Table 1.

Highlights of laboratory-scale adsorption performance of selected magnetic nanoadsorbents for micropollutants

Adsorbent	Micropollutant	Highlights of adsorption behavior	References
Magnetic CrFe2O4 nanocomposite prepared sonochemically using a nonionic surfactant	Mo6+	Thermodynamic data indicated that adsorption of Mo6+ ions was spontaneous and endothermic	Gamal et al. (2021)
		The adsorbent could be regenerated through the desorption of more than 98% of Mo6+ with 1.0 mol L−1 sodium hydroxide
Magnetic nanocomposite Co-multiwalled carbon nanotubes	Methylene blue	Maximum adsorption capacity=324.34 mg g−1	Çalımlı (2021)
		Adsorption was endothermic and followed pseudo-second-order kinetic model
Fe3O4-MnO2-EDTA composite	Cu2+ ions from binary or ternary metal adsorbate system	As-synthesized adsorbents yielded high Cu2+ selective adsorption (both in binary and ternary systems)	Chen and Xie (2020)
		In comparison with Fe3O4-MnO2, the magnetic Fe3O4-MnO2-EDTA nanoparticles resulted in rapid magnetic separation with high selectivity for Cu2+
Magnetic CoFe2O4/graphene oxide adsorbents	Methylene blue, methyl orange and Rhodamine B	Adsorption of organic dyes for CoFe2O4/graphene oxide composite mainly attributable to contribution of graphene oxide	Chang et al. (2020)
		Superior adsorption capacity qe(max) for methylene blue and Rhodamine B at 355.9 mg g−1 and 284.9 mg g−1, respectively (Langmuir adsorption model).
		Selective adsorption with order of adsorption capacity as follows: Methylene blue > Rhodamine B > methyl orange
Hydroxypropyl-β- cyclodextrin-polyurethane/graphene oxide magnetic nanoconjugates	Cr6+ and Pb2+	Adsorption capacity of adsorbents for Cr6+ and Pb2+ at 987 mg g−1 and 1399 mg g−1, respectively, and adsorption followed pseudo-second-order kinetics	Nasiri and Alizadeh (2021)
		Reusability of adsorbent makes it a promising candidate for Pb2+ removal from aqueous solutions
		This magnetic composite was endowed with a high adsorption performance and good reusability for heavy metal ions
Magnetic molecular imprint polymer networks synthesized from vinyl-functionalized magnetic nanoparticles	Antibiotics (ciprofloxacin and erythromycin)	Networks exhibited high binding capacity toward erythromycin and ciprofloxacin at 70 mg g−1 and 32 mg g−1, respectively.	Kuhn et al. (2020)
		Networks were recyclable and retained their binding capacity after 4 cycles
		Results demonstrated that the networks developed had high binding capacity, selectivity and recyclability
		The networks can be utilized both for monitoring and removal of hazardous antibiotic pollutants potentially present in different samples and food products
Phosphoramide-functionalized magnetic nanoparticles	Uranium	High maximum adsorption capacity=95.2 mg U g−1 sorbent	Singhal et al. (2020)
		80% adsorption achieved for pH 4–8 with maximum adsorption observed at pH 6
		Higher than 90% uranium extraction was recorded during adsorption studies conducted using drinking water, tap water and seawater
		Inferences were made in the study as follows: high adsorption capacity, low cost, less equilibration time, easy separation from matrix and non-toxicity of the adsorbent constitute some key merits sought when envisioning the process at an industrial scale
Magnetic tubular carbon nanofibers	Cu2+	Maximum adsorption capacity of nanofibers for Cu2+=375.93 mg g−1	Ahmad et al. (2020b)
		Porous morphology, large surface area and tubular structure of the nanofibers contributed to the rapid and highest adsorption of Cu2+ ions
		Langmuir adsorption isotherm model best described adsorption data
		The nanofibers developed have exhibited excellent regenerability when treated with EDTA
Magnesium–zinc ferrites	Cr6+ and Ni2+	Mg0·2Zn0·8Fe2O4 yielded best adsorption capacity (30.49 mg g−1)	Tatarchuk et al. (2021)
		Mg0·4Zn0·6Fe2O4 was observed to be the most effective adsorbent for removing Ni2+ (93.2%)
		Adjustment of magnesium content to an optimal value can enhance mixed ferrites’ ability to remove heavy metals from aqueous solutions
Sulfur-functionalized polyamidoamine dendrimer/magnetic Fe3O4 hybrid materials	Hg2+ and Ag+	Maximum adsorption capacity for Hg2+ and Ag+ was 0.8 mmol g−1 and 1.29 mmol g−1, respectively	Luan et al. (2021)
		Good adsorption selectivity (100% selective adsorption of Hg2+ in the presence of Ni2+, Zn2+ and Mn2+)
		Excellent regeneration characteristics, and reuse repeatedly over four use cycles
Magnetic sodium alginate (SA)-based Fe3O4@SA-Ca gel beads	Direct Orange 26 in aqueous solutions	Gel had ultrahigh adsorption capacity of 1252 mg g−1	Li and Lin (2021)
		Dye removal efficiency=96.2 % (298 K, 50 mg polymer dosage, 2.6 g L−1 initial dye concentration, pH 2.0, 90 min adsorption time)
		Adsorption was spontaneous and exothermic
		Gel was easily separated and recuperated from aqueous solutions without secondary pollution

EDTA Ethylenediaminetetraacetic acid, SA Sodium alginate