水热法可控合成二氧化钛纳米晶及其在染料敏化太阳能电池中的应用

本文报道了水热法可控合成二氧化钛纳米晶及其在染料敏化太阳能电池中的应用.选择合适的有机碱胶化剂,能很好地控制二氧化钛纳米晶的生长,形成不同形貌和粒径的锐钛矿型二氧化钛纳米晶颗粒.染料敏化太阳能电池光电性能测试结果表明,以四乙基氢氧化铵为胶化剂合成的边长为8～13nm的正方形二氧化钛纳米晶构成的光阳极光电性能优于以四丁基氢氧化铵为胶化剂合成的边长为7～10nm的正方形二氧化钛纳米晶以及长18～35nm,宽10～18nm的长方形二氧化钛纳米晶构成的光阳极.用较高浓度的四甲基氢氧化铵胶化剂能合成球形或椭球形亚微米级二氧化钛颗粒,以其为散射中心在光阳极中构建散射层,染料敏化太阳能电池的光电转换效率能由6.77%提高到8.18%.     

Exploration of biomass waste as low cost adsorbents for removal of methylene blue dye: A review

Biomass waste, which is abundantly available has been studied as low cost biosorbent for dye sequestration from waste water. The present review reports on recent development for remediation of methylene blue dye by agricultural waste and fruit peel waste material. The aim of this study was to revise latest literature in the field of dye adsorption and discuss the dye adsorption capacity of different types of adsorbents. The activated carbon prepared from several types of biomass waste material enhances the adsorption efficiency after modification. The variety of activating agents, method of activation, characterization of biosorbent material like SEM, EDAX, BET surface area and FTIR analysis has been explored in the present review. The dye adsorption factors such as effect of pH, agitation time, temperature, adsorbate and adsorbent dose were discussed. The detailed investigation on applicability of isotherm model, kinetic model and thermodynamic parameters has also been presented. The adsorption kinetics and adsorption isotherm model focus on selectivity of adsorbent. Adsorption mechanism, Influence of surface area, influence of pH_pzc and comparative study of biomass waste adsorbent with other adsorbents have been carried out. The use of biomass waste adsorbents is economically feasible, environmental healthy and found to have outstanding removal capacity of dyes.     

Adsorption study for removal of Congo red anionic dye using organo-attapulgite

The organo-attapulgite was prepared using hexadecyltrimethylammonium bromide (HTMAB) with equation equivalent ratio of HTMAB to CEC of attapulgite added and then used as adsorbent for the removal of Congo red (CR) anionic dye from aqueous solution. Adsorbent characterizations were investigated using infrared spectroscopy and X-ray diffraction. The effects of contact time, temperature, pH and initial dye concentration on organo-attapulgite adsorption for CR were investigated. The results show that the amount adsorbed of CR on the organo-attapulgite increase with increasing dye concentration, temperature, and by decreasing pH. The adsorption kinetics was studied with the pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and the rate constants were evaluated. It was found that the adsorption mechanisms in the dye/organo-attapulgite system follow pseudo-second-order kinetics with a significant contribution of film diffusion. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model, and the maximum adsorption capacity was 189.39 mg g⁻¹ for the adsorbent. Kinetic and desorption studies both suggest that chemisorption should be the major mode of CR removal by the organo-attapulgite. The results indicate that HTMAB-modified attapulgite could be employed as low-cost material for the removal of Congo red anionic dye from wastewater.     

