Silica materials recovered from photonic industrial waste powder: its extraction, modification, characterization and application

This study explored the possibility of recovering waste powder from photonic industry into two useful resources, sodium fluoride (NaF) and the silica precursor solution. An alkali fusion process was utilized to effectively separate silicate supernatant and the sediment. The obtained sediment contains purified NaF (>90%), which provides further reuse possibility since NaF is widely applied in chemical industry. The supernatant is a valuable silicate source for synthesizing mesoporous silica material such as MCM-41. The MCM-41 produced from the photonic waste powder (PWP), namely MCM-41(PWP), possessed high specific surface areas (1082 m²/g), narrow pore size distributions (2.95 nm) and large pore volumes (0.99 cm³/g). The amine-modified MCM-41(PWP) was further applied as an adsorbent for the capture of CO₂ greenhouse gas. Breakthrough experiments demonstrated that the tetraethylenepentamine (TEPA) functionalized MCM-41(PWP) exhibited an adsorption capacity (82 mg CO₂/g adsorbent) of only slightly less than that of the TEPA/MCM-41 manufactured from pure chemical (97 mg CO₂/g adsorbent), and its capacity is higher than that of TEPA/ZSM-5 zeolite (43 mg CO₂/g adsorbent). The results revealed both the high potential of resource recovery from the photonic solid waste and the cost-effective application of waste-derived mesoporous adsorbent for environmental protection.     

Functionalization of mesoporous MCM-41 for the delivery of curcumin as an anti-inflammatory therapy

In this study, mesoporous silica nanoparticles (MSNs) composed of MCM-41 were synthesized and modified with amine groups (i.e., NH₂) to form NH_2/MCM-41, which was loaded with curcumin (CUR) to form CUR@NH₂/MCM-41 to create an efficient carriers in drug delivery systems (DDSs). The three samples (i.e., pure MCM-41, NH₂/MCM-41, and CUR@NH₂/MCM-41) were characterized using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transition electron microscopy (TEM), and a thermogravimetric analyzer (TGA). The study investigated the effect of the carrier dose, CUR concentration, pH, and contact time on the drug loading efficiency (DLE%) by adsorption. The best DLE% for MCM-41 and NH₂/MCM-41 was found to be 15.78 and 80%, respectively. This data demonstrated that the Langmuir isotherm had a greater correlation coefficient (R²) of 0.9840 for MCM-41 and 0.9666 for NH₂/MCM-41 than the Freundlich and Temkin isotherm models. A pseudo-second-order kinetic model seems to fit well with R² = 0.9741 for MCM-41 and R² = 0.9977 for NH₂/MCM-41. A phosphate buffer solution (PBS) with a pH of 7.4 was utilized to study CUR release behavior. As a result, the full release after 72 h was found to have a maximum of 74.1% and 29.95% for pure MCM-41 and NH₂/MCM-41, respectively. The first-order, Weibull, Hixson-Crowell, Korsmeyer-Peppas, and Higuchi kinetic release models were applied to releasing CUR from CUR@MCM-41 and CUR@NH₂/MCM-41. The Weibull kinetic model fit well, with R² = 0.944 and 0.96912 for pure MCM-41 and NH₂/MCM-41, respectively.     

Relation between some two- and three-parameter isotherm models for the sorption of methylene blue onto lemon peel

Equilibrium uptake of methylne blue onto lemon peel was fitted to the 2 two-parameter isotherm models namely Freundlich and Langmuir and 3 six-parameter isotherm models namely Redlich-Peterson, Toth, Radke-Prausnitz, Fritz-Schluender, Vieth-Sladek and Sips isotherms by non-linear method. A comparison between two-parameter and three-parameter isotherms was reported. The best fitting isotherm was the Sips isotherm followed by Langmuir isotherm and Redlich-Peterson isotherm equation. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity. Radke-Prausnitz, Toth, Vieth-Sladek isotherm were the same when the Toth isotherm constant, n(T) and the Radke-Prausnitz isotherm, m(RP) are equal to unity and when the Vieth-Sladek isotherm constant, K(VS) equals zero. The sorption capacity of lemon peel for methylene blue uptake was found to be 29 mg/g.     

