Selective water sorbents for multiple application, 6. Freshwater production from the atmosphere

In this communication we consider an application of new selective water sorbents for freshwater production from the atmosphere. We present a general scheme of water production and discuss its efficiency in different climatic areas. The results of our lab-scale tests have demonstrated the feasibility of this method with the output of 3–5 kg of water per 10 kg of the dry sorbent per day.     

A novel route to perovskite lead titanate from lead and titanium glycolates via the sol–gel process

Pure perovskite lead titanate powder (PbTiO₃) is successfully produced via the sol–gel process using lead and titanium glycolates as starting precursors and has been synthesized by the oxide one spot synthesis process. The obtained lead titanate is of the tetragonal form of the perovskite phase, with high purity and nearly zero moisture content. From high‐resolution mass spectra, the XRD technique, Raman‐FTIR and TGA‐DTA analysis, the lead–titanium glycolates undergo sol–gel transition through the formation of Pb? O? Ti bonds. From the SEM micrographs, the PbTiO₃ particle shape transforms from an agglomerate sphere to a needle and fiber‐like shapes as the calcination temperature is varied above T_c. The corresponding molecular structural transformation, from the tetragonal form to the cubic form, occurs at 430 °C. The lead titanate powder calcined at 300 °C for 3 h has the highest dielectric constant and electrical conductivity values, namely 17470 and 1.83 × 10^?3, respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

The defluoridation of drinking water using multi-walled carbon nanotubes

In this study, the potential sorption capacity of multi-walled carbon nanotubes (MWCNTs) was investigated as a means of removing fluoride from the drinking water of a number of regions in Iran and from experimental solutions. The test was conducted in both batch and continuous operation modes. Batch mode experiments were used to study the effect of parameters such as pH, contact time, ionic strength, adsorbent dose, adsorbent capacity, and the presence of foreign anions on the efficiency of fluoride removal. The results showed that the highest level of sorption occurs at pH 5 (about 94% at 18 min). The ionic strength of the solutions and the presence of co-anions such as chloride, nitrate, sulfate, hydrogen carbonate, perchlorate had a negligible effect on the sorption of F⁻ onto MWCNTs. Sorption capacity measurements revealed that MWCNTs have a saturation capacity of 3.5 mg of F⁻ per gram. Sorption data were best fitted with the Fruendlich sorption isotherm equation, which indicates that F⁻ tends to be adsorbed on MWCNTs in a multilayered manner. Experiments using Kohbanan city drinking water, which contains the highest level of F⁻ among the drinking water samples studied, showed that MWCNTs can remove over 85% of fluoride content.     

Graphene oxide-based two-dimensional molecular brush for efficient removal of lead and copper ions from water media

In this study, graphene oxide (GO)-based two-dimensional molecular brush was fabricated by grafting polyacrylamide onto GO nanosheets for efficient removal of Pb²⁺ and Cu²⁺ from water media. Owing to the rich oxygen and nitrogen functional groups in the composites, the synthetic GO two-dimensional molecular brush can get the maximum adsorption capacity of 268.4 mg/g for Pb²⁺ and 127.2 mg/g for Cu²⁺, respectively. Moreover, the interspaces between the stacked two-dimensional molecular brushes provide fast pathways for the diffusion of heavy metal ions. As a result, GO-based two-dimensional molecular brush can reach the adsorption equilibrium within 60 min. These results indicated that the synthetic GO-based two-dimensional molecular brush is a promising adsorbent to separate heavy metal ions from water media.     

The use of solid sorbents for direct accumulation of organic compounds from water matrices–a review of solid-phase extraction techniques

The main principles of solid-phase extraction techniques are reviewed in this paper. Various solid sorbents can be used as a suitable trap for direct accumulation of organic compounds from aqueous solutions. The trapped analytes can be desorbed by elution with suitably chosen liquid phases. These preconcentration procedures can be considered as low performance liquid chromatography and the efficiency of the procedure can thus be related to the retention characteristics of the preconcentration column. The main sorbents used for trace enrichment purposes are also reviewed. Besides, the concise methodology, sample storage, and automation are discussed. The advantages of solid phase extraction as compared to liquid-liquid extraction are given as well as some drawbacks of this method.     

