## 1 Introduction  
Heavy metals with density more than 5.0 g/cm\({}^{3}\)[1] bring significant impacts on the environment and human. Pb\({}^{2+}\), Cu\({}^{2+}\), and Zn\({}^{2+}\) are typical heavy metals that commonly existed in urban runoff and are difficult to be degraded. Heavy metals prefer to accumulate in organisms and much of them are known to be carcinogenic and highly toxic [2]. They have attracted great attention due to their potential hazards to ecosystems and human health. Varieties of methods such as chemical precipitation, reverse osmosis, electrochemical treatment, ion exchange, membrane filtration, and adsorption have been used to remove heavy metals from wastewater [3]. Among them, adsorption is found to be one of the promising techniques with advantages such as high efficiency, environmental friendly, and low operational and maintenance costs. Nano adsorbents have exhibited obvious advantages due to their large specific surface area and great number of surface active sites. Especially, zero valent iron nanoparticles (nZVI) have attracted much attention to treat wastewater owing to its small size, amorphous structure and the presence of defective sites. The nZVI could act as promising regents that have been used to treat pollutants such as chlorinated organic solvents, nitrate, heavy metals and azo-dyes [4]. Furthermore, there are multiple interaction mechanisms between nZVI and compounds [5], such as surface mediated reduction, precipitation, surface complexation, partial chemical reduction, surface oxidation, and surface adsorption. Studies show that they are unique in environmental remediation [6]. However, due to the tiny particle size and high surface energy of the nano materials, nZVI are difficult to be separated from the wastewater, which limits their direct applications. A very straightforward and effective way is to prepare the well-structured novel beads in order to be applied as adsorbents. In addition, besides the unique properties of nanomaterials that mixed in the beads, other agents used during the synthesis procedure of the beads could also be verified not only used for forming the beads shape but also helpful on removal of the target pollutants to some extent. Previously, we have successfully prepared the polyvinyl alcohol (PVA) and pumice synthetized guar gum-nZVI beads (PPG-nZVI beads) and found their great removal efficiency towards lead [7]. The PPG-nZVI beads we have synthesized show superior properties such as large surface area, uniform size, high mechanical strength and good chemical stability. Their excellent removal efficiency towards lead also proved that they have the potential to be applied as adsorbents to remove heavy metal ions from wastewater. In this study, we further examined the removal efficiency of PPG-nZVI beads towards different kind of heavy metal ions as well as the influence of pH and ionic strength on their removal. As one of the typical commonly used technologies, stormwater infiltration facility is efficient to remove pollutants from urban runoff. The facility could be designed in several patterns such as planting pool, permeable pavement system, and bioretention system. The common fillers in the facilities are materials such as sand, zeolite, sawdust, and gravel. To improve the treating efficiency of the filler, we attempt to use the PPG-nZVI beads as one types of filling materials in stormwater infiltration facility to examine the removal efficiency towards heavy metals in runoff.