Sorption of SO(2) and NO from simulated flue gas over rice husk ash (RHA)/CaO/CeO(2) sorbent: evaluation of deactivation kinetic parameters

In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO(2) sorbent for SO(2) and NO sorptions were investigated in a laboratory-scale stainless steel fixed-bed reactor. Data experiments were obtained from our previous results and additional independent experiments were carried out at different conditions. The initial sorption rate constant (k(0)) and deactivation rate constant (k(d)) for SO(2)/NO sorptions were obtained from the nonlinear regression analysis of the experimental breakthrough data using deactivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 °C. The activation energy and frequency factor for the SO(2) sorption were found to be 18.0 kJ/mol and 7.37 × 10(5)cm(3)/(g min), respectively. Whereas the activation energy and frequency factor for the NO sorption, were estimated to be 5.64 kJ/mol and 2.19 × 10(4)cm(3)/(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO(2)/NO sorptions.     

Capture of gaseous elemental mercury from flue gas using a magnetic and sulfur poisoning resistant sorbent Mn/γ-Fe2O3 at lower temperatures

A series of Mn/γ-Fe(2)O(3) were synthesized to capture elemental mercury from the flue gas. Mn(4+) cations and cation vacancies on the surface played important roles on elemental mercury capture by Mn/γ-Fe(2)O(3). Furthermore, the reaction route of elemental mercury oxidization was dependent on the ratio of Mn(4+) cations to cation vacancies. As a result, the capacities of 15%-Mn/γ-Fe(2)O(3)-250 for elemental mercury capture were generally higher than those of 30%-Mn/γ-Fe(2)O(3)-400. SO(2) mainly reacted with ≡Fe(III)-OH and only a small amount of ≡Mn(4+) reacted with SO(2), so the presence of a high concentration of SO(2) resulted in an insignificant effect on elemental mercury capture by 15%-Mn/γ-Fe(2)O(3)-250 at lower temperatures. The capacities of 15%-Mn/γ-Fe(2)O(3)-250 for elemental mercury capture in the presence of 2.8 g N m(-3) of SO(2) were more than 2.2 mg g(-1) at <200°C. Meanwhile, 15%-Mn/γ-Fe(2)O(3)-250 can be separated from the fly ash using magnetic separation, leaving the fly ash essentially free of sorbent and adsorbed HgO. Therefore, 15% Mn/γ-Fe(2)O(3)-250 may be a promising sorbent for elemental mercury capture.     

Lightweight geopolymer made of highly porous siliceous materials with various Na2O/Al2O3 and SiO2/Al2O3 ratios

The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO₂/Al₂O₃ ratios of 13.0-33.5 and Na₂O/Al₂O₃ ratios of 0.66-3.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties and microstructures of the geopolymer pastes were investigated. The results indicated that the optimum calcination temperature of DE was 800 °C. Increasing fineness of DE and starting Na₂O/Al₂O₃ ratio resulted in an increase in compressive strength of geopolymer paste. Geopolymer pastes activated with NaOH gave higher compressive strengths than those with KOH. The optimum curing temperature and time were 75 °C and 5 days. The lightweight geopolymer material with mean bulk density of 0.88 g/cm³ and compressive strength of 15 kg/cm² was obtained. Incorporation of 40% RHA to increase starting SiO₂/Al₂O₃ and Na₂O/Al₂O₃ ratios to 22.5 and 1.7 and enhanced the compressive strength of geopolymer paste to 24 kg/cm² with only a marginal increase of bulk density to 1.01 g/cm³. However, the geopolymer materials with high Na₂O/Al₂O₃ (>1.5) were not stable in water submersion.     

Pyridine sorption from aqueous solution by rice husk ash (RHA) and granular activated carbon (GAC): parametric, kinetic, equilibrium and thermodynamic aspects

The present study deals with the adsorption of pyridine (Py) from synthetic aqueous solutions by rice husk ash (RHA) and commercial grade granular activated carbon (GAC) and reports on the kinetic, equilibrium and thermodynamic aspects of Py sorption. Batch sorption studies were carried out to evaluate the effect of various parameters, such as adsorbent dose (m), initial pH (pH0), contact time (t), initial concentration (C0) and temperature (T) on the removal of Py. The maximum removal of Py is found to be approximately 96% and approximately 97% at lower concentrations (<50 mg dm(-3)) and approximately 79.5% and approximately 84% at higher concentrations (600 mg dm(-3)) using 50 kg m(-3) and 30 kg m(-3) of RHA and GAC dosage, respectively, at 30+/-1 degrees C. Adsorption of Py is found to be endothermic in nature and the equilibrium data can be adequately represented by Toth and Redlich-Peterson isotherm equations. Py can be recovered from the spent adsorbents by using acidic water and 0.1 N H2SO4. The overall adsorption of Py on RHA and GAC is found to be in the order of GAC>RHA. Comparative assessment of adsorbents used by various investigators available in literature showed the effectiveness of BFA and RHA over other adsorbents. Spent RHA can simply be filtered, dried and used in the boiler furnaces/incinerators. Thus, its heating value can be recovered.     

