Removal of congo red using activated carbon and its regeneration

Activated carbon is used for the removal of colored toxic congo red dye. The effects of different operating conditions like, initial dye concentration, contact time, pH and temperature are studied for adsorption of congo red by a known amount of activated carbon (1.0g/L) under stirred batch condition. The zero point of charge of the activated carbon is found about 6.6. About 90% dye is removed for initial concentration of 50 and 100mg/L, it is about 80% at pH 7.0. Maximum adsorption (about 100%) of dye is observed at pH 2.0 for the concentration range studied here. Freundlich isotherm is found to fit the equilibrium data more adequately. Pseudo second order kinetic model explain successfully the kinetic data. The surfactant enhanced carbon regeneration (SECR) technique using both cationic and anionic surfactants is adopted for the regeneration of spent carbon by desorbing the dye. A kinetic model for dye desorption from the commercial activated carbon (CAC) is also proposed. Anionic surfactants show better performance than the cationic ones. Efficiency of dye desorption using surfactants is also compared with the desorption using pH change.     

Removal of congo red from aqueous solution by adsorption onto acid activated red mud

The objective of this study is to remove the congo red (CR) anionic dye, from water by using the acid activated red mud in batch adsorption experiments. The effects of contact time, pH, adsorbent dosage and initial dye concentration on the adsorption were investigated. The pH of the dye solution strongly affected the chemistry of both the dye molecules and activated red mud in an aqueous solution. The effective pH was 7.0 for adsorption on activated red mud. It was found that the sufficient time to attain equilibrium was 90 min. The adsorption isotherms were analyzed using the Langmuir, the Freundlich, and the three parameter Redlich-Peterson isotherms. The Langmuir isotherm was the best-fit adsorption isotherm model for the experimental data obtained from the non-linear chi-square statistic test.     

Study of the degradation behaviour of dimethoate under microwave irradiation

In this work, the degradation of dimethoate under microwave irradiation assisted advanced oxidation processes (MW/oxidants) were studied. The efficiencies of the degradation of dimethoate in dilute aqueous solutions for a variety of oxidants with or without MW irradiation were compared. The results showed that the synergistic effects between MW and K(2)S(2)O(8) had high degradation efficiency for dimethoate. Simultaneously, UV/TiO(2)/K(2)S(2)O(8) photocatalytic oxidation degradation of dimethoate was investigated. The experimental results indicated that the method of microwave degradation of organic pollutants in the presence of oxidant could reduce reaction time and improve product yield. Microwave irradiation was an advisable choice for treating organic wastewaters and has a widely application perspective for non- or low-transparent and fuscous dye wastewaters.     

Study on decolorization of Rhodamine B by raw coal fly ash catalyzed Fenton-like process under microwave irradiation

Coal fly ash (CFA) catalyzed Fenton-like process was studied under microwave (MW) irradiation for the decolorization of Rhodamine B (RhB) wastewater. The physical-chemical properties of CFA were characterized, including the specific surface area, micromorphology, chemical and crystal components, and the distribution and chemical valence of metallic elements. The metallic oxidants in the CFA indicate CFA can work as Fenton-like catalyst and MW-absorbent simultaneously. The results reveal OH is more significant in the decolorization of RhB than HO₂ and O₂^?. The generation of more OH in the MW-Fenton-like process (293–326 K) than that in the conventional heated Fenton-like process (326 K) reflects the function of hot spot effect and possible non-thermal effect of MW. Under the optimum condition ([H₂O₂] 2 mmol L^?1, [CFA] 15 g L^?1, pH 3, P_MW 0.1 kW), the decolorization rate reaches 91.6% after 20 min. The intrinsic kinetic model of RhB decolorization is $-\frac{\mathrm{d}{C}_{\mathrm{R}\mathrm{h}\mathrm{B}}}{\mathit{dt}}={1.76\times 10}^{-4}·C_{\mathrm{R}\mathrm{h}\mathrm{B}}·C_{{\mathrm{H}}_2{\mathrm{O}}_2}^{1.89}·C_{\mathrm{C}\mathrm{F}\mathrm{A}}^{1.97}-\mathrm{d}{\mathrm{C}}_{\mathrm{R}\mathrm{h}\mathrm{o}\mathrm{d}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{B}}/\mathrm{d}\mathrm{t}=1.76\times {10}^{-4}·{\mathrm{C}}_{\mathrm{R}\mathrm{h}\mathrm{o}\mathrm{d}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{B}}·{\mathrm{C}}_{{\mathrm{H}}_2{\mathrm{O}}_2}^{1.89}·{\mathrm{C}}_{\mathrm{c}\mathrm{o}\mathrm{a}\mathrm{l}\mathrm{f}\mathrm{l}\mathrm{y}\mathrm{a}\mathrm{s}\mathrm{h}}^{1.97}$. The loss of catalytic metallic elements causes the decline of catalytic capacity of CFA. The energy consumption (4313.3 kW·h kg^?1 RhB) is a limitation for the MW-Fenton-like process, which can be overcame by the safe application of nuclear energy. The intermediates and the path of RhB decolorization were detected and proposed, respectively.     

