Removal of Pb(II) from aqueous solutions by carbons prepared from Sal wood (Shorea robusta)

In the present work, physically and chemically activated carbons are prepared using Sal wood (Shorea robusta) sawdust by thermal process and using sulfuric acid as the activation agent to remove Pb(II) from aqueous solutions. Adsorption equilibrium studies have been done at a pH of 4 and a room temperature of 30 °C. It was found that the adsorption isotherms are favorable and chemically activated carbons are better than physically activated carbon in terms of adsorption capacity. Various two-parameter adsorption isotherm models, viz. Freundlich, Langmuir, Temkin and Dubinin-Radushkevich, were used to fit the equilibrium data and it was found that the Freundlich adsorption model provided best-fit. The first-order irreversible unimolecular reaction model and the pseudo-second-order kinetic models were used to fit the kinetic data and it was found that both the models provided good fit. Kinetic and film diffusion studies show that the adsorption of lead(II) on the activated carbons tested in this work are both intra-particle and film diffusion controlled.     

Sawdust of lam tree (Cordia africana) as a?low-cost, sustainable and easily available adsorbent for the removal of toxic metals like Pb(II) and Ni(II) from aqueous solution

Sawdust of lam tree (Cordia africana) has been investigated as an adsorbent for the removal of lead and nickel ions from aqueous solution. Since lam tree is widely grown in almost all the eastern, western, central and southern tropical African countries (United States Department of Agriculture, GRIN, Maryland), it can be a?common most easily available, sustainable, low cost adsorbent for the treatment of wastewaters in this part of the world where growing industrialization is affecting water quality like elsewhere in the world. Therefore, it is worthwhile to investigate the potential of sawdust of lam tree as an adsorbent for the removal of lead and nickel ions from aqueous solution as a?first step. The effect of contact time, pH, metal ion concentration and temperature on adsorption of these metal ions has been investigated to identify the optimum conditions for maximum adsorption. The equilibrium time was found to be 50?min for Pb⁺⁺ and 70?min for Ni⁺⁺ adsorption. Adsorption starts at a?low pH and increases steadily as the pH increases. The equilibrium adsorption data at temperatures of 25, 40 and 60°C were analyzed by the Langmuir and Freundlich isotherm models. Although equilibrium adsorption data conforms to both the models, the best fit was obtained with the Langmuir isotherm. Thermodynamic parameters like equilibrium constant, enthalpy change, free energy change, and entropy change were calculated and discussed. The maximum adsorption capacity of sawdust for Pb⁺⁺ and Ni⁺⁺ were calculated from the Langmuir isotherms. The metal uptake was found to increase with increase in temperature. The positive values of ??H ^o and negative values of ??G ^o together indicate that the adsorption of Pb⁺⁺ and Ni⁺⁺ on sawdust of lam tree is endothermic and spontaneous in nature. The study demonstrated that the sawdust of lam tree can be effectively used as an adsorbent for the removal of metal ions from aqueous solutions.     

Sorption studies of Zn(II)- and Cd(II)ions from aqueous solution on treated sawdust of sissoo wood

Sawdust, an inexpensive material, has been utilized as an adsorbent for the removal of Zn(II)- and Cd(II)ions from aqueous solution. The effects of time of equilibrium, pH, temperatures and dosage of the adsorbent on the removal of Zn(II)- and Cd(II)ions have been studied. The equilibrium nature of Zn(II)- and Cd(II)ions adsorption at different temperatures (25–60 °C) has been studied. The percent adsorption of Zn(II)- and Cd(II)ions increased with an increase in pH, temperature and dosage of treated sawdust. The applicability of the Langmuir isotherm suggests the formation of monolayer coverage of Zn(II)- and Cd(II)ions at the surface of the adsorbent. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of Zn(II)- and Cd(II)ions has also been computed and discussed. The heat of adsorption [ΔH=17.706 kJmole^-1 for Zn(II) and ΔH=16.949 kJmole^-1 for Cd(II)] implied that the adsorption was an endothermic adsorption. The sawdust was found to be a metal adsorbent as effective as activated carbon.     

