Environmentally friendly method is reported for the synthesis of nanoscale zero-valent iron using plant extract as a reducing agent. The biosynthesized nanoparticles were characterized using FESEM, EDS, XRD, FT-IR and TGA. A factorial design analysis was conducted to determine the influence of different factors affecting the removal of arsenic (As) and selenium (Se) from water using biosynthesized nanoscale zero-valent iron. The factors investigated include; pH, adsorbent dosage, initial concentration, contact time and shaker speed. It was observed that the effect of adsorbent dosage was most significant for the removal of arsenic from water. At 95% confidence level, dosage variation showed more than 30% increase in removal efficiency when it was varied between 10 mg and 100 mg. About 95% of arsenic removal was recorded using 100 mg adsorbent at solution pH 3. For selenium removal, the effect of adsorbent dosage showed a relatively positive influence. About 90% removal efficiency was recorded at Se solution of pH 3 which signifies the applicability of the material for real water samples. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.