As part of its commitment to advancing scientific research and innovation in applied chemistry and nanotechnology, the Department of Chemistry at the College of Education for Pure Sciences / Ibn Al-Haytham, University of Baghdad, held the defense of a PhD dissertation entitled “Synthesis of Novel Magnetic Nanocomposites and Their Application in the Removal of Terasil Black Dye, Lead, and Biological Contaminants from Industrial Wastewater,” submitted by Ali Fadhil Ismail Fayyadh under the supervision of Professor Dr. Intisar Alawi Laibi.
The research aimed to synthesize innovative magnetic nanocomposites with high efficiency in removing Terasil Black dye, lead ions, and biological contaminants from industrial wastewater. The study seeks to develop advanced and sustainable water treatment technologies capable of improving water quality, enabling the reuse of industrial water, and mitigating the environmental and public health risks associated with industrial pollutants.
The dissertation was examined by an academic committee chaired by Professor Dr. Ahlam Mohammed Farhan, with the membership of Professor Dr. Juman Ahmed Nasser, Assistant Professor Dr. Enas Hussein Ali, Assistant Professor Dr. Taghreed Baqir Alwan, Assistant Professor Dr. Khalida Obaid Samawi, and Professor Dr. Intisar Alawi Laibi, who also served as the dissertation supervisor.
This research reflects the College’s commitment to directing postgraduate research toward addressing critical environmental challenges and developing innovative nanotechnology-based solutions for industrial pollution control, thereby strengthening the University’s contribution to environmental sustainability, scientific innovation, and community service.
The dissertation contributes directly to United Nations Sustainable Development Goal (SDG) 6 – Clean Water and Sanitation by developing advanced technologies for industrial wastewater purification and improving water quality. It also supports SDG 9 – Industry, Innovation and Infrastructure through the application of nanotechnology in environmental remediation, SDG 3 – Good Health and Well-being by reducing exposure to hazardous pollutants, SDG 12 – Responsible Consumption and Production by promoting sustainable resource management and reducing industrial environmental impacts, and SDG 4 – Quality Education through strengthening scientific research and preparing highly qualified researchers capable of addressing contemporary environmental challenges.
This dissertation presents the synthesis, characterization, and application of reduced graphene oxide/magnetite binary nanocomposite (rGO/Fe3O4)-based ternary nanocomposites combined with SnO2, ZrO2, and MnO2 nanoparticles, denoted as r/F/S, r/F/Z, and r/F/M, respectively. The synthesis involved several stages, beginning with the preparation of graphene oxide (GO) sheets via a modified Hummers’ method, followed by reduction to reduced graphene oxide (rGO).
Binary nanocomposites rGO/Fe3O4 (r/F) were formed by co-precipitation of Fe (II) and Fe (III) ions in the presence of rGO. Subsequently, metal dioxide nanoparticles (MOX NPs) of SnO2, ZrO2, and MnO2 were prepared via precipitation and calcination from metal salts solutions. These MOX NPs were magnetically mixed with r/F to produce ternary nanocomposites r/F/S, r/F/Z, and r/F/M.
A comprehensive characterization was performed using Fourier transform infrared spectroscopy (FT-IR), showing peak shifts indicating strong interactions between r/F and MOX. Field emission scanning electron microscope analysis (FESEM) revealed monolayer rGO structures with well-dispersed Fe3O4 and MOX nanoparticles. X-ray diffraction analysis (XRD) confirmed well-crystallized phases with mean crystalline sizes calculated via the Debye-Scherrer equation as 11.18 nm (r/F), 24.4 nm (r/F/S), 15.98 nm (r/F/Z), and 19.75 nm (r/F/M). Energy dispersive x-ray spectroscopy analysis (EDS) verified elemental composition, affirming a carbon matrix with Fe, Sn, Zr, and Mn incorporation. Magnetic properties analyzed by vibrating sample magnetometer analysis (VSM) showed ferrimagnetism of Fe3O4 diminished in ternary nanocomposites due to non-magnetic rGO and MOX presence.
Optical analyses included photoluminescence spectra, where r/F/S and r/F/M exhibited strong emissions, while r/F/Z showed weak emission. Absorbance, transmittance, and reflectance spectra were measured from )200–1100 (nm, and optical band gaps for allowed direct transitions were determined as 3.15 eV (r/F/S), 2.43 eV (r/F/Z), and 2.61 eV (r/F/M), compared to MOX optical band gaps (SnO2 = 3.6 eV, ZrO2 = 5.0 eV, MnO2 = 3.0 eV). Extinction coefficient, refractive index, and real and imaginary dielectric constants varied with nanocomposite structure and photon energy for ternary nanocomposites.
