| During recent years, pollution of the aquatic environment is spreading throughout the world along with industrial development, which seriously threats to public health and ecological environment. Therefore, it is of great importance to develop better strategies for treating water resource contaminated by kinds of heavy metal ions, dyes and microorganisms. Many methods have been used for decontamination and/or disinfection in water remediation, adsorption is considered to be one of the most effective and economical approaches for water purification among them. With the development of nanotechnology, nanomaterial used as adsorbents exhibited enhanced adsorption capacity in wastewater treatment. Nanosized MgO(nano-MgO) as an inorganic metal oxide is an inexpensive, abundant, nontoxic and environmentally friendly nanomaterial, which has excellent adsorption capacity for heavy metal ions, organic dyes, and microorganism removal from aqueous solution. This paper focuses on the treatment of dyes, heavy metal ions and microorganism through MgO nanoparticles. The details were summarized as follows:(1) Nano-MgO were prepared by a simple sol-gel method, SEM, XRD, FTIR, XPS and BET were used to characterize the phase structure, morphology and specific surface area of the as-synthesized nano-MgO, the obtained nano-MgO exhibited uniform dispersion with particle size in the range of 20-30 nm. MO and E. coli were selected as experimental model dyes and bacterium, respectively. The adsorption of MO and the disinfection of E.coli used the synthesized nano-MgO was investigated under different conditions, such as the initial MO concentration and contact time. The results showed that 5 mg/L MO had no toxicity towards bacterial cells, and when 1 g/L MgO was added into the E. coli suspension in the absence of MO, nearly 6-log bacterial cells were inactivated within 1 h. However, when the synthesized nano-MgO was put into the E. coli-MO system, the synthesized nano-MgO did not exhibit higher antibacterial efficiency against E. coli in the presence of MO than in the absence of MO. Surprisingly, when the concentration of MO increased, the antibacterial activity of the synthesized nano-MgO decreased.(2)Cd2+, Pb2+ and E. coli were selected as experimental model heavy metals and bacterium, respectively. The synthesized nano-MgO through sol–gel technique was applied to simultaneously inactivate bacteria and remove heavy metal ions in water, and the mechanisms of bacterial inactivation and heavy metal ion removal by the synthesized nano-MgO were studied in details. It was found that 100 mg/L the synthesized nano-MgO could almost completely inactivate 7-log bacterial cells and removed 50 mg/L Cd2+ within 30 and 10 min, respectively. Significantly, the promotion of antibacterial effect of the synthesized nano-MgO towards E. coli was found in the presence of Cd2+. In a non-partition system, the concentration of Cd2+ at 10 mg/L maximally enhanced the antibacterial activity of the synthesized nano-MgO, while the antibacterial activity of the synthesized nano-MgO gradually increased with the concentration of Cd2+ in the partition system. In addition, 100 mg/L the synthesized nano-MgO could not completely inactivate 7-log bacterial cells within 2 h, and in E. coli-Cd2+-Pb2+ system, a competitive adsorption was observed, showing preference of adsorption in the order of Pb2+ > Cd2+. Furthermore, the study on mechanism of Cd2+ removal and E. coli inactivation indicated that Cd2+ was precipitated in the forms of CdCO3 and Cd(OH)2, accompanied with the mineralization of E. coli. ROS generation and the direct interaction between MgO and cell were considered to be two main reasons for the antibacterial activity of the synthesized nano-MgO, which can attack E. coli cell membrane. After the cell membrane was damaged, heavy metal ions entered easily into cell body to accelerate bacterial inactivation. |
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