Modeling and evaluation of chromium remediation from water using low cost bio-char, a green adsorbent

Oak wood and oak bark chars were obtained from fast pyrolysis in an auger reactor at 400-450 °C. These chars were characterized and utilized for Cr(VI) remediation from water. Batch sorption studies were performed at different temperatures, pH values and solid to liquid ratios. Maximum chromium was removed at pH 2.0. A kinetic study yielded an optimum equilibrium time of 48 h with an adsorbent dose of 10 g/L. Sorption studies were conducted over a concentration range of 1-100mg/L. Cr(VI) removal increased with an increase in temperature (Q(Oak wood)(°): 25 °C = 3.03 mg/g; 35 °C = 4.08 mg/g; 45 °C = 4.93 mg/g and Q(Oakbark)(°): 25 °C = 4.62 mg/g; 35 °C = 7.43 mg/g; 45 °C = 7.51 mg/g). More chromium was removed with oak bark than oak wood. The char performances were evaluated using the Freundlich, Langmuir, Redlich-Peterson, Toth, Radke and Sips adsorption isotherm models. The Sips adsorption isotherm model best fits the experimental data [high regression (R(2)) coefficients]. The overall kinetic data was satisfactorily explained by a pseudo second order rate expression. Water penetrated into the char walls exposing Cr(VI) to additional adsorption sites that were not on the surfaces of dry char pores. It is remarkable that oak chars (S(BET): 1-3m(2)g(-1)) can remove similar amounts of Cr(VI) as activated carbon (S(BET): ～ 1000 m(2)g(-1)). Thus, byproduct chars from bio-oil production might be used as inexpensive adsorbents for water purification. Char samples were successfully used for chromium remediation from contaminated surface water with dissolved interfering ions.     

Preparation and CO_2 adsorption properties of porous carbon by hydrothermal carbonization of tree leaves

Porous carbon materials were prepared by hydrothermal carbonization(HTC) and KOH activation of camphor leaves and camellia leaves. The morphology, pore structure, chemical properties and CO_2 capture ability of the porous carbon prepared from the two leaves were compared. The effect of HTC temperature on the structure and CO_2 adsorption properties was especially investigated. It was found that HTC temperature had a major effect on the structure of the product and the ability to capture CO_2. The porous carbon materials prepared from camellia leaves at the HTC temperature of 240℃ had the highest proportion of microporous structure, the largest specific surface area(up to 1823.77 m~2/g) and the maximum CO_2 adsorption capacity of 8.30 mmol/g at 25℃ under 0.4 MPa. For all prepared porous carbons, simulation results of isothermal adsorption model showed that Langmuir isotherm model described the adsorption equilibrium data better than Freundlich isotherm model. For porous carbons prepared from camphor leaves, pseudo-first order kinetic model was well fitted with the experimental data. However,for porous carbons prepared from camellia leaves, both pseudo-first and pseudo-second order kinetics model adsorption behaviors were present. The porous carbon materials prepared from tree leaves provided a feasible option for CO_2 capture with low cost, environmental friendship and high capture capability.     

Synthesis,characterization and photocatalytic behavior of TiO2–SiO2 mesoporous composites in hydrogen generation from water splitting

