Correction: Mubarak et al. Enhanced Performance of Chitosan via a Novel Quaternary Magnetic Nanocomposite Chitosan/Grafted Halloysitenanotubes@ZnγFe₃O₄ for Uptake of Cr (III), Fe (III), and Mn (II) from Wastewater. Polymers 2021, 13, 2714

In the original publication, there was a mistake in Figures 5 and 8 as published [1].

The corrected version is displayed below.

• 3.1.3. X-Ray Diffraction (XRD)

The X-ray diffraction (XRD) patterns for chitosan, halloysite, and Zn@Fe₃O₄ material provide clear insights into their structural characteristics. The XRD pattern of chitosan shows distinct peaks at 2θ = 9.24° and 17.5°, which correspond to the (010) and (020) diffraction planes. These peaks confirm the semi-crystalline nature of chitosan, with broadening indicating the transformation from the crystalline structure of chitin to the more amorphous structure of chitosan. For halloysite, characteristic reflections at 2θ values of 11.08°, 21.42°, 27.45°, and 32.47° highlight its tubular structure and the crystallinity of this natural nanomaterial. Zn@Fe₃O₄ nanoparticles exhibit broad peaks at 2θ = 24.14°, 31.86°, 42.50°, 56.3°, and 61.787°, which are associated with the (210), (220), (400), (511), and (440) planes, confirming the formation of the ZnγFe₃O₄ phase, where zinc is doped into the magnetite (Fe₃O₄) structure. This confirms the formation of a well-integrated composite material with strong interactions between its components [38–40].

Figure 5. X-ray diffraction (XRD) patterns for chitosan, halloysite, Zn@Fe₃O₄, and composite.

Figure 5. X-ray diffraction (XRD) patterns for chitosan, halloysite, Zn@Fe₃O₄, and composite.

• 3.1.7. TEM

Transmission electron microscopy (TEM) was used for the morphological study of loaded and discharged ZnγFe₃O₄ halloysite tubes. The TEM image shows halloysite nanotubes as elongated, cylindrical rods, with diameters ranging between 40 and 80 nm and lengths varying from 500 to 1000 nm (Figure 8). The nanotubes are surrounded by clusters of smaller particles, possibly indicating surface interactions or modifications. The TEM images of the loaded halloysite ZnFe₃O₄ have a morphology, validated by TEM analysis, that is random and free of any defects (i.e., beads, globules, and undefined form). It can be concluded that the ZnγFe₃O₄-loaded halloysite has similar morphological characteristics (Figure 8). ZnγFe₃O₄ was filled with average diameters of 150 ± 45 nm.

Figure 8. TEM of (a) halloysite and (b) magnetic halloysite.

Figure 8. TEM of (a) halloysite and (b) magnetic halloysite.

The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.