Adsorption of Cu2+ by Crosslinked Graft Copolymers of Starch

With the use of acrylic acid(AA)as a monomer,humic acid(HA)and starch as raw materials,potassium persulfate(KPS)as initiator,and N,Ndimethylacrylamide(MBA)as a cross-linking agent,AA/HA/Starch graft copolymer was prepared and characterized by SEM and FT-IR.The effects of temperature,adsorption time,adsorbent dosage,pH value and Cu²⁺initial concentration of the solution on the adsorption performance of the crosslinked graft copolymer were also investigated.The results showed that the Cu²⁺adsorption capacity of the AA/HA/Starch graft copolymer increased firstly and then decreased with increasing adsorbent dosage and the initial pH value of Cu²⁺solution.With the increase of Cu²⁺initial concentration and the extension of adsorption time,the adsorption amount of Cu²⁺increased rapidly and then stabilized.And it decreased slightly with the increase of temperature.At pH value of 5.5,temperature of 298 K,adsorbent dosage of 50 mg,adsorption time of 125 min,and 100 mL Cu²⁺solution with Cu²⁺initial concentration of 100 mg/L,the Cu²⁺adsorption capacity of the crosslinked graft copolymer was 238 mg/g.The adsorption of Cu²⁺by the adsorbent followed the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model,and the adsorption was attached to monolayer chemical adsorption.This study proved that AA/HA/Starch graft copolymer could be used as an efficient adsorbent for the removal of harmful and toxic metal cations such as Cu²⁺from industrial wastewater.     

Hybrid Amine-Functionalized Titania/Silica Nanoparticles for Solid-Phase Extraction of Lead,Copper, and Zinc from Food and Water Samples: Kinetics and Equilibrium Studies

In the present study, hybrid amine-functionalized titania/silica nanoparticles were employed as a new and novel adsorbent for solid-phase extraction of Pb²⁺, Cu²⁺, and Zn²⁺ ions prior to their determination using flame atomic absorption spectrometry. Under the best conditions (including adsorbent, 0.4 g; eluent, 5.0 mL nitric acid (HNO₃), 3.0 mol L^?1, 1.0 mL min^?1; and sample, pH 5.0, 3.0 mL min^?1), detection limits, adsorption capacities, and preconcentration factors were 0.12–0.24 μg L^?1, 7.1–20.7 mg g^?1, and 200, respectively. To predict the adsorption isotherms, different isotherm models were studied and the obtained results showed that the Langmuir model is the most suitable one to explain the experimental data. The kinetics of the reaction followed pseudo-second-order kinetic model. Thermodynamic parameters like free energy (ΔG ⁰) and enthalpy (ΔH ⁰) confirmed the spontaneous and exothermic nature of the process. The method was successfully applied for determination of the analytes in different food and water samples.     

Removal of methylene blue from aqueous media using activated carbon web

Activated carbon web is prepared by controlled pyrolysis of acrylic fibrous waste under the layer of charcoal using physical activation in high-temperature furnace. The carbonization was carried out at 1200 °C under different heating rate (i.e. 150 to 450 °C h^?1) with different holding time (i.e. 0 to 60 min) to decide optimum pyrolysis parameters. The heating rate of 300 °C h^?1 with no holding time revealed higher specific surface area of 280 m² g^?1. The prepared activated carbon web was later employed as adsorbent for removal of methylene blue from aqueous media. The effect of initial dye concentration, adsorbent dosage, stirring speed, and pH of solution was studied. The obtained results were later compared with adsorption isotherms (i.e. Langmuir and Freundlich). The Freundlich model was found to fit closely with results due to heterogeneous adsorption of dye molecules. Finally, virgin activated carbon and dye adsorbed activated carbon were tested for desorption behavior using differential scanning calorimetry and thermo gravimetric analysis. The significant reduction in desorption enthalpy from 172.46 to 52.43 J g^?1 is attributed to less adsorption energies of dye molecules on the surface of activated carbon due to nonhomogeneous distribution of active sites.     

