Apichat Imyim

Multi-element preconcentration of heavy metal ions from aqueous solution by APDC impregnated activated carbon

Ammonium pyrrolidinedithiocarbamate impregnated activated carbon (APDC-AC) has been used for the preconcentration of Cd(II), Cu(II), Ni(II), and Zn(II) from aqueous solution by column solid phase extraction (SPE) technique. Trace metal ions in aqueous solution were quantitatively sorbed onto APDC-AC packed in a SPE column at pH 5.0 with a flow rate of 1.0mLmin(-1). The sorbed metals were eluted with 1M nitric acid in acetone solution at a flow rate of 0.6mLmin(-1) and analyzed by flame atomic absorption spectrometry. The effects of sample volume, amount of APDC-AC, volume of eluent and ionic strength of working solution on metal ion recovery have been investigated. The present methodology gave recoveries from 90 to 106% and R.S.D. from 0.6 to 5.5%.

Highly selective preconcentration of Cu(II) from seawater and water samples using amidoamidoxime silica

Chemically modified silica containing amidoamidoxime group was studied as a sorbent for solid-phase extraction (SPE) and preconcentration of Cu(II) prior to determination by flame atomic absorption spectrometry (FAAS). The sorbent showed an extremely high selectivity towards Cu(II) in the pH range of 4-6, while the extraction of Pb(II), Cd(II), Ni(II) and Co(II) was low. The adsorption isotherm followed the Langmuir model and the maximum sorption capacity of 0.0163 mmol Cu(II)g(-1) was achieved. In the flow system, Cu(II) was completely retained on a column containing 40 mg of the modified silica at the flow rate of 4.0 mL min(-1) and quantitatively eluted by 5 mL of 1% (v/v) HNO(3). No interference from Na(+), K(+), Mg(2+), Ca(2+), Cl(-) and SO(4)(2-) at 10, 100 and 1000 mg L(-1) was observed. When applied for preconcentration and determination of Cu(II) in tap water, pond water, and seawater, the recoveries were 96, 101, and 95%, respectively, with high precision (% relative standard deviation (R.S.D.)<4) and low method detection limit (9 microg L(-1)).

Humic acids removal from water by aminopropyl functionalized rice husk ash

The use of rice husk ash (RHA) as an adsorbent for the adsorption of humic acids from water was studied. Optimum conditions for humic acids adsorption were found in batch method as follows, 60 min equilibrium time and initial in the range of pH 3-4. In addition, RHA was functionalized with 3-aminopropyltriethoxysilane. Again, the adsorption behavior of the modified rice husk ash (RHA-NH(2)) was studied. Optimum conditions for humic acids adsorption were found to be 30 min equilibrium time and initial pH in the range of 3-4. The adsorption capacity of RHA-NH(2) was higher than that of RHA. Experimental adsorption data fitted well with the Langmuir equation and the maximum adsorption capacity was 8.2mg/g. at pH 6. The column method was also performed. The comparative adsorption efficiencies of RHA-NH(2) and commercial activated carbons showed insignificant difference. The RHA-NH(2) adsorbent was applied for humic acids removal from surface water.

Long-term prediction of the leaching behavior of pollutants from solidified wastes

Abstract A methodology based on three experimental tests and a behavioral model was developed for the assessment of inorganic contaminant release from cement-based waste materials placed in an ‘immersed scenario’. The experimental ‘toolbox’ consists of the Pore water test (PWT), the Acid neutralization capacity test (ANC), and the Monolithic leaching test (ML). The experimental data supplied by the tests (leaching–available quantity, pore water composition, solubility vs. pH, released mass at the end of each leaching sequence) are the necessary input parameters for the behavioral model. The leaching model takes into account the transport phenomena coupled with main physico-chemical reactions in the saturated pore system of the material as well as in the eluate. The model, adapted to different scenarios, provides the concentration and the cumulative quantities released for each species. The methodology was applied on the wastes containing lead and stabilized/solidified with different hydraulic binders: two cements and a coal fly ash with lime. The stabilization of lead was better in the case of cement-based materials. The 10 years simulation of Pb release in the case of the particular scenario example, i.e. a water-storage reservoir built with the waste materials show that the lead concentration in stored water is higher than the accepted limit. Pb precipitation in the eluate can occur.

