Khemarath Osathaphan

Chulalongkorn University, Krung Thep, Bangkok, Thailand

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Publications (19)32.55 Total impact

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    ABSTRACT: Free cyanide (CN(-)) and metal-cyanide complexes (tetracyanonickelate(II)), Ni(CN)4(2-) and hexacyanocobaltate(III)), Co(CN)6(3-) are common constituents of effluents of mining, coal gasification, and petroleum refining. This article presents the degradation of Ni(CN)4(2-) and Co(CN)6(3-) by ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) in alkaline media. The effect of pH (9.0-11.0) and reactant molar ratios on the degradation of the cyanide complexes was investigated. The removal of Ni(CN)4(2-) ion in 200 min was found to be > 90% at pH 9.0; forming cyanate (NCO(-)) ions as the stoichiometric products ([Fe(VI)]:[Total CN(-)] = [Fe(VI)]:[NCO(-)] ≈ 1.0). The degradation efficiency decreased with an increase in pH from 9.0 to 11.0. Comparatively, the Co(CN)6(3-) ion could be degraded only up to 10% in 200 min at pH 9.0 and the final oxidized products were nitrite and nitrate ions. The oxidation efficiency of removing Co(CN)6(3-) did not vary significantly with pH. Fe(VI) consumptions as a result of the oxidation of free cyanide and metal-cyanides and their products are compared and discussed.
    Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 10/2014; 49(12):1380-4.
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    ABSTRACT: Knowledge of sorption and transport of heavy metals in soils in the presence of other metals is crucial for assessing the environmental risk of these metals. Competitive sorption and transport of four metals, Pb(2+), Ni(2+), Zn(2+), and Mn(2+), were investigated using multi-metal column experiments with lateritic soils obtained from a gold mine impacted by acid mine drainage. Based on Pb(2+) breakthrough time for single-metal system at a pH of approximately 5, the sorption capacity of Pb(2+) was estimated to be higher in lateritic soil than the other metals. For multi-metal systems, the estimated retardation factors for the metals from highest to lowest were: Pb(2+)>Zn(2+)∼ Ni(2+)>Mn(2+), suggesting the mobility of metals through lateritic soil for a multi-metal system would be in the order of Mn(2+)>Ni(2+)∼ Zn(2+)>Pb(2+). For binary and multi-metal systems, the estimated sorption capacities of individual metals were found to be lower than the sorption capacities in single metal system - indicating possible competition for sorption sites. Mass recoveries estimates showed that the sorption of metals was more reversible under competitive multi-metal systems than in single metal systems.
    Journal of hazardous materials 06/2011; 190(1-3):391-6. · 4.14 Impact Factor
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    ABSTRACT: a b s t r a c t Knowledge of sorption and transport of heavy metals in soils in the presence of other metals is crucial for assessing the environmental risk of these metals. Competitive sorption and transport of four metals, Pb 2+ , Ni 2+ , Zn 2+ , and Mn 2+ , were investigated using multi-metal column experiments with lateritic soils obtained from a gold mine impacted by acid mine drainage. Based on Pb 2+ breakthrough time for single-metal system at a pH of approximately 5, the sorption capacity of Pb 2+ was estimated to be higher in lateritic soil than the other metals. For multi-metal systems, the estimated retardation factors for the metals from highest to lowest were: Pb 2+ > Zn 2+ ∼ Ni 2+ > Mn 2+ , suggesting the mobility of metals through lateritic soil for a multi-metal system would be in the order of Mn 2+ > Ni 2+ ∼ Zn 2+ > Pb 2+ . For binary and multi-metal systems, the estimated sorption capacities of individual metals were found to be lower than the sorption capacities in single metal system – indicating possible competition for sorption sites. Mass recoveries estimates showed that the sorption of metals was more reversible under competitive multi-metal systems than in single metal systems.