Chromium(III) removal in tannery waste waters using Chinese Reed ( Miscanthus Sinensis), a fast growing plant

Dried Chinese Reed (Miscanthus sinensis) was investigated as adsorbent for the removal of Cr(III) from tannery wastewater. Batch mode adsorption studies were conducted using aqueous solutions of Cr(III). Parameters studied include Cr(III) concentration, agitation time, adsorbent dose and pH. Adsorption followed pseudo-second order kinetic model. Equilibrium adsorption data obeyed both Langmuir and Freundlich isotherms. Langmuir adsorption capacity was found to be 1.85 mg/g. Effects of pH on adsorption and desorption show that both ion exchange and chemisorption are involved in the adsorption process.     

Heat-treated wood as chromium adsorption material

Heavy metals adsorption with lignocellulosic materials has been heavily researched in the last years. Since heat activation has been used with good results to increase the adsorption capacity of some materials, heat-treated wood might be a better adsorbent. This hypothesis is the basis of the present study. The adsorption tests were made with powdered pine wood, heat-treated at 190–210?°C. All the heat-treated samples showed a significantly higher adsorption compared to untreated wood. The maximum adsorption was obtained at pH 3 for heat-treated wood at 210?°C. The kinetics of the adsorption process fitted a pseudo-second-order reaction (R² 0.990–0.996). Adsorption fitted well both the Langmuir and the Freundlich model, but the Freundlich model presented higher R² (0.988–0.998). The q_max values estimated by the Langmuir plotting were in the range 15.6–19.4 mg/g and the n values from Freundlich isotherms between 1.87 and 2.39. Heat-treated wood was a better adsorption material than untreated wood for chromium adsorption. This can be a good application for the sawdust produced by the processing of heat-treated wood at primary and secondary wood processing mills or for the recycling of heat-treated wood at the end of product life.     

Cell wall anthocyanin adsorption by different Saccharomyces strains during the fermentation of Vitis vinifera L. cv Graciano grapes

This work reports the adsorption of anthocyanins by the cell walls of different strains of Saccharomyces during the production of red wine from Vitis vinifera L. cv Graciano grapes. The anthocyanin derivative contents of the yeast cell walls were substantially different to those of their corresponding wines. Cinnamoyl derivatives (6-p-coumaroyl and 6-caffeoyl) were strongly adsorbed while vitisins (adducts of pyruvic acid and acetaldehyde) were weakly adsorbed. The mean total anthocyanin concentration of the wines was 507.64 mg L^?1 with the following distribution: 3-glucosides (3G), 82.2%; vitisins, 0.97%; 6-acetyl derivatives, 7.44%; 6-caffeoyl derivatives, 1.81%; and 6-p-coumaroyl derivatives, 7.54%. A mean of 18.57 mg of anthocyanins were adsorbed by the lees corresponding to 1 L of wine; this quantity was distributed: 3G, 52.60%; vitisins, 0.15%; 6-acetyl derivatives, 4.06%; 6-caffeoyl derivatives, 6.61%; and 6-p-coumaroyl derivatives, 36.58%. Large differences were seen between the different yeast strains examined with respect to the quantities of anthocyanins adsorbed. The mean adsorption percentage was 3.67%, but this varied between 1.60% (strain 3VA) and 5.85% (strain 9CV). The adsorption percentage of 6-p-coumaroyl derivates for strain 3VA (7.61%) was fourfold less than that of 9CV (28.37%). Strains 2EV and 3VA showed no vitisin adsorption.     

