Magnetic zeolites: a new adsorbent for removal of metallic contaminants from water

In this work the adsorption features of Na Y zeolite with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as an adsorbent for metallic contaminants in water and subsequently removed from the medium by a simple magnetic process. The zeolites:iron oxide magnetic composites, were prepared by using Na Y with weight ratio of 3:1 and were characterized by powder X-ray diffraction (XRD), magnetization measurements, chemical analyses, N(2) adsorption isotherms and M?ssbauer spectroscopy. Nitrogen adsorption isotherms showed that the surface area decreased from 505 m(2)g(-1) for the pure Na Y to 353 m(2)g(-1) for the Na Y:Fe oxide 3:1 composite. The adsorption isotherms of metal ions Cr(3+), Cu(2+) and Zn(2+) from aqueous solution onto the composites also showed that the presence of iron oxide does not affect the adsorption capacity.     

Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters

Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, <50 nm) incorporated in amine rich cryogels (Alu-cryo), (b) molecular imprinted polymers (<38 μm) in polyacrylamide cryogels (MIP-cryo) and (c) thiol functionalised cryogels (SH-cryo) were evaluated regarding material characteristics and arsenic removal in batch test and continuous mode. Results revealed that a composite design with particles incorporated in cryogels was a successful means for applying small particles (nano- and micro- scale) in water solutions with maintained adsorption capacity and kinetics. Low capacity was obtained from SH-cryo and this adsorbent was hence excluded from the study. The adsorption capacities for the composites were 20.3 ± 0.8 mg/g adsorbent (Alu-cryo) and 7.9 ± 0.7 mg/g adsorbent (MIP-cryo) respectively. From SEM images it was seen that particles were homogeneously distributed in Alu-cryo and heterogeneously distributed in MIP-cryo. The particle incorporation increased the mechanical stability and the polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity.     

特定结构固定床吸附除湿实验研究

本文以13X分子筛作为吸附剂,对特定结构的固定床进行了吸附除湿性能的实验研究.通过对固定床内部3个测点温度和相对湿度的测量,分析了再生过程和吸附过程中,固定床内部各测点吸附剂对水分的解析和吸附情况.结果表明,将温度为25℃、相对湿度为60％、风量为2500 m3/h的空气加热至60℃并送入床内进行再生,在整个再生过程中,位于固定床后段的吸附剂平均单位时间解析量为10.6 g/kg干空气,是前段床体吸附剂解析量的1.93倍,是中间段床体吸附剂解析量的2.23倍.对于温度为23℃、相对湿度为90％、风量为1500 m3/h的空气,在吸附平衡状态下,固定床后段的吸附剂单位时间除湿量为9.51 g/kg干空气,是前段床体吸附剂除湿量的2.87倍,是中间段床体吸附剂除湿量的3.51倍,位于固定床后段的吸附剂除湿效果更为显著.     

Enhanced mitigation of para-chlorophenol using stratified activated carbon adsorption columns

The adsorptive removal of toxic para-chlorophenol using activated carbon adsorption columns is a proven effective engineering process. This paper examined the possibility to stratify an adsorbent bed into layers, in order to enhance the adsorption process performance in terms of increased column service time and adsorbent bed saturation. Four different types of fixed-bed adsorption columns are used and compared under the same operating conditions, but with the variation of column geometry and activated carbon particle size stratification. The Type 3 column - a cylindrical column with particle stratification packing, is found to be the most efficient choice, as the extent of column service time and adsorbent bed saturation are the largest. This could eventually decrease the frequency of adsorbent replacement/regeneration and hence reduce the operating cost of the fixed-bed adsorption process. The Homogeneous Surface Diffusion Model (HSDM) was applied successfully to describe the dynamic adsorption of para-chlorophenol onto Filtrasorb 400 (F400) activated carbon in different types of columns. The Redlich-Peterson isotherm model equation, an experimentally derived external mass transfer correlation and a constant surface diffusivity are used in the HSDM. The optimised surface diffusivity of para-chlorophenol is found to be 1.20E-8 cm²/s, which is in good agreement with other phenolics/F400 carbon diffusing systems in literature.     

