Fig. 5

(a) Point of zero charge of rGO@Fe₃O₄ nanocomposites and (b) the effect of pH of the medium (n = 3) (The constant parameters used in the medium’s pH value optimization: 8.0 mL sample volume, 30 mg/L of Cr(VI) standard solution, 100 mg adsorbent, 30 min of mechanical shaker mixing, agitation speed 250 rpm).