Synthesis of octadecyl acrylate-co-ethylene glycol dimethacrylate resin for removal of dark-colored compound from apple juice and comparison with polyvinylpolypirrolidone (PVPP)

Adsorption process has an importance for improving the color of juice and also stabilizing the final product during the shelf life. In this study, polyvinylpolypirrolidone (PVPP) and octadecyl acrylate-co-ethylene glycol dimethacrylate (ODA-EGDMA) polymeric resins were used as adsorbents for improving the color properties of apple juice. The ODA-EGDMA resin was prepared by classical suspension polymerization technique and characterized by electron microscopy. The obtained spherical particles diameters were between 20 and 140 μm. PVPP was selected as reference polymeric material for its importance in the juice industry. The adsorption kinetics of dark-colored compounds on adsorbent polymeric resins were studied at different adsorbent resins concentrations (1, 2, 4, and 8 g adsorbent resin per liter of apple juice) at the constant temperature (20 °C) in batch reactor. Langmuir adsorption model was applied for both PVPP and ODA-EGDMA polymeric adsorbents. The Langmuir isotherms were plotted for both polymeric adsorbents by evaluation of the absorbance data of apple juice at 420 nm. Langmuir isotherm's empirical constants known as K _ad and Q ₀ were calculated from the equilibrium data. Numerical value of K _ad and Q ₀ were determined as 5.0578 and 0.3089 for the ODA-EGDMA polymeric resin, 2.4824 and 0.5268 for the PVPP adsorbent, respectively. The scope of this study included comparison of reusability and regeneration properties of the each polymeric adsorbent. For this purpose, series of experiment were done in pack bed column application. Pressure drop measured throughout the PVPP pack bed column was 4.8 times higher than ODA-EGDMA pack bed column at same flow rate (2.5 mL/min) during the this group experiment. ODA-EGDMA resin and PVPP were regenerated with NaOH (4% w/v, 50 °C) after each run. After regeneration, average removal of dark color (relative absorbance change at 420 nm) of apple juice was determined as 76.47±0.90% for ODA-EGDMA and 91.51±0.86% for PVPP adsorbent resin.     

Isotherm modeling of organic activated bentonite and humic acid polymer used as mycotoxin adsorbents

The aim of the current study was to evaluate and compare two representative samples of different classes of adsorbents intended for use as feed additives in the prevention or reduction of the adverse effects exerted by mycotoxins, specifically ochratoxin A (OTA) and zearalenone (ZEN). The adsorbents, an organically activated bentonite (OAB) and a humic acid polymer (HAP), were tested in a common in vitro model with a pH course comparing the maximum pH changes that can be expected in the digestive system of a monogastric animal, i.e. pH 7.4 for the oral cavity, pH 3.0 for the stomach, and pH 8.4 for the intestines. In the first experiment, the concentration-dependent adsorbent capacity of OAB and HAB were tested using a fixed concentration of either mycotoxin. Thereafter, adsorption was evaluated applying different isotherms models, such as Freundlich, Langmuir, Brunauer–Emmett–Teller (BET) and Redlich–Peterson, to characterize the adsorption process as being either homo- or heterogeneous and representing either mono- or multilayer binding. At the recommended statutory level for the mycotoxins of 0.1?mg?kg^?1 OTA and 0.5?mg?kg^?1 ZEN, OAB showed an adsorbed capacity of >96% towards both mycotoxins, regardless of the pH. The HAP product was also able to absorb >96% of both mycotoxins at pH 3.0, but extensive desorption occurred at pH 8.4. Based on χ-square (χ²) values, Langmuir and Redlich–Peterson equations proved to be the best models to predict monolayer equilibrium sorption of OTA and ZEN onto the organically activated bentonite and the humic acid polymer. The applied methodology has a sufficient robustness to facilitate further comparative studies with different mycotoxin-adsorbing agents.     