High temperature capture of CO2 on lithium-based sorbents from rice husk ash

Highly efficient Li(4)SiO(4) (lithium orthosilicate)-based sorbents for CO(2) capture at high temperature, was developed using waste materials (rice husk ash). Two treated rice husk ash (RHA) samples (RHA1 and RHA2) were prepared and calcined at 800°C in the presence of Li(2)CO(3). Pure Li(4)SiO(4) and RHA-based sorbents were characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. CO(2) sorption was tested through 15 carbonation/calcination cycles in a fixed bed reactor. The metals of RHA were doped with Li(4)SiO(4) resulting to inhibited growth of the particles and increased pore volume and surface area. Thermal analyses indicated a much better CO(2) absorption in Li(4)SiO(4)-based sorbent prepared from RHA1 (higher metal content sample) because the activation energies for the chemisorption process and diffusion process were smaller than that of pure Li(4)SiO(4). RHA1-based sorbent also maintained higher capacities during the multiple cycles.     

Utilization of fermentation waste (Corynebacterium glutamicum) for biosorption of Reactive Black 5 from aqueous solution

A fermentation waste, Corynebacterium glutamicum, was successfully employed as a biosorbent for Reactive Black 5 (RB5) from aqueous solution. This paper initially studied the effect of pretreatment on the biosorption capacity of C. glutamicum toward RB5, using several chemical agents, such as HCl, H(2)SO(4), HNO(3), NaOH, Na(2)CO(3), CaCl(2) and NaCl. Among these reagents, 0.1M HNO(3) gave the maximum enhancement of the RB5 uptake, exhibiting 195mg/g at pH 1 with an initial RB5 concentration of 500mg/l. The solution pH and temperature were found to affect the biosorption capacity, and the biosorption isotherms derived at different pHs and temperatures revealed that a low pH (pH 1) and high temperature (35 degrees C) favored biosorption. The biosorption isotherm was well represented using three-parameter models (Redlich-Peterson and Sips) compared to two-parameter models (Langmuir and Freundlich models). As a result, high correlation coefficients and low average percentage error values were observed for three-parameter models. A maximum RB5 uptake of 419mg/g was obtained at pH 1 and a temperature of 35 degrees C, according to the Langmuir model. The kinetics of the biosorption process with different initial concentrations (500-2000mg/l) was also monitored, and the data were analyzed using pseudo-first and pseudo-second order models, with the latter describing the data well. Various thermodynamic parameters, such as DeltaG degrees, DeltaH degrees and DeltaS degrees, were calculated, indicating that the present system was a spontaneous and endothermic process. The use of a 0.1M NaOH solution successfully desorbed almost all the dye molecules from dye-loaded C. glutamicum biomass at different solid-to-liquid ratios examined.     

Rice husk ash as both pozzolanic admixture and internal curing agent in ultra-high performance concrete

The present study investigated the effects of mesoporous amorphous rice husk ash (RHA) on compressive strength, portlandite content, autogenous shrinkage and internal relative humidity (RH) of ultra-high performance concretes (UHPCs) with and without ground granulated blast-furnace slag (GGBS) under different treatments. The results were compared with those of UHPCs containing silica fume (SF). Because of the mesoporous structure, RHA can absorb an amount of aqueous phase to decrease the free water content and to supply thereafter water for further hydrations of cementitious materials. Hence, compressive strength of RHA-blended samples is enhanced. The highly water absorbing RHA delays and slows down the decrease in the internal RH (self-desiccation) of UHPCs, and hence strongly mitigates autogenous shrinkage of UHPCs compared to SF. The combination of GGBS and RHA or SF improves the properties of UHPC. These results suggest that RHA acts as both highly pozzolanic admixture and internal curing agent in UHPC.     

