# Surfactant-Modified Construction Waste Bricks for the Removal of Diclofenac from Aqueous Solutions
## 1 Introduction  
Due to the significant enhancement in people's quality of life, there has been an increase in the release of pharmaceuticals and personal care products (PPCPs) into the environment on a global scale. In recent years, PPCPs have been found to accumulate in various aqueous solutions, including solutions from sewage treatment plants, industrial effluents, hospital effluents, reclaimed water irrigation, aquaculture, field runoff and even drinking water [1, 2, 3]. Despite the low concentration of PPCPs in the environment, they have been found to have a considerable impact on human health and natural ecosystems in both the short term and long term [4]. Diclofenac (DCF) is a common type of PPCP that belongs to the category of nonsteroidal anti-inflammatory drugs, which are frequently prescribed to alleviate pain and inflammation caused by various conditions, such as toothache, headache, osteoarthritis, rheumatoid arthritis, and other related disorders [5, 6]. The reports show that more than 1000 tons of DCF are produced and consumed annually, and most of it enters the environment through various pathways [2, 7]. Results have confirmed that DCF is not only associated with occasional hepatotoxicity and gastrointestinal effects but also causes renal disease in mammals at low concentrations [8, 9, 7]. Hence, there is an urgent need to explore and establish novel and efficient approaches to removing DCF from water-based solutions. Numerous technologies have been developed thus far to eliminate DCF from aqueous solutions, encompassing a wide range of methods such as biological, physical, and chemical processes [10]. However, reports show that biological processes, such as activatedsludge processes and constructed wetlands, have little effect on the removal of DCF [11]. Furthermore, studies also show that traditional physical and chemical methods, including coagulation, flocculation, and membrane filtration, are inefficient at eliminating DCF from the environment [12; 13]. Advanced oxidation processes (AOPs), such as UV radiation, photocatalysis, ozonation, and Fenton reactions, have been extensively studied as promising techniques to manage micropollutants in drinking water over the past few years [14; 15; 16]. However, in addition to economic factors, the production of secondary pollutants cannot be neglected as they may exhibit stronger toxicity [14]. Among the various methods available for water treatment applications, adsorption remains a highly effective approach due to its cost-effectiveness, energy efficiency, and ease of operation, particularly for the removal of micropollutants from aqueous solutions [17; 18; 19; 20]. Similar to other types of construction waste, the improper disposal, haphazard accumulation, and landfilling of waste bricks can have negative impacts on the atmosphere, soil, and water environment [21]. However, research has also shown that waste bricks have superior physical and chemical properties when compared to traditional materials such as clay and lime soil. Waste bricks have distinct properties such as specific surface areas, pore volumes, mechanical strengths, and active components, which render them appropriate for eliminating pollutants such as heavy metals and phosphorus from aqueous solutions [22]. However, the practical utilization of waste bricks for removing DCF from aqueous solutions is limited due to their inadequate adsorption sites, resulting in a relatively low removal efficiency. Table 1 displays the physicochemical characteristics of both CTAB and DCF. Surfactants have strong interactions with pollutants due to their hydrophilic and hydrophobic groups; hence, surfactants are often used as modified materials to enhance the removal efficiencies of different pollutants onto adsorbents [23; 24]. Reports have shown that the modification of cationic or anionic surfactants onto adsorbents could increase the adsorption capacity of polycyclic aromatic hydrocarbons, PPCPs, pesticides, and so on [25; 26; 27; 28; 29].