The use of waste materials as low-cost adsorbents is attractive due to their contribution in the reduction of costs for waste disposal, therefore contributing to environmental protection and most importantly, offers an attractive potential alternative to their conventional methods of removal of toxic ions from wastewater. Eggshells are naturally occurring and an abundant biomass that has proven to offer an economic solution for toxic ions removal. The eggshell biomass was treated with acetic acid (vinegar). Nickel (II) and Cobalt (II) ions were selected as model ions to demonstrate the potential of eggshell waste in removing excess toxic heavy metal ions from wastewater. All the experiments were carried out in batch process with laboratory prepared samples. Multivariate optimization method was used to identify factors affecting adsorption. These factors included metal ion concentration, pH, contact time and biomass dosage on removal of nickel and cobalt from wastewater effluent was investigated. Two-level fraction factorial and central composite design were used for optimization methods. Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, and Scanning Electron Microscopy coupled with Energy-dispersive X-ray spectroscopy were used to study physical properties of the waste material. The percentage removal of Nickel (II) and Cobalt (II) was 78.70 ± 1.02 and 76.53 ± 1.21 respectively. Vinegar-treated eggshells were proposed as eco-friendly, cheap, easily available and an efficient method for removal of heavy metals from the environment.
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