Dye removal from waste water via adsorption by activated carbons (ACs) developed from agricultural wastes represents an ideal alternative to other expensive treatment options. Physical and chemical ACs were prepared from rice husks. The textural properties of the ACs were characterized by Brunauer-Emmett-Teller-N2 adsorption and scanning electron microscopy. The chemistry of the carbon surface was investigated by Fourier transform infrared spectroscopy, base and acid neutralization capacities, pH of the active carbon slurry, and pHpzc. The adsorption capacities of the ACs for the basic dye (methylene blue) and acid dye (acid green 25) were determined using parameters such as contact time, pH, and temperature. NaOH-ACs showed the highest surface area and total pore volume, whereas steam-ACs showed the lowest ones.
Graphene is the thinnest known materials in the universe and the strongest ever measured. Graphene has emerged as an exotic material of the 21st century and received world-wide attention due to its exceptional charge transport, thermal, optical, mechanical, and adsorptive properties. Recently, graphene and its derivatives are considered promising candidates as adsorbent for H2 storage, CO2 capture, etc. and as the sensors for detecting individual gas molecule. The main purpose of this review is to comprehensive the synthesis method of graphene and to brief the adsorption behaviors of graphene and its derivatives.
Polypyrrole (PPy)/multi-walled carbon nanotubes (MWCNTs) composites were prepared by in situ polymerization of pyrrole on the surface of MWCNTs templates to improve the ammonia gas sensing properties. PPy morphologies, formed on the surface of MWCNTs, were investigated by field emission scanning electron microscopy. The thermal stabilities of the PPy/MWCNTs composites were improved as the content of MWCNTs increased due to the higher thermal stability of the MWCNTs. PPy/MWCNTs composites showed synergistic effects in improving the ammonia gas sensing properties, attributed to the combination of efficient electron transfer between PPy/MWCNTs composites and ammonia gas, and the reproducible electrical resistance variation on PPy during the gas sensing process.
Herein, macroporous carbon foams were successfully prepared with phenol and formaldehyde as carbon precursors and an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6), as a pore generator by employing a polymerization-induced phase separation method. During the polycondensation reaction of phenol and formaldehyde, BMIPF6 forms a clustered structure which in turn yields macropores upon carbonization. The morphology, pore structure, electrical conductivity of carbon foams were investigated in terms of the amount of the ionic liquid. The as-prepared macroporous carbon foams had around 100-150 μm-sized pores. More importantly, the electrical conductivity of the carbon foams was linearly improved by the addition of BMIPF6. To the best of the author's knowledge, this is the first result reporting the possibility of the use of an ionic liquid to prepare porous carbon materials.
The sol-gel technique has been studied to fabricate a homogeneous Fe-Mo/MgO catalyst. Ambient effects (air, Ar, and H2) on thermal decomposition of the citrate precursor have been systematically investigated to fabricate an Fe-Mo/MgO catalyst. Severe agglomeration of metal catalyst was observed under thermal decomposition of citrate precursor in air atmosphere. Ar/H2 atmosphere effectively restricted agglomeration of bimetallic catalyst and formation of highly-dispersed Fe-Mo/MgO catalyst with high specific surface-area due to the formation of Fe-Mo nanoclusters within MgO support. High-quality thin-multiwalled carbon nanotubes (t-MWCNTs) with uniform diameters were achieved on a large scale by catalytic decomposition of methane over Fe-Mo/MgO catalyst prepared under Ar-atmosphere. The produced t-MWCNTs had outer diameters in the range of 4-8 nm (average diameter ~6.6 nm) and wall numbers in the range of 4-7 graphenes. The as-synthesized t-MWCNTs showed product yields over 450% relative to the utilized Fe-Mo/MgO catalyst, and indicated a purity of about 85%.
A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride (CCl4) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of CCl4 concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against CCl4 vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by N2 adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against CCl4 vapours. The breakthrough time decreased with the increase of the CCl4 concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of CCl4, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low CCl4 vapour concentration.
Most heavy metals are well-known toxic and carcinogenic agents and when discharged into wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. The present study aims to develop a procedure for Pb(II) removal. The study was based on using powdered activated carbon, which was prepared from walnut shells generated as plant wastes and modified with potassium carbonate or phosphoric acid as chemical agents. The main parameters, such as effect of pH, effect of sorbent dosage, Pb(II) concentrations, and various contact times influence the sorption process. The experimental results were analyzed by using Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich adsorption models. The kinetic study of Pb(II) on activated carbon from walnut shells was performed based on pseudo-first order and pseudo-second order equations. The data indicate that the adsorption kinetics follow the pseudo-second order rate. The procedure was successfully applied for Pb(II) removal from aqueous solutions.
In the present work, exfoliated graphite nanoplatelets (EGN) of 1 μm in average particle size, which were prepared by heating at 900℃ and then subjected to ultrasonic, ball-milling, and vibratory ball-milling techniques, were uniformly incorporated into phenylethynyl-terminated polyimide (PETI-5) resin. The fracture surface morphology and the electrical resistivity of the EGN/PETI-5 composites were investigated. The results showed that the fracture surfaces and the electrical resistivity strongly depended on the EGN content. The fracture surfaces became more ductile and roughened with increasing EGN and the electrical resistivity was gradually decreased with increased EGN loading, indicating the percolation threshold at 5 wt% EGN.
Nanocomposite films were made by a simple solution casting method in which multi-walled carbon nanotubes (MWCNT) and magnetite nanoparticles (Fe3O4) were used as dopant materials to enhance the electrical conductivity of chitosan nanocomposite films. The films contained fixed CNT concentrations (5, 8, and 10 wt%) and varying Fe3O4 content. It was determined that a 1:1 ratio of CNT to Fe3O4 provided optimal conductivity according to dopant material loading. X-ray diffraction patterns for the nanocomposite films, were determined to investigate their chemical and phase composition, revealed that nanoparticle agglomeration occurred at high Fe3O4 loadings, which hindered the synergistic effect of the doping materials on the conductivity of the films.
In this study, cobalt oxide (Co3O4)/graphene composites were synthesized through a simple chemical method at various calcination temperatures. We controlled the crystallinity, particle size and morphology of cobalt oxide on graphene materials by changing the annealing temperatures (200, 300, 400℃). The nanostructured Co3O4/graphene hybrid materials were studied to measure the electrochemical performance through cyclic voltammetry. The Co3O4/graphene sample obtained at 200℃ showed the highest capacitance of 396 Fg-1 at 5 mVs-1. The morphological structures of composites were also examined by scanning electron microscopy and transmission electron microscopy (TEM). Annealing Co3O4/graphene samples in air at different temperatures significantly changed the morphology of the composites. The flower-like cobalt oxides with higher crystallinity and larger particle size were generated on graphene according to the increase of calcination temperature. A TEM analysis of the composites at 200℃ revealed that nanoscale Co3O4 (~7 nm) particles were deposited on the surface of the graphene. The improved electrochemical performance was attributed to a combination effect of graphene and pseudocapacitive effect of Co3O4.