Removal of nickel and silver ions using eggshells with membrane, eggshell membrane, and eggshells

Abstract

Industrial wastewater containing heavy metals can become a serious environmental pollutant if not treated appropriately. Conventional treatment to remove toxic heavy metals can be expensive and may generate large amounts of toxic sludge. Regenerated natural wastes such as eggshells and eggshell membrane which are easily available, inexpensive, biodegradable, and have high adsorbability, can act as promising 'green' alternatives to remove heavy metal pollutants from wastewater. Here, we studied the adsorption capacity of eggshells with membrane (ESWM), eggshell membrane (ESM), and eggshells (ES) for the removal of nickel and silver ions in synthetic wastewater. Reaction time (1 to 72 h), metal ion concentration (25 to 200 mg/L), adsorbent dosage (0.1 to 0.8 g/20 mL), temperature (15? to 45?), and pH (1 to 9) were evaluated. Post-treatment nickel and silver concentrations were later analyzed using a spectrophotometer. Our results indicated increased removal of nickel and silver ions with increased adsorbent (all three ESWM, ESM, and ES) dosage, whereas the removal of nickel and silver ion decreased with increasing initial metal concentration. Among ESWM, ESM, and ES, ESM has the highest removal capacity and was the best adsorbent. The 0.8 g of ESM could remove 90.91% of nickel ions (100 mg/L) at 25?, pH 5.76 and 24 h. On the other hand, approximately 100% of silver ions (25 mg/L) could be removed by 0.2 g of ESM at 25?, pH 5.2, and 24 h. There was no difference in the adsorbability of ES and ESWM on nickel and silver ions. In summary, all three adsorbents, ESWM, ES, and ESM, can remove heavy metal ions from aqueous solution, with ESM having the highest efficiency. Hence, eggshell and its derivatives can be promising 'green' adsorbent materials for treating wastewater containing nickel and silver ions. Copyright © 2014, Japanese Society for Food Science and Technology.