Biosorption of aluminum on Pseudomonas aeruginosa loaded on Chromosorb 106 prior to its graphite furnace atomic absorption spectrometric determination

A biosorption procedure for separation-enrichment of aluminum in environmental samples has been presented in this work. Pseudomonas aeruginosa loaded on Chromosorb 106 has been used as biosorbent for that purpose. P. aeruginosa is a gram-negative, aerobic rod. The influences of pH of the aqueous solution, eluent type, eluent volume, sample volume, etc. were examined on the quantitative recovery of aluminum in P. aeruginosa loaded on Chromosorb 106. The effects of concomitant ions on the recoveries of aluminum were also investigated. The detection limit based on 3 sigma for aluminum is 30 ng L(-1). Three certified reference materials (LGC 6010 Hard Drinking Water, NIST-SRM 1568a Rice Flour and NRCC-DORM-2 Dogfish Muscle) were analyzed for the validation of the presented procedure. The proposed procedure was applied to the determination of aluminum in environmental samples including natural water and food samples. The concentration of aluminum in real samples was found at ppb level.     

Investigation on the ballistic impact behavior of various alloys against 7.62 mm armor piercing projectile

In this study, impact behavior of the aluminum alloys of 7075 and 5083 and the high-strength low-alloy steel, AISI 4140 was investigated under 7.62 mm armor piercing (AP) projectile experimentally. Various heat treatments were applied to the alloys AISI 4140 and 7075 to see the effect of hardness and strength on their ballistic behaviors. Experimental results showed that among the investigated materials, the best ballistic performance was attained with the alloy, 7075-T651 which maintained the ballistic protection with the areal density 85 kg/m².     

Flame atomic absorption spectrometric determination of trace amounts of heavy metal ions after solid phase extraction using modified sodium dodecyl sulfate coated on alumina

A sensitive and selective solid phase extraction procedure for the determination of traces of Cu(II), Zn(II), Pb(II) and Fe(III) has been developed. An alumina-sodium dodecyl sulfate (SDS) coated on with meso-phenyl bis(indolyl) methane (MPBIM) was used for preconcentration and determination of Cu(II), Zn(II), Pb(II) and Fe(III) ions by flame atomic absorption spectrometry. The analyte ions were adsorbed quantitatively on adsorbent due to their complexation with MPBIM. Adsorbed metals were quantitatively eluted using 6 mL of 4 mol L⁻¹ nitric acid. The effects of parameters such as pH, amount of alumina, amount of MBITP, flow rate, type and concentration of eluting agent were examined. The effects of interfering ions on the separation-preconcentration of analytes were also investigated. The relative standard deviation of the method was found to be less than 3.0%. The presented procedure was successfully applied for determination of analytes in real samples.     

Gadolinium hydroxide coprecipitation system for the separation-preconcentration of some heavy metals

A simple and new procedure for the determination of trace amounts of lead(II), cobalt(II), manganese(II) and copper(II) is described, that combines atomic absorption spectrometry-gadolinium hydroxide coprecipitation. One milliliter of 1% gadolinium(III) solution was added to each sample; the pH was then adjusted to 11 in order to collect trace heavy metals on gadolinium(III) hydroxide. The precipitate was separated by centrifugation and dissolved in 1 mL of 1 mol L(-1) HNO3. The influences of analytical parameters including amount of gadolinium(III), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of concomitant ions were also examined. The recoveries of the analyte ions were greater than 95. The detection limits for the analyte elements based on 3 sigma (n=20) were in the range of 0.52-12.0 microg L(-1). The method was applied to the determination of analytes in real samples and good results were obtained (relative standard deviations <10%, recoveries >95%).     

Chromium (III) removal by weak acid exchanger Amberlite IRC-50 (Na)

Chromium (III) sorption on a weakly macroporous cation exchanger Amberlite IRC-50 (Na) is studied as a function of time and temperature. The rate constant values for chromium (III) sorption are calculated both for film and particle diffusion processes. The temperature is found to have a positive effect on both the diffusional processes. The high values of energy of activation confirm the particle diffusional nature of the process. The pH changes in the system show a competition between the Cr(OH)(2+) and H(+) ions for the exchange sites of the adsorbent. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters (DeltaH degrees , DeltaS degrees and DeltaG degrees) from chromium (III) exchange on the resin are calculated.     

Evaluation of the performance of calix[8]arene derivatives as liquid phase extraction material for the removal of azo dyes

This paper presents a study on the removal of azo dyes (Reactive Black 5, Trapaeolin 000, Methyl Orange and Direct Violet 51) with calix[n]arene derivatives from aqueous solution into the organic phase in order to explore the potential use of calixarenes as low-cost efficient extractants for wastewater dye removal. The carboxylic acid derivative of calix[8]arene shows highest affinity towards the azo dyes. The influence of NaCl (present in the solution) on extraction process was also studied. The extent of the dye removal increased with the addition of NaCl. The proposed extraction mechanism involves several kinds of interactions: electrostatic repulsion between carboxylic acid groups of calix[8]arenes and sulfonate groups of azo dyes, hydrogen bonding and formation of an inclusion complex due to three dimensional cavity type calix[n]arene molecules through host-guest interactions.     