微波法交联壳聚糖/活性炭复合膜的制备及其吸附性能

采用微波辐射技术制备了交联壳聚糖/活性炭复合膜(CCTS),通过红外光谱和扫描电镜对产物结构进行了表征,研究了该吸附剂的主要性能、吸附机理和对铜离子的吸附条件。结果表明,CCTS复合膜表面粗糙,比表面积较大。壳聚糖的氨基参与了交联反应,CCTS对铜离子的吸附是CCTS的—NH2和—OH与Cu2+发生了配位反应,其吸附符合Langmuir等温方程,属于单分子层吸附。CCTS对铜离子的吸附条件是25℃,pH值为5.5,在50mL浓度为200mg/L Cu2+溶液中,投加0.05g吸附剂,吸附6h,吸附量为117.4mg/g。与水浴法制备的吸附剂相比,该吸附剂的吸附量大大提高,且操作方法简单,工艺条件易于控制。     

Heat treatment of nanometer anatase powder and its photocatalytic activity for degradation of acid red B dye under visible light irradiation

The phase transformation of nanometer TiO₂ powder from anatase to rutile was realized by heat treatment, and a new nanometer TiO₂ photocatalyst that could be excited by visible light was obtained. The heat-treated TiO₂ powder at different transition stage was characterized by powder x-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The test of photocatalytic activity of the heat-treated TiO₂ powder was carried out by the photocatalytic degradation of acid red B dye in aqueous solution under visible light irradiation. The nanometer anatase TiO₂ heat-treated at 500°C for 30 min exhibited much higher activity than those of pure anatase and mechanically mixed (anatase and rutile) TiO₂. The remarkable improvement of photocatalytic activity was mainly illustrated by the special interphase between rutile and anatase, which not only restrains the recombination of photogenerated electron-hole pairs but also reduces the adsorbability of nanometer anatase TiO₂ powder to a certain extent. More significantly, the anticipatory interlaced energy level of heat-treated TiO₂ particles is convenient for capturing photons of low energy and thus achieves the intention of using visible light. The text was submitted by the authors in English.     

Synthesis of graphitic carbon particle chains at low temperatures under microwave irradiation

Chains of graphitic carbon particles were formed by microwave irradiation of polyethylene glycol at temperatures between 160 and 220 °C for 40 min, in the absence of a catalyst. Chains were comprised of individual particles ranging in size from 340 to 620 nm; particle size increased with synthesis temperature. The D/G ratio measured by Raman spectroscopy was 0.91, indicative of a mixture of amorphous and graphitic material. SEM, TEM and TGA measurements confirmed this. Our experiments show that the chains are an intermediate product, which when heated further under hydrothermal conditions, produce MWNTs.     

Relationship of mechanical properties and temperature of carbon fiber-reinforced plastics under microwave irradiation

One of the problems with the use of carbon fiber-reinforced plastics (CFRP) is the difficulty of recycling or disposing of them. Hence, it is necessary to find processes to treat CFRP wastes faster and more effectively. Because carbon fibers are good microwave absorbers, there is significant potential for the use of microwave irradiation for the processing of CFRP wastes. In this study, the relationship of mechanical properties and radiation temperature during microwave irradiation of unidirectional and cloth-type CFRP were studied. Experimental results indicate that microwave irradiation degrades CFRP’s mechanical properties by breaking down the bond between the polymer matrix and the carbon fibers.     