Influence of 15 and 80 nano-SiO2 particles addition on mechanical and physical properties of ternary blended concrete incorporating rice husk ash

This study demonstrates the effects of SiO₂ nanoparticles as additives with two different sizes of 15 and 80?nm on compressive strength and porosity of rice husk ash (RHA) blended concrete. Up to 20% of ordinary Portland cement (OPC) was replaced by RHA with average particle size of 5 micron. Also, SiO₂ nanoparticles were added to the above mixture at four different weight percentages of 0.5, 1.0, 1.5 and 2.0 and cured in lime solution. The results indicated that compressive strength of Portland cement–nano SiO₂–rice husk ash (PC–NS–RHA) ternary blended concrete was considerably increased. Moreover, the total amount of porosity decreased to a minimum with respect to the control concrete. This improvement was observed at all the curing ages and replacement levels, but there was a gain in the optimal point with 20% of RHA plus 2% of 80?nm SiO₂ particles at 90 days of curing.     

Microwave remediation of soil contaminated with hexachlorobenzene

This study describes the remediation of hexachlorobenzene (HCB) contaminated soils by microwave (MW) radiation in a sealed vial. When powdered MnO2 was used as MW absorber, a complete removal of HCB was obtained with 10 min MW by the addition of H2SO4 (50%). But no significant decomposition was observed by the addition of NaOH (10 mol/L) or H2O in the same conditions. In contrast, when powdered Fe was used instead of MnO2, the difference of HCB removals between H2SO4 and NaOH were not obvious. It is noteworthy that more than 95% removal was achieved in any case when the sole aqueous solution of H2SO4, NaOH, H2O or Na2SO4 was added without MnO2 or Fe. As a result, it is possible that water itself contained in the damp soil may act as MW absorber and remediate the contaminated soil without addition of any other MW absorbers. Gas chromatograph/mass spectrum (GC/MS) analysis detected no intermediates in all the processes. The decomposition mechanism of HCB by MW radiation was suggested as the binding of HCB and soil. Whatever fragments formed from HCB by heat were tightly bound to the soil, making it impossible to extract them out. In the end, treatment of practical HCB contaminated soil by MW reduced HCB from 55.8 mg/kg to 0.91 mg/kg.     

醇胺改性氧化石墨烯的制备及二氧化硫吸附性能

固体吸附剂在烟道气脱硫方面具有很大的潜力。以氧化石墨烯(GO)为基底材料,通过乙醇胺(MEA)、二乙醇胺(DEA)和三乙醇胺(TEA)对氧化石墨烯进行改性,得到了GO-MEA、GO-DEA和GO-TEA三种用于吸附SO_2的固体吸附剂。利用扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、能量色散X射线能谱(EDS)、元素分析(EA)等手段对其进行表征,并采用称重法测定了醇胺改性氧化石墨烯对SO_2气体的吸附性能。结果表明,醇胺改性氧化石墨烯对SO_2的吸附性能相比未改性氧化石墨烯有较大提高,其中GO-DEA的SO_2吸附性能最好,15h后平衡吸附量达到188.5mg/g。在130℃、真空条件下进行解吸,经过五次循环之后吸附量依然保持在165.3mg/g。     

Biosorption of Cr(III) ions by eggshells

The paper presents results of studies carried out on sorption of Cr(III) ions from aqueous solutions by eggshells as a low-cost sorbent. It was found that crushed eggshells possess relatively high sorption capacity, when comparing with other sorbents, that was evaluated as 21-160 mg/g. The effect of process parameters: pH, temperature, initial concentration of Cr(III) ions on the process kinetics was studied. It was found that the equilibrium of the process was reached after 60 min. Also equilibrium studies were performed: the effect of sorbent concentration and equilibrium Cr(III) concentration was studied. The maximum experimentally determined sorption capacity 160 mg/g was obtained at low sorbent concentration at 20 degrees C and pH 5. It was found that sorption capacity increased with the increase of Cr(III) concentration, temperature and sorbent concentration. Mathematical models describing kinetics and equilibrium of sorption were proposed. The process kinetics was described with pseudo-second-order pattern and equilibrium was described with Langmuir-type equation, and the influence of sorbate concentration, with an empirical dependence. The models were positively verified. Eggshells were able to remove the concentration of Cr(III) ions below the acceptable level, i.e. at 40 degrees C, at the initial concentration of metal ions 100 mg/kg, at sorbent concentration 15 g/l.     

