REPOSITORY > RESULTS

Abstract

Environmental contamination by toxic metals—such as Pb²⁺, Cr³⁺, and Hg²⁺—and organometallic species like monomethylmercury (MeHg) presents one of the most persistent global challenges due to their bioaccumulation, long-term toxicity, and resistance to degradation. This thesis addresses this critical issue through a multidisciplinary approach combining nanotechnology, environmental chemistry, biosensor engineering, and sustainable materials science.
The first part of this work investigates the synthesis and functionalization of nanostructured adsorbents for efficient toxic metal removal. Amino-functionalized SiO₂ nanoparticles and γ-Fe₂O₃@NH₂ magnetic nanoparticles were developed and evaluated for their metal ion adsorption efficiency under varying environmental conditions. These materials demonstrated excellent performance in removing Pb²⁺, Cr³⁺, and Hg²⁺, with enhanced selectivity, regeneration capability, and recyclability—paving the way for practical use in decentralized water treatment systems.
Building on this, superparamagnetic spinel ferrite nanomaterials were engineered for dual-functionality: remediation of Hg²⁺ and recovery of valuable rare earth elements (REEs) such as Dy³⁺ and Tb³⁺. Characterized by sol–gel auto-combustion synthesis, these nano-adsorbents offered high adsorption capacity, Langmuir-type isotherm behavior, and environmental safety validated through ecotoxicity testing. This supports a circular economy framework in pollutant management.
The second core of the thesis centers on the development of a highly sensitive and selective biosensor for the detection of MeHg, a compound known for its neurotoxic and teratogenic effects, even at femtogram levels. As part of the H2020-MSCA-ITN GMOS-Train project, MerB (organomercurial lyase), a bacterial enzyme evolved for MeHg detoxification, was cloned, expressed, and immobilized on gold nanoparticle-modified screen-printed electrodes using Ni²⁺-chelating linker chemistry. The resulting biosensor demonstrated unprecedented sensitivity—capable of detecting MeHg at 3 femtograms—with high selectivity and no interference from inorganic Hg²⁺.
Electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed the redox activity and conformational changes of MerB upon MeHg binding, establishing real-time quantitative readout capabilities. The biosensor proved portable, cost-effective, and user-friendly, with successful trials in environmental and fish tissue matrices—offering a transformative alternative to labor-intensive techniques like CVAFS and ICP-MS.
Overall, this thesis delivers a unified platform of smart nanomaterials and biosensors for comprehensive toxic metals and MeHg management. It bridges molecular biology with advanced materials and electrochemical engineering, contributing significantly to sustainable development goals, public health protection, and global mercury monitoring in alignment with the Minamata Convention.