Photocatalytic activity and kinetics for acid yellow degradation over surface composites of TiO_2-coated activated carbon under different photocatalytic conditions

TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.

Aluminum and Activated Alumina Powder Additions on Microwave Synthesis of Al_(4)SiC_(4)

Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.

Structural Characterization and Property Study on the Activated Alumina-activated Carbon Composite Material

AlCl3,NH3·H2O,HNO3 and activated carbon were used as raw materials to prepare one new type of activated alumina-activated carbon composite material.The influence of heat treatment conditions on the structure and property of this material was discussed;The microstructures of the composite material were characterized by XRD,SEM,BET techniques;and its formaldehyde adsorption characteristic was also tested.The results showed that the optimal heat treatment temperature of the activated alumina-activated carbon composite material was 450 ℃,iodine adsorption value was 441.40 mg/g,compressive strength was 44 N,specific surface area was 360.07 m2/g,average pore size was 2.91 nm,and pore volume was 0.26 m3/g.According to the BET pore size distribution diagram,the composite material has dual-pore size distribution structure,the micro-pore distributes in the range of 0.6-1.7 nm,and the meso-pore in the range of 3.0-8.0 nm.The formaldehyde adsorption effect of the activated alumina-activated carbon composite material was excellent,much better than that of the pure activated carbon or activated alumina,and its saturated adsorption capacity was 284.19 mg/g.

Mesoporous activated carbon-zeolite composite prepared from waste macadamia nut shell and synthetic faujasite

Novel activated carbon-zeolite composite adsorbent was prepared from macadamia shell bio-waste and synthetic zeolite X using hydrothermal treatment.Characterisation studies revealed mainly mesoporous structure with 418 m^2·g^(-1) BET surface area with faujasite clusters on the carbon carrier.Sorption capacity for methylene blue model pollutant increased from 85 to 97 mg·g^(-1) with the temperature increase from 25 to 45 ℃, and improved with increasing pH.Nonlinear regression analyses found accurate fit to the pseudo-first-order kinetics model and intra-particle diffusion rate controlling mechanism.Excellent fits to the Jovanovic isotherm model indicated monolayer coverage on chiefly homotattic surfaces with variable potential.The thermodynamic analysis confirmed spontaneous and endothermic physisorption process.The spent adsorbent was regenerated with 20% capacity loss over five reuse cycles.Although the adsorbent was developed for ammonia, heavy metal and organic matter removal from water sources, the results also indicate good performance in cationic dye removal from wastewaters.

The performance of activated carbon/NiFe_(2)O_(4) magnetic composite to retain heavy metal ions from aqueous solution

A novel magnetic activated carbon composite(AC/NiF) was synthesized by a precipitation method and applied in retention of Cu(Ⅱ),and Zn(Ⅱ) ions from aqueous solutions.The impact of different sorption parameters such as:equilibration time,solution pH value,competing cations and ionic strength on the amount sorbed of Cu(Ⅱ),and Zn(Ⅱ) was clarified.Results illustrated that the magnetic composite had retention ability towards both metal ions significantly higher than that of activated carbon(AC).The magnetic composite exhibited an affinity to adsorb Cu(Ⅱ) higher than Zn(Ⅱ) ions.The maximum sorption capacities(Q_(max)) of the applied magnetic composite(AC/NiF)towards Cu(Ⅱ) and Zn(Ⅱ) were 105.8 and 75.1 mg·g^(-1),respectively.Retention of Cu(Ⅱ) and Zn(Ⅱ) was proposed to be achieved though an ion exchange and surface adsorption in neutral conditions,while precipitation was believed to be the relevant mechanism in their removal from basic solutions.The kinetic studies showed that sorption process followed the kinetics of pseudo-second-order reactions with rate constant of 3 × 10^(-3) and 2 × 10^(-3) min^(-1)for sorption of Cu(Ⅱ) and Zn(Ⅱ) onto AC/NiF composite.Removal of Cu(Ⅱ) slightly decreased with increasing the ionic strength of aqueous solution,using NaCl as a background electrolyte.In contrast,presence of Mn(Ⅱ),Mg(Ⅱ)and Co(Ⅱ) in reaction solutions highly depressed the sorption of Cu(Ⅱ) and Zn(Ⅱ) with a competing efficiency followed the order:Mg(Ⅱ)> Mn(Ⅱ)> Co(Ⅱ).The magnetic composite was rapidly recovered from aqueous solution by an external magnetic field,and effectively regenerated using 0.1 mol L^(-1) HCl and 0.1 mol L^(-1) FeCl_(3) as eluents.Sorption of Cu(Ⅱ) and Zn(Ⅱ) onto the surface of AC/NiF composite occurred via a spontaneous reaction.And thermodynamically favorable process had ΔH~o values of 30.9 kJ·mol^(-1) and 19.7 kJ·mol^(-1),respectively.The results confirm that the magnetic composite can be viewed as a promising novel composite opens new opportunities for the attainment of required adsorption and operative magnetic separation.

