Figure 7. Effect of phosphate concentrations (0–1 mM) on the adsorption of As(V) (a) and As(III) (b) using uncalcined and calcined Fe₃O₄-HBC composite.

Experiment conditions: adsorbent dose  = 0.02 g 100 mL⁻¹, temperature  = 25±0.8°C, agitation speed  = 150 rpm, initial concentration  = 100 µg L⁻¹, contact time  = 14 h).