# Fabrication of Hydrophobic Coatings Using Sugarcane Bagsase Waste Ash as Silica Source
## 1 Introduction  
In recent years, solid waste management strategies have mainly focused on recycling rather than on waste disposal or storage. Industrial activities generate large quantities of various types of wastes, this causes significant economic and environmental problems, and management of industrial waste in an economic and ecological way has become a matter of great global interest. As a result, the use of waste materials can minimize the cost associated with landfilling [1; 2]. Sugarcane is one of the largest crops in the world. It is grown on approximately 25 million hectares, in over 90 countries, with a world harvest of 1.75 billion tons. World sugar demand is the main driving force behind sugarcane farming. Cane represents 80% of the sugar produced; most of the rest is made up of sugar beet. India is the second largest sugarcane producer in the world and the sugarcane production rate is increasing every year [3]. Sugarcane bagasse (SB) is a waste produced in sugar industries after the extraction of sugar can juice. There is a large volume of sugarcane bagasse produced all over the world, which implies the importance of approaches to the elimination of the material. Chemical analyses have shown that the ash obtained by burning the bagasse (sugarcane bagasse ash (SBA)) is rich in silica (SiO\({}_{2}\)) content. The quantity of silica content in SBA varies depending on the surrounding environment, nature of the soil, the harvest period, and the process involved. The concentration of silica increases with the increase in the amount of bagasse ash from the sugar cane [4; 5; 6]. Generally, the surface wettability can be characterized by the water contact angle (WCA). In the last two decades, special wettability with multifunctional surfaces has aroused great interest in fundamental research and industrial applications [7; 8; 9; 10; 11; 12; 13]. A surface with a drop of water below 90\({}^{\circ}\) and above 90\({}^{\circ}\) of WCA is commonly referred to as hydrophilic and hydrophobic surfaces, respectively. Precise superhydrophobic surfaces with a WCA above 150\({}^{\circ}\) have attracted significant attention due to their unique anti-humidifying and self-cleaning properties for practical applications. It is known that there are plants and numerous creatures in nature with incredible superhydrophobic surfaces. For example, the hydrophobic properties of lotus leaf with micro and nanoscopic surface architectures [14; 15; 16] have attracted much interest in industry and academia. The principle of water repellence of a superhydrophobic surface can be extended to practical applications, for example to develop coatings for car windows, buildings, tiles, and clothes [17; 18; 19; 20; 21; 22; 23; 24; 25]. Today, superhydrophobic materials have found spectacular advantages such as water repellence [26; 27], oil recovery [28; 29; 30], self-cleaning [31; 32], anti-corrosive [33; 34], anti-blocking [35; 36; 37], mechanical strength [38; 39], anti-icing [40; 41], and so on. Various techniques have been established to fabricate superhydrophobic surfaces, such as plasma or laser etching [42; 43], photolithography [14; 44], and electrochemical deposition [45]. However, these methods employ complicated processes, requiring specific equipment, rigorous preparation conditions, special substrates, and expensive/toxic fluoro silanes. In recent years, the fabrication of hydrophobic surfaces using waste materials and carbonaceous films has received significant attention [46; 47; 48; 49; 50; 51]. Silica could be extracted from rice husk ash [46; 47], oil palm fuel ash [12], and paper waste sludge ash [48; 49] to fabricate various hydrophobic substrates. Moreover, this would be highly beneficial for the waste disposal problems. The main objective of this present study was to investigate the application of SBA and non- fluoro silanes to fabricate hydrophobic surfaces. The hydrophobic surface was fabricated by the drop casting technique on various materials like floor tiles, brick, glass substrate, and cotton fabric.