Mesoporous carbon adsorbents from melamine–formaldehyde resin using nanocasting technique for CO2 adsorption

Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine–formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO₂ capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO₂ adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO₂ adsorption capacity among the synthesized adsorbents. Breakthrough time and CO₂ equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent–CO₂ system was found to be reversible with stable adsorption capacity over four consecutive adsorption–desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.     

Breakthrough CO2 adsorption in bio-based activated carbons

In this work, the effects of different methods of activation on CO₂ adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO₂ activation and Potassium hydroxide (KOH) activation. CO₂ adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25–65°C and inlet CO₂ concentration range of 10–30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N₂ and CO₂ adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO₂ on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm³/g and surface area of 1400 m²/g had the highest CO₂ adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO₂ and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO₂ activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration.     

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performance

A series of MgO-based adsorbents were prepared through solution–combustion synthesis and ball-milling process.The prepared MgO-based powders were characterized using X-ray diffraction,scanning electron microscopy,N_2 physisorption measurements,and employed as potential adsorbents for CO_2 adsorption.The influence of structural and textural properties of these adsorbents over the CO_2 adsorption behaviour was also investigated.The results showed that MgO-based products prepared by solution–combustion and ball-milling processes,were highly porous,fluffy,nanocrystalline structures in nature,which are unique physico-chemical properties that significantly contribute to enhance their CO_2 adsorption.It was found that the MgO synthesized by solution combustion process,using a molar ratio of urea to magnesium nitrate(2:1),and treated by ball-milling during 2.5 hr(MgO-BM2.5h),exhibited the maximum CO_2 adsorption capacity of 1.611 mmol/g at 25℃ and 1 atm,mainly via chemisorption.The CO_2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area,total pore volume,pore size distribution and crystallinity.The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO_2adsorption–desorption times,without any significant loss of performance,that supports the potential of MgO-based adsorbent.The results confirmed that the special features of MgO prepared by solution–combustion and treated by ball-milling during 2.5 hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO_2 capture technologies.     

Optimization of CO2 adsorption capacity and cyclical adsorption/desorption on tetraethylenepentamine-supported surface-modified hydrotalcite

The objective of this research was to investigate CO_2adsorption capacity of tetraethylenepentamine-functionalized basic-modified calcined hydrotalcite(TEPA/b-c HT)sorbents at atmospheric pressure formed under varying TEPA loading levels,temperatures,sorbent weight to total gaseous flow rate(W/F)ratios and CO_2concentrations in the influent gas.The TEPA/b-c HT sorbents were characterized by means of X-ray diffraction(XRD),Fourier transform infrared spectrometry(FT–IR),thermal gravimetric analysis(TGA),Brunauer–Emmet–Teller(BET)analysis of nitrogen(N_2)adsorption/desorption and carbon–hydrogen–nitrogen(CHN)elemental analysis.Moreover,a full 2~4factorial design with three central points at a 95%confidence interval was used to screen important factor(s)on the CO_2adsorption capacity.It revealed that85.0%variation in the capacity came from the influence of four main factors and the15.0%one was from their interactions.A face-centered central composite design response surface method(FCCCD–RSM)was then employed to optimize the condition,the maximal capacity of 5.5–6.1 mmol/g was achieved when operating with a TEPA loading level of 39%–49%(W/W),temperature of 76–90°C,W/F ratio of 1.7–2.60(g·sec)/cm~3and CO_2concentration of 27%–41%(V/V).The model fitted sufficiently the experimental data with an error range of±1.5%.From cyclical adsorption/desorption and selectivity at the optimal condition,the 40%TEPA/b-c HT still expressed its effective performance after eight cycles.     

功能化凹凸棒吸附材料的制备及其对重金属废水中Pb2+的吸附行为

重金属离子废水会对人体健康和环境造成严重威胁,吸附法是去除重金属废水中重金属离子的重要方法.对凹凸棒土（ATP）接枝磁性Fe₃O₄纳米粒子,再使用3-氨基丙基三乙氧基硅烷（APTES）进行改性,制备了具有良好吸附性能的凹凸棒复合纳米材料吸附剂（ATP-Fe₃O₄-APTES）,并将其用于重金属离子废水的处理.利用FT-IR、XRD、SEM及TEM、BET吸脱附法、Zeta电位和VSM分析等方法对材料的结构和表面性质进行了分析表征.研究了所制备材料对重金属离子Pb²⁺的吸附行为,考察了溶液pH、吸附时间、吸附温度和Pb²⁺初始浓度等因素对材料吸附性能的影响作用,探讨了吸附过程的吸附动力学、吸附等温线和吸附热力学行为.结果表明,材料对Pb²⁺的最大吸附容量为129.32 mg·g^-1.吸附过程符合准二级动力学模型和Langmuir吸附等温式,表明材料对Pb²⁺的吸附是单分子层化学吸附;吸附热力学分析表明,吸附过程是一个自发的吸热过程,吸附驱动力主要来自吸附材料表面-NH₂与Pb²⁺之间的配位作用.综上,所制备功能化磁性凹凸棒吸附材料对重金属离子具有良好的吸附性能,有望用于重金属离子废水的处理.     

