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Engineered magnetic biochar (EMB) is a multifunctional material that has gained increasing attention in environmental and industrial applications. This review explores various synthetic methods, and diverse applications of EMB, focusing on its enhanced potential for environmental remediation, and water treatment. The incorporation of metal, various functional groups along with magnetic nanoparticles into biochar matrices provides EMB with unique properties, enabling efficient adsorption of heavy metals, organic contaminants, and pollutants from aqueous solutions. There are extensive literature reports on the development of such engineered magnetic biochar adsorbents for effective and selective removal of a wide range of inorganic pollutants including heavy metals and inorganic ions from water. This article encompasses all the techniques which have been utilized for the engineering of the pristine magnetic biochar and its application specifically in heavy metal removal from water and summarizes the latest innovative research and knowledge in this field. Due emphasis has been shed on elaborating the mechanisms involved in the adsorption of inorganic pollutants, specifically heavy metals by these efficient materials. Until now, to the best of our knowledge, no review on tailored magnetic biochar covering the surface engineering techniques and adsorption mechanisms has been penned. In addition to shedding light on the fundamental aspects, this article also provides a critical comparison of these adsorbents with the literature reported ones which clearly highlight their efficacy and offers insights into the current advancements, challenges, and future prospects of EMB, emphasizing its potential to address environmental and agricultural sustainability challenge. [Display omitted] • A one-stop-reference for removal of heavy metals using modified magnetic biochar. • Succinct overview of innovative synthetic techniques including microwave technology. • Detailed account of the strategies used for surface engineering of magnetic biochar. • Deep insights into the mechanistic aspects involved in the adsorption processes. • Includes comparison of the modified magnetic biochar with other adsorbents. [ABSTRACT FROM AUTHOR]

The response of a typical ferrofluid (FF) lies in its explicit property of chain formation of magnetic nanoparticles. The most significant magneto-optic (MO) and magneto-viscous (MV) effects of FF are attributed to chaining effect. In the present research, an effort was made to analytically justify the dependence of the structure evolution of FFs on different measurable parameters involved in MO and MV effects. The problem is treated with the help of dimensional analysis and an empirical relation is formulated relating the equilibrium chain length with Verdet coefficient (constant), particle diameter, viscosity of the carrier fluid, particle density, magnetization and shear rate. The formulated relation of chain length is supported by error analysis to yield the uncertainty in the result. The maximum uncertainty in four sets of data is found as ∼0.75. [ABSTRACT FROM AUTHOR]

SQUID magnetometry and electron magnetic resonance (EMR) spectroscopy at 9.28 GHz were employed to probe magnetism and surface spin disorder in Fe3 O4 nanoparticles. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed magnetite particles with size ≃8 nm. Magnetization (M) versus temperature studies yielded blocking temperature TB ≃ 170 K in H = 50 Oe. For T > TB, M scales approximately as H/T with μP ≃ 5400 μB as the magnetic moment/particle. At 5 K, the magnitudes of hysteresis loop parameters viz. coercivity Hc ≃ 37 Oe and saturation magnetization M8 = 62 emu/g are considerably smaller than the reported values for larger 150 nm Fe3 O4 particles. In EMR studies, a single symmetric line at g ≃ 2.11 with linewidth ΔH = 850 Oe is observed at 300 K with the g-value and ΔH increasing with decreasing T. These results are interpreted in terms of a disordered surface spin layer of 0.5 nm thickness. [ABSTRACT FROM AUTHOR]

In this paper, we compare the magnetic relaxation of DNA-coated γFe2 O3 with that of parent 7-nm γFe2 O3 particles by measuring the temperature dependence of AC susceptibilities (χ′ and χ″) at frequency f = 0.1, 1, 10, 100, and 1000 Hz and electron magnetic resonance (EMR) at 9.28 GHz. Changes in the blocking temperature TB (where χ′ peaks) with frequency are analyzed using the relation: TB = Ta + [T0/ln(f0/f)] derived from Vogel-Fulcher relaxation, where Ta(T0) measures the effective energy barrier (interparticle interaction). The fit to the data yields f0 = 1.3 × 1016 Hz, Ta = 2760 K(2960 K), and T0 = 40 K(20 K) for the uncoated (DNA-coated) γFe2 O3. From the relative shift ΔTm of Tm (the temperature where χ″ peaks) with change Δ log f in frequency, the parameterΦ = ΔTm/(TmΔ log f) is determined to be 0.04(0.06) for the uncoated (coated) ΔFe2 O3. These results show only minimal changes in the magnetic dynamics of γFe2 O3 upon DNA coating. [ABSTRACT FROM AUTHOR]