Internet of Things for Sustainable Mining

The sustainable mining Internet of Things deals with the applications of IoT technology to the coupled needs of sustainable recovery of metals and a healthy environment for a thriving planet. In this chapter, the IoT architecture and technology is presented to support development of a digital mining platform emphasizing the exploration of rock–fluid–environment interactions to develop extraction methods with maximum economic benefit, while maintaining and preserving both water quantity and quality, soil, and, ultimately, human health. New perspectives are provided for IoT applications in developing new mineral resources, improved management of tailings, monitoring and mitigating contamination from mining. Moreover, tools to assess the environmental and social impacts of mining including the demands on dwindling freshwater resources. The cutting-edge technologies that could be leveraged to develop the state-of-the-art sustainable mining IoT paradigm are also discussed

Mixed matrix nanofiber as a flow-through membrane adsorber for continuous Li⁺ recovery from seawater

© 2016 Elsevier B.V. A polysulfone (PSf)-based mixed matrix nanofiber (MMN) dispersed with particulate lithium ion sieves (LIS) was developed as a flow-through membrane Li+ adsorber. The MMN was prepared via electrospinning, thermal annealing, and acid pickling (i.e. activated LIS: Li0.67H0.96Mn1.58O4 or MO). The unique dimensional property of the macroporous MMN promoted high MO exposure and distribution on the nanofiber surface. Minimal losses in Li+ adsorption capacity and kinetics, elicited by the PSf matrix, were observed. Moreover, the PSf matrix effectively improved the Li+ selectivity of MO as it alleviated the sorption of interfering cations. As membranes, the MMNs were highly permeable to water under minimal trans-membrane pressure. The convective flow of seawater through the highly accessible MMN facilitated the fast Li+ transport to the MO surface. Breakthrough studies revealed that a balance between kinetics and dynamic Li+ adsorption capacity could be obtained at optimal seawater/MMN contact time, which was easily achieved by adjusting the feed flow-rate or MMN thickness. Continuous flow-through operations were successfully controlled at a very short adsorption-desorption cycle time (one day) while maintaining the dynamic Li+ adsorption capacity of the MMN. Cycled operations confirmed the regenerability of the MMN and its adsorption performance consistency. Enrichment of Li+ was successfully done by repeated Li+ desorption in a small volume of acid solution. Overall results demonstrated the strong potential of the flow-through MMN membrane adsorber for continuous Li+ recovery from alternative resources like seawater

Macroporous flexible polyvinyl alcohol lithium adsorbent foam composite prepared via surfactant blending and cryo-desiccation

© 2015 Elsevier B.V. Macroporous polyvinyl alcohol (PVA) foam composites with high loading of uniformly distributed lithium ion sieves (LIS) were successfully fabricated and evaluated for Li+ recovery. Surfactant blending combined with cryo-desiccation effectively produced LIS/PVA foams with hierarchical porosity composed of macro- and mesopores. Glutaraldehyde cross-linking rendered the LIS/PVA foams insoluble in water but exhibited high water absorbency and flexibility. Relative to the LIS powder, the foams exhibited minimal reductions in adsorption capacity (qe) and kinetic properties due to: (1) high total porosity and surface area, (2) hydrophilicity of PVA matrix, and (3) high LIS loading, which promoted particle exposure on the foam surface. These features facilitated easy convective flow of water through the matrix and allowed intimate contact between the Li+ feed source and the LIS surface. Thus, LIS/PVA foams with high loadings (200-300wt%) exhibited meager reductions in qe (7-13%) and kinetic properties compared to the LIS powder. With LIS loading increase, Li+ selectivity of LIS/PVA foams against other cations (i.e. Na+, K+, Mg2+, Ca2+) likewise approached that of the LIS powder. While 300wt% LIS/PVA had low mechanical property, lower LIS loadings of 200- and 250wt% were highly durable and exhibited no deterioration in adsorption performance and reusability. Among the prepared LIS/PVA, 250wt% demonstrated the highest adsorption performance and can be repeatedly used for long-term application. The developed LIS/PVA foams are promising Li+ adsorbents for secondary Li+ sources; application of these foams via a simple "absorb and squeeze" mechanism could be more practical than the energy-intensive processes like packed bed and membrane systems

Continuous lithium mining from aqueous resources by an adsorbent filter with a 3D polymeric nanofiber network infused with ion sieves

© 2016 Elsevier B.V. Electrospun composite nanofiber (NF) was fabricated and employed as an adsorbent membrane filter in a continuous Li+ mining process from seawater. The filter was composed of a hydrophilic polyacrylonitrile (PAN) matrix infused with lithium ion sieves (LIS) H1.6Mn1.6O4. Characterization of the LIS/PAN NF confirmed its favorable structural and surface properties for effective Li+ adsorption. The LIS/PAN NF was mechanically suitable as a microfiltration membrane with high water flux and low pressure requirement. Breakthrough experiments at varied feed concentrations (Cf), seawater flowrates (F), and NF thicknesses (Z) revealed the dynamic adsorption behavior of the filter. The seawater residence time was most critical and must be kept ⩾0.12 min at any given Cf and Z to maximize the Li+ capacity of the filter. This can be conveniently achieved by adjusting the F of the process. Analogous to a packed bed system, the predictive power of nine breakthrough models were determined through non-linear regression analyses. Results reveal that bed-depth-space-time, Bohart-Adams (BA) and Thomas models adequately predicted the performance of the filter albeit BA exhibited the best agreement. Meanwhile, Wolborska failed to converge with any of the experimental results while Yoon-Nelson, Wang, Clark, dose-response, and modified dose-response were too simple to provide any meaningful information. Cycled Li+ adsorption-desorption runs successfully collected and concentrated Li+ in a mild acid stripping solution. After ten cycles, Li+ was separated 155–1552 times more efficiently than Na+, K+, Mg2+ and Ca2+. Overall results demonstrate the potential of LIS/PAN NF as an adsorbent membrane filter for continuous Li+ mining from aqueous resources

