Iron oxide-modified pervious concrete filter for lead removal from wastewater

The effects of partially adding iron-oxide-modified aggregate to OPC-based pervious concrete filter on the mechanical properties, heavy metal removal and leaching were investigated. Up to 10% of both coarse and fine aggregates were coated with iron oxide and filters (IOMA-C, coarse alone modified, IOMA-F fines alone modified and IOMA-CF) were prepared. Compressive strengths of the concrete improved while the permeability decreased by up to 13%. Simulated wastewater containing 15 ppm lead Pb (II) ions was passed through the control and IOMA-filters for 8 h under trickling water head. Iron-oxide-modified filter (IOMA-CF) showed maximum removal efficiency of 99.1% (87.3% for control). Desorption studies with 1M HNO3 indicated that iron oxide complexed the Pb (II) ions more irreversibly, reducing the extent of their leaching. Batch studies were carried out at 1 g/L adsorbent loading (crushed control and IOMA-CF) with solutions containing 5 to 25 ppm Pb (II). Langmuir isotherm fit adsorption results on both the control and IOMA-CF systems while Temkin isotherm was the best fit for IOMA-CF, indicating the stronger, more irreversible chemisorption of Pb (II) on iron oxide. Theoretical adsorption capacities based on Langmuir isotherms for the control and IOMA-CF were 18.21 and 20.66 mg/g, respectively. Kinetics studies indicated that a pseudo second order kinetics model fit the results of all systems with a slightly slower rate of adsorption than the control system. Effects of pH and coexisting ions have been examined. These preliminary results indicate the potential of applying pervious concretes either as water filters or pretreatment units.