**1. Introduction**

Environmental pollution caused by heavy metals is a serious problem and has been the focus of worldwide concern. The chemical effect of these metals has been of great environmental interest due the fact these metals are not biodegradable, which means they have cumulative effects in organisms, causing serious damage to health [1, 2]. Among several metals, manganese and nickel are considered highly toxic. Both are contained in wastewater from galvanoplasty as a consequence of the electrodeposition processes and other metallic surface treatments to prevent corrosion [3]. The main harmful effects caused by these metals are cancer, pulmonary lesions and central nervous system damages [4].

There are several methods for the removal of ions from aqueous solutions, such as reverse osmosis, ion exchange, precipitation, electrodialysis and adsorption [5]. Among these methods, adsorption is the most versatile and widely used to remove various pollutants [6]. Methods to remove heavy metals using low-cost adsorbents have been successfully developed, as shown in the literature [7–9].

Natural polymers like alginate (polyanion) are receiving growing attention due to their strong affinity for heavy metal ions. The absorption capacity, specifically of hydrogel in particle form, is comparable to or even better than commercial ion exchange resins. Furthermore, these materials are abundant, biocompatible and environmentally friendly, which make them potential adsorbents for removal of pollutants from wastewater [10].

Accordingly, economically feasible materials that provide efficient removal of these metals from wastewater are being widely studied. The adsorption described in this article is used as a cost-effective way to remove heavy metals, making it competitive with the conventional technology. The proposed adsorbent, consisting of hydrogel based on alginate, a natural anionic polymer, is widely studied to remove heavy metals, since it is nontoxic, inexpensive and highly efficient regarding adsorption [2].

Alginate is a linear copolymer composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G) subunits. It can be used in several fields, like the food, pharmaceutical biomedical industries, for purposes such as drug delivery, sensorial enzyme encapsulation and development of contrast agents for diagnostic imaging. Moreover, alginates have been proven to be outstanding for water purification. Research has also demonstrated that gel beads of calcium alginate can remove heavy metals from wastewater [11].

Nevertheless, the separation of the loaded biomaterials from the medium is often a problem. So, the use of magnetic adsorbents (called here magsorbents) to solve this technical problem has received considerable attention in recent years [12].

Magnetic nanoparticles are embedded in polysaccharides to raise their capacity as biosorbents. Also, they are very useful in the isolation or recovery process of gel beads. Papers have been published describing the removal of heavy metal ions using maghemite and alginate, as magnetic and encapsulating material, respectively [13].

Idris et al. [2] prepared magnetic alginate beads by insertion of nanoparticles of maghemite in chains of sodium alginate, aiming to remove ions of Pb (II) from aqueous solutions. Physicochemical parameters, such as pH, initial metal concentration and contact time were studied. The results revealed that 95.2% of Pb (II) was removed in 2 hours at pH 7, and the maximum adsorption capacity was 50 mg g−1. Furthermore, the presence of magnetic particles in hydrogel beads enabled the easy isolation of the beads after the sorption process. The results showed the potential of using magnetic beads to treat wastewater containing heavy metals.

However, to the best of our knowledge, not studies have been published about the synthesis of hydrogels based on calcium alginate along with γ-maghemite nanoparticles prepared in situ (preparation method in a single step) to remove heavy metals from industrial wastewater. The existing works first synthesize the gamma-maghemite by the co-precipitation process and then add it to the hydrogel (two-step preparation method). Moreover, in our study, the adsorption kinetic in function of hydrogel mass and the competitiveness between the metals (adsorption mechanism) were evaluated.

*Nanomagnetic Polymeric Absorbent Based on Alginate and Gamma-Maghemite Synthesized… DOI: http://dx.doi.org/10.5772/intechopen.98611*
