ASENI CLAY

Aseni clay was obtained from Kogi State, Nigeria. Adsorption studies of Iron (III) ions (Fe3+) was carried out on the clay and Atomic Absorption Spectrometry (AAS) was employed in analysis of equilibrium concentration of Fe3+ions in aqueous solution. Batch experiment involving varied initial concentration adsorbent dosage, contact time and pH were conducted. quilibrium data showed that as initial Fe3+ concentration increased from 10 to 50 mg·L-¹ the adsorption capacity increased from 0.96 to 3.62 mg·g-¹ while percentage removal decreased from 95.7% to 72.4%, indicating progressive site saturation at higher loadings. Increasing the adsorbent mass from 0.2 to 1.0 g (per 100 mL) improved removal efficiency from 57.67% to 83.23%, demonstrating the positive effect of greater available surface sites. Contact time produced rapid initial uptake, with the amount adsorbed rising from 22.97 mg·L -¹ at 5 min to 26.03 mg·L-¹ at 120 min and percentage removal from 76.57% to 86.77%, indicating approach to equilibrium within the experimental timeframe. pH trials (4–9, initial concentration 100 mg·L-¹) returned very high removal (>99%); however, experimental notes indicated Fe hydrolysis/precipitation during base addition which likely affected measured concentrations and must be considered when interpreting pH-dependent results. Equilibrium modelling revealed strong fits to both Langmuir and Freundlich isotherms, with a marginally better fit to the Freundlich model (R² = 0.9815 versus Langmuir R² = 0.979), consistent with adsorption on a heterogeneous surface. Kinetic analysis showed that the pseudo-second-order model provided an excellent description of the adsorption behaviour (linear t/qt versus t relationship; very high R²), suggesting that chemisorption and surface complexation are dominant rate-controlling steps. The findings indicate that Aseni clay is a viable, low-cost adsorbent for Fe +³ removal under the tested laboratory conditions, especially at low to moderate contaminant concentrations, while highlighting the need for care in pH control to avoid precipitation artefacts and for further work on regeneration and real-waste testing.