Effect of Water Hardness and pH on Adsorption Kinetic of Arsenate on Iron Oxide
The adsorption of arsenate on iron oxide particles was studied as a function of pH and hardness concentrations. The surface morphology of iron oxide particles was found to be rough and irregular. The major chemical compositions on iron oxide particles included Fe2O3 (96%). The optimum solution pH for adsorption was found to be 8.0. The equilibrium of arsenic concentration was reached after 30 min of contact time. The adsorption capacity was 124 µg/g. The adsorption isotherm was found to be either Langmuir or Freundlich. The adsorption kinetic was fitted well with pseudo-second order reaction with a rate constant (k2) ranging from 0.0062 to 0.0801 g/µg.min for 2 g to 20 g of iron oxide particles used. Calcium and magnesium concentrations did not significantly affect the adsorbed concentration of arsenic at equilibrium.