**4. Binary and ternary antibiotics mixture**

The TiO2 is steady, inexpensive photocatalyst, and widely applied for removal and decompose organic pollutants. However, the poor selectivity of the TiO2 is not conducive to remove high toxic contaminants from mixed solution, mostly in the presence of other pollutants [15, 16]. Some studies use tetracycline (TC) as a molecular template and the TiO2 fly ash cenospheres as a supporter, the synthesis of the molecularly imprinted photocatalyst (MIP). Such a material possesses the specific recognition ability toward tetracycline (TC) using surface-imprinting technology and the photo-induced method. The cenospheres hollow spherical structure has the diameter from 90 to 120 μm, and the degradation process of photocatalytic activity of MIP with 20 mgL−1 of TC under visible light radiation reached the photodegradation rate of 77%. Also, MIP showed the TC-selective recognition and promoted the photodegradation of TC in the ternary solutions containing TC, oxytetracycline (Oxy), and ciprofloxacin (CIP). The coefficients of selectivity of degradation from TC, Oxy, and CIP were 1.67 and 1.25, respectively. The photodegradation mechanism of TC analyzed by mass spectrum (MS) indicated the TC decomposition step by step, resulting in CO2 , H2 O, and other gases.

A large number of antibiotics and their residues lead to the environmental emergence as a threat to indigenous microbial populations. The tetracycline (TC) ranks second in the global production and use. In spite of its consumption, environmental TC residues are very low (μgL−1 or nanogram L−1), but they are resilient, and the TC residues may cause a series of ecological environmental and human health effects, such as promoting the resistant bacteria. The photocatalytic with solar energy is green technology and capable of decomposing the organic pollutant to a nontoxic compound.

The molecular imprinting is a versatile and straightforward method for the preparation of robust materials which can recognize the specific target in secondary and tertiary systems. Then, stability, the ease of development, and low cost make the molecularly imprinted particularly attractive. Two or more antibiotics always coexist in the polluted aquatic environment. Thus, it is essential and meaningful to discuss the multicomponent antibiotics solution.

Published works related a variety of antibiotics in polluted soil and water environment. Therefore, it is of great significance to explore the ecological risk of the combined exposure to various antibiotics. The mixture of different types of antibiotics may lead to varying joint effects on the bacteria's, synergistic, additive, and some antagonistic effects.

Some published works indicate that antibiotics mixtures present synergetic effects and others antagonistic effects. The presence of sulfonamides (SA), as potentiator effects (SAP), and tetracycline's (TC) was investigated for binary and tertiary mixture toxicity. The mixtures of SA-SAP and SA-SAP-TC presented a synergetic impact on bacteria tests, while SA-TC and SAP-TC showed antagonistic effects. The TC presence in ternary mixtures altered the toxic ratio of SA and SAP, which lead to the various joint effects of the ternary mixtures on different bacteria populations.
