Optimizing Conditions For Preparing Activated Carbon From Avocado Seeds For Best Adsorption Of Lead Ions From Wastewater

ABSTRACT

Pollution of water bodies by heavy metals and biomass wastes is increasing as Kenya becomes industrialised. The conventional methods of cleaning wastewater are expensive. They include ion exchange, bio sorption, solvent extraction, precipitation among others. New and cheaper technologies are emerging that utilizes locally available biomass inform of activated carbon. The aim of this study was to determine the best carbonisation and activation conditions of temperature, time and phosphoric acid concentration using avocado seed wastes for removal of Pb2+ ions from wastewater. It also compared the adsorption efficiency and capacity of the activated and the inactivated carbon from the same material. The adsorption studies were done using batch experiments by investigating the effect of metal ion concentration, contact time, adsorbent mass and pH. The data obtained from optimization of conditions were found to be 600 ºC, 5 hours and 50 % H3PO4 acid for maximum adsorption of Pb2+ ions using 80 mg/l solutions. The data obtained from adsorption studies for the two adsorbents were found to fit best into Freundlich isotherm with R2 value of 0.917 and 0.921 and adsorption capacities of 2.24 mg/g and 1.66 mg/g for activated and inactivated carbon respectively. From the batch adsorption experiments, the activated carbon showed a higher percentage remova l of Pb2+ ions compared to inactivated carbon. There being a great significance difference between the two adsorbents, the AC was found to be a better adsorbent than the IC. Thus maximizing activation conditions would produce a better activated carbon from avocado seeds that would be used to remove heavy metal ions from aqueous solutions and other industrial or domestic applications. It also eliminates the problem of agricultural wastes accumulating in our environment.