Abstract
Peanut shells-derived activated carbons (ACPNS) with different chemical characteristics, appropriate for the removal of methomyl pesticide in aqueous solutions are prepared. The steam activated carbon is obtained from the carbonized peanut shells in the presence of nitrogen in the temperature range from 973 to 1173K. The carbonized peanut shells are, further, chemically activated using NaOH and ZnCl2. The structure of the ACPNS was characterized by N2 adsorption at 77K, scan electron microscopy and FTIR. B.E.T methods are used to deduce the effective surface areas. The parameters (such as initial pH, temperature, etc) affecting the adsorption capacity of peanut shells-derived activated carbons toward methomyl removal from aqueous solutions are investigated using batch experiments. The study of kinetic models including pseudo first order and pseudo second-order are carried out. Adsorption isotherms are investigated. Equilibrium adsorption data fitted the Langmuir adsorption isotherm well with R2> 0.9980. The maximum adsorption capacities of peanut shells-derived activated carbons for the removal of methomyl, are calculated. The thermodynamic parameters including ΔG°, ΔH° and ΔS° for the adsorption processes of methomyl on the ACPNS were calculated, and the negative value of ΔG° indicated the spontaneous nature of adsorption. The prepared peanut shells derived activated carbons are successfully applied to the removal of methomyl pesticide from different water samples with a recovery % > 95 and a RSD< 3%. The mechanism of adsorption is proposed.
Highlights
Pollution of ground and surface water is considered as the most important problem can threaten human, animals, plants and aquatic organisms
The textural properties of solids are conventionally determined from the adsorption of nitrogen at 77K and the adsorption data are usually analyzed by the application of the BET equation [31,32]
The steep slope at initial methomyl concentrations is a desirable feature of the sorption system and the results indicates that the ACPNS are efficient adsorbents for methomyl
Summary
Pollution of ground and surface water is considered as the most important problem can threaten human, animals, plants and aquatic organisms. It is a highly toxic carbamate insecticide first registered in 1968 by the EPA as a "Restricted use pesticides" and is used on a wide variety of crops It is a cholinesterase inhibitor and is often most effective against pests that have developed a resistance to organophosphates [5]. Ultrasound combined with photo-Fenton treatment [12], electro dialysis membranes [13], filtration, ozonation [14], reactions with oxidants such as free radicals, disinfection, floatation [15], preconcentration [16] and adsorption [17] Amongst these techniques, adsorption is considered as the most effective and widely used for control of taste and odor as well as removing synthetic organic compounds and wide range of pollutants from wastewater and water supplies [18,19]. There are many different adsorbents can be used for water treatment and purification such as silica gel [20], activated alumina [21], zeolites [22], polymers [23] & resins [24], clay [25] and activated carbon [26]
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