Utilization of iron scrap into copperas and rambutan (Nephelium lappaceum L.) peel extract into environmentally friendly iron nanoparticles for hexavalent chromium removal and its kinetics

Abstract

AbstractHexavalent chromium is a toxic pollutant that is very harmful to human health and the environment. One of the materials for hexavalent chromium removal is iron nanoparticles (INPs). In recent years, the manufacture of environmentally friendly INPs has been of great interest. In general, INPs are made using sodium tetra borane/NaBH4, which is expensive. The synthesis of INPs using NaBH4 also produces side products in the form of toxic boric acid and hydrogen gas which are explosive and flammable. In this study, INPs are made by using iron scrap waste into copperas which is then reacted with rambutan peel extract (RPE). The reaction between iron scrap and sulfuric acid until crystals are formed and then washed until blue‐green crystals are formed. The resulting crystal is made into a solution and then reacted with RPE. After forming a black solution, it was dried by spray drying. The resulting black powder was characterized by UV‐Vis Spectrophotometer, SEM‐EDX, FTIR, and XRD. The results showed that iron scrap can be synthesized into copperas with a Fe content of 19.84 ± 0.15%. RPE has a total phenol content of 877.39 ± 16.6 ppm/100 g rambutan skin or equivalent to 441.42 mg GAE/100 g rambutan skin. INPs can be made from copperas from iron scrap and RPE which have Surface Plasmon Resonance (SPR) characteristics at 214 nm absorption, particle size 20–70 nm. Hexavalent chromium removal using INPs was maximum at pH 3, hexavalent chromium concentration of 5 ppm, INPs concentration of 0.15 g/100 mL, and contact time of 10 min. The adsorption isotherm type of hexavalent chromium using iron nanoparticles can take place chemically or physically. The correlation coefficient showed that the model of Freundlich (R2 > 0.99) is more suitable than the model of Langmuir (R2 = 0.98) with an adsorption capacity of 91.74 mg iron nanoparticles/g hexavalent chromium. The use of INPs for hexavalent chromium removal is a promising and effective technology. These results can be an alternative to the production of environmentally friendly INPs by using materials from waste into useful materials for the prevention of environmental pollution.