Immunoassay for the detection of lead ions in environmental water samples

A rapid, simple, and reliable competitive immunoassay was developed for measurement of lead ions Pb(II) in environmental samples. Avian antibodies were produced against Pb(II). Since lead ions are too small to elicit an immune response, the metal was coupled to protein carrier Bovine serum albumin (BSA) using a bifunctional chelator 1-(4-isothiocyanobenzyl) ethylenediamine N,N,N′,N′-tetra acetic acid (ITCBE). Poultry birds (layers) were immunised with this Pb(II)–ITCBE–BSA immunoconjugate and the avian antibodies (IgY) isolated from egg yolk recognised Pb(II)-ITCBE complexes as capture reagent and a Pb(II)–ITCBE conjugate of Alkaline phosphatase as an enzyme label. Antibody reaction was optimised for different concentrations of antigen and antibody dilutions. Cross reactivity with other metals were below 1% in competitive ELISA. The IC₅₀ value of this avian antibody was 0.19?µg?mL^?1. The detection range and the detection limit were 0.02–1000?µg?mL^?1and 0.2?µg?mL^?1, respectively.     

对氨基苯亚甲基硫代若丹宁固相萃取分离光度法测定环境水和食品样品中的铅

合成了新试剂对氨基苯亚甲基硫代若丹宁(ABTR),并用红外光谱、核磁共振氢谱和元素分析鉴定其结构。研究了ABTR与铅的显色反应,在pH3.8的HAc NaAc缓冲介质中,吐温80存在下,ABTR与铅反应生成2∶1稳定络合物,该络合物可被WatersSep PakC18小柱固相萃取,小柱上富集的络合物用乙醇洗脱后富集倍数可达50倍,在乙醇介质中,λmax=545nm,体系摩尔吸光系数ε=1.09×105L·mol-1·cm-1。铅量在0.05～4.0μg/mL内符合比尔定律,本法可用于环境水和食品样品中铅的测定。     

Preparation of functionalized magnetic nanoparticulate sorbents for rapid extraction of biphenolic pollutants from environmental samples

A new solid-phase extraction coupled with magnetic carrier technology was developed for extraction of bisphenol A (BPA) and diethylstilbestrol (DES) from water samples. The SPE sorbents, functionalized magnetic nanoparticles (Fe₃O₄@SiO₂/β-CD, core/shell), were synthesized in a two-stage system. The material was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and a vibrating sample magnetometer. SPE extraction parameters, such as volume and pH of sample, adsorption time, and desorption conditions were optimized. Under selected conditions: 250 mL of water sample, 0.1 g of sorbents and elution with methanol (3 mL with 1% acetic acid), the extraction was completed in 25 min. SPE followed by HPLC was employed to determine BPA and DES in environmental samples. The developed method provided spiked recoveries of 80–105%, relative standard deviations of less than 7%, and LOD of BPA (20.0 ng/L) and DES (23.0 ng/L), respectively. The proposed method offered easy preparation of sorbents, rapid analysis, high enrichment yields, and reliable quantitative assay.     

Effective removal of anionic dyes from aqueous solutions by novel polyethylenimine-ozone oxidized hydrochar (PEI-OzHC) adsorbent

The adsorption behavior of the anionic dyes Remazol Brilliant Blue R (RBBR) and Reactive Black 5 (RB5) from aqueous solutions by polyethylenimine ozone oxidized hydrochar (PEI-OzHC) was investigated. The adsorption capacities of both dyes increased with functionalization of PEI in the hydrochar adsorbent. The results of surface characterization (FTIR, BET, TGA, elemental analysis, and SEM) showed that PEI modification greatly enhanced the adsorbent surface chemistry with a slight improvement of adsorbent textural properties. In addition, the adsorption kinetics data showed an excellent adsorption efficiency as reflected in the high removal percentages of the anionic dyes. The Isotherm results indicated that RBBR and RB5 dye adsorption occurred via monolayer adsorption, and chemisorption was the rate-controlling step. The PEI-OzHC adsorbent possesses higher maximum Langmuir adsorption capacity towards RBBR (218.3 mg/g) than RB5 (182.7 mg/g). This increase in adsorption capacity is attributed to the higher number of functional groups in RBBR that interact with the adsorbent. This study reveals the potential use of adsorbents derived from pine wood hydrochar in municipal as well as industrial wastewater treatment. Furthermore, surface chemistry modification is proven as an effective strategy to enhance the performance of biomass-derived adsorbents.     