Fracture behavior of wasted activated carbon powder composites

At the Waterworks Bureau (Tokyo Metropolitan Government), activated carbon has been used for filtering water. After being used for the filtering process, it is normally disposed or burned for thermal recycling. However, CO₂ emissions occur during the thermal recycling. This work focuses on the identification of mechanical behavior of recycled wasted activated carbon (WAC) in order to elaborate smart materials having mechanical–electrical functions. Acoustic emission technique (AE) was used intensively as characterization support in which sensors were attached to detect microdamage during bending tests. At first, the resonant frequencies of the specimens were measured using the through-transmission test. The resonant frequencies of the specimens containing low weight fractions of WAC powder were less in comparison to the frequencies of the specimens with higher volume fraction. The frequency analysis was carried out with the projected wavelet transform on the signals detected during bending tests. Obtained data showed that, typically, the first major peaks showed the resonant frequency of the sensors, while the second major peaks exhibited signals indicative of resin cracking. The surfaces of the fractured specimens were analyzed by optical microscopy in order to visualize the crack formation and propagation on the activated carbon composite under flexural stresses. Consequently, fractographic and AE analyses provide better understanding of the failure mechanisms involved.     

以核桃壳为碳源微波加热制备介孔活性炭

以核桃壳为碳源,微波辐射法制备了介孔活性炭。用XRD、SEM和低温氮气吸脱附对所制备活性炭进行了物性分析;用恒流充放电、循环伏安和交流阻抗等方法分析了微波功率、辐射时间对活性炭电容性能的影响。确定活性炭的最佳制备工艺为微波功率480W,辐射时间9min。制得的活性炭平均孔径为4.44nm,介孔率为78.51%,比表面积达1530m2/g,为不规则、疏松多孔的无定形结构。当充放电电流为100mA/g时,比电容为226.4F/g,循环1 000次后比电容为192.2F/g,每次循环电容衰减仅为0.015%。     

Effect of Ag loading on activated carbon doped ZnO for bisphenol A degradation under visible light

Silver modified activated carbon doped zinc oxide (Ag/AC-ZnO) was synthesized via a calcination-electroless deposition route. The samples were characterized by X-ray powder diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the Ag/AC-ZnO was evaluated for bisphenol A degradation in the presence of H₂O₂ under visible light irradiation. The archived results showed that the photocatalytic activity of the Ag/AC-ZnO was higher than that of AC-ZnO and pure ZnO. The cytotoxicity of the bisphenol A after photocatalysis under visible light irradiation was tested using L929 mouse fibroblast cells and the obtained results indicated that the treated bisphenol A solution exhibited no cytotoxicity against normal cells.     

活性碳纤维负载铁酞菁催化降解4-硝基苯酚

合成了高活性的四磺酸基铁酞菁(FePcS),通过酰氯化反应将FePcS负载到乙二胺改性的活性碳纤维(ACF)上,制备新型催化活性碳纤维(ACF-FePcS),并通过紫外漫反射光谱和X射线光电子能谱对其结构进行表征。以H2O2为氧化剂,研究了ACF-FePcS对4-硝基苯酚(4-NP)的催化降解性能。结果表明,在室温25℃,反应4h后,4-NP的去除率达90%以上,且在较广的pH和温度范围内都有较高活性。因此,ACF-FePcS具有"富集-原位催化降解"的特点,在去除有机污染物方面具有较好的应用前景。     

基于微波辐照合成类石墨烯氮化碳的研究进展

类石墨烯氮化碳具有与石墨烯非常相似的结构特征,已在光催化、润滑等领域表现出极优越的性能,成为二维纳米功能材料领域的新热点。本文重点介绍了基于微波辐照合成类石墨烯氮化碳的研究进展,并通过与氧化刻蚀、液相超声剥离、热聚合等传统合成方法的比较,分析了微波合成在制备效率、效果上的优势;并指出采用高功率微波设备和石墨粉、短切碳纤维等对微波具有强烈响应的微波吸收剂,通过增强能量传递与吸收效率,强化微波电磁场环境下合成反应的非稳态程度,有助于提高合成效率、效果,并获取得到特殊形态、结构的新产物。     

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.     

Influence of precursor preparation on the synthesis of WC under microwave irradiation

The role of precursor preparation in the microwave synthesis of tungsten carbide (WC) from tungsten, hydrogen peroxide (H₂O₂) and carbon is investigated. In this work, the influence of the conditions of precursor preparation on the synthesis reaction of WC is examined, with focus on evaporation temperature and concentration of the H₂O₂ solution. Precursors following different preparation conditions are compared in terms of phase and morphology. The evaporation step is shown to control the condition of the precursor in terms of its crystallinity and degree of hydration. These consequently affect the phase composition of the product. Slow evaporation, taking 8–12 h at temperatures below 100 °C (slow), led to crystalline flakes of hydrated tungsten oxide in the precursor. Vigorous evaporation, taking 10 min at a rapid heating rate (fast), resulted in amorphous tungsten oxide. When mixed intimately with carbon and microwaved, the latter precursor was more effectively carburised.     

