The Adsorption Studies for the Removal of Lead (Pb2+) from Paint Industrial Wastewater using Avocado Seed Activated Carbon (ASAC)

Abstract

The rapid increase in industrial activities in Nigeria has led to the high contamination of water bodies with heavy metals such as Lead, Cadmium, Zinc etc from wastewater disposal. Previous techniques adopted for this wastewater treatment such as ion exchange, biosorption, solvent extraction and precipitation etc are highly expensive and capital intensive; hence, the need for cheaper technologies that utilizes locally available biomass as a precursor for the preparation of activated carbon. This study aims to utilize avocado seed for the production of activated carbon to treat paint industrial wastewater containing heavy metals such as Lead (Pb2+) and to evaluate the adsorption isotherm and kinetic models that best fit the equilibrium data obtained from the batch adsorption experiment. The avocado seed activated carbon (ASAC) was prepared by carbonizing the sample at a temperature of 700 °C and activating it with a 30 % v/v Concentration of H3PO4 acid at a temperature of 500 °C for 6 hours in a muffle furnace. The batch adsorption studies were done by investigating the varying effect of metal ion concentration (0.5-3.0 mg/L), contact time (15-180 mins) and adsorbent dosage (0.5-3.0 g). The data obtained were analysed using six adsorption isotherms such as Langmuir, Freundlich, Temkin, Toth, Sips and Redlich-Peterson methods. Freundlich isotherm model with an R2 value of 0.94 and adsorption capacity of 0.1965 mg/g showed the highest percentage removal of Lead (Pb2+) to be > 97 %. The kinetic studies revealed that the experimental data fitted well to the pseudo-first-order model with a high correlation coefficient of 0.980 when compared to other models like pseudo-second-order, intra-particle diffusion and Boyd model, thus; signifying that the adsorption’s mechanism was physiosorption. Thus, optimum activation conditions would produce higher activated carbon from avocado seeds that could be used for the removal of heavy metal ions from industrial wastewater, which will aid in eliminating the challenge of agricultural waste accumulation in the environment.