Locust bean husk (LBH) activated with H3PO4 was used as an adsorbent to remove Pb2+ and Ni2+ from aqueous solution. The effects of varying initial metal ion concentration and adsorbent dose on the adsorption capacity were identified through laboratory experimental investigations. An equilibrium adsorption experiment at ambient temperature was carried out and the experimental data of adsorption fitted into Langmuir and Freundlich adsorption models. The result showed that the amount of metal ion adsorbed onto activated LBH increases with an increase in the initial metal ion concentration. In the given time duration of 2hours and at the initial metal ion concentration of 100ppm, Pb2+ and Ni2+ showed their highest uptake value of 19.85mg/g(79.4%) and 11.10mg/g(57.1%) respectively. For the effect of adsorbent dosage, the maximum adsorbent capacity was at a dosage of 0.8g, recording adsorption capacity of 4.07mg/g for Pb2+ and 2.94mg/g for Ni2+. Langmuir model having higher R2 values of 0.961 and 0.952 for Pb2+ and Ni2+ respectively fitted the equilibrium adsorption data better than the Freundlich model for the two metals.