Chitosan/UiO-66 composites as high-performance adsorbents for the removal of methyl orange in aqueous solution

UiO-66 and chitosan/UiO-66 composites were successfully synthesized by varying the mass addition of chitosan which were 0%, 2.5%, 5%, 10%, and 20% of the mass of UiO-66, denoted as UiO-66, Cs(2.5)/UiO-66, Cs(5)/UiO-66, Cs(10)/UiO-66, and Cs(20)/UiO-66, respectively. UiO-66 was modified with chitosan using the impregnation process. The X-ray diffraction patterns of the synthesized materials showed characteristic peaks at 2θ of 7.25° and 8.39°, which matched to that of the reported UiO-66. In addition, the Fourier transform infrared spectroscopy spectra of the materials showed absorption bands at the same wavenumber as UiO-66 and chitosan previously reported. The surface morphology of UiO-66 observed from scanning electron microscopy images was in the form of agglomerated small cube particles, where the smaller particles were observed for Cs(10)/UiO-66. From the N₂ adsorption isotherms, it was found that the Brunauer-Emmett-Teller surface areas of UiO-66, Cs(5)/UiO-66, and Cs(10)/UiO-66 materials were 825.7 m²/g, 835.4 m²/g, and 882.2 m²/g, respectively. The results of the study on adsorption of methyl orange in aqueous solutions showed that Cs(5)/UiO-66 had the highest adsorption capacity of 370.37 mg/g and followed the pseudo–second-order adsorption kinetic with a Langmuir isotherm model.     

Applicability of waste materials--bottom ash and deoiled soya--as adsorbents for the removal and recovery of a hazardous dye, brilliant green

Deoiled soya, an agricultural waste material, and bottom ash, a waste of power plants, have been successfully used for the removal and recovery of the hazardous water-soluble dye brilliant green from water. To remove the dye from water, batch adsorption studies have been carried out by observing the effects of pH, concentration, amounts of adsorbents, size of adsorbent particles, etc. Attempts have also been made to monitor the adsorption process through Langmuir, Freundlich, Tempkin, and D-R adsorption isotherm models. Relevant thermodynamic parameters have also been calculated from these models. The adsorption process has been found endothermic and feasible at all the temperatures. The kinetics of the adsorption was also recorded and indicates pseudo-second-order kinetics in both cases. Kinetic operations also reveal the involvement of a film diffusion mechanism for the deoiled soya adsorption at all the temperatures, while bottom ash undergoes through a particle diffusion mechanism at only 30 °C and at higher temperatures a film diffusion mechanism operates. Bulk removal of the dye has been carried out through column studies for both adsorbents. Attempts have also been made to recover the dye from exhausted columns by eluting sulfuric acid of pH 3.     

Synthesis and characterization of new polymers derived from 2-methyl-m-phenylenediamine as an effective adsorbent for cationic dye removal

The oxidative polymerizations of 2-methyl-m-phenylenediamine were performed to synthesize PMPDIA-A and PMPDIA-B polymers by H₂O₂ (35% aqueous solution) oxidant in acid-catalyzed ethanol and basic aqueous medium. Furthermore, PMPDIA-E polymer of 2-methyl-m-phenylenediamine was enzymatically synthesized by HRP (horseradish peroxidase) enzyme and H₂O₂ (35% aqueous solution) in dioxane/0.1 M phosphate tampon solution (pH = 7) mixture. The structures of 2-methyl-m-phenylenediamine and polymers were confirmed by FT-IR, NMR and UV–Vis spectrometer measurements. Molecular weight distributions, surface morphologies, thermal and fluorescence properties of polymers were determined from GPC, SEM, TG-DTA, DSC and fluorescence spectra analyses, respectively. CV and UV–Vis analyses were performed to determine the HOMO–LUMO energy levels, electrochemical (E_g′) and optical (E_g) band gaps values of MPDIA, PMPDIA-E, PMPDIA-A and PMPDIA-B. The electrochemical and optical band gaps values of polymers were lower than MPDIA, because of their polyconjugated structures. According to GPC measurements of polymers, the weight average molecular weights were between 5400 and 10400 Da. The fluorescence quantum yield of PMPDIA-E was calculated to be 9.15% in DMSO solution. The adsorption of methylene blue (MB) from aqueous solution on PMPDIA-B was studied. Adsorption isotherms and equilibrium adsorption capacities were determined by the fitting of the experimental data to two well-known isotherm models: Langmuir and Freundlich.     