Regeneration of hexamminecobalt(II) catalyzed by activated carbon treated with KOH solutions

The combined elimination of NO and SO(2) can be realized by hexamminecobalt(II) solution which is formed by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexamminecobalt(II), Co(NH(3))(6)(2+), so that NO removal efficiency can be maintained at a high level for a long time. In this study, KOH solution has been explored to modify coconut activated carbon to meliorate its catalytic performance in the reduction of hexamminecobalt(III), Co(NH(3))(6)(3+). The experiments have been performed in a batch stirred cell to investigate the effects of KOH concentration, impregnation duration, activation temperature and activation duration on the performance of activated carbon. The results show that the best KOH concentration for the improvement of activated carbon is 0.5 mol l(-1). The optimal impregnation duration is 9h. High temperature is favorable to ameliorating the catalytic performance of activated carbon. The optimum activation duration is 4h.     

Morphological syntheses of ZnO nanostructures under microwave irradiation

ZnO nanostructures with flower-, rod-, and flake-like morphologies have been controllably synthesized using Zn(acac)₂·H₂O (acac = acetylacetonate) as a single-source precursor through a facile and fast microwave-assisted method. The morphologies of ZnO nanostructures can be systematically adjusted by using various surfactants. The ZnO products are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The results show that all ZnO nanostructures are of single-crystalline nature with hexagonal wurtzite structure. The possible formation mechanism for these ZnO nanostructures is proposed and their photoluminescence properties are also investigated.     

Synthesis of nanosize BPO4 under microwave irradiation

Nanosize BPO₄ was synthesized using H₃BO₃ and H₃PO₄ (85%) as raw materials under microwave irradiation. This reaction was performed at powers lower than 640 W and irradiation time ranging from 2.5 min to 5 min, which were only a fraction of the time required for conventional synthetic procedures. The structure of the as-prepared BPO₄ is analogous to that of a high cristobalite. The particle sizes of the samples irradiated at 640 and 400 W range from 40 nm to 90 nm and 30 nm to 60 nm, respectively. The effects of different conditions on the experimental outcome are also discussed.     

Fabrication of mesoporous carbonated hydroxyapatite/carbon nanotube composite coatings by microwave irradiation method

Carbonated hydroxyapatite/carbon nanotube composite coatings (MHCs) with mesoporous structures were fabricated by electrophoretic deposition of nacre powders and carbon nanotubes on Ti6Al4V substrates followed by treatment with a phosphate buffer solution (PBS) by microwave irradiation method. The carbon nanotubes are dispersed uniformly on the whole MHCs. The conversion mechanism of the crack-free nacre/carbonate nanotube composite coatings (NCCs) to MHCs is a dissolution-precipitation reaction. After soaking in PBS, calcium ions are released from the nacre powders and react with phosphate ions to form carbonated hydroxyapatite nanoparticles. These nanoparticles aggregate to form mesopores with the pore sizes of ~ 3.9 nm among them. Simulated body fluid (SBF) immersion tests reveal that MHCs have a good in vitro bioactivity.     

Effect of zirconia on the formation of calcium phosphate bioceramics under microwave irradiation

Bi-phasic calcium phosphate (BCP) bioceramics containing hydroxyapatite (HA) and tri-calcium phosphate (TCP) phases have recently attracted attention as an ideal bone graft substitute due to their controlled resorption in the body fluid upon implantation. In this study, the HA and BCP phases were prepared by in situ method, using natural goniopora under microwave irradiation. Fourier-transform infrared (FT-IR) and powder X-ray diffraction (XRD) methods were employed to investigate proof of HA and BCP formations. XRD results show that the major characteristic peaks of HA appear in the regions of approximately 26°, 28°, 29°, 30–35°, 39°, 46°, 49° and 50° (2θ). FT-IR results indicate that there are no occurrences of impurities during HA and BCP formations. Reinforcement of zirconia in the in situ formation of HA leads to a more resorbable phase of β-TCP since the influence of zirconia induces faster decomposition of HA, as indicated by differential thermal (DT) analysis. The in vitro physiological stability of prepared materials was performed in phosphate-buffered saline (PBS) of pH 7.4 at 37 °C in a thermostatic water bath, and the results indicate that the resorbable nature of BCP lies in between the resorption levels of HA and TCP. Solubility of the BCP can be controlled by the addition of zirconia corresponding to clinical applications.