In the present study, treatment of amoxicillin (AMX) antibiotic from the surface water using carboxymethyl tragacanth gum-grafted-polyaniline doped to Fe2O3 (CMTG-g-PANI/Fe2O3) bionanocomposites (BNCs) was examined with adsorption process from pharmaceutical industry wastewater (PI ww) plant, İzmir, Turkey. Different pH values (4.0, 5.0, 7.0 and 9.0), increasing adsorption times (5 min, 10 min, 20 min and 40 min), increasing AMX concentrations (100 mg/l, 200 mg/l, 300 mg/l, 400 mg/l and 500 mg/l), increasing CMTG-g-PANI/Fe2O3 BNCs concentrations (5 mg/l, 15 mg/l, 30 mg/l and 45 mg/l), respectively, was operated during adsorption process in the efficient removals of AMX micropollutants in PI ww. The characteristics of the synthesized NPs were assessed using XRD, EDX, FESEM, FTIR, TEM and VSM analyses, respectively. Also, thermal gravimetric analysis (TGA) was operated with Brunauer–Emmet–Teller (BET) measurements by a multi-point method, and the pore parameters were calculated via the Dubinin–Astakhov (DA) method. ANOVA statistical analysis was used for all experimental samples. The maximum 99.36% AMX removal was obtained during adsorption process in PI ww at pH=7.0 and at 25oC. The maximum 99.07% AMX removal was observed during adsorption process in PI ww after 20 min, at pH=7.0 and at 25oC, respectively. The maximum 99.23% AMX removal was found with adsroption process in PI ww, at 100 mg/l AMX, after 20 min, at pH=7.0 and at 25oC, respectively. The maximum 99.20% AMX removal was measured to 5 mg/l CMTG-g-PANI/Fe2O3 BNCs with adsorption process in PI ww, at 100 mg/l AMX after 20 min, at pH=7.0 and at 25oC, respectively. The maximum 99% and 99% AMX recovery efficiencies were measured in PI ww during adsorption process, after 1. recycle time and 2. recycle time, respectively, at 100 mg/l AMX after 20 min, at pH=7.0 and at 25oC, respectively. A granular structure with good thermal stability (34wt% char yield), 8.1143 m2/g specific surface area and 23 emu/g magnetization saturation were measured for CMTG-g-PANI/Fe2O3 BNCs. 983.11 mg/g maximum adsorption capacity was observed at pH=7.0, at 20 min adsorption mixing time, at 5 mg/l CMTG-g-PANI/Fe2O3 BNCs, at 500 mg/l initial AMX concentration, respectively. The Freundlich isotherm model and the pseudo-second-order kinetic models are much more suitable with the experimental data for AMX removal in PI ww during adsorption process with CMTG-g-PANI/Fe2O3 BNCs. The adsorption/desorption process showed that CMTG-g-PANI/Fe2O3 BNCs could continue to remove AMX after three sequential adsorption/desorption cycles without significantly losing adsorption capacity. Finally, the combination of a simple, easy operation preparation process, excellent performance and cost effective, makes this CMTG-g-PANI/Fe2O3 BNCs bioadsorbent a promising option during adsorption process in PI ww treatment.

Emerging contaminants (ECs), sometimes known as contaminants of emerging concern (CECs) can refer to a wide variety of artificial or naturally occurring chemicals or materials that are harmful to human health after long-term disclosure. ECs can be classified into several classes, including agricultural contaminants (pesticides and fertilizers), medicines and antidote drugs, industrial and consumer waste products, and personal care and household cleaning products [1,2]. Antibiotics are one of the ECs that have raised concerns in the previous two decades because they have been routinely and widely used in human and animal health care, resulting in widespread antibiotic residues discharged in surface, groundwater, and wastewater.

