Valorization of waste NiMH battery through recovery of critical rare earth metal: A simple recycling process for the circular economy.

The process flowsheet consists of three main circuits, i.e., metal extraction by acid leaching, critical rare earth metal (REM) recovery from leach liquor and pure Co/Ni recovery by solvent extraction. Quantitative metal extraction using 1 M H2SO4, pulp density of 25 g/L at 90 °C from waste NiMH battery was achieved. From leach liquor using 10 M NaOH, at pH 1.8, more than 99% REM was precipitated out and isolated through calcination at 600 °C. Undesired metals like Mn, Al, Zn, and Fe were scrubbed out from the leach liquor using 0. 7 M D2EPHA at the equilibrium pH of 2.30. From the scrubbed raffinate Co and Ni was separated using 0.5 M Cyanex 272 at pH 4.70 through solvent extraction. At pH 4.70 Co was completely extracted from solution leaving Ni in solution, which can be recovered completely. From Co loaded Cyanex 272, the Co was stripped by 1 M H2SO4 and regenerated Cyanex 272 can be reused and close the loop. Similarly, the undesired metal loaded D2EPHA can be regenerated and reused and close the loop. As the process is close-loop process recovers critical REMs, Co, and Ni, the valorization process efficiently addresses the circular economy and recycling challenges associated with waste NiMH battery.

Synthesis of submicron silver powder from scrap low-temperature co-fired ceramic an e-waste: Understanding the leaching kinetics and wet chemistry.

The current study focuses on the understanding of leaching kinetics of metal in the LTCC in general and silver leaching in particular along with wet chemical reduction involving silver nanoparticle synthesis. Followed by metal leaching, the silver was selectively precipitated using HCl as AgCl. The precipitated AgCl was dissolved in ammonium hydroxide and reduced to pure silver metal nanopowder (NPs) using hydrazine as a reductant. Polyvinylpyrrolidone (PVP) used as a stabilizer and Polyethylene glycol (PEG) used as reducing reagent as well as stabilizing reagent to control size and shape of the Ag NPs. An in-depth investigation indicated a first-order kinetics model fits well with high accuracy among all possible models. Activation energy required for the first order reaction was 21.242 kJ mol-1 for Silver. PVP and PEG 1% each together provide better size control over silver nanoparticle synthesis using 0.4 M hydrazine as reductant, which provides relatively regular morphology in comparison to their individual application. The investigation revealed that the waste LTCC (an industrial e-waste) can be recycled through the reported process even in industrial scale. The novelty of reported recycling process is simplicity, versatile and eco-efficiency through which waste LTCC recycling can address various issues like; (i) industrial waste disposal (ii) synthesis of silver nanoparticles from waste LTCC (iii) circulate metal economy within a closed loop cycle in the industrial economies where resources are scarce, altogether.

Selective recovery of silver from waste low-temperature co-fired ceramic and valorization through silver nanoparticle synthesis.

Considering the value of silver metal and silver nanoparticles, the waste generated during manufacturing of low temperature co-fired ceramic (LTCC) were recycled through the simple yet cost effective process by chemical-metallurgy. Followed by leaching optimization, silver was selectively recovered through precipitation. The precipitated silver chloride was valorized though silver nanoparticle synthesis by a simple one-pot greener synthesis route. Through leaching-precipitation optimization, quantitative selective recovery of silver chloride was achieved, followed by homogeneous pure silver nanoparticle about 100nm size were synthesized. The reported recycling process is a simple process, versatile, easy to implement, requires minimum facilities and no specialty chemicals, through which semiconductor manufacturing industry can treat the waste generated during manufacturing of LTCC and reutilize the valorized silver nanoparticles in manufacturing in a close loop process. Our reported process can address issues like; (i) waste disposal, as well as value-added silver recovery, (ii) brings back the material to production stream and address the circular economy, and (iii) can be part of lower the futuristic carbon economy and cradle-to-cradle technology management, simultaneously.