3.2.2. MNPs for removal of organic contaminants

3.1. Different types of magnetic materials for water treatment

66 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment

treatment.

thermally stable as well as biocompatible.

3.2.1. MNPs for the removal of metals

3.2. Use of magnetic materials for clean water technology

Different types of magnetic materials have been synthesized and designed for development of advanced materials and applied effectively in widespread uses such as biomedicine, magnetic resonance imaging (MRI), catalysis, spintronics, robotics, engineering, environmental remediation, etc. [22] There are different synthesizing methods viz. co-precipitation, solvothermal, hydrothermal, microemulsion, sonochemical, etc. which determine their particle size, distribution, morphology, surface functionality, and magnetic properties and in turn of their various application [22]. Magnetic materials are made from mixtures of metals of iron, cobalt, nickel, and alloys and their oxides (of the type MFe2O4, where M is a metal). Out of these materials, iron (zero valent iron) and its oxides, i.e., usually γ-Fe2O3 (maghemite) and Fe3O4 (magnetite) nanoparticles have attained significant interest in recent years and have been used for water treatment processes. The various composite magnetic materials such as Fe3O4@C [23, 24], Fe@SiO2 [25], Fe3O4@TiO2 [26], Fe3O4@PPO (poly(propylene oxide)), PEO (poly(ethylene oxide) [27], Fe3O4@PDA (polydopamine) [28], Fe3O4@PNIPAM (poly(N-isopropylacrylamide)) [29], Fe3O4@MIPs (molecularly imprinted polymer-encapsulated particles) [30], Fe3O4@CNTs (multiwalled carbon nanotubes) [31], Fe@CS (carbon spheres) [32], Fe/iron oxide-oxyhydroxide/rGO (grapheme) [33], etc. have been used for environmental applications. Singh and his co-workers synthesized a series of magnetic nanocomposites such as CoFe2O4–ZnS [34], Fe3O4@GTPs (green tea polyphenols) [35], Fe3O4–Cr2O3 [36], CoFe2O4-Cr2O3-SiO2 [37] and applied for wastewater

In addition to their suitable magnetic properties, i.e., ferrimagnetic, ferromagnetic and superparamagnetic (nanoparticle size less than 10 nm), their synthesis procedure is simple and costeffective and they can be easily functionalized as desired for many applications. The size and shape and magnetism of these magnetic materials can be easily controlled based on their application and thus they can be easily dispersed in liquid medium and their stability can be retained for multiple uses. Moreover, these materials are non-toxic or less toxic, chemically inert,

Appearance of water pollution as a global threat demands the development of low-cost and reliable materials for effective waste water remediation. The magnetic materials have been used for clean water technology for both in laboratory as well as field scale [38, 39]. In recent years, iron oxide nanomaterials have been used as adsorbent or immobilizing agent and

Heavy metal contamination in water such as cadmium, zinc, lead, chromium, nickel, copper, vanadium, platinum, silver and titanium due to industrial activities is significantly increasing which is detrimental to human beings and animals. Magnetic nanomaterial adsorbents have been potentially used for removal of metallic ions such as Cr(VI), Cu(II), Co(II),Cd(II), As(V), As(III) and Hg(II) in water [41, 42] which are more effective as compared to micron size particles. The magnetic chelating resin based materials have been used for effective removal

photocatalyst or the both depending on nature of contaminants in water [40].

Magnetic nanoparticles are used as an adsorbent for the removal of various dyes and dyes stuff from aqueous solution. Removal of dyes from waste water has become a serious issue of concern because of its harmful impact on human. Dyes basically can be classified in to two categories, i.e., anionic dyes and cationic dyes.
