Preparation and photocatalytic activity of mixed phase anatase/rutile TiO2 nanoparticles for phenol degradation

The evolution of desirable physico-chemical properties in high performance photocatalyst materials involves steps that must be carefully designed, controlled, and optimized. This study investigated the role of key parameter in the preparation and photocatalytic activity analysis of the mixed phase of anatase/rutile TiO2 nanoparticles, prepared via sol-gel method containing titanium-n-butoxide Ti(OBu)4 as a precursor material, nitric acid as catalyst, and isopropanol as solvent. The prepared TiO2 nanoparticles were characterized by means of XRD, SEM, and BET analyses, and UV-Vis-NIR spectroscopy. The results indicated that the calcination temperature play an important role in the physico-chemical properties and photocatalytic activity of the resulting TiO2 nanoparticles. Different calcination temperatures would result in different composition of anatase and rutile. The photocatalytic activity of the prepared mixed phase of anatase/rutile TiO2 nanoparticles was measured by photodegradation of 50 ppm phenol in an aqueous solution. The commercial anatase from Sigma-Aldrich and Degussa P25 were used for comparison purpose. The mixed phase of anatase/rutile TiO2 nanoparticles (consists of 38.3% anatase and 61.7% rutile) that was prepared at 400°C exhibited the highest photocatalytic activity of 84.88% degradation of phenol. The result was comparable with photocatalytic activity demonstrated by Degussa P25 by 1.54% difference in phenol degradation. The results also suggested that the mixed phase of anatase/rutile TiO2 nanoparticles is a promising candidate for the phenol degradation process. The high performance of photocatalyst materials may be obtained by adopting a judicious combination of anatase/rutile and optimized calcination conditions

Carbon membrane for gas separation: a short review

For the past 30 years, membrane technology has been prominently used for various gas purifications to obtain a high purity gas. Membrane acts as semipermeable wall, which the separation occurs by controlling the rate of movement of various molecules between two liquid phases or two gas phases or a liquid and a gas phase that passing through the membranes. Then, the advantages offered by membrane process such as simple operation with low energy consumption, low operating and capital cost, continuous process and unnecessary regeneration process compared to absorption and adsorption processes, have attracted considerable attentions by researchers. Besides, traditional methods such as pressure swing adsorption, cryogenic distillation and amine absorption which experienced with high energy consumption, expensive and lead to adverse impact on the environment has even made membrane process as preferable method for gas separation. Polymeric materials were used to develop a membrane that can attain high selectivity and permeability with high chemical and thermal resistance

Removal of lead(II) from aqueous solution using polyacrylonitrile/zinc oxide activated carbon nanofibers

This study aimed to prepare activated carbon nanofibers (ACNFs) from polyacrylonitrile (PAN) and zinc oxide (ZnO) via electrospinning process for removal of lead from aqueous solution. The ACNFs/ZnO were characterized in term of its morphological changes, specific surface area and functional groups analysis using Field Emission Scanning Electron Microscope (FESEM), Brunauer–Emmett–Teller (BET) and Fourier Transform Infrared (FTIR) analysis, respectively. The results showed that the specific surface area (SSA) of the ACNFs/ZnO were higher than the neat ACNFs which were 163.04 m2/g as compared to 67.6 m2/g, accordingly. FESEM analysis illustrated that composite ACNFs possessed more compact fibers with presence of ZnO beads and smaller fiber diameter whereas neat ACNFs possessed more aligned nanofibers with larger fiber diameter. Adsorption study showed that the composite ACNFs possessed higher capacity which was 120.3 mg/g as compared to 77.6 mg/g of neat ACNFs. This excellent adsorption performance of ACNFs PAN/ZnO exhibits the potential of this composite adsorbent to solve the environmental issue of heavy metal contamination

Preparation of composite activated carbon nanofibers (ACNFs) for adsorption of heavy metals

