الفهرس 
CHAPTER ONE: AIMS AND SCOPE OF RESEARCHOnly 14 pages are availabe for public view
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Abstract
Laboratory investigation of insecticide (diazinon) adsorption onto natural clay was conducted in this study. The following major points can be extracted from the results of this study:
1- The removal of diazinon Increases with lapse of time and attains equilibrium in 180 min.
2- Natural clay has 70.6 % diazinon removal efficiency in comparison with that of activated carbon for the same particle size (500-710 11m).
3- The adsorption isotherms corresponding to the natural clay may be classified as type-L (Giles classification) which suggests a medium affinity of diazinon molecules for the active sites of natural clay surface and also that there is no strong competition from the solvent for adsorption sites.
4- Decrease in particle size of natural clay gave a good improvement in diazinon removal. The adsorption capacity increased from 4.80 mg/g (61.48 %) to 6.0 mg/g (75.92 %)as particle size decreased from 500-710 ~lm to 250-355 11111.
5- The adsorption isotherms have been plotted to obtain the Langmuir, the Freundlich and the Redlich-Peterson parameters. The correlation coefficients obtained from the Freundlich plots were higher than those obtained from the Langmuir and Redlich-Peterson plots.
6- Equilibrium parameter (R) was used to asses the natural of equilibrium for diazinon and the results indicated that the diazinon - natural clay system exhibit favorable adsorption i.e. 0 < R < 1.
7- The external mass-transfer process has been studied with three system
variables, namely, agitation speed, initial diazinon concentration and clay
mass. The external mass-transfer coefficient, Ks, has been found to vary linearly with agitation speed, initial concentration and clay mass according to the following equations:
Ks = 1.62X 10-5 (RPM) 1.1,
Ks = 7.4X 10-3 (m) 1.25
8- The results show that the external mass-transfer may be rate controlling step only for very short time intervals at the beginning of the contacting process.
9- Intraparticle diffusion has been studied on the basis or the same variables
as in the external mass transfer: The macropore rate parameter for intraparticle diffusion, Kr, has been determined and used to correlate experimental data against the system variables. The macropore rate parameter, Kr, has been found to vary linearly with system variables according to the following equations:
F A’t t’ K, = 3.16X 10-3 (I”lPM)1.0’
01’ gl a 1011:”
For Initial Conc. K, = 0.83 (Co) 0.59
For mass: K, = 0.13 (m)1.24
10- By means or the above equations, it has been found that, the intraparticle di ffusion (macropore and micropore) is a major rate controlling step in controlling diazinon removal from aqueous solutions. The kinetic studies showed conclusively that intraparticle di rfusion resistance was predominant in the adsorption process and that external resistance was minimized by the efficient rapid mixing.