Physical and chemical modification of distillery sludge for Pb(II) biosorption

The waste distillery sludge from sugar-cane industry was pretreated physically (boiled, heated and autoclaved) as well as chemically (HCl, H(2)SO(4), H(3)PO(4), NaOH, Ca(OH)(2), Al(OH)(3), C(6)H(6), HCHO, CH(3)OH and C1(2)H(25)OSO(3)Na (sodium dodecyl sulphate (SDS)) for assessing the comparative sorption capacity of untreated and modified distillery sludge for Pb(II) biosorption from aqueous solutions. Experiments were conducted in shake flasks on a batch basis to access the effect of different experimental parameters such as pH, biosorbent dosage, biosorbent size, initial Pb(II) concentration and contact time. The uptake capacity 'q' (mg/g) of untreated and pretreated distillery sludge was in following order: NaOH (51.29+/-1.21)>HCl (49.82+/-1.22)>HCHO (49.56+/-1.14)>H(2)SO(4) (47.71+/-1.20)>HgCl(2) (45.32+/-1.06)>Ca(OH)(2) (44.01+/-1.18)>MeOH (43.73+/-1.23)>C(6)H(6) (42.72+/-1.19)>H(3)PO(4) (42.01+/-1.17)>SDS (40.87+/-1.27)>autoclaved (40.23+/-1.24)>Boiled (39.95+/-1.19)>heated (38.87+/-1.32)>Al (OH)(3) (38.30+/-1.14)>untreated (37.76+/-1.21). In further parameter studies, the optimized biosorbent size was 0.250 mm at pH 5 and best dose was 0.05 g of biosorbent. The applicability of the Langmuir and Freundlich models for sorption process was tested and best fitted model was Langmuir with the coefficient of determination (R(2)) value, 0.97, the process followed second order kinetic mechanism.     

Multi-functional sorbents for the simultaneous removal of sulfur and lead compounds from hot flue gases

A multi-functional sorbent is developed for the simultaneous removal of PbCl(2) vapor and sulfur dioxide from the combustion gases. The sorbent is tested in a bench-scale reactor at the temperature of 700 degrees C, using simulated flue gas (SFG) containing controlled amounts of PbCl(2) and SO(2) compounds. The removal characteristics of PbCl(2) and SO(2), individually and in combination, are investigated. The results show that the mechanism of capture by the sorbent is not a simple physical adsorption process but seems to involve a chemical reaction between the Ca-based sorbent and the contaminants from the simulated flue gas. The porous product layer in the case of individual SO(2) sorption is in a molten state at the reaction temperature. In contrast, the combined sorption of lead and sulfur compounds generates a flower-shaped polycrystalline product layer.     

Synthesis of a quaternary amine anion exchange resin and study [of] its adsorption behaviour for chromate oxyanions

Glycidyl methacrylate/N,N'-methylene bis-acrylamide (GMA/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2-10 indicating the strong basic nature of the quaternary amine sites. The effect of pH on the recovery of chromate by RPA and RQA was examined. The results indicated that RQA is an efficient sorbent for chromate from both acidic and basic media. The repeated use of RQA was tested through stripping the adsorbed chromate using a mixture of 0.05 NaOH and 2 M NaCl in the case of the uptake from acidic media and using 2 M NaCl solution in the case of alkaline solutions.     

Utilization of agricultural waste (rice husk) in synthesis of TS-1 zeolite as a support for NiMo nanocatalyst employed in hydrodesulfurization of heavy oil

Agricultural waste, rice husk (RH) was treated to obtain rice husk ash (RHA) and utilized as silica precursor in hydrothermal synthesis of TS-1 zeolite. Results of characterization analyses, XRD, FTIR, FESEM and N₂ adsorption-desorption, confirmed that TS-1 zeolite was properly synthesized from RHA. Synthesis of TS-1 was also carried out with TEOS for comparison of textural properties. Prepared TS-1 zeolite with RHA was used as support for HDS catalyst preparation. Molybdenum active phase and nickel promoter were loaded via three different methods, impregnation, precipitation and solution combustion, to obtain NiMo/TS-1 hydrodesulfurization catalyst. EDX dot-mapping and H₂-TPR analyses indicated on better preparation of NiMo/TS-1 catalyst by solution combustion method, in terms of distribution and amount of successfully loaded metal over the support surface. Hydrodesulfurization (HDS) activity of synthesized samples was examined in hydrodesulfurization of heavy oil feed, carried out in a continuous fixed bed reactor apparatus. Performance test revealed that NiMo/TS-1 catalyst synthesized by solution combustion method eliminated 63.5 % of the feed sulfur content (4000 ppm); a superior hydrodesulfurziation activity, compared to the samples prepared via impregnation and precipitation methods with 40.8 % and 50.2 % sulfur removal, respectively. Amount of sulfur present in the feed and treated product was determined with GC-MS analysis.     

