Characteristics of microporous/mesoporous carbons prepared from rice husk under base- and acid-treated conditions

The study reports the preparation of activated carbon with a high surface area from rice husk using chemical activation with H(3)PO(4) and ZnCl(2). Activated carbon prepared from rice husk usually exhibits low specific surface areas due to its high ash content. However, experimental results show that base-leaching and acid-washing processes can effectively enhance the adsorption capacity of rice-husk carbon. The study also investigates the effects of preparation parameters on the surface characteristics of the carbon. These parameters include the kind of activating agent, before and after treatment procedures, impregnation ratio and activation temperature. The chemical and physical properties of samples were examined by EA, ICP-MS, XRD, FTIR, SEM and a N(2)-adsorption meter. The surface areas obtained from ZnCl(2) and H(3)PO(4) activation are as high as 2434 and 1741 m(2)/g, respectively. These values are higher than that of activated carbon treated with neither base nor acid (1262 and 508 m(2)/g for ZnCl(2) and H(3)PO(4) activation). Thermogravimetric analysis shows that the activation process can be divided into three parts based on temperature zones. The results of this study will be useful in developing resource recovery systems for agricultural biomass.

Synthesis of zero-valent copper-chitosan nanocomposites and their application for treatment of hexavalent chromium

This study used ionotropic crosslinking to synthesize chitosan-tripolyphosphate chelating resin beads, which are used to fabricate zero-valent copper-chitosan nanocomposites. The copper nanoparticles were dispersed on chitosan-tripolyphosphate beads, and were thus able to maintain appropriate dispersion and stability, which greatly improves their applicability. The fabrication process contains two steps: using chitosan-tripolyphosphate beads to adsorb Cu(II) ions, followed by chemical reduction to reduce Cu(II) ions to zero-valent copper. This study explored the adsorption of synthesized chitosan-tripolyphosphate beads to Cu(II) ions, and used SEM/EDS, XPS, and TEM to examine the properties of zero-valent copper-chitosan nanocomposites. The results showed that, the adsorption behavior of hexavalent chromium from aqueous solution onto fabricated nanocomposites has better adsorption capacity than that of the chitosan-tripolyphosphate beads.

Chitosan, the marine functional food, is a potent adsorbent of humic acid

Chitosan is prepared by the deacetylation of chitin, the second-most abundant biopolymer in nature, and has applicability in the removal of dyes, heavy metals and radioactive waste for pollution control. In weight-reduction remedies, chitosan is used to form hydrogels with lipids and to depress the intestinal absorption of lipids. In this study, an experimental method was implemented to simulate the effect of chitosan on the adsorption of humic acid in the gastrointestinal tract. The adsorption capacity of chitosan was measured by its adsorption isotherm and analyzed using the Langmuir equation. The results showed that 3.3 grams of humic acid was absorbed by 1 gram of chitosan. The adsorption capacity of chitosan was much greater than that of chitin, diethylaminoethyl-cellulose or activated charcoal. Cellulose and carboxymethyl-cellulose, a cellulose derivative with a negative charge, could not adsorb humic acid in the gastrointestinal tract. This result suggests that chitosan entraps humic acid because of its positive charge.

Utilization of rice husk wastes in synthesis of graphene oxide-based carbonaceous nanocomposites

Rice husk is an agricultural waste-based biomass that can provide an alternative renewable source of bioenergy. Rice husk carbon and rice husk ash are major solid residues obtained after converting rice husk to bioenergy. This paper reports the synthesis of two graphene oxide-based activated carbons using rice husk carbon through H₃PO₄ and ZnCl₂ activation, respectively. By contrast, mesoporous silica was produced using recycled rice husk ash. Graphene oxide/ordered mesoporous carbon was prepared using mesoporous silica as a template source. These composites were inspected using a Raman spectrometer, Fourier transform infrared spectrometer, transmission electron microscope, field-emission scanning electron microscope, X-ray diffractometer, and surface area analyzer. Experimental results indicated that graphene oxide-based H₃PO₄ activated carbon, ZnCl₂ activated carbon, and ordered mesoporous carbon had a surface area of 361, 732, and 936 m²/g, respectively; a pore volume of 0.299, 0.581, and 1.077 cm³/g, respectively; and an average pore size of 2.31, 3.17, and 4.35 nm, respectively. The carbonaceous composites with graphene oxide exhibited a higher adsorption ability than did pure carbon materials without graphene oxide. The maximum adsorption capacities using methylene blue as adsorbate followed the order of ordered mesoporous carbon (1591 mg/g) > ZnCl₂ activated carbon (899 mg/g) > H₃PO₄ activated carbon (747 mg/g). The isothermal adsorption and kinetics study for graphene oxide/ordered mesoporous carbon indicated that adsorption followed the Langmuir isotherm model and pseudo-second order kinetic model. Rice husk waste has excellent prospective potential for producing highly valuable nanoproducts and for reducing environmental pollution.

Synthesis of TiO₂ Nanoparticles and Good Dispersion on SBA-15 Mesoporous Materials for High Photocatalytic Activity

This paper reports the preparation of TiO2 based photocatalysts from two different types of silica materials, silica gel and SBA-15. This study examines the factors that affect the photocatalytic activity of catalyst composite, such as types of silica support, TiO2 loading, and pH value of dye solution. The samples were characterized by XRD, UV-vis, FTIR, FE-SEM, TEM, TGA, and surface area analyzer. Experimental results show that TiO2 supported on silica gel or SBA-15 materials can effectively enhance photocatalytic reaction than unsupported catalysts. The TiO2/SBA-15 materials have larger pore volume and pore size compared to TiO2/silica-gel materials, which exhibited a much higher adsorption and photodegradation activity. The resulting mesoporous TiO2/SBA-15 had a high surface area of 574 m2/g, pore volume of 1.30 cm3/g, pore size of about 8.0 nm, and mesopore content as high as 100%. The results of this study will be useful in enhancing photocatalytic efficiency of TiO2 nanocatalyst materials.

