Removal of heavy metals by using activated carbon produced from cotton stalks
El Zayat, Mohamed
Utilization of agricultural waste to produce valuable products has opened opportunities in Egypt to minimize serious public health risks from exposure to dangerous fumes that come from burning the agricultural wastes in open fields. In this study, activated carbon produced locally from cotton stalks was examined for the removal of target heavy metal contaminants from water and waste water. Adsorption studies conducted in completely mixed batch reactors showed the ability of the produced activated carbon to remove heavy metals, namely lead, cadmium and copper, from aqueous solutions in a pH range below that of precipitation and with high uptake capacity after an equilibrium reaction time of 72 hours. The surface titration experiment indicated a negative surface charge of the produced activated carbon in solution at pH as low as 6, meaning that electrostatic attraction of the divalent heavy metals can occur below the pH required for precipitation. Continuous flow columns studies showed a good affinity of the produced carbon for the target heavy metals compared to other commercial adsorbents, revealed by the number of bed volumes treated until breakthrough. The highest adsorption capacity was for lead, followed by copper and then cadmium. Multicomponent metal adsorption experiments indicated a competition for the available surface sites. Adsorption capacities in the mixture were reduced from their single-solute values for all metals.
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