Bifunctional resin-ZVI composites for effective removal of arsenite through simultaneous adsorption and oxidation

Bifunctional resin-supported nanosized zero-valent iron (N–S-ZVI) composite was developed by combining the oxidation properties of nZVI/O₂ with adsorption features of iron oxides and anion-exchange resin N–S. In batch culture experiments, N–S and the N–S-ZVI composite were examined for As(III) and As(V). The results reveal that ZVI in the composite played a key role in enhancing As(III) removal. The N–S-ZVI composites could oxidize more toxic As(III) to less toxic As(V) with high efficiency under ambient conditions without the need of noble metals. At the same time, the oxidized As(V) could be effectively removed by adsorption onto the surface of composites. The mechanisms for the oxidation of As(III) to As(V) and the simultaneous removal of As(V) are proposed. In order to investigate the potential performance of N–S-ZVI in practical use, the effects of solution pH and coexisting anions on arsenite removal and on fixed-bed column treatment of simulated waters were studied. All the results indicated that the bifunctional composites have a great potential for As(III) removal from contaminated waters.     

太阳能固体吸附式转轮制冷机性能分析

针对活性炭纤维-乙醇太阳能固体吸附式转轮制冷系统,采用沿吸附床周向的一维均匀压力场数学模型,对转轮吸附床温度场进行了静态模拟计算;从吸附床的内、外部特性参数出发,全面而系统地分析了这些参数的改变对系统性能、平衡脱附率以及吸附量的影响。结果表明,在转轮吸附床的内部参数中,转轮吸附床的转速、吸附剂的填充密度对系统的性能有着较大的影响;在其外部参数中,冷却气体入口流速、蒸发温度等因素对系统影响比较大。     

Reactive Red 120 dye removal from aqueous solution by adsorption on nano-alumina

The adsorption of Reactive Red 120 dye from aqueous solutions by using nano-alumina has been investigated. The batch adsorption studies were carried out to determine the impact of pH, contact time, concentration of dye, and the adsorbent dose on adsorption process. The maximum adsorption efficiency was observed at pH 3. However with an increase of the adsorbent dose, the dye removal efficiency increased, while the amount of dye adsorbed per unit mass (mg/g) decreased. A pseudo-second-order model best described the adsorption kinetics of the specified dye onto nano-alumina. In this case the Langmuir isotherm model appeared to be most suitable. Findings of the present study reveal that nano-alumina can be an effective adsorbent for the removal of Reactive Red 120 from aqueous solutions.     

Removal of organic dyes by magnetic alginate beads

This study deals with the development of a clean and safe process for water pollution remediation. We have synthesized a magnetic adsorbent in order to develop a solid-phase extraction process assisted by a magnetic field. To follow an 'ecoconception' approach, magnetic beads containing magnetic nanoparticles and activated carbon are prepared with a biopolymer extracted from algae, sodium alginate. The use of renewable bioresources of low cost and those disposable in large amount allows the development of a product with a low impact on the environment. The adsorption properties of activated carbon and magnetic properties of iron oxide nanoparticles are combined to produce an interesting magnetic composite. Synthesis and characterization of the magnetic beads have been reported. Their adsorption capacity was investigated by measuring the removal of two dyes (methylene blue and methyl orange) of different charges from aqueous solutions. The efficiency of the beads has been compared with that of non-encapsulated activated carbon. The effects of initial dye concentration, pH and calcium content of the beads have been studied. Adsorption kinetics experiments have been carried out and the data have been well fitted by a pseudo-second-order equation.     

Defluoridation of wastewaters using waste carbon slurry

Adsorption of fluoride on waste carbon slurry was investigated. Waste carbon slurry was obtained from fuel oil based generators of a fertilizer industry. The work involves batch experiments to investigate the effects of contact time, pH, temperature and adsorbent dose on the extent of adsorption by carbon slurry. The contact time and pH for maximum fluoride uptake were found 1h and 7.58, respectively. Maximum adsorption capacity (4.861 mg g(-1)) of fluoride on carbon slurry was observed at 15.00 mg L(-1) initial fluoride concentration using 1.0 g L(-1) adsorbent dose. Among four applied models, the experimental isotherm data were found to follow Langmuir equation more closely. Thermodynamically, adsorption was found endothermic with values 7.348 kJ mol(-1), -25.410 kJ mol(-1) and 0.109 kJ mol(-1)K(-1) for enthalpy, free energy and entropy, respectively showing the feasibility of adsorption process. From kinetic analysis, the adsorption was found to follow second-order mechanism with rate constant 49.637 gm g(-1)min(-1). The rate-controlling step of the adsorption was found pore diffusion controlled. In order to investigate the potential of this adsorbent on industrial scale, column and desorption experiments were carried out. The breakthrough capacity of column was calculated 4.155 mg g(-1) with at a flow rate of 1.5 mL min(-1). The proposed adsorbent has been used to remove fluoride from groundwater and wastewater. Desorption has been achieved under alkaline conditions (pH 11.6) from exhausted carbon slurry. The performance of carbon slurry was compared with many other reported adsorbent for fluoride removal and it was observed that proposed adsorbent is effective in terms of performance and cost especially.     

