Australian Clinoptilolite Tuff for Removal of Metal Ions from Wastewater, pp. 393-415
Authors: (Syaifullah Muhammad, Shaobin Wang, Moses O. Tadé - Department of Chemical Engineering, Curtin University of Technology, Perth, Australia)
Abstract: Natural zeolites are naturally occurring hydrated aluminosilicate minerals. The structures of zeolites consist of three-dimensional frameworks of SiO4 and AlO4 tetrahedra. The aluminum ion is small enough to occupy the position in the center of the tetrahedron of four oxygen atoms, and the isomorphous replacement of Si4+ by Al3+ produces a negative charge in the lattice. The net negative charge is balanced by the exchangeable cation (sodium, potassium, or calcium). These cations are exchangeable with certain cations in solutions such as lead, cadmium, zinc, and manganese. Clinoptilolite (HEU topology) is the most abundant natural zeolite and is mainly found in specific types of sedimentary rocks (tuffs). Tuffs containing crystals of HEU-type zeolites provide low-cost industrial minerals with several commercial applications, with the emphasis on the removal of pollutant metal ions from wastewaters. Removal of heavy metals from aqueous wastes is a challenging task for the correct management of waste disposal. In the past two decades, research has been carried out focusing on using lowcost effective sorbents for heavy metal adsorption and the sorption behaviour of several natural materials and waste products has been investigated. In this paper, we report an investigation of using natural clinoptilolite tuff from Australia for heavy metal removal (Cr3+ and Pb2+) from wastewater. We studied the properties of the clinoptilolite tuff and several parameters influencing the removal efficiency of single metal ions and binary mental ions. In single metal ion system, kinetic studies show that the adsorption is physical process and follows the first-order kinetics. Adsorption isotherm can be well fitted by the Langmuir and Freundlich models. In binary metal ion system, the adsorption of Cr3+ and Pb2+ shows competitive adsorption and adsorption capacity is greatly reduced. Temperature also influences the adsorption capacity.