One-Step Synthesis and Functionalization of High-Salinity-Tolerant Magnetite Nanoparticles with Sulfonated Phenolic Resin.

Superparamagnetic nanoparticles are being actively developed for various applications in oil fields. A key requirement for such nanoparticles is the long-term stability of their dispersion under harsh subsurface conditions such as high salinity and high temperature. In this study, through functionalization of the surface of the magnetite nanoparticles with a sulfonated phenolic resin, stable dispersions of the nanoparticles in 5 wt % NaCl solution at neutral to basic pH were achieved. Sulfonated phenolic resin is aromatic in nature and can endure high temperatures; moreover, the strongly anionic sulfonate groups facilitate sufficient electrostatic repulsion between the particles even in a highly saline environment. Sulfonated phenolic resin was synthesized by heating a mixture of 4-hydroxybenzenesulfonic acid and formaldehyde at 1:1 molar ratio. Then, by synthesizing magnetite nanoparticles by a co-precipitation process in a solution of sulfonated phenolic resin, one-pot synthesis/surface functionalization was accomplished, which not only simplifies the manufacturing process but also can potentially lower the cost of production owing to the use of readily available phenolic resins. The reliability of the technique was confirmed by the detailed characterization of the nanoparticle through size distribution analysis, thermogravimetric analysis, ζ-potential measurements, transmission electron microscopy imaging, and energy-dispersive X-ray spectroscopy mapping. Further, Langevin curve was generated for evaluating the superparamagnetism of the nanoparticles.

Shredding and liberation characteristics of refrigerators and small appliances.

Mechanical disaggregation, or shredding, is an important part of the recycling process. Occurring at the beginning of the processing sequence, it significantly affects the efficiency of downstream processing stages. This study examines the size reduction and liberation characteristics of the single-stage shredding of household appliances to improve the efficiency and quality of the recycling process. Several disposed appliances, including 75L refrigerators and five major categories of small appliances (vacuum cleaners, videocassette recorders (VCRs), electric rice cookers, fans, and electric heaters), were shredded using a high-speed vertical shredder under varying discharge clearance conditions. The fragments were analyzed according to size, composition, and degree of liberation. It was found that single-stage crushing with the high-speed vertical shredder was sufficient to produce fragments at an appropriate size and with a high degree of liberation. Based on the experimental results, an optimal shredding and separation scheme for the process is proposed.