Thermogravimetric analysis (TGA) and differential scanning calorimetry – differential thermal analysis (DSC-DTA) assessed thermal stability; TGA indicated weight loss stages, with good stability above 50 ºC. Surface area, pore volume, and pore diameter were quantified using nitrogen adsorption data analyzed with BET, Langmuir, t-plot, and BJH models.
Adsorption studies targeted the removal of terasil black (TB) dye from the wastewater samples of Al-Kut textile factory. Initial dye concentration (10 ppm) decreased to 1.67 ppm (r/F/S), 2.08 ppm (r/F/Z), and 3.75 ppm (r/F/M) after adsorption. Equilibrium times were 60 min for r/F/S and r/F/M, 40 min for r/F/Z. Adsorption capacities were 78.75 mg/g (r/F/S), 56.25 mg/g (r/F/Z), and 50.42 mg/g (r/F/M) at 298 K. Kinetics followed pseudo-second order kinetic model with high correlation coefficients (R² > 0.99). Activation energy was the lowest value for r/F/S (0.68 kJ/mol), indicating easier adsorption. Type S isotherms in Giles classification and the Freundlich model fit indicated heterogeneous multilayer adsorption. Thermodynamics showed an endothermic process with positive values of enthalpy and entropy changes, and spontaneous adsorption was evidenced by negative Gibbs free energy increasing with increasing in temperature. Optimal pH was slightly acidic to neutral. Increased solution ionic strength decreased the adsorption capacity.
Similarly, the adsorption of Pb²⁺ ions was investigated using wastewater samples from Al-Waziriyah General Company for electrical and electronic industries, with initial concentrations of 0.27 ppm reduced to 0.052 ppm (r/F/S), 0.083 ppm (r/F/Z), and 0.108 ppm (r/F/M). Equilibrium time was the lowest for r/F/S (30 min). Adsorption capacities were 33.96 mg/g (r/F/S), 25.21 mg/g (r/F/Z), and 24.37 mg/g (r/F/M). Pseudo-second order kinetic model and the Freundlich isotherm model were applied. Activation energies were (r/F/S=9.26, r/F/Z=23.98, and r/F/M=26.54) kJ/mol. Thermodynamics suggested endothermic process with positive enthalpy and entropy changes, non-spontaneous adsorption for Pb²⁺ ions with positive value of Gibbs free energy diminishing with rising temperature. pH and ionic strength effects were similar to dye adsorption.
Photodegradation process was evaluated to remove (TB) dye from the wastewater samples of Al-Kut textile factory using the prepared and activated ternary nanocomposites after being placed in the dark for (60 min.) to obtain equilibrium (adsorption/desorption) state, then it was exposed to UV irradiation directly using a manual irradiation system exposure cabinet with (15) watt power UV lamp having wavelength range (200 nm-400 nm) and at a distance of (10 cm) from the UV lamp. The results of (TB) dye concentrations in the solution samples after using the photodegradation process under optimum conditions with an initial concentration of the solution before treating with (10 ppm) were (r/F/S=0.025 ppm, r/F/Z=0.416 ppm, and r/F/M=1.167 ppm). Optimal catalyst loading weight was 0.15 g, enhancing active surface area and free radical generation. Increasing dye concentration reduced degradation due to light absorption shielding. Higher temperatures accelerated photodegradation kinetics. Optimal pH was slightly acidic to neutral. Pseudo-first order kinetic model described the reactions, with the rate constant highest for r/F/S. Activation energies were (r/F/S=22.59, r/F/Z=25.27, and r/F/M= 28.77) kJ/mol, implying efficient and physical adsorption-driven photocatalysis. Thermodynamic parameters confirmed endothermic, spontaneous photocatalytic reactions, with positive change entropy indicating increased randomness and negative Gibbs free energy values. Comparative analysis showed photodegradation surpassed adsorption for dye removal efficiency, with activity order: r/F/S > r/F/Z > r/F/M.
Finally, studying the bioactivity of the nanocomposites against pathogenic microorganisms (gram-positive, gram-negative, and pathogenic fungi) isolated from tannery wastewater from Malik leather tannery in Al-Nahrawan city showed that the r/F/M nanocomposite was more effective against all tested microorganisms compared with the other nanocomposites under study, but with various degrees of sensitivity.