TiO₂–SiO₂ mesoporous composite photocatalysts with different proportions (in wt%) of TiO₂ and SiO₂ (TiO₂–SiO₂ = 20:80, 40:60, 60:40, 80:20 and 100:0) were prepared by loading TiO₂ on as-synthesized Si–MCM-41 using sol–gel method. The physicochemical properties of composites were investigated by powder X-ray diffraction, N₂ adsorption–desorption measurements, transmission electron microscopy and UV–Vis diffuse reflectance spectroscopy. It is revealed that the titanium species are dispersed as TiO₂ having interaction with the surface of the support. Even at high TiO₂ loading, the mesostructural feature of MCM-41 was found to be intact without pore blockages. The change in morphology of TiO₂ particle was observed with increase in TiO₂ loading which may be due to different environment for the growth of TiO₂. The photocatalytic evaluation of composites was carried out in production of hydrogen by water splitting. Among the prepared samples, mesoporous composite containing 60 % TiO₂ (MTi60) has shown the best results (0.08805 mmol of H₂/h/g of TiO₂) compared to other composite photocatalysts. The catalytic performance of this sample was further enhanced (~8 times) after loading 1 % Pt in water splitting (0.70161 mmol of H₂/h/g of TiO₂). 1 % Pt loaded on pure TiO₂ (MTi100) showed hydrogen evolution of the magnitude 0.26 mmol of H₂/h/g of TiO₂. TiO₂–SiO₂ mesoporous composite photocatalyst showed much higher activity (~1.9 times) than amorphous silica-embedded titania catalyst having same composition.     

Adsorption of Thorium from Aqueous Solution using Nanoporous Adsorbents: Effect of Contact Time,pH, Initial Concentration,and Temperature

Nanoporous silicates MCM-41 have been prepared using different surfactants such as cetyltrimethylammonium bromide (C₁₆TAB) and dodecyltrimethylammonium bromide (C₁₂TAB) as template. The adsorbents are characterized using powder x-ray diffraction, nitrogen adsorption-desorption isotherm data, scanning electron microscopy, and transmission electron microscopy. The thorium sorption was studied as a function of shaking time, pH, initial concentration, and temperature. The sorption of thorium at the determined optimum conditions follows Langmuir and Freundlich isotherms. The results show that the nanoporous MCM-41 synthesized by C₁₂TAB has more adsorption capacity than the MCM-41 synthesized by C₁₆TAB (77.6 µmol · g^?1 vs. 52.1 µmol · g^?1) at 25°C. Th(IV) adsorption onto nanoporous adsorbents was very fast process and therefore, this adsorbent is suitable for column separation. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were found to be 47.76 KJ · mol^?1, 196.21 J · mol^?1 · K^?1, and 19.00 KJ · mol^?1, respectively (at 298 K). The positive value ΔH° suggested the endothermic nature of adsorption and negative ΔG° indicates the feasibility and spontaneity of the adsorption process.     

The investigation of MCM-48-type and MCM-41-type mesoporous silica as oral solid dispersion carriers for water insoluble cilostazol

Objective: To explore the suitable application of MCM-41 (Mobil Composition of Matter number forty-one)-type and MCM-48-type mesoporous silica in the oral water insoluble drug delivery system.

Methods: Cilostazol (CLT) as a model drug was loaded into synthesized MCM-48 (Mobil Composition of Matter number forty-eight) and commercial MCM-41 by three common methods. The obtained MCM-41, MCM-48 and CLT-loaded samples were characterized by means of nitrogen adsorption, thermogravimetric analysis, ultraviolet-visible spectrophotometry, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and powder X-ray diffractometer.

Results: It was found that solvent evaporation method was preferred according to the drug loading efficiency and the maximum percent cumulative drug dissolution. MCM-48 with 3D cubic pore structure and MCM-41 with 2D long tubular structure are nearly spherical particles in 300–500?nm. Nevertheless, the silica carriers with similar large specific surface areas and concentrating pore size distributions (978.66?m²/g, 3.8?nm for MCM-41 and 1108.04?m²/g, 3.6?nm for MCM-48) exhibited different adsorption behaviors for CLT. The maximum percent cumulative drug release of the two CLT/silica solid dispersion (CLT-MCM-48 and CLT-MCM-41) was 63.41% and 85.78% within 60?min, respectively; while in the subsequent 12?h release experiment, almost 100% cumulative drug release were both obtained. In the pharmacokinetics aspect, the maximum plasma concentrations of CLT-MCM-48 reached 3.63?mg/L by 0.92?h. The AUC_0–∞ values of the CLT-MCM-41 and CLT-MCM-48 were 1.14-fold and 1.73-fold, respectively, compared with the commercial preparation.