Efficient nitrogen doped porous carbonaceous CO2 adsorbents based on lotus leaf

In this work, the waste biomass lotus leaf was converted into N-doped porous carbonaceous CO₂ adsorbents. The synthesis process includes carbonization of lotus leaf, melamine post-treatment and KOH activation. For the resultant sorbents, high nitrogen content can be contained due to the melamine modification and advanced porous structure were formed by KOH etching. These samples were carefully characterized by different techniques and their CO₂ adsorption properties were investigated in detail. These sorbents hold good CO₂ adsorption abilities, up to 3.87 and 5.89 mmol/g at 25 and 0°C under 1 bar, respectively. By thorough investigation, the combined interplay of N content and narrow microporous volume was found to be responsible for the CO₂ uptake for this series of sorbents. Together with the high CO₂ adsorption abilities, these carbons also display excellent reversibility, high CO₂/N₂ selectivity, applicable heat of adsorption, fast CO₂ adsorption kinetics and good dynamic CO₂ adsorption capacity. This study reveals a universal method of obtaining N-doped porous carbonaceous sorbents from leaves. The low cost of raw materials accompanied by easy synthesis procedure disclose the enormous potential of leaves-based carbons in CO₂ capture as well as many other applications.     

N-doped mesoporous alumina for adsorption of carbon dioxide

N-doped mesoporous alumina has been synthesized using chitosan as the biopolymer template. The adsorbent has been thoroughly investigated for the adsorption of CO₂ from a simulated flue gas stream (15% CO₂ balanced with N₂) and compared with commercially available mesoporous alumina procured from SASOL, Germany. CO₂ adsorption was studied under different conditions of pre-treatment and adsorption temperature, inlet CO₂ concentration and in the presence of oxygen and moisture. The adsorption capacity was determined to be 29.4 mg CO₂/g of adsorbent at 55℃. This value was observed to be 4 times higher in comparison to that of commercial mesoporous alumina at a temperature of 55℃. Basicity of alumina surface coupled with the presence of nitrogen in template in synthesized sample is responsible for this enhanced CO₂ adsorption. Adsorption capacity for CO₂ was retained in the presence of oxygen; however moisture had a deteriorating effect on the adsorption capacity reducing it to nearly half the value.     

Capture of carbon dioxide from flue gas on TEPA-grafted metal-organic framework Mg2(dobdc)

Carbon dioxide （CO2） adsorption on a standard metal-organic framework Mg2（dobdc） （Mg/DOBDC or Mg-MOF-74） and a tetraethylenepentamine （TEPA） modified Mgz（dobdc） （TEPA-Mg/DOBDC） were investigated and compared. The structural information, surface chemistry and thermal behavior of the adsorbent samples were characterized by X-ray powder diffraction （XRD）, infrared spectroscopy （IR）, thermogravimetric analysis （TGA） and nitrogen adsorption-desorption isotherm analysis. CO2 adsorption capacity was measured by dynamic adsorption experiments with N2-CO2 mixed gases at 60℃. Results showed that the CO2 adsorption capacity of Mg/DOBDC was significantly improved after amine modification, with an increase from 2.67 to 6.06 mmol CO2/g adsorbent. Moreover, CO2 adsorption on the TEPA-Mg/DOBDC adsorbent was promoted by water vapor, and the adsorption capacity was enhanced to 8.31 mmol CO2/g absorbent. The adsorption capacity of the TEPA-Mg/DOBDC adsorbent dropped only 3% after 5 consecutive adsorption]desorption cycles. Therefore, this kind of adsorbent can be considered as a promising material for the capture of CO2 from flue gas.     

Removal of Cd2+ from water by Friedel’s salt (FS: 3CaO.Al2O3·CaCl2·10H2O): Sorption characteristics and mechanisms

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel’s salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.     

