Shape separation of particulates by a rotating horizontal sieve drum

Value-added products from thermochemical treatments of contaminated e-waste plastics

The rise of electronic waste (e-waste) generation around the globe has become a major concern in recent times and its recycling is mostly focused on the recovery of valuable metals, such as gold, silver, and copper, etc. However, e-waste consists of a significant weight fraction of plastics (25-30%) which are either discarded or incinerated. There is a growing need for recycling of these e-waste plastics. The majority of them are made from high-quality polymers (composites), such as acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS), polycarbonate (PC), polyamide (PA), polypropylene (PP) and epoxies. These plastics are often contaminated with hazardous materials, such as brominated flame retardants (BFRs) and heavy metals (such as Pb and Hg). Under any thermal stress (thermal degradation), the Br present in the e-waste plastics produces environmentally hazardous pollutants, such as hydrogen bromide or polybrominated diphenyl ethers/furans (PBDE/Fs). The discarded plastics can lead to the leaching of toxins into the environment. It is important to remove the toxins from the e-waste plastics before recycling. This review article gives a detailed account of e-waste plastics recycling and recovery using thermochemical processes, such as extraction (at elevated temperature), incineration (combustion), hydrolysis, and pyrolysis (catalytic/non catalytic). A basic framework of the existing processes has been established by reviewing the most interesting findings in recent times and the prospects that they open in the field recycling of e-waste plastics.

Shape-based separation of micro-/nanoparticles in liquid phases

The production of particles with shape-specific properties is reliant upon the separation of micro-/nanoparticles of particular shapes from particle mixtures of similar volumes. However, compared to a large number of size-based particle separation methods, shape-based separation methods have not been adequately explored. We review various up-to-date approaches to shape-based separation of rigid micro-/nanoparticles in liquid phases including size exclusion chromatography, field flow fractionation, deterministic lateral displacement, inertial focusing, electrophoresis, magnetophoresis, self-assembly precipitation, and centrifugation. We discuss separation mechanisms by classifying them as either changes in surface interactions or extensions of size-based separation. The latter includes geometric restrictions and shape-dependent transport properties.

Mechanical recycling of waste electric and electronic equipment: a review

The production of electric and electronic equipment (EEE) is one of the fastest growing areas. This development has resulted in an increase of waste electric and electronic equipment (WEEE). In view of the environmental problems involved in the management of WEEE, many counties and organizations have drafted national legislation to improve the reuse, recycling and other forms of recovery of such wastes so as to reduce disposal. Recycling of WEEE is an important subject not only from the point of waste treatment but also from the recovery of valuable materials.WEEE is diverse and complex, in terms of materials and components makeup as well as the original equipment's manufacturing processes. Characterization of this waste stream is of paramount importance for developing a cost-effective and environmentally friendly recycling system. In this paper, the physical and particle properties of WEEE are presented. Selective disassembly, targeting on singling out hazardous and/or valuable components, is an indispensable process in the practice of recycling of WEEE. Disassembly process planning and innovation of disassembly facilities are most active research areas. Mechanical/physical processing, based on the characterization of WEEE, provides an alternative means of recovering valuable materials. Mechanical processes, such as screening, shape separation, magnetic separation, Eddy current separation, electrostatic separation, and jigging have been widely utilized in recycling industry. However, recycling of WEEE is only beginning. For maximum separation of materials, WEEE should be shredded to small, even fine particles, generally below 5 or 10mm. Therefore, a discussion of mechanical separation processes for fine particles is highlighted in this paper. Consumer electronic equipment (brown goods), such as television sets, video recorders, are most common. It is very costly to perform manual dismantling of those products, due to the fact that brown goods contain very low-grade precious metals and copper. It is expected that a mechanical recycling process will be developed for the upgrading of low metal content scraps.