Water scarcity has emerged at the forefront of the world's most critical environmental concerns. In the future decades, the rapid population development in emerging regions will continue to raise the need for clean water from residential, agricultural, industrial, and energy perspectives. Clean drinking water is the most significant factor that influences the quality of life for humans. Nanomaterials are ideal for wastewater treatment due to their potential properties, which include small size, large surface area, high porosity, high catalytic activity, tailorable physical and chemical properties, ease of separation, and reproducibility. These favorable properties of nanomaterials make them an attractive candidate for wastewater treatment. This chapter comprehensively overviews a broad spectrum of nanomaterials in wastewater treatment, including different carbon allotropes (graphene, CNTs, MWCNTs, etc.) and metal oxide nanoparticles. Finally, the prospects of these new generation materials in water and wastewater treatment are also discussed.
TopIntroduction
For the survival of all forms of life on Earth, water is an absolute necessity (Morrison et al., 2020). Two major issues that make water management challenging are the growing need for water and the pollution of water supplies (Elbeltagi et al., 2021). Water scarcity is the most pressing environmental issue of our day. The need for clean water is expected to increase in the next decades for various reasons, including residential, agricultural, industrial, and energy uses. The reason for this is the ever-increasing population of developing nations (Savage & Diallo, 2005). Only Earth qualifies as a habitable planet with its 70% water content (Pradeep & Anshup, 2009). But only 2.5% of Earth's water is potable, with the rest being salty (Oki & Kanae, 2006). The amount of freshwater that is accessible as surface water (rivers, lakes, etc.) is extremely low. That's why we can't do without surface water, and it's essential to our survival (Bhat et al., 2017). By 2025, half of the global population is expected to live in areas with inadequate access to clean water (WHO, 2014).
Prior to 2015, only 20% of the world's wastewater was treated. According to the UN, 70% of industrial wastewater is dumped untreated in underdeveloped countries. Wastewater treatment and safe water supply in both industrialized and developing nations are falling behind stricter rules and rising demand for clean water (Narayan, 2010). A material's smallest dimension must be less than 100 nm to be considered a nanomaterial. These materials are typically distinguished from their more substantial equivalents by distinct physical or chemical characteristics. Due to their larger surface area, nanoparticles contain more active sites per unit mass than any other particle size. Furthermore, the surface free energy of nanoparticles is higher, resulting in better surface reactivity (Yadav et al., 2017). The problem is exacerbated by industrialization and the disposal of electronic waste. Water bodies' pollution includes lead, mercury, arsenic, cobalt, nickel, and other toxic elements (Khan & Malik, 2019). Additionally, new pollutants can harm the ecological system and human health, even at low concentrations. Low quantities of emerging pollutants may also harm the environment and people's health.
Most developing contaminants in wastewater bodies are chemicals that are not biodegradable, accumulate in food webs, and are harmful to humans, animals, plants, and ecosystems (Kumar et al., 2015; Larramendy et al., 2015). One of the world's major problems is the unregulated release of wastewater into waterways such as streams and rivers. As a result, the water quality in these bodies of water is severely compromised (Naidoo & Olaniran, 2013). The largest cities in India generate 38,354 MLD of manure and wastewater daily, yet the country only has 11,786 MLD worth of sewage treatment capacity. Also, 13,468 MLD of industrial wastewater is produced in India, but only 8080.8 MLD of that volume can be handled (Kaur et al., 2012.). Pakistan (2301 MLD), Nepal (133 MLD), Sri Lanka (163 MLD), and Bangladesh (150 MLD) are some of the other Asian nations that produce a lot of wastewater every year (Batool & Shahzad, 2021). Methods such as coagulation-flocculation, electrochemical treatment, adsorption, membrane filtration, etc., have been used for decades to treat contaminated water (Batool & Shahzad, 2021; Shah et al., 2020). Modern techniques for treating contaminated water include ultrafiltration, adsorption, chemical precipitation, biological oxidation, coagulation, etc. Heavy metals, some of which are harmful, are frequently found in industrial effluent (F. Liu et al., 2020). As a result, efficient and cost-effective energy-saving technology is needed for wastewater treatment.