Adsorption of Indigo Carmine Dye by Composite Activated Carbons Prepared from Plastic Waste (PET) and Banana Pseudo Stem

This study is on the adsorption of indigo carmine dye by composite activated carbons prepared from banana pseudo stems and plastic waste. The activated carbons named TB1P1, TB1P1h and TB2P1 were obtained by pyrolysis at 700°C under steam of raw materials at different ratios (1:1 and 2:1). They were characterized by different techniques such as SEM/EDX, Raman Spectroscopy, FTIR, XRD, TGA/DTA and BET/BJH. Analyses indicate amorphous structures with specific surface areas of 424.37;385.45 and 338.84 m2/g for TB1P1, TB1P1h and TB2P1 respectively. The study of the adsorption of indigo carmine dye by these adsorbents was carried out by varying parameters such as contact time, mass of adsorbent and initial concentration of the dye. The maximum retention is 94.71%, 86.18% and 84.17% for TB1P1, TB1P1h and TB2P1 respectively after 60 min of stirring, for a pH = 4.6 using 0.6 g of adsorbents. The adsorption of indigo carmine follows well, the Langmuir model, with the most suitable kinetics as pseudo second order.

Mechanosynthesis as a Simple Method to Obtain a Magnetic Composite (Activated Carbon/Fe3O4) for Hyperthermia Treatment

A large number of magnetic nanomaterials have been studied for their hyperthermic potential, such as iron oxide based materials. These are embedded in different matrices to improve their properties. In this paper magnetite was synthesized by the coprecipitation method and an activated carbon/magnetite composite was obtained by mechanosynthesis (400 rpm, 3 h). The samples were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), IR-FT spectroscopy and Scanning Electron Microscopy (SEM). Furthermore, composite heating curves as well as hemolysis tests were performed. The composite showed a superparamagnetic behavior due to its low coercivity index (8.92 Oe) and a high saturation magnetization (40.12 emu/g). SEM images showed that the magnetite was observed on the surface of activated carbon and also the IR-FT spectra indicated that oxygenated groups on the activated carbon surface were responsible for the anchoring of magnetite in the surface, with particle sizes between 9 and 14 nm. Heating results indicated that a composite mass of 18 mg reach a temperature of 45.6&degC in a low frequency magnetic field (10.2 kA and 200 kHz). Hemolysis tests indicated that the composite is a non-hemolytic material (4.7% hemolysis). These results demonstrate that the material can be used in magnetic hyperthermia techniques for cancer treatment.

Photocatalytic properties of TiO_2 bonded active carbon composites prepared by SOL-GEL

Photocatalyst of TiO2 bonded active carbon （TiO2/AC）, was prepared via sol-gel method from a mixture of TiO2 sol with active carbon. Post heat treatment was performed at 250 ℃ for 2 h in air and then kept at 400 ℃ to 600 ℃ under a flow of nitrogen for 2 h. The TiO2/AC composites obtained were characterized by SEM, XRD, UV-vis and BET. The photocatalytic activities of the TiO2/AC composites were studied in comparison with TiO2, AC, P-25 and a mixture of TiO2 and AC, respectively. The Ramnant rate of Rhodamine B absorbed by the active carbon is found to be almost 70% and the remnant rates of the Rhodamine B decolorized by TiO2 and the mixture of TiO2 and the active carbon are 30% and 25%, respectively. However, nearly complete removal of Rhodamine B is observed for a TiO2/AC composite after 200 min under UV irradiation, which will take the P-25 commercial product 5 h. Therefore, the TiO2/AC composite is much more effective in decolorization of aqueous Rhodamine B. In addition, the composite can be easily separated from solutions.

