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The objectives of this work were to prepare, characterize the CaCO3 nanoparticles as admixture derived from eggshell waste to improve the mechanical properties and performance of oil well cement (OWC) and to evaluate the interactions regarding the cement-admixture compatibility. The results suggest to use the combination of ultrafine grinding (ball milling) and heating treatment. The evaluation of the effectiveness of the addition of eggshell nanoparticles (ESNP) on the mechanical properties (compressive strength) of OWC was also an important objective. The high purity of eggshell powder was milled for 5–30 h to prepare ESNP with an average particle size of 40 nm after 25 h. The physico-chemical properties of the ESNP were characterized by different techniques including particle size analyzer (PSA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) methods. The ESPN was added in three different percentages to the OWC (2%, 6% and 10% as partial replacement of cement) and a w/c of 0.44. It was also revealed that the best percentage of ESNP addition not only resulted in much denser microstructure in OWC but also changed the formation of hydration products through presence of CaCO3 nanoparticles, which increased the rate of reaction of tricalcium aluminate (C3A) to form a carboaluminate complex. In this way the rate of hydration increased, the total hydration products increased and consequently the strength as well. Hence the addition of ESNP contributed to the improvement of early-age compressive strength, microstructure and durability properties of cement. According to the results, it was found that the optimal addition of ESNP to OWC is 6%.

The nanoparticles of the magnetic core-shell Fe3O4@SiO2 were produced using a modified Stöber approach and functionalized with (3-amino-propyl) APTES triethoxysilane and ethylene-diamine-tetra-acetic acid (EDTA). Magnetic nano adsorbents exhibit many attractive opportunities for different purposes due to their easy removal and possibility of reusing these nanoparticles. The ligands grafting was chemically stable and did not affect the morphology or substrate structure appreciably. APTES-EDTA microspheres were formed for the removal from aqueous solution solutions of trivalent rare earth elements ions since the REEs have a strong oxygen affinity. The advantages of the SiO2 shell that covers the magnetite nanoparticles include lower specific weight and a larger grafting density compared to other surfaces, improving the resistance to acidic environments. Different techniques have described the particle size, morphology, precise surface area and surface alteration including Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). The results show that the Fe3O4 nanoparticles with an average particle size of 15 ± 3 nm were successfully synthesized at pH=11, at 25 °C temperature. Moreover, The nanoparticles prepared for Fe3O4 were coated with amorphous SiO2 and functionalized with amino and carboxylic groups.

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