Comparative Performance of Locally Available Adsorbent Materials for Petroleum Hydrocarbon Removal from Contaminated Groundwater in Akwa Ibom State

Groundwater contamination by petroleum hydrocarbons in oil-producing communities of Akwa Ibom State, South South Nigeria, demands practical and affordable remediation technologies suited to local resource availability. This study comparatively evaluates the performance of four locally available adsorbent materials, including coconut shell biochar, rice husk ash, clay minerals, and peat, for the removal of total petroleum hydrocarbons from contaminated groundwater samples collected from wells in the Ikot Abasi area. Adsorbent materials were characterised by BET surface area analysis, scanning electron microscopy, and FTIR spectroscopy. Batch adsorption experiments were conducted at varying contact times, adsorbent dosages, initial hydrocarbon concentrations, and pH values. Adsorption isotherm data were modelled using Langmuir and Freundlich equations, and regeneration potential was assessed over five adsorption-desorption cycles. Results show that coconut shell biochar exhibited the highest petroleum hydrocarbon removal efficiency at 92 percent under optimised conditions, attributed to its significantly larger BET surface area compared to the other materials. Rice husk ash achieved 78 percent removal and showed the best regeneration stability over five cycles. Clay minerals demonstrated lower efficiency but remained competitive considering zero production cost. Combining coconut shell biochar with clay minerals in a column arrangement yielded near-complete effluent treatment, suggesting potential for a practical field-deployable system. Keywords: adsorption, petroleum hydrocarbons, groundwater, biochar, Akwa Ibom State