Modification of Silica Nanoparticles with 4,6-Diacetylresorcinol as a Novel Composite for the Efficient Removal of Pb(II), Cu(II), Co(II), and Ni(II) Ions from Aqueous Media

Due to the danger of heavy metals such as Pb(II), Cu(II), Co(II), and Ni(II) ions to the environment and humans, the world needs to develop new effective adsorbents to get rid of them. Many Schiff bases can form chelates with most heavy metal ions. Hence, loading them on supports like silicon oxide as new composites help to solve the pollution problem. So, in this work, a new composite based on the formation of Schiff base on silica nanoparticles was facilely synthesized. (3-aminopropyl)trimethoxysilane was used to modify silica nanoparticles with silanol groups (Si–OH). Then, the modified silica was then combined with 4,6-diacetylresorcinol to create a new Schiff base/silica composite. XRD, FE-SEM, FT-IR, CHN analyzer, and N 2 adsorption/desorption analyzer were used to characterize the synthesized composite. The formation of the Schiff base results in a significant drop in the intensity of the composite XRD peak at 2Ɵ = 21.9°. In addition, the FT-IR bands at 3443 and 1606 cm −1 are due to the stretching and bending vibrations of OH and/or C=N, respectively. The FE-SEM images confirmed that the silica has uneven forms while the composite has a flaky surface due to the formation of the Schiff base. According to an elemental analysis of the composite, the percentages of C, H, and N are 15.26, 3.24, and 1.65%, respectively. The produced Schiff base restricts the pores of silica and hence the composite BET surface area and total pore volume were lowered. The synthesized composite was used to remove Pb(II), Cu(II), Co(II), and Ni(II) ions from aqueous solutions with high efficiency. The maximum uptake capacity of the composite toward Pb(II), Cu(II), Co(II), or Ni(II) ions is 107.066, 89.767, 80.580, and 70.972 mg/g, respectively. The adsorption processes of the investigated metal ions were chemical, spontaneous, and well fitted with the Langmuir equilibrium isotherm and pseudo-second-order kinetic model. The synthesized composite can be successfully regenerated and utilized various times in the removal of investigated metal ions from aqueous solutions.