Discoloration Kinetics of Clarified Apple Juice Treated with Lewatit® S 4528 Adsorbent Resin During Processing

The present work studies the adsorption of colored compounds in apple juice with a Lewatit® resin S 4528. The sorption equilibrium through the adsorption isotherms for 20, 35, and 50 °C was studied. The absorbance at 420 nm was used to measure the concentration of colored compounds, which permits correlating the residual concentration with the adsorbed concentration, proving that the data matched reasonably well according to the Langmuir and Freundlich models. Also, the efficiency of the adsorption process was studied for different resin/juice mass ratios at different temperatures, from which it was observed that there was an improvement in efficiency as the resin content increased, while the increase in temperature was not so important in the process. The adsorption kinetics at 35 °C for different resin/juice mass ratios was also studied. The kinetic model developed by Ibarz was used, concluding that the data matched this model reasonably well. The adsorption kinetic constant was always higher than the desorption kinetic constant, which indicates that the adsorption stage predominates the desorption stage. The adsorption kinetic constant shows a decreasing tendency with the raise in the resin/juice ratio, and the desorption kinetic constant shows an increasing tendency. The variation of the CIELab color parameters (L*, a*, and b*) with the adsorption time was studied, obtaining results that match the kinetic adsorption model proposed.     

Chromium(III) removal in tannery waste waters using Chinese Reed (<Emphasis Type="Italic">Miscanthus Sinensis</Emphasis>), a fast growing plant

Dried Chinese Reed (Miscanthus sinensis) was investigated as adsorbent for the removal of Cr(III) from tannery wastewater. Batch mode adsorption studies were conducted using aqueous solutions of Cr(III). Parameters studied include Cr(III) concentration, agitation time, adsorbent dose and pH. Adsorption followed pseudo-second order kinetic model. Equilibrium adsorption data obeyed both Langmuir and Freundlich isotherms. Langmuir adsorption capacity was found to be 1.85 mg/g. Effects of pH on adsorption and desorption show that both ion exchange and chemisorption are involved in the adsorption process.

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Entfernen von Chrom(III) aus Gerberei-Abwasser mit Miscanthus Sinensis

Zusammenfassung Getrocknetes Chinagras (Miscanthus Sinensis) wurde untersucht auf seine Eignung als Adsorbens zum Entfernen von Chrom(II) aus Gerberei-Abwasser. Batchversuche mit wässrigen Chrom(III)-Lösungen wurden unternommen. Die untersuchten Parameter waren: Chromkonzentration, Behandlungszeit, Anteil an Adsorbens und pH-Wert. Die Adsorption folgte dem kinetischen Modell einer Pseudo-Reaktion 2. Ordung. Die Gleichgewichtsdaten entsprachen sowohl der Langmuir- als auch der Freundlich-Isotherme. Die Adsorptionskapazität nach Langmuir betrug 1,85 mg/g. Einflüsse des pH auf Adsorption und Desorption zeigen, dass sowohl Ionenaustausch als auch Chemosorption am Absorptionsprozess beteiligt sind.

     

The biosorptive effect of untreated and chemically modified fir cone powder on Pb(II) removal

In this work, the main aim was to investigate the adsorption potential of untreated and chemically modified (sodium hydroxide and hydrogen peroxide treatment) fir cone powder (Abies alba) for the removal of Pb(II) from aqueous solutions. The effect of contact time, initial concentration of Pb(II), initial pH and temperature was studied in a batch process mode. Adsorption isotherm models (Langmuir, Freundlich, Dubinin–Radushkevich (D–R) and Temkin) and kinetics (pseudo-first-order and pseudo-second-order) models for both processes (treated and untreated) were used to analyse the equilibrium data. The kinetic data were found to fit better the pseudo-second-order. Maximum adsorption capacities calculated using the Langmuir model are 4.8 and 2.9 mg/g for NaOH and H₂O₂ treated fir cone powder, respectively, and 3.7 mg/g for untreated fir cone powder. The results indicate that the NaOH treatment increases the fir cone powder adsorption capacity, while the H₂O₂ treated biomass showed a slight decrease in its adsorption capacity in comparison to the untreated one.     

