Woravith Chansuvarn

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.

Adsorption of Pb(II) from aqueous solution onto manganese oxide-modified laterite soil

The objective of this work was to study the adsorption efficiency of natural soil and its surface modified with manganese oxide for removal of Pb(II) ion. The adsorption of Pb(II) from aqueous solution onto raw laterite soil (LS) and manganese oxide-modified laterite soil (Mn-LS) was evaluated based on batch method. The adsorption efficiency of Pb(II) was investigated as a function of the initial pH, equilibrium time, adsorbent concentration and initial Pb(II) concentration and temperature. The maximum monolayer adsorption capacities of LS and Mn-LS were estimated as 1.053 and 38.76 mg g-1, respectively. The results show that the amount of Pb(II) adsorbed onto Mn-LS was more than LS by about 39-times under the optimized adsorption condition. The adsorption isotherms of Langmuir and Freundlich models was used to describe the equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The calculated adsorption energy (14.95 kJ mol-1) from the Dubinin-Radushkevich (D-R) model indicated that the adsorption process onto Mn-LS was taken place mainly by chemical ion exchange. The kinetic evaluation also suggested that the adsorption process of both adsorbents followed well the pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Pb(II) onto LS and Mn-LS process was feasible, spontaneous and endothermic.

Modification of Natural Clay Surface with Manganese-Oxide for Removal of Cadmium(II) Ion from Aqueous Solution

Natural clay (NC) and its surface modified with manganese oxide (MnO-NC) was assessed for removal of Cd (II) ion by batch adsorptive process. The surface modification of NC was chemically prepared with manganese chloride in basic solution by simple procedure, resulting in larger surface area than raw material by about 10-times. FT-IR spectra and SEM photograph showed the unique characteristic of MnO-NC after chemically surface modification with MnO2 particles successfully set down onto the NC surface. Under optimum conditions as a function of solution pH of 6.0, adsorbent dose of 5 g/L, contact time of 15 min and initial cadmium concentration of 100 mg/L, the adsorption capacity reach to 30.6 mg/g. By comparing with NC, MnO-NC provides higher adsorptive capability than the one by about 30-times. Based on isotherm estimation, the Langmuir adsorption isotherm showed more suitable for both adsorbents with the best correlation coefficient (r2>0.99) than the Freundlich isotherm. The adsorptive kinetics of Cd (II) onto NC and MnO-NC followed the pseudo-second-order.

Adsorption of Cadmium(II) Ion from Aqueous Solution onto a Raw Material of Bamboo Powder and its Surface Modification

This work was focused on evaluating the potential of bamboo powder modified with manganese oxide (MnO-BP) as a low-cost byproduct adsorbent for the adsorption of cadmium(II) ion. A batch method was carried out at room temperature and the optimized conditions. The optimization of adsorption parameters including pH, equilibrium time, dosage and initial Cd(II) concentration was also systematically studied for the removal of cadmium(II) ion. The maximum monolayer adsorption capacity of MnO-BP was estimated as 8.57 mg/g that it more adsorption capacity than untreated-bamboo powder by about 5 times. The Langmuir and the Freundlich isotherms were used to describe the adsorptive mechanism and calculated the maximum monolayer adsorption capacity. It was found that the data from MnO-BP fitted well to the Freundlich isotherm with R2>0.99. It indicated that the adsorptive behavior of MnO-BP to cadmium(II) ion is preferable. In this work, MnO-BP was used for the removal of cadmium(II) ion in wastewater sample. The MnO-BP is a low-cost adsorbent that can be used to remove cadmium(II) effectively.

Distribution of Residue Carbofuran and Glyphosate in Soil and Rice Grain

The distribution of residual pesticides in soil and rice grain was studied in rice farming area covered in Samchuk district, Suphanburi province, Thailand. The 19 samples of soil and rice grain were collected by random sampling in 2015 covered 7 sub-districts. The residual carbofuran and glyphosate in soil and rice grain was quantitative determined based on standard method. It was found that the concentration of carbofuran was found in the range of ND-0.0512 µg/kg and ND-0.0865 µg/kg for soil and rice grain, respectively. Glyphosate was found in the range of ND-0.2632 µg/kg and ND-0.2244 µg/kg for soil and rice grain, respectively. The residual levels of carbofuran and glyphosate in soil and rice grain depended on a spray period time, their decomposition and their concentration usage. The residual levels of carbofuran and glyphosate did not significantly quantitative correlation between soil and rice grain for this study area.