High-Resolution Records of the Holocene Paleoenvironmental Variation Reflected by Carbonate and Its Isotopic Compositions in Bosten Lake and Response to Glacial Activities

The Early Holocene paleoclimate in Bosten Lake on the northern margin of the Tarim Basin, southern Xinjiang, is reconstructed through an analysis of a 953 cm long core （BSTC2000） taken from Bosten Lake. Multiple proxies of this core, including the mineral components of carbonate, carbonate content, stable isotopic compositions of carbonate, Ca/Sr, TOC and C/N and C/S of organic matter, are used to reconstruct the climatic change since 8500 a B.P. The chronology model is made by nine AMS 14C ages of leaves, seeds and organic matter contained in two parallel cores. The climate was cold and wet during 8500 to 8100 a B.P. Temperature increased from 8100 to 6400 a B.P., the climate was warm and humid, and the lake expanded. The lake level was highest during this stage. Then from 6400 to 5100 a B.P., the climate became cold and the lake level decreased slightly. During the late mid-Holocene, the climate was hot and dry from 5100 to 3100 a B.P., but there was a short cold period during 4400 to 3800 a B.P. At this temporal interval, a mass of ice and snow melting water supplied the lake at the early time and made the lake level rise. The second highest lake level stage occurred during 5200 to 3800 a B.P. The climate was cool and wet during 3100 to 2200 a B.P., when the lake expanded with decreasing evaporation. The lake had the last short-term high level during 3100 to 2800 a B.P. After this short high lake level period, the lake shrank because of the long-term lower temperature and reduced water supply. From 2200 to 1200 a B.P., the climate was hot and dry, and the lake shrank greatly. Although the temperature decreased somewhat from 1200 a B.P. to the present, the climate was warm and dry. The lake level began to rise a little again, but it did not reach the river bed altitude of the Konqi River, an outflow river of the Bosten Lake.

Enhanced cycle performance of Li/S battery with the reduced graphene oxide/activated carbon functional interlayer

The high-energy lithium/sulfur(Li/S) battery has become a very popular topic of research in recent years due to its high theoretical capacity of 1672 m Ah/g. However, the polysulfide shuttle effect remains of great concern with a great number of publications dedicated to its mitigation. In this contribution, a three-dimensional(3D) reduced graphene oxide/activated carbon(RGO/AC) film, synthesized by a simple hydrothermal method and convenient mechanical pressing, is sandwiched between the separator and the sulfur-based cathode, acting as a functional interlayer to capture and trap polysulfide species. Consequently, the Li/S cell with this interlayer shows an impressive initial discharge capacity of 1078 m Ah/g and a reversible capacity of 655 m Ah/g even after 100 cycles. The RGO/AC interlayer impedes the movement of polysulfide while providing unimpeded channels for lithium ion mass transfer. Therefore, the RGO/AC interlayer with a well-designed structure represents strong potential for high-performance Li/S batteries.

Study on Treatment of the Pesticide Wastewater by the Composite Process of Biological Active Carbon Filter-Fluid Bed

[ Objectlve] The research aimed to study treatment effect of the pesticide wastewater by the composite process of biological active car- bon filter-fluid bed. [Method] The composite process of biological active carbon filter- fluid bed was applied to treat the mixed pesticide wastewater. The removal efficiencies of CODcr, BODs, NH3-N, SS and the influence factors were investigated. [ Result] The composite process had good treatment efficiency for pesticide wastewater. After running stably, the average removal rates of CODc,, BODs, NH3-N and SS were re- spectively 91.6%, 96.2%, 90.2% and 87.5%. All indices reached the third level cdteda specified in Comprehensive Standard of the Sewage Dis- charge （DB12/356-2008）. [ Conclusionl The whole system operates reliably and simply, and provides a stable, convenient and economical solu- tion for deep treatment of the mixed pesticide wastewater.

Pressure relief-dipping-microwave assisted polymerization of melamine-L-aspartic acid resin at activated carbon for purification of L-threonine fermented crude product

L-threonine(L-Thr) obtained by fermentation often contains vestigial hydrosoluble Pb(Ⅱ), Fe(Ⅱ), L-glutamic acid(L-Glu) etc., which affect the product quality. Poly melamine and L-aspartic acid(L-Asp) resin functional coconut shell activated carbon composite(PMA/AC) was prepared by a pressure relief-dipping-microwave assisted polymerization method for the simultaneous removals. The adsorption capacities of Pb(Ⅱ), Fe(Ⅱ) and L-Glu could reach to 82.34 mg·g^(-1), 57.82 mg·g^(-1) and 102.58 mg·g^(-1) at conditions of pH 5.0, 45 °C and 4 h with an initial concentration of 0.01 mol·L^(-1), respectively. The present PMA/AC was successfully used to the simultaneous removals of vestigial Pb(Ⅱ), Fe(Ⅱ) and L-Glu from the fermented crude product solution of L-Thr. Moreover, the PMA/AC was carefully characterized by FE-SEM, IR et al. analysis techniques, the results show that abundant PMA particles evenly distributed at the inner and outside surface of AC with a size of(50 ± 20) nm.

