Search

Biofouling has been persisting as a worldwide problem due to the difficulties in finding efficient environment-friendly antifouling coatings for long-term applications. Developing novel coatings with desired antifouling properties has been one of the research goals for surface coating community. Recently hydrogel coating was proposed to serve as antifouling layer, for it offers the advantages of the ease of incorporating green biocides, and resisting attachment of microorganisms by its soft surface. Yet poor adhesion of the hydrogel on steel surfaces is a big concern. In this study, porous matrix aluminum coatings were fabricated by cored wire arc spray, and the sizes of the pores in the aluminum (Al) coatings were controlled by altering the size of the cored powder of sodium chloride. Silicone hydrogel was further deposited on the porous coating. The hydrogel penetrated into the open pores of the porous Al coatings, and the porous Al structure significantly enhanced the adhesion of the hydrogel. In addition, hydrogel coating exhibited very encouraging antifouling properties.

Electrolytic manganese residue (EMR) is a type of industrial solid waste with a high silicon content. The silicon in EMR can be used as an essential nutrient for plant growth, but most of the silicon is found in silicate minerals with very low water solubility, that is, it is inactive silicon and cannot be absorbed and used by plants directly. Thus, developing a highly effective and environmentally friendly process for the activation of silicon in EMR is important both for reusing solid waste and environmental sustainability. The aim of this study was to investigate the desilication of EMR using cultures of Paenibacillus mucilaginosus (PM) and Bacillus circulans (BC). The results showed that the two types of silicate bacteria and a mixed strain of them were all able to extract silicon from EMR with a high efficiency, but the desilication performance of the mixed PM and BC was the best. Fourier transform infrared spectroscopy indicated that silicate bacteria can induce a suitable micro-environment near the EMR particles and release Si into the solution through their metabolism. X-ray diffraction analysis confirmed that layered crystal minerals, such as muscovite and diopside, were more likely to be destroyed by the bacterial action than quartz, which has a frame structure. Scanning electron microscopy-energy dispersive spectrometry proved that the silicate structures were destroyed and that Si in the residue was decreased, indicating the dissolution of silicon under the action of these microorganisms. This study suggests that bioleaching may be a promising method for the activation of silicon in EMR.

Electrolytic manganese residue (EMR) is a kind of solid waste generated along with the production of electrolytic manganese, with a high content of quartz and metals. The former can be used as silicon fertilizer for crops after activation, while the latter may cause harm to surrounding environment due to their toxicity. The aim of this study was to investigate the effects of bacterial on the activation of silicon and fixation of heavy metals in EMR by using microbe-mineral direct contact and indirect contact methods. Mixed cultures of Bacillus mucilaginosus (BM) and Bacillus circulans (BC) were used to achieve activation of silicon in EMR, and the leaching concentration of Mn, Co and Ni and their chemical forms in the leaching residue were also investigated. The results show that the microbe-mineral direct contact method has better performance for the activation of silicon in EMR with the available silicon in the leaching solution up to 163.27 mg L−1 than the indirect contact method. The metals (Mn, Co and Ni) remaining in the residue mainly exist as the stable state after bioleaching, with lower leaching concentration after bioleaching of 20 d. And the effect of silicon bacteria on activation of silicon and the fixation mechanism of metals including the effect of silicate and silicate bacteria is confirmed, and it is verified by the identification of metabolites and the analysis of chemical reaction process. This study investigates the treatment of EMR by using mixed silicate bacteria, and reveals the mechanisms of bacteria on the activation of silicon and fixaion of heavy metals in EMR. The bioleaching method not only provides silicon source for soil but also can realize the reclamation of EMR.