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    ABSTRACT: This study investigated the effects of pH on the transport of Pb2+, Mn2+, Zn2+ and Ni2+ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves (BTCs) of bromide (Br-) with CXTFIT model suggested that physical non-equilibrium processes were absent in the columns. The heavy metal BTCs were, however, asymmetrical and exhibited a tailing phenomenon, indicating the presence of chemical non-equilibrium processes in the columns. The retardation factors of Pb2+ were the largest of the four metal ions at both pH 4.0 (33.3) and pH 5.0 (35.4). The use of Langmuir isotherm parameters from batch studies with HYDRUS-1D did not predict the BTCs well. Rather the two-site model (TSM) described the heavy metal BTCs better than the equilibrium linear/nonlinear Langmuir model. The fraction of instantaneous sorption sites (f) of all four metal ions on the lateritic soil was consistently about 30%-44% of the total sorption sites.
    Journal of Environmental Sciences 01/2011; 23(4):640-8. · 1.77 Impact Factor
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    ABSTRACT: Cyanide is found as free cyanide and metal–cyanide complexes in metal finishing rinse wastewaters. Experiments were performed to seek removal of cyanide in Ni(II)–cyanide and Ni(II)–cyanide–ethylenediaminetetraacetate (EDTA) solutions by the environmentally friendly oxidant, ferrate(VI) (FeO42−, Fe(VI)) as a function of pH (8.0–11.0). Incomplete removal of cyanide in Ni(II)–cyanide solutions (≤60%) was observed at the studied pH range. However, cyanide removal efficiency approached to 100% in Ni(II)–cyanide–EDTA solutions. Formation of Ni(II)–cyanide and Ni(II)–EDTA complexes and relative rates of the reactions of Fe(VI) with various species (water, cyanide, Ni(II)–cyanide, and EDTA) present in solutions were responsible for the variation in removal efficiencies in mixtures at various pH. The oxidation of cyanide by Fe(VI) produced cyanate. Tests using electroplating rinse wastewaters demonstrated that Fe(VI) was highly effective in removing cyanide. KeywordsFerrate–Removal–Metal finishing–Rinse water–Speciation–Rates
    Water Air and Soil Pollution 01/2011; 219(1):527-534. · 1.75 Impact Factor
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    ABSTRACT: The effect of ethylenediaminetetraacetate (EDTA) on the removal of cyanide (CN(-)) from electroplating wastewater was investigated using an electrochemical process. Decay of 100 mg/L CN(-) was carried out as a function of electrical current (I = 0.5-5.0 A) and molar ratios of EDTA to CN(-) (2.6-15.7) at pH 13.0. The experiments showed that electrooxidation of CN(-) follows first-order kinetics with respect to CN(-) ion. The first-order rate constant, k, showed linearity with the applied current (r(2) = 0.99). At a molar ratio of 2.6 ([EDTA]: [CN(-)]) and electric current, I = 2.5 A, the oxidation of CN(-) proceeded by a slower rate than in the absence of EDTA. Under similar conditions, the oxidation rate of cyanide increased at molar ratios ranging from 5.2 to 15.7. Consequently, the energy consumption for the electrooxidation of CN(-) varies with the amount of EDTA present in the solution.
    Journal of Environmental Science and Health Part A 03/2008; 43(3):295-9. · 1.25 Impact Factor
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    ABSTRACT: Removal efficiencies of cyanide and a zinc–cyanide complex in solutions were studied by using an ion-exchange process at pH10.0 and 12.0. An anion-exchange resin, AMBERLITE® IRA-402 Cl, was used to perform packed bed continuous experiments. For the initial 200mg/l cyanide solution, the packed bed gave a cyanide effluent concentration of 0.2mg/l at 80 bed volumes for both pH10.0 and 12.0. Comparatively, in the mixture of 200mg/l cyanide and 100mg/l zinc, packed bed volumes were obtained as 80 and 90 at pH10.0 and 12.0, respectively, to have 0.2mg/l cyanide effluent concentrations. The packed beds were exhausted at 250 and 400 bed volumes for cyanide and zinc–cyanide complex solutions, respectively. Speciation calculations in Zn(II)/cyanide/OH− were used to interpret the results. The exchange capacities of the resin were determined as ∼1.2 and ∼0.9meq/ml resin for cyanide and zinc–cyanide complex solutions, respectively, and were independent of pH in the studied pH range.
