Magnetic ferrite nanoparticles have a broad application in wastewater treatment, and the interest in applying these particles specifically in waste treatment is growing. However, the gap in understanding how ferrite properties that are controllable through synthesis methods affect wastewater treatment efficiency needs to be better explained. In this review, we assess the analysis of the most impactful publications to highlight the controllable ferrite nanoparticles’ properties through the different synthesis methods and their parameters connected to wastewater treatment efficiency. For a long time, ferrite nanoparticles were seen as adsorbents suitable for physically removing pollutants, but recent studies show that these nanostructures could be suitable for UV and visible light-induced photocatalytic decomposition of contaminants.

In this study we examined the influence of ultra-small gold and magnetite‑gold nanoparticles (NPs) stabilized with d,l-methionine, Fe₃O₄@Au@Met, on their antibacterial efficacy against three of twelve the worst bacterial family members included in the World Health Organization (WHO) list. In particular, gram-negative Acinetobacter baumannii, Salmonella enterica and gram-positive methicillin-resistant Staphylococcus aureus and Micrococcus luteus were tested. Apart from the synthesis, gold species reduction and NP stabilization, an excess of methionine has been used herein to detach ultra-small gold NPs from the Fe₃O₄@Au@Met surface, collect them and investigate. The antimicrobial efficiency of the ultra-small (Ø ~ 1.8 nm) Au@Met NPs and Fe₃O₄@Au@Met NPs was evaluated through the quantitative analysis by comparing with that of naked magnetite NPs, d,l-Met and BSA. It has been determined that compared with the control sample, 70 mg L^-1 probe of Au@Met NPs exhibited the killing efficiency of 84.4-58.5% against gram-negative bacteria and 89.1-75.7% against gram-positive bacteria. The composition, structure, and morphology of the synthesized and tested herein NPs were investigated by inductively coupled plasma optical emission spectrometry, magnetic measurements, FTIR, XRD, XPS, AFM and HRTEM.

We report the design and methodology for functionalization of the surface of small Co-ferrite nanoparticles with a mean size of up to 5.0 nm through the attachment of vitamin C molecules initiating [AuCl₄]⁻ reduction and the subsequent deposition of gold. By this method, Co-ferrite-Au nanoparticles have been fabricated for the first time in a simple and controllable manner, consisting of the determination of the consumed ascorbic acid content. The sequential addition of vitamin C and HAuCl₄ to the ferrofluid at low concentrations leads to the formation of a gold shell on the ferrite core. This approach avoids the additional stabilization of ferrite nanoparticles before gold deposition, and is of great importance in view of the preparation of biodegradable superparamagnetic particles for nanomedicine applications. The deposition of gold onto the ferrite surface was proved herein by UV-vis absorption and energy-dispersive X-ray (EDX) spectroscopy, inductively coupled plasma mass spectrometry analysis, atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM) and Mössbauer spectroscopy.