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Calcium oxide was obtained from eggshell and modified with Sulfur, Nitrogen and, Oxygen. The adsorbents were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and, scanning electron microscopy (SEM). The adsorbents were used for the removing of the dyes of Nigrosin, Alizarin red S, Indigo carmine, and Acid fuchsin from their aqueous solutions. The adsorption isotherm experiments were studied, and the equilibrium adsorption found either obeyed the Langmuir or Freundlich isotherm depending on the Sips isotherm results. Thermodynamic studies showed that the adsorption processes of the studied dyes were spontaneous, endothermic and randomness increases according to their ΔG, ΔH and ΔS values, respectively. The kinetic studies revealed that the pseudo second-order model best represented adsorption kinetics. Moreover, the photocatalytic ability of adsorbents was investigated under the sunlight, the results revealed the adsorbents have a strong photo-catalytic ability to absorb the dyes, particularly that observed for Acid fuchsin.

Successful removal of nigrosine, alizarin, indigo and acid fuchsin dyes from aqueous solutions using modified CaO nanoparticles has been investigated. The CaO was obtained from eggshells and modified with AgI. The adsorbents were characterized using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy and transmission electron microscopy. The kinetic studies were also investigated, the results showed that the adsorption of alizarin dye follows the pseudo-first-order model, while the adsorption of the nigrosine, indigo, and acid fuchsin follow the pseudo-second-order model onto modified and unmodified CaO. Moreover, the photocatalytic activity of modified adsorbent was tested under sunlight. The modified adsorbent showed a strong photocatalytic activity, a 0.01 g modified adsorbent was sufficient to absorb 100% of acid fuchsin through only 5 min after exposes to sunlight.

In this paper, calcium oxide (CaO) was produced by the thermal treatment of eggshell. The doping process with silver iodide (AgI), oxygen (O), sulfur(S) and nitrogen (N) was achieved by adsorbents. The adsorption of Acid fuchsine (AF), Indigo Carmine (IC), Nigrosine (NG) and Alizarine Red S (AR) on the surface of these particles was studied. The different conditions affecting the adsorption process, such as the time of equilibrium, the primary concentration of the studied dyes, the amount of the adsorbent, the acidic function, the speed of the pruning motion and the temperature were studied. The pH stability time (5-10 minutes), IC and NG (30 minutes) and AR were (90 minutes). The effect of temperature was also studied within the range (25-45 ° C). The results showed that the adsorption capacity increased by increasing the temperature, ie the reaction is endothermic. The study showed the effect of the acidic function on the percentage of pigmentation. The percentage was increased by increasing the acidic function in the basal circles on the surfaces except for the AR dye. It decreased the percentage by increasing the acidic function. The effect of the weight of the adsorbent was studied on the percentage of adsorption.