Abstract
Lead, a highly toxic element, is frequently present in various solid wastes as well as in industrial effluents. Sorption with a low cost sorbent is a simple way of Pb removal from liquid streams, but stabilization of spent sorbent has to be ensured in order to prevent Pb leaching out and possible environmental contamination. In previous research, ceramic sorbent, generated as waste product in brick industry, was tested as sorbent and proved high sorption capacity for lead. Lead was sorbed partially as hydrocerussite and partially as adsorbed surface layer. The Pb leaching from sorbent was very high and thus further immobilization of sorbent was necessary. Lead, as well as other heavy metals, is known as retarder of the hydration process of Ordinary Portland Cement (OPC), used for the immobilization. In this paper, influence of sorbed Pb and PbO, as reference compound, on cement hydration was studied by calorimetry, thermogravimetry and Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy (MAS NMR). The sorbed lead was found to be less detrimental to hydration retardation due to the lower solubility of precipitated hydrocerussite in basic environment compared to PbO, which forms plumbate anion.
Highlights
Lead belongs, due to its high toxicity, to elements which environmental emissions and occurrence are carefully monitored
Lead was added in two forms; either as sorbed on ceramic sorbent—samples CEM + Pb from the sorbent (PbSorb)-x, where x stands for mass fraction of Pb per Ordinary Portland Cement (OPC) (x = 0.5 and 2), or as PbO (CEM + Pb-x)
The mass change around 650 ◦C is missing in PbSorb due to conversion calcium carbonate to hydrocerussite during the sorption experiment
Summary
Due to its high toxicity, to elements which environmental emissions and occurrence are carefully monitored. Lead exposure is responsible for effects on nervous system, the reproductive system and kidneys. Lead gets collected in tissues; especially children are vulnerable to lead exposure, since lead is more absorbed into growing bodies. Sources of Pb environmental contamination were reviewed in [4]; lead is present in industrial waste waters, e.g., from acid–lead battery production and processing [5] (22 mg/L) or metallurgy [6]. Due to relatively high volatility of Pb compounds, lead is entering ecosystems through atmospheric precipitation [7]. The industrial effluent limit for Pb in EU countries is 500 μg/L [10]
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