Multiwalled carbon nanotube/TiO2 nanocomposite as a highly active photocatalyst for photodegradation of Reactive Black 5 dye

A nanocomposite UV‐visible light‐responsive multiwalled carbon nanotube (MWCNT)/titanium dioxide (TiO2) nanophotocatalyst was successfully synthesized by a modified sol‐gel method using titanium isopro...     

Conducting polymer/alumina composites as viable adsorbents for the removal of fluoride ions from aqueous solution

The polyaniline/alumina (PANi-AlO) and polypyrrole/alumina (PPy-AlO) composites were prepared and characterized by FT-IR, SEM and X-ray diffraction studies and were employed as adsorbents for the removal of fluoride ions from aqueous solution by the batch sorption method. The amount of fluoride ions adsorbed per unit mass of the adsorbents was observed to be higher than that by the individual constituents. The maximal amount of adsorption is 6.6 mg/g for PANi-AlO and for PPy-AlO it is 8 mg/g. The Langmuir and Freundlich isotherms were used to describe adsorption equilibrium. The kinetics of the adsorption process was investigated using Natarajan-Khalaf equation and intraparticle diffusion model. FT-IR and XRD pattern of the adsorbent, before and after the adsorption is recorded to get better insight into the mechanism of the adsorption process. The results of equilibrium and spectral investigations revealed that the mechanism of fluoride ion removal by these composites involve both the formation of aluminium-fluoro complexes on the alumina surface and doping/dopant-exchange of fluoride ions in the polymer.     

Converting red mud wastes into mesoporous ZSM-5 decorated with TiO2 as an eco-friendly and efficient adsorbent-photocatalyst for dyes removal

Red mud wastes have been converted into mesoporous zeolite socony mobile-5 (ZSM-5) followed by deposited titanium dioxide (TiO₂) nanoparticles to generate synergy adsorption-photodegradation for removal of dye removal in waste water. The amount of TiO₂ loading was varied to achieve optimum photocatalytic activity while maintaining the mesoporosity and high surface area of ZSM-5. Sol-gel method facilitated the formation of anatase TiO₂ on the ZSM-5. The fourier transform infrared spectra clarified the formation of Si–O–Ti at 957 cm^?1 by the exchanging the hydrogen ion with titanium ion, which proved by decreasing the absorption band of Si–OH and Si–O interaction at 964 and 944 cm^?1, respectively. Sol-gel method also preserved the mesopore diameter of ZSM-5 at 3.5 nm which allow the diffusion of methylene blue (MB) molecules into the pores. However, the surface area and the pore volume were slightly reduced with increasing the TiO₂ loading. The adsorption performance of samples showed that the increasing in the TiO₂ loading led to the decreasing in the adsorption capacity. All samples showed the suitability towards the pseudo second order kinetic. The Langmuir isotherm was suitable to describe the adsorption mechanism by monolayer adsorption. Mesoporosity of ZSM-5 accelerated the adsorption of dye via the increase of mass transfer in the pore channel which confirmed by the low intercept of intraparticle diffusion model at the first stage. The photocatalytic test showed that 10% TiO₂ loading on the ZSM-5 exhibited the highest methylene blue removal followed by 5% and 20% TiO₂ loading. Optimization on the amount of photocatalyst and the pH of solution indicated the reaction favoured 1 g L^?1 of catalysts and at alkaline pH. 10% TiO₂/ZSM-5 also exhibited high stability and reusability up to four reaction cycles. Photocatalytic performance of 10% TiO₂/ZSM-5 was further investigated on photodegradation of malachite green and rhodamine B organic dyes, which showed the photocatalytic efficiency of 73 and 88%, respectively. Superoxide radical, hydroxyl radical, and photogenerated electron were identified as the main active species for MB photodegradation based on the reduction of degradation rate following the addition scavenger molecules.     

