href="#ue5b545b4-c934-5147-99ff-189394f34c02">Chapter 20 briefly discusses textile wastewater treatment technologies, with a primary focus on the potential treatment methods for valorization of sludge. Chapter 21 deals with biofertilizers and their role in the sustainable growth of the agriculture sector. Finally, Chapter 22 presents a detailed overview of the effect of adsorption parameters, such as pH, temperature, time, initial concentration of Cr(VI) and bioadsorbent dose, for maximum removal of toxic chromium.
This book will appeal to a broad readership, including scientists, researchers, scholars, engineers and students from diverse backgrounds interested in the field of biomass valorization. It can also be used as a reference book for undergraduate and graduate courses.
In conclusion, I would like to thank all the authors for writing exciting and informative chapters for this book. Last but not least, my special thanks to Mr. Martin Scrivener, President of Scrivener Publishing, USA, for his very friendly and inspiring cooperation.
Shahid-ul-Islam
IUST
November 2021
1
Photocatalytic Biomass Valorization into Valuable Chemicals
Brajesh Kumar1*, Lovjeet Singh2, Pawan Rekha3 and Pradeep Kumar4
1 Department of Chemical Engineering, National Institute of Technology Srinagar, Hazratbal, Srinagar, Jammu and Kashmir, India
2 Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, Rajasthan, India
3 Department of Chemistry, Malaviya National Institute of Technology, Jaipur, Rajasthan, India
4 Department of Chemical Engineering, Institute of Engineering & Technology, Lucknow, Uttar Pradesh, India
Abstract
With the increasing demands of green and renewable energy sources due to worldwide environmental concern, the valorization of earth-abundant biomass into valuable fuels and chemicals represents an area of tremendous importance in green chemistry. Biomass has potential to be used as a substitute of non-renewable and rapidly depleting fossil fuels. The integration of biomass utilization and photocatalysis appears as a promising technology to obtain higher grade of sustainability in chemical processes. The photocatalytic process is considered among the top green processes because of its feasibility at room temperature and atmospheric pressure. This chapter thus highlights the fundamental concept and basic mechanism of photocatalytic transformation of biomass and biomass-derived chemicals to electricity, hydrogen and fine chemicals. A detailed discussion on the catalyst aspect such as structure activity relationship, band gap tuning and visible light induced activity will be presented. Furthermore, some possible strategies to avoid various challenges in practical applicability of this process are discussed.
Keywords: Renewable energy, biomass, photocatalysts, solar energy, biohydrogen
1.1 Introduction
A wide range of energy that people use in the human habitation and in other necessary spaces is procured from non-renewable sources of energy. As we all know energy extracted from conventional approach (coal, petrol, diesel, natural gas, hydrates, oil, shale, natural bitumen, extra heavy oil, etc.) is reducing day by day due to finite availability on this globe [1]. The reasons behind this energy crisis are given in Figure 1.1. With great benefits, the sources of conventional energy are also creating huge adverse impacts such as global warming and ocean acidification. In global warming, the average temperature of the atmosphere increases which in turn results in many climatic problems such as high speed of melting glaciers, intense storm threat, disbalances in atmosphere’s chemical composition, scarcity of water, possibility of fire in forests, etc. Ocean acidification is the consequence of some anthropogenic excess that is responsible for global warming in which there is release of more amount of carbon dioxide at faster rates. Due to this impact, the pH level of ocean lowers down causing the absorption of carbon dioxide in the ocean water forcefully creating more and more acids in the oceans.
Figure 1.1 Reasons for energy crisis on earth.
The fuels obtained from conventional sources of energy are costly in nature and also influence the global economy. To overcome all these kinds of concerns and keeping an important point of view in mind for the future, there is a great need to focus on research related to renewable sources energy for producing clean and environmental friendly fuels. The possible pathways to obtain fuels from conventional and renewable sources of energy are presented in Figure 1.2.
Figure 1.2 Distribution of sources of energy.
1.2 Renewable Energy Sources: The Great Hope of the Future
To reduce the harmful effects created by the exploitation of conventional sources of energy, there are two prime ways [2]:
1 (i) Find an alternate way to catch the carbon dioxide and release after treatment (generated by fossil fuel consumption) or do not let release carbon dioxide directly into the atmosphere.
2 (ii) To search for other alternative fuels which do not release carbon dioxide gas.
Among the available sources of renewable energy, solar energy and biomass are attaining great attention by researchers worldwide because the combination of solar energy and biomass provides a great platform to pursue a significant research for producing clean and pure renewable fuel.
In solar energy, photons are used to provide heat (low temperature) instead of thermal energy to carry out a chemical reaction and this process is known as photocatalysis (a subcategory of catalysis). There are basically three big advantages of photocatalysis valorization such as purification of air or water, production of clean fuel from renewable sources, and generation of quality chemicals. It is a well-known fact that the less quantity of absolutely freely available solar radiation on the surface is utilizing.
Still, many industries are dependent on the use of conventional fuels due to lack of research in the field of green chemistry in terms of photocatalysis. Plants