    Water Air and Soil Pollution 01/2008; 194(1):179-183. · 1.75 Impact Factor
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    ABSTRACT: The kinetics of the photocatalytic oxidation of cyanide in aqueous TiO2 suspensions was investigated as a function of catalyst loading (0.1–5.0gl−1), air-flow rate (0.2–1.1lmin−1), and the concentration of ethylenediaminetetraacetate, EDTA (0.4–40mM) at pH 13.0. The cyanide oxidation rate did not vary with the TiO2 loading while a slight increase in the degradation rate with an increase in the air-flow rate was found. Cyanate (NCO−) was the only product of the cyanide decomposition. The effect of EDTA on the photocatalytic oxidation of cyanide was examined at different molar ratios of EDTA to cyanide (0.1–10.5) by keeping the initial cyanide concentration at 3.85mM. EDTA retarded the photocatalytic oxidation of cyanide and the decrease in the oxidation rate was not proportional to the molar ratio of EDTA to cyanide. The first-order rate constant, k (min−1) for the oxidation of cyanide in the presence of EDTA may be expressed as k=3.38×10−3×([EDTA]/[CN−])−0.23. A mechanism of the oxidation of cyanide by a photocatalytic process in absence and presence of EDTA is presented.
    Solar Energy - SOLAR ENERG. 01/2008; 82(11):1031-1036.
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    ABSTRACT: Zinc-cyanide complexes are found in gold mining effluents and in metal finishing rinse water. The effect of Zn(II) on the oxidation of cyanide by ferrate(VI) (Fe(VI)O(4)(2-), Fe(VI)) was thus investigated by studying the kinetics of the reaction of Fe(VI) with cyanide present in a potassium salt of a zinc cyanide complex (K(2)Zn(CN)(4)) and in a mixture of Zn(II) and cyanide solutions as a function of pH (9.0-11.0). The rate-law for the oxidation of Zn(CN)(4)(2-) by Fe(VI) was found to be -d[Fe(VI)]/dt=k[Fe(VI)][Zn(CN)(4)(2-)](0.5). The rate constant, k, decreased with an increase in pH. The effect of temperature (15-45 degrees C) on the oxidation was studied at pH 9.0, which gave an activation energy of 45.7+/-1.5kJmol(-1). The cyanide oxidation rate decreased in the presence of the Zn(II) ions. However, Zn(II) ions had no effect on the cyanide removal efficiency by Fe(VI) and the stoichiometry of Fe(VI) to cyanide was approximately 1:1; similar to the stoichiometry in absence of Zn(II) ions. The destruction of cyanide by Fe(VI) resulted in cyanate. The experiments on removal of cyanide from rinse water using Fe(VI) demonstrated complete conversion of cyanide to cyanate.
    Chemosphere 11/2007; 69(5):729-35. · 3.14 Impact Factor
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    ABSTRACT: The sorption and transport of three pharmaceutical compounds (acetaminophen, an analgesic; nalidixic acid, an antibiotic; and 17alpha-ethynyl estradiol, a synthetic hormone) were examined by batch sorption experiments and solute displacement in columns of silica, alumina, and low organic carbon aquifer sand at neutral pH. Silica and alumina were used to represent negatively-charged and positively-charged fractions of subsurface media. Column transport experiments were also conducted at pH values of 4.3, 6.2, and 8.2 for the ionizable nalidixic acid. The computer program UFBTC was used to fit the breakthrough data under equilibrium and nonequilibrium conditions with linear/nonlinear sorption. Good agreement was observed between the retardation factors derived from column model studies and estimated from equilibrium batch sorption studies. The sorption and transport of nalidixic acid was observed to be highly pH dependent, especially when the pH was near the pK(a) of nalidixic acid (5.95). Thus, near a compound's pK(a) it is especially important that the batch studies be performed at the same pH as the column experiment. While for ionic pharmaceuticals, ion exchange to oppositely-charged surfaces, appears to be the dominant adsorption mechanism, for neutral pharmaceuticals (i.e., acetaminophen, 17alpha-ethynyl estradiol) the sorption correlated well with the K(ow) of the pharmaceuticals, suggesting hydrophobically motivated sorption as the dominant mechanism.