Enhanced CO2 adsorptive performance of PEI/SBA-15 adsorbent using phosphate ester based surfactants as additives

In this study,a series of polyetherimide/SBA-15: 2-D hexagonal P6 mm,Santa Barbara USA(PEI/SBA-15) adsorbents modified by phosphoric ester based surfactants(including tri(2-ethylhexyl)phosphate(TEP),bis(2-ethylhexyl) phosphate(BEP) and trimethyl phosphonoacetate(TMPA))were prepared for CO_2 adsorption.Experimental results indicated that the addition of TEP and BEP had positive effects on CO_2 adsorption capacity over PEI/SBA-15.In particular,the CO_2 adsorption amount could be improved by around 20% for 45PEI–5TEP/SBA-15 compared to the additive-free adsorbent.This could be attributed to the decrease of CO_2 diffusion resistance in the PEI bulk network due to the interactions between TEP and loaded PEI molecules,which was further confirmed by adsorption kinetics results.In addition,it was also found that the cyclic performance of the TEP-modified adsorbent was better than the surfactant-free one.This could be due to two main reasons,based on the results of in situ DRIFT and TG-DSC tests.First and more importantly,adsorbed CO_2 species could be desorbed more rapidly over TEP-modified adsorbent during the thermal desorption process.Furthermore,the enhanced thermal stability after TEP addition ensured lower degradation of amine groups during adsorption/desorption cycles.     

Synthesis, characterization, and photocatalytic activity of porous La–N–co-doped TiO2 nanotubes for gaseous chlorobenzene oxidation

The photocatalytic oxidation of gaseous chlorobenzene(CB) by the 365 nm-induced photocatalyst La/N–Ti O2, synthesized via a sol–gel and hydrothermal method, was evaluated. Response surface methodology(RSM) was used to model and optimize the conditions for synthesis of the photocatalyst. The optimal photocatalyst was 1.2La/0.5N–Ti O2(0.5) and the effects of La/N on crystalline structure, particle morphology, surface element content, and other structural characteristics were investigated by XRD(X-ray diffraction), TEM(Transmission Electron Microscopy), FTIR(Fourier transform infrared spectroscopy), UV–vis(Ultraviolet–visible spectroscopy), and BET(Brunauer Emmett Teller). Greater surface area and smaller particle size were produced with the co-doped Ti O2 nanotubes than with reference Ti O2. The removal of CB was effective when performed using the synthesized photocatalyst,though it was less efficient at higher initial CB concentrations. Various modified Langmuir-Hinshelwood kinetic models involving the adsorption of chlorobenzene and water on different active sites were evaluated. Fitting results suggested that competitive adsorption caused by water molecules could not be neglected, especially for environments with high relative humidity. The reaction intermediates found after GC–MS(Gas chromatography–mass spectrometry) analysis indicated that most were soluble, low-toxicity, or both. The results demonstrated that the prepared photocatalyst had high activity for VOC(volatile organic compounds) conversion and may be used as a pretreatment prior to biopurification.     

TiO2/Ag modified penta-bismuth hepta-oxide nitrate and its adsorption performance for azo dye removal

A modified hydrophilic penta-bismuth hepta-oxide nitrate (Bi₅O₇NO₃) surface was synthesized via a precipitation method using TiO₂ and Ag as modified agents. The synthesized product was characterized by different analytical techniques. The removal efficiency was evaluated using mono-and di-sulphonated azo dyes as model pollutants. Different kinetic, isotherm and diffusion models were chosen to describe the adsorption process. X-ray photoelectron spectroscopy (XPS) results revealed no noticeable differences in the chemical states of modified adsorbent when compared to pure Bi₅O₇NO₃;however, the presence of hydrophilic centres such as TiO₂ and Ag developed positively charged surface groups and improved its adsorption performance to a wide range of azo dyes. Dyes removal was found to be a function of adsorbent dosage, initial dye concentration, solution pH and temperature. The reduction of Langmuir 1,2-mixed order kinetics to the second or first-order kinetics could be successfully used to describe the adsorption of dyes onto the modified adsorbent. Mass transfer can be described by intra-particle diffusion at a certain stage, but it was not the rate limiting step that controlled the adsorption process. Homogenous behavior of adsorbent surface can be explored by applying Langmuir isotherm to fit the adsorption data.     