Starch-modified filters used for the removal of dyes from waste water

The present article proposes the use of starch-enriched flour as low-cost adsorbent of dyes. The adsorbents have been prepared by reticulation of starch-enriched flour using epichlorohydrin as crosslinking agent. These starch-modified filters exhibit interesting properties in terms of sorption rate. Studies concerning the sorption capacity are presented. The influence of the amine groups and the chemical structure of dyes are also studied. The regeneration procedure of the filters is showed and discussed. In order to explain the results, an adsorption mechanism mainly based on physical adsorption and interactions such as hydrogen bonds and ion-exchange due to the nature of the polymer network is proposed.     

Ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate as a solvent for extraction of lead in environmental water samples with detection by graphite furnace atomic absorption spectrometry

A novel method is described for the preconcentration of ultratrace amounts of lead in water. Dithizone is employed as a chelator forming a neutral lead-dithizone complex to extract lead ions from aqueous solution into the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate. Under optimal conditions, the extraction efficiency in one step and back-extraction efficiency with 5 mL of 0.1 mol L⁻¹ nitric acid were 99.9 and 99.8% for 20 μg of lead in 1 L of water solution, respectively. Preconcentration coupled with graphite furnace atomic absorption spectrometry was developed for the determination of lead in environmental water samples. The calibration graph was linear with a correlation coefficient of 0.998 at levels near the detection limits up to at least 0.1 μg L⁻¹. The detection limit, calculated as three times the standard error of the estimated calibration graph, is 1.0 ng of lead per liter of water sample. The determination of lead was free from interference from almost all cations and anions, and from humic acid in water from plant rot. Lead recoveries between 97.8 and 100.8% for spiked samples prove the accuracy of the method.     

Determination of lead in water samples after its separation and preconcentration by 4,5-dihydroxy-1,3-benzenedisulfonic acid functionalised polyurethane foam

A new sorbent based on polyurethane foam functionalised with 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron-PUF) was synthesised. This material was used in the development of a procedure for preconcentration of lead, with subsequent detection by flame atomic absorption spectrometry (FAAS). The influence of some variables involved in the extraction process was studied. Analytical parameters were evaluated using 50 and 500?mL of Pb (II) solution. Under optimum conditions, the system showed enrichment factors of 38 (50?mL) and 114 (500?mL). The detection limits obtained were 0.5 and 1.1?µg?L^?1 when volumes of 500 and 50?mL of Pb (II), respectively, were used. The method was applied to the determination of lead content in well water and drinking water samples collected in the town of Amelia Rodrigues, Bahia, Brazil.     

Use of amidoximated hydrogel for removal and recovery of U(VI) ion from water samples

Poly(acrylamidoxime-co-2-acrylamido-2-methylpropane sulfonic acid) (PAMSA) hydrogel was prepared by copolymerization of acrylonitrile and 2-acrylamido-2-methylpropane sulfonic acid as monomer, N,N′-methylenebis(acrylamide) as crosslinking agent and potassium peroxodisulfate as initiator. Amidoximated copolymer network was prepared by the reaction of copolymer network with hydroxylamine hydrochloride. A batch procedure was used for the determination of the characteristics of the U(VI) solid phase extraction from the amidoximated hydrogel. The determination of U(VI) was performed by spectrophotometric method using arsenazo-III as complexing agent. Optimal pH value for the quantitative preconcentration was 3, and full desorption was achieved with 3 mol L⁻¹ HClO₄. The adsorption process can be well described by the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm was closely fitted with the Langmuir model. A preconcentration factor of 20 and the three sigma detection limit of 2.8 μg L⁻¹ (n = 20) were achieved for uranium(VI) ions. The PAMSA hydrogel was used for separating and preconcentrating the uranyl ion existing in sea water samples, thermal spring water samples and the certified reference materials (TMDA 64; fortified lake water sample).     

