Metal Immobilization in Soils Using Synthetic Zeolites

Abstract

In situ immobilization of heavy metals in contaminated soils is a technique to improve soil quality. Synthetic zeolites are potentially useful additives to bind heavy metals. This study selected the most effective zeolite in cadmium and zinc binding out of six synthetic zeolites (mordenite-type, faujasite-type, zeolite X, zeolite P, and two zeolites A) and one natural zeolite (clinoptilolite). Zeolite A appeared to have the highest binding capacity between pH 5 and 6.5 and was stable above pH 5.5. The second objective of this study was to investigate the effects of zeolite addition on the dissolved organic matter (DOM) concentration. Since zeolites increase soil pH and bind Ca, their application might lead to dispersion of organic matter. In a batch experiment, the DOM concentration increased by a factor of 5 when the pH increased from 6 to 8 as a result of zeolite A addition. A strong increase in DOM was also found in the leachate of soil columns, particularly in the beginning of the experiment. This resulted in higher metal leaching caused by metal-DOM complexes. In contrast, the free ionic concentration of Cd and Zn strongly decreased after the addition of zeolites, which might explain the reduction in metal uptake observed in plant growth experiments. Pretreatment of zeolites with acid (to prevent a pH increase) or Ca (to coagulate organic matter) suppressed the dispersion of organic matter, but also decreased the metal binding capacity of the zeolites due to competition of protons or Ca.

Edta, Water-Extractable Arsenic and Bioavailability of Arsenic in Soil/Tailings: the Effects of Zeolite and Beringite Amendments

“…The capping of contaminated tailings with lateritic soil as practiced by some mining companies in Ghana does not remove arsenic from the soil/tailings. Amendments that have been screened for their potential to immobilize heavy metals in soils are alkaline materials such as beringite and zeolite (Edwards, Rebedea, Lepp, & Lovell, 1999.;Oste, Lexmond, & Van Riemsdijk, 2002;Mench, Vansgronsveld, Beckx, & Ruttens, 2006).…”

Assessment of Heavy Metals Inactivation in Contaminated Soil by Coal Fly and Bottom Ashes

“…Several remediation methods have been applied under in-situ (Matsi, Keramidas 1999;McGowen 2000;Oste et al 2002) as well as ex-situ (Tandy et al 2004;Diatta, Chudzinska 2009) conditions to soils anthropogenically contaminated with various contaminants. Additives, among others zeolites (Querol et al 2005) and clay minerals (Lombi et al 2003), were also applied to soils for this purpose.…”

A Comparative Study of the Sorption of Cd(II) and Pb(II) Ions from Aqueous Solution by Local Bentonite and Clinoptilolite

“…These give rise to uncompensated charges capable of being balanced by adsorbed cations. Substitution of trivalent aluminium ions for quadrivalent silicon within the lattice structure of the tetrahedral sheets and of ions of lower valency, particularly magnesium, for trivalent aluminium in the octahedral sheets results in uncompensated charges in the structural units of clay minerals (Ozturk et al 2007;Breck 1974). The above factors largely explain the good sorption properties of zeolites and bentonite towards heavy metal ions from aqueous solutions (Bhattacharyya and Gupta 2007; Rao et al 2006;Shahwan et al 2006;Faghihian and Bowman 2005;Erdem et al 2004;Alvarez et al 2003;Faghihian et al 2003;Chakir et al 2002;Inglezakis et al 2002;Oste et al 2002;Naseem and Tahir 2001;Nava et al 1995).…”