In this study, the optimal conditions and effects of external factors on tetracycline adsorption by magnetic multi-walled carbon nanotubes (MMWCNTs) were established by a response surface methodology for the first time. Batch adsorption experiments showed that increasing the dosage and contact time effectively promoted the adsorption of tetracycline and maximum removal of 97.93–99.13% was achieved at pH 3–7. The pseudo-second-order model and Fourier-transform infrared spectroscopy spectra indicated that the mechanism of adsorption may be π–π electron interaction and cation–π electron bonding. Design Expert was utilized to develop a response surface methodology for the analysis and optimization of tetracycline adsorption by magnetic multi-walled carbon nanotubes. The Box–Behnken design (BBD) results showed that the optimization exhibited high significance and reliability. The main effect plots and Pareto chart indicated that pH exerted a significant individual effect on the regulation of adsorption, while 3D response surface plots and interaction effect plots exhibited a significant antagonistic interaction between pH and contact time. A maximum tetracycline removal of 99.16% was achieved under the optimal conditions of 12 mg adsorbent dosage at pH 5.43, with an adsorption time of 120 min. Mathematical and experimental results confirmed the accuracy of the established optimal conditions.

Microplastics (MPs) and antibiotics (ATs) have been detected in various aquatic environments and characterized as novel contaminants that have attracted worldwide attention. This review summarizes the characteristics of MPs and ATs, analyzes the sources of MPs and ATs in aquatic environments, reviews the concentration distribution of the two pollutants in China, and introduces the environmental effects of mixing MPs and ATs. Studies on single pollutants of MPs or ATs are well established, but the interactions between the two in aquatic environments are rarely mentioned. The physicochemical characteristics of MPs make them carriers of ATs, which greatly increase their risk of being potential hazards to the environment. Therefore, in this article, the interaction mechanisms between MPs and ATs are systematically sorted out, mainly including hydrophobic, electrostatic, intermolecular interactions, microporous filling, charge-assisted hydrogen bonding, cation-bonding, halogen bonding, and CH/π interactions. Also, factors affecting the interaction between ATs and MPs, such as the physicochemical properties of MPs and ATs and environmental factors, are also considered. Finally, this review identifies some new research topics and challenges for MPs and ATs, in order to gain deeper insight into their behavioral fate and toxic mechanisms.

The convenient and feasible pretreatment method of alkali treatment is very common in the degradation process of wheat straw. However, its utilization in the pretreatment of wheat straw as alternative adsorbents for aqueous heavy metals remediation is rarely reported. The present study investigated the removal efficiency of Cu(II) ions using wheat straw with alkali pretreatment. The condition of alkali treatment on wheat straw was optimized with the adsorption capacity of Cu(II) as indicator using single-factor experiments. The influences of wheat straw dosages, pH values, contact time, and temperatures on adsorption performance for both untreated wheat straw (UWS) and alkali-treated wheat straw (AWS) were investigated. Results showed that the relatively large removal rate of Cu(II) could be obtained, and chemical behavior occurred during the adsorption process. Characteristic analysis found that the major function of alkali treatment to wheat straw was to introduce the hydroxy group, which resulted in the increase of -C-O- group. Although the adsorption capacity is not as high as the one of ligands supported adsorbents, the method is easy to operate and has a wide range of application; at the same time, it could realize both purposes of treating heavy metal pollution and solid wastes.