## 1 Introduction  
Water has ever been the most significant life component for all creatures. With the notable rise in global warming and desertification, water quantity is becoming a worldwide concern [1; 2]. While the quantity of water and the share per capita are growing apprehensions, quality of water, which is relapsing progressively--mostly because of the anthropogenic deeds, the population development, the inadvertent expansion, the swift industrialization, and the inappropriate usage of natural water--is becoming a more serious concern [3]. Food, leather, and textile industries release large amounts of contaminated effluents. With the diverse chemical structure of the reagents used in these industries, various problems evolve. Dyes, an example of a major water contaminant, would color large volumes of water even if released as traces as low as 1 ppm. This effect causes not only an undesirable change in water quality in terms of aesthetic properties, but also it cannot be easily reversed or \"decolorized\". Reports show that, with the huge amount of dyes being produced annually (\(7\times 10^{5}\) tons/annum), an amount of 2% of dyes is directly released into the aquatic system together with an amount of 10% being lost during the tanning process, an issue that signifies the magnitude of the problem [4; 5; 6]. Released dyes affect not only aquatic beings but also human health. Their impacts include carcinogenicity, mutagenicity, poisoning, disturbance of the metabolism in aquatic bodies, etc. [7; 8]. Titan yellow (TY, Figure 1) is an organic triazene azo dye commonly used in tanning nylon and wool as well as a stain in microscopical examinations. The safety data sheet of TY shows that it is hazardous in case of ingestion with a less hazardous influence on eyes and skin [9; 10]. Removal of dyes from wastewater has been done by employing several approaches, e.g., adsorption, bleaching, filtration, biodegradation, and coagulation [11]. These methods possess both pros and cons in terms of cost, availability, efficacy, and surface area and have different influences on the environment. Adsorption, with the capability to totally remove dyes from wastewater, represents an ideal approach. Modeling of an efficient, green, low cost, safe, and reusable adsorbent (in other words, a standard adsorbent) has been the subject of various investigations. While different adsorbents have been used to remove dyes, the most commonly used adsorbents are the activated carbon (char) [12; 13]. As developing a standard adsorbent has been the task undertaken in many investigations, a novel category of adsorbents is becoming more prominent-_green_ adsorbents. This class of adsorbents offers a dual benefit by removing the contaminants as well as getting rid of the agricultural waste and by-products that would represent a burden on the environment if not properly discarded. Several agricultural waste products (e.g., peels of potatoes, pomergranates, bananas, rice husk, eggshells, crab shells, date pits) have been recycled into adsorbents and were used for the removal of heavy metals, dyes, drugs, etc. [13; 14; 15; 16; 17; 18]. Agricultural wastes and products rich in high molecular weight components such as cellulose, hemicelluloses, and lignin would deliver a good quantity of an adsorbent or biomass. Moreover, since these components are rich in functional groups, they are capable of forming different types of bonding (inter- or intramolecular), eventually creating a supramolecular structure capable of adsorbing the contaminants [19]. A literature survey shows that the waste biomasses can be used as they are (untreated or intact) [20; 21] following a treatment (activated carbon produced physically or chemically) [22; 23; 24] or after conversion into nanoparticles decorated with some functional groups for water remediation [25; 26]. _Aloe vera_ (AV) is a succulent plant that belongs to the family Asphodelaceae. The origin of AV is the Arabian Peninsula and regions with tropical/subtropical climates.