Studies have suggested that ecofriendly, inexpensive, and renewable material sources are essential for developing scalable, high-performance mixed matrix membranes (MMMs). With the fact that the second-most prevalent biomacromolecule in the world of plant biology is lignin, this article delineates the effective fabrication of a lignin-based MMM utilizing polysulfone (PSf) as the base material. The influence of PSf and the lignin concentration on the properties of the fabricated membranes was examined. Also, the developed membranes were assessed for surface morphology, roughness, thickness, thermal stability, functional groups, elemental composition, mechanical strength, and hydrophilicity. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies showed that the PSf/lignin membranes possessed a rough and inconsistent morphology and comparatively greater surface porosity. The water contact angle was reduced for the 1.0 wt % PSF/ lignin membrane. Furthermore, lignin nanoparticles significantly impacted the membrane surface characteristics and decreased the ζ potential. Under the ideal experimental scenario, M2 (0.5 wt % lignin/PSf) and M3 (1.0 wt % lignin/PSf) membranes demonstrated good pure water flux values and a higher removal of 98.5 and 98.75% of Cr(VI), respectively. EDX analysis of the membranes after filtration affirmed the effective Cr(VI) removal from water. Owing to its low cost, green credentials, simplicity in synthesis, and remarkable efficiency, the newly developed PSf/lignin membrane is best suited for removing Cr(VI) and various other related contaminants from discharge aqueous effluents.

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Steel slag is a solid waste of the steel industry, produced during steel production. Three types of slag, namely electric arc furnace (EAF), basic oxygen furnace (BOF), and Linz-Donawitz processed slag (LD-slag) are the steel industry byproducts. That slag comprises precious elements including zinc (Zn), chromium (Cr), iron (Fe), nickel (Ni), silicon (Si) , aluminum (Al), and vanadium (V) and is considered a secondary source of many metals. These metal constituents can be recovered from slags by employing mineral processing techniques like crushing, grinding, magnetic separation, eddy current separation, flotation, leaching, and/or roasting. Metal extraction from steelmaking slag and slag utilization is essential not only for conserving metal supplies but also for environmental protection. This review article evaluated and summarized various extraction methods including magnetic separation, roasting, pyrometallurgical method, hydrometallurgical and bio hydrometallurgical technique to recover precious metal constituents from obtained slag. The state-of-the-art of metal recovery from slag using the aforementioned methodologies and the merits, and demerits of each procedure have been illustrated comprehensively. Suggestions have been made to overcome the shortfall and or lacuna of the technology for better performance and efficiency. The opportunities and difficulties portion of this article paints a vivid picture of turning such a beneficial technology into a more adaptable procedure with some additions that may motivate and lead future research in new directions. The essence of this survey indicates that extracted metal and treated slag might be reutilized in various fields ranging from biomedical to fertilizer applications.

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