized using scanning electron microscopy (SEM), UV-Visible spectroscopy, Photoluminescence (PL), X-ray diffraction (XRD), Fourier transformer infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). The SEM results illustrated that an increase in the concentration of zein nanofibres improved the morphology of the fibres into ribbon like shape and had an effect on the average diameter size. The addition of PVA into zein nanofibres enhanced electrospinnabilty and the mechanical strength of zein was dependent on the presence of PVA. The optical properties, XRD, FTIR and thermal studies confirmed that zein/PVA (80/20) blend weight ratio was miscible and the other blend weight ratios remained immiscible, this was due to stronger interaction of hydrophilic performance of zein and PVA through hydrogen bonding. Therefore, fibre blend weight ratios of zein/PVA (90/10, 80/20, 70/30, 60/40 and 50/50) were successfully fabricated. The optimisation of collagen nanofibres favoured electrospraying instead of electrospinning hence collagen nanofibres could not be fabricated. Iron oxide nanoparticles was synthesized using hydrothermal method and manganese oxide nanoparticles was synthesized through co-precipitation method. The TEM results revealed well defined shapes of metal oxide nanoparticles illustrating that the increment of temperature had an influence on the crystallinity and particle size of 𝛼-Fe2O3 , 𝛼-MnO2 and 𝛼-Mn2O3 nanoparticles. The XRD confirmed the crystalline pattern of the metal oxide nanoparticles were of rhombohedral 𝛼-Fe2O3 structures (JCPDS 00-033-0664), cryptomelane phase 𝛼-MnO2 (JCPDS No. 29-1020) and orthorhombic crystalline phase of 𝛼-Mn2O3 (JCPDS No. 04-007-088). The metal oxide nanoparticles were thermally stable. Three different concentrations (4.25 wt%, 4.75 wt% and 5.25 wt %) of 𝛼-Fe2O3 and 𝛼- Mn2O3 were embedded onto zein/PVA (80/20) fibre blends and electrospun. The SEM, optical properties, XRD and TGA confirmed that the embedment of metal oxide nanoparticles enhanced the zein/PVA fibre blends performance, mechanical strength and resistance to wear therefore 5.25 wt% of 𝛼-Fe2O3/zein/PVA and 𝛼-Mn2O3/zein/PVA were explored further for the adsorption of chrysoidine G removal from wastewater. The adsorption studies of zein/PVA (80/20), 𝛼-Fe2O3/zein/PVA and 𝛼-Mn2O3/zein/PVA were carried out in a batch system on the effects of contact time, pH, initial concentration and adsorbent dosage. All the nanoadsorbents could rapidly reach adsorption equilibrium within 30 min at room temperature. The maximum removal efficiency of chrysoidine G of zein/PVA, 𝛼-Mn2O3/zein/PVA was higher than 𝛼-Fe2O3/zein/PVA. The dye adsorption equilibrium data were well-fit with Langmuir isotherm rather than Freundlich isotherm. The comparison of kinetic models revealed that the overall adsorption process was described well by pseudo second-order kinetics. The polymeric materials were cost effective hence regeneration studies were implemented for three cycles. These nanoadsorbents are easily available and are expected to be economical.