水滑石焙烧产物对弱酸艳红B吸附特性研究

以Mg(NO3)2·6H2O和AL(NO3)3 - 9H2O为原料,NaOH、NaCO溶液作混合沉淀剂,采用水热法可制得结晶度很高的、具有规整的层状结构水滑石.水滑石经500℃焙烧可使其结构完全被破坏得对应的焙烧产物,该焙烧产物对弱酸艳红B染料有很强的吸附能力.在200 mL 100 mg/L弱酸艳红B溶液中,加入40...     

Low Temperature Preparation of High Refractive Index and Mechanically Resistant Sol-gel TiO2 Films for Multilayer Antireflective Coating Applications

TiO₂ sol-gel thin films have attracted a large attention for applications which require high refractive index transparent layers. In this work, sol-gel TiO₂ layers were prepared by Aerosol-gel deposition followed by a thermal treatment procedure in air. Depending on the experimental conditions, abrasion resistant and high refractive index layers could be obtained after post-treatment at only 110°C. In this paper, the experimental parameters which allow the preparation of functional TiO₂ sol-gel layers at such low temperature are discussed. It is concluded that the preparation of high refractive index and mechanically resistant TiO₂ layers can be interpreted in terms of competition between polycondensation and densification mechanisms. This result allows to envisage the sol-gel processing at low temperature of multilayer antireflective coatings.     

溶胶-凝胶法制备TiO2负载活化半焦光催化烟气脱硝

利用超声辅助溶胶-凝胶法,以钛酸正丁酯为钛源,制备了TiO2负载于活化半焦的光催化剂。考察了TiO2负载量,煅烧温度和时间,以及水对光催化脱硝活性的影响。利用X射线衍射（XRD）,BET,FT-IR,扫描电镜（SEM）以及能谱分析（EDS）等方法对催化剂进行了表征分析。实验结果表明,TiO2负载量为5.22 %,煅烧温度500 癈,煅烧时间为1 h时,TiO2/SC光催化脱硝剂效果最好,反应3小时后脱硝率仍高于70 %。通过添加自由基捕获剂的方法确定TiO2/ASC光催化脱硝过程中起主要作用的活性物种为?OH和?O2-,而空穴在本实验的光催化过程中几乎不起作用。对催化剂的再生研究发现,高温（400癈）水热一次再生可恢复催化剂脱硝活性至新鲜催化剂的100%,三次再生效果仍为新鲜催化剂脱硝率的80%。     

A simple method for removal of toxic dyes such as Brilliant Green and Acid Red from the aquatic environment using Halloysite nanoclay

This project explains an easy, simple and eco-friendly method to remove some toxic dyes like Brilliant Green and Acid Red from aquatic solution by technique of solid-phase extraction that uses Halloysite nanoclay eco-friendly solid phase as absorbent surface for adsorption of dye. The physical properties of the HNC such as scanning electron microscopy, transmission electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and surface area analysis were studied. The best conditions like pH of the solution, HNC weight, contact shaking time, the temperature of the solution, and ionic strength were investigated for removal effectiveness. The experimental data of the adsorption process showed that HNC can remove most of the dyes within 30 min, with an adsorption capacity of 12.5 mg/g for A.R dye and 13.9 mg/g for B.G dye on HNC solid phase at optimum conditions. The removal process of dyes on HNC was studied kinetically and thermodynamically, and the data confirms that the pseudo-second-order kinetic model was able to describe the adsorption process. Thermodynamic data confirms the process was spontaneous andexothermic in nature for A.R dye, while was spontaneous and endothermic in nature for B.G dye. Finally, the effectiveness of HNC was inspected by removing dyes from three various real samples, and the results showed high performance in removing dyes on HNC for four consecutive cycles.     

