New Polymeric Adsorbents Functionalized with Aminobenzoic Groups for the Removal of Residual Antibiotics  
[PERSON]  
1 Industrial Chemistry and Environmental Engineering Faculty, Politehnica University Timisoara, 6 Vasile Parvan Blv, 300223 Timisoara, Romania; radu.ardelean@uptro  
[PERSON]  
2 Corional Dragulescu  
effluents, such as amoxicillin, sulfamethoxazole, and tetracycline, with concentration values in the range of ng/L to \(\upmu\)g/L [5,6]. Sulfamethoxazole (SMX) is a representative antibiotic of the sulfonamide family, which is a group of veterinary pharmaceuticals. It is mainly given to patients who suffer from infectious diseases caused by bacteria [7]. Tetracycline (TC) is a widely used antibiotic because it has a broad spectrum of action against bacteria (both Gram-positive and Gram-negative), mycoplasmas, fungi (chlamydia), rickettsiae, and vermin, low toxicity and cost, and good oral absorption [8, 9, 10].  
Several treatment methods have been developed to remove antibiotics from aqueous solutions, such as adsorption methods, biological treatment, coagulation-precipitation, electrochemical processes, ion exchange, membrane processes, and photocatalysis [9, 10, 11]. Among these methods, adsorption technology is still the most studied option for reducing antibiotics [12, 13, 14, 15], since it is cost-effective and simple and highly reproducible, and a wide range of adsorbents is available [16, 17, 18].  
Over time, researchers have effectively used different types of adsorbent material, such as carbon-based materials [19], polymers and resins [20, 21, 22], metal-organic frameworks [23], clays and minerals [24], zeolites [25], etc., to reduce the concentration of residual antibiotics in polluted waters.  
The functionalization of polymeric supports with active pendant groups has provided structures with improved properties that can be used in a wide range of applications. The applications of these materials include their use as catalysts [26, 27], antibacterial agents [28, 29], and adsorbents for a wide range of pollutants [30, 31]. Various polymers and resins have been successfully explored for the removal of antibiotics from aqueous environments using adsorption techniques [21, 32].  
In our previous work, we have presented the functionalization of styrene-divinylbenzene copolymers with N,N-dialkyl 2-hydroxyethyl ammonium groups [33, 34], and with aminobenzic acid groups [35], by polymer-analogous reactions.  
In this article, we present, for the first time, the adsorption performances of macroporous styrene-divinylbenzene copolymers bearing p-aminobenzoic acid groups against antibiotics. The polymeric adsorbents from the present study are different from those used in our previous work [35].  
The purpose of the present study was to obtain new polymeric adsorbents, starting from macroporous chloromethylated styrene-divinylbenzene copolymers, with different degrees of crosslinking (6.7% (PAB1), 10% (PAB2), and 15% (PAB3) divinylbenzene). These functionalized solid copolymer adsorbents are easily recovered from the rection medium by simple filtration, with no contamination of the environment. New polymeric adsorbents were characterized by a wide range of analytical methods: FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis. The polymeric adsorbents functionalized with p-aminobenzoic acid active groups (PAB1, PAB2 and PAB3) were tested by extensive kinetic and thermodynamic studies in the adsorption of antibiotics (tetracycline, sulfamethoxazole, and amoxicillin) from aqueous solutions. The best adsorption capacity was observed for tetracycline, while the adsorption of amoxicillin did not show positive results.