Attenuation of Heavy Metals from Waste Oil-Based Drilling Mud using Locally Produced Coconut Shell-Based Activated Carbon

Abstract

Most toxic Heavy Metals (HM) persist in oil-based mud and ecosystem for many decades after the application of mud for drilling oil and gas wells. This study assessed the attenuation of such heavy metals from waste oil-based mud using activated carbon produced locally. The oil-based mud analysed presented variable levels of Iron (Fe), Copper (Cu), Nickel (Ni), Potassium (K), Arsenic (As), Chromium (Cr), Manganese (Mn) and Zinc (Zn). Adsorption is a highly effective means of separation to remove a wide range of pollutants in waste streams. Coconut shell activated carbon (CS-AC) was locally produced to remove heavy metals from the waste oil-based mud to encourage value addition to waste. The adsorption data was fitted to Langmuir and Freundlich isotherm model using linear regression analysis. The data was more fitted to the Langmuir isotherm as indicated by the high goodness of fit values (R²). To reduce the heavy metal concentrations below threshold levels optimum CS-AC dosage required for Fe, Cu, Ni, K, As, Cr, Mn and Zn is 5 g/l of CS-AC for a contact time of 30 minutes. The characterization of the produced carbons shows good results comparable to other commercial activated carbons. CS-AC is a viable and economical product for the removal of toxic heavy metals from waste oil-based mud before disposal.