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 Magalhães4

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

*Corresponding author: gundsat42@hotmail.com, kgs_satya@yahoo.co.in

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 lignocellulosic wastes to obtain value added products. The prospect of obtaining nanounits by systematic breakdown of the larger biopolymer is still an emerging and challenging field that holds great promise of revolutionizing utilization of lignocellulosic materials. In this regard, NC has been extensively studied and it has been used for diverse applications (Charreau et al., 2013).

With the above background of safer ecological/environmental requirements leading to the demand for the use of renewable bioresources, nanosized cellulose, lignin, and silica can be tapped to address sustainability issues as they offer distinct advantages over other materials. This chapter presents an overview of preparation methods of cellulose, lignin, and silica in nanoform, their characterization, and applications. In addition, market aspects and perspectives for these nanomaterials based on lignocellulosic biomass are also mentioned.

1.1.1 Cellulose and Nanocellulose

Cellulose is the most abundant renewable organic polymer produced in the world. There are two reports giving different amounts of cellulose available with one giving at 1.5 × 1012 tons of the total annual biomass production (Klemm et al., 2005), while the second gives an annual production of more than 7.5 × 1010 tons (Habibi, 2014; Habibi et al., 2009). Sources of cellulose include mainly plants, animals, bacteria, and other organisms being others. Higher production of cellulose comes from pulp mill industry, which produces it from solid wood through chemical digestion. Cellulose is thus not only widely available from renewable sources but its production has low carbon footprint and it is biodegradable. As an inexhaustible sustainable biopolymer, cellulose has remarkable chemical and physical properties that can be utilized for wide range of applications. One example of use of cellulose is as a raw material for various applications including the production of nanocellulose. It may be noted that the source of the cellulose, being renewable and biodegradable, is produced from solid wood through chemical digestion, acidic or alkaline process thus making its production with low carbon footprint. Thus, cellulose is widely available and a low cost material. Hence, cellulose is a fascinating material and almost inexhaustible sustainable polymer, possessing remarkable chemical and physical...