Antibiotics, which are widely utilized in medicine, poultry farming and food processing [3,4], have attracted considerable attention due to their abuse and their harmful effects on human health and the ecological environment [5,6]. The misuse of antibiotics induces Deoxyribonucleic Acid (DNA) contamination and accelerates the generation of drug-resistant bacteria and super-bacteria [7-9]; thus, some diseases are more difficult to cure [10]. A number of studies have revealed that the level of antibiotics in the soil, air and surface water and even in potable water, is excessive in many areas [11-13], which will ultimately accumulate in the human body via drinking water and then damage the body’s nervous system, kidneys and blood system. Therefore, it is necessary to develop an efficient method to remove antibiotics present in PI ww.

The uncontrolled, ever-growing accumulation of antibiotics and their residues in the environment is an acute modern problem. Their presence in water and soil is a potential hazard to the environment, humans, and other living beings. Many therapeutic agents are not completely metabolized, which leads to the penetration of active drug molecules into the biological environment, the emergence of new contamination sources, the wide spread of bacteria and microorganisms with multidrug resistance [14-16]. Modern pharmaceutical wastewater facilities do not allow efficient removal of antibiotic residues from the environment [17,18], which leads to their accumulation in ecological systems [19,20]. Global studies of river pollution with antibiotics have shown that 65% of surveyed rivers in 72 countries on 6 continents are contaminated with antibiotics [21]. According to the World Health Organization (WHO), surface and groundwater, as well as partially treated water, containing antibiotics residue and other pharmaceuticals, typically at < 100>

More than 90% of medications taken orally do not decompose, thus they become active compounds. Since antibiotics are highly soluble in water, conventional treatment procedures cannot eliminate them, which poses a significant obstacle to their removal [27]. The removal of antibiotics and their residues from water and wastewater prior to their final release into the environment is of particular concern [28]. Modern purification methods can be roughly divided into the following three categories depending on the purification mechanism: biological treatment [29,30], chemical degradation [28,31], and physical removal. Each of these methods has its own advantages and disadvantages. For example, biological purification can remove most antibiotic residues, but the introduction of active organisms into the aquatic environment can upset the ecological balance. Various chemical approaches (ozonation, chlorination, and Fenton oxidation) cannot provide complete purification and, in some cases, lead to the death of beneficial microorganisms due to low selectivity.  

The most common techniques for removing antibiotics include electrochemical degradation [32], Fenton oxidation process [33], UV radiation [34,35], ozonation [36], membrane filtration [37,38], photolysis [39], biological degradation [40], and adsorption [41]. The most appealing technology, nevertheless, is the adsorption process, which has a flexible and straightforward design, is simple to use, is inexpensive, and is highly effective [42, 43]. The adsorbent used in industrial applications should be able to quickly absorb the target material and be ecologically benign [44].

Amoxicillin (AMX) is one of the most widely employed commercial penicillins and based on a β-lactam antibiotic categorized as penicillin [45], due to its high bacterial resistance and large spectrum against a wide range of microorganisms [46, 47]. Systemic, bacterial, and gastrointestinal illnesses are treated with AMX in both human and veterinary medicine. It is widely recognized that AMX is utilized in modern medicine, and its ecotoxicity contributes to the danger of medical wastewater. It can be found in medical wastewater coming from pharmaceutical plants and hospitals, which causes skin disorders and microbial resistance among pathogen organisms. Due to the difficulty of breaking down this antibiotic, the residue is eliminated in the urine and feces. Consuming too much AMX creates resistant bacteria because it accumulates in the body and feeds the organisms [48]. It has been reported that about 30−90% of AMX are discharged into the environment through human and animal excrements [49], and the presence of AMX in the ng/l to mg/l concentration ranges in surface water, domestic and industrial wastewater. Since resistant bacteria can cause diseases that are not treatable with traditional antibiotics, AMX waste must be treated before its disposal [50]. It is essential to use an effective technique to remove AMX before it is released into the aquatic environment.