Liquid-liquid extraction of lithium using lipophilic dibenzo-14-crown-4 ether carboxylic acid in hydrophobic room temperature ionic liquid

A green liquid-liquid extraction (LLE) system was developed for the recovery of lithium (Li+) from sodium and potassium ions, which are typically present at high concentrations in seawater. Dibenzo-14-crown-4ether (DB14C4) was functionalized with a long lipophilic alkyl C18 chain and a pendent proton ionizable carboxylic acid group to obtain a lithium (Li+) carrier system (DB14C4-C18-COOH) with high Li+ extraction performance and good stability in the room temperature ionic liquid diluent, CYPHOSIL 109. The Li+ extraction efficiency of DB14C4-C18-COOH/CYPHOSIL 109 can be enhanced by increasing the solution pH and DB14C4-C18-COOH concentration. Further examination of extraction results reveal 1:1 coordination between DB14C4-C18-COOH and Li+ which was also supported by density functional theory calculations. At room temperature, the developed LLE system effectively extracted dilute Li+ from Na+ (selectivity alpha(++)(Li)(/Na) = 1954) and K+ (alpha K-++(Li)/ = 138). Kinetic and thermodynamic parameters were evaluated for optimum Li+ extraction conditions. Sequestered Li+ can be easily recovered from the LLE system using dilute hydrochloric acid. Results from recycling tests showed stable Li+ extraction performance hence it can be used for long term application. Overall results indicate the potential application of DB14C4-C18-COOH/CYPHOSIL 109 as a treatment step to recover Li+ from brine or seawater. (C) 2016 Elsevier B.V. All rights reserved. A green liquid-liquid extraction (LLE) system was developed for the recovery of lithium (Li+) from sodium and potassium ions, which are typically present at high concentrations in seawater. Dibenzo-14-crown-4ether (DB14C4) was functionalized with a long lipophilic alkyl C18 chain and a pendent proton ionizable carboxylic acid group to obtain a lithium (Li+) carrier system (DB14C4-C18-COOH) with high Li+ extraction performance and good stability in the room temperature ionic liquid diluent, CYPHOSIL 109. The Li+ extraction efficiency of DB14C4-C18-COOH/CYPHOSIL 109 can be enhanced by increasing the solution pH and DB14C4-C18-COOH concentration. Further examination of extraction results reveal 1:1 coordination between DB14C4-C18-COOH and Li+ which was also supported by density functional theory calculations. At room temperature, the developed LLE system effectively extracted dilute Li+ from Na+ (selectivity alpha(++)(Li)(/Na) = 1954) and K+ (alpha K-++(Li)/ = 138). Kinetic and thermodynamic parameters were evaluated for optimum Li+ extraction conditions. Sequestered Li+ can be easily recovered from the LLE system using dilute hydrochloric acid. Results from recycling tests showed stable Li+ extraction performance hence it can be used for long term application. Overall results indicate the potential application of DB14C4-C18-COOH/CYPHOSIL 109 as a treatment step to recover Li+ from brine or seawater. (C) 2016 Elsevier B.V. All rights reserved.11Nsciescopu

Design of lithium selective crown ethers: Synthesis, extraction and theoretical binding studies

Lithium-selective (Li+) di-hydroxy crown ethers (CEs 3a-3h) were efficiently synthesized via intermolecular cyclization of bulky bis-epoxide with 1,2-dihydroxybenzene. Bis-epoxides were produced by etherifying allyl bromides with bulky diols to afford diene intermediates, which were subsequently epoxidized. Optimized cyclization reactions were established by changing the solvent, catalyst, and reaction temperature. Complexation abilities of CEs 3a-3h with Li+ and other alkali metals (Na+, K+, Cs+) were assessed by liquid-liquid extraction in dichloromethane-water system. Among the CEs, the highest Li+/Na+ selectivities were obtained from 3d (alpha(Li/Na) = 2519) and 3e (alpha(Li/Na) = 1768). DFT calculations reveal that 3d (1.28-1.37 angstrom) and 3e (1.23-1.38 angstrom) had the closest cavity sizes with Li+ diameter (1.36 angstrom). This result affirms that the size-match selectivity of CEs with Li+ was due to the presence of bulky tetramethyl (3d) or bicyclopentyl (3e) subunits with the rigid benzo groups. Complexation with larger cations like Na+, K+ and Cs+ greatly distorted the 3d and 3e rings as indicated by the larger O-M+ distances on their bulky sides than on their benzo sides. Thus, their (3d, 3e) superior selectivities were due to their Li+ preference and unstable complexation with larger M+. Enthalpy exchange reaction mechanisms reveal the tendency of all CEs to form 2:1 CE-M+ complexes with larger cations except for 3d, which mainly forms 1:1 CE-M+ hence it is considered most suitable for Li+. The efficient synthesis of di-hydroxy CEs widens their application not only as extractants but also as solid-supported Li+ adsorbents given the amenability of their OH- groups to further functionalization. (C) 2017 Elsevier B.V. All rights reserved.11Nsciescopu