# In Situ and Partial In Situ Synthesis of Cellulose Magnetic/Maghemite Composites
## 1 Introduction  
Cellulose is a natural polysaccharide that is in high demand in many industries. It is present in almost every sphere of human life, starting from the paper and packaging sector, textile industries, agriculture and food production, chemical and oil industries, wastewater treatment, biomedicine, cosmetics and healthcare, and electronic devices. The utilization of cellulose-based products offers a variety of environmental and economic benefits. Considered an abundant organic polymer in nature, cellulose has also been studied and applied as a precursor for functional composite materials [1]. Several scientific studies show that cellulose can form composites with various materials due to good mechanical properties, a large surface area, and biodegradable and renewable properties [2]. Besides these, cellulose contains powerful intra- and inter-molecular hydrogen bonds owing to plenty of hydroxyl groups, which may be an important factor in anchoring iron oxides [3]. Iron oxides, whether monodispersed or polydispersed, have attracted increasing attention due to their excellent biocompatibility, low toxicity, and magnetic properties. They have considerable potential for use in the biomedical industry, especially in recent years due to increasing the frequency of some types of diseases [4] (magnetic resonance imaging, targeted drug delivery, cell separation, and hyperthermia treatment), the electrical industry (electric motors and power transformers), magnetic recording, information storage media, and environmental processes (treatment of wastewater) [5, 6]. The main oxides of iron are hematite (\(\alpha\)-Fe\({}_{2}\)O\({}_{3}\)), maghemite (\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)), magnetite (Fe\({}_{3}\)O\({}_{4}\)), ferrite (Fe\({}_{2}\)O\({}_{4}\)), wustite (Fe\({}_{1}\)-xO), and the oxide hydroxides (geotheite: \(\alpha\)-FeOOH, lepidocrocite: \(\gamma\)-FeOOH, akaganeite: \(\beta\)-FeOOH) [6]. Hematite, maghemite, magnetite, and ferrite are interesting for their high magnetization (saturation magnetization is higher than 60 emu/g), and goethite, lepidocrocite, and akaganeite for their superparamagnetic properties, as well as for the existence of hydroxyl groups that can create chemical bonds with other compounds [7,8]. Cellulose-iron oxide composites have been studied in the last few years to be of interest as transparent films for magnetic and/or optical applications, magnetic resonance imaging (antibacterial or contrasting materials), recyclable catalysts, magnetically retrievable oil adsorbents, or magnetic aerogels [8]. Composites are obtained by incorporating magnetic particles into the cellulose matrix or by performing in situ synthesis (iron oxides are generated in the presence of cellulose or cellulose is prepared in the presence of magnetic particles) [8, 9, 10]. Due to the distinct synthesis conditions of the two precursors, cellulose, and magnetic iron oxides, in situ synthesis is less commonly used. However, a few examples have been described in the literature. [PERSON] et al. obtained superparamagnetic papers from cellulose fiber suspension with 5-13 wt% ferrite nanoparticles, iron oxides, and mixed oxides (oxides of iron with cobalt and/or nickel) by using a one-cycle in situ synthesis [11]. Magnetic particles are prepared in the presence of suspensions of suitable natural cellulose fibers via careful oxidation of ferrous hydroxide precipitated with sodium hydroxide from the ferrous ions. The saturation magnetization has values between 10 and 15 emu/g (smaller for nickel ferrite and higher for cobalt ferrite). [PERSON] and his colleagues prepared magnetic nanocomposite cellulose/maghemite film by using an in situ synthesis of plate-like Fe\({}_{2}\)O\({}_{3}\) nanoparticles in the cellulose matrix [12].