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Item Process engineering aspects in bioleaching of metals from electronic waste(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2020) Minimol, M.; Shetty K, V.; Saidutta, M.B.Obsolete electronic devices and their components majorly contributed by the computer and mobile phone printed circuit boards (PCBs) constitute the electronic waste (e-waste). The e-wastes pose an environmental threat due to their eco-toxicological characteristics, thus making its management a mandate through an ecologically sustainable process. Further, the high concentration of metals in the e-waste makes it a secondary ore for metal recovery. Bioleaching is a bio-hydrometallurgical process, which is microbe-mediated dissolution of metals. Different nutritional classes of microorganisms like autotrophs and heterotrophs are active bioleaching agents of e-wastes. The mode of action of microbes for bioleaching of metals is obscure and is believed to ensue through redox reactions, protonic attack, or chelation. The process of bioleaching is influenced by biotic factors like the group and class of microorganism, growth rate, metabolic activity, etc. However, there are several abiotic factors that strongly affect the bioleaching efficiency. Development of a bioleaching process would need the study of various biological, nutritional, and engineering factors that influence the process. This chapter presents the critical analysis of various process engineering aspects in the bioleaching of metals from e-waste. To engineer a bioleaching process, (1) various biological, nutritional, and physicochemical factors, such as media composition, pH, e-waste loading, particle size, oxygen requirement, inoculum size, etc., should be optimized and (2) suitable bioreactor choice considering the microbial type, phases to be contacted, and the pattern of contacting followed by optimization of bioreactor operational parameters. This paper brings out a critical review of these bioprocess engineering aspects in bioleaching of metals from e-waste, directing the reader to the future scope of research on bioleaching, a bioremediation strategy to save and conserve environment for sustainable development. © 2020, Springer Nature Switzerland AG.Item Shear stress effects on production of exopolymeric substances and biofilm characteristics during phenol biodegradation by immobilized Pseudomonas desmolyticum (NCIM2112) cells in a pulsed plate bioreactor(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2016) Veena, B.R.; Shetty K, K.V.; Saidutta, M.B.This article reports studies on a continuous pulsed plate bioreactor (PPBR) with the cells of Pseudomonas desmolyticum (NCIM2112) immobilized on granular activated carbon (GAC) used as a biofilm reactor for biodegradation of phenol. Almost complete removal of 200 ppm phenol could be achieved in this bioreactor. Biofilm structure and characteristics are influenced by hydrodynamic and shear conditions in bioreactors. In this article, the effect of shear stress induced by frequency of pulsation on biofilm characteristics during the startup period in the PPBR is reported. The startup time decreased with the increase in frequency of pulsation. The formation of biofilm in PPBR was found to have three phases: accumulation, compaction, and plateau. The effect of frequency on production of exoploymeric substances (EPS) such as, protein, carbohydrate, and humic substance is reported. An increase in shear stress induced by the frequency of pulsation increased the production of exopolymeric substances in the biofilm during startup of the bioreactor. Increase in shear stress caused a decrease in biofilm thickness and an increase in dry density of the biofilm. Increase in shear stress resulted in a smoother and thinner biofilm surface with more compact and dense structure. © 2016, Copyright © Taylor & Francis Group, LLC.Item Bioleaching of copper from electronic waste using Acinetobacter sp. Cr B2 in a pulsed plate column operated in batch and sequential batch mode(Elsevier Ltd, 2017) Jagannath, A.; Shetty K, V.K.; Saidutta, M.B.The amount of metal content present in electronic waste (e-waste) such as printed circuit boards (PCBs) exceeds that present in rich minerals thus allowing the use of PCBs as artificial ores. The copper content in PCBs is 10-30 mass %, which is the highest among all the metallic elements. The recovery of copper from e-waste serves dual fold benefit of conservation of metal resources and overcoming environmental hazard due to e-waste accumulation. In the currently reported study, a pulsed