USE OF NANOTECHNOLOGY IN REMEDIATION OF HEAVY METALS POLLUTED SOILS

Abstract

Heavy metals polluted soils are a significant worldwide environmental problem. The crops cultivated in polluted soils often contain significant levels of heavy metals (Cd, Pb,.. etc) that can impair human health. The current technologies such as; removing up of pollutants; stabilization/solidification of pollutants, vitrification, soil capping.., etc; used in remediation of polluted soils are not adequate. Smarter and cheaper techniques still need to be addressed to decontaminate polluted soil. Nanotechnology offers a number of emerging techniques much more effective that could work to immobilize contaminants. In the present study, nanoparticles; nano scale zero valent iron “nZVI”, nZVI- bentonite, nano alginite, nano carbon and dendrimers; are used as a potential sorbents to immobile Cd and Pb in polluted soil. These nanoparticles (except nano carbon) are prepared in lab either using top-down or bottom-up methods, then characterized using transmission electron microscop (TEM). The prepared nanoparticles proved to have very small size (less than 100 nm), high surface area (151-259.7 m 2 /g) and cation exchange capacity (30.3-60.7Cmol(c)/kg). Also, the prepared nanoparticles proved high adsorption capacity for Cd and Pb, and high retention for the adsorbed metal. The maximum adsorption capacity of nanoparticles ranged from 1598-93458 and 3954-25974 mg kg-1 for Cd and Pb, respectively. That is besides, only small percents (5.7-13% and 21.6-61.8%) of the previously adsorbed ones were desorbed. Application of nanomaterials to polluted soils at rates of 0.1 to 1% efficiently reduced plant available Cd and Pb as extracted using DTPA. Also, they efficiently transformed Cd and Pb in polluted soils from mobile (exchangeable) to immobile form (oxides form). Also, application of nanomaterials to polluted soils at rates of 1% and 2% in pots experiment significantly increased fresh and dry weight of crop Garden Rocket (Eruca Sativa) and decreased uptake of Cd and Pb.