| Summary: | The adsorption potential of acid activated carbon prepared from leaves of <i>Juniperus procera</i> to remove Pb(II) and Cr(VI) toxic ions from aqueous solutions was investigated. The effects of solution pH, adsorbent mass, contact time, initial ion concentration and temperature on the biosorption process were studied, and the optimum conditions were determined. Moreover, Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherm models were applied to analyze adsorption data. Thermodynamic parameters for the adsorption processes were calculated. Adsorption was found to be a spontaneous and endothermic process. In addition, kinetic studies revealed a pseudo-first order kinetics biosorption process. The obtained results suggest that acid activated <i>Juniperus procera</i> leaves powder can be used as a cheap, efficient and environmentally friendly adsorbent material with high removal efficiency up to 98% for Pb(II) and 96% for Cr(VI) at 0.80 and 1.00 g/100 mL, respectively. The duration of the process was 100 min and 120 min for Pb(II) and Cr(VI) ions, respectively. The morphology of the of prepared activated carbon was investigated by scanning electron microscope (SEM).
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