Adsorption of carbon dioxide on amine-modified TiO2 nanotubes

TiO2 nanotubes (TiNT) were prepared by a hydrothermal treatment and modified by three kinds of amines,namely ethylenediamine,polyetherimide and tetraethylenepentamine (TEPA),to study their CO2 adsorption properties from gas streams.The resultant samples were characterized by X-ray diffraction,transmission electron microscopy,and infrared spectroscopy,as well as low temperature N 2 adsorption.CO2 capture was investigated in a dynamic packed column at 30℃.TEPA-modified TiO2 nanotubes showed the highest adsorption capacity of 167.64 mg/g because it had the highest amino-group content among the three amines.CO2 fixation on TiNT impregnated by TEPA was investigated at 30,50,and 70℃,and the adsorption capacity increased slightly with temperature.Following the adsorption step,the sorbents were regenerated by temperature programmed desorption,and the TiNT-TEPA sample,as CO2 sorbent,was found to be readily regenerated and energy-efficient.The cycle test also revealed that the TiNT-TEPA adsorbent is fairly stable,with only a 5% drop in the adsorption capacity after 10 adsorption/desorption cycles.In addition,the CO2 adsorption behavior was investigated with the deactivation model,and which showed an excellent prediction for the TiNT-TEPA breakthrough curves.     

Synthesis, characterization and experimental investigation of Cu-BTC as CO2 adsorbent from flue gas

Porous Cu-BTC material was synthesized by the solvothermal method. Powder X-ray diffraction (PXRD) was used to test the phase purity of the synthesized material and investigate its structural stability under the influence of flue gas components. The thermal stability of the material was determined through thermal gravimetric (TG) analysis. Scanning electron microscopy (SEM) was employed to study the microstructure of the material. Cu-BTC was demonstrated not only to have high CO₂ adsorption capacity but also good selectivity of CO₂ over N₂ by means of packed bed tests. The adsorption capacity of Cu-BTC for CO₂ was about 69 mL/g at 22°C. The influence of the main flue gas components on the CO₂ capacity of the material were discussed as well.     

Probing the potential of polyester for CO2 capture

Global warming, the major environmental issue confronted by humanity today, is caused by rising level of green house gases. Carbon capture and storage technologies offer potential for tapering CO2 emission in the atmosphere. Adsorption is believed to be a promising technology for CO2 capture. For this purpose, a polyester was synthesized by polycondensation of1,3,5-benzenetricarbonyl trichloride and cyanuric acid in pyridine and dichloromethane mixture. The polymer was then characterized using FT-IR, TGA, BET surface area and pore size analysis, FESEM and CO2 adsorption measurements. The CO2 adsorption capacities of the polyester were evaluated at a pressure of 1 bar and two different temperatures（273 and 298 K）.The performance of these materials to adsorb CO2 at atmospheric pressure was measured by optimum CO2 uptake of 0.244 mmol/g at 273 K. The synthesized polyester, therefore, has the potential to be exploited as CO2 adsorbent in pre-combustion capture process.     

蚯蚓粪便生物炭对水体中雌二醇的吸附

为寻求高效、廉价的E2(雌二醇激素)吸附剂及开拓蚯蚓粪便的资源化利用途径,将蚯蚓粪便在300、500和700 ℃下热解碳化制备生物炭(分别记为BC300、BC500和BC700),对所得生物炭的基本理化性质(包括物质组成、表面官能团、孔隙结构等)进行分析,并将其用于吸附水体中E2,考察生物炭投加量、溶液pH、反应时间及初始ρ(E2)对生物炭吸附性能的影响,并探讨了吸附机理.结果表明:随热解温度的升高,生物炭的H/C(原子比)由0.13降至0.03,O/C(原子比)由0.46降至0.02,芳香性增强,极性降低,逐渐由脂肪炭结构过渡到芳香炭结构;生物炭比表面积由24.33 m2/g增至76.29 m2/g,总孔体积由0.09 cm3/g增至0.19 cm3/g.不同热解温度下制备的生物炭对E2的吸附过程均符合准二级动力学方程,拟合系数大于0.991;Langmuir和Freundlich等温吸附模型均能较好地描述蚯蚓粪便生物炭对E2的吸附过程,Langmuir理论最大吸附量表现为BC700(7.66 mg/g)>BC500(5.23 mg/g)>BC300(3.32 mg/g).随热解温度的升高,O/C和H/C降低,说明碳化程度增强,生物炭吸附E2的分配作用减弱而表面吸附作用增强.研究显示,蚯蚓粪便生物炭对E2的吸附效果随比表面积和孔体积的增加而增强.      

