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Tee, Wan Ting (2025) Development of 3D heteroatom-doped graphene oxide composites for removing tricyclic antidepressant pharmaceutical residues from wastewater. PhD thesis, University of Nottingham.

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Abstract

Tricyclic antidepressant (TCA) residues in water sources are an emerging environmental concern due to increasing usage and potential risks to ecosystems and human health. Their persistence and biological activity have led to recent frequent detection in aquatic environments. However, conventional wastewater treatment processes are not designed to effectively remove such emerging contaminants. Heteroatom doping of graphene has shown potential in enhancing adsorption performance for various water pollutants, but its application for TCA removal remains underexplored. This thesis addresses this research gap by developing novel three-dimensional (3D) heteroatom-doped graphene oxide (GO) composites for efficient TCAs adsorption from aqueous solutions.

Several types of 3D heteroatom-doped GO composites were developed via solution-based synthesis route for the removal of different TCAs from aqueous solutions. These include 3D boron-doped GO (3DBG) reinforced with carboxymethyl cellulose (CC), 3D phosphorus-doped GO (3DPG) with bentonite and CC, sulphur-doped GO (3DSG) with bentonite and CC, and nitrogen-sulphur co-doped GO (3DBG) with bentonite and CC. Each adsorbent was custom-made to enhance the adsorption efficiency of specific TCA pharmaceutical such as amitriptyline, imipramine, nortriptyline and clomipramine.

The studies involved characterising the physico-chemical properties of the graphene composites using various high-precision techniques including XRD, TGA, FTIR, TEM, XPS and FESEM-EDX. Batch adsorption experiments were carried out to determine the effects of different parameters such as dosage, initial TCA concentration, system temperature and contact time, on the adsorption performance. The interactive effects of multiple factors and system optimisation were evaluated by response surface methodology with central composite design. The adsorption kinetic and equilibrium data were analysed using theoretical adsorption models like pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich, intraparticle diffusion, Langmuir, Freundlich and Dubinin-Radushkevich models.

The results showed relatively high Langmuir maximum adsorption capacities for all four heteroatom-doped GO composites, with values of 737.4, 433.3, 472.9 and 531.9 mg/g for amitriptyline-3DBG, imipramine-3DPG, nortriptyline-3DSG and clomipramine-3DNSG systems, respectively. The adsorption processes were found to be spontaneous and endothermic, with mechanisms involving chemisorption, physisorption, π-π interactions, pore filling, hydrogen bonding, hydrophobic and electrostatic interactions. The graphene composites exhibited impressive removal efficiencies, with the ability to be regenerated through different chemical elution such as ethanol, methanol, hydrochloric acid and acetone.

Response surface methodology (RSM) with central composite design (CCD) was used to assess the interactive effects of key parameters and optimise the adsorption processes. The optimised conditions which offered the highest removal efficiencies of amitriptyline (87.72 %) by 3DBG were 12.5 mg, 32 min, 30 °C and 70 ppm, and of nortriptyline (80.74 %) by 3DSG were 12.5 mg, 35 min, 30 °C and 100 ppm. The highest adsorption capacities of imipramine (458.95 mg/g) onto 3DPG was achieved at 10 mg, 34 min, 48 °C and 250 ppm, and of clomipramine (332.5 mg/g) onto 3DNSG was attained at 15 mg, 44 min, 30 °C and 300 ppm.

A further study has evaluated the potential large-scale application of 3DBG composite in removing amitriptyline using a continuous packed-bed setup. The best conditions were found to be a graphene bed height of 3.5 cm, an amitriptyline concentration of 100 ppm and an influent flowrate of 2 mL/min. Generally, higher adsorption capacity and longer breakthrough times were achieved with a longer bed and lower initial concentrations. The Log Bohart-Adams model accurately described the breakthrough curves, demonstrating the graphene material's effectiveness. The obtained results highlight the potential of the as-synthesised 3D heteroatom-doped GO composites for the effective continuous removal of TCA pharmaceutical pollutants from wastewater.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Lee, Lai Yee Gan, Suyin Thangalazhy Gopakumar, Suchithra
Keywords:	3D graphene materials; heteroatom doping; nanocomposites; water pollution; pharmaceuticals; wastewater treatment; adsorption
Subjects:	T Technology > TP Chemical technology
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Engineering > Department of Chemical and Environmental Engineering
Item ID:	81522
Depositing User:	TEE, Wan
Date Deposited:	26 Jul 2025 04:40
Last Modified:	26 Jul 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/81522

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