Environmental behaviour of a construction made of a mixture of hydraulic binders and air pollution control residues from municipal solid waste incineration Part 1. Physico-chemical characterisation and modelling of the source term

Abstract The reuse of waste materials requires the development of assessment methods for the long-term release of pollutants (source term) from wastes (or materials containing wastes) in contact with water. These methods depend on the scenario conditions: characteristics of the materials (especially physical structure and composition), contact with water. The scenario studied here is a water storage reservoir for fire fighting. The reservoir construction is made of a mixture of hydraulic binders and air pollution control (APC) residues from a municipal solid waste incinerator (MSWI). The modelling of the source term is performed in 5 steps ranging from the physico-chemical characterisation of the material to the validation of the proposed model by means of field simulation devices. This article presents the first steps of the methodology: physico-chemical characterisation of the source term, identification of the main transfer mechanisms and laboratory scale modelling of the source term. During the physico-chemical characterisation, it has been shown that the solidified waste shows a high basic capacity and that a relative decrease in pH during leaching favours retention of the main pollutants. During the first leaching sequences, the dynamic leaching tests show that the release of pollutants such as cadmium, arsenic, zinc and lead is extremely low but that the release of alkaline species (sodium and potassium) and chloride is very high from the beginning, whereas the release of calcium remains very high even after 3600 h of leaching. Identification of the main transfer mechanisms concludes that the release of soluble pollutants is the combined result of diffusional transfer of pollutants in the solution and the physico-chemical specificity of the species. The modelling based on these features enables a good simulation of the release but reveals a deviation from the experimental results after 500 h for alkaline species and 1000 h for Ca and Cl leaching. However, this deviation only appears after release of the major part of these elements.

Bulk optode sensors for batch and flow-through determinations of lead ion in water samples.

A sensitive optode consisting of highly lead-selective ionophore (Lead IV), proton-selective chromoionophore (ETH 5294) and lipophilic anionic sites (KTpClPB) in plasticized polyvinyl chloride (PVC) membrane was fabricated. The optode membranes were used for determination of Pb(2+) by absorption spectrophotometry in batch and flow-through systems. The influence parameters such as pH, type of buffer solution, response time and concentration of regenerating solution were optimized. The membrane responded to Pb(2+) by changing its color from blue to pinkish purple in Tris buffer containing different concentration of Pb(2+) at pH 7.0. The optode provided the response range of 3.16x10(-8) to 5.00x10(-5) mol L(-1) Pb(2+) with the detection limit of 2.49x10(-8) mol L(-1) in the batch system within the response time of 30 min. The dynamic range of 1.26x10(-8) to 3.16x10(-5) mol L(-1) Pb(2+) with detection limit of 8.97x10(-9) mol L(-1) were obtained in the flow-through system within the response time of 15 min. Moreover, the proposed optode sensors showed good selectivity towards Pb(2+) over Na(+), K(+), Mg(2+), Cd(2+), Hg(2+) and Ag(+). It was successfully applied to determine Pb(2+) in real water samples and the results were compared with well-established inductively coupled plasma optical emission spectrometry (ICP-OES). No significant different value (t(critical)=4.30>t(exp)=1.00-3.42, n=3 at 95% of confidence level) was found.