Several methods have been reported for removal of AMX in different matrices. These include electrode gradation [51]. advanced oxidation [52]. photocatalytic degradation [53]. and adsorption [49, 54-56], among others. Adsorption process has been found to more effective for removal of AMX because it restricts the transportation of pollutants into water systems [57]. Also, adsorption process is attractive because it uses different adsorbents. These include activated carbon (AC) [49, 54], carbon nanotubes [47,57,58], magnetic Fe3O4/activated carbon nanocomposite (NCs) [59, 60], magnetic graphene oxide [55, 56], and porous polymers [61]. In order to effectively remove AMX from water, a range of micro/nanostructures were deemed acceptable adsorbents, either as single phases or composites. The use of various adsorbents for AMX removal from aqueous solutions were reported at literature. A metal–organic framework (MIL-53(Al)) was prepared with a hydrothermal technique and used as an adsorbent for the removal of AMX from surface water [62]. 758.5 mg/g MIL-53 adsorption capacity in experimental conditions due to its high surface area. An adsorbent based on NH4Cl-induced AC was employed for the removal of AMX from water. 99% AMX removal was measured, owing to the high specific surface area (1029 m2/g) of NH4Cl-induced AC [63]. 97.9% AMX removal from surface water was reported by an adsorbent based on AC produced from pomegranate peel/iron nanoparticles, at pH=5.0 after 30 min contact time [64]. A green magnetic adsorbent based on functional CoFe2O4-modified biochar was used for AMX removal from surface water. The maximum 99.99 mg/g adsorption capacity is obtained at pH=7.0 and at 25oC [65].

Tragacanth gum (TG), as a colorless and odorless natural polymer, is a highly complex heterogeneous anionic polysaccharide that forms from the stems and branches of Astragalus gummier and other Asian Astragalus species [66]. Within a few weeks, the exudate can be recovered after it has solidified into flakes or coils of ribbon [67]. TG is a substance that is found in Turkey, Iran, India and Afghanistan. Neutral and anionic sugars, such as D-galacturonic acid, D-galactose, D-xylose, L-arabinose, L-fucose, and d-glucose are found in TG [66, 68]. TG natural polymer is utilized in a broad range of areas, including the food, pharmaceutical, cosmetic [69], textile, printing, and leather industries [66, 70-76]. It is possible because of its amazing qualities, including (i) superior acid, heat, and enzyme resistance; (ii) longer shelf life and microbial resistance; (iii) non-toxicity, non-allergenicity, non-carcinogenicity, non-mutagenicity, and non-teratogenicity; (iv) biocompatibility; and (v) biodegradability [66, 70-76]. In addition to, TG is inexpensive, readily accessible, and has great solubility, strong thermal stability, and a long shelf life [77]. In TG, hydroxyl- and carboxylic-acid-reactive functional groups can be used for chelation in removing pollutants from surface water. In order to increase the adsorption capacity of natural polymers, copolymerization with functional monomers and inorganic fillers are added. The nanoparticles (NPs) synthesis mediated by gum TC qualifies various principles of green chemistry such as (i) natural availability/renewability, (ii) non-toxicity/inherently safer, (ii) aqueous solubility, (iv) dual functional role of reducer and stabilizer, and (iv) biodegradability [71, 74-78].

Iron (III) oxide (Fe2O3, hematite or red iron oxide) is an inorganic compound. It is occurs naturally in rocks of all ages. It appears as a red-brown solid. It is odourless and pH=7.0 [79]. Fe2O3 NPs is used as a feedstock in the production of iron, as a pigment (Pigment Brown 6, Pigment Red 101), in cosmetics, in dental composites, an important ingredient in calamine lotion, to apply the final polish on metallic jewellery, in magnetic disk and magnetic tapes, and in pharmaceuticals industry [79]. If Fe2O3 NPs is inhaled, iron causes irritation of the gastrointestinal tract and lungs [79].