A pilot plant technical assessment of an advanced in-duct desulphurisation process

In-duct sorbent injection (DSI) is a well-known, low-cost desulphurisation technology handicapped by its moderate SO(2) removal capacity. Fortunately, there are some technical options for increasing the desulphurisation efficiency without eliminating its inherent advantages. In this experimental study, several improvement design options like the recirculation of reactivated sorbent, the pre-collection of the fly ash and the use of seawater for humidification have been analysed using an extensive parametric testing programme. The effect of the main operating variables directly related to the desulphurisation efficiency has been also tested following a fractional factorial design. These variables were the Ca/S ratio, the approach to the adiabatic saturation temperature and the recirculation ratio of the partially converted sorbent. Other important questions like the use of a high-BET-area lime and the impact of the DSI process on an ESP have been also included in this experimental assessment.More than 50 experimental tests were carried out in a 3-MWe equivalent pilot plant to assess the different improvement options for in-duct sorbent injection. The results of this study allow us to extract practical conclusions about the devices, equipment and operating conditions as a function of the target SO(2) efficiency, and even enable us to provide an economic assessment. Using the proposed improvement options to process a flue gas with 400-1000ppm of SO(2) concentration, a 90% sulphur removal with a lime utilisation of 45% was achieved.     

碳纳米管改性对环氧树脂复合材料热学和电学性能的影响

分别采用混酸(浓H2SO4和浓HNOs)、浓HNOs、浓NaOH及浓H2SO4/H2O2对碳纳米管(CNTs)在室温下进行表面处理,通过FTIR、SEM、DSC和TGA研究了各改性方法对CNTs/环氧树脂(EP)复合材料热性能和电性能的影响.结果表明,混酸处理使CNTs在EP中的分散性、EP的玻璃化温度和热分解温度都显著提高,其它3种方法也有这种作用,相比较而言,H2SO4/H2O2和HNO3的改性作用稍差,而NaOH的最差.4种处理方法都使复合材料的导电性能、介电常数以及介电损耗显著下降,其中混酸处理使上述性能下降的程度最高,其次为H2SO4/H2O2处理,NaOH处理和HNO3处理对电性能影响较小.     

用稻壳灰为硅源合成有序介孔二氧化硅材料的研究

用稻壳灰为硅源,用十六烷基三甲基溴化铵作为模板剂,在酸性或碱性条件下均成功地合成了有序介孔SiO2材料MCM-41.利用XRD、N2吸附曲线、SEM、TEM等测试方法分别对稻壳灰及介孔SiO2样品进行了表征.结果表明,稻壳灰为非晶体,呈粒状的多孔结构,其比表面积为250m2/g;在酸性条件下合成的MCM-41具有周期性规则排列的介孔结构,最可几孔径为2.4nm,比表面积为1100m2/g.     

Utilization of a low cost agro-residue for production of coagulant aids and their applications

Different samples of rice husk ash (RHA) and sodium silicate were prepared and characterized using FTIR, NFTIR and XRD. The selected sample of RHA was obtained by calcination of untreated rice husk (RH) in a semi-closed system at 650°C. Four novel polyinorganic coagulants were also prepared, namely, poly aluminum chloride silicate, poly hydroxy aluminum sulphate silicate, poly ferric chloride silicate and poly ferric aluminum chloride silicate. Applications were carried out for the removal of some pollutants from ground, sewage and industrial waste waters. It was found that the maximum percentages removal of Fe(2+) and Mn(2+) ions in ground water reached 99 and 97%, respectively, the maximum percentage removal of, Pb(2+) ion in industrial waste water reached 97%. In addition, the maximum percentages removal of COD, BOD and TSS in sewage waste water reached 90, 92, and 93%, respectively.     

Adsorption of phthalic acid and its esters onto high-area activated carbon-cloth studied by in situ UV-spectroscopy

The adsorption behavior of phthalic acid and its three esters dimethyl phthalate, diethyl phthalate and diallyl phthalate onto high-area activated carbon-cloth was studied by in situ UV-spectroscopic technique. The effect of ionization of phthalic acid on its adsorption was examined by carrying out the adsorption process in three media; water, 1 M H(2)SO(4) and 0.005 M NaOH. Maximum adsorption was observed in 1 M H(2)SO(4) and almost no adsorption in 0.005 M NaOH. These results were discussed in terms of electrostatic and dispersion interactions between the adsorbate species and the carbon-cloth surface taking the point of zero charge (pH(pzc)) of the carbon-cloth into account. The adsorption process for the phthalate species studied was found to follow the first-order rate law, and the rate constants were determined. The isotherm data for the adsorption of phthalic acid and its esters were derived experimentally and fitted to Langmuir and Freundlich isotherm equations. Both equations were found to represent the experimental isotherm data almost equally well.