The increasing use of electrical and electronic equipment leads to a huge generation of electronic waste (e-waste). It is the fastest growing waste stream in the world. Almost all electrical and electronic equipment contain printed circuit boards as an essential part. Improper handling of these electronic wastes could bring serious risk to human health and the environment. On the other hand, proper handling of this waste requires a sound management strategy for awareness, collection, recycling, and reuse. Nowadays, the effective recycling of this type of waste has been considered as a main challenge for any society. Printed circuit boards (PCBs), which are the base of many electronic industries, are rich in valuable heavy metals and toxic halogenated organic substances. In this review, the composition of different PCBs and their harmful effects are discussed. Various techniques in common use for recycling the most important metals from the metallic fractions of e-waste are illustrated. The recovery of metals from e-waste material after physical separation through pyrometallurgical, hydrometallurgical, or biohydrometallurgical routes is also discussed, along with alternative uses of non-metallic fraction. The data are explained and compared with the current e-waste management efforts done in Egypt. Future perspectives and challenges facing Egypt for proper e-waste recycling are also discussed.

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For the past few decades, a plethora of nanoparticles have been produced through various methods and utilized to advance technologies for environmental applications, including water treatment, detection of persistent pollutants, and soil/water remediation, amongst many others. The field of materials science and engineering is increasingly interested in increasing the sustainability of the processes involved in the production of nanoparticles, which motivates the exploration of alternative inputs for nanoparticle production as well as the implementation of green synthesis techniques. Herein, we start by overviewing the general aspects of nanoparticle synthesis from industrial, electric/electronic, and plastic waste. We expand on critical aspects of waste identification as a viable input for the treatment and recovery of metal-and carbon-based nanoparticles. We follow-up by discussing different governing mechanisms involved in the production of nanoparticles, and point to potential inferences throughout the synthesis processes. Next, we provide some examples of waste-derived nanoparticles utilized in a proof-of-concept demonstration of technologies for applications in water quality and safety. We conclude by discussing current challenges from the toxicological and life-cycle perspectives that must be taken into consideration before scale-up manufacturing and implementation of waste-derived nanoparticles.

We demonstrate development of electrochemical nanosensors for planetary health applications using nanocuprous oxide synthesized from recycled materials. Laser-scribed graphene electrodes were enhanced with copper liberated from waste cables, and cuprous oxide nanospheres were synthesized via precipitation at low temperature using lactose as a reducing agent and four different surfactants as capping agents. These laser-scribed electrodes are a low-cost, lithography-free approach to direct synthesis of flexible carbon circuits. Sensors were fabricated by anchoring nanoparticles to flexible graphene electrodes, and then material properties and sensor performance were compared for each surfactant. Surfactant molecular weight and terminal group played an important role in nanoparticle size, band gap, ferromagnetic response, and electron transport. As proof of principle, we show development of catecholamine and mercury sensors for planetary health applications using the best material. Dopamine sensors were linear from 300 nM to 5 μM, with a detection limit of 200 nM, response time of 2.4 ± 0.7 s, and sensitivity of 30 nA μM cm2. Mercury sensors were linear from 0.02 to 2.5 ppm, with a detection limit of 25 ppb, response time of <3 min, and sensitivity of 10 nA ppm–1. The methods shown here are facile, environmentally friendly, and economical. Green synthesis of flexible sensors and electronic devices with recovered waste represents a sustainable approach for next-generation flexible carbon sensors for planetary health applications.

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