In this study, treatment of AMX antibiotic from the surface water using CMTG-g-PANI/Fe2O3 BNCs was examined with adsorption process from PI ww plant, İzmir, Turkey. Different pH values (4.0, 5.0, 7.0 and 9.0), increasing adsorption times (5 min, 10 min, 20 min and 40 min), increasing AMX concentrations (100 mg/l, 200 mg/l, 300 mg/l, 400 mg/l and 500 mg/l), increasing CMTG-g-PANI/Fe2O3 BNCs concentrations (5 mg/l, 15 mg/l, 30 mg/l and 45 mg/l), respectively, was operated during adsorption process in the efficient removals of AMX micropollutants in PI ww. Also, increasing recyle times (Between 1 and 20 cycle) was examined for the AMX removal The characteristics of the synthesized NPs were assessed using XRD, EDX, FESEM, FTIR, TEM and VSM analyses, respectively. In addition to, TGA analysis was operated with BET measurements by a multi-point method, and the pore parameters were calculated via the Dubinin–Astakhov (DA) method. ANOVA statistical analysis was used for all experimental samples.

2.1. Characterization of Pharmaceutical Industry Wastewater

Characterization of the biological aerobic activated sludge proses from a PI ww plant, İzmir, Turkey was performed. The results are given as the mean value of triplicate samplings (Table 1). 

Table 1: Characterization of PI ww

2.2Experimental Chemicals

Na2HPO4, NaCl, KH2PO4 and NH4Cl purchased from Merck (Merck, Germany). The KOH tablets used as electrolyte was purchased from Merck (Merck, Germany). TG with high-quality in translucent flakes was purchased from Sigma-Aldrich (Germany). The specific surface area of the samples was studied by the Brunauer–Emmett–Teller (BET) technique according to Belsorp mini II, Microtrac BEL, Osaka, Japan. The thermal behavior of samples was investigated by thermogravimetric analysis (TGA) with L81A1750 Linseis (Selb, Germany).

2.3. The Preparation of Carboxymethyl Tragacanth Gum (CMTG) 

The CMTG was synthesized according to Abdollahi et al. [80], with slight modifications. 1 g disolved powdered TG was filled in a mixture of water/ethanol (85 ml/15 ml). Then, 1.2 g NaOH in 10 ml deionized water was added to the reaction mixture. This solution was kept at 50oC for 30 min under a magnetic stirrer (Heidolph, Schwabach, Germany). After, 1.3 g monochloroacetic acid (C2H3ClO2) in 10 ml deionized water was added to the reaction solution, and the final solution was stirred for 4 h at 50oC. After then, cooling, the solution was poured into a double volume of ethanol or methanol. The resultant CMTG sediment was separated using filter paper and dried at 40oC.

1. The Synthesis of Fe2O3 NPs

The co-precipitation method was employed for the Fe2O3 NPs synthesis [81]. 0.1 M NaOH solution was added to 100 ml deionized water, and the reaction mixture was stirred magnetically for 15 min under an inert atmosphere [It is an environment where powder bed fusion can take place without the risk of contamination from reactive gases in the air, such as O2(g) and CO2(g)]. After, a solution of Fe(III) and Fe(II) salts was dropped into the previous solution, and the final solution was kept under vigorous stirring at 25oC for 70 min. The resulting brown precipitate was separated and washed several times with deionized water and ethanol. After that, the precipitate was dried and the obtained powder was calcined at 300oC for 2 h to gain the Fe2O3 NPs.

1. The Preparation of CMTG-g-PANI/Fe2O3 BNCs

In a 250 ml round-bottom flask, 0.62 g CMTG was dissolved in 50 ml deionized water. Then, 1.5 ml HCl was added to the solution, and the flask was kept under N2(g) at 0–5°C. Subsequently, 10 wt

3.1. The Characteristics of CMTG-g-PANI/Fe2O3 BNCs

3.1.1. The Results of XRD Analysis 

The results of XRD analysis was observed to CMTG-g-PANI/Fe2O3 BNCs in the removal of AMX in PI ww with adsorption process (Figure 1). The characterization peaks were found at 2θ values of 22.18o and corresponding to the (110), respectively (Figure 1a). The characterization peaks were measured at 2θ values of 33.41o, 36.10o, 50.28o, 55.71o, 62.38o and 64.60o, respectively, and corresponding to the (003), (112), (200), (120), (222) and (221), respectively (Figure 1b). The characterization peaks were observedd at 2θ values of 22.19o, 24.03o and 33.11o, respectively, and corresponding to the (101), (114) and (120), respectively (Figure 1c). The characterization peaks were measured at 2θ values of 34.12o, 36.81o, 49.76o and 54.63o, respectively, and corresponding to the (112), (042), (211) and (132), respectively (Figure 1d).