Development of covalent-organic frameworks derived hierarchical porous hollow carbon spheres based LiOH composites for thermochemical heat storage

Under the joint assistance of its excellent storage strength, accessible long storage lifespan, and high heat utilization efficiency, salt hydrate-based thermochemical heat storage(THS) materials give renewable energy an important outlet to alleviate the pressure of underutilization. Herein, an activated hollow spherical carbon(AHSC) with hierarchical porous architectures converted from covalent-organic frameworks(COFs) is constructed and utilized as the supporting matrix for Li OH.THS composite material for the first time. The obtained Li/AHSC_(3) composites have distinguished hydration performance while manifesting impressive storage ability up to 1916.4 k J kg^(-1)with low operating temperature stemming from the collective effect of the void spherical framework, multimodal porosity, and high surface area of AHSC3. And the Li/AHSC3-40 composite with evidently progressed thermal conductivity is capable of realizing 94.5% heat preservation after twenty-five adsorption-desorption cycles, exhibiting its eminent cyclability and great heat transfer performance. This study not only brings new hope for overcoming the underutilization of low-grade heat but also may enlighten new ideas for enriching the application scenarios of COFs-derived carbonaceous materials.

Activated Carbons Based on Shea Nut Shells (<i>Vitellaria paradoxa</i>): Optimization of Preparation by Chemical Means Using Response Surface Methodology and Physicochemical Characterization

In this study, shea residues (Vitellaria paradoxa) dumped in the wild by the units processing almonds into butter were used in the production of activated carbons. Shea nut shells harvested in the locality of Baktchoro, West Tandjile Division of Chad were used as a precursor for the preparation of activated carbons by chemical activation with phosphoric acid (H3PO4) and sulphuric acid (H2SO4). Central Composite Design (CCD) was used to optimize the preparation conditions, and the factors used were concentration of activating agent (1 - 5 M), carbonization temperature (400°C - 700°C) and residence time (30 - 120 min). The studies showed that at optimal conditions the yield was 51.45% and 42.35%, while the iodine number (IN) was 709.45 and 817.36 mg/g for CAK-P (phosphoric acid activated carbon) and CAK-S (sulphuric acid activated carbon) respectively. These two activated carbons (ACs) which were distinguished by their considerable iodine number, were variously characterized by elementary analysis, pH at the point of zero charge (pHpzc), bulk density, moisture content, Boehm titration, Fourier transform infrared spectroscopy, BET adsorption and scanning electron microscopy. These analyses revealed the acidic and microporous nature of CAK-P and CAK-S carbons, which have a specific microporous surface area of 522.55 and 570.65 m2·g−1 respectively.

Effect of Texture and Surface Chemistry of Palm Nut Hull Activated Carbon on the Adsorption of Pigments and Free Fatty Acids from Vegetable Oils

Activated carbons were produced from palm nut hull,which is a waste material of palm oil extraction industries.Activated carbons having various pore size distributions and surface composition were obtained by conventional carbonization method via the sulphuric acid solution pre-treatment method.The surface areas,mesopore volume and-OH groups of activated carbons increase with the increases of sulphuric acid solution concentration.The activated carbons obtained were tested for the adsorption of pigments and free fatty acids from palm oil and shea butter.It comes out from this study that the amount of adsorbate(i.e.pigments and free fatty acids)fixed increases with the increase of the adsorption temperature and with the increases of mesopore volume.Intraparticle diffusion,pseudo-first-order and pseudo-second-order kinetics models were used to analyze the kinetics data obtained at different temperatures(temperature range 60℃ to 90℃).Among the kinetics models used,the pseudo-second order was the best applicable model to describe the adsorption of oil pigments and free fatty acid onto activated carbons.The activation energies obtained by applying the Arrhenius equation for the adsorption of pigments were low(i.e.less than 40 kJ·mol^-1 for the both vegetables oils),indicating that the adsorption could be assigned to physisorption.

A Novel High Active TiO_2/AC Composite Photocatalyst Prepared by Acid Catalyzed Hydrothermal Method

A high active novel TiO2/AC composite photocatalyst was prepared and used for phenol degradation. It was much more active than P-25 and exhibiting good decantability, less deactivation after several runs and less sensitive to pH change. Diffuse reflectance spectra （DRS） revealed that the electronic change in TiO2 did not occur by the addition of AC. Results of SEM and XRD suggested that better TiO2 distribution can be achieved when optimal AC content was adopted. The performance of the prepared TiO2/5AC catalyst revealed great practical potential in wastewater treatment field.

