Conversion of waste eggshells to mesoporous hydroxyapatite nanoparticles with high surface area

Synthesis of rod-like hydroxyapatite with high surface area and pore volume from eggshells for effective adsorption of aqueous Pb(II)

“…Again, the equilibrium adsorptions for the different concentrations were in 10 min irrespective of the concentration or the sorbent used. Note here that the adsorption for the 398 and 934 mg/l initial concentrations were obtained using the HAP sample from the previous work [18]; pH had no significant effect on the system [36] therefore, a fixed pH 9 was used subsequently.…”

“…The calcination also reduces their particle, surface and pore parameters which are vital for adsorption purposes. Having produced RHNP with large surface and pore parameters from burnt eggshells at room temperature in this study and from raw eggshells at room temperature via using nitric acid in the previous work [18], we applied these products as adsorbents or biosorbents for the adsorption of Pb 2+ from wastewater without the usual calcining at higher temperatures. Our target was inexpensive, efficient, and effective adsorbents/ biosorbents for heavy metal recovery from wastewater and waste treatment.…”

“…Atomic absorption spectrophotometer (AAS, PerkinElmer 700) was used to analyze the dissolved Pb 2+ from standard solution of lead acetate using a calibration curve. With the above procedure, the adsorption of different HAp materials (calcined, uncalcined, previously prepared [18]) was investigated, and the adsorption isotherms at 25 C for the uncalcined RHNP prepared in this work were measured.…”

“…The crystallite phases of the eggshell powder, the powder calcined at 950 C, commercial HAp, produced RHNP, and the RHNP calcined at various temperatures were characterized by XRD as before [18]. Briefly, data were collected in 2u using a step size of 0.02 in 40 s counting range between 10 and 70 in a reflection mode with Cu K a radiation.…”

“…Another aim was to apply the as-produced product as an effective adsorbent (without calcining to !600 C) for the adsorption of Pb 2+ from wastewater. We also applied another mesoporous HAp produced previously [18] for this adsorption purpose. The difference between the mesoporous HAp from the previous study and the RHNP in the current study is that the latter was generated from burnt eggshell powder (to yield CaO and Ca (OH) 2 subsequently), the former HAp was obtained by dissolving eggshells in concentrated nitric acid (to get Ca(NO 3 ) 2 ).…”