Solid phase extraction and flame atomic absorption spectrometric determination of trace amounts of cadmium and lead in water and biological samples using modified TiO2 nanoparticles

A solid phase extraction procedure for the separation and preconcentration of trace amounts of Cd(II) and Pb(II) using the alizarin red S modified TiO₂ nanoparticles prior to their determination by flame atomic absorption spectrometry has been proposed. The influences of some analytical parameters such as pH, flow rates of sample and eluent, type and concentration of the eluent, and interfering ions on the recovery of Cd(II) and Pb(II) by the sorbent were investigated. The analytes were quantitatively sorbed from the aqueous solution at pH 5.5 onto a microcolumn packed with the sorbent and recovered with 2.0?mL of 1.5?mol?L^?1 hydrochloric acid. Under the optimum experimental conditions, the detection limits for Cd(II) and Pb(II) were 0.11 and 0.30?ng?mL^?1 and the relative standard deviations for ten replicate measurements of 5.0 and 50.0?ng?mL^?1 of Cd(II) and Pb(II) were 2.1 and 1.9%, respectively. A sample volume of 200?mL resulted in a preconcentration factor of 100. The method was successfully applied to the determination of Cd(II) and Pb(II) in water and biological samples, and accuracy was examined by the recovery experiments, independent analysis using electrothermal atomic absorption spectrometry, and analysis of a water standard reference material (SRM 1643e).     

Production of process water using integrated membrane processes

Application of ultrafiltration, nanofiltration, reverse osmosis, membrane distillation, and integrated membrane processes for the preparation of process water from natural water or industrial effluents was investigated. A two-stage reverse osmosis plant enabled almost complete removal of solutes from the feed water. High-purity water was prepared using the membrane distillation. However, during this process a rapid membrane fouling and permeate flux decline was observed when the tap water was used as a feed. The precipitation of deposit in the modules was limited by the separation of sparingly soluble salts from the feed water in the nanofiltration. The combined reverse osmosis—membrane distillation process prevented the formation of salt deposits on the membranes employed for the membrane distillation. Ultrafiltration was found to be very effective removing trace amounts of oil from the feed water. Then the ultrafiltration permeate was used for feeding of the remaining membrane modules resulting in the total removal of oil residue contamination. The ultrafiltration allowed producing process water directly from the industrial effluents containing petroleum derivatives. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

A novel route to perovskite lead zirconate from lead glycolate and sodium tris(glycozirconate) via the sol–gel process

A perovskite lead zirconate was synthesized, using lead glycolate and sodium tris (glycozirconate) as the starting precursors, by the sol–gel process. The obtained molar ratio Pb:Zr of PbZrO₃ was 0.9805:1. The TGA–DSC characterizations indicated that the percentage of ceramic yield was 56.4, close to the calculated chemical composition of 59.6. The exothermic peak occurred at 245.7 °C, close to the theoretical Curie temperature of 230 °C. The pyrolysis of PbZrO₃ of the perovskite phase was investigated in terms of calcination temperature and time. The structure obtained was the orthorhombic form when calcined at low temperature at 300 °C for 1 h; it transformed to the monoclinic and cubic forms of the perovskite phase at higher temperatures above the Curie temperature as verified by X‐ray data. The lead zirconate synthesized and calcined at 300 °C for 1 h has the highest dielectric constant, the highest electrical conductivity and the dielectric loss tangent of 2267, 3.058 × 10^?4 (Ω m)^?1 and 2.484 at 1000 Hz, respectively. The lead zirconate powder produced has potential applications as materials used in microelectronics and microelectromechanical systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Recyclable polymer-based nano-hydrous manganese dioxide for highly efficient Tl(I) removal from water

Tl(I)in water even at a trace level is fatal to human beings and the ecosystem.Here we fabricated a new polymer-supported nanocomposite(HMO-001)for efficient Tl(I)removal by encapsulating nanosized hydrous manganese dioxide(HMO)within a polystyrene cation exchanger(D-001).The resultant HMO-001 exhibited more preferable removal of Tl(I)than D-001 and IRC-748,an iminodiacetic chelating polymer,particularly in the presence of competing Ca(II)ions at greater levels in solution.Such preference was ascribed to the Donnan membrane effect caused by D-001 as well as the specific interaction between Tl(I)and HMO.The adsorbed Tl(I)was partially oxidized into insoluble Tl(III)by HMO at acidic pH,while negligible oxidation was observed at circumneutral pH.The exhausted HMO-001 was amenable to efficient regeneration by binary NaOH-NaClO solution for at least 10-cycle batch runs without any significant capacity loss.Fixed-bed column test of Tl(I)-contained industrial effluent and natural water further validated that Tl(I)retention on HMO-001 resulted in a conspicuous concentration drop from 1.3 mg/L to a value lower than 0.14 mg/L(maximum concentration level for industrial effluent regulated by US EPA)and from 1–4?g/L to a value lower than 0.1?g/L(drinking water standard regulated by China Health Ministry),respectively.     