溶胶-凝胶自燃烧法制备的CuO-ZnO/Al2O3及催化二氧化碳加氢制甲醇的性能研究

采用溶胶-凝胶自燃烧法,以柠檬酸为燃料制备了多种CuO-ZnO/Al2O3催化剂.利用N2静态吸附(BET)、X射线衍射(XRD)、扫描电子显微镜(SEM)、X-射线光电子能谱(XPS)和H2程序升温还原(H2-TPR)等方法研究了柠檬酸与硝酸盐比例关系对催化剂物化性质,形貌和还原性能的影响.并将其用于二氧化碳加氢制甲醇反应,考察催化剂的CO2转化率,甲醇选择性以及甲醇时空收率等催化性能.实验结果表明,当柠檬酸用量等于化学计量比时,CuO-ZnO/Al2O3催化剂的催化性能最好,当柠檬酸用量大于化学计量比时,催化性能次之,且变化不大,但当柠檬酸用量小于化学计量比时,催化性能明显降低.这一结果与其物化性质和还原性能有关,当柠檬酸用量等于或大于化学计量比时,催化剂中CuO颗粒较小,分散均匀,且分散度高.     

B2O3对Ag/TiO2-Al2O3吸附剂的柴油吸附脱硫性能影响

采用浸渍法制备了不同B₂O₃负载量(e.g. 5%~20% (w))的Ag/TiO₂-B₂O₃-Al₂O₃吸附剂。以含硫量为245.36mg(S)/L 的商业柴油作为考察对象,常温常压下采用静态评价进行吸附脱硫性能研究。结果表明,B₂O₃改性后的Ag/TiO₂-Al₂O₃吸附剂的柴油吸附脱硫活性有了较大提高,当B₂O₃的负载量为15%时,吸附剂的吸附脱硫活性最高,2%Ag/4%TiO₂-15%B₂O₃-Al₂O₃ (w)的饱和吸附硫容达到2.36mg(S)/g 吸附剂。这对于未经预处理的商业柴油而言,吸附脱硫活性已经达到较高水平。采用N₂物理吸附、O₂化学吸附、X射线衍射(XRD)、NH₃程序升温脱附(NH₃-TPD)、傅里叶红外光谱(FT-IR spectra)、¹¹B核磁共振(¹¹B-NMR)等表征手段对不同负载量B₂O₃改性Ag/TiO₂-Al₂O₃吸附剂的织构性质、晶相结构和表面酸性的影响进行研究。关联活性测试和表征结果发现,吸附剂的吸附脱硫活性主要与吸附剂的表面弱酸性有关,而B₂O₃改性在吸附剂表面引入了较多的四配位的BO₄物种,能显著增加吸附剂表面弱酸性位点数量,提高吸附剂的吸附脱硫活性。     

Sol-gel synthesis of TeO<Subscript>2</Subscript>-based materials using citric acid as hydrolysis modifier

Sol-gel processing of tellurium oxide has been investigated in the tellurium isopropoxide/citric acid/isopropanol/water system. As evidenced by Fourier transformed infrared spectroscopy (FTIR), citric acid has been found to be a relevant chemical modifier to control hydrolysis-condensation reactions of highly reactive tellurium isopropoxide Te(OCH(CH₃)₂)₄. Thus, depending on the main synthesis chemical parameters such as alkoxide concentration, water and modifier ratios, colloidal sols and gels have been successfully synthesised. The thermal behaviour of the dried gels has been investigated by X-ray diffraction, differential scanning calorimetry coupled with thermogravimetry and also FTIR spectroscopy. On the one hand, the crystallisation of the non-centrosymmetric γ-TeO₂ polymorph as well as the α-TeO₂ phase which the crystallite size ranges from a few ten nanometers (∼50 nm) to a few microns as a function of heat treatment, and, on the other hand, the synthesis of homogeneous sols which can be handled in air and so particularly suitable for the elaboration of thin films provide new opportunities for making tellurite based materials and thin film devices for practical applications.     