    Water Research 05/2007; 41(10):2180-8. · 4.66 Impact Factor
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    ABSTRACT: Mixtures of anionic and cationic surfactants exhibit synergistic behavior as evidenced by low critical micelle concentrations (CMC) of the mixed system, increased surface activity, and improved detergency performance. The adsorption of a single-head anionic surfactant, sodium dodecyl sulfate (SDS), in mixture with a twin-head cationic surfactant, pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD), showed synergism of adsorption onto silica when present at a mixing ratio of 1:3 (cationic-rich), and also demonstrated lower surfactant desorption with water flushing of columns packed with the surfactant-modified media. In addition, the proportion of the mixed surfactants in the admicelles moved from the initial ratio of 1:3 towards equimolar after rinsing the surfactant-modified silica absorbent. The retardation of organic solutes passing through columns packed with modified-silica adsorbent increased nominally three fold for silica modified with mixed surfactants versus single surfactants (retardation factors increase from 4.0 to 12.8 for styrene and from 32.1 to 90.2 for ethylcyclohexane for single and mixed surfactants, respectively). Thus, this study demonstrates that mixed surfactant systems more effectively modified the silica surface than single surfactant systems both in terms of enhanced retardation of organic solutes and in terms of reduced surfactant desorption.
    Water Research 04/2007; 41(6):1343-9. · 4.66 Impact Factor
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    ABSTRACT: Two pure minerals and a hydrophobic medium were selected to study sorption of pharmaceuticals. The sorption of four pharmaceuticals, acetaminophen (analgesic), 17alpha-ethynyl estradiol (synthetic hormone), nalidixic acid (antibiotic), and norfloxacin (antibiotic), was evaluated with silica, alumina, and Porapak P (a hydrophobic medium). Alumina and silica were selected to represent positively charged and negatively charged aquifer mineral surfaces at neutral pH, respectively, while Porapak P was selected to represent the hydrophobic organic content of an aquifer medium. At neutral pH, acetaminophen, the least hydrophobic pharmaceutical, showed no significant sorption to any of the media, while 17alpha-ethynyl estradiol, the most hydrophobic pharmaceutical, showed significant sorption to Porapak P. Nalidixic acid, which has a carboxyl functional group that is anionic at neutral pH, showed significant adsorption to the positively charged alumina. Norfloxacin, with both a carboxyl (anionic) and a piperazynyl (cationic) group, can exist in four forms (neutral, cationic, anionic, and zwitterionic) depending on the aqueous pH. Norfloxacin also showed significant adsorption than nalidixic acid. Both nalidixic acid and norfloxacin adsorbed to silica and Porapak P to a much lower extent. The pH dependence of nalidixic acid and norfloxacin adsorption to silica and alumina was also studied by varying the pH between 4 and 11. The maximum adsorption of nalidixic acid to alumina occurred near its pKa (pH approximately 6), where the combination of cationic alumina and anionic nalidixic produced maximum adsorption. The maximum adsorption of norfloxacin to alumina was observed at pH approximately 7, which was the region where the zwitterionic form dominated. This research demonstrates that the adsorption of ionizable pharmaceuticals is strongly dependent on the system pH, the pharmaceutical properties (pKa and hydrophobicity), and the nature of the surface charge (point of zero charge). For pharmaceuticals that are uncharged at environmentally relevant pH values, the main sorption factor is their solubility or hydrophobicity; for charged forms, ion exchange is also an important adsorption mechanism.
    Water Research 05/2006; 40(7):1481-91. · 4.66 Impact Factor
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    ABSTRACT: This research reports on the adsorption and precipitation of mixtures of anionic and cationic surfactants having single and twin head groups. The surfactant mixtures investigated were: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), in a mixture with the twin-head cationic surfactant pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD)—adsorption was studied on negatively charged silica; and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), and the single-head cationic surfactant dodecylpyridinium chloride (DPCI)—adsorption was studied on positively charged alumina. Whereas the mixed surfactant system of SHDPDS/DPCI showed adsorption on alumina that was comparable to the of SHDPDS alone, the mixed surfactant system of SDS/PODD showed increased adsorption on silica as compared with PODD alone. The adsorption of the SDS/PODD mixture increased as the anionic and cationic system approached an equimolar ratio. Precipitation diagrams for mixtures of single- and twin-head surfactant systems showed smaller precipitation areas than for single-head-only surfactant mixtures. Thus, the combination of single- and double-head surfactants helps reduce the precipitation region and can increase the adsorption levels, although the magnitude of the effect is a function of the specific surfactants used.
