Functional finishes may impart special features in textiles like water repellency, flame resistance, fragrance, anticrease, and antimicrobial activities [1]. Cellulose is a natural fibre that has long satisfied global demand in the apparel and textile industries. Due to its exceptional handability, flexibility, biodegradability, eco-compatibility, and comfortability, cellulose is used worldwide in clothing and functional textiles [[2], [3], [4]]. The native hydrophilic properties of cellulose could be tuned to enhanced performance, versatility, and value addition [1,2]. For instance, cellulose may be made hydrophobic for water-repelling, self-cleaning, and oil/water-separating fabrics [5,6]. Usually, polyurethanes, waxes, silicones, metallic coatings, and especially fluorocarbons have been practiced for the said purposes. The fluorocarbon finishes, being persistent, toxic, and nonbiodegradable, stay in the environment for decades, thus causing several health and hygienic issues. Such compounds may enter the food chain and bring carcinogenic effects. Besides, fluorocarbons on wearable cellulose fabrics may reduce breathability and comfort [1,7].

Given these ecological and health concerns, natural sources are invited to produce renewable hydrophobic finishes, thus making the processes/products sustainable [8,9]. Several alternative sources have been approached in the above context, including beeswax, lanolin, biopolyesters, chitosan, plant oils, lignin, and so on [10]. Lignocellulosic biomass is a significant renewable source for producing fuels, energy, chemicals, polymers, and other products. It comprises two major semi-crystalline polysaccharides of cellulose (30–50 wt%) and hemicellulose (15–30 wt%) and amorphous aromatic macromolecules of lignin (10–30 wt%) [11]. Corn straw presumed as an agricultural waste, is abundant in corn-producing countries like Pakistan and is rich in cellulose, hemicellulose, and lignin components [12]. The lignin, being the main structural biomacromolecules of lignocellulosic biomass, is the most plentiful natural source of aromatics, having excellent potential for producing biofuels, chemical precursors, auxiliaries, and so forth [13]. Lignin is frequently found in plants, notably in seeds, whole grains, fruits, vegetables, and corn straw. It is the central part of the plant cell wall and, due to its nonpolar nature, helps protect the plant from extensive physiological water loss during transpiration [10].

Herein, corn straw has been expedited as a renewable source of lignin that is extractable through enzymatic or chemical hydrolysis followed by solvent extraction. Once isolated, the lignin may express hydrophobicity due to its polyphenolic and CH abundant structure [14]. The aromatic rings in the lignin comprise a series of conjugated double bonds, making them relatively nonpolar and resistant to interact with water molecules [15,16]. Likewise, the phenylpropanoid units of the lignin structure could further be modified with additional hydrophobic moieties, such as methyl or methoxy groups, to make them more hydrophobic [17]. Previously, sliver/titania incorporated bio-nanocomposites had been in situ fabricated and impregnated on cellulosic fabrics to express a WCA of 152.1° on a sliding surface at 8.7°, being functional up to 20 washes [18]. The corn straw lignin, however, may impart hydrophobicity in textiles in an eco-friendly and sustainable manner. If made superhydrophobic, textile surfaces could achieve self-cleanness. Such fabrics may be employed in marine, rain, and moist environments. They may be applicable in phase separation membranes and protective clothing for workers in wet or hazardous environments [12,15].

In this work, we aimed to extract lignin from corn straw feedstock through acid hydrolysis/solvent extraction and prepare an eco-friendly, hydrophobic, bio-based lignin finish using mild chemicals for successful application to cellulose fabric. The hydrophobic coatings made of lignin may provide an economical and sustainable alternative to conventional petroleum-based hydrophobic finishes. This is the first report on producing lignin-based bio-finish for superhydrophobic textiles with acceptable comfort and sensorial properties. We propose a bio-based alternative to synthetic hydrophobic finishes.