多壁碳纳米管/氧化亚铜的制备及其对N-甲酰吗啉的光催化性能

采用液相还原法制备多壁碳纳米管/氧化亚铜(MWCNTs/Cu2O)复合微球。利用傅立叶变换红外光谱仪(IR)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)等对样品进行官能团分析、物相分析和形貌观察,结果表明:多壁碳纳米管以纵横穿插方式与氧化亚铜形成复合微球。对比氧化亚铜和多壁碳纳米管/氧化亚铜对目标有机物N-甲酰吗啉的光催化活性,结果表明:多壁碳纳米管/氧化亚铜复合催化剂的催化效果明显优于氧化亚铜。     

Preparation and evaluation of a novel Fe-Mn binary oxide adsorbent for effective arsenite removal

Arsenite (As(III)) is more toxic and more difficult to remove from water than arsenate (As(V)). As there is no simple treatment for the efficient removal of As(III), an oxidation step is always necessary to achieve higher removal. However, this leads to a complicated operation and is not cost-effective. To overcome these disadvantage, a novel Fe-Mn binary oxide material which combined the oxidation property of manganese dioxide and the high adsorption features to As(V) of iron oxides, were developed from low cost materials using a simultaneous oxidation and coprecipitation method. The adsorbent was characterized by BET surface areas measurement, powder XRD, SEM, and XPS. The results showed that prepared Fe-Mn binary oxide with a high surface area (265 m2 g(-1)) was amorphous. Iron and manganese existed mainly in the oxidation state +III and IV, respectively. Laboratory experiments were carried out to investigate adsorption kinetics, adsorption capacity of the adsorbent and the effect of solution pH values on arsenic removal. Batch experimental results showed that the adsorbent could completely oxidize As(III) to As(V) and was effective for both As(V) and As(III) removal, particularly the As(III). The maximal adsorption capacities of As(V) and As(III) were 0.93 mmol g(-1) and 1.77 mmol g(-1), respectively. The results compare favorably with those obtained using other adsorbent. The effects of anions such as SO4(2-), PO4(3-), SiO3(2-), CO3(2-) and humic acid (HA), which possibly exist in natural water, on As(III) removal were also investigated. The results indicated that phosphate was the greatest competitor with arsenic for adsorptive sites on the adsorbent. The presence of sulfate and HA had no significant effect on arsenic removal. The high uptake capability of the Fe-Mn binary oxide makes it potentially attractive adsorbent for the removal of As(III) from aqueous solution.     

聚多巴胺 / 膨润土吸附剂的制备及对铬（Ⅵ）的吸附性能研究

本文以膨润土为基体,盐酸多巴胺为原料,采用聚合物改性技术制备聚多巴胺-膨润土吸附剂(PDA/SDS-BT)。通过红外光谱仪(FT-IR),X射线衍射仪(XRD)、透射电镜(TEM)对制备的吸附剂进行了结构表征,并考察了PH、吸附剂投加量、吸附时间和吸附温度对吸附性能的影响。结果表明:适当提高温度有利于吸附,PH=3,反应温度313K,达到吸附平衡时,吸附量可达81.10mg/g。     

Adsorption of basic dyes on granular activated carbon and natural zeolite

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.     

Experimental investigation of the effect of carbon nanotubes and carbon fibres on the behaviour of plain cement composite beams

In this article, the behaviour of reinforced cement composite beams with multi-walled carbon nanotubes (MWCNTs) and carbon fibres (CFs) is investigated. The percentage of CFs was fixed at 0.25 wt% of cement, while the percentage of MWCNTs was varied from 0.25, 0.5, 0.75, 1 wt% of cement. Dispersion of both MWCNTs and CFs was carried out using ultrasonic energy. Composite beams were tested under flexure in order to evaluate their mechanical properties such as flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. The present work also investigates the optimum percentage of fibres that gives the best results both in terms of enhanced properties and economy.     

Adsorption studies using gas-liquid chromatography—III. Experimental factors influencing adsorption

Gas-liquid chromatography with a flame ionization detector system using the direct injection of aqueous solutions was used to monitor the adsorption of selected organic compounds in water onto activated carbon.The effects of changes in experimental factors influencing adsorption were investigated using both batch (agitated flask) and column (flow through packed bed) systems; solution pH and concentration, carbon particle size, carbon bed depth and flow rate were all studied.The direct injection of aqueous solutions was observed to facilitate the direct analysis of pollutants in water, obviating the need for preliminary concentration or extraction steps.     

