Open Chem., 2018; 16: 949–955 Research Article Open Access Lvshan Zhou, Xiaogang Guo*, Chuan Lai*, Wei Wang Electro-photocatalytic degradation of amoxicillin using calcium titanate https:// doi.org/10.1515/chem-2018-0108 Electro-photocatalytic; Amoxicillin; Calcium received January 5, 2018; accepted July 8, 2018. Keywords: titanate; Kinetics; Degradation. Abstract: The electro-photocatalytic degradation of amoxicillin in aqueous solution was investigated using single factor test by the potassium permanganate method 1Introduction for measuring the values of chemical oxygen demand (CODMn). Batch experiments were carried out successfully In recent years, more and more experts have called for under different conditions, including initial amoxicillin the banning of the abuse of antibiotics due to seriously concentration, calcium titanate dosage, pH, UV irradiation endangering the environment and endangers human time, electrolyte and temperature. The experimental health. Various antibiotics are detected in the medical results show that there is a great difference between wastewater, surface water, groundwater worldwide, and electro-photocatalytic and photocatalitic degradation. even in the drinking water [1~3]. Therefore, much attention The maximum electro-photocatalytic degradation has been focused on the research of antibiotic compounds efficiency can increase to 79% under the experimental in the environment, and methods for their treatment [4]. conditions of 200 mL amoxicillin solution (100 mg L-1) Amoxicillin is a commonly used β-lactam antibiotic, with 0.5 g calcium titanate by pH=3 for 120 min irradiation which is widely applied in medical, animal husbandry, and 0.058 g sodium chloride as electrolyte at 318.5K. In aquaculture and other fields [5]. It is reported that addition, the reaction rate constant of 0.00848~0.01349 amoxicillin has been analyzed in different water samples min-1, activation energy of 9.8934 kJ mol-1 and the pre- from different regions and countries [6]. Since the exponential factor of 0.5728 were obtained based on 1940s, many methods such as adsorption, precipitation, kinetics studies, indicating that the electro-photocatalytic oxidation and microbial degradation were explored reaction approximately followed the first-order kinetics for antibiotic waste water treatment by researchers model. [7]. At present, light or electricity-assisted degradation methods are commonly used based on the advanced oxidation reaction. Rosenfeldt [8] proposed that providing ultraviolet light during antibiotics degradation using hydrogen peroxide can effectively increase the *Corresponding authors: Xiaogang Guo, College of Chemistry degradation ratio of antibiotics. Comparing with Fenton- and Chemical Engineering, Yangtze Normal University, Chongqing like and Fenton methods on the removal of penicillin in 408100, China, E-mail: [email protected]; Chuan Lai, School of Chemistry and Chemical Engineering, Eastern Sichuan Sub-center dark and light conditions, advanced oxidation turned out of National Engineering Research Center for Municipal Wastewater to be an effective method for reducing the chemical oxygen Treatment and Reuse, Sichuan University of Arts and science, demand in aqueous solution. When light is supplemented, Dazhou 635000, China; Key Laboratory of Green Catalysis of Higher extending processing time can continue to improve Education Institutes of Sichuan, Sichuan University of Science and the degradation effect [9,10]. In 2016, a research was Engineering, Zigong, 643000, China; Wanyuan Market Supervision Bureau, Dazhou 635000, PR China, E-mail: [email protected] undertaken applying power with various current densities Lvshan Zhou: School of Chemistry and Chemical Engineering, to the levofloxacin aqueous solution, and the content Eastern Sichuan Sub-center of National Engineering Research Center of levofloxacin effectively decreased by electro-Fenton for Municipal Wastewater Treatment and Reuse, Sichuan University method [11]. Light and electricity have played extremely of Arts and science, Dazhou 635000, China; Key Laboratory of important roles in the degradation of antibiotics, and Green Catalysis of Higher Education Institutes of Sichuan, Sichuan University of Science and Engineering, Zigong, 643000, China have an extremely important role confirmed in lots of Wei Wang: Wanyuan Market Supervision Bureau, Dazhou 635000, reports. Therefore, photocatalysis is an effective method PR China used for degradation of antibiotics, until now, which Open Access. © 2018 Lvshan Zhou et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution- NonCommercial-NoDerivatives 4.0 License. 