    Journal of Surfactants and Detergents 02/2006; 9(1):21-28. · 1.52 Impact Factor
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    ABSTRACT: Mixtures of anionic and cationic surfactants with single and twin head groups were used to solubilized styrene and ethylcyclohexane into mixed micelles and adsolubilize them into mixed admicelles on silica and alumina surfaces. Two combinations of anionic and cationic surfactants were studied: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), with a twin-head cationic surfactant, pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD), and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), with a single-head cationic surfactant, dodecylpyridinium chloride (DPCl). Mixtures of SDS/PODD showed solubilization synergism (increased oil solubilization capacity) when mixed at a molar ratio of 1∶3; however, the SHD-PDS/DPCl mixture at a ratio of 3∶1 did not show solubilization enhancement over SHDPDS alone. Adsolubilization studies of SDS/PODD (enriched in PODD) adsorbed on negatively charged silica and SHDPDS/DPCl adsorbed on positively charged alumina showed that while mixtures of anionic and cationic surfactants had little effect on the adsolubilization of styrene, the adsolubilization of ethylcyclohexane was greater in mixed SHPDS/DPCl systems than for SHDPDS alone. Finally, it was concluded that whereas mixing anionic and cationic surfactants with single and double head groups can improve the solubilization capacity of micelles or admicelles, the magnitude of the solubilization enhancement depends on the molecular structure of the surfactant and the ratio of anionic surfactant to cationic surfactant in the micelle or admicelle.
    Journal of Surfactants and Detergents 02/2006; 9(1):29-37. · 1.52 Impact Factor
  • W. Khongnakorn, K. Osathaphan, S. Khaodhiar
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    ABSTRACT: The objective of this study was to investigate the biotic and abiotic processes that affected benzene transportation in the saturated groundwater layer. The study was performed in the laboratory using synthetic groundwater and soil sample from Maptaput Industrial Estate, Rayong. This study was divided into 3 parts; batch test, column test and computer modeling. The biotic, biodegradation, and the abiotic processes were studied in the batch system. The column experiment was performed to investigate the transport behavior of benzene. The computer program, CXTFIT, with parameters acquired from batch and column experiments was used to simulate the benzene transport behavior. It was found that benzene adsorption followed the linear adsorption isotherm with its coefficient (Kd) of 0.544 cm3/g and the retardation factor of 5.43. The biodegradation rate could be estimated using the firstorder biodegradation rate equation with the degradation rate of 0.0009- 0.0092 per day. The dispersion coefficient estimated from column experiments was 0.0102 cm2/s. The results from computer simulation did not fit the experimental data well. It can be concluded that the transport of benzene was a non-equilibrium transport. It was also found that biodegradation of benzene had significant effect on benzene transportation in saturated groundwater. The simulated transport with biodegradation process fitted the data fairly.
    Songklanakarin Journal of Science and Technology. 01/2004;
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    ABSTRACT: Cyanide and metal–cyanide complexes are common constituents of effluents of mining, petroleum refining, and coal gasification. This paper presents the photocatalytic degradation of free cyanide, Ni(II)-cyanide (Ni(CN)42−), and Co(III)-cyanide (Co(CN)63−) complexes in aqueous TiO2 suspensions. The effect of pH (9.5–12.0), TiO2 loading (0.1–2.0 g/l), and the airflow rate (0.5–2.0 l/min) in a photoreactor on the degradation of the cyanide complexes was investigated. Free cyanide fully converted to cyanate (NCO−) under alkaline conditions. The maximum removal of the Ni(CN)42− ion in 180 min was found to be 90 %; forming CN− and NCO− ions as the major and minor products, respectively. Comparatively, the Co(CN)63− ion could be degraded only up to 30 % in 180 min. The schemes of the photocatalytic oxidation of cyanides are briefly described. The possible causes for differences in degradation of Ni(CN)42− and Co(CN)63− are also discussed. Optimum conditions for efficient removal of Ni(CN)42− and Co(CN)63− ions separately and in mixtures are given.
    Water Air and Soil Pollution 224(8). · 1.75 Impact Factor