Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash
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741 Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash Dhirendra Singh Department of Soil Science, Faculty of Agriculture, Government Post Graduate School, Sawai Madhopur, Rajasthan 322001, India. (Received 9 August 2000; accepted 8 September 2000) ABSTRACT: The adsorption thermodynamics of oxamyl on fly ash at 10ºC, 25ºC and 50ºC have been studied via the relevant adsorption isotherms, Freundlich constants (K F and 1/n), distribution coefficient (K d ) and other thermodynamic para- meters. The data were well fitted by the Freundlich equation (r 2 > 0.98) and yielded S-shaped isotherms at all the temperatures studied. Thermodynamic parameters such as the thermodynamic equilibrium constant (K 0 ), the standard free energy change (DG 0 ), the standard enthalpy change (DH 0 ) and the standard entropy change (DS 0 ) have been calculated as a means of predicting the nature of the adsorption process. INTRODUCTION Huge quantities of fly ash, an industrial waste product, are produced in India by coal-based power stations as well as steel plants. It has been reported that fly ash has an adsorptive potential which may help in the removal of organic acids (Ahmed et al. 1983) and other toxic ions from water (Nadar and Parvathy 1982; Prabhu et al. 1981). Eiceman and Vandiver (1983) reported that poly- cyclic aromatic hydrocarbons are adsorbed on fly ash and it has also been used effectively for the neutralization of soil acidity (Adriano 1980; Elseewi et al. 1980; Lal et al. 1996a) as well as increasing the availability of certain plant nutrients in soil (Jones and Straughan 1978; Elseewi et al. 1981; Druzina et al. 1983; Maiti et al. 1990; Sikka and Kansal 1994; Lal et al. 1996b; Oswal et al. 1997). The treatment of soils with fly ash has led to a reduction in the population of plant parasitic nematodes (Haq et al. 1985). Oxamyl [N,N-dimethyl-2-methylcarbomoyloxyimino-2-(methylthio)acetamide] is a broad spec- trum, non-volatile nematicide which has been widely used in agriculture in India for a long time for the control of nematode problems which have developed in crop production. Its structure can be represented as: (CH 3 ) 2 N CO C=NO CO NH CH 3 ½ SCH 3 The excessive use of oxamyl creates a source of pollution in soil, surface and ground water. Considerable work has been undertaken on the factors affecting the adsorption of pesticides and organic chemicals in soils (Bailey and White 1970; Mortland 1970). However, to date, only a few experimental studies have focused on the adsorption of oxamyl on soils (Gerstl 1984; Bansal 1982; Singh et al. 1981; Bansal and Gupta 1998). Indeed, no record appears in the literature of studies pertaining to the adsorption of oxamyl on fly ash when both have been applied to soil in order to reduce the nematode population. For this reason, the present investigation has been undertaken to study the thermodynamics of oxamyl adsorption on fly ash in an attempt to understand the role of fly ash in removing pollutants.
Transcript of Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash
741
Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash
Dhirendra Singh Department of Soil Science, Faculty of Agriculture, Government Post Graduate School, Sawai
Madhopur, Rajasthan 322001, India.
(Received 9 August 2000; accepted 8 September 2000)
ABSTRACT: The adsorption thermodynamics of oxamyl on fly ash at 10ºC,25ºC and 50ºC have been studied via the relevant adsorption isotherms, Freundlichconstants (K
F and 1/n), distribution coefficient (K
d) and other thermodynamic para-
meters. The data were well fitted by the Freundlich equation (r2 > 0.98) and yieldedS-shaped isotherms at all the temperatures studied. Thermodynamic parameterssuch as the thermodynamic equilibrium constant (K0), the standard free energychange (DG0), the standard enthalpy change (DH0) and the standard entropy change(DS0) have been calculated as a means of predicting the nature of the adsorptionprocess.
INTRODUCTION
Huge quantities of fly ash, an industrial waste product, are produced in India by coal-based powerstations as well as steel plants. It has been reported that fly ash has an adsorptive potential whichmay help in the removal of organic acids (Ahmed et al. 1983) and other toxic ions from water(Nadar and Parvathy 1982; Prabhu et al. 1981). Eiceman and Vandiver (1983) reported that poly-cyclic aromatic hydrocarbons are adsorbed on fly ash and it has also been used effectively for theneutralization of soil acidity (Adriano 1980; Elseewi et al. 1980; Lal et al. 1996a) as well asincreasing the availability of certain plant nutrients in soil (Jones and Straughan 1978; Elseewi etal. 1981; Druzina et al. 1983; Maiti et al. 1990; Sikka and Kansal 1994; Lal et al. 1996b; Oswal etal. 1997). The treatment of soils with fly ash has led to a reduction in the population of plantparasitic nematodes (Haq et al. 1985).
Oxamyl [N,N-dimethyl-2-methylcarbomoyloxyimino-2-(methylthio)acetamide] is a broad spec-trum, non-volatile nematicide which has been widely used in agriculture in India for a long timefor the control of nematode problems which have developed in crop production. Its structure canbe represented as:
(CH3)
2�N�CO�C=NO�CO�NH�CH
3
½ SCH
3
The excessive use of oxamyl creates a source of pollution in soil, surface and ground water.Considerable work has been undertaken on the factors affecting the adsorption of pesticides andorganic chemicals in soils (Bailey and White 1970; Mortland 1970). However, to date, only a fewexperimental studies have focused on the adsorption of oxamyl on soils (Gerstl 1984; Bansal 1982;Singh et al. 1981; Bansal and Gupta 1998). Indeed, no record appears in the literature of studiespertaining to the adsorption of oxamyl on fly ash when both have been applied to soil in order toreduce the nematode population. For this reason, the present investigation has been undertaken tostudy the thermodynamics of oxamyl adsorption on fly ash in an attempt to understand the role offly ash in removing pollutants.