A novel route to perovskite lead zirconate titanate from glycolate precursors via the sol–gel process

A perovskite lead zirconate titanate was synthesized by the sol‐gel process, using lead glycolate, sodium tris(glycozirconate) and titanium glycolate as the starting precursors. For the mole ratio Pb:Zr:Ti of 1:0.5:0.5 [Pb(Zr_0.5Ti_0.5)O₃], TGA‐DSC thermal analysis indicated that the percentage of ceramic yield was 55.8, close to the calculated chemical composition value of 49.5. The exothermic peak occurred at 268 °C below the theoretical Curie temperature of 400 °C. The pyrolysis of Pb(Zr_0.5Ti_0.5)O₃ of the perovskite phase was investigated in terms of calcination temperature and time. The structure obtained was of the tetragonal form when calcined at temperatures below 400 °C; it transformed to the tetragonal and the cubic forms of the perovskite phase on calcination above the Curie temperature, as verified by X‐ray data. The lead zirconate titanate synthesized and calcined at 400 °C for 1 h had the highest dielectric constant, the highest electrical conductivity and the dielectric loss tangent of 10 190, 0.803 × 10^?3 (Ω.m)^?1 and 1.513 at 1000 Hz, respectively. The lead zirconate titanate powder synthesized has potential applications as an electronic material. Copyright © 2008 John Wiley & Sons, Ltd.     

Continuous flow hydride generation laser induced fluorescence spectrometry for trace determination of lead in water and sediment samples

Continuous flow hydride generation coupled with laser induced fluorescence spectrometry (HG-LIF) has been used for the determination of Pb in aqueous samples. Lead hydride is generated in K₃Fe(CN)₆-HCl medium using NaBH₄ as the reducing agent. Parameters such as acidity and the concentrations of oxidising and reducing agents have been studied in order to obtain the highest sensitivity. Laser excitation of Pb has been performed at 283.306 nm and fluorescence has been detected at 365 nm and 405.8 nm. The limit of detection calculated for the optimised conditions (1% K₃Fe(CN)₆ in 0.3% Oxalic Acid, 0.055 mol L^?1 HCl, 1% NaBH₄ in 0.1% NaOH) is 0.3 ng mL^?1. However, a significant Pb background was observed for blank measurements, which degraded the limit of detection. The limit of detection that is estimated for a Pb free blank was determined by detuning the laser to a wavelength of 282.806 nm and was found to be 0.45 pg mL^?1. Method repeatability is 3.5% RSD at the 10 ng mL^?1 level. The accuracy of this method has been evaluated by analysis of a water reference material. The results obtained for a multielement standard determined using the HG-LIF approach have been found to be in agreement with those obtained by using a comparison ICP-AES approach. The HG-LIF approach has been applied to the measurement of Pb in a contaminated sediment sample material. The results of this study demonstrate that a small tunable laser system combined with hydride generation sample introduction can be used to measure Pb with high sensitivity, precision and selectivity in different sample matrices.     

Separation of zinc from aqueous samples using a molecular imprinting technique

In this article, the separation of zinc from aqueous samples by solid-phase extraction based on a molecular imprinting technique is described. Zn-imprinted polymer was prepared by free radical solution polymerisation in a glass tube containing ZnSO₄, morin, 4-vinylpyridine as a functional monomer, ethyleneglycoldimethacrylate as a cross-linking monomer, and 2,2′-azobisisobutyronitrile as an initiator. The obtained polymer block was ground and sieved (55–75 µm) and the Zn–morin complex was separated from polymer particles by leaching with 2M HCl. The synthesised polymer particles have been characterised by IR and differential scanning calorimetric studies either before or after leaching. The effects of different parameters, such as pH, adsorption and desorption time, type and minimum amount of the eluent for elution of the complex from polymer were evaluated. Extraction efficiency more than 99% was obtained by elution of the polymers with 10 mL of CH₂Cl₂–dimethyl sulfoxide (1 : 1, v/v). The detection limit of the proposed method was 2.9 µg L^?1. A dynamic linear range in the range of 25–200 µg L^?1 was obtained. The relative standard deviation was found to be below 9.2%. In addition, the influence of various cationic and anionic interferences on the complex recovery was studied. The method was applied to the recovery and determination of Zn in a few different real samples.