Determination of color additive tartrazine (E 102) in food samples after dispersive solid phase extraction with a zirconium-based metal-organic framework (UiO-66(Zr)-(COOH)2)

ABSTRACT

A new and rapid dispersive solid phase extraction method by using a green-synthesised UiO-66(Zr)-(COOH)₂ (Zr-BTeC) adsorbent with body-centred cubic (bcu) topology was developed for determination of tartrazine in food samples. Zr-BTeC was used for the first time as an adsorbent for tartrazine. It was synthesised and characterised by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis, and zeta potential measurements. Tartrazine was determined at 405 nm spectrophotometrically. Experimental conditions were optimised in order to achieve quantitative recoveries. The sample acidity was found to be 0.02 mol L^?1 HCl. The amount of Zr-BTeC was 10 mg. Both adsorption and elution contact times were only 5 s without the need for vortexing. Elution was with 2 mL of 0.5 mol L^?1 NH₃. A sample volume of 45 mL was selected as optimum. The adsorption capacity for tartrazine with Zr-BTeC was found to be 185 mg g^?1 and the adsorbent was reusable up to 40 cycles. The tartrazine concentrations found by the developed method in food supplements were compared with the results obtained by HPLC method for the same samples. Statistical analysis results showed that there are insignificant differences between the results of the two methods (p = .05). The method was successfully applied to the determination of tartrazine in spiked chewing gums, lemon flavoured icing glaze, and jelly samples.     

Determination of Quercetin, Gallic Acid, Resveratrol, Catechin and Malvidin in Brazilian Wines Elaborated in the Vale do São Francisco Using Liquid–Liquid Extraction Assisted by Ultrasound and GC-MS

In this work, a fast and simple methodology has been applied for the determination of gallic acid, resveratrol, catechin and malvidin in Brazilian wines by gas chromatography–mass spectrometry. The procedure included a stage of ultrasound-assisted liquid–liquid extraction and subsequent derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and GC-MS analysis. The limit of detection varied from 0.41 to 1.18 mg?L^?1 in all the analytes. The relative standard deviations calculated for 8.0 and 20 mg?L^?1 were 1.90 and 0.82 % for gallic acid, 3.08 and 1.22 % for catechin, 1.30 and 0.44 % for malvidin, 1.50 and 0.53 % for resveratrol, and 1.41 and 0.61 % for quercetin. The developed methodology was applied for the analysis of red wine samples collected in the São Francisco region, Bahia state, Brazil. Quercetin concentration varied from 2.4 to 3.0 mg?L^?1, gallic acid 21.4–56.3 mg?L^?1, resveratrol 1.5–5.9 mg?L^?1, malvidin 15.3–32.2 mg?L^?1, and catechin 11.71–18.2 mg?L^?1. The obtained concentrations are in agreement with those reported in the literature.     

Preparation of tea catechins using polyamide

An adsorption separation method using Polyamide-6 (PA) as an adsorbent was developed to separate catechins from green tea extract. The adsorption capacity of total catechins for PA was 193.128 mg g⁻¹ with an adsorption selectivity coefficient K_A^B of total catechins over caffeine 21.717, which was better than macroporous resin model HPD 600. The Langmuir model and the pseudo-second order mode were primely fitted to describe its equilibrium data and adsorption kinetics, respectively. PA column separation by two-step elution using water and 80% (v/v) aqueous ethanol was established to prepare catechins complex which contained 670.808 mg g⁻¹ total catechins and 1.828 mg g⁻¹ caffeine. It is considered that PA was a promising adsorbent for selective isolation of catechins.     