plate bioreactor in which the inter-plate spaces were packed with e-waste material was effectively employed for bioleaching of copper from e-waste using Acinetobacter sp. Cr B2. Various factors such as inoculum size, e-waste loading, frequency and amplitude of pulsation that significantly affected the bioleaching efficiency were studied. Inoculum size of 9% (v/v), frequency of 0.2 s-1, amplitude of 6.5 cm and total e-waste loading of 40 g with 10 g/stage were found to provide maximum bioleaching of Cu. Around 23% of Cu bioleaching was achieved under these conditions by batch mode of operation. Increasing the number of sequential cycles of operation in sequential batch mode further improved the bioleaching efficiency, by overcoming the maximum copper solubility and growth limitations of the single batch operation. With five cycles of sequential batch operation around 63% leaching of Cu could be achieved. The bioleaching was found to be mediated both by the action of extracellular enzymes and metabolites. The study demonstrated the potential application of pulsed plate bioreactor for larger scale application of copper bioleaching from PCBs. © 2017 Elsevier Ltd. All rights reserved.Item Bioleaching of zinc from e-waste by A. aquatilis in fluidised bed bioreactor(Taylor and Francis Ltd., 2023) Minimol, M.; Shetty K, V.; Saidutta, M.B.Technological advancements with the use of new-generation electronic devices and accumulated electronic wastes (e-wastes) raise environmental concerns. E-waste, especially mobile phone Printed Circuit Boards (PCBs) is a rich source of metals. Bioleaching, a microbe-mediated metal dissolution process is employed for the recovery of metals. The operational parameters like particle size, inoculum percentage (v/v) and e-waste load (w/v) were optimised for Zn bioleaching by Alcaligenes aquatilis in shake flasks and fluidised bed bioreactor (FBR). The e-waste feed particle size of 0.175 mm and 5% inoculum was found to be the optimum for Zn bioleaching in both the shake flask and FBR. The optimum e-waste load was 5% in the shake flask and 2% in FBR. The maximum recovery of Zn was 0.6 mg/g (13.73%) in the shake flask and 0.57 mg/g (13%) in FBR, implying that FBR exhibits similar efficiency of Zn bioleaching as in the shake flask. Further three sequential batch runs increased the recovery to a maximum of 1.66 mg/g from 4.37 mg/g Zn present in the PCBs ie., 38% Zn recovery. This shows that efficient bioleaching of Zn on a larger scale can be achieved with sequential batches and applied for the simultaneous recovery of metals from PCBs. © 2023 Indian Institute of Chemical Engineers.Item Performance of Fluidized-Bed Bioreactor in Copper Bioleaching from Printed Circuit Boards using Alcaligenes aquatilis(Springer Science and Business Media B.V., 2024) Madhavan, M.; Shetty K, V.; Saidutta, M.B.Technological advancements have led to a demand for modern electronic gadgets and outdated ones discarded as electronic waste (e-waste). The printed circuit boards (PCBs) constitute a significant portion of these wastes that contain hazardous substances that mandate e-waste management. The rich source of precious and base metals makes it a resource for urban mining. Bioleaching, a process of biohydrometallurgy, an alternative to conventional heat and chemical-based metal recovery processes, can be efficiently applied for metal recovery from these wastes in an environmentally safe manner. The process parameters like particle size, inoculum size (v/v), and e-waste load (w/v) for bioleaching of Cu from PCBs in a Fluidized-Bed bioreactor (FBR) and shake flask using Alcaligenes aquatilis as bioleaching agent were optimized. The bioleaching of 47.99% and 37.54% of Cu from PCBs were achieved in shake flask and FBR, respectively. The optimal conditions of Cu bioleaching were 0.175 mm particle size, 5% (v/v) inoculum, and 2% (w/v) e-waste load with 169.45 mg/g and 132.55 mg/g of Cu recovery in shake flask and FBR at 84 and 96 h, respectively. Further, the Cu bioleaching was carried out in sequential batches to improve the recovery with the optimized conditions. There was a prominent increase in the cumulative %Cu bioleaching of about 80.02% after three sequential batch experiments from PCBs with an initial Cu concentration of 353.09 mg/g. The present study proves that sustainable heterotrophic bioleaching of Cu can be efficiently achieved in a Fluidized-bed bioreactor operated in sequential batch mode by Alcaligenes aquatilis. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer Nature B.V. 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.