Comparison of Water Absorption and Mechanical Behaviors of Polypropene Composites Filled with Rice Husks Ash

Composite materials were obtained by filling polypropene with raw and thermally treated rice husks at filler contents from 1 to 20%. The physicochemical properties were determined. A slight increase was observed in the tensile strength of the composites based on white rice husk ash (WRHA) and aerosil (AR) at degree of filling up to 3%. Young's modulus increased and the elongation at break and energy to break point showed a tendency to decrease for all the composites studied. The thermodynamics and kinetics of water absorption at immersion were studied in the temperature interval 25–90°C. The values of the changes in standard free energy, ΔG°, enthalpy, ΔH°, and entropy, ΔS° of adsorption were calculated. Water absorption was found to be thermodynamically difficult due to the diffusion mechanism of the process and it was accompanied by a decrease in the values of ΔH° and ΔS° with an increase in fillers contents. The effects of the amount of absorbed water, temperature, and treatment time on the composites tensile properties were estimated.     

Preparation and characterization of ceramic composites derived from rice husk ash and polysiloxane

Ceramic matrix composites (CMCs) were prepared from a polysiloxane network filled with rice husk ash (RHA), a reactive filler. CMCs were obtained by pyrolysis at 1000 and 1600 °C of green bodies prepared from a mixture of polysiloxane network and RHA at a weight ratio of 4:1, respectively. The RHA and the CMCs were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), in addition to density and mechanical measurements. The CMCs were obtained without macroscopic defects, and their initial observed porosity was reduced by polymeric infiltrations cycles of the polymeric precursor, which improved their flexural strength and modulus up to 100%.     

Mechanical properties and thermal stability of rice husk ash filled epoxy foams

Mechanical properties and thermal stability of epoxy foams filled with white and black rice husk ash were studied. Epoxy foams were prepared from a commercial system and filled with different amounts of both the ashes (0, 6.8, 12.8, 18.0, and 22.7 wt %). The incorporation of both the ashes modified the final morphology of the foam, decreasing the average cell size and increasing the number of cells per volume unit. For all filler percentages used, the specific modulus and strength results showed that the white ash is more effective as reinforcing agent than the black ash. The initial degradation temperature was not affected by the content and type of ash used as the filler. The integral procedure decomposition temperature, weight loss, and char residue results were related to the ash type and atmosphere used in the thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Purification of FAME by rice hull ash adsorption

Rice hull ash (RHA) and silica gel were used for purification of FAME by adsorption of FFA at atmospheric conditions. Studies demonstrated that silica gel is a better adsorbent than RHA in purifying FAME. However, both adsorbents were effective in reducing FFA levels from FAME extracts. The FFA adsorption efficiency increased with high FAME concentration and high adsorbent dosage. But FAME adsorption also increased with larger doses of adsorbent. The adsorption isotherms of FFA were determined with both adsorbents. FFA adsorption displayed Freundlich-type isotherms.     

The effect of coupling agent and chemical treatment on rice husk ash‐ filled natural rubber composites

Rice husk ash was incorporated into natural rubber (NR) using a laboratory size two‐roll mill. Curing using a conventional vulcanization system (CV) was chosen, and cure studies were carried out on a Monsanto rheometer. Physical testing of the NR vulcanizates involved the determination of tensile, tear, and abrasion resistances, and hardness. Fourier transform infrared spectroscopy (FTIR) analysis was done to verify the presence of the characteristic functional groups of precipitated silica in MHA (milled husk ash) and THA (treated husk ash). The effect of the coupling agent, bis(3‐triethoxysilylpropyl)‐tetrasulfane (Si‐69), on the curing and physical properties of the vulcanizates was investigated. A chemical treatment on a rice husk ash was done, and the effects of this procedure are also reported. For comparison, two commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N774), were also used. Although the presence of the silane coupling agent had not brought the expected increase in properties, treated husk ash showed exceptional performance in terms of tensile strength and abrasion resistance of the filled vulcanizates. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1019–1027, 2000     

Competitive adsorption of lutein from soy oil onto rice hull ash

Adsorption of lutein from crude soybean oil onto acid ash prepared from rice hulls displayed Freundlich-type isotherms. Different isotherms were obtained depending on the amount of adsorbent used. Addition of isopropanol to the miscella and water deactivation of the adsorbents decreased lutein adsorption. These observations suggested competitive adsorption based on polarity. Triglycerides were adsorbed to a greater extent than lutein, probably due to their larger concentrations. These findings parallel the adsorption behavior of silicic acid.     