Removal of Phosphate from Wastewater Using Carbonized Filter Cake

The aim of this work was to study the potential of the agricultural waste byproduct as a low-cost adsorbent for removal of phosphate ion (PO43-) from synthetic wastewater. The simple preparation of carbonized filter cake (CFC) was performed at 550°C. CFC was also characterized using FTIR, X-ray fluorescence analysis. The adsorptive parameters of batch experiment, such as pH of solution, dosage and contact time were systematically studied in order to the optimization condition. The optimum conditions of pH, contact time and adsorbent dose were to be 6, 60 min, and 2 g/L, respectively. The Langmuir and Freundlich isotherms were used to calculate the adsorption parameters that was able to describe the equilibrium isotherm and adsorptive mechanism. The maximum monolayer adsorption capacity of CFC was estimated as 20.32 mg/g. The optimized condition was applied for phosphate removal from synthetic wastewater. The achieved phosphate removal efficiency from synthetic wastewater sample was to be 92.4%. Filter cake is a low-cost byproduct of sugar cane but it can also highly effective remove phosphate ion from aqueous solution. The modification of filter cake surface via chemical reaction as a new adsorbent in order to increase surface sites and high affinity with phosphate ion will also be further studied.

Determination of Contaminated Heavy Metals in Lacquer Thinner

The aim of this work needed to discover the problem of lacquer thinner products claimed with dissatisfying the quality of coating and color appearance. The trace metals produced cans was focused on release to solvents. The contaminated trace metals including Fe, Sn, Cu, and Zn in lacquer thinner were also determined by atomic absorption spectrometry (AAS). The lacquer thinner samples were simply carbonized to be ashes by furnace muffle at 550°C for 8 hours. The carbonized ashes were then also digested by conventional wet digestion with concentrated nitric acid until a clear solution was archived. Twenty samples of lacquer thinner were achieved from the paint manufacturer. The content of Fe, Sn, Cu, and Zn was found in the range of 0.0631-77.190 mg/kg, ND-12.613 mg/kg, ND-1.4679 mg/kg, and ND-0.4028 mg/kg, respectively. The result of high concentration of Fe related to the appearance of lacquer thinner color. The evidence of released heavy metals in the ashes of lacquer thinner samples was evaluated by X-ray fluorescence technique. The result of this work was concluded that the contaminated trace metals in the suspected lacquer thinner samples were leached from the metallic package.

Novel Visual Detection of Mercury(II) Ion Based on In Situ Deposited Gold Nanoparticles

In this report, we present a new method for visual and colorimetric detection of Hg (II) ion by using in-situ composited gold nanoparticle (GNP). GNP was formed in one step at room temperature, using NaBH4 as reducing agent incorporated with 2-[5-(2-aminoethylsulfanyl)-pentylsulfanyl]-ethylamine (5-AEPE) as a stabilizer. A 5-AEPE ligand displayed an effective stabilizer for preventing the aggregation of gold nanoparticle in the absence of Hg (II) ion, showing a rose-red color. On the other hand, in the presence of Hg (II) ion, reduced Hg (0) can also deposit on the surface of gold nanoparticle, resulting solution turn to purple and blue immediately. Based on naked eye detection optimization, 125 μM Au (III), 0.6 mM 5-AEPE, 0.8 mM NaBH4 and 0.1%(v/v) Triton X-100 was achieved. By measuring at a wavelength of 680 nm, absorbance values increased linearly as two levels of concentration of Hg (II) ion range of 0.125-2.5 μM (low) and 2.5-15 μM (high). This method offer advantage of simplicity, rapidity, cost effectiveness and no requirement of any sophisticated instruments. Moreover, this method has several potential advantages as optical sensor, especially no as-prepared gold nanoparticle synthesis and shorter observation time.

Adsorptive Removal of Lead(II) Ions from Aqueous Solution onto Chemical Modified Autoclaved Aerated Concrete

An autoclaved aerated concrete (ACC) was chemically modified with manganese oxide (MnO-ACC) for investigate as a high effective adsorbent for removal of lead ions from aqueous solution. The precipitation reaction of manganese oxide was easily done under a high basic solution, resulting manganese oxide in a micron scale occupy on the surface of ACC. The maximum removal efficiency of lead ions using MnO-ACC was obtained under a function of pH 7, adsorbent dosage of 5 g/L, equilibrium time of 15 min. The experimental data were analyzed by commonly adsorption models. The Langmuir adsorption isotherm model is more suitable with a good correlation coefficient of R2=0.99 than the Freundlich model. The maximum monolayer adsorption capacity (qmax) of MnO-ACC was found to be 43.22 mg g−1 in which higher adsorptive capable than unmodified ACC by about 10 times. Based on kinetics study, the adsorption of lead ions onto MnO-ACC followed a pseudo second-order model with a good correlation coefficient of R2=0.99.

Defluoridation of Groundwater Using Raw Material of Autoclaved Aerated Concrete

A batch process of defluoridation using raw material of autoclaved aerated concrete (AAC) was studied under optimum conditions. The parameters of adsorption method, such as pH, adsorbent dose and contact time were optimized under batch experiments. SPADNS method was used to quantitatively evaluate the residual fluoride concentration. Under optimum conditions, pH of solution, adsorbent dose and contact time was to be 7, 0.1 g/10 mL and 60 min, respectively. The amount of defluoridation was found to be 3.23 mgF-/gACC. Deflouridation capacity of AAC can be explained on the basis of the chemical interaction of fluoride with the metal oxides under suitable pH conditions. The adsorption process was found to follow first order rate mechanism as well as Freundlich isotherm.