Search

The emerging problem of electronic waste has promoted the interest in exploring metal recovery from secondary sources under the umbrella of urban mining. This study presents the physical and chemical characterization of various components present in end-of-life laptops to help ascertain the sites of metallic values and develop sustainable and environment-friendly recycling. The recycling potential of a laptop is evaluated by sequential disassembly, separation, and characterization of components such as body (49.8 wt.%), printed circuit board (9.7 wt.%), hard disk drive (4.9 wt.%), and battery (12.4 wt.%). The printed circuit boards comprise metallic values, majorly copper (25 wt.%), tin (5.8 wt.%), and lead (3.1 wt.%). The precious metals (Au, Ag) with an economic advantage are abundantly present in electronic components such as integrated circuits, capacitors, resistors, and processors. Critical elements such as lithium, cobalt, and rare earth elements are detected in the discarded laptops' batteries and hard disk drives. The recycling potential representing the amount of material that can be recycled in various components, depending on the type, concentration, and purity, is determined in the range of 36–100%. On average, a unit laptop contains~ 386 g of Cu (14.45 wt. %), 49.73 g Co (1.86 wt. %), ~346 mg Ag, ~141.2 mg Au, ~650 mg of rare earth elements (Nd, Dy). This study presents a database for investigating integrated and economical recycling techniques from different components of a laptop, and an overall process flow is also proposed.

The recovery of metals from discarded printed circuit boards using environmentally-friendly physical routes is gaining importance. Physical separation of metal values from non-metallic constituents exploits various characteristics of crushed powder such as density, liberation, shape, size, and wettability. However, the generation of fines during grinding/crushing of the printed circuit boards is an unavoidable but essential by-product. The fine fractions are discarded due to the higher amounts of non-metallic fraction and poor separation of metallic values. In this study, the flotation process was studied to separate metallic and non-metallic values without the addition of external additives from the fine fraction of printed circuit boards (

The current study investigates the effect of microwave processing on low-grade banded iron ore using charcoal, coking coal, and non-coking coal. Charcoal showed better microwave heating response at low temperatures, and the coals exhibit better heating response at higher temperatures. Low carbon dosage ~ 12% is sufficient to generate concentrate with 61.8% iron grade and ~6% for 94.8% iron recovery comprising of magnetite phase suitable for iron-making applications. The process separation efficiency of ~ 95% is achieved at 6% carbon dosage and decreases with an increase in carbon due to formation of the fayalite phase. The metallization degree showed a strong dependency on reductant dosage and achieved a maximum value of 22.7% at 18% charcoal. The comparison of ore with pure iron oxide and the synthetic mixture of iron oxide indicated that the underlying bonding due to banded structure enhances the Joule heating during microwave irradiation and thereby aids in attaining higher temperature and better separation.

Printed circuit boards (PCBs) are an essential and central component of electronic waste. The rapid depletion of natural resources, massive generation of end-of-life PCBs and inherently metal-loaded values inevitably call for recycling and recovery. This review critically discusses the systematic and sequential processes adopted for PCB metallic recoveries via physical, pyrometallurgical, hydrometallurgical, and combined technologies. Pre-treatments play a decisive and significant role in upgradation and efficient metal extraction. A novel combination of different pre-treatments and hybrid thermal-chemical routes are often reported for improved separation efficiency and performance. Selective recovery (using solvent extraction, precipitation, polymer inclusion membrane, adsorption, ion exchange) of high purity product from multi-elemental leach solution has recently gained interest and is reviewed. Current recycling techniques at a commercial scale are preferably based on pyrometallurgy (smelting-refining), where electronic waste is only a fraction of the total feed stream. Electronic components such as monolithic ceramic capacitors, tantalum capacitors, integrated circuits, and central processing units mounted on the PCBs are important due to precious metals' presence. The futuristic recycling perspective should treat base and precious metal-rich components separately with minimal environmental effect, end product usage, and maximum economic benefit. Sustainable processing routes for converting discarded PCBs into value-added products should also be attempted, as amplified in this review. An integrated, definite framework for full resource recovery from waste PCBs was proposed.