酸改性粉煤灰对罗丹明B的吸附研究

采用盐酸改性粉煤灰为吸附材料,以罗丹明B的模拟废水为吸附对象,研究了改性粉煤灰的投入量、吸附时间、温度及溶液pH值对吸附效果的影响。研究表明,对50 mL浓度2 mg/L的罗丹明B模拟废水,酸改性粉煤灰的最佳吸附条件是：在50℃下,加入0.09 g的粉煤灰,调节pH值为1.77,搅拌30 min。改性粉煤灰对罗丹明B吸附的脱色率可达98.19%。     

小麦秸秆对硝基苯的吸附动力学及热力学研究

采用批量吸附实验考察了小麦秸秆对硝基苯的吸附动力学及热力学行为。吸附平衡时间约为60 min,且在前20 min是吸附急剧增加的第一阶段。吸附动力学行为符合拟二级动力学方程,拟二级动力学方程拟合曲线的决定系数均大于0.99,说明拟合程度很好。Langmuir和Freundlich吸附等温线都能较好地拟合吸附过程。吸附热力学结果表明,该反应是自发、吸热并且熵变增加的过程,温度升高有利于吸附反应的进行。     

Mechanical and morphological properties of white rice husk ash filled polypropylene/ethylene‐propylene‐diene terpolymer thermoplastic elastomer composites

The performance of white rice husk ash (WRHA) as filler for polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic elastomer (TPE) composites was investigated. The composites with different filler loadings were prepared in a Brabender plasticorder internal mixer. Both unvulcanized and dynamically vulcanized composites were prepared. Mixing and vulcanization processes of the composites were monitored through the typical Brabender torque‐time curves. The mechanical properties and morphology of the composites were also studied. The Brabender torque curves revealed that the dynamic vulcanization process employed was successful and incorporation of filler has no adverse effect on the processibility of the composites. Incorporation of WRHA improves the tensile modulus and flexural modulus and lowers tensile strength, elongation at break, tear strength, and toughness of both types of composites. Dynamic vulcanization significantly enhances the mechanical and TPE properties of the composites. Dynamic mechanical analysis (DMA) study revealed the existence of two phases in both types of composites. It further shows that neither dynamic vulcanization nor filler agglomeration has played a prominent role in the compatibility of the composites. Thermogravimetric investigation shows that dynamic vulcanization or WRHA loading has not adversely affected the thermal stability of the composites. The scanning electron micrographs provide evidence for the tendency to form filler agglomerates with increasing filler loading, better filler dispersion of dynamically vulcanized composites over unvulcanized composites, and effective vulcanization of elastomer phase of the composites in the presence of filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 438–453, 2002     

对甲基苯甲酸在大孔吸附树脂上的吸附热力学及动力学研究

研究了对甲基苯甲酸在NDA-1800和JX-101大孔吸附树脂上的静态吸附热力学和动力学行为。结果表明,在283～313 K和研究的浓度范围内,两种大孔吸附树脂吸附对甲基苯甲酸的行为符合Freundlich吸附等温方程。对甲基苯甲酸在两种大孔吸附树脂上的吸附焓变△H〈0,为放热过程;自由能变△G〈0,吸附过程能自发进行;吸附熵变△S〈0,这是因为吸附质分子从水溶液中被吸附到树脂表面后,其分子运动受到了限制,使吸附熵减少。两种大孔树脂吸附对甲基苯甲酸的速率常数都比较大,且随着温度的升高而增大。吸附活化能都比较低,吸附较容易进行。     