Conclusion: Our findings suggest that MCM-41-type and MCM-48-type mesoporous silica have great promise as solid dispersion carriers for sustained and immediate release separately.     

O2, CH4 and CO2 gas retentions by acid smectites before and after thermal treatment

Acid smectites in natural condition and after thermal treatment up to 900 °C were studied for their O₂, CH₄ and CO₂ gas retentions at 25 °C and 1 kg/cm². Two smectites, one dioctahedral and one trioctahedral, were treated with 5.0 N sulphuric acid solution for 15 and 60 min. The gas adsorptions by the smectites increased after acid treatments. The O₂ (0.014–0.030 mmol/g) and CH₄ (0.045–0.063 mmol/g) gas retention values were small whereas the values corresponding to CO₂ (0.206–0.357 mmol/g) retentions were high for acid smectites. The acid trioctahedral smectite showed higher gas adsorption values than acid dioctahedral smectite. The CO₂ gas adsorption values by acid smectites heated up to around 600 °C, decreased around 10% and 20% for acid trioctahedral and dioctahedral smectites, respectively. After that drastically decreased and at 900 °C both acid smectites showed very small adsorption values. The chemical composition, the structure and the texture of the smectites influenced the gas retention.     

Graphene oxide-sulfated lanthanum oxy-carbonate nanocomposite as an adsorbent for the removal of malachite green from water samples with application of statistical optimization and machine learning computations

Sulfated lanthanum oxy-carbonate nanorods (S-La₂O₂(CO₃) NRs) was synthesized by the reverse micelle microemulsion method and then used to modify graphene oxide nanosheets to synthesize of graphene oxide-sulfated lanthanum oxy-carbonate (GO-S-La₂O₂(CO₃)) nanocomposite. By characterization of S-La₂O₂(CO₃) NRs and GO-S-La₂O₂(CO₃) nanocomposite by the Fourier Transform-Infrared (FT-IR) Spectrophotometry, Field Emission-Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS), Transmission Electron Microscopy (TEM) and X-ray diffraction analysis (XRD), GO-S-La₂O₂(CO₃) was used for treatment of malachite green (MG). To find the optimum removal percentage (RP), influencing parameters were investigated by the response surface methodology based on central composite design (RSM-CCD). Adsorption mechanism was evaluated by Dubinin–Radushkevich (D-R), Langmuir, Temkin, Freundlich (two parameter equations) and Sips (Three parameter equations) isotherms and based on the results the adsorption of MG into the GO-S-La₂O₂(CO₃) nanocomposite obeyed by the Freundlich isotherm with the maximum adsorption capacity of 555.5 mg g^?1. Also, the results of kinetic analysis show that the adsorption of MG onto the GO-S-La₂O₂(CO₃) nanocomposite followed by the pseudo second order kinetic model. For estimation of adsorption behavior, different machine learning techniques are used and based on the results; ANFIS model has the confidential operation because of fuzzy procedure and flexibility of data mining in distributed adsorption data.     

配合物[Fe(bipy)2]3+修饰的MCM-41的合成与表征

以γ－氨丙基修饰介孔分子筛ＭＣＭ－４１内孔壁,将引入的γ－氨丙基与金属配位离子［Ｆｅ（ｂｉｐｙ）_２］^３＋通过配位键首次合成了金属配位化合物修饰的ＭＣＭ－４１（ＭＣＭ－ａｐ－Ｆｅ（ｂｉｐｙ）_２）．通过ＸＲＤ,７７Ｋ氮气吸附－脱附曲线,固体ＵＶ－ｖｉｓ漫反射光谱和循环伏安曲线表征了复合物ＭＣＭ－ａｐ－Ｆｅ（ｂｉｐｙ）_２。由于［Ｆｅ（ｂｉｐｙ）_２］^３＋的引入,使 ＭＣＭ－ａｐ－Ｆｅ（ｂｉｐｙ）_２的结晶度降低, ＢＥＴ比表面积、孔容和最可几孔径急剧下降．γ－氨丙基与Ｆｅ^３＋的配位而使其ＵＶ－ｖｉｓ漫反射吸收光谱与ＭＣＭ－Ｆｅ（ｂｉｐｙ）_２不同;循环伏安特性曲线表明ＭＣＭ－ａｐ－Ｆｅ（ｂｉｐｙ）_２在电化学上比浸渍法制备的ＭＣＭ－Ｆｅ（ｂｉｐｙ）_２稳定．     

