Effectiveness of Mangifera Indica Peels for Heavy Metal Adsorption in the Treatment of Produced Water from Niger-Delta Oilfields

Abstract

Abstract Produced water usually contains contaminants such as hydrocarbon fractions, heavy metals, corrosion inhibitors, etc. which are potentially harmful to the environment. Produced water has to be treated to conform to regulatory standards. Treatment techniques that are both robust and cost-effective need to be developed to increase the economic viability of produced water treatment. This research evaluates the effectiveness of mango peels as bio-adsorbents in the treatment of produced water and the effectiveness of modifications made to the mango peels. Produced water samples were obtained from Niger Delta and analysed for heavy metals using atomic absorption spectrophotometry (AAS). In this study, mango peels were washed with distilled water, sun-dried and oven-dried at 80°C. The adsorbent was pulverized and sieved (212 μm). Three batches of adsorbent were prepared: unmodified, 0.2 mol/L NaOH treated and 0.5 mol/L NaOH treated mango peels. Samples were treated with individual batches of adsorbent for up to six hours. Treated samples were analysed with AAS. The adsorption capacity, as well as the removal efficiency, were also determined. Adsorption was assessed using the Langmuir and Freundlich models. For the 0.2 mol/L NaOH adsorbent treatment, the removal efficiency for the metal concentrations (Ni, Pb, Fe, Mn, Cu, and Zn) were found to be 58.33%, 100.00%, 95.00%, 75.00%, 56.00% and 98.67% respectively, while the removal in 0.5 mol/L NaOH adsorbent treatment for the heavy metals were 95.83%, 100.00%, 93.00%, 90.79%, 68.00%, 97.35% respectively. The unmodified mango peels proved to be ineffective because the metallic concentration in the produced water increased after treatment (except for Lead and Copper). The modified variants proved to be effective as they reduced metallic concentration. The 0.5M NaOH modified variant outperformed the 0.2M NaOH modified variant. This shows that pH and contact time affect the adsorption process.