Differentiating Nanomaghemite and Nanomagnetite and Discussing Their Importance in Arsenic and Lead Removal from Contaminated Effluents: A Critical Review

Abstract

Arsenic and lead heavy metals are polluting agents still present in water bodies, including surface (lake, river) and underground waters; consequently, the development of new adsorbents is necessary to uptake these metals with high efficiency, quick and clean removal procedures. Magnetic nanoparticles, prepared with iron-oxides, are excellent candidates to achieve this goal due to their ecofriendly features, high catalytic response, specific surface area, and pulling magnetic response that favors an easy removal. In particular, nanomagnetite and maghemite are often found as the core and primary materials regarding magnetic nanoadsorbents. However, these phases show interesting distinct physical properties (especially in their surface magnetic properties) but are not often studied regarding correlations between the surface properties and adsorption applications, for instance. Thus, in this review, we summarize the main characteristics of the co-precipitation and thermal decomposition methods used to prepare the nano-iron-oxides, being the co-precipitation method most promising for scaling up processes. We specifically highlight the main differences between both nano-oxide species based on conventional techniques, such as X-ray diffraction, zero and in-field Mössbauer spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism, the latter two techniques performed with synchrotron light. Therefore, we classify the most recent magnetic nanoadsorbents found in the literature for arsenic and lead removal, discussing in detail their advantages and limitations based on various physicochemical parameters, such as temperature, competitive and coexisting ion effects, i.e., considering the simultaneous adsorption removal (heavy metal–heavy metal competition and heavy metal–organic removal), initial concentration, magnetic adsorbent dose, adsorption mechanism based on pH and zeta potential, and real water adsorption experiments. We also discuss the regeneration/recycling properties, after-adsorption physicochemical properties, and the cost evaluation of these magnetic nanoadsorbents, which are important issues, but less discussed in the literature.

Raman, TEM, EELS, and Magnetic Studies of a Magnetically Reduced Graphene Oxide Nanohybrid following Exposure to Daphnia magna Biomarkers

“…In addition, it should be mentioned that not only the hyperfine parameter values of = 0.34 mm/s and = 0.41 mm/s, with B hf,A = 50.7 T, and B hf,B = 52.9 T, are close to those values of the bulk γ-Fe 2 O 3 phase, the RRA values are also equal to those found in the bulk-like phase (36.9% for the site A and 63.1% for the site B [ 9 , 29 ]); consequently, these findings are finger prints for well-crystallized and chemically stable γ-Fe 2 O 3 NPs in the ternary nanocomposite even after being exposed and recovered from the ecotoxicological assays. These results also agree with the EELS analysis discussed above.…”

“…From the evolutionary point of view, changes, adaptations, and phenotypic variations are fundamental features to be modeled and studied during an ecotoxicology analysis due to its important location in the trophic chain when nanomaterials are used for water cleaning processes of real effluents [ 3 , 4 , 5 ]. For instance, recent advances and developments in several nanohybrids for the removal of toxic metals and other organic hazardous materials suggest their final spreading into water bodies, soils, various effluents, and the construction industry [ 6 , 7 , 8 , 9 , 10 ], a condition that requires tests of their ecotoxicological effects. For example, cytotoxic and morphological analyses have been studied [ 11 , 12 , 13 , 14 , 15 ], but lethal concentrations ( LC 50 , mg L −1 ) need to be established and will depend on the developed nanoadsorbents (nanocomposite).…”

A Ferrofluid with High Specific Absorption Rate Prepared in a Single Step Using a Biopolymer

“…The uncoated MNPs show (top spectrum) diffraction peaks at 30.2 • , 35.7 • , 43.4 • , 57.4 • , and 62.9 • associated with the respective diffraction planes (220), (311), (400), (333), and (440), which correspond to the face-centered cubic structure of Fe 3 O 4 [18]. As is explained in [19], the XRD technique must be complemented (in further experiments) with Mössbauer spectroscopy to determine the presence of maghemite in the samples. In the same figure, the diffractogram of MNP-GA1 and MNP-GA2 are plotted with the dark and red lines, respectively, and both spectra exhibit the same peaks as the uncoated MNPs.…”

Invasive plants as biosorbents for environmental remediation: a review

“…Lead also links to several adverse effects on the intelligence quotient degrees and physical growths in children (Kuang et al 2020;Naranjo et al 2020). Over the decades, lead can be released from the environment through human activities such as transportation, agriculture, ceramic, and battery productions (Ramos-Guivar et al 2021). The presence of lead in wastewater is impactful because it can cause long-term accumulation and enter the human body through the food chains and contaminated water (O'Connor et al 2020;Jarvis and Fawell 2021).…”