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Flotation is an attractive method for separating the different components of waste printed circuit boards (WPCBs) due to its cleanliness and efficiency. Non-metallic particles (NMPs) with good floatability usually need to be floated, however, it is difficult to achieve complete removal. The effect of particle size on the flotation behavior of NMPs, which is usually ignored in previous studies, is concerned in this paper. Flotation tests and kinetic analysis were carried out to reveal the effect of reagent dosage on flotation characteristics of particles in narrow size fractions. As the fineness decreases, the particles are more likely to be floated. Equally, the finer the particle size, the lower the reagent dosage required to achieve the maximum recovery. For 1-0.5 mm and -0.045 mm, the maximum recovery increased from 42.16% (1500 g/t MIBC) to 97.31% (100 g/t MIBC). Therefore, the feasibility of reducing particle size by grinding to improve floatability was verified. The results show that the reduction of particle size can significantly promote its efficiency of being floated. After grinding treatment, -0.045 mm yields in each size fraction (1-0.5, 0.5-0.25, 0.25-0.125, 0.125-0.074, 0.074-0.045 mm) increased by 22.10%, 28.42%, 30.90%, 64.56%, 89.32%, resulting in an increase of 37.71%, 13.12%, 2.82%, 7.82% and 2.00% in maximum recovery, respectively. It is also proved that the particle size, rather than the resin content, has a more significant effect on the floatability of NMPs.

A study has been undertaken to investigate the effects, on the properties of foamed concrete, of replacing large volumes of cement with fly ash. This paper reports the results of the properties of foamed concrete and shows that up to 55% of the cement could be replaced without any significant reduction in compressive strength. Foamed concrete with 55% fly ash and good performance were obtained by optimizing the process parameters. The results showed that the compressive strength, dry density, water absorption and thermal conductivity of foamed concrete with 55% fly ash were 0.71MPa, 244kg/m3, 33%, and 0.045 W/mK respectively.

This present paper took ordinary Portland cement as main raw materials to prepare foam cement with properties, such as lightweight, high strength, and heat preservation, by the method of chemical foaming. The authors discussed the effects on the properties by key factors like water/cement ratio, foaming agents, foam stabilizers, accelerator and fibers of foam cement objects. Taken all the results show that in the condition that water/cement ratio of 0.48, foaming agents, foam stabilizers, accelerators and polypropylene fibers were adopted accounting for the quality of cement of 4.8%, 0.6%, 0.25% and 0.4% respectively, the characteristics of prepared formed cement samples could conform to the requirement of standard of JC/T266 formed cement.