Chapter 1
Preparation, Characterization, and Applications of Nanomaterials (Cellulose, Lignin, and Silica) from Renewable (Lignocellulosic) Resources
K.G. Satyanarayana1*, Anupama Rangan2, V.S. Prasad3 and Washington Luiz Esteves MagalhĂŁes4
1Poornaprajna Institute of Scientific Research (PPISR), Bangaluru, Karnataka, India
2Department of Pharmaceutical Chemistry, Vivekananda College of Pharmacy, Bangalore, India
3Chemical Sciences & Technology Division, National Institute for Interdisciplinary Science & Technology (NIIST-CSIR), Thiruvananthapuram, Kerala, India
4Department of Technology of Forestry Products, Embrapa Forestry, Colombo PR, Brazil
Abstract
Safer ecological/environmental requirements have necessitated the use of renewable bioresources to address the issues of sustainability of the resources. In this perspective, biomass is attractive due to its abundance, renewability, and low cost. However, there are some limitations for industrial uptake of materials derived from biomass for structural and other applications. As the demand for developing functional materials increases, macro- to nanosize reduction of materials provides an alternative for varied applications presenting advantages in behavior and functionality. This has triggered development and use of nanomaterials along with the need to find new sources to produce them. While most of nanofibers from lignocellulosic materials refer to nanocellulose (NC), there have also been attempts to obtain nanolignin and nanosilica from wood and similar materials. Surface modification and functionalization of NC from various sources including natural fibers can lead to various nanomorphologies which have potential for application in storage and delivery of drugs and cosmetics. Lignin is the second most abundant natural renewable biopolymer. Recent advances in bioengineering and biotechnology have brought lignin into the limelight as a value-added product in spite of this being mostly regarded as an undesired by-product. Silica with high purity and amorphous nature has many industrial applications. With the progress of nanotechnology and increase in demand, several silica-processing industries have started producing nanosilica particles. Accordingly, this chapter presents preparation methods of cellulose, lignin and silica in nanoform, their characterization, and applications.
Keywords: Nanomaterials, biomass, cellulose, lignin, silica, processing, structures and properties, applications
1.1 Introduction
Nano-based manufactured goods and nanotechnology has been gaining increased attention in the recent times. Indeed, nanotechnology is significantly affecting design and use of many products and processes across varied fields of scientific research and industrial applications. Greater expectations have been put forth on various aspects of nano-related things (science of nanomaterials, nanotechnology including nano-manufacturing, etc.) not only in the academic community, but also among investors, governments, and industrial sectors (Serrano et al., 2009; Tuuadaij & Nuntiya, 2008; Lin et al., 2011a,b). Reasons for this are obvious in that nano-related materials and processes exhibit unique characteristics. Nanomaterials exhibit enhanced properties and performance, while the technology provides approaches to fabricate new structures at atomic scale (Thakur et al., 2012a,b, 2014a,b). Although there are some limitations for industrial uptake of materials derived from biomass for structural and other applications, the demand for development of functional materials is increasing probably due to reduction in the size of these materials below the normal micro level. This offers advantage in behavior and functionality exhibited by the nanosized materials based on biomass. One of the applications of nanotechnology in the area of biomass has been the development of nanocellulose (NC) in virtue of its super functionalities, such as its extremely large, active surface area, and low cost (Hubbe et al., 2008; Yano et al., 2005). Thus, new world of novel materials and devices has arrived showing greater application potential than that was possible hitherto with normal materials and processes. In fact, these nano-related materials have already attained industrial and economic reality. Worldwide annual sources of naturally occurring nanoparticles is estimated to be the lowest from biomass with about 1.8 million tons, compared to 16.8 million tons from mineral aerosol and 3.6 million tons from marine salts (Gaffet, 2011). This large measure of nanoparticles highlights their possible applications in a variety of fields aiming at manufacturing or modifying available material resources for a variety of technological uses (Senff et al., 2010).
While this is the status of emerging materials and technology, many countries are projected to face sustainability issues in the coming years. The diminishing natural sources coupled with the increasing demand for clean and safer energy alternatives have necessitated the development of novel approaches using biodegradable renewable resources. The idea of shifting to renewable resources to produce fuel and value added products from lignocellulose is being explored extensively. This is because lignocellulose is the most abundant renewable biomass on earth and is mainly composed of cellulose, hemicelluloses and lignin. Cellulose and hemicellulose fractions are polymers of sugars and are potential sources of fermentable sugars. Lignin can be used for the production of chemicals, low end products such as adhesives as well as for generation of heat and power applications (Harmsen et al., 2010). The overall objective for research in this field is to prepare the required biomaterials from agro-industrial lignocellulosic wastes like sugar bagasse, wood residues, agricultural residues etc. There is a dire need for efficient technologies to be introduced using these lignocellulosic wastes as they are abundant, inexpensive and offer a distinctive resource for large-scale and cost-effective technologies, besides meeting the industrial demands for renewable resource.
At a more fundamental level, lignocellulosic biomass is made up of nanometer-size constitutive building blocks that provide mechanical strength besides serving multiple functions. In nature there are many examples of such efficient and optimized systems that are based on nanotechnology (Avila-Olias et al., 2013). Indeed, some of the inherent properties of the naturally occurring biomaterial composites such as bone, teeth or the shells of marine animals can be directly correlated to the nanometer dimensions of their building blocks (Sarikaya et al., 2003). Thus, it is logical to explore the use and application of nanotechnology-based methods as a promising approach for efficient utilization of the lignocellulosic resources. However, the complex structure of lignocellulose where the carbohydrates such as cellulose and hemicelluloses are extensively cross-linked with lignin acts as a barrier for efficient degradation of the lignoce...