Effect of Water Hardness and pH on Adsorption Kinetic of Arsenate on Iron Oxide

摘要

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 Fe_(2)O_(3) (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 ( k_(2) ) 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.