Treatment of metals-contaminated wastewaters by use of natural zeolites

Abstract

This paper assesses the potential of natural zeolite utilization as a low-cost in exchange material for heavy metals removal. Two natural zeolites, clinoptilolite and chabazite, have been evaluated with respect to their selectivity and removal performance for the treatment of effluents contaminated with mixed heavy metals (Pb, Cd, Cu, Zn, Cr, Ni and Co). The effects of relevant parameters such as chemical treatment, metals concentration, pH, and presence of competing ions were examined. The results showed that the received zeolites contained exchangeable K, Ca and Na ions, but exposing them to concentrated NaCl solutions converted them to a homoionic state in the Na form which improved their exchange capacity. Clinoptilolite and chabazite exhibited different selectivity profiles for all metals studied except for Pb for which both zeolites performed exceptionally well. The results also showed that chabazite exchange capacity is superior to that of clinoptilolite mainly due to the higher Al substitution of Si which provides chabazite with a negative framework favourable to higher exchange capability. The pH was found to have an effect on metal removal as it can influence both the character of the exchanging ions and the zeolite itself. Overall, the removal mechanism was controlled by ion exchange and precipitation was proven negligible.

Iron(II) modified natural zeolites for hexavalent chromium removal from contaminated water

“…Clinoptilolite is one of the most abundant zeolite minerals and has been widely used for heavy metals removal from waters and wastewaters (Faghihian and Bowman 2005, Park et al 2002, Wingenfelder et al 2005. Chabazite and phillipsite are also of commercial interest due to their favourable exchange properties (Ouki andKavannagh 1999, Sheta et al 2003).…”

Multi-Technique Application for Waste Material Detection and Soil Remediation Strategies: The Red Mud Dust and Fly Ash Case Studies

“…Synthetic zeolite can be added to polluted soils (Querol et al, 2006;Lin et al, 1998;Rayalu et al, 2006) or crystallized directly in those contaminated (Belviso et al 2010b;2010c;Terzano et al, 2006) in order to solve environmental problems. Zeolites are hydrated aluminosilicate minerals with a three-dimensional open structure making them very useful for solving the mobility of toxic elements in a number of environmental applications (Babel and Kurniawan, 2003;Ćurković et al, 1997;de'Gennaro et al, 2003;Inglezakis et al, 2002Inglezakis et al, , 2003Kesraoui-Ouki et al, 1994;Kocaoba et al, 2007;Moreno et al, 2001aMoreno et al, , 2001bOuki and Kavannagh, 1999;Pansini & Colella, 1990;Querol et al, 1999Querol et al, , 2002Rayalu et al, 2006;Stefanović et al, 2007;Torracca et al, 1998;Woolard et al, 2000;Wu et al, 2008). All this is strictly connected with their ability to exchange cations, their large surface area, and their typical structural characteristics (such as porosity), which facilitate pollutant absorption and encapsulation.…”

Utilização de zeólita preparada a partir de cinza residuária de carvão como adsorvedor de metais em água

“…O pH tem um impacto significante na remoção dos metais por zeólita, já que pode influenciar o caráter dos íons trocáveis e o caráter da pró-pria zeólita 13 .…”