支化聚乙烯亚胺功能化磁性纳米吸附剂的制备及对Cu2+的吸附研究

为解决水体中重金属Cu²⁺污染,本研究首先采用水热法制备得到超顺磁四氧化三铁纳米粒子,然后使用对Cu²⁺具有强络合作用的含有丰富氨基官能团的支化聚乙烯亚胺接枝到纳米粒子表面,得到Fe₃O₄@BPEI磁性纳米吸附剂。采用红外光谱（FTIR）、X射线粉末衍射（XRD）、透射电子显微镜（TEM）等对其结构、尺寸及形貌进行表征。研究了不同吸附因素对吸附剂吸附Cu²⁺的影响,确定了最佳吸附条件,并通过吸附动力学模型和吸附等温线模型进一步探讨吸附机理。结果表明：支化聚乙烯亚胺成功接枝到四氧化三铁纳米粒子表面。最佳吸附条件为pH=6.0、吸附平衡时间为40 min、吸附剂用量为10 mg。通过实验数据拟合,Fe₃O₄@PEI吸附Cu²⁺的过程符合Langmuir等温吸附方程和拟二级动力学模型,表明吸附过程为化学吸附控制的单分子层覆盖,在303 K时,模型理论饱和吸附量为141.24 mg/g。表明支化聚乙烯亚胺修饰的磁性纳米吸附剂对Cu²⁺具有较强的吸附能力,对水体中Cu²⁺的去除具有一定的应用前景。     

Regeneration performance and carbon consumption of semi-coke and activated coke for SO2 and NO removal

To decrease the operating cost of flue gas purification technologies based on carbon-based materials, the adsorption and regeneration performance of low-price semi-coke and activated coke were compared for SO₂ and NO removal in a simulated flue gas. The functional groups of the two adsorbents before and after regeneration were characterized by a Fourier transform infrared (FTIR) spectrometer, and were quantitatively assessed using temperature programmed desorption (TPD) coupled with FTIR and acid–base titration. The results show that semi-coke had higher adsorption capacity (16.2% for SO₂ and 38.6% for NO) than activated coke because of its higher content of basic functional groups and lactones. After regeneration, the adsorption performance of semi-coke decreased because the number of active functional groups decreased and the micropores increased. Semi-coke had better regeneration performance than activated coke. Semi-coke had a larger SO₂ recovery of 7.2% and smaller carbon consumption of 12% compared to activated coke. The semi-coke carbon-based adsorbent could be regenerated at lower temperatures to depress the carbon consumption, because the SO₂ recovery was only reduced a small amount.     

Choice of precipitant and calcination temperature of precursor for synthesis of NiCo2O4 for control of CO–CH4 emissions from CNG vehicles

Compressed natural gas(CNG)is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants(Na_2CO_3,KOH and urea)for nickel cobaltite(Ni Co_2O_4)catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400°C.The catalysts were used for oxidation of a mixture of CO and CH_4(1:1).The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na_2CO_3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH_4mixture at the lowest temperature(T_(100)=350°C).Whereas,for catalyst prepared using urea,T_(100)=362°C.On the other hand the conversion of CO-CH_4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400°C.Further,the effect of higher calcination temperatures of 500 and600°C was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410°C over catalysts calcined at 500 and 600°C respectively.Thus,the best precipitant established was Na_2CO_3and the optimum calcination temperature of 400°C was found to synthesize the Ni Co_2O_4catalyst for the best performance in CO-CH_4oxidation.     

磁性高分子复合水凝胶的制备及其对水中铜离子的吸附性能

以海藻酸钠和聚乙烯醇为骨架负载磁性纳米Fe_3O_4颗粒合成了两种磁性高分子复合水凝胶材料:一种是以Ca~(2+)交联制备的磁性海藻酸钙单网络水凝胶(SAPFe),另一种是以海藻酸钙和聚乙烯醇经循环冷冻解冻制成的磁性双网络水凝胶(DAPFe).利用SEM、FTIR、BET对合成的材料进行表征,并研究了SAPFe和DAPFe对Cu~(2+)的吸附性能.结果表明,DAPFe比表面积达89.01 m~2·g~(-1),平均孔径为2.2 nm,DAPFe比SAPFe具有更低的含水率、更高的交联程度、更发达的孔隙结构和更高的比表面积.DAPFe对Cu~(2+)的最大吸附量可达207.01 mg·g~(-1),远大于SAPFe(173.01 mg·g~(-1)).SAPFe和DAPFe对Cu~(2+)的吸附等温线均符合Langmuir模型,吸附动力学符合准二级吸附动力学模型.通过分析SAPFe和DAPFe吸附Cu~(2+)前后官能团的变化,发现磁性高分子复合水凝胶具有丰富的羧基和羟基功能性官能团,并通过与Cu~(2+)产生螯合作用实现去除.