A Sustainable Route to Synthesize Graphene Oxide/Ordered Mesoporous Carbon as Effect Nanocomposite Adsorbent

Rice husk is an agricultural waste that provides an alternative renewable source of bioenergy. Burning rice husk can produce rice husk ash. The rice husk ash is a potential resource of low-cost precursor for synthesizing high value-added materials. This paper reports the synthesis of SBA-15 mesoporous silica from recycled rice husk ash waste. Next, graphene oxide/ordered mesoporous carbon (GO/CMK-3) nanocomposite was synthesized using the SBA-15 template. The composite was investigated by X-ray diffractometer, field-emission scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectrometer, Raman spectrometer and surface area analyzer. Experimental results confirmed that GO/CMK-3 composite possessed high surface area (936 m²/g), large pore volume (1.077 cm³/g), and uniform pore size (4.35 nm). The mesopore structure was not destroyed by the introduction of GO. Methylene blue was employed as an adsorbate to evaluate the adsorption capacity of GO/CMK-3 composite. The GO/CMK-3 revealed much higher adsorption capacity levels than did pure CMK-3 and SBA-15. The adsorption capacity decreased with increasing solution temperature, and increasing initial concentration of dye. The thermodynamic observation indicated that the total adsorption process was spontaneous and exothermic. The conversion of rice husk ash waste into GO/CMK-3 composites can be regarded as an economically beneficial by-product for reducing environmental pollution.

Association between body composition and median neuropathy in patients with physical disabilities

BACKGROUND

Patients with physical disabilities more often have median neuropathies of the wrist and more than 70% of wheelchair users are overweight or obese.

AIM

To explore the effects of body composition on the occurrence of distal median neuropathy and to search for the best probabilistic cutoff value of indicators to predict the likelihood of developing distal median neuropathy in patients with physical disabilities.

DESIGN

A prospective study.

SETTING

A 1-day annual physical checkup program for employees of a social welfare organization.

POPULATION

In total, 72 patients with a physical disability (mean age ± SD, 40.0 ± 8.8 years; 40 women).

METHODS

Using electrophysiologic testing to assess distal median nerve function and using a dual-energy X-ray absorptiometry examination to assess body composition. The formula for leg exercise burden index (EBI) was: leg EBI = body fat mass of both legs/lean tissue mass of both legs.

RESULTS

The risk of developing a low median sensory nerve conduction velocity in the wrist-to-palm segment (< 43 m/s) was greater for patients with a higher leg EBI, yielding an adjusted odds ratio of 6.88 (P < 0.005). The body mass index (BMI) and being a wheelchair user were predictors of developing long median distal motor latency (> 4 ms). Using receiver operating characteristic analyses, we determined that patients with a physical disability were likely to develop distal median sensory neuropathy if they had a leg EBI of ≥ 0.943 and were likely to develop distal median motor neuropathy if they had a BMI of ≥ 24.5 kg/m2.

CONCLUSION

The leg EBI is a predictor of having distal median sensory neuropathy among patients with a physical disability.

CLINICAL REHABILITATION IMPACT

The value of the leg EBI can be useful information for identifying risk of distal median sensory neuropathy in patients with a physical disability.

Efficient Removal of Hazardous P-Nitroaniline from Wastewater by Using Surface-Activated and Modified Multiwalled Carbon Nanotubes with Mesostructure

P-nitroaniline (PNA) is an aniline compound with high toxicity and can cause serious harm to aquatic animals and plants. Multiwalled carbon nanotubes (MWCNTs) are a multifunctional carbon-based material that can be applied in energy storage and biochemistry applications and semiconductors as well as for various environmental purposes. In the present study, MWCNTs (CO2-MWCNTs and KOH-MWCNTs) were obtained through CO2 and KOH activation. ACID-MWCNTs were obtained through surface treatment with an H2SO4-HNO3 mixture. Herein, we report, for the first time, the various MWCNTs that were employed as nanoadsorbents to remove PNA from aqueous solution. The MWCNTs had nanowire-like features and different tube lengths. The nanotubular structures were not destroyed after being activated. The KOH-MWCNTs, CO2-MWCNTs, and ACID-MWCNTs had surface areas of 487, 484, and 80 m2/g, respectively, and pore volumes of 1.432, 1.321, and 0.871 cm3/g, respectively. The activated MWCNTs contained C-O functional groups, which facilitate PNA adsorption. To determine the maximum adsorption capacity of the MWCNTs, the influences of several adsorption factors-contact time, solution pH, stirring speed, and amount of adsorbent-on PNA adsorption were investigated. The KOH-MWCNTs had the highest adsorption capacity, followed by the CO2-MWCNTs, pristine MWCNTs, and ACID-MWCNTs. The KOH-MWCNTs exhibited rapid PNA adsorption (>85% within the first 5 min) and high adsorption capacity (171.3 mg/g). Adsorption isotherms and kinetics models were employed to investigate the adsorption mechanism. The results of reutilization experiments revealed that the MWCNTs retained high adsorption capacity after five cycles. The surface-activated and modified MWCNTs synthesized in this study can effectively remove hazardous pollutants from wastewater and may have additional uses.