Water vapor adsorption of CaCl2-impregnated activated carbon

Activated carbons (AC) impregnated with the hygroscopic salt CaCl₂ were synthesized to enhance the amount of water vapor adsorbed at low relative pressure (P/P₀). Possible applications for these materials are in adsorption heat pumps and desiccant air conditioners. The ACs were synthesized from tissue paper by chemical activation with K₂CO₃ and the porous properties were investigated of a number of materials prepared under a variety of activation conditions. The highest specific surface area (S_BET) (1820 m²/g) was obtained from the sample prepared with a K₂CO₃/sample ratio = 1/1 by mass, activated at 900 °C for 2 h under flowing N₂ (2 L/min). Impregnation with CaCl₂ was performed using 2.4-6.5 M CaCl₂ solutions and a solution volume equal to the pore volume of the AC. XPS surface chemical analysis revealed that the impregnated CaCl₂ was mostly successfully impregnated into the pores while the surface CaCl₂ increased gradually with increasing amount of impregnation. The adsorption of water vapor in the P/P₀ range 0.1-0.3 (ΔW_0.1-0.3) was dramatically increased by CaCl₂ impregnation, the ΔW_0.1-0.3 value reaching 0.52 g/g in the sample impregnated with 70 mass% CaCl₂; this value is much higher than previously reported ΔW_0.1-0.3 values.     

Synthesis of MCM-41 nanoparticles from stem of common reed ash silica and their application as substrate in electrooxidation of methanol

In this work, stem of common reed ash (SCRA) is introduced as a new source of silica in the preparation of mesoporous materials. Mesoporous silicate MCM-41 nanoparticles were synthesized hydrothermally using sodium silicate prepared from SCRA as a silica source. The characterization of MCM-41was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N\(_{2}\) adsorption/desorption (BET) and transmission electron microscopy (TEM). SEM shows that MCM-41 nanoparticles are sphere-like with size in the range of 30–50 nm with some degree of agglomeration. TEM image of the synthesized sample shows the open framework structure of MCM-41. A type IV isotherm can be observed from adsorption/desorption curves, which is the characteristic of mesoporous materials. The prepared MCM-41 nanoparticles were used as substrate to facilitate the oxidation of methanol through the modification with an electroactive species. The modification was achieved by impregnation of MCM-41 pores with \(\hbox {Ni}^{2+}\) ions (Ni-doped MCM-41). A modified carbon paste electrode (CPE) was prepared by mixing Ni-doped MCM-41 with carbon paste (NiMCM-41CPE). Cyclic voltammetry of NiMCM-41CPE shows an increment in current density of methanol oxidation in comparison with CPE in alkaline solution. Moreover, a decrease in the overpotential of methanol oxidation occurred on the surface of modified electrode. The effects of some parameters such as scan rate and methanol concentration are also investigated on the behaviour of NiMCM-41CPE. Also, the heterogeneous electron transfer rate for the catalytic reaction (k) of methanol is calculated.     

Preparation and use of chemically modified MCM-41 and silica gel as selective adsorbents for Hg(II) ions

