Abstract
Among the various possibilities of limiting the disposal of fly ashes (lignite), their reutilization as adsorbent materials is worthy of consideration. To this end, proper ashes beneficiation techniques can be put into practice. The adsorption of toxic compounds from industrial wastewater is an effective method for both treating these effluents and recycling lignite fly ash. The aim of this paper is to give a contribution for understanding the relationships among beneficiation treatments, adsorbent properties and adsorption mechanism and efficiency. In this context, the lignite fly ash was demineralised using concentrated HCl and HF (FA-DEM) and was used as adsorbent for Zn(II) ions from aqueous solutions. Batch experiments were carried out under various adsorbent dosages, pH, contact time and different metal ion concentrations. For FA-DEM, the 57.7% removal of Zn(II) ion was achieved under the optimum conditions of adsorbent dosages of 4 g/L, pH at 6, temperature at 303 K and the contact time of 1.15 h. The adsorption of Zn(II) ions onto FA-DEM followed the pseudo second order kinetics. The Langmuir isotherm model best represented the equilibrium data.
Highlights
Heavy metals are presented in wastewaters because of discharge by industry, for example electroplating, inorganic pigment manufacture, wood processing, photographic operations, and petroleum refining
In this paper we report the efficiency of Zn(II) uptake on lignite fly ash modified by treatment with HCl (4M HCl) followed by treatment with HF (FA-DEM)
Scanning Electron Microscopic Studies (SEM) The Figures 1(a) and (b) clearly show that the SEM was employed to observe the physical morphology of the FA-DEM before and after adsorption
Summary
Heavy metals are presented in wastewaters because of discharge by industry, for example electroplating, inorganic pigment manufacture, wood processing, photographic operations, and petroleum refining. The method most common and widely used for removing heavy metals from wastewater is chemical precipitation by the use of caustic soda or lime [5]. This method is not expensive, but requires a large amount of chemicals and results in a large quantity of sludge that requires supplementary treatment. Replacing synthetic substrates with low-cost adsorbents has, been intensively studied, and there have been reports of the use of materials obtained from agriculture and from forest wastes, for example, bagasse fly ash [6], sugar beet pulp [7], activated carbon derived from bagasse [8], maple sawdust [9], clay [10,11], volcanic ash bone char [12], humus [13], or bituminous coal, for removal of heavy metals. Removal of heavy metals (cadmium, copper, zinc, and nickel) on scrap rubber, bituminous coal, peat [14], natural zeolite [15], alkali treated lignite fly ash and alkali followed by methyl orange treated lignite fly ash [16] has been reported
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