A comparative study of microwave and chemically treated Acacia nilotica leaf as an eco friendly adsorbent for the removal of rhodamine B dye from aqueous solution

The use of cheap and eco friendly adsorbents prepared from freely and abundantly available Acacia nilotica leaves have been investigated by batch methods. Microwave treated A. nilotica leaves (MVM) are more effective than chemically treated A. nilotica leaves (CVM) for the removal of rhodamine B (RH B) from aqueous solution. The effect of initial pH, contact time and initial dye concentration of RH B onto CVM and MVM has been investigated. The applicability of the linear form of Langmuir model to CVM and MVM was proved by the high correlation coefficients R² = 0.9413 and 0.9681 for RH B adsorption. The R² values were greater than 0.994 for all RH B concentrations, which indicates the applicability of the pseudo-second-order kinetic model. The recycling ability of MVM is greater than CVM. The preparation of MVM does not require an additional chemical treatment step and it attains rapid equilibrium. Hence it is agreeing with the principles of green chemistry and less time is required to possess high adsorption of RH B. Therefore, the eco friendly adsorbent MVM is expected to be environmentally and economically feasible for the removal of RH B from aqueous solutions.     

Effects of CeO2 and CaO composite promoters on the properties of eggshell Ni/MgO-Al2O3 catalysts for partial oxidation of methane to syngas

The effects of CeO₂ and CaO composite promoters on the properties of eggshell Ni/MgO-Al₂O₃ catalysts of 1.5 mm diameter for the partial oxidation of methane to syngas were investigated. The addition of 1wt.% promoters could enhance the catalytic performance of the Ni/MgO-Al₂O₃ catalyst, while further increasing the promoter content to 4wt.% results in the decrease of reactivity. The catalytic property is related to the oxidizability of surface nickel species.     

Properties of TiO2-polyacrylic acid dispersions with potential for molecular recognition

Titanium dioxide (TiO₂)/polyacrylic acid (PAA) (TiO₂/PAA) particles were formed by mixing PAA and an acidic solution of TiO₂ nanoparticles in dimethylformamide (DMF) followed by heat treatment. TEM and particle analysis showed that the resulting particles had a narrow size distribution. The colloid was very stable and aggregation was not observed over a wide pH range (3–9) or at high salt concentration. The residual carboxylic acid of PAA could be modified via EDC/NHS activation to form an amide bond with a protein. An antibody was attached to the hybrid nanoparticle and specific binding to antigen was monitored by surface plasmon resonance. The results suggest that TiO₂/PAA nanoparticles are candidates as the base component of a photocatalytic system with potential for substrate selectivity.     

ZnO and TiO2 clusters as catalyst in the addition and abstraction reaction of acrylic acid with the OH radical

The present work displays the theoretical analysis on the role of metal oxide clusters as an effective catalyst in the reaction between acrylic acid and OH radical, which has an energy barrier of 12.4 kcal/mol. The formation of metal oxide cluster such as ZnO and TiO₂ with varying size from monomer to hexamer is analyzed using cohesive energy, which increases with cluster size. Adsorption of acrylic acid on clusters reveals that dimer ZnO and tetramer TiO₂ are good adsorbed entities. The dimer ZnO and tetramer TiO₂ clusters have reduced the barrier height. However, from the thermodynamical analysis of H-abstraction and OH addition reaction, the dimer ZnO cluster is found to be a good catalyst than a tetramer TiO₂ cluster. The favorable H abstraction and OH addition reactions are feasible at the active methylene group (–CH). OH addition reactions dominate over the H abstraction reaction. Further, the presence of metal oxide clusters enhances the rate of the reaction between acrylic acid and OH radical. The kinetics of the favorable reaction with a dimer ZnO cluster has a rate constant of 7.80 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, which is higher than the literature report (1.75 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹). Overall, ZnO and TiO₂ metal oxide clusters can be effectively utilized as catalyst.