Adsorbents for Hg(II) ion extraction were prepared using amorphous silica gel and ordered MCM-41. Grafting with 2-(3-(2-aminoethylthio)propylthio)ethanamine was used to functionalize the silica. The functionalized adsorbents were characterized by nitrogen adsorption, X-ray diffraction, 13C MAS NMR spectroscopy and thermogravimetric analysis. The adsorption properties of the modified silica gel and MCM-41 were compared using batch method. The effect of pH, stirring time, ionic strength and foreign ions were studied. The extraction of Hg(II) ions occurred rapidly with the modified MCM-41 and the optimal pH range for the extraction by the modified materials was pH 4-7. Foreign ions, especially Cl- had some effect on the extraction efficiency of the modified silica gel and the modified MCM-41. The adsorption behavior of both adsorbents could be described by a Langmuir model at 298 K, and the maximum adsorption capacity of the modified silica gel and MCM-41 at pH 3 was 0.79 and 0.70 mmol g(-1), respectively. The modified MCM-41 showed a larger Langmuir constant than that of the modified silica gel, indicating a better ability for Hg(II) ion adsorption. The results indicate that the structure of the materials affects the adsorption behavior. These materials show a potential for the application as effective and selective adsorbents for Hg(II) removal from water.     

Preparation of a novel Fe3O4/graphite oxide nanosheet/citric acid-crosslinked β-cyclodextrin polymer composite to remove methylene blue from water

A novel composite basing on the Fe₃O₄ nanoparticle, the graphite oxide nanosheet (GON), and the citric acid-crosslinked β-cyclodextrin polymer (CA-CDP) was prepared for the purpose of removing the methylene blue (MB) dye from water. The structure of the resultant Fe₃O₄/GON/CA-CDP composite was investigated by the scanning electron microscope, the two dimensional EDS mapping, the thermal gravimetric analyzer, the Fourier transform infrared spectroscope, the wide angle X-ray diffraction, the X-ray photoelectron spectroscope, and the zeta potential measurement. The Fe₃O₄/GON/CA-CDP composite not only had a good MB adsorption capacity of 173 mg/g but also a high saturation magnetization of 36.4 emu/g. It was found that the MB adsorption capacity of the Fe₃O₄/GON/CA-CDP composite increased with the increasing initial MB solution pH value especially in the low-pH-value range. Moreover, the MB adsorption mechanism, the MB adsorption isotherm, and the MB adsorption kinetic of the Fe₃O₄/GON/CA-CDP composite were investigated. It was found that 1) the good adsorption ability of the Fe₃O₄/GON/CA-CDP composite for the MB dye originated from the electrostatic attraction, the Lewis acid-Lewis base interaction, the host-guest supramolecular interaction and the π-π interaction, and 2) the MB adsorption isotherm and the MB adsorption kinetic of the Fe₃O₄/GON/CA-CDP composite could be well explained by the Sips model and the intraparticle diffusion model, correspondingly.     

Carbon dioxide adsorption using amine-functionalized mesocellular siliceous foams

Mesocellular siliceous foams (MCFs) with and without remaining template were prepared and modified by polyethylenimine (PEI) or mixed amines [Diethylenetriamine and PEI or 3-aminopropyltrimethoxysilane (APTMS) and PEI]. These samples were evaluated for their adsorption capacities for CO₂ at different temperatures. With the increase of PEI loading, the optimal adsorption temperature shifts to higher temperature for samples prepared in our study. The remaining template in MCF materials plays an important role in promoting CO₂ adsorption capacity, which could be 3.24 mmol/g when the amount of PEI loading is 70 % at 85 °C. Meanwhile, the remaining template contributes greatly to the dispersion of PEI, resulting in higher adsorption capacity at low temperature. The effect of the amount of remaining template was studied, and it was found that CO₂ adsorption capacity decreases with increasing template. The CO₂ adsorption capacities for mixed-amine-modified MCFs are higher than those of the samples modified by PEI only, which was ascribed to the better dispersion of PEI. MCF modified with the mixing of APTMS and PEI exhibited highest adsorption capacity of 2.67 mmol/g at 50 °C. These findings reveal that pore structure, PEI loading, PEI dispersion, and remaining template work together to influence the CO₂ adsorption performance.     