The objective of this study is to prepare a new and highly efficient nanomaterial for heavy metals adsorption. Owing to that, activated carbon nanofibers (ACNFs) from precursor polyacrylnitrile (PAN) and manganese oxide (MnO2) have been prepared via electrospinning process for removal of heavy metals (lead and cadmium) from aqueous solution. The PAN/MnO2-based ACNFs were characterized in term of its morphological changes, specific surface area and functional groups analysis using SEM, BET and FTIR analysis respectively. The results showed that the specific surface area (SSA) of the electrospun composite ACNFs was higher than the neat ACNFs which is 499m2/g as compared to 800m2/g. SEM analysis illustrated that composite ACNFs have more compact fibers with presence of MnO2 beads and smaller fiber diameter of 437.2 nm whereas neat ACNFs possessed more aligned nanofibers with average fiber diameter of 575.5 nm. From adsorption study, the removal of Pb (II) and Cd (II) using both ACNF/MnO2 and ACNFs were higher than the commercial GAC with the removal efficiency is 100% for Pb (II) and 97% for Cd (II). The high removal efficiency of ACNFs/MnO2 is attributed by its larger SSA, presence of functional groups that play role in adsorption process such as hyroxyl and carboxyl groups and the role of manganese oxide as adsorbent itself (Han,2006). This excellent adsorption performance of ACNFs exhibits the potential of this composite adsorbent to solve the environmental issue of heavy metal contamination

Effects of different loading of magnesium oxide on activated carbon nanofibers for methane adsorption

In the last few years, with the escalating world demand for energy, natural gas had been suggested as an alternative for replacing heavy fossil fuels as it produces cleaner combustion, less harmful and economical. Moreover, continuous world’s depending on fossil fuels such as crude oils, coals and heavy fuels has become a major concerned to the entire world as the excessive burning of these fuels produced harmful gases that leading to global warming. For this reasons, in this work, PAN- based activated carbon nanofibers (ACNFs) with various loading of magnesium oxide (MgO) (0, 5, 10, and 15 wt.%) were prepared for methane (CH4) adsorption. The nanofibers (NFs) were successfully produced via electrospinning process at optimize parameters. The resultant NFs underwent three steps of pyrolysis process which are stabilization, carbonization and activation at 275 oC, 600 oC and 800 oC, respectively. The ACNFs/MgO were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric (TGA) analysis, X-ray diffraction (XRD) analysis, Brunaeur, Emmett and Teller (BET) method and CH4 adsorption tests. The adsorption equilibrium of CH4 on ACNFs/MgO was measured using a static volumetric technique. Adsorption of CH4 on the ACNFs/MgO was conducted at 30 oC for pressures up to 4 bars. The equilibrium data were stimulated using the Freundlich and Langmuir isotherms, with both models having R2 > 0.98. The results on BET surface area showed the ACNFs loading with 15 wt.% MgO has the highest surface area of 1893.09 m2/g and it was assumed to be a major contributor for higher gas adsorption capacity. From these findings, it is believed that ACNFs/MgO will become a new adsorbent with great potential for gas adsorption and storage in the near future applications

Effect of P84 (BTDA-TDI/MDI) composition towards the performance of the disk supported carbon membrane

Carbon membrane has attracted researchers’ attention as it is superior in terms of its gas separation performance. In this study, the composition of polymer precursor in the dope solution was investigated based on carbon membrane performance. P84 polyimide was chosen as the polymer precursor as it fulfils the requirement for carbon membrane properties. By varying the polymer precursor composition (6, 9, 12, and 15 wt.%), P84 was stirred in NMP solvent until homogenous solution was formed. Commercialised alumina disc was coated via spray coating method at 1 bar at room temperature. The disc supported polymeric membrane was carbonised at 700 °C under nitrogen (200 ml/min) with heating rate of 3 °C/min. The carbon membrane was analysed via SEM. Gas permeation tests were performed using pure O2 and N2 at 4 bar at room temperature. The selectivity of 3.7 was obtained using the disc supported carbon membrane for O2/N2. The optimum polymer composition in this study was obtained by 12 wt.% of P84