Synthesis of ZSM-5 zeolite and silicalite from rice husk ash

Local rice husk was precleaned and properly heat treated to produce high purity amorphous SiO₂ for use in the synthesis of ZSM-5 zeolite and silicalite by hydrothermal treatment (150 °C) of the precursor gels (pH 11) under autogenous pressure in a short reaction time (4–24 h). A wide range of SiO₂/Al₂O₃ molar ratios (30–2075) and a small template content were employed to fully exploit the potential of rice husk ash (RHA). The mineralogical phases, morphology, specific surface area and pore volume of the synthesized products were investigated by XRD, FT-IR, SEM and BET analyses, respectively. Under the employed conditions, it was found that the gels with a low range of SiO₂/Al₂O₃ molar ratios (<80) produced an amorphous phase to poorly crystalline ZSM-5 zeolite; those with a medium range (80–200) favored well crystalline ZSM-5 zeolite production with a large surface area; whilst those with a high range of SiO₂/Al₂O₃ molar ratios (>200) yielded silicalite. The increase in Na₂O content, which was derived from the addition of NaAlO₂ to attain the desired SiO₂/Al₂O₃ molar ratio of the gel, did not significantly enhance the crystallization rate, crystallinity, or yield of products. On the contrary, these properties were greatly affected by the increase in the SiO₂/Al₂O₃ molar ratio.     

Thermal and rheological behavior of ultrafine fly ash filled LDPE composites

The specimens containing different volume fractions of ultrafine fly ash in LDPE were prepared with the help of two roll mixing mill and the hot‐plate compression‐molding machine. Thermal and rheological properties were evaluated using DSC and parallel‐plate rotational‐rheometer. The effect of composition variation on melt enthalpy, crystallinity, shear viscosity, shear stress and first normal stress difference was studied and reported here. The addition of ultrafine fly ash in LDPE decreased the melt enthalpy of the specimen. Slight decrease in the crystallinity of LDPE was observed on addition of fly ash. The shear stress as well as the shear viscosity both increased with the addition of ultrafine fly ash in LDPE. Two regions of shear thinning were observed at 200°C for fly ash filled LDPE. The first normal stress difference (N₁) reduced with fly ash content and with the increased temperature. The values of N₁ remained almost invariable at low shear region however a proportional increase was observed beyond the shear stress of 10 kPa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

A comparison of the properties of rice husk ash,silica, and calcium carbonate filled 75 : 25 NR/EPDM blends

The effects of incorporation of three different fillers, i.e., rice husk ash (RHA), silica, and calcium carbonate (CaCO₃), over a loading range of 0–60 phr on the curing characteristics, processability, mechanical properties, and morphology of 75 : 25 natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends were studied using a conventional vulcanization system. Filler loading and type influence the processability of the blends in which RHA and CaCO₃ offer better processing advantage over silica. The best improvement in the tensile and tear strength and abrasion resistance of the 75 : 25 NR/EPDM blends with additional fillers was achieved when filled with silica. However, RHA and CaCO₃ were better in resilience property compared to that of silica. The RHA filled blends showed higher failure properties and abrasion resistance but lower ozone resistance than that containing CaCO₃. Scanning electron micrographs revealed that the morphology of the blend filled with silica is finer and more homogenous compared to the blend filled with RHA and CaCO₃. According to these observations, RHA can be used as a cheaper filler to replace CaCO₃ in rubber blends where improved mechanical properties are not so critical. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of fineness of rice husk ash and additives on the properties of lightweight aggregate

In this paper, the preparation of lightweight aggregate (LWA) from rice husk ash (RHA) obtained from a biomass power plant was studied. As-received and ground RHAs were mixed with sodium hydroxide solution (NaOH) and cured to obtain the hardened sodium silicate paste. The samples were then crushed and heated to form LWA. The LWA was tested for acid and base solubility and for disintegration in boiling water. The results showed that ground RHA-LWA gave better performances in terms of expansion, solubility, and disintegration than the as-received RHA-LWA. However, the disintegration of LWA in boiling water was the main problem. It was found that the incorporation of 2-7% boric acid by weight of RHA alleviated this problem and no sign of disintegration was observed. The density of LWA of 0.20-0.40 g/cm³ was achieved.     

