Abstract
In the present work, waste eggshells were used as a precursor for the synthesis of aragonite crystals through the wet carbonation method. Cadmium (Cd2+) and lead (Pb2+) were removed by the synthesized aragonite from synthetic wastewater. The influence of initial solution pH, contact time, Cd2+ and Pb2+ concentration, and sorbent dosage were evaluated. The major sorption was observed in the first 100 mins and 360 mins for Pb2+and Cd2+ respectively reaching sorption equilibrium at 720 mins (12 hr). The sorption capacity toward Pb2+ was much higher than toward Cd2+. Both heavy metals displayed high sorption capacities at initial pH 6. The pseudo-second-order kinetic model fits well with the experimental data with a higher correlation coefficient R2. Two isotherm models were also evaluated for the best fit with the experimental data obtained. Langmuir isotherm best fits the sorption of the metals on aragonite synthesized from eggshells. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) results of sorbent after sorption showed that the mechanism of sorption was dominated by surface precipitation. Therefore, aragonite crystals synthesized from waste eggshells can be a potential substitute source for the removal of Cd2+ and Pb2+ from contaminated water.
Highlights
Solid waste management, being a current vital issue, is a huge burden regarding sustainability
The objective of the present work is to study the potential use of synthesized aragonite crystals from eggshells in the sorption of Cd2+ and Pb2+ from synthetic wastewater
All the peaks of synthesized sorbent resembled aragonite phase, which implies that the transformation of calcite to a high grade aragonite crystals can be obtained from waste eggshell through wet carbonation
Summary
Solid waste management, being a current vital issue, is a huge burden regarding sustainability. The rapid rise in population resulted in an increase in food waste such as eggshell, which is one of the solid wastes available in abundance with serious environmental problems. Approximately 5.92 million tonnes of waste eggshell are generated per year [1]. These waste eggshells have been dumped into landfills without further treatment, causing several environmental consequences [2]. The waste is mainly made up of calcium carbonate (CaCO3) with minor impurities, which has been used in further applications as a source of calcium supplements [3,4,5]. The effect of impurities has been minimized with further treatments such as chemical treatment and physical treatment [6,7]
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