206 research outputs found
Polyaniline/Fe-0 composite nanofibers: An excellent adsorbent for the removal of arsenic from aqueous solutions
No full textA novel nano-scale polyaniline/Fe-0 composite (termed as PANI/Fe-0) was synthesized via reductive deposition of nano-Fe-0 onto the PANI nanofibers matrix at room temperature. PANI/Fe-0 was characterized by SEM, TEM, XRD, FTIR and XPS. PANI/Fe-0 was tested for arsenic removal in batch experiments. The effects of initial pH value, adsorbent mass loading, As initial concentration, and co-solutes on As removal were explored. Results showed nano-Fe-0 particles with average diameter 6.4 nm embedded onto the PANI matrix. As removal was rapid for both As(III) and As(V) species. The equilibrium isotherm data fitted well with Langmuir isotherm model. The maximum adsorption capacities at pH 7.0 for As(III) and As(V) were 232.5 and 227.3 mg/g, respectively. These capacities are significantly higher than most of the reported adsorbents. The co-existing HCO3-, SiO32-, and SO42- ions had no significant effect on As removal. However, the presence of NO3- and PO43- significantly reduced the As removal efficiencies. Achieved results further show that PANI/Fe-0 is a promising adsorbent for safe drinking provision in low-income communities owing to its excellent performance, simple and low-cost synthesis process. (C) 2015 Elsevier B.V. All rights reserved
Synthesis and characterization of metal/metal oxide supported nano-catalysts for nitro arenes reduction
No full textAbstract: Please refer to full text to view abstract.Ph.D. (Chemistry
Iron nanoparticles derived from rooibos tea extract supported polymer for Cr⁶⁺ removal
No full textMSc (Chemistry ), North-West University, Mafikeng CampusDeterioration of water quality due to the presence of toxic heavy metals in environmental water resources introduced by industrial pollution is a serious matter of concern today. Only around 20% of the global wastewater was properly treated until 2015. Furthermore, in developing countries, approximately 70% of the industrial wastewater is not properly discharged. Chromium is a common heavy metal contaminant with two major species that is the, trivalent Cr(III) and hexavalent Cr(VI). Due to its higher solubility and mobility in environments, Cr(VI) is highly toxic and carcinogenic while Cr(III) is an essential micronutrient in trace amount for mammals. Therefore, the objective of the study was to synthesize low-cost Fe0 nanoparticles (NPs) supported in polypyrrole (Ppy) to investigate their effectiveness in Cr(VI) removal from aqueous solutions. Moreover, the effect of temperature, contact time, pH, adsorbent dose, and effect of co-existing ions were assessed. Ppy/Fe⁰ nanocomposite (NC) was characterized using various techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), Braunner-Emmet-Teller (BET) and X-ray diffractometry (XRD). An increase in Cr(VI) removal due to pH was observed when pH was increased, the removal decreased from 73 - 32% and the optimum was at pH 2.0. The kinetic adsorption data ?tted the pseudo-second-order model. The adsorption isotherm followed the Langmuir isotherm model with the maximum sorption capacity of 305.8 mg.g⁻¹ at 25 °C and the adsorption process was endothermic. The specific surface area of the synthesized nanocomposite was calculated to be 80.53 m².g⁻¹ by the BET method. TEM images clearly showed the core/shell structure of the Ppy/Fe⁰ NC. Based on the findings from the study, it is hypothesized that results obtained may assist the wastewater treatment field with easy and safe removal of heavy metals from water.Master
Risk assessment of nano-pollutants released from select nano-enabled products in fresh and wastewater