Performance of montmorillonite/graphene oxide/CoFe2O4 as a magnetic and recyclable nanocomposite for cleaning methyl violet dye-laden wastewater

The purpose of this research was to improve the adsorption properties of montmorillonite (MMT) using graphene oxide (GO) and CoFe₂O₄ magnetic nanoparticles for methyl violet (MV) removal. The surface analyses were done on the fresh and used composite. The Langmuir isotherm had more ability to describe data than other studied models (Freundlich, Redlich–Peterson, and Toth). The maximum adsorption capacity of MV by MMT, MMT/CoFe₂O₄, and MMT/GO/CoFe₂O₄ was computed to be 59.61 mg/g, 91.27 mg/g, and 97.26 mg/g, respectively. Obtained data for all adsobers were more consistent with the pseudo-second-order kinetic model (R² > 0.92). The thermodynamic study showed that the MV adsorption by MMT, MMT/CoFe₂O₄, and MMT/GO/CoFe₂O₄ is spontaneous and exothermic. The ad(de)sorption of MV pollutant was studied up to 10 stages. A textile wastewater sample was treated by using the adsober. The MMT/GO/CoFe₂O₄ magnetic composite demonstrates the high adsorption capacity and suitable reusability toward the MV removal from aqueous media.     

Error Anlaysis Studies of Dye Adsorption onto Activated Carbon from Aqueous Solutions

Adsorption of tartrazine and methylene blue from aqueous solution onto activated carbon has been investigated. Experimental datas obtained from dye adsorption have been studied by five two-parameter (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, and Frumkin), five three-parameter (Redlich-Peterson, Sips, Toth, Radke-Prausnitz, Koble-Corrigan) isotherm models. In this study, eight nonlinear error functions (sum squares errors, hybrid fractional error function, Marquardt's percent standard deviation, average relative error, sum of absolute error, the coefficient of determination, nonlinear chi-square test, and standard deviation of relative errors) were examined for isotherm equations. In order to clarify the adsorption kinetics fit of pseudo-first order and pseudo-second order kinetic models were used. The best fitting isotherm model was the Radke-Prausnitz and kinetics model was pseudo-second order for two dyes. Adsorption experiment showed that the maximum capacity of activated carbon's for methylene blue and tartrazine were 28.571 and 18.182 mg.g^?1, respectively.     

Preparation and characterization of epoxy composites filled with functionalized nano-sized MCM-41 particles

Mono-dispersed nano-sized MCM-41 (M (with template)) particles were synthesized by sol–gel reaction. The effect of interface modification on the properties of epoxy composites was investigated. Modifications were carried out either by substituting silanol groups on the surface or in the mesopore channels into amine (M-NH₂), calcinating mixture template in the mesopore channels (M(without template)), or recalcinating them at higher temperature to remove silanol groups (–OH) in the mesopore channels or on the surface (CM). Transmission electron micrograph results showed that the dispersing of MCM-41 nanoparticles was not influenced by the modification, while –NH₂ group indeed modified the mesopore channels or the surface of MCM-41 particle by using IR, XRD, and N₂ adsorption–desorption. In addition, tensile tests suggested that M-NH₂ nanoparticles could simultaneously provide epoxy matrix with strengthening and toughening effects. However, due to the different interfacial structures between the fillers and the matrix, the mechanical properties of the composites filled by M-NH₂ were much better than those of composites filled by MCM-41 (without template), MCM-41 (with mixture template), and CM.     

Characterization of Zr-based MCM-41 mesoporous molecular sieves obtained by microwave irradiation or hydrothermal method

Zr-based MCM-41 mesoporous molecular sieves (ZrMCM-41) were successfully synthesized by microwave irradiation method and hydrothermal method, respectively. The obtained samples were characterized by XRD, TEM, FT-IR and N₂ physical adsorption. The results show that the samples synthesized by the two different methods both possess typical hexagonal mesoporous structure of MCM-41 and high specific surface areas (over 800 m²/g). After calcination at 750°C for 3 h or hydrothermal treatment at 100°C for 6 days, the mesoporous structure of the samples still retained, however, the mesoporous ordering is poor. Under the comparable conditions, the reaction time required in the synthesis of ZrMCM-41 by microwave irradiation method was greatly reduced, and microwave irradiation method is eco-friendly and is easy to operate.