Microfluidic solvent extraction, stripping, and phase disengagement for high-value platinum chloride solutions

Process intensification for sustainable extraction of metals from e-waste: challenges and opportunities

The electrical and electronic waste is expected to increase up to 74.7 million metric tons by 2030 due to the unparalleled replacement rate of electronic devices, depleting the conventional sources of valuable metals such as rare earth elements, platinum group metals, Co, Sb, Mo, Li, Ni, Cu, Ag, Sn, Au, and Cr. Most of the current techniques for recycling, recovering, and disposing of e-waste are inappropriate and therefore contaminate the land, air, and water due to the release of hazardous compounds into the environment. Hydrometallurgy and pyrometallurgy are two such conventional methods used extensively for metal recovery from waste electrical and electronic equipment (WEEE). However, environmental repercussions and higher energy requirements are the key drawbacks that prevent their widespread application. Thus, to ensure the environment and elemental sustainability, novel processes and technologies must be developed for e-waste management with enhanced recovery and reuse of the valued elements. Therefore, the goal of the current work is to examine the batch and continuous processes of metal extraction from e-waste. In addition to the conventional devices, microfluidic devices have been also analyzed for microflow metal extraction. In microfluidic devices, it has been observed that the large specific surface area and short diffusion distance of microfluidic devices are advantageous for the efficient extraction of metals. Additionally, cutting-edge technologies have been proposed to enhance the recovery, reusability, and recycling of e-waste. The current study may support decision-making by researchers in deciding the direction of future research and moving toward sustainable development.

Photometric Sensing of Active Chlorine, Total Chlorine, and pH on a Microfluidic Chip for Online Swimming Pool Monitoring

A microfluidic sensor was studied for the photometric detection of active chlorine, total chlorine, and pH in swimming pool samples. The sensor consisted of a four-layer borosilicate glass chip, containing a microchannel network and a 2.2 mm path length, 1.7 mL optical cell. The chip was optimised to measure the bleaching of methyl orange and spectral changes in phenol red for quantitative chlorine (active and total) and pH measurements that were suited to swimming pool monitoring. Reagent consumption (60 mL per measurement) was minimised to allow for maintenance-free operation over a nominal summer season (3 months) with minimal waste. The chip was tested using samples from 12 domestic, public, and commercial swimming pools (indoor and outdoor), with results that compare favourably with commercial products (test strips and the N,N'-diethyl-p-phenylenediamine (DPD) method), precision pH electrodes, and iodometric titration.