950 Lvshan Zhou et al. is primarily concerned with designing novel catalysts . The 500 mL beaker with a magnetic stirring bar and The titanium dioxide (TiO2), zinc oxide (ZnO), cadmium under an illumination of 15 W UV lamp (Sitong, China) sulfide (CdS) and ferric oxide (Fe2O3) were commonly is taken as the photocatalytic reactor. In some cases, it is used as catalyst in amoxicillin photocatalytic degradation necessary to provide power supply to energize in aqueous process [12]. Considering the limited performance for solution. For each degradation experiment, various pure catalysts, researchers modified the photocatalyst by amounts of calcium titanate were added into 200 mL various ways, such as loading metal, inorganic salts and amoxicillin solution. PH was adjusted by H2SO4 and NaOH even organic matter [13-15]. In addition to modifying the solutions and monitored by INESA PHS-3E pH meter developed catalysts, researchers have also explored other (China). The suspension was agitated by magnetic stirring new catalysts, especially calcium titanate as a promising for 30min under dark conditions, and then irradiated catalyst. by UV lamp. Amoxicillin concentrations, calcium Calcium titanate with octahedral groups as basic titanate dosage, pH, UV irradiation time, electrolyte and structural unit is a typical perovskite type photocatalyst. temperature were optimized according to the values The band gap of calcium titanate is 3.5eV higher than that proposed in experimental design. After each experiment, of TiO2 (3.2eV), showing the potential excellent catalytic the test solution was withdrawn and separated by a high performance in theory [16]. In recent years, a great number speed centrifuge (Feige TGL-16GB, China) at 8000 r/min of researchers in various countries have begun to use pure for 10 min. or modified calcium titanate involving loaded metal and In the course of experiment, the values of chemical metal oxide for improving photodegradation of water, oxygen demand (CODMn) for various test solutions were and several decent results are obtained [17-20]. However, measured according to potassium permanganate method how to realize the antibiotics degradation is still difficult [21]. The working curve of amoxicillin standard solutions c R2 by using calcium titanate, and the related reports are is [CODMn]=668.91 +5.1268, =0.9992, where [CODMn] is few. In this work, the amoxicillin degradation bycalcium the concentration of (mg L-1) in test solution, and c (mg L-1) titanate in aqueous solution was studied by single factor is amoxicillin standard solution concentration from 0 mg experiment under UV irradiation with various current L-1 to 300mg L-1. densities. Meanwhile, an extension study of application The degradation efficiency of each test was calculated based on calcium titanate would be analyzed in this work, based on the following expression (Eq. (1)): and more useful information could be provided for the kinetic study of amoxicillin degradation. [CODMn ]initial [CODMn ] final K˄%˅ u100 (1) [CODMn ]initial 2Experimental [CODMn]initial and [CODMn]final are the chemical oxygen demand values of the initial and final solutions Amoxicillin and calcium titanate (minimum 99.5%, 2μm) respectively. were purchased from Aladdin. And others were purchased The degradation kinetics can usually be described by the from Chengdu Kelon Chemical Co., Ltd. Distilled water zero-order, first-order and second-order kinetics models. was used for the preparation of all test solutions. The reaction rate between amoxicillin concentration An aqueous stock solution with 300 mg L-1 amoxicillin and time can be expressed by Eq. (2), Eq. (3) and Eq. (4), was prepared. From this, calibration standards with respectively. concentrations of 1, 10, 20, 50, 100 and 200 mg L-1 were prepared in distilled water before being filtered through dc - r k (2) 0.45mm nylon filter membranes from Jingteng (China). 0 dt 0 In order to eliminate the effect of calcium titanate self- adsorption, the adsorption experiment was carried out dc - r k c (3) under dark conditions. In the adsorption process, the 1 dt 1 effect of initial amoxicillin concentrations of 100 and 300 mg L-1 were investigated by batch experiments for a dc - r k c2 (4) specific period of the contact time (0~300 min) at room 2 dt 2 temperature. c c t c c t t Integrating between = 0 at = 0 and = at = , Eq. (2), (3) and (4) can be displayed as follows: Electro-photocatalytic degradation of amoxicillin using calcium titanate 951 2.0 c c0 k0t (5) k t 1.5 1 ) c c0 e (6) -1 1 1 1.0 k2t (7) c c0 removal (mg L Mn 100mg/L Amoxicillin 0.5 c c COD 0 and are the concentrations of amoxicillin at initial 300mg/L Amoxicillin -1 k k k and final testing, respectively (mg L ), 0, 1, 2 are rate constants of the zero-order, first-order and second-order 0.0 reaction respectively, t is irradiation time. 0 50 100 150 200 250 300 E Assuming that the activation energy ( a) of Adsorption time (min) amoxicillin in the process of degradation is independent of temperature (T), the Arrhenius equation (Eq. (8) and Figure 1: The effect of adsorption on chemical oxygen demand E -1 -1 (9)) can be used to calculate the activation energy ( a) and removal for 200mL 100 mg L and 300 mg L amoxicillin solution the pre-exponential factor (A). with 0.5 g calcium titanate at room temperature in various adsorption time. k Ae(Ea RT ) (8) or 30 Ea 1 ln k ln A (9) 25 R T k is rate constants. 20 Ethical approval: The conducted research is not 100mg/L Amoxicillin 300mg/L Amoxicillin related to either human or animal use.