Sorption characteristics of Cu(II) ions onto silica gel-immobilized calix[4]arene polymer in aqueous solutions: batch and column studies

In the present study, Cu(II) removal from aqueous solutions by sorption was investigated. Aminopropyl silica gel-immobilized calix[4]arene polymer (APSIC[4]P) was used in sorption as sorbent. During the experimental part of this study, the effect of parameters, such as pH, initial Cu(II) concentration, temperature on Cu(II) removal was observed. In addition, sorption isotherm studies and column studies were made. Maximum Cu(II) removal was obtained at pH 6 and 25 degrees C. In the isotherm studies, Langmuir and Freundlich isotherm models were applied and it was determined that the experimental data confirmed to Langmuir isotherm model. Batch sorption capacity (q0) was calculated as 5.08 mg/g. The capacity value for column study was obtained by graphical integration as 1.14 mg/g. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristics parameters of the column useful for process design.     

Role of Composite Phase Change Material on the Thermal Performance of a Latent Heat Storage System: Experimental Investigation

复合相变材料对潜热储能系统中热性能作用的实验研究

Jasim Abdulateef¹, Ahmed F. Hasan^2*,Mustafa S. Mahdi²

（1. 迪亚拉大学 机械工程系,巴古拜 32001,伊拉克;2.迪亚拉大学 化学工程系,巴古拜 32001,伊拉克）

摘要：

石蜡是可用于潜热储能系统单元（LHSU）的理想的相变材料（PCM）。这种潜热储能单元的使用因相变材料导热性差而受到限制。本文采用铝和相变材料制成的金属泡沫生产复合相变材料,以此作为相变材料-潜热储能单元中的导热材料,并使用水作为传热流体（HTF）。通过实验,评估了使用纯相变材料和复合相变材料的潜热储能单元的传热特性。研究包括熔化和凝固过程中相变材料的时变可视化。此外,热存储室内放置一个热电偶网络,记录每个过程的温度分布。结果表明,复合相变材料-潜热储能单元在熔化和凝固过程中均表现出较好的性能。由于金属泡沫的作用,复合相变材料-潜热储能单元的熔化时间比简单的相变材料-潜热储能单元快83%左右,凝固时间减少85%左右。

关键词：相变材料;金属泡沫;潜热;复合相变材料

     

Nickel inhibition of calcium precipitation by ureolytic mixed microorganisms under batch conditions

The respirometric assessment of the inhibitory impact of Ni(II) on substrate utilization and microbial carbonate precipitation (MCP) by ureolytic mixed microorganisms was investigated with a glucose containing mineral medium under batch conditions over an incubation period of 134 h. The IC₂₅ was determined as 224 mg Ni(II) L⁻¹ from the BOD values of samples. The interpretation of kinetic data showed that the substrate removal rate fitted a zero-order at the beginning of the incubation period and first-order during the last period, for a range of Ni(II) concentrations between 0 and 512 mg L⁻¹. Increasing Ni(II) concentrations from 0 to 512 mg L⁻¹ reduced the substrate degradation rate constant from 10.8 to 5.3 mg L⁻¹ h⁻¹ for zero-order rate constant (k₀), and from 0.015 to 0.002 h⁻¹ for first-order rate constant (k₁). The zero- and first-order reaction rates during incubation period were equalized to the reaction rate of the Monod equation in order to determine the kinetic constants, half saturation concentration (K_S) and maximum substrate removal rate (R_max). BOD removal rate was inhibited accordingly to mixed inhibition model with increasing Ni(II) concentrations during the calcification process. Also, the inhibition of calcium precipitation was observed at a higher Ni(II) concentration because of inhibition of ammonium production in these samples.     

Heterogeneous photo-Fenton oxidation of reactive azo dye solutions using iron exchanged zeolite as a catalyst

The heterogeneous photo-Fenton-type oxidation of reactive azo dye solutions has been investigated in a quartz batch reactor using artificial UVA as a light source. Fe-exchanged zeolite has been used as a heterogeneous catalyst in the process. The effect of various process variables on decolorization performance of the process was evaluated by examining temperature, pH, H₂O₂ dosage, catalyst loading, initial dye concentration and light intensity. The optimal operational parameters were found as follows: 35 °C, pH as solution pH 5.2, 15 mmol H₂O₂ dosage, 1 g/L catalyst loading. Stability and reuse of the catalyst were also tested. Mineralization and comparison with homogenous photo-Fenton process were evaluated by analyzing color removal and total organic carbon (TOC) values.