粉煤灰的活化及其对活性深蓝K-R的吸附

以粉煤灰(FA)经碱熔融和酸处理制得活性粉煤灰(AFA),并将其用于模拟废水中活性深蓝K-R的吸附,探讨了AFA的制备条件和影响吸附的因素。结果表明:在m(Na2CO3)∶m(FA)为1∶5,焙烧温度为850℃,HCl浓度为4mol/L,搅拌溶解温度为80℃的制备条件下,所制得的AFA对3500mg/L活性深蓝K-R的吸附量为335.98mg/g,活性深蓝K-R去除率达94.5%;染料起始浓度、pH、吸附时间和温度均对吸附效果产生影响;吸附动力学可用准二级吸附动力学方程进行描述(R2=1.000);等温吸附符合Langmuir方程。AFA可有效去除水溶液中高浓度的活性深蓝K-R。     

Equilibrium and kinetic modelling of the adsorption of Cd ions onto chestnut shell

A study on the removal of Cd²⁺ ions from aqueous solutions by acid formaldehyde pretreated chestnut (Castanea sativa) shell was conducted in batch conditions. The influence of different parameters: adsorption time, temperature (15, 25 and 35 °C) and initial concentration of Cd²⁺ ions (15.3, 50.5 and 87.3 mg L^− 1), on cadmium uptake was analysed. Cadmium free and cadmium loaded chestnut shell were characterized by FTIR spectroscopy, which evidenced the functional groups involved in cadmium uptake. Cadmium adsorption equilibrium could be described by the Freundlich adsorption model at all the temperatures essayed, which predicted shell heterogeneity. The Cd²⁺ adsorption process by chestnut shell followed the pseudo second order kinetic model. Cadmium sorption capacity increased with decreasing temperature at an initial concentration of 15.3 mg L^− 1 and with increasing initial cadmium concentration at a temperature of 25 °C. The second order kinetic constant, which increased with increasing temperature, was used to calculate the energy of adsorption as equal to 19.2 kJ mol^− 1.     

Kinetics and thermodynamics of the phosphine adsorption on the modified activated carbon

The kinetics and the thermodynamics of phosphine (PH₃) adsorption on the modified activated carbon have been explained for the adsorption process of PH₃. This study investigated the kinetic and thermodynamic properties of PH₃ adsorption on the activated carbon impregnated with 5% HCl solution. The thermodynamic properties including PH₃ adsorption isotherm and adsorption heat were separately investigated at 20°C, 70°C, 90°C. The results showed that the Freundlich-type isotherm equation described the isotherms well. The adsorption capacity increased with increasing temperature between 20°C and 70°C. Between 70°C and 90°C, the adsorption capacity decreased obviously with increasing temperature. The adsorption capacity reached the maximum at 70°C. By analyzing the results of the kinetics and the thermodynamics, we found that the adsorption of PH₃ was dominated by physical adsorption at the lower temperature (20°C). Then with increasing temperature, chemical adsorption gradually dominated in the adsorption process. The adsorption capacity decreased at above 70°C is due to the exothermic effects in the process of adsorption.     

粉煤灰的混酸改性及吸附性能研究

以粉煤灰为原料,用混酸酸溶制取改性粉煤灰吸附剂,并处理生活污水。结果表明：最佳酸溶时间为3h,其固体溶出率约25wt％;当改性粉煤灰的用量为100g／L时,吸附效果最佳,COD的吸附率达到75．4％,出水达到《城市污水处理厂污染物排放标准》（GB18918—2002）中的二级标准限值（100mg／L）;改性后吸附能力提高了近三倍。     

Influence of rice husk ash and wollastonite on plasticizer migration in polyvinyl chloride system

The influence of rice hull ash and wollastonite on the migration problem of plasticizer EDOS from polyvinyl chloride (PVC) has been studied. The methods of optical interferometry, IR spectroscopy, viscometry, SEM and EDX were used to study the mutual solubility and diffusion mobility in the PVC-EDOS system in the presence fillers and without them, as well as the phase structure of plasticized filled systems. It is shown that in a fully compatible PVC-EDOS system, a diffusion mixing mechanism is observed, and the interdiffusion coefficients increase from 10⁻⁸ to 10⁻⁶ (cm²/s) with increasing plasticizer concentration. The introduction of a dispersed filler somewhat reduces the interdiffusion coefficients. The sorption of the plasticizer on the surface of the dispersed filler has been established, which leads to a decrease in the migration of EDOS from the composition. It was found that the introduction of wollastonite leads to a smaller increase in viscosity and an improvement in the technological properties of the system. And the introduction of environmentally neutral rice husk ash reduces the migration of the plasticizer and improves the stability of the composition during operation, which also has a positive effect on the environmental friendliness of this system.