Yupeng Guo

Adsorption of malachite green on micro- and mesoporous rice husk-based active carbon

The adsorption of malachite green (MG) from aqueous medium by rice husk-based porous carbons (RHCs) were studied. The extent of adsorption was studied as a function of pH, contact time, contact temperature, adsorbate concentration, ion strength and adsorbent with different pore structural. The comparison of adsorption of MG on oxidized carbons and their heat-treated derivatives were studied. The results obtained under various experimental conditions were found to follow the Freundlich adsorption isotherm. The adsorption capacity of carbons activated by NaOH-activation was larger than that of carbons activated by KOH-activation, the adsorption of MG on oxidized carbons was decreased and was enhanced after heat-treatment.

Application studies of activated carbon derived from rice husks produced by chemical-thermal process—A review

The production of functional activated carbon materials starting from cheap natural precursors using environmentally friendly processes is a highly attractive subject in material chemistry today. Recently, much attention has been focused on the use of plant biomass to produce functional carbonaceous materials, encompassing economic, environmental and social issues. Besides the classical route to produce activated carbons from fossil materials, rice husk shows clear advantages in that it can generate a variety of cheap and sustainable carbonaceous materials with attractive nanostructure and functional patterns for a wide range of applications. From a comprehensive literature review, it was found that porous carbon that derived from rice husks, in addition to having wide availability, has fast kinetics and appreciable adsorption capacities too. Porous carbon materials also play a significant role in new applications such as catalytic supports, battery electrodes, capacitors, and gas storage. In this review, an extensive list of rice husks literature has been compiled. Conclusions have been drawn from the literature reviewed, and suggestions for future research are proposed.

Adsorption of Cr(VI) on micro- and mesoporous rice husk-based active carbon

The adsorption of hexavalent chromium from aqueous medium by rice husk-based activated carbon (RHC) was studied. The extent of adsorption was studied as a function of pH, contact time, contact temperature, adsorbate concentration and adsorbent with different pore structure. The removal of Cr(VI) by RHC was first introduced. The adsorption of two carbons activated by KOH-activation and NaOH-activation was discussed. The difference was studied through pore size distribution, pore volume and the adsorption capacity.

High surface area porous carbons prepared from hydrochars by phosphoric acid activation

In the present work, a new route for preparation of high-performance porous carbons under mild conditions was reported. The high surface area (2700 m2/g) and large pore volume (1.98 cm3/g) porous carbons were prepared from hydrochars by conventional phosphoric acid activation method. The hydrochars described here can be obtained from sulfuric acid hydrolysis of rice husk via dehydration, polymerization and carbonization. A specific capacitance of 130 F g(-1) was achieved by using the porous carbon, indicating that the porous carbon prepared by this route has good electrochemical performance. Furthermore, the localized graphitic nature of the porous carbon was proved by X-ray diffraction pattern.

A sustainable route for the preparation of activated carbon and silica from rice husk ash

An environmentally friendly and economically effective process to produce silica and activated carbon form rice husk ask simultaneously has been developed in this study. An extraction yield of silica of 72-98% was obtained and the particle size was 40-50 nm. The microstructures of the as-obtained silica powders were characterized by X-ray diffraction (XRD) and infrared spectra (IR). The surface area, iodine number and capacitance value of activated carbon could achieve 570 m(2)/g, 1708 mg/g, 180 F/g, respectively. In the whole synthetic procedure, the wastewater and the carbon dioxide were collected and reutilized. The recovery rate of sodium carbonate was achieved 92.25%. The process is inexpensive, sustainable, environmentally friendly and suitable for large-scale production.

A new route for preparation of hydrochars from rice husk

In the present work, a green and sustainable route for preparation of hydrochars from sulfuric acid hydrolysis solution of rice husk under low temperature and atmospheric pressure was described. This route was achieved with the catalysis of sulfuric acid. The sphere-like carbon materials with regular size of about 500 nm were obtained at 95 degrees C for 6h when the acid concentration was 42% and 52%. The morphology of the hydrochars changed with sulfuric acid concentration increased. The surface of the materials contained a large number of functional groups. Furthermore, the localized graphitic nature of the materials was proved by X-ray diffraction pattern. High surface area porous carbons could be prepared from the hydrochars after activation, and they exhibited good electrochemical performance.

A new method of comprehensive utilization of rice husk.

Rice husk is an abundant agricultural byproduct. The research on comprehensive utilization of rice husk to prepare xylose, activated carbon and silica was carried out. The hydrolysis conditions of xylan in rice husk to produce xylose were as follows: the concentration of H(2)SO(4) was 3.6% (wt.%), the temperature was 100°C, the ratio of rice husk mass (g) to H(2)SO(4) solution (ml) was 1:5 and the time was 3 h. The hydrolysis degree of xylan reached 95.6%. The resulting residues were used to prepare activated carbons with the BET surface area of 1763 m(2)/g when 50% H(3)PO(4) was impregnated with rice husk with the ratio of 5:1 at 500°C for 0.5 h. The produced carbons had effective adsorption capability to purify the xylose solution. Furthermore, they exhibited good electrochemical performance. After adsorption, activated carbons were calcined to produce silica with the diameter of 30 nm.

Synthesis and catalytic activity of stable hollow ZrO2–SiO2 spheres with mesopores in the shell wall

Stable hollow ZrO2–SiO2 spheres with mesopores in the shell wall have been successfully synthesized by a sol–gel process in an oil–water–oil microemulsion. The samples were characterized by transmission polarized light microscopy, SEM, TEM, and N2 adsorption–desorption isotherms. The characterization results indicate that a large number of mesopores are present in the shell wall of the calcined hollow ZrO2–SiO2 spheres, and that the diameter and shell thickness are ca. 50 and 15 µm, respectively. The hollow spheres exhibit high thermal stability and remain intact spherical structures even after calcination at 550 °C for 8 h. In the cracking reactions of cumene and 1,3,5-triisopropylbenzene the sulfated hollow ZrO2–SiO2 spheres show very high catalytic activities. Especially, the higher catalytic activity of 1,3,5-triisopropylbenzene cracking suggests the potential application in cracking of bulky molecules. A possible formation mechanism of hollow spheres of binary composite oxide is also proposed.

The preparation of tridymite crystal by chemical processing

A new method for the synthesis of tridymite is reported in this article. When amorphous SiO2 is treated with ethylene glycol for 3 h at 196°C and then filtered and washed with distilled water, tridymite is obtained. The transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the crystal materials. The EDX shows the material is pure silica and The XRD pattern shows this silica is tridymite phase. In order to study the formation process of tridymite, all sorts of reaction conditions are discussed in detail. The products obtained at different conditions are characterized by XRD techniques. Finally, a reasonable mechanism is proposed.