Magnetic powder MnO-Fe2O3 composite--a novel material for the removal of azo-dye from water

Fine powder adsorbents or catalysts often show better adsorptive or catalytic properties, but they encounter the difficulties of separation and recovery in application. In this study, four inexpensive magnetic powder MnO-Fe2O3 composites used as adsorbent-catalyst materials were prepared and characterized. These materials could be recovered efficiently by a magnetic separation method. Their adsorptive properties for the removal of an azo-dye, acid red B (ARB), from water and the regeneration of adsorbents containing ARB by catalytic combustion was studied. These powder adsorbents showed excellent adsorption towards ARB under acidic conditions. A very fast adsorption rate was observed and could be well described by a pseudo-second-order kinetics model. The adsorption capacity increased with increasing Fe content and surface area of the adsorbent, and the highest adsorption capacity of 105.3 mg/g was obtained at pH 3.5. The adsorption was not affected by the presence of Cl-, but was significantly affected by SO4(2-). The adsorbent containing ARB can be regenerated by catalytic combustion of adsorbed ARB at 400 degrees C in air. Laboratory experiments demonstrated that this material is reusable.     

Desorption of dye from activated carbon beds: effects of temperature, pH, and alcohol.

The adsorption isotherms of yellow and red dye solutions onto granular activated carbon at varying solution pHs (2-8). temperatures (15-50 degrees C), and alcohol concentrations (0-20%) were experimentally determined by batch tests and the Tóth model was found to best fit the adsorption isotherm data for varying solution pHs. temperatures, and alcohol concentrations. The maximum adsorption capacity was found to decrease with increasing solution pH and alcohol concentration and could be predicted by the correlation equations obtained in this study. A correlation equation was also obtained to account for the effects of solution temperature on the adsorption equilibrium constant. The 25 degrees C water was found to be a very poor regenerant for the carbon bed presaturated with the yellow dye compared with 20% alcohol solution. A simple equation was derived, based on non-linear wave propagation theory, to predict the desorption curves of activated carbon bed. Given presaturation concentration, bed density and void fraction, and adsorption isotherm, the wave propagation theory predicted the desorption curves quite satisfactorily.     

The characterization of metal oxide - Mangifera indica L. matrix and its potential as scavenger of heavy metal pollutant

Widespread pollution by heavy metals requires an efficient, cheap and eco-friendly removal technique. This paper reports the use of discarded leaves of Mangifera indica L. modified to enhance their adsorption efficiency in the removal of heavy metal pollutant. The adsorbent was then characterized through X-ray diffraction study, Fourier transform infrared spectroscopy and application to mathematical models. The adsorption process was found to fit the Langmuir’s isotherm model and pseudo-first-order kinetic model. The intra-particle diffusion model was found to be the rate limiting step for the adsorption process. Its rapid kinetics, high hydrophilicity, and easy regenerability with mild mineral acid (like 0.005 M HCl) make this adsorbent suitable for the fixed bed column technique.     

Adsorption studies using gas-liquid chromatography—II. Competitive adsorption

Gas-liquid chromatography with a flame ionization detector system using the direct injection of aqueous solutions was used to monitor the adsorption of selected organic compounds dissolved in water onto activated carbon.The effects of competitive adsorption in batch (agitated flask) and column (flow through packed bed) systems were investigated. The effects became more pronounced with increase in the number of solutes in solution. This emphasises the importance of the competitive adsorption effect on the performance of an activated carbon unit in water or wastewater treatment.     

Modeling a solar-powered double bed novel composite adsorbent (silica activated carbon/CaCl2)-water adsorption chiller

During the past few decades, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Adsorption cooling system is one of the technologies which could be powered by renewable energy. This study aims to improve the performance of a solar-powered adsorption chiller by applying a novel composite adsorbent, a mixture of activated carbon, silica gel and calcium chloride. Modeling is established to investigate the cooling performance of a composite adsorbent based adsorption chiller driven by flat-type solar collectors with three different configurations of glaze: (1) single glazed cover; (2) double glazed cover and (3) transparent insulation material (TIM) cover. The simulation results show that the coefficient of performance (COP) and the specific cooling power (SCP) of the adsorption chiller depend hugely on the solar collector temperature. It is found that a double glazed cover shows the best cooling performance and 30 m² is the most optimized solar collector area. Two to three hours of pre-heating time is required to initiate the desorption process of the adsorber in a day of operation. This newly developed silica activated carbon/CaCl₂ composite material as adsorbent used in the adsorption chiller could achieve a high mean COP_sc of 0.48. Its satisfactory performance suggests that this novel composite material has a potential to be used in the adsorption chiller system even if it is powered by unstable solar energy.