No full textM.Sc. (Applied Chemistry)Abstract: Products that contain engineered nanomaterials (ENMs) are called nano-enabled products (NEPs) and they exhibit varying extent to emit ENMs into environment as nanopollutants. The ENMs are an emerging class of environmental contaminants of which their potential environmental risk is yet to be fully understood. Sunscreens can be incorporated with ENMs, commonly titanium dioxide (TiO2) ENMs in order to enhance UV absorption and protection against UV rays. Sunscreens are a dominant NEP type across international markets and exhibit high likelihood to release ENMs into the environment as the ENMs are suspended in liquid and cream, hence they are a priority source of nanopollutants specifically into waste and natural water systems. The current study examined the characteristics of ENMs incorporated in sunscreens as well as those released from sunscreen use. A sample of four sunscreens enabled with TiO2 ENMs (A–D) and one (E) containing TiO2 were selected. An extraction protocol infusing solvent and physical separation steps was adopted to extract the ENMs from the sunscreens. The extracts were examined by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Ultraviolet and Visible Spectrophotometry (UV/Vis), Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), and the nanoparticle tracking analysis (NTA) in order to characterise and quantify the ENMs for size, shape, and concentration properties. The presence of TiO2 ENMs was confirmed in all the sunscreen samples. The modal sizes of the TiO2 ENMs obtained from SEM analysis for sunscreen A, B, C, and E were 67.6, 69.8, 51.8, and 106.5 nm respectively and no TiO2 ENM was detected in sunscreen D with EDS. From analysis with TEM the modal sizes for sunscreen A, B, and C were 73.9, 81.5 and 44.7 nm respectively. Sunscreens D and E were not examined with TEM. The ENMs were predominantly of needle-like, plate, rod, and irregular shapes. The concentration of TiO2 ENMs in sunscreen A, B, C and E were 1.9, 0.6, 0.5 and 2.1 %w/w respectively, whereas it was below detection level in sunscreen D. Overall,.
Groundwater purification using functionalised magnetic nanoparticles (electromagnetic separation)
No full textMost developing countries are faced with drinking water problems, with conditions becoming more severe due to water pollution. Meeting the growing demands for clean water in most countries, there are difficult challenges as the availability and supply of drinkable water are diminishing. Due to economic and environmental concerns, development of additional physical means for the removal of organic compounds from wastewater using permanent magnets, electromagnetic coils, electrodes and ultrasonic pretreatment is desirable. Improving the adsorption and separation process, magnetic field exposure method has progressively drawn consideration. Magnetic field exposure method has demonstrated its capacity for increasing the adsorptive elimination of contaminants from water as static magnetization is suitable, simple and cost-effective.
The polypyrrole magnetic nanocomposite use for adsorption experiments influenced by exter-nal magnetic field was prepared using the in-situ polymerization method, which was charac-terized using TEM, SEM, EDX, XRD, BET, FTIR, VSM, and ESR spectrophotometers. The magnetic nanocomposite (PPy/Fe3O4) was observed to have an average particle size of 10 nm with the elementary composition of carbon, oxygen, nitrogen, chloride and iron. The magnetic nanocomposite had a crystalline structure of face-centred cubic lattice of Fe3O4, an adsorption-desorption isotherm shape indicating a typical type-IV mesoporous material with a surface area of 28.77 m2/g. Characteristic peaks of Fe3O4 and PPy were also observed using FTIR spectro-photometer. From the VSM and ESR characterization, the synthesized superparamagnetic ma-terial was shown to have a saturation magnetization of 23 emu/g and an effective g-value of 2.25 g which was attributed to Fe3+ spin interaction.
An enhanced removal of Cr(VI), fluoride and congo red dye were observed under the influence of magnetic field, with parameters like pH, adsorbent dosage, the initial concentration of ad-sorbate, magnetic field and magnetic exposure time been varied. The enhanced adsorption of contaminants using magnetic field is attributed to the increase in the magnetic field induced on the particles over a magnetic exposure time, resulting in the rotating particles forming aggre-gates due to the increased magnetic force and torque on the particles from the PSV results. This leads to increase in the chain collision and area of particle interaction with the aqueous solution of hexavalent chromium, fluoride and congo red dye.Ph. D. (Physics)Physic
A Water Dispersible Nanocomposite of Polyacrylonitrile with Silica via Aqueous Polymerization of Acrylonitrile by K2CrO4–NaAsO2 Redox System
No full text
- …