含铬废革屑对水体中染料的吸附

研究了含铬废革屑对水体中染料的吸附特性。结果表明 :含铬废革屑对酸性染料和直接染料有较大的吸附量 ,但对碱性染料的吸附量却较低。在酸性嫩黄G的最适吸附pH值为 3 .0的条件下 ,酸性嫩黄G的平衡浓度为 82 9mg/L ,其平衡吸附量达到 2 3 4mg/g ;在直接红棕RN的最适吸附 pH值为 9.0的条件下 ,直接红棕RN的平衡浓度为 1 1 5 7mg/L时 ,其平衡吸附量达到 1 5 2mg/g。含铬废革屑对酸性嫩黄G的吸附平衡符合Langmuir方程 ,而对直接红棕RN的吸附平衡符合Freundlich方程。吸附动力学研究表明 :含铬废革屑对以上 2种染料的吸附 ,符合拟二级速度方程。     

Preconcentration of trace levels of cadmium (ІІ) ion using <Emphasis Type="Italic">Descurainia Sophia</Emphasis> seeds as a green adsorbent for solid phase extraction followed by its determination by flame atomic absorption spectrometry

For the first time, Descurainia Sophia (DS) seeds as an efficient and green adsorbent were used in solid phase extraction for preconcentration of trace levels of cadmium prior to its determination by flame atomic absorption spectrometry (FAAS). By using a batch method, Descurainia Sophia seeds were used as adsorbent to retain cadmium (??) ions in the sample solution. After eluting the adsorbent with 3 mol L^?1 HCl, the retained cadmium (??) was determined by flame atomic absorption spectrometry. Different parameters affecting the extraction efficiency such as pH, amounts of adsorbent, type and concentration of eluent solvent, extraction and desorption time were investigated and optimized. Under the optimum conditions, the calibration curve was linear in the range of 5–300 µg L^?1 cadmium (??) with a correlation coefficient of 0.998. The limit of detection (LOD) was 1.0 µg L^?1 and the relative standard deviation (RSD, %) based on seven replicate analysis of 25 µg L^?1 cadmium (??) was 3.2%. The accuracy of the proposed method was checked by the analysis of certified reference material (CRM) and spike methods. The results show a good agreement with certified values. The proposed method was successfully applied to determination of trace levels of cadmium in different water and rice flour samples.     

Speciation of Inorganic Antimony in Food and Water Samples by Flow Injection On-line Nano γ-Alumina Micro-column Solid-Phase Extraction Coupled with Slotted Tube Atom Trapping Flame Atomic Absorption Spectrometry

Nano γ-alumina, with ultra-high specific surface area (387.2 m²?g^?1), has been synthesized and used as a promising adsorbent material in solid-phase extraction. A simple, sensitive, and economic method was developed for speciation of inorganic antimony by slotted tube atom trapping flame atomic absorption spectrometry (STAT-FAAS) after flow injection on-line nano γ-alumina micro-column solid-phase extraction. In this method, Sb(III)–diethyldithiocarbamate (DDTC) complexes produced on-line from DDTC and Sb(III) were adsorbed by the synthesized γ-alumina nanoparticles in a micro-column, then eluted by 1.0 mol?L^?1 HNO₃ in methanol, whereas Sb(V) remained in aqueous solution. The total inorganic Sb was determined by the same procedure after Sb(V) was reduced with thiourea. Under optimal conditions, the enrichment factor was 56.5 and the detection sensitivity was improved 40-fold for antimony by STAT-FAAS compared to conventional FAAS. The limit of detection was 6.0 ng?L^?1 for Sb(III) and 8.2 ng?L^?1 for Sb(V), respectively. The intra-day precision (RSDs, n?=?11) were 2.8 % for Sb(III) and 3.5 % for Sb(V), respectively, and the inter-day precision (n?=?3) were 7.1 % for Sb(III) and 8.4 % for Sb(V), respectively. The recoveries for the spiked samples were 93–107 %. The proposed method was applied to speciation of inorganic antimony in water and food samples successfully.