PVDF/Fe2O3 mixed matrix membrane for oily wastewater treatment

Oily wastewater has been recognized as one of the most concerned environmental pollutions that come from a variety of sources. The increasing of these uncontrollable oily wastewater discharges consequently leads to environmental problems. The current barrier in this situation is when dealing with finely emulsified oily wastewater streams with small droplet size (< 20 μm in diameter). To tackle this issue, it is found that the utilization of the membrane technology is most effective due to its highly effective separation process and simplicity. Nevertheless, traditional filtration membranes are mostly afflicted with low flux and rejection rate as a consequence of easy fouling caused by the plugging of oil and surfactant. Thus, the wettability and antifouling properties of the membrane play an important role in dealing with this issue. The aim of this study was to evaluate the performance and operation of the membrane when treating oily wastewater. PVDF was chosen as the host polymer based on its outstanding properties and 0.2 wt% of Fe2O3 loading was utilized to enhance the hydrophilicity of the membrane. The effects of mixed matrix membrane (MMM) and neat poly (vinylidene fluoride) (PVDF) membrane relating to their differences in the SEM images, water flux and oil rejection were studied. The presence of additive in the polymeric composition has helped to achieve 40% higher flux increment with an oil removal efficacy of ~97 %, as compared to the unmodified PVDF membrane

Primary evaluation of COF-based mixed matrix membranes to antifouling property

Nowadays, anaerobic membrane bioreactors (AnMBRs) are one of the considerable wastewater treatment technologies. However, the performance of AnMBRs in wastewater treatment is faded due to the membrane fouling issue. Due to that concern, it gives a reason to find a material with high quality properties to prepare an antifouling membrane for the application in AnMBRs. In this present study, a new ultrafiltration (UF) membrane incorporated covalent organic framework (COF) was successfully constructed by interfacial polymerization method. A mixed-matrix membranes (MMMs) in various concentrations of COF range of 0 to 1 wt% was prepared and characterized by SEM, XRD, FTIR and AFM analysis. The analysis has confirmed the incorporation of the COF to the UF membrane. The effect of various COF concentration towards the antifouling property of the prepared membranes were evaluated. The results show, the increasing of COF concentration from 0 to 1 wt% has led to the increasing in the rejection rate from 26.11% to 95.87%. Besides, the membrane hydrophilicity significantly improved by 30.53%, when the water contact angle decreased from 66.94° to 46.50°. These results suggested that the PES/COF MMMs has great potential to offer an efficient separation with superior antifouling membrane for AnMBRs

Preparation of high performance SPEEK/Cloisite 15A nanocomposite membrane via advanced membrane formulation method

Sulfonated poly (ether ether ketone) (SPEEK)/Cloisite 15A® nanocomposite membranes were prepared via solution intercalation method. For better dispersion of nanoclay in the polymer matrix, the solution intercalation method was modified and a compatibilizer was introduced. The state of nanoclay dispersion was determined by FESEM. The effect of the solution formulation preparation method and compatibilizer on the performance properties such as proton conductivity and methanol permeability of all membranes was studied. FESEM analysis confirmed that SPEEK/Cloisite 15A® nanocomposite membrane prepared via modified solution intercalation method and in the presence of compatibilizer was the best membrane in terms of its morphological structure. Due to its well nanoclay distribution in polymer matrix, this kind of membrane exhibited the highest selectivity owing to its high proton conductivity and low methanol permeability. SPEEK/Cloisite 15A® with compatibilizer prepared via modified solution intercalation method was found to be the best membrane

Adsorption of cesium from aqueous solution using chitosan beads

Due to rapid population growth, technological advancement and industrial revolution, the rate of generated waste effluents has become a grave concern. Cesium, which possesses high fission yield, is generally transferred into liquid wastes, especially those emanated from nuclear power plants, reprocessing of spent fuels, nuclear weapon testing, and radionuclides production facilities for medical applications. Radiocesium (137Cs) is one of the hazardous radionuclides which have adverse effects on human health and the environment. Thus, from a health point of view, the removal of cesium from wastewater is imperative. Several techniques have been introduced as solution, and recently, adsorption has been gaining increasing attention among the scientific community owing to a number of reasons. Hence, this research presents an experimental work on sorption of cesium from wastewaters. In this study, chitosan was used as an adsorbent. The effects of several critical parameters, namely contact time, initial concentration, and absorbent dosage on the absorbent performance were investigated. From the findings, the optimum condition for the adsorption of cesium was optimized at pH 1 at 300 mg/L for 5 hours of contact time. The sorption data fitted well with Freundlich adsorption model, with the value of R2 = 0.9940, and was best described by pseudo-first-order model with the value of correlation coefficient, R2 = 0.9952