碳化复合桩(MCP)原理与应用试验研究

介绍了一种基于MgO碳化固化软弱土技术的碳化复合桩(MCP),通过透气管桩向MgO搅拌桩注入CO_(2)气体进行碳化形成新型复合桩。进行了室内模型试验,通过对碳化过程和碳化后的温度、物理、力学等特性的分析,论证了该技术在粉土和淤泥质土中的适应性,结果表明,在MgO充分水化的条件下,不同深度的碳化反应较为均匀;在透气管桩外围存在有效碳化距离和最大碳化距离,在有效碳化距离内可获取良好的碳化效果,揭示了MCP的形成机理与影响因素。在室内试验基础上开展了现场应用试验,结果表明,MCP施工工艺方便、成桩效果好且桩身强度均匀,碳化桩体标贯击数均值为39;其单桩竖向极限承载力为1920 kN,相对于PHC管桩提升37%。室内与现场试验表明,MCP复合桩兼具固碳与加固效果,对岩土工程低碳化发展具有重要意义。

盾构淤泥质废弃黏土氧化镁固化-碳化试验及碳化机制研究

盾构隧道施工产生的废弃土面临堆放、运输及处理等难题,将原材料丰富、生产耗能少、环境友好的MgO用于废弃土固化处理是一个值得探索的方法。通过改变MgO掺量a_(m)、养护龄期T、碳化时间H研究MgO固化-碳化淤泥质废弃黏土界限含水率w、无侧限抗压强度q_(u)、弹性模量E_(50),结合微观形貌及矿物成分变化规律探讨其固化-碳化机制。结果表明:MgO固化-碳化具有明显的加固土体效果,加固效果随a_(m)、T呈先上升后趋于稳定的趋势,随H呈先上升后下降的趋势;不同a_(m)、T下,碳化4h会使土体塑性指数I_(P)降低57%以上,土体可塑性显著下降;不同a_(m)和T的固化-碳化土q_(u)均在H为4h时取得峰值,最高可达1.4MPa,比碳化前强度提升了220%~350%;固化-碳化反应对土体的E_(50)提升受a_(m)影响较大,当a_(m)超过9%时,碳化4h试样的E_(50)增幅在500%左右;MgO固化-碳化过程中水化产物、碳化产物不断生成和发育,形成网状、花朵聚集状的形貌,填充土颗粒间的孔隙,增强了土颗粒间的胶结作用,土体结构更为密实。该研究为长三角地区土压盾构产生的淤泥质废弃黏土的固化-碳化处理与再利用提供了思路。

Preparation and photocatalytic activity of TiO_2-coated granular activated carbon composites by a molecular adsorption-deposition method

TiO2 nanoparticle-coated granular activated carbon (GAC) composite photocatalysts (CPs) were suc-cessfully prepared by a molecular adsorption-deposition (MAD) method. The CPs were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), BET surface area and UV-Vis adsorption spectroscopy, and their photoactivity was evaluated by methyl orange (MO) photodegradation. The results show that small-sized TiO2 nanoparticles were dispersed well, deposited on the surface of GAC, and showed slight blue shift in comparison with pure TiO2. With the increase in TiO2 content, the CPs showed band gaps in lower energy, smaller surface areas and the higher content of Ti3+ ions. Compared with pure TiO2 and others CPs samples, CPs-382 sample showed the highest photoactivity due to the optimum TiO2 content and surface area besides the synergic effect of photocatalytic degradation of TiO2 and adsorptive property of GAC. In addition, the CPs could be very easily reclaimed, recycled and reused for methyl orange removal while high photoactivity is pre-served.

Efficient photoreduction strategy for uranium immobilization based on graphite carbon nitride/activated carbon nanocomposites

Uranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery.Herein,carbon nitride/activated carbon composite materials(CN/AC)were investigated for U(Ⅵ)reduction under visible light.An exceptional boost in photocatalytic activity was observed for CN/AC composites(up to 70 times over the conventional bulk g-C_(3)N_(4)).The strong interactive conjugatedπ-bond structure between g-C_(3)N_(4) and AC accelerated the migration of carriers and then prolonged the electron lifetime.CN/AC composites exhibited excellent compatibility with different water substrates and were resilience to a wide range of p H changes and abundant competitive anions/cations.Quenching experiments and electron microscopy characterization indicated that U(VI)was reduced by photogenerated electrons and deposited on the edge of CN/AC composites.The low-cost,high-performance carbon-based composite material proposed in this work is a potential candidate for the efficient treatment of radioactive wastewater.