Determination of Cadmium, Nickel, Lead, and Zinc in Fish Tissue by Flame and Graphite Furnace Atomic Absorption after Extraction with Pyrrolidine Dithiocarbamate and Activated Carbon

A solid phase extraction (SPE) technique using an activated carbon column was developed for the extraction of trace levels of Cd, Ni, Pb, and Zn in aqueous solution which was obtained from the digestion of fish tissue. Ammonium pyrrolidin edithiocarbamate (APDC) was used to form metallic complexes that could be retained in a SPE column which was packed with powder activated carbon. The analytes were eluted from the column by nitric acid in acetone. The metal concentrations were determined by flame and graphite atomic absorption spectroscopy. The effects of flow rate, APDC concentration, and pH were investigated. The proposed method was validated. The method detection limits were 11.7, 13.4, 10.1, and 25.3 µg kg−1 for Cd, Ni, Pb, and Zn, respectively. The recoveries and RSDs were within the range of 81.9–101.1% and 0.6–6.0%, respectively. The method has potential merit for heavy metal determination in fish tissue.

Prediction of inorganic pollutant release from various cement based materials in disposa/utilisation scenario based on the application of a multi-parameter leaching tool box

The aim of this study is to assess the long term release of contaminants from cement based stabilised wastes. According to the methodology proposed by the European standard ENV 12 920, the impact of waste in disposal/utilisation scenarios has to be evaluated before being exposed to the environment. For this objective we propose a combined experimental and modelling procedure. Firstly a “tool box” consisting of some tests as the Pore Water simulation test (PW), the Maximum Leachable Fraction test (MLF), the Acid Neutralisation Capacity test (ANC), and the Monolithic Leaching Test (MLT) is used to characterise the waste containing material. Secondly the results of the tests are the necessary input parameters for the coupled physico-chemical leaching model that provides the long-term leaching behaviour. For applying the tool box and the model validation, Ordinary Portland Cement with additives was used to prepare the samples containing 25% of binder, 1% of Pb, and sand. The release mechanisms are described. The model provides the long-term release amounts of pollutants as well as the expected concentrations of pollutants in surrounding natural water over several centuries in the considered scenario conditions.

Simple spectrophotometric method for determination of melamine in liquid milks based on green Mannich reaction

A new and simple spectrophotometric method has been developed and validated for measuring the contamination of melamine in different milk products. The method is based upon measuring the absorption of the complex formed from melamine, 4-hydroxyacetophenone (Hap) and 1-pyrene carboxaldehyde (Pcd), which was adapted from the Mannich reaction. Quantitative analysis was done at a wavelength of 236 nm within a few minutes. The reaction was optimized by focusing on both obtaining high performance of the method and to concern the volatility and toxicity of used reagents. This method provided a linear dynamic range, limit of detection and limit of quantification of 0.100-3.78, 0.08 and 0.14 mg L(-1), respectively. The relative standard deviation (RSD) was 3.6% (n=10). The recoveries of melamine spiked liquid milk samples, with melamine concentrations of 0.63, 1.26, 1.89 and 2.52 mg L(-1), were 87.7±3.7%, 91.1±8.8%, 89.2±4.4% and 90.6±3.6% (n=3), respectively.

Naked eye screening of 11 phenolic compounds and colorimetric determination using polydiacetylene vesicles with α-cyclodextrin

The colorimetric response (CR) of poly(10,12-pentacosadiynoic acid) vesicles (PPCDA) induced by α-cyclodextrin (α-CD) in an aqueous solution has been studied. Various parameters affecting the CR, such as response time and concentration were investigated. The blue color of 0.01 mM PPCDA solution became pinkish red with the addition of α-CD at the concentration higher than 3 mM. The inhibition of the color transition from blue to red was investigated using 11 phenolic compounds. The color transition could be inhibited and observed by naked eye in the presence of 4 phenolic compounds, i.e. 4-nitrophenol (4-NP) and 4-bromophenol (4-BP) and 4-chlorophenol (4-CP) and 3-nitrophenol (3-NP). A colorimetric method for the determination of these compounds was validated and applied for surface water analysis. The linear range from the plot of CR against phenolic compounds concentration was in the order of 0.5-2.0 mM with R(2) more than 0.99. The recoveries were 90-95% with good precision (1-4%RSD, n=10).