Figure 1: XRD spectra of (a) CMTG NPs, (b) Fe2O3 NPs, (c) CMTG-g-PANI NCs and (d) CMTG-g-PANI/Fe2O3 BNCs in the removal of AMX in PI ww with adsorption process.

3.1.2. The Results of EDX Analysis

The EDX analysis of CMTG-g-PANI/Fe2O3 BNCs was also performed to investigate in the removal of AMX in PI ww with adsorption process (Figure 2). The elemental percentages of CMTG-g-PANI/Fe2O3 BNCs were obtained at 41.50w%C, 27.80w%O, 12.66w%N, 7.56w

The treatment of AMX antibiotic from the surface water using CMTG-g-PANI/Fe2O3 BNCs as a bioadsorbent was examined with adsorption process from PI ww plant, İzmir, Turkey. The maximum 99.36% AMX removal efficiency was obtained during adsorption process in PI ww at pH=7.0 and at 25oC. The maximum 99.07% AMX removal efficiency was observed during adsorption process in PI ww after 20 min adsorption time, at pH=7.0 and at 25oC, respectively. The maximum 99.23% AMX removals efficieny was found with adsroption process in PI ww, at 100 mg/l AMX, after 20 min adsorption time, at pH=7.0 and at 25oC, respectively. The maximum 99.20% AMX removal efficieny was measured to 5 mg/l CMTG-g-PANI/Fe2O3 BNCs with adsorption process in PI ww, at 100 mg/l AMX after 20 min adsorption time, at pH=7.0 and at 25oC, respectively. The maximum 99% and 99% AMX recovery efficiencies were measured in PI ww during adsorption process, after 1. recycle time and 2. recycle time, respectively, at 100 mg/l AMX after 20 min adsorption time, at pH=7.0 and at 25oC, respectively.

A granular structure with good thermal stability (34wt% char yield), 8.1143 m2/g specific surface area and 23 emu/g magnetization saturation were measured for CMTG-g-PANI/Fe2O3 BNCs. 983.11 mg/g maximum adsorption capacity was observed at pH=7.0, at 20 min adsorption mixing time, at 5 mg/l CMTG-g-PANI/Fe2O3 BNCs, at 500 mg/l initial AMX concentration, respectively. The Freundlich isotherm model and the pseudo-second-order kinetic models are much more suitable with the experimental data for AMX removal in PI ww during adsorption process with CMTG-g-PANI/Fe2O3 BNCs. The adsorption/desorption process showed that CMTG-g-PANI/Fe2O3 BNCs could continue to remove AMX after three sequential adsorption/desorption cycles without significantly losing adsorption capacity. The intermolecular interactions such as hydrogen bonding, electrostatic and π–π interactions between AMX and CMTG-g-PANI/Fe2O3 BNCs were suggested for the adsorption mechanism of AMX by CMTG-g-PANI/Fe2O3 BNCs in PI ww during adsorption process. 

The AMX removal with adsorption process with CMTG-g-PANI/Fe2O3 BNCs applied to other waste metal ions to prepare the biogenic metals, facilitate their recovery and reuse in degrading micropollutants in PI ww. Finally, the combination of a simple, easy operation preparation process, excellent performance and cost effective, makes this CMTG-g-PANI/Fe2O3 BNCs bioadsorbent a promising option during adsorption process in PI ww treatment.

This research study was undertaken in the Environmental Microbiology Laboratories at Dokuz Eylül University Engineering Faculty Environmental Engineering Department, Izmir, Turkey. The authors would like to thank this body for providing financial support.