## 1 Introduction  
Iron nanoparticles have recently gained great research interest in environmental applications since it offers high surface reactivity due to high the surface area [1]. Removal of organic pollutants [2; 3; 4], inorganic pollutants [5; 6], and pathogenic bacteria [7; 8; 9; 6] are among the most important applications. Moreover, iron nanoparticles have been applied for the catalytic degradation of chlorinated hydrocarbons such as trichloroethene, tetrachlorethene, and carbon tetrachloride from aqueous solutions [10; 11; 12].  
Many approaches have been reported for iron nanoparticles syntheses such as ball milling, sol-gel, high-energy electro-deposition [13], coprecipitation laser-induced gas phase pyrolysis, chemical vapor condensation, and freeze-drying [14]. Chemically, the formation of iron nanoparticles can be attained through the reduction of iron organic or inorganic salt or via reduction of an iron oxide.  
Iron nanoparticles have been synthesized by sodium borohydride or lithium triethylborohydride as a reducing agent [14].  
Green synthesis of iron nanoparticles has attracted much attention from researchers as it decreases nanoparticles aggregation and thus improves stability. In addition, it is an environmentally friendly method of eliminating the use of sodium borohydride as a reducing agent, which is very corrosive and flammable [10]. Furthermore, using plant extracts as reducing agent offer suitability for biomedical and pharmaceutical applications since no toxic chemicals are used during synthesis [8]. Green Iron nanoparticles synthesis using plant extract is a very effective synthesis process at a very reasonable cost. Recently, many reports have discussed the successful synthesis of iron nanoparticles via green chemistry [3; 4; 5; 8; 9; 11; 14; 15; 16; 17; 18].  
The work aims to explore the use of seedless pods of Acacia _nilotica_ extract (ANE), shown in Figure 1a as a reducing agent for iron nanoparticles synthesis using appropriate precursors such as FeSO\({}_{4}\).7H\({}_{2}\)O. Acacia _nilotica_ is a tropical and subtropical tree related to Leguminosae-Mimosoideae family. It can be found in Sri Lank, Pakistan, India, Egypt, Sudan, and tropical Africa [19]. Its bark, flowers, pods, and leaves have been traditionally used to cure many diseases such as cancer, cold, cough, diarrhea, fever, dysentery, hypertension, and bleeding piles [20]. Its young seedless pods contain 18-27% of tannins, flavonoids, and minerals. It was hypothesized that the young seedless pods of Acacia _nilotica_ may have reduction and stabilization effect during iron nanoparticles synthesis due to the presence of flavonoids and tannins [19; 20]. Acacia _nilotica_ leaves extract has been used for the synthesis of iron nanoparticles for Congo red dye degradation [21]. Furthermore, gold nanoparticles have been synthesized using leaves extract [22]. However, the seedless pods of the plant have not been reported for the synthesis of nanoparticles so far. Thus, the main goal of this study was to investigate the reduction and the stabilization effect of the seedless pods of Acacia _nilotica_ extract (ANE) in the synthesis of iron nanoparticles (FeNP) and to investigate the FeNP in adsorption, degradation, and antibacterial applications.