PRODUCED WATER

The continuous discharge of poorly treated produced water from oilfields is a major cause of environmental degradation in the Niger Delta. This study explores a practical, low-cost solution by evaluating the effectiveness of locally sourced Nigerian clays from Ogba River (AG) and Gelegele River (GE) as natural adsorbents for removing heavy metals from real produced water. The clay samples were processed through washing, sun-drying, and chemical activation using a 2M hydrochloric acid solution to enhance their natural properties. We then conducted a series of laboratory batch experiments to test how well these activated clays could remove Iron (Fe) and Copper (Cu) from the water. The study specifically examined how the amount of time the clay was in contact with the water influenced its cleaning power, and we used kinetic and isotherm models to understand the speed and underlying mechanism of the removal process. The results demonstrated that both treated clays were effective, but their performance was highly specific to the metal and the clay's origin. For iron removal, the GE clay showed a slightly higher final efficiency (65.3%) and capacity (0.0243 mg/g) than the AG clay (63.7%, 0.0237 mg/g). In contrast, for copper, the AG clay was markedly superior, achieving 88.5% removal compared to the GE clay's 73.1%. Kinetic studies revealed a clear difference in the removal mechanisms: the adsorption of copper onto both clays was best described by the Pseudo-First-Order model, indicating a physisorption process. However, the adsorption of iron onto the AG clay followed the Pseudo-Second-Order model, suggesting a stronger, chemisorption-driven mechanism. When analyzing the equilibrium data, we found that the classic Langmuir and Freundlich isotherm models yielded unrealistic parameters, highlighting their limitation for accurately describing adsorption in such a complex, low-concentration effluent like real produced water. In conclusion, this work confirms that simple, acid-activated local clays are a viable and sustainable material for cleaning heavy metals from produced water. The findings, particularly the distinct kinetic behaviors, are crucial for designing a treatment process. To move this solution forward, we recommend that future research focuses on testing these clays in continuous-flow pilot systems, conducting a detailed cost-benefit analysis, and exploring how to integrate this clay-based polishing step into existing treatment setups in the Niger Delta.