Polyvinylidene fluoride membranes impregnated at optimised content of pristine and functionalised multi-walled carbon nanotubes for improved water permeation, solute rejection and mechanical

Multi-walled carbon nanotubes functionalised by plasma oxygen (CNTs) have been used as heterogeneous catalysts for the ozonation of methyl orange (MO) dye (CI 13025) in aqueous solutions. It was found that the addition of CNTs significantly enhanced the dye decolourisation as compared to ozone alone or when activated carbon was used at the same dose as CNTs. Both the initial ozone concentration and catalyst dosage enhanced the removal of MO. However, ozone gas concentrations higher than 6 g/m 3 NTP did not improve any further the decolourisation rates. The removal efficiency of MO increased with pH in the range 2 to 3, while a reverse trend was observed when the pH increased from 3 to 9. The addition of a radical scavenger resulted in only a limited change in the decolourisation rates suggesting that molecular ozone was the main pathway by which MO decolourisation occurred in solution. However, under favourable conditions for MO attraction to CNT surface (pH=3), the decolourisation rate has significantly increased. At higher pH than the pKa value of MO (3.47) and the point of zero charge of CNT (3.87), a condition that favours the electrostatic repulsion of MO from CNT, the rates were reduced in the presence of CNT as compared to ozone alone possibly due to loss of part of the supplied ozone in un-useful parallel reactions.

is a widely used polymeric material for ultrafiltration or nanofiltration membranes. To enhance membrane permeability, rejection, and antifouling performance, the effect of four different types of carbon-based nanomaterials and air exposures during PES/carbon-based nanomaterial membrane fabrication was evaluated. The carbon-based nanomaterials were pristine carbon nanotubes, oxidized CNTs (CNTs-O), pristine graphene nanoplatelets (GNPs-P), and oxidized graphene nanoplatelets (GNPs-O). The characteristics and performances of pure and blended membranes were investigated based on their permeability, porosity, morphology, and hydrophobicity. Longer air contact time during membrane preparation resulted in lower membrane permeability, hydrophobicity, and porosity. All fabricated membranes tended to have channelled sponge-like structure, and highest permeability was attributed to the PES/GNPs-O membrane.

This research demonstrates for the first time that ozone is an effective cleaning agent for polyvinylidene fluoride (PVDF) membranes fouled by natural organic matter (NOM). Bare PVDF membranes as well as PVDF impregnated with CNTs (pristine (CNTs-P) and oxidized (CNTs-O)) at 0.3 %mass membranes were used. Three different methods were investigated for cleaning the fouled membranes including; A: 10min cleaning by pure water, B: 5min water followed by 5min ozonated water, and C: 10min fully ozonated water. It was found that the application of fully ozonated water for 10 minutes was very effective to reinstate the flux to almost its original value of un-fouled membrane. The CNTs-P/PVDF membrane exhibited the highest fouling with a total fouling ratio of 81% whilst for the bare PVDF and the CNTs-O/PVDF membranes, the fouling ratios were 76% and 74%, respectively. The full ozonated water cleaning method gave the highest removal of fouling leaving the lowest irreversible fouling on the membrane as compared to the other cleaning methods. On the other hand, the highest removal of NOM fouling was obtained for CNTs-O/PVDF membranes indicating that fouling on CNTs-O/PVDF membrane was less bound than the other membranes. Contact angle measurements of the fouled membranes showed that all membranes exhibited increased contact angles due to the NOM deposition but after cleaning, particularly with ozonated water, the membrane contact angles returned to almost their original values. FTIR analysis of the membranes corroborated the results obtained.

In this study, biosynthesis of silver nanoparticles using the extract of a local banana peel (variant name: Raja) as bio-reductor was carried out. This study aimed to determine the effect of two different ratios of Banana Peel Extract (BPE)/distilled water on the synthesis of silver nanoparticles. The two of BPE/water ratios were 1% (v/v) and 5%(v/v), named as Sample A and Sample B, respectively. Whereas, the concentrations of AgNO3 solution as the precursor were varied as follows: 0.125; 0.1; 0.075; and 0.05 M. The synthesized colloidal silver nanoparticles were characterized using a UV-Vis spectrometer, while the BPE solution was analyzed using Fourier Transform Infra-Red (FT-IR) to study its functional groups. While, the solid silver nanoparticles was characterized using a Scanning Electron Microscopy (SEM) with an Energy-dispersive X-ray spectroscopy (EDX) analysis. The UV-Vis spectrometer results qualitatively showed that sample A produced better silver nanoparticles than that of sample B. All samples showed absorbance peaks at wavelength of 450 nm. It was found that the highest absorbance value (i.e. 1.59) occurred at sample A with a concentration of AgNO3 solution 0.1 M. Additionally, FT-IR analysis result showed the presence of a hydroxyl group specifically for alcohols as phenols, which indicated the possibility of polyphenol compounds. The SEM micrograph showed that some of the silver nanoparticles were in the shape of tetrahedron or triangular like particle and spherical The SEM image analysis results using ImageJ software showed that most of the silver nanoparticles produced had the size of 100-300 nm. Furthermore, the EDX analysis result showed a peak count at 3 keV, which confirmed the formation of silver nanoparticles.