Abstract
Due to high production costs, the popularization and application of microbial flocculants in the field of water treatment have been limited. In this study, the capture of lead ions by the fermentation broth of a novel Paenibacillus sp. strain A9 and cultured with food wastewater was further investigated. The results revealed that the production of MBFA9 could be increased significantly by adding a small amount of carbon and nitrogen to food wastewater. Under the best experimental conditions (pH 8.5, culture temperature 30°C, 150 r/min), adding 1% (m/v) carbon and 0.1% (m/v) nitrogen to 1% (v/v) wastewater resulted in a yield of MBFA9 of 6.29 g/l. At a temperature of 30°C, pH of 5, contact time of 35 min, and FBA9 dosage of 5%, the removal rate and removal capacity of Pb(II) reached the highest values of 95.1% and 317 mg/g, respectively. Field emission scanning electron microscopy analysis indicated that bacterial cells, metabolite small molecule acids, and MBFA9 in FBA9 all contributed to the removal of Pb(II). Fourier-transform infrared spectrometry analysis indicated that functional groups such as –OH, –COOH, –CO, and –NH2 existed in MBFA9 and on the cell surface. Various mechanisms involved in Pb(II) removal can occur simultaneously, including cell surface adsorption, microcrystallization, and biological flocculation.
Highlights
With the development of industrial production, the amount of heavy metals discharged to the environment is increasing, resulting in different degrees of water pollution (Ao and Guan, 2018; Zhang et al, 2019)
10 min was selected as the best contact time for Pb(II) adsorption from the solution by the fermentation broth A9 (FBA9), which is much lower than the results reported in earlier previous studies of the adsorption of metal ions on various biomasses or bioflocculants (Feng et al, 2013)
The results indicated that MBF produced by strain A9 (MBFA9) can be successfully used for the removal of Pb(II) from aqueous solution
Summary
With the development of industrial production, the amount of heavy metals discharged to the environment is increasing, resulting in different degrees of water pollution (Ao and Guan, 2018; Zhang et al, 2019). The removal of heavy metals by microbial methods has many advantages, such as low cost, simple operation, strong selectivity, and good treatment effect. Yao et al (2013) used MBF produced by the flocculant-producing bacteria Bacillus mucilaginosus to treat wastewater containing Fe(III) and Pb(II) and introduced CO2 to enhance the removal effect. They found that MBF has an adsorption effect on metal ions and can be used as a nucleating medium for the formation of carbonate minerals via reaction with CO2. Many studies have investigated the adsorption of cadmium, lead, chromium, and other heavy metals by microbial cells. Zeng et al (2008)
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